SDA and Monitor 7 Newbie questions

bcs4

Wow, has this place changed! I probably haven't visited for for 6 or 7 years.

Amazing! I've been glancing over stuff here for the past couple of hours and I'm astonished by the fact that there are so many fans of the SDA still around! I thought I was probably one of the few left.

Ihope to tap into your wisdom with a couple of questions about tweeters first. I own a pair of SDA 1s serial number SDA 1832 and Monitor 7's number 7 58868 and 7 58859 and I'm wondering if I need the tweet upgrade.

The tweeters on the SDAs have a grey metal plate with "Polk Audio" in black writing and wires on the surface of the plate forming an upside down V and the 7s are black plastic with "Polk Audio" and "Silver Coil" written on them wires extending straight out to the side. Both have soft clear membrane domes.

I'm also wondering how reliable they are at the volumes I used to drive them at, say 100 DB. My old AR 3As and KLH 5s gave up the ghost years ago, granted the surrounds were brittle..

Any help would be greatly appreciated. I'd really like to feel like I can listen to them at the levels I want without doing a lot of damage to the speakers that have held a place in my heart for a long time. They are currently driven by a Sony ES receiver.

Thanks in advance,
Bill

ohskigod

I'm wondering if that reciever might be adequate for driving sda1's properly. I think getting some seperate amplification on them would be best. especially if your a fan of 100 db listening levels. receievers have a higher chance of clipping. at those levels, underpowering is FAR more dangerous than overpowering speakers.
I heard sony es series are good, but it still might have clipping issues at such high volumes. if your all about loud, it would be best if you were all about seperate amplification as well


sounds like your sda's have the sl1000 and the mon 7's have the sl2000. pics would help confirm that. the silk dome replacement for the sl2000 to me is worlds better than the sl2000. I have little to no experience with the sl1000, which from what I heard was a replacement for, but not as good as, the peerless tweeter.

If your in the mood to change tweets, I would at least give the silk domes replacemtents for the sl2000, but post pics so we can be sure of the tweeter ID for both sets.

Polk65

Welcome back Bill.

Do you need a tweeter change? This is subjective. Do your speakers sound harsh to you or do your ears hurt after listening for awhile at moderate volume?

If you find some Peerless tweeters, they will sound smoother and are a drop in replacement for your SDA 1's. Look for Peerless tweeters with a little hole in the center of the dome. This is an indication that it was used in a Polk Audio speaker. Some of the Peerless tweeters are 4ohms and not what you are looking for.

Polk Audio sells a new sl1000 replacement but it is not a direct drop in. The new tweeter is slightly larger and will require some cutting with a sharp utility knife or dremel tool. The screw holes also do not line up. You can unscrew one of your Monitor 7 tweeters and place it over the SDA tweeter holes to get an idea of how much cutting you will need to do. The new Polk Audio tweeter will fit in your Monitor 7's.

Here is what another member did with his SDA 2's. He upgraded both the tweeters and crossovers. http://www.polkaudio.com/forums/showthread.php?t=28024

Do your SDA's have fuses on the back of the cabinets? If so, you won't need to change a common crossover item called a polyswitch.

How is your wiring terminated? If it is bare wire, it has oxidated over the years. Trim some wire off the ends and either use a treatment like Caig ProGold or terminate them with your choice of spade lugs or banana plugs.

I'm not familiar with Sony ES receivers. If it has preamp out RCA jacks you can add an external amp for cleaner power and continue using the Sony. Seperates would be better but if you want a receiver, consider an HK or Denon.

Below are a few pictures of tweeters in my SDA CRS for size comparison.
(1) Polk Audio sl1000, (2) Peerless 810665, (3) Peerless 810665, (4) Peerless 810665, (5) Polk Audio sl2000

bcs4

Thanks for the info. I think I'll go ahead and update the tweeters on the SDAs but wait on the 7s since they're just surrounds right now.

I was wondering if anyone has ever lab tested the upgraded speakers before and after the change. This leads to a second thought I've had for a long time. I think it'd be great if some online or paper magazine would test some of the vintage speakers again to see how they compare to current products. I've gotta believe the SDAs would do well. I'd imagine the 7s would do relatively well too.

I've also wondered how the SDAs would do with all speakers driven to two channels without the enlarged sound stage feature. I think a great deal of the strength of these speakers was simply the fact that Polk was one of the first that used real technology and quality drivers (in quantity) in their speakers. Small woofers and tweeters in quantity make a ton of common sense because they move more air without being driven as hard. Others tried to use multiple speaks before, Rectillinear, the "Wall of Sound" (can't remember the manufacturer), and Bose 901s (the only significant contribution Bose ever made, IMHO). I've got to believe the SDAs would sound great even without the umbillical feature, and I wonder if it's actually needed or might conflict with the digital surround effects contained in todays surround receivers.

Thanks, again for your responses and this wonderful site,
Bill

Polk65

Bill, Just so it is crystal clear...

For your particular SDA's, you will probably have to enlarge the tweeter holes and their edges to mount the new replacement tweeters. Some have used an exacto knife, and it is quite time consuming. Others have ordered the tweeters and found this out afterwards only to curse in every known language.

Steve

schwarcw

Hi Bill!

Welcome back to Club Polk! As Polk65 said the tweeter chang is subject. I will tell you that I have replaced my SL1000's in my SDA-2's and I found this to be a great improvement to my ears. It was not as harsh, smoother and still had good detail. I didn't have too much problem mounting the replacements into the cabinents. They are not drop in as Polk65 has pointed out. I made a new gasket from cork, and the replacement tweeter sat on top of very nicely. I didn't use any gasket cement, you probably could if you wanted to. New holes were needed and I drilled them without a problem. The cabinents remained airtight when I tested them by gently pushing on the passive radiator while watching the mid range woofers push.

To your point about not using the SDA interconnect cable for HT applications and "conflicting" with the surround affect, I use my SDA's in the fronts with the interconnect cable. What I did to test it was to have someone behind the speaker, unplug, plug, unplug, plug . . etc. while I was listening to a soundtrack. I think the SDA enhanced the surround affect, no conflict at all. The front stage was noticably wider with the cable connected, and it stll allowed for the rear surround sound to come through without any problem. I recommend using the interconnect for HT and two channel music.

Good luck and welcome back!

bcs4

Thanks for the caution, but I used to make kitchen cabinets before I started building houses.

Now if I were going to work on the crossovers, that would be different as I've found pounding in the solder very difficult to say the least. I hope I never have to use that da*n 2 1/2 ounce hammer again! To this day I won't let my wife dust anywhere near the Dynaco amp that I built.

Bill

Polk65

Do you help friends out with hardwood floors?

bcs4

Schwarch,

I'm not sure your A B test gave you a true picture as I believe SDAs lose some of their drivers when the cable is removed. At least that's what happens with mine..

Thanks, and it's great to be here,
Bill

bcs4

Polk65,

Yes, but I don't solder that any more. I'd be happy to send you a picture of some that has been installed.

Good luck,
Bill

schwarcw

bcs4 wrote:

Schwarch,

I'm not sure your A B test gave you a true picture as I believe SDAs lose some of their drivers when the cable is removed. At least that's what happens with mine..

Thanks, and it's great to be here,
Bill

Exactly! Maybe my text was confusing, I recommend using the cable because all the drivers are in use and the soundstage is wider. If you've worked cabinents, the tweeter installation is pretty easy:)

I performed the crossover mods on mine without any difficulty. I followed the thread posted earlier http://www.polkaudio.com/forums/showthread.php?t=28024 and had no problem. The most difficult thing is you have to remover all the speakers, mark them, etc. It's a little time consuming. I never did anything like this before and had no problem. Take it one step at a time. Try the tweeters, and if you feel ambitious, go for the crossover mod after you've enjoyed the speakers for a while. Some folks have heard a big improvement, some others feel the improvement was marginal. I feel it was definitely an improvement. But, mabe my ears lost objectivity during the modification process:D

Carl

Larry Chanin

schwarcw wrote:

To your point about not using the SDA interconnect cable for HT applications and "conflicting" with the surround affect, I use my SDA's in the fronts with the interconnect cable. What I did to test it was to have someone behind the speaker, unplug, plug, unplug, plug . . etc. while I was listening to a soundtrack. I think the SDA enhanced the surround affect, no conflict at all. The front stage was noticably wider with the cable connected, and it stll allowed for the rear surround sound to come through without any problem. I recommend using the interconnect for HT and two channel music.

Hi Bill,

I use SDA-1Cs in a dedicated home theater setup with the interconnect cable. I agree with Carl's remarks above. As long as your mains are delivering a stereo image the dimensional drivers will be cancelling interaural crosstalk and therefore improving the front soundstage imaging. The surrounds won't have any effect whatsoever on the front soundstage, and I doubt the center channel would cause any conflict either.

Nevertheless, I think I'm like a lot of SDA enthusiasts here that occasionally wonder how the vintage SDAs would sound if they were fitted some of the highly rated modern drivers, such as the Ring Radiator Tweeter. I like the replacement silk tweeters, but I still can't help thinking that the ring radiators are superior. (No doubt its not a simple matter of altering the baffle recess to accommodate the modern tweeters. I'm guessing that the crossovers would probably have to be adjusted as well.)

I love my SDAs, but one of the things that they have going against them when used with the interconnect is that they shouldn't be toed in because that would adversely effect imaging. This puts them at a disadvantage with regard to high frequency response when being compared with conventional speakers that are toed in. Toeing in improves the high frequency response by making the speaker less off-axis relative to listeners sitting towards the middle of the room.

In contrast the SDAs are designed to be facing forward, as a result the listeners are more off axis and the high frequency response has to be adversely affected to some extent, when compared to a conventional arrangement. However, in a home theater arrangement, it you have a good center channel speaker it can somewhat compensate for this since the center is close to being on-axis for listeners sitting towards the middle of the room.

Larry

schwarcw

Larry Chanin wrote:

In contrast the SDAs are designed to be facing forward, as a result the listeners are more off axis and the high frequency response has to be adversely affected to some extent, when compared to a conventional arrangement. However, in a home theater arrangement, it you have a good center channel speaker it can somewhat compensate for this since the center is close to being on-axis for listeners sitting towards the middle of the room.

Larry

Another problem with the SDA's is that the front baffle has to be out in front of any entertainment center or your TV. In my case this put the speaker 14" out from the wall. At this distance the SDA bass response is affected. Too close to the back wall and it sounds to boomy, too far out, not enough bass. Ideal placement is probably 6" to 8" out from the front wall.

Carl

Larry Chanin

schwarcw wrote:

Another problem with the SDA's is that the front baffle has to be out in front of any entertainment center or your TV. In my case this put the speaker 14" out from the wall. At this distance the SDA bass response is affected. Too close to the back wall and it sounds to boomy, too far out, not enough bass. Ideal placement is probably 6" to 8" out from the front wall.

Carl

Hi Carl,

Whether this is a problem of course depends on the situation, and its not always a problem in comparison to conventional speakers, but sometimes an advantage.

In my case with a front projector screen and a false wall, its an advantage to be able to place the speakers close to the front wall. This permitted me to build the false wall much closer to the real wall. Conventional speakers could have required as much as four feet of space. I only needed about 16" or so.

Larry

bcs4

My thoughts are more along the line of duplication or the cancellation of parts of the sound field by using two technologies to recreate surround.

For instance, the SDAs create a virtual center area that is also created by Dolby surround in it's center speaker. If something is recorded in Dolby, the sound coming from the center channel is specified by the recording itself. If the Polk does it's job (as I believe it does) the SDAs will also create sound seemingly emulating from the center speaker position, something the Dolby did not intend. In doing so, some sound from the correct center channel will be enhanced and some will be cancelled (as intentionally done by the Polks to create the effect that makes them great stereo speakers). The apexes that are mistakenly duplicated will be louder, bases and apexes will somewhat cancel etc. Just a thought..

As was mentioned above, has anyone that you know of actually successfully modified their SDAs with other drivers that may be a little more current? I know I may blaspheme here, and I don't want to step on any toes (remember I love my Polks too) but it would seem possible to match certain characteristics (mainly sensitivity?) of the Polk tweeters and replace them with even smoother and flatter drivers. I've been reading here quite a bit, and I haven't seen any mention. Hope I haven't crossed an invisible line with the question. I'll just mind my own business now. Nothing to see here. Move along.

Thanks again everyone,
Bill

schwarcw

Good luck with your SDA's! Experiment with them and see what sounds best for you!

Welcome to Club Polk!

Carl

Larry Chanin

bcs4 wrote:

My thoughts are more along the line of duplication or the cancellation of parts of the sound field by using two technologies to recreate surround.

For instance, the SDAs create a virtual center area that is also created by Dolby surround in it's center speaker. If something is recorded in Dolby, the sound coming from the center channel is specified by the recording itself. If the Polk does it's job (as I believe it does) the SDAs will also create sound seemingly emulating from the center speaker position, something the Dolby did not intend. In doing so, some sound from the correct center channel will be enhanced and some will be cancelled (as intentionally done by the Polks to create the effect that makes them great stereo speakers). The apexes that are mistakenly duplicated will be louder, bases and apexes will somewhat cancel etc. Just a thought..

Hi Bill,

SDA dimensional drivers do not create duplication of center channel sounds in multi-channel soundtracks.

The dimensional drivers only operate when there is a different signal being produced in each main speaker. For example, in a pure two channel stereo setup, if the same monoaural sound was playing in both mains a phantom center sonic image would be produced, but the dimensional drivers would not be operating because there is no difference in signals. In this example this is identical to the way conventional speakers operate. The fact that conventional speakers also create phantom images demonstrates that the dimensional drivers are not the source of phantom centers. It is purely the conventional stereo drivers of an SDA pair that produces the phantom centers.

The dimensional drivers are driven by a stereo difference signal provided by the interconnect cable. This creates an inverted phase signal that cancels interaural crosstalk coming from the stereo drivers of the other main speaker and visa versa. The dimensional drivers only cancel crosstalk thereby improving imaging. They do not create phantom images.

Even if conventional speakers are used in a multi-channel system, the sound engineer has the option of creating both a true physical center channel signal and a main speaker phantom center by briefly placing the same monoaural signals in both mains as the center channel. If an engineer choses to do this the results would be identical with the SDAs. No doubt engineers routinely do this to some extent to stablize the soundstage as sounds are panned left to center to right and back. Whereas the volume of the right and left signals may not be as loud as the center channel, there will be a condition where each main speaker is playing the same mono signal as the center channel. This will happen when the sonic image is intended to be centered in the soundstage. It is up to the engineer to create a channel mix that is realistic without undue duplication of signals. If there is undue duplication in a soundtrack, both conventional and SDA speakers would be effected the same way.

Larry

bcs4

Thanks for responding Larry,

I'm not sure we'll agree on this, but that's fine. It's my impression, based on Matthew Polk's "White Paper" http://www.polkaudio.com/downloads/whitepapers/SDA_WhitePaper.pdf (as discussed throughout and illustrated in figure 3 on page 6) that the intent of the SDA is to create the impression of multiple speakers in the front 180 degrees in the case of earlier SDAs, and approaching the full 360 degrees in later versions, thus it would have to create duplicating or cancelling effects by accident when used with a processor and a discrete center and rear channels. Again, only in my opinion, this would seem to conflict with the engineer's intention for the discrete center or rear channels. That isn't to say that the SDA sound might still be preferred by some over non SDA sound.

Though you are correct in the event the right, center, and left channels are sent mono signal, I would think that the majority if not all of a quality Dolby 5.1 or higher recording, these channels would be discrete, if only marginally. If a majority of a movie soundtrack were indeed mono, it would defeat the purpose of discrete encoding. Even if a soundtrack were mostly mono, the surround generated by the SDAs would not be the same as the discrete during the times we enjoy surround the most.

That being said, it is entirely likely that I am incapable of understanding Dolby 5.1+ and SDA.

By the way, you mention the ring radiator tweeter. Can you recommend any more tweeters or characteristics to consider other than lower rolloff, flat response and efficiency that I could try in the SDA? Obviously there are other considerations in the choice of a tweeter, but I would hope there wasn't much filtering in the highs for the SDA 1s. If there were I would think they would have filtered out the 12-15K peak in the original tweeters. I know I can get the spec sheet for the original Peerless that the SL1000 was trying to duplicate, but I haven't seen any thing for the SL1000.

Thanks again,
Bill

Larry Chanin

bcs4 wrote:

Thanks for responding Larry,

I'm not sure we'll agree on this, but that's fine. It's my impression, based on Matthew Polk's "White Paper" http://www.polkaudio.com/downloads/whitepapers/SDA_WhitePaper.pdf (as discussed throughout and illustrated in figure 3 on page 6) that the intent of the SDA is to create the impression of multiple speakers in the front 180 degrees in the case of earlier SDAs, and approaching the full 360 degrees in later versions, thus it would have to create duplicating or cancelling effects by accident when used with a processor and a discrete center and rear channels.

Hi Bill,

The recent SDA technology paper is a simplified discussion used to introduce Polk's new Surround bar. It doesn't really discuss the details of the original implimentation. My remarks are based on Mr. Polk's white paper published in 1984 to describe the principals of his original SDA implimentaton.

I think your confusion lies in the belief that the dimensional drivers are in some manner reproducing the effect of multiple speakers and that they are in someway duplicating the original stereo signals, particularly the center channel. That is not what is happening. The wider front soundfield is a direct result of elimination of interaural crosstalk. As shown in the overview paper, (upper portion of figure 3) regardless of how wide the recorded sonic image was, conventional speakers which produce interaural crosstalk can only project imaging which is squeezed between the physical speakers. Once the crosstalk is eliminated the resulting soundfield can extend beyond the physical placement of the speakers to more accurately reproduce the original, widely spaced presentation. The dimensional drivers aren't creating duplicated signals, they are permitting the conventional stereo drivers to recreate a more accurate sonic image, closer to the live performance in which there is no interaural crosstalk.

bcs4 wrote:

Again, only in my opinion, this would seem to conflict with the engineer's intention for the discrete center or rear channels. That isn't to say that the SDA sound might still be preferred by some over non SDA sound.

You fail to recognize that it is not the dimensional drivers that are producing the phatom imaging, but rather the conventional drivers. Needless to say, conventional speakers have conventional drivers and if there were a problem with duplication of phantom imaging and discrete channels, the conventional speaker would be subjected to the same defect. All the dimensional driver do is improve imaging and widen the soundfield. They are not creating duplicated channels of the original signal.

bcs4 wrote:

Though you are correct in the event the right, center, and left channels are sent mono signal, I would think that the majority if not all of a quality Dolby 5.1 or higher recording, these channels would be discrete, if only marginally. If a majority of a movie soundtrack were indeed mono, it would defeat the purpose of discrete encoding. Even if a soundtrack were mostly mono, the surround generated by the SDAs would not be the same as the discrete during the times we enjoy surround the most.

My example with the extreme case of a stereo configuration playing mono was intended to illustrate the fact that the dimenional drivers only operate to produce interaural crosstalk cancellation, not phantom imaging. It is the conventional stereo drivers in the SDA that produce phantom imaging.

I agree, in the majority of a 5.1 soundtrack the signals playing in the front speaker array will be quite different. Therefore, your concern about duplicated center channel images (physical and phantom) should be allayed. My example was intended to show that in brief conditions during a soundtrack the engineer will deliberately duplicate the center imaging to, guess what, center the sonic image on the sound stage. This duplication is intended and normal, and of course it is not created by SDA dimensional drivers, it is created by conventional drivers in both SDAs and conventional speakers.

bcs4 wrote:

That being said, it is entirely likely that I am incapable of understanding Dolby 5.1+ and SDA.

At this juncture, if there is still a disagreement, perhaps it would be best to respectfully agree to disagree.

bcs4 wrote:

By the way, you mention the ring radiator tweeter. Can you recommend any more tweeters or characteristics to consider other than lower rolloff, flat response and efficiency that I could try in the SDA? Obviously there are other considerations in the choice of a tweeter, but I would hope there wasn't much filtering in the highs for the SDA 1s. If there were I would think they would have filtered out the 12-15K peak in the original tweeters. I know I can get the spec sheet for the original Peerless that the SL1000 was trying to duplicate, but I haven't seen any thing for the SL1000.

Thanks again,
Bill

While being a long-time SDA enthusiast, I don't claim having DIY speaker experience, nor am I recommending radical changes to your SDA's. (I was merely responding to your query comparing SDA's with modern speakers. There are pros and cons.) In fact, there's a disparaging terms used here to describe Polk speakers that have been radically altered, "FrankenPolks". :eek:

I believe that most folk here believe the peak in the original SL2000s was adequately handled by the silk dome replacements. However, when comparing vintage and modern speakers, I was suggesting that the ring tweeters are more advanced and are likely to have a better response than the silk replacements. As I mentioned, even if the modern tweeters could be physically installed in an SDA, other changes in the crossover would probably be needed for this to change to be viewed as an improvement.

Larry

bcs4

With respect, I agree. Thanks for spending so much time to respond though.

Bill