SDA crossover upgrades

Mr. Bubbles

Only for the sake of innocents reading this...

Not controversy, more like amusement. You are not the first person who thought he had more knowledge and insight into modifying Polk speakers than Matthew Polk and Polk's engineering department.

Dude, relax; don't be so arrogant. I respect all your opinions and realize that you are very knowledgeable about Polks, SDAs , and I would think about many other things. I can tell that you are very thorough in your research, upgrades and tests of your equipment before and after upgrades/ mods that you do. I have read many of your posts and gleaned a lot of information from them. One thing that jumps out to me is that I have not found a post where you came up with a new idea or concept on your own; it appears to have all come from someone else making a suggestion. I am not knocking you for that, it may very well be a much safer road to follow than the roads I take, but that is not the way that I am.

I in no way think I know more about these speakers than the guys that designed these speakers. But i also will bet just about anything that these guys know more now about speaker design than they did when they designed these speakers. That is obvious by the changes and improvements that they made to each successive model. They were learning, even back then.

If that were true, Polk would not have implemented an entire redesign from the SRS to the 1.2. Here is something else to consider: NOT ALL 1.2's CAN BE CONVERTED TO 1.2TL's![/u] I have attached the instructions from the 1.2 to 1.2TL conversion kit. Notice this warning from Matthew Polk:

"IMPORTANT: THE SRS 1.2TL Conversion kit can only be used with SRS 1.2 speakers whose serial numbers are 5001 or greater.

If conversion from one SRS model to another is as easy as you think it is, one has to wonder about the need for the warning. Why can only a specific run of 1.2's be converted to 1.2TL's? Isn't that odd? Aren't all 1.2's alike? What would happen if Matthew Polk's warning is cheerfully ignored and the owner of 1.2's with serial numbers 4999 and 5000 installed the 1.2TL upgrade kit? Would there only be a mild deterioration in sound quality or would amps and speakers blow up?

We obviously see design changes as different in each of our minds. I see a design change as the difference between the 1.2, 2.3, and 3.1. Not simply an updated version of the same model. you evidently do not see it that way and that is one aspect of why we are all different.

First I've heard of the serial number issue but my first question is why? i am sure you have had that question but evidently haven't found the answer. If that information is true (and I presume it is) then there is a difference that was not made known. Was it because there was a crossover point from the finality of using up old parts as they had in other models? That information would lead one to believe that there are at least 2 different 1.2 versions.

finally to your last point in that quote; can you read a schematic (not a literal question as i am sure you can), can you trace a circuit board to see if it matches that schematic? I am sure the sound may be different with the different drivers from the SRS to 1.2 but can you say it would be negative? Not unless you try it and listen to it first. But if you connect a crossover similar to the 1.2's with an interconnect like the SRS you will absolutely damage an amp. was this part of the warning/ I don't know but it could have been if there was a transitional model there.

I choose loudspeakers based on their sonic performance attributes. Any modifications I do would be toward improving and enhancing those performance attributes. With any loudspeaker design, there is a limit to the amount of modification you can do and still maintain the performance attributes that attracted you to the speaker in the first place.

I do the same and agree with this 100%. Where we differ is that I see that Polk did the same thing and made changes that I see to be not as drastic as you see them.

My modification goals are based on enhancing performance and getting as close as possible to the designer's ideal. If I wanted to stray from the original Polk design, I would just buy another speaker.

Again I agree completely. i am not trying to stray from Polk design but using ideas that they used later in development of these models. That is not to say that I will not try my own ideas later but I feel I should use the designers ideas first and then progress from there.

You are entitled to believe whatever you want, but the fact is, if you replace an automobile engine and suspension parts with corresponding tractor parts, the car will still get you from point A to point B, but comfort and safety will be compromised.

This was just meant to make a point and as H9 said it was silly. But it is correct and absolutely what we have in the market. everything from Kia's to Ferrari's to Cadillac's, and many others.

You are confusing redesign with updating. The SRS, 1.2 and 1.2TL use entirely different crossover designs intended to achieve different performance goals. An update substitutes better parts than those originally used, but the circuit design remains the same. I replaced most of the parts in my 1.2TL crossovers, even down to the printed circuit boards, with higher quality, better performing parts. However, I did not deviate from the original circuit design. I did not achieve a "different" sound. I achieved a huge enhancement to the sound.

Actually the definition of updating to to modernize or bring up to date. that would be to make changes to make the product a modern equivalent to it's original self. That is what Polk did as the models progressed. many of the mods that you and i have done do not match that definition, even if they may have been the things that Polk wanted to do but didn't. ie, a 10awg 16mH inductor is NOT and updated version of the original inductor, but a different inductor altogether and therefore by your definition, a design change. I would also tend to bet that the changes you made absolutely made a difference in the sound of your speakers and that this difference was indeed an improvement.

Where did you get this misinformation from?

The SRS uses 6503's in the stereo and dimensional circuits. The 1.2 and the 1.2TL use 6503's in the stereo circuit and 6511's in the dimensional circuit. Therefore, there is no rational basis for thinking that the SRS crossover "matches" both the 6503 and 6511 drivers. Also, the 6503 and 6511 have very different electrical and mechanical characteristics. For example, the DC resistance of the 6503 is 6.15 ohms compared to 2.7 ohms for the 6511. The maximum impedance of the 6503 is 39.78 ohms compared to 21.28 ohms for the 6511.

Please read the entire post. I explain this in technical detail. I also point out that I realize that these driver have different characteristics. that doesn't mean they can't use the same crossover components. using the 1.2 solely as an example,( you may want to inquire of an engineer to verify this since you may not understand my explanation) the crossover circuit for the stereo drivers uses the exact same values as the circuit for the dimensional drivers (except for the 16mH inductor to keep all frequencies below roughly 150hz in phase) when you adjust for the series connection between the 2 cabinets. Therefore Polk found it effective that both of these different drivers use the same crossover.

The only TL mods I recall being done by members of this forum were 1.2==>1.2TL mods, CRS+==>CRS+ TL and SDA 2B==>SDA 2B TL mods. These were all Polk recommended mods.

Again this looks like the safer road. The safe road is filled with complacency and definitely does not lead to progress. It only takes you where you know you are going but never offers suspense or new ideas.

The SRS and 1.2 cabinets are different with regard to bracing, panel construction and in the way the panels are joined together. They are completely different cabinets.

Ummm, ok. A cabinet drawer with mortise and tenon joints and a brace underneath does not make it completely different from cabinet drawer with square joints and screws holding it together. the same size and strength drawers serve the exact same function. They are different , but not completely.

Again, Polk's engineering department will be able to provide additional insight. I hope you consider them to be a credible source of information about SDA's.

I am sure they can be a great help. thank you for pointing them out. If one can indeed make some form of contact with the engineers I am sure it would be beneficial. That is not the case with most companies; with others you can only get "Peggy" on the phone. Think credit card commercial for those of you who don't catch that right away.

DK thanks for you response. As I mentioned earlier i enjoy this type discussion as it almost always makes e check myself and either re-think or think of new things. Again I respect your opinions as I can tell from your posts that you are very intelligent and thorough I am just not the kind of person to look to you as the Polk "god" as many on these forums appear to do. To me you are a very intelligent man that has previously started a similar path that I myself have only recently begun. being that we are different people, we are likely to approach that path in different ways.

Face

I did not see any arrogance, just a no nonsense reply.

Mr. Bubbles

Face wrote: »

I did not see any arrogance, just a no nonsense reply.

To me it seemed arrogant. I could have misinterpreted, I have surely done so before.

Joe08867

I think the arrogance is in the reader and i don't mean you I mean anyone reading can misinterpret something. I have read into posts such as this and felt the same way. I believe not hearing the person and only reading what they say can change a phrase drastically.

In either case, I do have a question for you.

Did you compensate in your redesign of the crossover for the disparity in the drivers needed for each design? I have a feeling the 6511 to 6503 differences are going to be quite apparent in your work if you did not. I am seeing a future of weak Dimensional sound.

You are adding a lot of Ohms to the SDA side using the crossover for the 1.2 or 1.2tl. While it may make the dimensional side easier to drive for the amp you are also attenuating the SDA effect. Not a trade off I would vote for in the larger SDA's. You almost have to add more resistance to the stereo side to compensate or rewire the Dimensional side to drop the ohms back down.

michael1947

I have a pair of sds srs 1a's and they sound just fine. Do we rebuild/replace the crossovers because they wear out or because we think Mathew and the boys at Polk Audio got it wrong. Just curious.

Mr. Bubbles

Joe, you are absolutely right. I have sent and received many messages that have been taken wrong. If i have done so in this case, I apologize, but the comment about the innocent seemed to be kind of a smart **** comment.

Did you compensate in your redesign of the crossover for the disparity in the drivers needed for each design? I have a feeling the 6511 to 6503 differences are going to be quite apparent in your work if you did not. I am seeing a future of weak Dimensional sound.

I have done no other compensation, at this point, than what Polk did when they made their upgrade (redesign as others see it) to the 1.2. I truly have a hard time believing so many intelligent members don't see that Polk used the same crossover on both of these drivers. Once again, if someone does the math on the dimensional series circuit between the two cabinets of the 1.2 the stereo drivers have exactly the same value components as the dimensional drivers. That is ALL I mentioned doing to the dimensional circuit; exactly what Polk did but with a different driver. Albeit a different driver that Polk saw fit to use the same crossover on. Will it sound different? I am sure it will. Will it be better than the SRS sounded originally? maybe, maybe not. If it doesn't, it is easy enough to remove 4 parts and put 4 others back in and switch the interconnect cable back to the original layout. It is a simple mod, and just as simple to go back to original if it doesn't make an improvement. Maybe it should be considered more like research than a mod. I am willing to bet that the SDA effect will be almost no different than the 1.2's in their original form, though I am sure the tonality will be somewhat different due to the different driver characteristics.

You are adding a lot of Ohms to the SDA side using the crossover for the 1.2 or 1.2tl. While it may make the dimensional side easier to drive for the amp you are also attenuating the SDA effect. Not a trade off I would vote for in the larger SDA's. You almost have to add more resistance to the stereo side to compensate or rewire the Dimensional side to drop the ohms back down.

Actually I will be keeping the same impedance that I have already. It will be different than the actual 1.2 since , as DK points out above, the impedance of the two different drivers is different.

As many of you think this could very well be a waste of time, but as mentioned before it is too easy not to try and if it doesn't work to put it back like it was.

Mr. Bubbles

Another point to note that the SRS, 1.2 and 1.2TL are similar is the parts list posted in the sticky. All the crossovers have the same part # with a different version designation at the end. If they were completely redesigned it would stand to reason that they would have entirely different model #'s instead of designations to indicate different versions of the same.

Joe08867

michael1947 wrote: »

I have a pair of sds srs 1a's and they sound just fine. Do we rebuild/replace the crossovers because they wear out or because we think Mathew and the boys at Polk Audio got it wrong. Just curious.

We usually redo crossovers to update/upgrade the parts from there 20+ year old crossovers as they do wear out over time, and honestly they make better parts for these now.

There are also those that mod them with ideas from Polk engineers as well. Like the 4.1TL mod for SDA2b's and the CRS+ so they can use the Tri-Laminate tweeter with these models.

What Oliver is doing is shooting for something I have not seen before on this forum. I applaud the effort but I think some key items are being overlooked.

Joe08867

oliverbubbles wrote: »

Actually I will be keeping the same impedance that I have already. It will be different than the actual 1.2 since , as DK points out above, the impedance of the two different drivers is different.

As many of you think this could very well be a waste of time, but as mentioned before it is too easy not to try and if it doesn't work to put it back like it was.

Actually you won't be keeping the same impedance. The issue you are not seeing is that the two crossover designs and drivers are different. So you will be gaining impedance with the new crossover design. Lets look at the speaker in both forms. I do not have the figures in front of me but for arguments sake lets say Original SRS's have a dimensional impedance of 8 ohms and 1.2TL's have an impedance of 4ohms. By not changing drivers with to compensate you will be doubling the ohm's rating that the 1.2TL crossover will see. Do you see what I mean? In a way you will be attenuating the circuit. In what way I am not sure but the ohm sweep is different for each as well as there response curves. These all have to be taken into account before changing the crossover.

heiney9

michael1947 wrote: »

I have a pair of sds srs 1a's and they sound just fine. Do we rebuild/replace the crossovers because they wear out or because we think Mathew and the boys at Polk Audio got it wrong. Just curious.

Caps, especially inexpensive eletrolytic caps, have a finite shelf life of anywhere from 10-15 years many time less. So we rebuild to replace old worn parts and while we are in there we change things up that have proved to be better in the span of when something was assembled like in the 80's until now. We replace inductors on the advice of "Matt and the Boys" because it's been roughly 20 years and components and technology change by either being something new and or cost is dramatically less now. We change resistors to something like Mills wire wound non-inductive because they sound better, etc.

H9

Mr. Bubbles

Joe08867 wrote: »

Actually you won't be keeping the same impedance. The issue you are not seeing is that the two crossover designs and drivers are different. So you will be gaining impedance with the new crossover design. Lets look at the speaker in both forms. I do not have the figures in front of me but for arguments sake lets say Original SRS's have a dimensional impedance of 8 ohms and 1.2TL's have an impedance of 4ohms. By not changing drivers with to compensate you will be doubling the ohm's rating that the 1.2TL crossover will see. Do you see what I mean? In a way you will be attenuating the circuit. In what way I am not sure but the ohm sweep is different for each as well as there response curves. These all have to be taken into account before changing the crossover.

I will be keeping the same impedance as i will be keeping the same drivers in the same wiring configuration. The crossover (effectively the 1.2 crossover) will see a different impedance than what it would normally see in the 1.2 since the driver impedance is different. What this will do is effect the response curve as the actual crossover frequency will be somewhat different. This can be easily compensated for with the inductor /capacitor values. the main concern I have is the differing output levels of the drivers due to impedance/ and efficiency. This too can be compensated for but does then get more in depth. But as I've said several times; if it doesn't work it can be changed back very easily.

Mr. Bubbles

The SRS uses 6503's in the stereo and dimensional circuits. The 1.2 and the 1.2TL use 6503's in the stereo circuit and 6511's in the dimensional circuit. Therefore, there is no rational basis for thinking that the SRS crossover "matches" both the 6503 and 6511 drivers. Also, the 6503 and 6511 have very different electrical and mechanical characteristics. For example, the DC resistance of the 6503 is 6.15 ohms compared to 2.7 ohms for the 6511. The maximum impedance of the 6503 is 39.78 ohms compared to 21.28 ohms for the 6511.

I am not sure what the nominal impedance is for either of these drivers. I would assume however that the 6503 is roughly double that of the 6511. this is somewhat (though not precisely) verified by the DCR specs given by DK. above. lets look at the dimensional circuits as a whole in both models.

The numbers i have here are simply numbers rounded from DK's specs above. they are IN NO WAY intended to represent the actual impedance of these drivers. say the SRS has 4 drivers of roughly 6 ohms each in a series/ parrallel configuration and the crossover is designed for this nominal 6 ohm total impedance and only sees these 4 drivers to get this impedance match.

now we look at the 1.2 drivers; say their are 4 of them in each cabinet, just as the SRS's each cabinet wired seies parallel with 3 ohm speakers. this gives us 3 ohms in each cabinet. but now this crossover not only sees these 4 drivers but also the 4 drivers in the other cabinet that these are in series with. This equates to 6 ohms total impedance, just as the SRS's. the only difference id that we now have all components in the dimensional circuit of both cabinets run in series with each other so not only do the driver electrically add together but so do the crossover components in this circuit.

Just like DK and others have built the same crossover for their speakers using different components, Polk did the same thing here between these 2 models. this describes the dimensional circuit only.

DarqueKnight

oliverbubbles wrote: »

Joe, you are absolutely right. I have sent and received many messages that have been taken wrong. If i have done so in this case, I apologize, but the comment about the innocent seemed to be kind of a smart **** comment.

oliverbubbles wrote: »

To me it seemed arrogant. I could have misinterpreted, I have surely done so before.

Perhaps it seemed arrogant to you because that is the world you live in. It is interesting that you accuse me of arrogance while your discourse is sprinkled with arrogant, passive-aggressive remarks. Even if I were the most arrogant jerk that ever lived, plus a serial killer, what difference would that make pertaining to the soundness of my ideas? Either my ideas make sense or they do not. I don't understand the relevance of any real or perceived character flaws to the soundness of my comments. I would not refuse a cure for cancer if it were invented by a serial killer.

I have continually and consistently pointed you toward the source of knowledge for modding SDA's:

DarqueKnight wrote: »

Why don't you submit an inquiry to Polk's engineering department about your modification plans? That is what I did prior to doing my first SDA modification in 1990. Polk engineers were very helpful in pointing out certain pitfalls to avoid. Electrical circuit modification is not just a simple matter of reading a schematic and substituting parts. Schematics don't, and can't, tell the whole story about the speaker designer's performance goals. If you submit an inquiry, it will have to be forwarded through Polk's customer service department (contact Kim Jasper). The engineering department no longer communicates directly with the public.

DarqueKnight wrote: »

What others have done in the past (and I'm speaking of legitimate modifications) have been done under the advisement of Polk's engineering department. Do what you want with your speakers, but if you are interested in performance improvement, it would seem prudent to seek advisement from the people who designed and built them.

DarqueKnight wrote: »

The SRS and 1.2 cabinets are different with regard to bracing, panel construction and in the way the panels are joined together. They are completely different cabinets. I understand that you find this difficult to believe. Again, Polk's engineering department will be able to provide additional insight. I hope you consider them to be a credible source of information about SDA's.

This was not arrogance. This was showing concern about you and others getting into an unfortunate situation with your speakers.

In contrast, these type of comments could be construed as insights into your character:

oliverbubbles wrote: »

...surely I am not the only one outside of Polk that has figured that out.

oliverbubbles wrote: »

I truly have a hard time believing so many intelligent members don't see that Polk used the same crossover on both of these drivers. drivers is different.

Why do you feel the need to passively-aggressively question the intelligence of forum members? While I applaud your ability to look at schematics that some of us have been using for over two decades and "see" things that we overlooked, I wonder why you can't just show us the error of our ways without calling our intelligence into question?

Along those lines, I have a question. I have attached a copy of the forward statement from the 1989 Polk Audio In Field Technical Manual. Warranty Manager Helen Yarbor states, in all caps (which is the written equivalent of screaming):

"IT IS IMPORTANT TO REALIZE THAT WE MANUFACTURE A VARIETY OF 6 1/2" DRIVERS WHICH ARE OPTIMIZED FOR SPECIFIC MODELS. THEREFORE IT IS HIGHLY RECOMMENDED THAT ONE READS THE QC STICKER ON THE BACK OF EACH DRIVER AND MATCH THE PART NUMBER TO ITS PARENT MODEL USING THE CROSS REFERENCE SUPPLIED IN THIS MANUAL."

Ms. Yarbor's comment appears to indicate that drivers are not as interchangeable among SDA models as you purport. Am I interpreting this correctly, or am I overlooking something?

oliverbubbles wrote: »

DK Again I respect your opinions as I can tell from your posts that you are very intelligent and thorough I am just not the kind of person to look to you as the Polk "god" as many on these forums appear to do.

That's kind of (passive-aggressively) over the top don't you think? I certainly don't consider myself to be a Polk "god" and it is insulting to the membership that you ascribe this to them. If I did consider myself a "Polk god", Would I have consistently referred you to Polk's engineering department? Since you are discussing model conversions, which is not a trivial undertaking, I suggested that you confer with Polk about that.

With regard to whether the change from the SRS to the 1.2 is a mere "upgrade" or a "redesign", I can only refer you to what Polk said. Their marketing literature said the 1.2 cabinet was a new "monocoque" design. They said the crossover was "redesigned" to enhance imaging and to present and easier load to an amplifier. Perhaps their use of the words "monocoque cabinet structure" and "crossover redesign" were just marketing hype. You probably won't have to go to Polk's engineering department for clarification on those points. Polk's customer service manager, Kim Jasper, should be able to provide such information.

As for me, since I own both the SRS and the 1.2TL, I can just look inside the cabinets and see that they are very different. This also applies to the crossover circuits. However, I don't doubt that you might look inside my speaker cabinets and not see much difference.

oliverbubbles wrote: »

Being the best they can be doesn't mean that I will end up with any of the SRS crossover designs in the end. i want them to be the best they can be, not necessarily the best Polk design they can be.

oliverbubbles wrote: »

As many of you think this could very well be a waste of time, but as mentioned before it is too easy not to try and if it doesn't work to put it back like it was.

Experimentation is not a waste of time, if it is appropriately conducted. However, as I and others have pointed out, you are overlooking many important design factors. You may not be able to "put it back like it was". In any event, enjoy your venture.

oliverbubbles wrote: »

One thing that jumps out to me is that I have not found a post where you came up with a new idea or concept on your own; it appears to have all come from someone else making a suggestion.

Really Oliver...why would this jump out to you? You talk like it's a bad thing that I take a conservative approach to modifying expensive vintage loudspeakers that would be close to impossible to replace if I screwed something up.

***Guess what?*** I am not in audio to come up with new ideas and concepts. In fact, I have stated many times that I do not enjoy the work involved in researching and implementing modifications. I am in audio for the enjoyment of music. It just so happens that my musical enjoyment can be greatly enhanced by carefully executed modifications. I get enough electronics "play time" at work. When I come home I just want to listen to music.

oliverbubbles wrote: »

I am not knocking you for that, it may very well be a much safer road to follow than the roads I take, but that is not the way that I am.

I realize that. However, you clearly stated that this thread was aimed at "guys on a budget", many of whom are inexperienced and unknowledgeable in this sort of thing:

oliverbubbles wrote: »

This post is not really for you "hardcore " guys out there with unlimited budgets but more for the guys on a budget considering crossover upgrades.

Therefore, the "innocents" I referred to were those who might be induced to error and catastrophic misfortune by the abundant misinformation and wild speculation in your posts. We have seen "innocents" start out with your mindset and end up with the following:

1. Passive radiators replaced with active woofers.
2. Tweeters replaced with "upgrade" horn tweeters.
3. "Enhanced" SDA circuitry that makes all music sound like it was recorded in a garage.
4. Drivers replaced with "upgrades" that were totally inappropriate and in some cases electrically unsafe.
5. Brutally butchered, and sometimes burned, crossovers.

Examples of the hack jobs in items 1-5 above periodically show up on eBay, after which we have a great time marveling at the *genius* of the mind behind such "performance enhancements".

As I said before, do what you want to do with your speakers. You asked for discussion and I provided my thoughts.

Joe08867

Oliver, DK is right on all his counts as far as the cabinets are concerned. Different building methods and bracing do change the sound characteristics of a speaker. Go over to a DIY speaker forum and look at what they have done. 1/2 in mdf won't hold a candle to 1/2 inch birch ply and triple bracing a cabinet compared to double bracing is almost night and day.

This comment.

Ummm, ok. A cabinet drawer with mortise and tenon joints and a brace underneath does not make it completely different from cabinet drawer with square joints and screws holding it together. the same size and strength drawers serve the exact same function. They are different , but not completely.

Makes you sound very silly, almost as bad as the car is a car comment. There are differences in the cab, the crossovers and the drivers. This isn't something we say just cause we want hear ourselves, its to help people not make mistakes.

I love the fact that you are trying something new but your method of thinking has me worried you will blow something up before long.

And your last post explains what I mean about impedance to a T. You in fact state it for me.

now we look at the 1.2 drivers; say their are 4 of them in each cabinet, just as the SRS's each cabinet wired seies parallel with 3 ohm speakers. this gives us 3 ohms in each cabinet. but now this crossover not only sees these 4 drivers but also the 4 drivers in the other cabinet that these are in series with. This equates to 6 ohms total impedance, just as the SRS's. the only difference id that we now have all components in the dimensional circuit of both cabinets run in series with each other so not only do the driver electrically add together but so do the crossover components in this circuit.

So instead of 6ohms total impedance you are going to have somewhere in the neighborhood of 12-14ohms. Do you see what I mean now? That is more than double the impedance so you will be attenuating the circuit.

Just letting you know, I have read your ideas and although commendable, I don't think you thought it through.

Face

I foresee another pair of Frankenpolks on the used market some day.

Mr. Bubbles

Perhaps it seemed arrogant to you because that is the world you live in. It is interesting that you accuse me of arrogance while your discourse is sprinkled with arrogant, passive-aggressive remarks. Even if I were the most arrogant jerk that ever lived, plus a serial killer, what difference would that make pertaining to the soundness of my ideas? Either my ideas make sense or they do not. I don't understand the relevance of any real or perceived character flaws to the soundness of my comments. I would not refuse a cure for cancer if it were invented by a serial killer.

really? that's not arrogance. maybe just compensation. Dude I'm not passive about anything. I can be pretty damn aggressive though. seems a little hypocritical there talking about the world i live in and all. you are correct your attitude, arrogance or not has nothing to do with what works and what doesn't. i tried to apologize for any misconception i may have had but you seem to want to point the me not being wrong in the first place. Either way, **** or not I still respect your opinions.

I have continually and consistently pointed you toward the source of knowledge for modding SDA's:

Yes you have and i remember thanking you for that. maybe you missed that part.

In contrast, these type of comments could be construed as insights into your character:

I'm an ****, never claimed any different. But these comments must have been misunderstood by you and since that is the cae possibly others. What i meant by them was that I am not the smartest person in the world and others, probably you included are smart enough to know this already so someone else out there has seen this besides me. i apologize to all who may have taken offense to this.

I wonder why you can't just show us the error of our ways without calling our intelligence into question?

I don't recall trying to show anybody the error of their ways, dude, I have enough problems of my own. i'm just trying to learn things here, and if you recall this all started by me simply posting my plans, not asking for opinions.

Along those lines, I have a question. I have attached a copy of the forward statement from the 1989 Polk Audio In Field Technical Manual. Warranty Manager Helen Yarbor states, in all caps (which is the written equivalent of screaming):

"IT IS IMPORTANT TO REALIZE THAT WE MANUFACTURE A VARIETY OF 6 1/2" DRIVERS WHICH ARE OPTIMIZED FOR SPECIFIC MODELS. THEREFORE IT IS HIGHLY RECOMMENDED THAT ONE READS THE QC STICKER ON THE BACK OF EACH DRIVER AND MATCH THE PART NUMBER TO ITS PARENT MODEL USING THE CROSS REFERENCE SUPPLIED IN THIS MANUAL."

This is all well and good but doesn't apply to what I have been saying (exactly). different drivers have different characteristics and will therefore sound different if placed in similar circuits. this does NOT mean that they will not be a close substitution or possibly a better substitution. And yes they could always sound worse. I have not shied away from this fact and have acknowledged it several times. Polk did this in my 2A's to use up old parts, and they sound better than any other speaker i have.

That's kind of (passive-aggressively) over the top don't you think? I certainly don't consider myself to be a Polk "god" and it is insulting to the membership that you ascribe this to them. If I did consider myself a "Polk god", Would I have consistently referred you to Polk's engineering department? Since you are discussing model conversions, which is not a trivial undertaking, I suggested that you confer with Polk about that.

Dude, read what i write; I never said you thought you were a "god", just that others act like you are. man take what you can get, if you're like most of us your wife never treats you that way. I am sorry if I am wrong, i am just assuming you are straight.

Really Oliver...why would this jump out to you? You talk like it's a bad thing that I take a conservative approach to modifying expensive vintage loudspeakers that would be close to impossible to replace if I screwed something up.

***Guess what?*** I am not in audio to come up with new ideas and concepts. In fact, I have stated many times that I do not enjoy the work involved in researching and implementing modifications. I am in audio for the enjoyment of music. It just so happens that my musical enjoyment can be greatly enhanced by carefully executed modifications. I get enough electronics "play time" at work. When I come home I just want to listen to music.

Once again, read what I wrote, and this time what you even copied and pasted from my post. I did. say being that way was a bad thing at all, it is just not the way i am. I am extremely competitive and if i do the same thing the next guy does i will only be playing at the same level. not that i am trying to win anything here, just explaining my nature.

I realize that. However, you clearly stated that this thread was aimed at "guys on a budget", many of whom are inexperienced and unknowledgeable in this sort of thing:

exactly! and this mod will cost me less than $20. if it doesn't work I can put it back to the way it was and only be out less than $20.

Therefore, the "innocents" I referred to were those who might be induced to error and catastrophic misfortune by the abundant misinformation and wild speculation in your posts. We have seen "innocents" start out with your mindset and end up with the following:

1. Passive radiators replaced with active woofers.
2. Tweeters replaced with "upgrade" horn tweeters.
3. "Enhanced" SDA circuitry that makes all music sound like it was recorded in a garage.
4. Drivers replaced with "upgrades" that were totally inappropriate and in some cases electrically unsafe.
5. Brutally butchered, and sometimes burned, crossovers.

Examples of the hack jobs in items 1-5 above periodically show up on eBay, after which we have a great time marveling at the *genius* of the mind behind such "performance enhancements".

Once again I tried to apologize for the arrogant comment if I took the innocent thing differently than you meant it. but now you seem to be calling into question my intelligence with the wild speculation and misinformation thing. again, sounds a little hypocritical to me. Those things don't appear to be anywhere closely related to my mindset, but I see your point. Again you compare my mindset to that and then make the *genius* comment. This seems to be calling my intelligence into question. Check yourself man, hypocrisy is not a trait that most people think of as good for ourselves. But hey, if you're good with it I am too.

Mr. Bubbles

. Different building methods and bracing do change the sound characteristics of a speaker. Go over to a DIY speaker forum and look at what they have done. 1/2 in mdf won't hold a candle to 1/2 inch birch ply and triple bracing a cabinet compared to double bracing is almost night and day.

I realize this completely, i worked in car audio for 22+ years and designed and built the loudest car in the world on the IASCA circuit, 2 years in a row. We were one of the first to break 176db when others were several db below this. AND this was done WITHOUT a factory sponsor on a budget of less than $25000 when the closest competitor was factory sponsored by more than one manufacturer and on a rough budget of about 1/4 million. We didn't get to replace our drivers or amps every run since we were not factory sponsored. The system was made to work and to last.

What does that have to do with any Polk speaker, NOTHING. but I let you know to tell you i know how cabinets work. I know the use of different materials, but that is not what happened here. Polk removed braces to open up the cabinet, if I had to guess why, it would have been to allow some of the standing waves inside the cabinet to help move the passive better. Did they make the cabinet thicker, or out of different material? not to my knowledge. they cut grooves in the cabinet boards so as to break up any sympathetic vibrations. DK's "monocoque" is simply describing an exoskeleton because they removed the internal bracing. I've built more cabinets than i care to think about (for home and automobile) out of everything from fiberglass to 1/2" steel plate. I've canceled resonances, damped drivers and cabinets and baffles, and then went back and added resonances back in where beneficial. There is NO rocket science to building speaker cabinets, and these are no different. In fact these cabinets are pretty poor. if they weren't using 6.5" active drivers they would never hold up.

So instead of 6ohms total impedance you are going to have somewhere in the neighborhood of 12-14ohms. Do you see what I mean now? That is more than double the impedance so you will be attenuating the circuit.

how do you get that. 4 3ohm drivers per cabinet wired series parallel as they are in these speakers will equal (3 ohms per cabinet in series with 3ohms from the other cabinet) 6ohms. the same as 4 6ohm drivers in a single cabinet.

Mr. Bubbles

Attached Images

* File Type: pdf Yarbor-FWD-1989FLDMAN.pdf‎ (82.8 KB, 3 views)

This letter also states that a suitable replacement will be recommended. indicating that some drivers are indeed interchangeable.

heiney9

Knock yourself out Oliver, I look forward to a new generation of better SDA's.

The mere fact that you feel the oldest SDA's you own, the SDA 2A's sound the best out of the 1C's and SRS's leaves me a little suspect because I have spent time with all those models and the 2A's, IMO, don't compete on any level with the newer SDA's. The 1C's, IMO, are about the best SDA's going as they are sort of the "sweet spot" for SDA's as in they fit in a majority of rooms without too much difficulty, they are fairly easy to drive comparatively, they aren't huge, they have a generous and forgiving sweetspot comparatively so one can listen off-axis and out of the sweet spot w/o too much listening penalty. They are fairly laid back in their presentation, most models have the ability to be used with the AI-1 interpahse cable, plus they look nice.

Again, just IMO, but there aren't too many here who would feel the 2A's trumph both the 1C's and SRS's all things being equal.

H9

Joe08867

oliverbubbles wrote: »

how do you get that. 4 3ohm drivers per cabinet wired series parallel as they are in these speakers will equal (3 ohms per cabinet in series with 3ohms from the other cabinet) 6ohms. the same as 4 6ohm drivers in a single cabinet.

Because they are double the impedance. How are you not seeing this? Double the impedance in each cab, now wire them as they should be in the 1.2tl crossover and you get???????? That's right 12+ ohm's. The crossover changes the wiring so that the impedance doubles across the two speakers. Combining 6+ ohms in each cabinet gets you 12+ ohms total across the circuit. I do not know how to explain it any better.

Mr. Bubbles

Joe08867 wrote: »

Because they are double the impedance. How are you not seeing this? Double the impedance in each cab, now wire them as they should be in the 1.2tl crossover and you get???????? That's right 12+ ohm's. The crossover changes the wiring so that the impedance doubles across the two speakers. Combining 6+ ohms in each cabinet gets you 12+ ohms total across the circuit. I do not know how to explain it any better.

I apologize Joe, I do see that and i now see where the confusion is coming in. I have been describing this in "effective" terms as compared to each other instead of actual terms as you are here. That is my fault and i am sorry to have confused you. i may have also confised you in my answer to your previous question. so let me rephrase my previous answer; yes I am making adjustments to compensate for this actual difference.

H9, I think a big reason i like the 2's so much better is their simplicity and to me it shows in the sound as being less colored to my ears.

heiney9

Actually I believe the single board 1C's are equally as simple w/the exception of the progressive point source tweeter array. But I certainly won't say you're not allowed to like the 2A's better. It's just more uncommon for those that have compared them to later models.

H9

Mr. Bubbles

I apologize Joe, I do see that and i now see where the confusion is coming in. I have been describing this in "effective" terms as compared to each other instead of actual terms as you are here. That is my fault and i am sorry to have confused you. i may have also confused you in my answer to your previous question. so let me rephrase my previous answer; yes I am making adjustments to compensate for this actual difference.

I would like to elaborate on this. I have the components to compensate for this impedance difference but plan on trying it first with the stock component values of the SRS and then the stock values of the 1.2 and then if necessary make any changes that are needed. I have not pre-adjusted anything. If an attenuation circuit is needed I will rewire all 4 dimensional drivers per cabinet in parallel (which will then be in series with the other cabinet wired the same way) and then place the attenuation circuit on the dimensional drivers so as not to have to attenuate the stereo drivers and the tweeters, but only one portion of the crossover circuit. This should give the same listening levels as I have now. As I mentioned before; the biggest concern I have is exactly what I think Joe is getting at; the difference in levels and the response curve of the dimensional circuits as compared to the other circuits in the system.

Face

How do you plan on attenuating a woofer circuit? Seems like a huge waste of power.

DarqueKnight

oliverbubbles wrote: »

I am sorry if I am wrong, i am just assuming you are straight.

You assume correctly...Mr. Bubbles.

oliverbubbles wrote: »

Dude I'm not passive about anything. I can be pretty damn aggressive though.

Me too.

oliverbubbles wrote: »

Yes you have and i remember thanking you for that. maybe you missed that part.

Yeah, I saw that...you're very welcome.

oliverbubbles wrote: »

I'm an ****, never claimed any different.

O.K.

oliverbubbles wrote: »

i apologize to all who may have taken offense to this.

No offense taken on my part. As I clearly stated, I was...and still am...amused. From the comments I have read from others, I don't think anyone else took offense either.

oliverbubbles wrote: »

DK's "monocoque" is simply describing an exoskeleton because they removed the internal bracing.

Why did you refer to the cabinet design as "DK's "monocoque"? The term "monocoque" was Polk's descriptive term, not mine.

oliverbubbles wrote: »

There is NO rocket science to building speaker cabinets, and these are no different. In fact these cabinets are pretty poor. if they weren't using 6.5" active drivers they would never hold up.

What do you mean by "if they weren't using 6.5" active drivers they would never hold up"? It appears that you are saying that Polk needed to use small drivers because the allegedly "poor" cabinets could not withstand the pounding from larger drivers. Using a larger number of smaller drivers can be more sonically advantageous than a single larger driver.

oliverbubbles wrote: »

This letter also states that a suitable replacement will be recommended. indicating that some drivers are indeed interchangeable.

Well, common sense should indicate that if Ms. Yarbor wanted her "suitable replacement" comment to include drivers, she would have said that. She had the "driver" comment in bold all-capital type and the "components" comment later in normal type. This letter was written sometime in 1988 for the 1989 Field Service Manual. I don't recall that there were issues with driver availability during the time this was written. There is nothing in the manual about substituting one driver with another. Sometimes there were issues with sourcing electronic components (polyswitches, capacitors, etc.) and connectors.

Long after SDA's were discontinued, there were supply problems with some drivers (the 6513 comes to mind). "Workable" substitutions were suggested, but it was plainly stated that such substitutions were not optimal.

oliverbubbles wrote: »

I am extremely competitive and if i do the same thing the next guy does i will only be playing at the same level.

oliverbubbles wrote: »

not that i am trying to win anything here, just explaining my nature.

oliverbubbles wrote: »

...i worked in car audio for 22+ years and designed and built the loudest car in the world on the IASCA circuit, 2 years in a row. We were one of the first to break 176db when others were several db below this. AND this was done WITHOUT a factory sponsor on a budget of less than $25000 when the closest competitor was factory sponsored by more than one manufacturer and on a rough budget of about 1/4 million. We didn't get to replace our drivers or amps every run since we were not factory sponsored. The system was made to work and to last.

What does that have to do with any Polk speaker, NOTHING. but I let you know to tell you i know how cabinets work. I know the use of different materials, but that is not what happened here. Polk removed braces to open up the cabinet, if I had to guess why, it would have been to allow some of the standing waves inside the cabinet to help move the passive better. Did they make the cabinet thicker, or out of different material? not to my knowledge. they cut grooves in the cabinet boards so as to break up any sympathetic vibrations. DK's "monocoque" is simply describing an exoskeleton because they removed the internal bracing. I've built more cabinets than i care to think about (for home and automobile) out of everything from fiberglass to 1/2" steel plate. I've canceled resonances, damped drivers and cabinets and baffles, and then went back and added resonances back in where beneficial.

(In my best Irish accent...) Surrrre, surrre...Mr. Bubbles...whatever you say.

Toolfan66

Hahahaha!!!

Mr. Bubbles

Mr. Bubbles

yeah i got that name for my bubbly fu@&!N personality. Fits pretty well doesn't it.

Why did you refer to the cabinet design as "DK's "monocoque"?

Just tryin to give the "god" some credit.

What do you mean by "if they weren't using 6.5" active drivers they would never hold up"? It appears that you are saying that Polk needed to use small drivers because the allegedly "poor" cabinets could not withstand the pounding from larger drivers. Using a larger number of smaller drivers can be more sonically advantageous than a single larger driver.

That is exactly what I meant. Smaller driver are definitely more advantageous for accuracy and sound quality. but they can not produce the pressures of large drivers. Sure the SRS's, 1.2's, and 1.2TL's have the cone area of an 18 but with very little excursion and even less motor strength. Don't get me wrong they sound awesome and the cabinets are adequate for the drivers installed in them but the build quality on the ones I have seen sucks.

Well, common sense should indicate that if Ms. Yarbor wanted her "suitable replacement" comment to include drivers, she would have said that. She had the "driver" comment in bold all-capital type and the "components" comment later in normal type. This letter was written sometime in 1988 for the 1989 Field Service Manual. I don't recall that there were issues with driver availability during the time this was written. There is nothing in the manual about substituting one driver with another. Sometimes there were issues with sourcing electronic components (polyswitches, capacitors, etc.) and connectors.

Long after SDA's were discontinued, there were supply problems with some drivers (the 6513 comes to mind). "Workable" substitutions were suggested, but it was plainly stated that such substitutions were not optimal.

You have some of that? You read it one way i read it another. same text. I'm sure you're right though.

laugh all you want with your Family cartoons, I have stated many times on these forums that I am the one trying to learn here, you are apparently the resident book of knowledge. My background is not in home audio and I am trying to gain what knowledge I can. I have made that plain so your cartoon doesn't seem to work here. But hey laugh all you want. If you ever come to South Carolina, look me up. Maybe we can have a beer and discuss things like real men.

I almost forgot, if you wish to respond to this again, fine. I am growing tired of the BS so I will let you have the last word as any "god" should be able to. I will not respond to you on this matter again.

heiney9

Again, Mr. Oliver Bubbles, I await your new and improved SDA's for the 22nd Century. Please right all the wrongs Polk did when offering these to the public. Please build a worthy cabinet.

H9

Mr. Bubbles

Man the guy i bought these from was right; there are some fu@$in idiots around this forum. There are also some decent people too. Joe and a few others appear to be some of the latter. The rest of you dumba$$es please treat me like you are treating Audio and ignore me.

Toolfan66

oliverbubbles wrote: »

Man the guy i bought these from was right; I am a fu@$in idiot on this audio forum . The rest of you please treat me like a dumba$$es and ignore me.

Fixed!!!