SDA crossover upgrades

Mr. Bubbles

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.

This upgrade was done on a pair of SDA SRS's. I am sure there are better components than what I used but i was on a tight budget and felt that most any decent quality components must be an improvement over 25 year old stock components.

I searched many sites and brands and settled on the Dayton 1% metalized poly caps for all caps directly in the signal path and standard Dayton metalized poly's for all shunt capacitors. The only exception was that for the 4.4 micro farad i used a 4micro farad 1% metalized poly paralleled with (2) 2.2 microfarad film and foil Daytons to get as close to the 4.4 as possible. I debated heavily over the resistors as price was somewhat closer on these but finally decided on the Daytons as well due to total overall cost with resistors included. however budget did allow enough that i doubled all resistors to a parallel pair for the correct resistance, ie, 15ohm resistor was created with two 30ohm's in parallel. I did this to increase the increase the wattage limits so as to keep heat in the resistors (and therefore distortion) down after periods of higher volume levels.

I first replaced the resistors in the right cabinet. I then listened to the speakers in both cabinets in stereo and mono. I could hear a very slight improvement in the right cabinet. I would like to repeat, VERY SLIGHT. Resistors by themselves; definitely worth the money, but maybe not the time and effort. I then replaced the caps in the right cabinet and listened again. MUCH more detail and clarity. bass extension seems more prominent. let me not confuse anyone however, I use the word more as a description of my impression but it was not really that there was more of anything that was/ wasn't there before but LESS of the characteristics that masked these things, Almost like a haze was removed. Even my wife could hear the difference. The balance seemed to now shift towards the right cabinet slightly. I then upgraded all the same components in the left cabinet. DEFINITELY worth the time and money with the parts I used. As mentioned before i know that there are better parts out there but I am unfamiliar with how much better they may have sounded with those parts. I plan on trying more esoteric components in my 2A's as well as components such as these in the 2A's as well for comparison purposes.

Now let me tell you what i did NOT do. I changed no inductors. I did not change the 92uf cap in the shunt circuit for the tweets, and i did not change the pair of 130uf caps in the dimensional circuit. I realize that the mid range/mid-bass sound will be greatly effected by the 130's and now that I have changed the shunt caps in the stereo and dimensional circuits I realize the shunt cap in the tweet section would make a significant difference too. the reason i did not change these is that i am going to experiment with changing this crossover to match that of the 1.2's. it is actually MUCH cheaper to convert this to a 1.2 crossover than it is to update all the large caps mentioned here. Note here that my cost is further reduced as i have a good many quality inductors form my car stereo years, and happen to have the 2 1.25mH that I need to make this change. For that reason i am going to be trying this in the near future (in fact i ordered all of the necessary additional components to do this when i ordered the parts for this upgrade). if I like it then I have a better system and saved money. if i don't like it i can then order the parts and upgrade those circuits as well. The designs between these 2 models is virtually the same with only a few minor changes and the dimensional circuits are almost identical in crossover values except for the high pass circuit used in the SRS and it's absence in the 1.2. i will update on this when i try it. Before then, I would like to get some listening time in with the current upgrade so I can be sure of what i hear between the 2 crossover designs.

For now i have noticed a nice improvement in sound and hope to continue to do so as these components break in.

For those of you on a budget and having the ability to do your own work, this is a worthwhile investment. I only spent $120 including the parts for the future experimentation/ upgrade. Thought the more esoteric components may sound better (I am not sure) you need not spend $400-$500 to perform this upgrade and get good results. so if money is tight don't worry that you can not afford those high priced parts. use a GOOD affordable part and you will have a worthwhile improvement without breaking the bank.

heiney9

Mills makes the exact values for the resistors you needed that are 12W and more than enough and @ only $4.25 those are awesome sounding resistors. You don't mention cost or type of resistor used? Mills are non-negotiable whenever I do upgrades beause they make quite a difference over stock or cheap resistors. If I was going to go all out I'd look at Dueland. Otherwise, nice write up and I'm sure an equally nice job, but we need photos or it didn't happen :razz:

An SRS is still not a 1.2 even if you could mess with the x-over.

H9

Joe08867

15ohm resistor was created with two 30ohm's in parallel. I did this to increase the increase the wattage limits so as to keep heat in the resistors (and therefore distortion) down after periods of higher volume levels.

I have seen a few people do this. It was more prevelant in car audio than home audio but i look forward to you findings.

Give those caps and such about 300hrs to break in before you make any real judgements. I do hope the Dayton's aren't as harsh as when I did them on my SDA2's. Cost me more in the long run as I redid the crossovers again with Sonicaps.

Mr. Bubbles

You don't mention cost or type of resistor used?

Sorry, I mentioned they are Daytons but am unsure if Dayton makes different ones. They came from parts Express and are the only Dayton resistors they had. They are 10W 2% values. If this is fairly accurate they are much tighter than the original 10%. Stock was 5W and now with my set up they are effectively 20W at each resistor location. this should keep heat way down. Cost was .98 each. This was part of my decision to use the multiples in parallel; even at 2 (a couple had 3) at each location total cost was still a good bit below using the Mills (as far as my budget was concerned).

but we need photos or it didn't happen

Will get some pictures and detailed parts list. I was just excited about it this morning and wanted to share with those that may have some of the same enthusiasm I do (unlike my wife).

An SRS is still not a 1.2 even if you could mess with the x-over.

Agreed.... somewhat. But neither is a 1.2 a 1.2TL, just as it was not produced that way from the factory. We have been through this before, and we will just have to agree that we both see this issue differently. As a note though, I am not looking for a label here so much as i am the best sound I can get from these speakers.

Give those caps and such about 300hrs to break in before you make any real judgements. I do hope the Dayton's aren't as harsh as when I did them on my SDA2's. Cost me more in the long run as I redid the crossovers again with Sonicaps.

They're not what I would describe as harsh currently but could be after break-in. Also I have no reference of comparison to the Sonicaps at this point. I realize i may desire to change these again later but I wanted to do something to help them out as I was fairly disappointed in them as compared to my 2A's. I am not sure i will ever prefer these to the 2A's as just like preamps, amps etc, the simpler more basic, circuits usually sound better to my ears. I am anxious to hear how these change with time/ break-in.

Joe08867

What are you driving these SRS's with? I ask just because you still seem to like your SDA2's more. I am a huge fan of SDA2's but driven correctly and in the right room SRS's, 1.2's or 1.2TL's are really hard to beat.

I agree with H9 on the SRS's will not be 1.2's but hope you enjoy the trip you are taking nonetheless.

heiney9

I have to say at some point give the Mills a listen, wire wound non-inductive do sound better than a typical .75c - $1.25 resistor. Again, not diminishing what you've done so far. I understand being on a budget and what not.

H9

Mr. Bubbles

What are you driving these SRS's with? I ask just because you still seem to like your SDA2's more. I am a huge fan of SDA2's but driven correctly and in the right room SRS's, 1.2's or 1.2TL's are really hard to beat.

I agree with H9 on the SRS's will not be 1.2's but hope you enjoy the trip you are taking nonetheless.

Currently using an Adcom setup with GFA555ll amplifier. Don't get me wrong, I am liking the SRS's much better as I have now done a lot to them, Re-sealed cabinets, re-wired internally with 12awg on all mid-woofer circuits, binding posts for interconnect, Dynamatted baskets, new gaskets, T-nuts, and epoxied magnets to baskets. Now the crossover upgrades. I am enjoying them, but if I had to choose one pair it would still be the 2's. I just think they have a less colored sound.

I agree that the SRS's will not be 1.2's no matter what you do to them. I am not looking to have a speaker with any particular badge, just the best sound i can get with what I have. A modded SRS is still a modded SRS even if it has a 1.2 crossover in it. If it didn't come from the factory that way it is still what the factory made it, just a modded version. But a 1.2 crossover is a 1.2 crossover even if it is inside a pair of Realistic cabinets.

DarqueKnight

oliverbubbles wrote: »

Now let me tell you what i did NOT do. I changed no inductors.

oliverbubbles wrote: »

Note here that my cost is further reduced as i have a good many quality inductors form my car stereo years, and happen to have the 2 1.25mH that I need to make this change.

When changing inductors, the inductance value as well as the DC resistance (DCR) value must be considered. With the exception of the large inductor in the SDA circuit, Polk does not recomment changing inductors. If you do change the smaller inductors, you must take care to choose inductors with the same DCR values as the originals. Polk does recommend a lower DCR inductor in the SDA circuit. See this thread for additional information:

Improvements-To-Modified-SDA-SRS-1.2TL-Crossover

oliverbubbles wrote: »

The designs between these 2 models is virtually the same with only a few minor changes and the dimensional circuits are almost identical in crossover values except for the high pass circuit used in the SRS and it's absence in the 1.2.

No. The SRS and 1.2 are entirely different designs.

oliverbubbles wrote: »

the reason i did not change these is that i am going to experiment with changing this crossover to match that of the 1.2's. it is actually MUCH cheaper to convert this to a 1.2 crossover than it is to update all the large caps mentioned here.

The 1.2 crossover was designed for the drivers and cabinet used in the 1.2. The SRS uses different drivers and a different cabinet. The cabinets have very different acoustic characteristics. All the parts of a speaker system (cabinet, crossover, drivers) are designed to work together. Simply replacing the SRS crossover with a 1.2 crossover is not recommended and could possibly damage the drivers. The only SDA models with interchangeable crossovers are the 1987 versions of the SDA 2B and SDA CRS+ and the 1989 versions of the SDA 2B and SDA CRS+.

oliverbubbles wrote: »

Agreed.... somewhat. But neither is a 1.2 a 1.2TL, just as it was not produced that way from the factory. We have been through this before, and we will just have to agree that we both see this issue differently.

An SRS can be significantly improved, but it cannot be converted to a 1.2 or 1.2TL. The original SRS is an entirely different speaker, even down to the cabinet design. See these threads for additional information:

Improvements-to-the-SDA-SRS

Further-Improvements-to-the-SDA-SRS-Custom-PCB-and-SDA-Inductor&p=1488234

A 1.2 can be converted to a 1.2TL. Polk used to sell a conversion kit.

Mr. Bubbles

wire wound non-inductive do sound better than a typical .75c - $1.25 resistor

The Daytons I got are labeled as non-inductive but I don't know much else about their makeup.

heiney9

oliverbubbles wrote: »

The Daytons I got are labeled as non-inductive but I don't know much else about their makeup.

In my listening experience the Daytons have a fairly noticeable upward slope at the higher frequencies and had a tad bit of grain compared to the Mills, which is smoother and more flat at the upper frequencies. Of course we all hear differently and listen for different things.

H9

Mr. Bubbles

DK thanks for the link.

No. The SRS and 1.2 are entirely different designs.

The 1.2 crossover was designed for the drivers and cabinet used in the 1.2. The SRS uses different drivers and a different cabinet. The cabinets have very different acoustic characteristics. All the parts of a speaker system (cabinet, crossover, drivers) are designed to work together. Simply replacing the SRS crossover with a 1.2 crossover is not recommended and could possibly damage the drivers. The only SDA models with interchangeable crossovers are the 1987 versions of the SDA 2B and SDA CRS+ and the 1989 versions of the SDA 2B and SDA CRS+.

yes they are different models but not entirely. Cabinet volume is the same even though the different drivers are used, but internally the cabinet is different with the bracing structure. The dimensional crossover is virtually identical with the exception of the high-pass circuit in the SRS and its absence in the 1.2. the dimensional circuit is switched from a direct positive signal connection (which is electrically inverted) in the SRS to the dimensional drivers being connected through each other (electrically inverted) in the 1.2. the other components have all the same values. Yes the caps and inductors re different values individually but a 1.25mh inductor in series with another 1.25mH inductor (as connected from one cabinet to the other) is equivalent to a 2.5mH inductor, and a 40uf cap in series with a 40uf cap is equivalent to a 20uf cap. So, even though the drivers are different and I am sure have somewhat different sound characteristics, Polk found that they should use the same effective crossover components, and therefore theoretically even the drivers would be interchangeable. This is easily converted from one style to the other with the correct parts. the tweeter circuits are also very, very similar. even in the TL version that simply has varied values to accommodate the different electrical properties of the tweets, making it very simple to adapt the 198's into even the SRS's if desired. I am sure this will stir some controversy But technically speaking all three of these models are very similar with only minor upgrades in each (electrically and mechanically speaking of course).

An SRS can be significantly improved, but it cannot be converted to a 1.2 or 1.2TL. The original SRS is an entirely different speaker, even down to the cabinet design. See these threads for additional information:

Again I'm not trying to make a 1.2 or TL out of my SRS's just trying to get the best sound from these speakers and i am not comfortable being limited to what others done in the past. many times i can not do any better but sometimes I can. However, these are NOT, Entirely different, but quite the contrary.

A 1.2 can be converted to a 1.2TL. Polk used to sell a conversion kit.

Still just a converted 1.2 using the logic outlined here, and not a real 1.2TL. However i somewhat disagree with this logic. I believe that if it looks like a car and rides like a car it is a car no matter if it is made from tractor parts.

Mr. Bubbles

In my listening experience the Daytons have a fairly noticeable upward slope at the higher frequencies and had a tad bit of grain compared to the Mills, which is smoother and more flat at the upper frequencies. Of course we all hear differently and listen for different things.

thanks for the description, that may help me in my listening tto these if i seem to notice some detail like that. i have no experience as of yet with the Mills, but maybe in the future.

nooshinjohn

oliverbubbles wrote: »

I believe that if it looks like a car and rides like a car it is a car no matter if it is made from tractor parts.

Enzo Ferrari would say that you described a Lamborghini perfectly!:cheesygrin:

Toolfan66

The 1.2 and 1.2tl cabinets are the same except a couple added braces along the back wall, the crossover boards are the same as well along with the drivers. the only difference is the tweeters and a couple different values in the xovers. converting a 1.2 to a 1.2tl is a 1.2tl speaker..

heiney9

Oliver, why would you use a x-over that is designed for different drivers than what is currently in your SDA's? I don't get that. You say you want them to be the best they can be, how do you know the changes you make based on the 1.2 x-over will work with the drivers in the SRS's? Don't you think using different drivers and a different x-over in the 1.2's were done for a reason. You'd be better off changing the caps you didn't change and leaving it stock. That will make SRS's the best they can be.

Again, just trying to have a discussion about what you're thinking, etc. Not being critical or negative.

Joe08867

You make a good point H9. I would be cautious about using a 1.2 or 1.2tl crossover on SRS's without also changing out the drivers that do not match.

I do applaud your efforts, though I wonder if it will not be what you are hoping for.

heiney9

oliverbubbles wrote: »

I believe that if it looks like a car and rides like a car it is a car no matter if it is made from tractor parts.

That's simply ridiculous, that means to you a Hyundai and Ferrari are the exact same thing. They aren't and that logic is just a little bit silly, IMO.

Mr. Bubbles

heiney9 wrote: »

Oliver, why would you use a x-over that is designed for different drivers than what is currently in your SDA's? I don't get that. You say you want them to be the best they can be, how do you know the changes you make based on the 1.2 x-over will work with the drivers in the SRS's? Don't you think using different drivers and a different x-over in the 1.2's were done for a reason. You'd be better off changing the caps you didn't change and leaving it stock. That will make SRS's the best they can be.

Again, just trying to have a discussion about what you're thinking, etc. Not being critical or negative.

It is only a different crossover in the sense that it is an updated version. by that logic why did Polk make the changes to the tweeter section of the crossover when they used the same tweeters as before? Because it was an improvement that they hadn't recognized earlier when the SRS's were developed. Since the tweeters in mine are the same as the 1.2's and the cabinet has nothing to do with the tweeter section other than the mounting locations which are the same as well, then why not improve the tweeter section as Polk evidently saw fit to do. That part has nothing to do with the dimensional driver that many of you keep pointing out are different. between the 2 models. So if i stop there then why should i not improve the tweeter section just as Polk did? Someone please explain that to me since it is the same principal when one goes from the 1.2 to the 1.2TL. it is just doing the same thing Polk did just not at the factory.

The next part would be the mid-woofer portion. The drivers here are the same. The crossover is updated slightly changing the 2.75mH coil to a 2.5mH coil. Very slight change of crossover, again to the same driver. So apparently this driver will work with either of these crossovers. At least according to Polk.

Now to the dimensional circuit. the drivers did indeed change here between the SRS and the 1.2. however the crossover component values are identical between these and the Mid-woofers when you take the wiring of the dimensional circuit into account. Both cabinets are wired together in the 1.2 from the negative terminals of he dimensional drivers which places the crossover components from each cabinet in series with the components from the other cabinet. Doing the math, the crossover components for the dimensional drivers are exactly the same as the mid-woofers except the large inductor which is the same in all 3 models.

Now, since we can use the 6503 in either circuit of the SRS or the 1.2 and the 6511 uses the same circuit as the 6503 in the 1.2 then the 6503 can then use the same circuit as the 6511 (which it already does in the 1.2). So the crossover matches both drivers, even though they may have slightly different characteristics, surely I am not the only one outside of Polk that has figured that out.

Since Polk saw fit to improve/ update the crossover in both the tweeter section as well as the mid-woofer/ dimensional sections, why would I not want to start where they did in a quest for improved sound. It sounds like many of you have done the same by modding to the TL version.

Is the dimensional effect the same in later models, is it better, is it worse? I don't know as I don't have all versions to compare. DK may be able to answer this as I think he has both the SRS and the 1.2TL from posts I've read here.
from an electrical standpoint I doubt there is much if any difference in the dimensional effect. i would assume a slight difference in the bass response but can not be sure how significant.

The 1.2 and 1.2tl cabinets are the same except a couple added braces along the back wall, the crossover boards are the same as well along with the drivers. the only difference is the tweeters and a couple different values in the xovers. converting a 1.2 to a 1.2tl is a 1.2tl speaker..

This makes the cabinets as well as the crossovers different. But again the SL2000 is used with either the SRS and or the 1.2 tweeter section crossovers so these two crossovers are interchangeable with the drivers, we just assume there were improvements made to the sound due to the upgrades in the 1.2. The difference between the cabinets of the SRS and the 1.2 is the bracing just as you describe here. That makes it the same as the 1.2TL except for the bracing.

You say you want them to be the best they can be, how do you know the changes you make based on the 1.2 x-over will work with the drivers in the SRS's?

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. I do not know which sounds better, see above. I will always be able to change them back if I don't like it, but as far as working with the drivers, see above again.

as H9 mentioned, I am only having a discussion here and hope not to offend anyone. Discussions such as this challenge my thought process and help me to learn more in the long run.

heiney9

But the tweeters were the same, they didn't change (until the TL's) even though the circuit did a little bit. The drivers in the SRS aren't the same as the drivers in the 1.2's, that was my point. I'm not saying it won't work, I'm just wondering if you've considered that and what you expect to be "better" about it?

So then if the x-over components in the 1.2 are identical for the SDA circuit, then it must be the drivers that make the improvement. You don't have those drivers so what kind of improvement do you expect?

H9

Mr. Bubbles

heiney9 wrote: »

That's simply ridiculous, that means to you a Hyundai and Ferrari are the exact same thing. They aren't and that logic is just a little bit silly, IMO.

from a transportation standpoint they are the same, in fact6 the Hyundai may be better since it can hold more passengers. Yes the ferrari is a better car and my comment was silly but is all in how we look at things and I think that I am looking at this situation as Apples to Apples (just maybe a golden delicious vs a granny smith vs a Rome, when many of you look at these models as apples, oranges and lemons.

Mr. Bubbles

heiney9 wrote: »

But the tweeters were the same, they didn't change (until the TL's) even though the circuit did a little bit. The drivers in the SRS aren't the same as the drivers in the 1.2's, that was my point. I'm not saying it won't work, I'm just wondering if you've considered that and what you expect to be "better" about it?

H9

I have considered the fact that the drivers are different and will have a different sound than the 1.2's. better or worse i don't know until I try. But it is pretty plain that either driver will work with either crossover (well to me it is anyway), just as my 2A's have different drivers than called for even though they appear in every way to have been that way from the factory.

audiocr381ve

oliverbubbles wrote: »

I have considered the fact that the drivers are different and will have a different sound than the 1.2's. better or worse i don't know until I try. But it is pretty plain that either driver will work with either crossover (well to me it is anyway), just as my 2A's have different drivers than called for even though they appear in every way to have been that way from the factory.

Keep up the great work, I'm interested in hearing about what you think of the final result.

Mr. Bubbles

One pint I failed to touch on earlier is the high pass filter (130uf caps) in the SRS dimensional circuit. This appears to me to be there solely to make the dimensional effect work with the amplifier since in those models (without the filter) the positive signal lead of one channel would be connected directly to the negative of the other channel. this obviously would damage the amp and not work at all. For this reason the high pass filter is necessary simply for function only and not to affect the sound. This is why it would not be necessary in the later models as the positive signal lead is not used directly in the dimensional circuit, but is fed through each channels crossover components and drivers. that is why I would expect little to no difference in the effect and sound.

heiney9

I am interested in your findings too, just playing a bit of devils advocate at times. Good luck

H9

audiocr381ve

heiney9 wrote: »

I am interested in your findings too, just playing a bit of devils advocate at times. Good luck

H9

No this is great stuff guys. I love hearing the back and forth on this type of thing. Hopefully it leads to new discoveries!

DarqueKnight

oliverbubbles wrote: »

But technically speaking all three of these models are very similar with only minor upgrades in each (electrically and mechanically speaking of course).

oliverbubbles wrote: »

This is easily converted from one style to the other with the correct parts.

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?

oliverbubbles wrote: »

I am sure this will stir some controversy

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.

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.

oliverbubbles wrote: »

Again I'm not trying to make a 1.2 or TL out of my SRS's just trying to get the best sound from these speakers and i am not comfortable being limited to what others done in the past.

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.

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.

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.

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. This is similar in concept to the fact that there is a limited amount of cosmetic surgery one can undergo and still look like a human being.

oliverbubbles wrote: »

I believe that if it looks like a car and rides like a car it is a car no matter if it is made from tractor parts.

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.

However, I understand your premise: You think that if you put different (or what you consider "improved") circuitry in an SRS cabinet and keep the same drivers and tweeters, you will still have an SRS, just an improved version. No, you will not have an improved SRS. You will have a pair of "Frankenpolks". There are design rules and which must be respected during the course of a modification.

oliverbubbles wrote: »

It is only a different crossover in the sense that it is an updated version.

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.

oliverbubbles wrote: »

by that logic why did Polk make the changes to the tweeter section of the crossover when they used the same tweeters as before? Because it was an improvement that they hadn't recognized earlier when the SRS's were developed.

No.

Your question does not make sense when you consider that 17 models of SDA's used the SL2000 tweeter. Tweeters have to be sonically blended with drivers. Reusing the same tweeters with different driver and cabinet combinations usually requires some adjustment to the crossover circuit.

oliverbubbles wrote: »

Since the tweeters in mine are the same as the 1.2's and the cabinet has nothing to do with the tweeter section other than the mounting locations which are the same as well, then why not improve the tweeter section as Polk evidently saw fit to do.

Tweeters have to blend in with the drivers and passive radiator and the drivers and passive radiator have to be acoustically complimentary with the cabinet. Loudspeakers should be modified with due regard to the totality of their design in order to maintain coherency of sound.

oliverbubbles wrote: »

Now, since we can use the 6503 in either circuit of the SRS or the 1.2 and the 6511 uses the same circuit as the 6503 in the 1.2 then the 6503 can then use the same circuit as the 6511 (which it already does in the 1.2). So the crossover matches both drivers, even though they may have slightly different characteristics, surely I am not the only one outside of Polk that has figured that out.

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.

oliverbubbles wrote: »

Since Polk saw fit to improve/ update the crossover in both the tweeter section as well as the mid-woofer/ dimensional sections, why would I not want to start where they did in a quest for improved sound. It sounds like many of you have done the same by modding to the TL version.

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.

oliverbubbles wrote: »

Is the dimensional effect the same in later models, is it better, is it worse? I don't know as I don't have all versions to compare. DK may be able to answer this as I think he has both the SRS and the 1.2TL from posts I've read here. from an electrical standpoint I doubt there is much if any difference in the dimensional effect. i would assume a slight difference in the bass response but can not be sure how significant.

I addressed this in post #29 of my "Improvements to the SDA SRS" thread:

DarqueKnight wrote: »

Modified SRS compared to the modified SRS 1.2TL

The midrange reproduction between the two speakers was close, with the SRS 1.2TL providing a little more detail, presence, and image solidity. Whereas the soundstage of the SRS is fully three-dimensional, the soundstage of the 1.2TL was more holographic. The SRS 1.2TL gives more of a sense of space between the individual instruments in the soundstage. The SRS 1.2TL was far better in reproducing upper treble and lower bass frequencies.

With the SRS 1.2TL, tenor and alto saxophone notes have a more "reedy" and "airy" quality. Rim shots on the drum kit have more impact and transient attack. The high-hat has more metallic shimmer and overtones. The bass notes are stronger, more articulate and more defined. In summary, the SRS 1.2TL presents a more "real" aural illusion.

oliverbubbles wrote: »

The difference between the cabinets of the SRS and the 1.2 is the bracing just as you describe here. That makes it the same as the 1.2TL except for the bracing.

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.

inspiredsports

DarqueKnight wrote: »

. . . the only SDA models with interchangeable crossovers are the 1987 versions of the SDA 2B and SDA CRS+ and the 1989 versions of the SDA 2B and SDA CRS+ . . .

Qualifying as "almost" the same, 1986 SDA 1B's and SDA SRS II's had identical drivers and identical crossover boards (cabinet size and passive radiators were different). The only difference in the crossovers was the first resistor after the black wire on the binding post; 1 ohm on the 1B and 3.5 ohm on the SRS II.

Toolfan66

Thanks for that info DK!!! That answers a lot as the 1.2's the tweeters are wired out of phase and that's why they sent you a new wiring harness for the tl upgrade. The only other odd thing is the passives on the tl version has weights on them and the 1.2's do not, the SRS passives are or look a lot different from the back side then the 1.2/1.2tl's.

Not sure why they would send the extra bracing and not a weight for the passives. I added three extra braces in my cabinets. The only reason I kept the 1.2 cabs over the 1.2tl cabs is the 1.2's were in much better shape..

DarqueKnight

TOOLFORLIFEFAN wrote: »

Thanks for that info DK!!! That answers a lot as the 1.2's the tweeters are wired out of phase and that's why they sent you a new wiring harness for the tl upgrade. The only other odd thing is the passives on the tl version has weights on them and the 1.2's do not, the SRS passives are or look a lot different from the back side then the 1.2/1.2tl's.

Not sure why they would send the extra bracing and not a weight for the passives. I added three extra braces in my cabinets. The only reason I kept the 1.2 cabs over the 1.2tl cabs is the 1.2's were in much better shape..

My 1.2TL's were born as 1.2TL's. The 1.2TL instructions are not from a conversion kit I purchased, they are just part of the information I've collected over the years.

As seen in the picture below, my 1.2TL passives are weighted. The passive radiator for the SRS, 1.2 and 1.2TL all have the model number SW150, but as you noted, all three look different. Maybe lighter weight materials were used in later model SW150's used in the 1.2TL's and this required the use of the weight. I expect that all three models of SW150 had the same mechanical properties. Therefore, a 1.2 owner would not need a weight.

Toolfan66

I still own all the parts for my 1.2's and of course I am running all my parts from my 1.2tl's both passives look identical except for the weight. We have a nice digital scale at work I should weigh them and see if there is a difference..

Toolfan66

I wonder if they sold many conversion kits.