Has anyone tried this before - SDA CRS+10?

heiney9

TennMan wrote: »

The room you have them in probably makes a difference in whether or not they sound boomy or bloated.

No. I sold a lot of 10's back in the day, owned pairs, had friends that owned pairs, heard customers systems, heard them currently and compared to the 5's and 7's in the same setting they are as I described to my ears. Still great performers, but the 5's and 7's are purer and have better midrange performance. Side by side drivers playing the same frequency is sort of a design no-no.

H9

TennMan

heiney9 wrote: »

Dude, we are just discussing it with you. Did you really think you'd throw this out there and everyone would be like "cool, do it". It's a discussion and I don't think anyone has said anything nasty or attacking anyone personally, etc.....it's a discussion forum and you will get all kinds of discussion about anything you choose to lay out for discussion.

It's all good, do it and report back. Don't be one of those who starts this whole idea and then we never hear anything back about it :biggrin:

H9

Oh, I didn't think anyone was being nasty and I take no offense to anyone's comments. I knew everyone would not jump on the band wagon. I just didn't want to offend anyone with an off the wall idea like this that might appear as me being dis-satisfied with my CRS+ speakers. I'm very satisfied with them as is. I was just looking at the cabinets, drivers and schematics, and decided to ask if it had been done before.

I'm going to look into how feasible it is to do without damaging anything. If that is possible, I'll probably try it. I will certainly report back here the results... good or bad.

halo71

heiney9 wrote: »

Side by side drivers playing the same frequency is sort of a design no-no.

H9

I guess nobody read my last post. lol

heiney9

halo71 wrote: »

I guess nobody read my last post. lol

I read it, just reiterating and completing my thoughts in my post. The thing is, it is subtle. It's not like the 10's suck. But if you spend time with the 5,7,10 you will notice the 5 and 7 have a midrange openess and clarity the 10's can't quite muster. On some really congested music or compressed pop and rock you wouldn't even notice because the recording doesn't allow you to hear it.

Probably aren;t going to hear it on Nirvana's Smells Like Teen Spirit, but probably would notice it on something from Norah Jones, etc.

H9

TennMan

I may not be fully understanding what I should about how the driver offset of the drivers will effect the outcome. Sometimes things take a while to soak in.

I realize the 10 and CRS have different spacing between the drivers. But, the SDA-2 and CRSs use the same tweeters, crossovers and drivers in the '87 versions so they are the same parts in different cabinets, excluding the PR of course.

As you can see in the photos below, a monitor 10 on the left and a SDA-2 on the right, the drivers are located with the same spacing. I looks like they could have used the same template to cut all the holes. With that in mind, how would the driver offset be a factor in the sound when putting SDA drivers in a monitor 10 cabinet? I know there are a lot of other factors to consider but right now I'm wanting get a good understanding of the driver spacing.

Again, I don't mean to sound argumentative. Keep in mind that I'm a newbie at this stuff and I'm just gathering information I need to know before starting on this. Thanks for all the input so far.

heiney9

The spacing between the regular driver and dimensional driver is critical, it's a big part of what allows the SDA properties.

Do a little reading here to understand SDA and how it works. Scroll to pp 89 and read the margin explanations. You'll see why the M10 cabinet and driver placement isn't ideal for SDA. Not only are the drivers too close, the phase alignment from the mids and tweeters will not be correct, as certain frequencies will be arriving earlier and later than others, diminishing, if not completely constricting any SDA properties.

http://www.polksda.com/srsreview.shtml

Joe08867

I thought the crossover in the CRS+ and the 2b were identical? I also don't think the spacing will have that much of an effect if any at all on the sound.

Like Tennman said above the 2b's are spaced much closer than the CRS+ with the same crossover.

I also thought that the SDA crossovers let lower frequencies across both drivers and the effect was centered on the midrange split from right to left? I could be wrong but I don't think I am.

TennMan

heiney9 wrote: »

The spacing between the regular driver and dimensional driver is critical, it's a big part of what allows the SDA properties.

Do a little reading here to understand SDA and how it works. Scroll to pp 89 and read the margin explanations. You'll see why the M10 cabinet and driver placement isn't ideal for SDA. Not only are the drivers too close, the phase alignment from the mids and tweeters will not be correct, as certain frequencies will be arriving earlier and later than others, diminishing, if not completely constricting any SDA properties.

http://www.polksda.com/srsreview.shtml

I admit I have no understanding of the workings of the SRS speakers. Thanks for posting the link for me.

I don't see how the explanation of SDA that was given in the article about SRS speakers, which have the tweeters mounted between the MWs, relates to what I proposed doing with the CRS and monitor 10 speakers. All I can offer about the spacing was covered in my last post with the photos. I hoping others will weigh in and give their opinion about spacing/offset of the drivers and the effect it will have on SDA in the 10B cabinets.

audiocr381ve

Joe08867 wrote: »

I thought the crossover in the CRS+ and the 2b were identical? I also don't think the spacing will have that much of an effect if any at all on the sound.

Like Tennman said above the 2b's are spaced much closer than the CRS+ with the same crossover.

I also thought that the SDA crossovers let lower frequencies across both drivers and the effect was centered on the midrange split from right to left? I could be wrong but I don't think I am.

He wants to do the mods on Monitor 10B's.

heiney9

Did you read the sidebar explanations? Especially the last one? Those aren't just for the SRS's they are common to all SDA's and one of the principles of SDA implementation.

The last one is the clincher and I explained what would be going on in my post, but you still don't understand?

Here it is again;

the phase alignment from the mids and tweeters will not be correct, as certain frequencies will be arriving earlier and later than others, diminishing, if not completely constricting any SDA properties.

On the 10's the acoustic centers of the drivers (all drivers) are pretty much flush, on sda's the mid/bass drivers are set back so they create a 20* angle (not physically, but the radiating pattern) towards the listener so the the slower mid/bass signals arrive at the same time as the faster tweeter signals. The M10 drivers aren't set up that way. They will cause phase alignment errors which will most likely be large enough to kill the acoustical SDA properties.

H9

P.s. I'm not telling you this so you don't do it, I'm telling you this beause you said you didn't have an understanding how SDA's worked.

heiney9

It's time to get the screwdriver out and get to swapping. No more thinking, just do it and see how it turns out.

H9

OldmanSRS

Try it. Be careful and note how to restore it if needed and let us now how they sound.

No harm done.

halo71

:cheesygrin:

Toolfan66

If spacing is so critical then why is the spacing all over the board with SDA's. All the same parts are in the CRS+'s and the 2B's except the passive but yet spacing is not the same and the cabinet size is way off from one another..

I would bet money that putting those parts in the 10's will sound as stellar as they do in the original cabinets the only difference will be no toe in.

heiney9

Has anyone here read the original white paper on SDA?

H9

Mr. Bubbles

the phase alignment from the mids and tweeters will not be correct, as certain frequencies will be arriving earlier and later than others, diminishing, if not completely constricting any SDA properties.

On the 10's the acoustic centers of the drivers (all drivers) are pretty much flush, on sda's the mid/bass drivers are set back so they create a 20* angle (not physically, but the radiating pattern) towards the listener so the the slower mid/bass signals arrive at the same time as the faster tweeter signals. The M10 drivers aren't set up that way. They will cause phase alignment errors which will most likely be large enough to kill the acoustical SDA properties.

No disrespect H9 but all this is only good from the speakers respective sweet spot. Given the 20 degree information, one should calculate that radiating angle in to determine the exact spacing between the speakers in relation to the distance back from their physical plane the listening location will be.

This could be done with any cabinet unless the tweets are time aligned and this too works perfectly with exact measurements considering the driver locations and the amount of delay built into the specific crossover. No matter the brand or model of the speaker.

Notice that even in the side bar pictures they show the mid/ bass sound originating from the front of the voice coil. This is the case with any speaker and why many high end speakers set the tweeters back on the baffle in relation to the mid/ bass drivers ( the RTA 12 is a perfect example of this). That being said even the 10B cabinets will offer some amount of axis offset due to the mid/ bass voice coils being set further back in the cabinet than that of the tweeters though not he same 20 degrees as the SRS's but very close to that of the 2'b's. I hate to say it but at least a portion of that article was designed around marketing hype over the SRS's and not true physics.

The idea that the OP has will never sound like a SRS but could possible be a close hybrid to the 2A's/ b's. Then again it could suck real bad. Until he does it no one will ever know. I would bet the SDA effect will end up at least almost as good as the 2A's/ B's. I would be more concerned with the dispersion pattern of the sideways tweet and the overall response curve. The sweet spot could be calculated from the measured effective axis angle and the distance between the speaker plane and the listening position along with the distance between cabinets.

TennMan

Although I think installing the CRS parts in the 10B cabinets might work and perhaps sound really good, I'm having second thoughts about actually doing it right now. None of the comments I got here caused that. I think maybe common sense has finally started to set in.

This afternoon I found Larry's writeup , SDA's 1C's vs CRS+'s'. What he wrote reminded me of the first time I heard SDA, (which was not many days ago), and how amazed I was that these small CRS+ speakers could sound so good.

Then tonight as I sat in the dark listening to Pink Floyd - Money for the first time since I got the CRSs, I realized how much I like these little speakers just the way they are. While I sat there listening to Pink Floyd all the good things that Larry and others had to say about the CRSs kept going thru my mind. His writeup made me realize that now is not the time to start taking my, new to me, CRS+ speakers apart in search of something that sounds better. I could screw something up in the process and as they say... "you never know what you've got until it's gone".

Thanks Larry for that great writeup!

I appreciate all the comments that I received about this crazy idea. I will keep them all in mind and if the urge strikes me again to try making a set of CRS+10s I will know where to start.

Joe08867

audiocr381ve wrote: »

He wants to do the mods on Monitor 10B's.

I know that. I am not dumb I was explaining the relation of the mids between CRS and SDA2's, The SDA2's and the Monitor 10's have nearly if not identical spacing. Reading is easy, understanding is much harder, huh?

Just kidding.


H9, I have read the white paper, I have it on my computer now. Honestly I think this might work pretty well.. Will it be perfect? Probably not. Will it sound as good as CRS's or SDA2's? I don't know. I have a feeling it will be close. But we may need to find someone that lives close to really know for sure.

GO FOR IT.

kelly osborne

Guys, this is my first time posting, n not sure if I'm posting in the right spot but here goes, I bought new a pair of SDA CRS 7750 SPEAKERS back in 85-86- . After getting a divorce my wife kept these speakers n stereo system. I thought I would never get them back. My son had them in his room n when he got older he moved in with me . Needless to say I got my system back. It's been a while since I messed with any stereo stuff, can someone tell me what I've got n I need a tweeter for the left one n the joining cable is gone. Can I still get this stuff or am I up a tree here. I remember these speakers being the best I've ever heard. Help.

Toolfan66

kelly osborne wrote: »

Guys, this is my first time posting, n not sure if I'm posting in the right spot but here goes, I bought new a pair of SDA CRS 7750 SPEAKERS back in 85-86- . After getting a divorce my wife kept these speakers n stereo system. I thought I would never get them back. My son had them in his room n when he got older he moved in with me . Needless to say I got my system back. It's been a while since I messed with any stereo stuff, can someone tell me what I've got n I need a tweeter for the left one n the joining cable is gone. Can I still get this stuff or am I up a tree here. I remember these speakers being the best I've ever heard. Help.

You can get replacement tweeters from Polk also I beleive you have the blade/blade cable and I have one for sale if you would like it.. Let me know.

If you call Polk about the tweeters let them know you are a member and you will get a discount..

nspindel

TennMan wrote: »

Although I think installing the CRS parts in the 10B cabinets might work and perhaps sound really good, I'm having second thoughts about actually doing it right now. None of the comments I got here caused that. I think maybe common sense has finally started to set in.

This afternoon I found Larry's writeup , SDA's 1C's vs CRS+'s'. What he wrote reminded me of the first time I heard SDA, (which was not many days ago), and how amazed I was that these small CRS+ speakers could sound so good.

Then tonight as I sat in the dark listening to Pink Floyd - Money for the first time since I got the CRSs, I realized how much I like these little speakers just the way they are. While I sat there listening to Pink Floyd all the good things that Larry and others had to say about the CRSs kept going thru my mind. His writeup made me realize that now is not the time to start taking my, new to me, CRS+ speakers apart in search of something that sounds better. I could screw something up in the process and as they say... "you never know what you've got until it's gone".

Thanks Larry for that great writeup!

I appreciate all the comments that I received about this crazy idea. I will keep them all in mind and if the urge strikes me again to try making a set of CRS+10s I will know where to start.

As people have indicated, there's nothing wrong with the experiment you've described, since you're not doing anything that can't be easily reversed. But as you're realizing, you've got a damn fine pair of speakers there, and I highly doubt your experiment would yield something that sounds better.

My advice would be to continue to familiarize yourself with this forum and the tweaks that many of us have discovered and applied. There is a lot of hard work that has been done by a lot of the members here, all very well documented in these forums for you to follow and apply yourself. A lot of these tweaks are quite inexpensive, things like dynamat on the driver baskets and replacing the stock seals with armacell. If you want to invest some money into these speakers, crossover rebuilds will give you unbelievable improvements. That's where you should be focusing your attention, in my opinion. Good luck and enjoy your CRS+'s!

TennMan

Well guys, after sleeping on it last night I changed my mind again. I'm now the owner of a set of CRS+10Bs. Possibly the first set of them in existence. I know what every one says, "if there are no photos it didn't happen", so I posted a couple of photos below.

I can lay to rest all the talk about different driver spacing between the CRS and the 10s killing the SDA. It didn't. In my room the SDA effect is as good today as it was yesterday before doing the CRS+10B swap. I will say that I may not have the best room for SDA according the reviews of others about how there SDAs sound. I don't get sounds from the rear and only rarely from 90* to the sides. I covered what SDA effects I hear in another thread if anyone whats to read about it.

The bass of the 10Bs, that I missed in the CRS+, is back in the CRS+10Bs. Some like the bass of the 10s, some say it's bloated. To each his own. I happen to like it. This configuration seems to give a little more punch to the music over the stock CRS+.

I'm not going to get into a debate about whether or not the CRS+10Bs sound better than the CRS+. I like my CRS+ speakers and I like the CRS+10Bs really well so far. I'm probably bias due to this swap being my idea. I have only listened for a couple of hours so far but at this point I have no regrets on the CRS+10B swap. I want to wait for someone else to do the swap and then report their results and they can recommend for or against doing the swap.

I intend to do a lot more listening tonight. I like to listen in the dark when everything is quiet. I think I'm going to like what I hear.

The swap can be done without doing any modification to either speaker with the exception of drilling one hole in the brace behind the drivers in the 10s cabinet to mount the crossover. If you don't care to drill a hole in the back of the cabinet that would be a better choice. Since I didn't know the outcome of this project I didn't want to drill a hole in the back.

A 1/4" hole in the braces is needed for the screw. I didn't have a 90* angle drill so I had to drill the hole in the brace by hand, using a drill bit with a hex on the end and a 1/4" drive socket and ratchet. Not all that hard. Just takes some time. The hole is drilled in the center of the brace up 3-3/4" from the bottom surface. I had to scrape off some hot glue from the brace to allow the crossover to mount flush against the brace.

I did discover that the CRS+10Bs didn't like the tilted stands that I made for my 10Bs. The speakers sitting straight up works the best.

If anyone has questions feel free to ask. If anyone does the swap I recommend throwing on ZZTop - Cheap Sun Glasses first thing. You will know right away if you made the right decision.

polk_stand_1.jpg

heiney9

The bass is a function of the MW drivers and x-over and cabinet volume. The only thing the same is the cabinet volume so who knows if the bass is the same as it was in the original 10's, it could be better or worse or different.....etc.

Glad you are enjoying them

H9

TennMan

heiney9 wrote: »

The bass is a function of the MW drivers and x-over and cabinet volume. The only thing the same is the cabinet volume so who knows if the bass is the same as it was in the original 10's, it could be better or worse or different.....etc.

Glad you are enjoying them

H9

The passive radiators are the same. Actually the PRs don't even need to be removed to do this swap. You are probably correct in your assessment that the bass may not be the same as the 10s. It could actually be better or worse or different.....etc. Maybe someone else will do this soon and give us their opinion of how they think this CRS+10B combination sounds.

inspiredsports

Your idea spurred my curiousity and I've just spent some time looking over the schematics of the CRS line, Monitor 10 line and SDA 2B's.

I'll bet the CRS crossovers and drivers will sound good in the Monitor 10 cabinets.

Plus, as mentioned above, it will be easy enough to undo if you aren't satisfied with the sound quality.

heiney9

TennMan wrote: »

The passive radiators are the same. Actually the PRs don't even need to be removed to do this swap. You are probably correct in your assessment that the bass may not be the same as the 10s. It could actually be better or worse or different.....etc. Maybe someone else will do this soon and give us their opinion of how they think this CRS+10B combination sounds.

I know the PR's are the same that's why I didn't mention them at all. Since the MW drivers are different and have different parameters and the x-over is completely different those two things will have a big impact on the bass output of the 10B cabinet. That was my point, not saying one is better than the other but I would expect there to be some differences in the bass output now vs. the regular 10B. The PR is tuned to the cabinet and the frequency and performance of the drivers. The drivers and the x-over are different ergo, there should be a difference in bass vs. the regular 10B

Mr. Bubbles

I am not sure where OP is located. Maybe Tennessee? If any other Polkies are close maybe another set of educated ears could listen as well for a second opinion and another perspective.

My assumption would be as the OP describes. It is my understanding that Polk used only one Passive in the 10's no matter the driver configuration. However they did use at least 2 different driver configurations in that model. This indicates that the passive/ cabinet tuning is the same (or at least very similar) for the different drivers. One could then assume that the drivers from the CRS+'s would work at least similarly with the passive/ cabinet combo, since at one point both models used the same drivers. I would assume a very similar bass response to the original 10 sound but with the addition of the SDA effect which should be somewhat similar to that of the 2A/B's. Is this what I am understanding the sound to be like or are you familiar with the 2's.

TennMan, I guess what I'm asking is how does the bass compare/ contrast the bass of the original 10's before the swap? And how is the SDA effect compared/ contrasted to the CRS+'s before the swap (or to SDA 2A/B's if you have experience with those models).

evhudsons

very interesting, and great props for not destroying anything at all. I love the idea of plug and play swap experiments.

I do know that proper alignment is crucial to good sda. Even if unconnected they sound great, but when you get used to the sda you will know when it is not right. Last night I noticed something out of whack. Upon inspection, my cleaner had slightly moved one by about two inches farther back. I got out my tape measure to make it exact, and used a L shaped measuring device to square them up. It was then very noticeably back to normal sda, which is profound once you know the difference.

Even if the sda line has different spacing, I'm sure they did their measurements and formulas to make sure the sda worked. I would not assume that because they are different spacing distance doesn't matter from model to model.

TennMan

All I can say about the PRs is that the monitor 10B speaker and the CRS+ had different part numbers for the PRs so I stayed with the ones that were in the monitor 10 cabinets. One PR was a SW100 and the other was a SW102. They both look the same.

TennMan, I guess what I'm asking is how does the bass compare/ contrast the bass of the original 10's before the swap? And how is the SDA effect compared/ contrasted to the CRS+'s before the swap (or to SDA 2A/B's if you have experience with those models).

I haven't had a chance to listened to this combination very much so far today but my initial feelings about the bass is that it is more or less the same as the with the 10B drivers. I will know more after I spend some time with them later tonight. I'm not a good person to make any firm comments about SDA effects or comparisons. My CRS+ and now this CRS+10B hybrid are all SDA speakers I have ever heard. From my short amount of listening today I feel he SDA effect of the hybrid is just as good as it was with the stock CRS+. After I listen more extensively latter on tonight I might feel differently.

I really don't want to say too much one way or the other right now. I don't want my comments to influence anyone else who does the CRS+10B swap that really knows their stuff when it comes to SDAs. I would much rather hear their impression of the hybrids. The ramblings of a SDA newbie like me doesn't carry much weight. Are you listening OldmanSRS? It would be great if someone with 2Bs could do this swap and compare them to the 2Bs. I don't expect them to come up to that standard but it would be an interesting to see how they compare. I wouldn't be surprised if someone else doing this swap said they were dogs. What do I know?

inspiredsports

TennMan wrote: »

. . . it would be great if someone with 2Bs could do this swap and compare them to the 2Bs . . .

If you look at the progression of the various lines of Polk speakers at that point in time, there was somewhat of a convergence going on with crossover component values and drivers.

CRS's compared to 2B's had some similarities, as did 2B's and Monitor 10's. I'm guessing your end result will be very "2B-like".

It would be interesting to see a measured response curve when you're done. If it's a bit off it may be possible to "voice" the cabinets by tweaking the value of the initial (2.7ohm?) resistor on the plus (red) binding post. More likely, it may not need any tweaking at all.