Getting the full SDA Effect from Polk L800 Speakers

[sonofmagni]

Certainly all of these amp experts should be able to provide insight into my question regarding the “compatibility” for a Rotel 981? We got 3 pages dedicated to complete non-sequiters as it relates to a review.
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Any insight on my prior questions is appreciated

As I mentioned, the real issue is whether one speaker connection is gnd. If you take an ohm meter and go from the black speaker connections to signal gnd (like the outside part of an RCA connector), or to each other, and they are common, then you are good.

 

[Irvrobinson]

I believe that Rotel is a traditional class A/B amp and should be fine for the SDA technology.

If this is a Rotel RB-981, I don't think he can use it (two of them, actually) in bridged mode. Is it this amp, or a different Rotel 981?

RB-981-OM.pdf

Certainly all of these amp experts should be able to provide insight into my question regarding the “compatibility” for a Rotel 981? We got 3 pages dedicated to complete non-sequiters as it relates to a review.

God forbid time is dedicated to questions about getting the speaker. Literal weeks were spent figuring out how this speaker beat performs and under the right conditions it’s apparently mind blowing which leads me to want to buy it.
But instead addressing questions we’re treated to a meta analysis of arguments of naysayers who haven’t even heard it.
There’s not much info on the speakers anywhere other than here.

in other news: this demo of the port at the 18 minute mark is pretty cool:

Any insight on my prior questions is appreciated

 

[sonofmagni]

Bridge mode I believe by definition would be a balanced signal, so not what you want for these speakers.

 

[tjcinnamon]

If this is a Rotel RB-981, I don't think he can use it (two of them, actually) in bridged mode. Is it this amp, or a different Rotel 981?

RB-981-OM.pdf

I would use 1 channel for the highs and 1 for the woofers. I wouldn’t bridge them. I have 2, 1 for each speaker.
That is indeed the amp. I figure it will be 190W at 4ohms per channel.

thoughts?

 

[Irvrobinson]

I would use 1 channel for the highs and 1 for the woofers. I wouldn’t bridge them. I have 2, 1 for each speaker.
That is indeed the amp. I figure it will be 190W at 4ohms per channel.

thoughts?

I don’t think you’ll get any benefit at all from passive bi-amping, but it’s unlikely to do any harm either.

 

[Matthew J Poes]

I don’t think you’ll get any benefit at all from passive bi-amping, but it’s unlikely to do any harm either.

The only benefit would be doubling the power to the speaker (But as you will probably point out, it isn't like the woofer has access to that extra power). If you can simply use a more powerful amp, then that is easier. But if someone happens to have a couple extra amps laying around that only put out, say, 100 or 200 watts per channel, then using them in passive biamp might give a little headroom. In theory there should be a reduction of IMD, but I don't imagine it is meaningful or audible.

 

[Matthew J Poes]

For those open to learning more about reproducing live sound accurately (or the real musical event accurately) and the problems with existing approaches, I found some resources. We will be doing some more on this, with reviews of more advanced XTC products and more in-depth discussion of some of the SOTA solutions like Ambisonics.

Part 1: Problems with Stereo Reproduction and How to Fix Them

www.ambiophonics.org

-Now...Keep in mind, ambiophonics, while amazingly effective, doesn't work well with a stereo spaced pair of speakers, it works best with the speakers very close together and you need to be precisely placed at the apex of the listening triangle. While this works amazingly well, it never caught on for a reason (and it too introduces a problematic change in timbre.

The main benefit of this article is simply to provide some background on the distortions we discussed earlier. While I know some are being dismissive of these distortions, I still intend to educate with the hopes that some will understand.

https://chohner.com/docs/hohnerlein2016_ma_thesis_beamforming_CTC.pdf

Highly effective means of XTC while also being an interesting read in terms of background information

Whatever Happened to Ambisonics

More on ambisonics and soundfield reproduction

https://irp-cdn.multiscreensite.com/7b2b654758d449b08935c9dfa207e8f9/files/uploaded/THE%20AMBIOPHONE.pdf

More on soundfield reproduction with ambiophonics, the recording techniques, and a good bit of background

Recording the BBC Philharmonic orchestra in 3D – S3A Spatial Audio

www.s3a-spatialaudio.org

A group that has recorded, using higher order ambisonics, a symphony. These recordings are rare, but are becoming more common. Reproducing them accurately at home is difficult. The best options would be with two speakers and a good XTC filter, the mix then needs to be downconverted from HOA to binaural. Over headphones works, but there will be some problems still. It can also be reproduced over 5.1+ surround, but may in fact not be better than the 2-channel with crosstalk. Ideally you would have a mix of both but I am unaware of good home DSP solutions to that. At the end of the day, Ambisonics, while the future, is still not ready for consumer enjoyment. I haven't found the link to this recording yet, but will be reaching out to the team there to see if the dataset can be made available to me. If so, I have the tools to downmix ambisonics to binaural and 5.1/7.1 (no I can't do ATMOS sorry). Or who knows, maybe they have files already in these formats.

 

[Matthew J Poes]

I would use 1 channel for the highs and 1 for the woofers. I wouldn’t bridge them. I have 2, 1 for each speaker.
That is indeed the amp. I figure it will be 190W at 4ohms per channel.

thoughts?

Try it and see if you can hear a difference. It will only give a small increase in headroom, but if its what you have, try it.

I didn't try this, so I can't speak to how it might work. As I noted to Irv, in theory you should see a small improvement in headroom, but in practice I expect it to be very small. While it could reduce IMD in the amp, it won't reduce IMD in the speaker, so I don't know that it will be audible.

 

[STC]

I would like to comment about the part why the Polk need to be placed closely than the conventional stereo placements.

To have good attenuation of the signal reaching the opposite ear, you should able to cancel the signal by inverting the original signal and feeding it to the other speakers. Unfortunately, due to HRTF the response that reaches the two ears can never be identical unless the source is directly in front of you. The ideal speaker should be single speaker in the centre that launches the original signal and the inverted signal to the intended ears. This is known as Ambiopole.

Polk SDA is relying on this principle and suggest the speakers be placed much closer. Ideally, it is about 20 degrees ( that’s what I use with the Sound Lab speakers). If you have seen in ear response measurements this is the best compromise you can achieve without the sweet spot being too narrow.

Rest of the comments about poor side or centre is something I did not encounter although poor setting up may have a weaker centre if not corrected.

You can experience the concept by simply placing a divider between your speakers or if you have a DAW just invert the signals and delay the about 90 μs you should have a good cancellation.

You can read about crosstalk cancellation in the link already posted by Mathews above or just visit the institute or experiment the crosstalk by yourself.

 

[Ralph Glasgal]

The Polk SDA, the Lexicon Panorama Mode, and the Carver Sonic Holography were all pioneering attempts at correcting the effects of loudspeaker crosstalk. However they all had the drawback that they were nor recursive. That is they were one shot cancellation systems. The problem is that the reverse polarity signal sent to the near ear to cancel the signal from the other speaker also went across the head to the wrong ear and this sound was not also cancelled. This only partial cancellation sounds peculiar to a lot of listeners and makes angles and levels very critical. But without digital processors it could not be done then according to the theory but they deserve credit for trying. See www.ambiophonics.org for papers, tutorials, and the better hardware and software solutions now available..

 

[tjcinnamon]

Welp, I went and listened to the L800's at a speaker store. They were fantastic. With without the SDA effect, they were solid speakers and competed with my Paradigm Prestige but did not sound better than the Paradigm Founders 120 which I had side by side. That said with Room EQ at my house (Dirac), I'm sure the mid-range will clean up. Plus their listening room was a typical listening room for a stereo store (which was sub optimal but not terrible).

When the SDA was in full effect it was something to marvel at. As soon as I heard that these speakers were on my roadmap. However, he had an "open box", really it was no box they also have the Atmos modules in them which I have no use for. But I the L400 center, L900 Atmos, and L800 towers in walnut for $6100 which was basically free atmos and free center channel.

There ability to be put next to a wall is a good feature for me as well. Now I'm on the amp hunt. I'll have them about 6.75' apart with my listening distance at 9.75' give or take. Not perfect for these as they are supposed to be about 6' together but not terrible either.

 

[Golfx]

Welp, I went and listened to the L800's at a speaker store. They were fantastic. With without the SDA effect, they were solid speakers and competed with my Paradigm Prestige but did not sound better than the Paradigm Founders 120 which I had side by side. That said with Room EQ at my house (Dirac), I'm sure the mid-range will clean up. Plus their listening room was a typical listening room for a stereo store (which was sub optimal but not terrible).

When the SDA was in full effect it was something to marvel at. As soon as I heard that these speakers were on my roadmap. However, he had an "open box", really it was no box they also have the Atmos modules in them which I have no use for. But I the L400 center, L900 Atmos, and L800 towers in walnut for $6100 which was basically free atmos and free center channel.

There ability to be put next to a wall is a good feature for me as well. Now I'm on the amp hunt. I'll have them about 6.75' apart with my listening distance at 9.75' give or take. Not perfect for these as they are supposed to be about 6' together but not terrible either.

Well congratulations. I use the Anthem MCA 325 with great results.

 

[tjcinnamon]

Well congratulations. I use the Anthem MCA 325 with great results.

Thanks very much! I was going to ask what amp to get. I figured something that can play down to 2 ohms despite being a 4 ohm speaker. I was looking at an anthem 325 as well. It's pretty pricey. Looks like the Class D hypex and purifi aren't meant for this type of speaker. I have some Rotel 981's for now but I want to get something that can pull 400W at 4ohms. I wish they worked well with hypex or purifi. I had my eye on those for a while now.

 

[Golfx]

The Anthem MCA 325 is as faultless tank. Btw you are going to LOVE your L400.

 

[sonofmagni]

Thanks very much! I was going to ask what amp to get. I figured something that can play down to 2 ohms despite being a 4 ohm speaker. I was looking at an anthem 325 as well. It's pretty pricey. Looks like the Class D hypex and purifi aren't meant for this type of speaker. I have some Rotel 981's for now but I want to get something that can pull 400W at 4ohms. I wish they worked well with hypex or purifi. I had my eye on those for a while now.

Mine sound amazing with my MA352 if you like that sort of amp.

 

[tjcinnamon]

The Anthem MCA 325 is as faultless tank. Btw you are going to LOVE your L400.

Why do you say that about the 400?

 

[Golfx]

I listen to non binaural music recordings in Auro3d. The center 400 yields a really warm dominant presence. It’s tweeter matches those of the 800s which join to present a very enjoyable wall of music. Did you read the review of the 400? You definitely should.


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[tjcinnamon]

I listen to non binaural music recordings in Auro3d. The center 400 yields a really warm dominant presence. It’s tweeter matches those of the 800s which join to present a very enjoyable wall of music. Did you read the review of the 400? You definitely should.


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I did not but I figured it may add to the effect. The wide sound stage made the center (mono) feel a bit placed further back in the room relative to the other instruments. I figured a center channel would help bring that forward.

Also, I'm not a big audio adjectives guy so I am just placing things in the room. The big selling point was closing my eyes and hearing things literally outside the walls. It was quite the effect.

 

[tjcinnamon]

I listen to non binaural music recordings in Auro3d. The center 400 yields a really warm dominant presence. It’s tweeter matches those of the 800s which join to present a very enjoyable wall of music. Did you read the review of the 400? You definitely should.


Sent from my iPhone using Tapatalk

Just read it! It’s pretty exciting and a good review. I’m looking at the Anthem MCA 325 to see if they’ll cut me a deal with my big purchase. That is a Single Ended Amp, correct?

 

[Golfx]

Just read it! It’s pretty exciting and a good review. I’m looking at the Anthem MCA 325 to see if they’ll cut me a deal with my big purchase. That is a Single Ended Amp, correct?

Yes. Class AB single ended. Runs very cool. There may be their previous version (different face plate but same electronics) on eBay still new in box for a discount.