Advanced tweaking of Polk SDA's...

jakelm

daifanshi,

Why dont you run a Fr sweep in you room and post the graph here so we can understand what the problem might be?

I'm still (after reading 3 pages) trying to figure out what your trying to accomplish. All of this over a spike @ ~13khz?


....I so confused......

I'll go back and re-read again.:o

heiney9

jakelm wrote: »

daifanshi,

Why dont you run a Fr sweep in you room and post the graph here so we can understand what the problem might be?

I'm still (after reading 3 pages) trying to figure out what your trying to accomplish. All of this over a spike @ ~13khz?


....I so confused......

I'll go back and re-read again.:o

He's been asked what he's trying to achieve and he seems to be avoiding the question. And the spike in question is in a tweeter he doesn't own :rolleyes:. Strange indeed!

H9

jakelm

heiney9 wrote: »

He's been asked what he's trying to achieve and he seems to be avoiding the question. And the spike in question is in a tweeter he doesn't own :rolleyes:. Strange indeed!

H9

All, I can gather is an active crossover, which in my opinion, is a bad idea. Now if he wants to bypass the crossover network and go strickly active, thats one thing, but combining the 2 will surely be a problem.

The price of a good active xover, to me, would be about the same as just buying the RD tweets, and finish with the whole thing.

But the speakers he has now do not have the sl2000's, so whats the problem?


..ah well... dont mind me...please continue.

DarqueKnight

daifanshi wrote: »

I recently bought a pair of 2.3TL's locally from craigslist for a very reasonable price.

I have a background in DIY speakers and I think the design allows for some interesting experimentation.

Hmmmmm...most new SDA owners post about the glorious 3D sound stage. Seems like these were purchased not for listening, but for dissecting and experimenting.

daifanshi wrote: »

Before we decide to bypass the in-speaker crossover completely, we can apply it to some known problems with certain Polk designs. The often maligned 12kHz resonance of the SL2000 tweeter can be easily tamed with an active filter before the main amplifier input without a complex in-speaker crossover redesign.

Lots of the guys around here kept one, or a few, or all of their SL2000's when they upgraded to the silk dome replacement. Someone might let you borrow one of theirs if you are not going to do destructive testing.

How would you characterize the sound of your 2.3TL's compared to the sound of other speakers you currently own or have recently owned?

daifanshi

heiney9 wrote: »

Are you purposely ignoring my question? I'm just curious to know if have read and understood the SDA "white paper"? I'm betting you didn't and don't care too. Which is fine except if you are trying any kind of meaningful experiment it would be best to understand the fundamentals. By the questions and discussions you've had so far it sounds like your shooting in the dark.

H9

I don't understand how this marketing paper is relevant. I've read it very carefully and there is nothing in there that I can find that says the SDA speaker system can't be realized with active crossovers replacing the passive ones.

Can you point to me where it says SDA and active crossovers are bad? Maybe I missed that part. For completeness give me a page number and paragraph.

For those who might still not understand what I'm planning to do. I am going to recreate the passive crossovers of the SDA 2.3TL and change it into active multi-amp system. I am not playing around with the locations of the dimensional and stereo arrays or the tweeters responses. In the meantime I will add a provision for adjusting the phase alignment between the tweeter and midranges.

I will also add an adjustable variable delay to the dimensional drive signals to augment the physical time delay provided by the spacing between the dimensional and stereo arrays.

This differs drastically from Carver Sonic Holography or Stereo Expanders because of the dimensional drivers.

Polk has already has the provision for a semi-active system with the biamp terminals. I am just taking it to the next logical step.

For those who are interested in active crossovers, you can google "active vs. passive crossovers" and something should appear.

There's been so much noise since the first post, that I'm afraid a lot of this may have been lost.

jakelm

Ben,

Didnt you do almost exactly what Dai is trying?

daifanshi

DarqueKnight wrote: »

Hmmmmm...most new SDA owners post about the glorious 3D sound stage. Seems like these were purchased not for listening, but for dissecting and experimenting.




Lots of the guys around here kept one, or a few, or all of their SL2000's when they upgraded to the silk dome replacement. Someone might let you borrow one of theirs if you are not going to do destructive testing.

How would you characterize the sound of your 2.3TL's compared to the sound of other speakers you currently own or have recently owned?

As you can probably guess, most of my speakers are active. The main system consists of completely active dipoles like the Linkwitz Phoenix. Except mine have rear tweeters and different drivers. In my garage I have some minimalist EPI 100's for goofing.

What drew me initially to active crossovers was the transient abilities. Modern recordings with huge dynamic range swings sounded wonderfully realistic. And the amplifier requirements were much less than a typical passive.

The Polk 2.3TL are a very dynamic system . It is a testament to the designers' persistence and skill. The sheer number of drivers helps too. The decrease in distortion from multiple drivers is very apparent. The one thing I feel is a weakness is the upper midrange where I can hear some "fuzziness". It can be cleaned up somewhat when I drive the speakers with my old tube amps. But even with my 1-ohm stable 200W solid state amps, it's more noticeable. The bass is very clean and goes very low in room. In my particular room, it is sensitive to placement distance from the back wall and can cause boominess at certain frequencies when I'm not careful placing them. I can try the "bass brace" technique in the future, but my speakers did not come with them.

The imaging is dependent on source material of course. But something like old Pink Floyd can image very well with the SDA effect.

It is one of the best passive systems in terms of balance and how "big" the sound can get. The vintage Thiel CS's and Dunlavy SC's that I've heard are in the same class.

heiney9

daifanshi wrote: »

I don't understand how this marketing paper is relevant. I've read it very carefully and there is nothing in there that I can find that says the SDA speaker system can't be realized with active crossovers replacing the passive ones.

Can you point to me where it says SDA and active crossovers are bad? Maybe I missed that part. For completeness give me a page number and paragraph.

For those who might still don't understand what I'm planning to do. I am going to recreate the passive crossovers of the SDA 2.3TL and change it into active multi-amp system. I am not playing around with the locations of the dimensional and stereo arrays or the tweeters responses. In the meantime I will add a provision for adjusting the phase alignment between the tweeter and midranges.

I will also add an adjustable variable delay to the dimensional drive signals to augment the physical time delay provided by the spacing between the dimensional and stereo arrays.

This differs drastically from Carver Sonic Holography or Stereo Expanders because of the dimensional drivers.

Polk has already has the provision for a semi-active system with the biamp terminals. I am just taking it to the next logical step.

For those who are interested in active crossovers, you can google "active vs. passive crossovers" and something should appear.

There's been so much noise since the first post, that I'm afraid a lot of this may have lost.

The 1984 paper I'm talking about is not a "marketing" instrument. I think perhaps you might be referring to the newer "Surround Bar" paper which may seem to be more marketing than substance. I also never said the paper stated not to use "active" x-overs I was simply implying by reading the original paper you'd have a better understanding as to why "passive" components might have been used. Ans also a much better understanding of the SDA principle.

The answers to your questions are here in the forum but I'm not going to do the leg work for you. I'm also not trying to prove/disprove anything I'm simply giving my input to help you with your very broad statements (all passive x-overs will benefit from the use of active components) and sparse understanding of how the SDA works in the real world.

Have at it, but be prepared to back up your opinion/findings because there are quite a few on the board who know what they are doing. I welcome any new input but that input has to be from someone with some knowledge and it appears so far you have very little knowledge about SDA's. You've barely even had your SDA's and you still won't articulate specifically what issues you feel the SDA's are deficient in. You're just making broad statements and wanting to randomly fix/analyze things without rhyme or reason. I don't approach situations in that manner so I don't get where you are coming from, or where you are going, or where you'd like to end up.

H9

daifanshi

DarqueKnight wrote: »

What software did you use for the simulation?

Why would a forum member need to confirm the "correctness" of the SDA schematics posted here? They all have one or more approval signatures from Polk's engineering department.

Here are a couple of questions I posted earlier that I think you missed:





There are lots of SDA enthusiasts here and we love to share information about sonic performance. Some, like yourself, have fairly deep backgrounds in audio electronics.:)

I used pspice to simulate the networks. The driver models are guestimates but are close enough for the purposes of determining the basic crossover response.

The "correctness" would refer to the accuracy of the publish values versus the real thing. I did take a crossovers out once but I did not compare the values with the schematic. I could pull them out again, but I was hoping somebody knew already.

Sometimes there are undocumented changes in production to the design that happen "on the fly". And sometimes the released schematics are back-rev versions. Just wanted to make sure.

Cheers.

daifanshi

heiney9 wrote: »

The 1984 paper I'm talking about is not a "marketing" instrument. I think perhaps you might be referring to the newer "Surround Bar" paper which may seem to be more marketing than substance. I also never said the paper stated not to use "active" x-overs I was simply implying by reading the original paper you'd have a better understanding as to why "passive" components might have been used. Ans also a much better understanding of the SDA principle.

The answers to your questions are here in the forum but I'm not going to do the leg work for you. I'm also not trying to prove/disprove anything I'm simply giving my input to help you with your very broad statements (all passive x-overs will benefit from the use of active components) and sparse understanding of how the SDA works in the real world.

Have at it, but be prepared to back up your opinion/findings because there are quite a few on the board who know what they are doing. I welcome any new input but that input has to be from someone with some knowledge and it appears so far you have very little knowledge about SDA's. You've barely even had your SDA's and you still won't articulate specifically what issues you feel the SDA's are deficient in. You're just making broad statements and wanting to randomly fix/analyze things without rhyme or reason. I don't approach situations in that manner so I don't get where you are coming from, or where you are going, or where you'd like to end up.

H9

I approach electronics with the view than any and all things can be improved. I don't believe any particular design is sacred. If I think something is deficient, I will attack the problem. Often this goes against "conventional wisdom" and "tradition" and "common belief".

But I sense that many feel that I treading on hallowed ground. There was never disrespect intended and it should not be interpreted that way. Based on MY personal experience the ideas I laid out are perfectly reasonable and have technical merit.

If somebody doesn't like my posted ideas for some non-technical or whatever reason. Please don't read them. But even if there's ONE other person who can contribute to the art or learn from what I'm posting, then it was well worth it.

heiney9

daifanshi wrote: »

I don't understand how this marketing paper is relevant. I've read it very carefully and there is nothing in there that I can find that says the SDA speaker system can't be realized with active crossovers replacing the passive ones.

Can you point to me where it says SDA and active crossovers are bad? Maybe I missed that part. For completeness give me a page number and paragraph.

For those who might still not understand what I'm planning to do. I am going to recreate the passive crossovers of the SDA 2.3TL and change it into active multi-amp system. I am not playing around with the locations of the dimensional and stereo arrays or the tweeters responses. In the meantime I will add a provision for adjusting the phase alignment between the tweeter and midranges.

I will also add an adjustable variable delay to the dimensional drive signals to augment the physical time delay provided by the spacing between the dimensional and stereo arrays.

This differs drastically from Carver Sonic Holography or Stereo Expanders because of the dimensional drivers.

Polk has already has the provision for a semi-active system with the biamp terminals. I am just taking it to the next logical step.

For those who are interested in active crossovers, you can google "active vs. passive crossovers" and something should appear.

There's been so much noise since the first post, that I'm afraid a lot of this may have been lost.

Why? What's wrong with them now? What specific area's will this improve in the SDA 2.3TL? Please for the love of god start articulating some specific info relating to the SDA 2.3TL. Broad statements about active x-overs being better are nothing but smoke and mirrors. Talking about EPI's, Theils and Dulavy speakers has no relevance to the SDA 2.3TL. Name dropping will get you nowhere. None of those speakers are remotely similar to SDA's.

dorokusai

If you don't like what Daifanshi is trying to do....don't post in the thread.

It's his money, not yours and members' should be kind to newbies. Keep the discussion civil...is it really that hard to do? I'm not pointing fingers, just making a general statement.

daifanshi

heiney9 wrote: »

Why? What's wrong with them now? What specific area's will this improve in the SDA 2.3TL? Please for the love of god start articulating some specific info relating to the SDA 2.3TL. Broad statements about active x-overs being better are nothing but smoke and mirrors. Talking about EPI's, Theils and Dulavy speakers has no relevance to the SDA 2.3TL. Name dropping will get you nowhere. None of those speakers are remotely similar to SDA's.

H9,

Block my postings please. It's something I want to do. And it doesn't hurt you personally. So why care?

jakelm

daifanshi wrote: »

I approach electronics with the view than any and all things can be improved. I don't believe any particular design is sacred. If I think something is deficient, I will attack the problem. Often this goes against "conventional wisdom" and "tradition" and "common belief".

But I sense that many feel that I treading on hallowed ground. There was never disrespect intended and it should not be interpreted that way. Based on MY personal experience the ideas I laid out are perfectly reasonable and have technical merit.

If somebody doesn't like my posted ideas for some non-technical or whatever reason. Please don't read them. But even if there's ONE other person who can contribute to the art or learn from what I'm posting, then it was well worth it.

Dont mind those guys..:D They are just very sceptical on tweaks that have been performed time and time again, and those tweaks have failed more times than post.:p;)...but you never know....

Continue on your quest and let us know how it all turns out..

Good luck to you...

Face

Whatever you end up doing, post pictures along the way. Also, please make sure you are able to return them back to stock if things don't work out.

jakelm

SDA's with active crossover. Lets do it.....

geoff727

daifanshi wrote: »

Like I mentioned earlier, I hope my passive radiators never get kicked in. If I ever need a replacement, changing the length of a tuned port is a LOT easier than changing the mass-loading of a different PR to make it work right.

(Emphasis mine)
You know, this happened on a pair that was shipped to me once. The shipper ran one of the forks of a forklift right through it. Obviously, it ruined the PR. But, it also took off the particle board flange that the PR was mounted to. I didn't have the woorworking knowledge or wherewithal to fix that. I'm not even sure it could have been fixed. But, it illustrated to me, with the specific way that it was hit, that the passive itself is just about as strong as the wood it is mounted on. So, if a PR were kicked that way, and I'm sure they have been, the particle board might give way along with the PR, probably before if the PR was hit on the edge. It was a sad day for that speaker......

F1nut

Someone has been deleting posts again. :rolleyes:

ben62670

F1nut wrote: »

Someone has been deleting posts again. :rolleyes:

Yep I have some missing