Any Polk Audio fan’s in the house?

S

shadyJ

Speaker of the House
Staff member
@Dkcivicsi06 Congrats on the win. I purchased mine at full retail. Its a great speaker if you have the room for it.

@shadyJ you can certainly do measurements. Just disconnect the SDA cable to get only the stereo mid/treble drivers. You may need to move the mic so its on axis relative to the inner active driver pair.

Also if you can please compare different Amps. I am having trouble recreating tHe SDA effect as much as I heard it in Polk demos using the same audio tracks. I think it maybe due to my choice of amps. I am using a McIntosh C47/MC452 and recently bought a Marantz PM-10 to try but get similar sound stage. The Mc is warmer sounding while the Marantz is crisp and brighter (not a bad thing).
Any difference in SDA effect will definitely not be due to the amplifier. It will have a lot to do with positioning and speaker placement within the room. The speakers are very sensitive to acoustic conditions.
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
@shadyJ I would suggest you speak to the speaker designer Scott Orth at Polk Audio. He mentioned to me the SDA signal is affected by amplifier topology. Single ended vs balanced differential. Per Scott the SDA was designed for single ended amplifiers. Most of the amplifiers I've been looking into to mate with my L800 are mostly the latter, I own a McIntosh Quad balanced and a Marantz PM-10 the others I'm considering are Yamaha S3000, PS Audio BHK and I'm not sure if the Anthem STR are balanced but It would be another I would consider.

Without going into too much detail, the derived SDA signal is only half of the wave from a balanced amplifier vs a singled ended amplifier where one terminal is typically ground and is only the signal return and you get full signal from the red speaker terminal.

Since you mentioned room. This is my room setup 25’x15’

Taken from the owners manual


I played with room positioning and settled on the following
X = 10.5’
Y = 10”
Z = 7’ 5”
S = 5’ 11” (right) 9’ 5” (left)
I haven’t heard the L800’s under official Polk conditions and wonder if the common feeling that the envelopment is not as good may actually be due primarily to music selection. I am finding these speakers to be highly sensitive to the musical content. A lot of music seems wasted on them.
They are also very setup dependent for sure. They seem to want to be far closer to each other than is typical. The SDA effect worked best for me (my room is very narrow at just 11’) at Just 6 feet apart.

I’ll need to ask Scott about what he is referring to. Nearly all amplifiers are not really single ended, they are typically a push pull design. But these amps are still ground referenced. A very few set of amplifiers are of a true differential balanced design. These contain two push pull amplifiers operates out of phase and have no ground reference. I could see this causing a problem, but I don’t believe any of the amps you mentioned are true balanced differential amps. The inked ones i know to fall into this category are ATI signature amps, the old Emotiva XPR amps, and some Class D BTL smps. I suppose some Class AB amps in BTL mode would also fit this, but not all. It depends how it’s done. I actually am not sure how Macintosh does the output of their amps since many use transformers. It’s possible the Macintosh Class AB design doesn’t reference the negative terminal to ground and in that case what you suggest could be an issue.

the amp I am using doesn’t have a ground reference. It’s a Class D BTL arrangement, so If what you say is true, I need to try a different amp. My Single ended amplifier is in need of repair, so I will have to do that ASAP to let me try it on these speakers. I guess a receiver is also always an option.

I’ll be sure to try these speakers with a variety of amps and sources. I’ll also be taking a number of highly technical measurements that I think will allow me to provide more information objective insight into what is going on.

Have you tried any binaural recordings? I find them spooky good on these SDA speakers. Hyper-realistic.
 
G

Gmoney

Audioholic Ninja
@Gmoney diyaudio.com I think. Look up PASS ACA. The kit is v1.6 and SE stereo or balanced monoblocks.

Found the info... SDAs need common ground amps, meaning the right and left channel returns are common.
Thanks! about how long it took you putting those together?
 
Pogre

Pogre

Audioholic Slumlord
Why would someone design speakers with competitive pricing in mind, but only sound their best with amps that are hard to find and very expensive..? I think I'd pass on these myself.
 
Pogre

Pogre

Audioholic Slumlord
@Pogre , to the contrary, the more expensive amps are the balanced differential kind.
Just displayed my ignorance there, didn't I? Lol.
.
Okay, so they don't require expensive amplification. From the duscussion tho it appears the single ended topology isn't very common?
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
Why would someone design speakers with competitive pricing in mind, but only sound their best with amps that are hard to find and very expensive..? I think I'd pass on these myself.
its actually quite the opposite. The kind of amplifier that SDA tech needs is the common type in use by most amplifiers. It’s a coincidence that I and the other poster are using a fully differential balanced amplifier. In fact, when SDA was first invented, differential balanced amps barely even existed. They are becoming more common today.
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
@Gmoney diyaudio.com I think. Look up PASS ACA. The kit is v1.6 and SE stereo or balanced monoblocks.

Found the info... SDAs need common ground amps, meaning the right and left channel returns are common.
I will be having a Polk engineer come out to my place to help with setup. I will ask about this and be sure I have an SE amp available to them.
I need to recheck the manual. I don’t recall it saying this.
I will say this. While it makes sense to me that this could be an issue. The tech clearly still works to some extent with a differential balanced amp. I took measurements to see if it reduced comb filtering and the results I obtained precisely matched what you would expect (since the SDA tweeters fall off above 10khz). I found a sizable reduction in combo filtering Up to 10khz. Quite a lot after that point (as would be true or any normal speaker).
 
Matthew J Poes

Matthew J Poes

Audioholic Chief
Staff member
@Matthew J Poes Cool! I think your article will be very helpful once all is said and done. The insights and tips you get from Polk is something we’re sure to all benefit from.

I’m on a totally different amp (PM-10 giving the MC452 a rest), and still enjoying the output. To really see if the amp topology makes a difference I will need to haul my RB-1590 out of my HT to test with.
I am in a similar boat. My only options for single ended amplifiers are an Onkyo receiver and an Acurus amplifier that recently started to motorboat. I had planned to have it fixed and never got around to it.

I look forward to your findings. I’ve also been talking to Al Griffin about his day experience. I found it insightful.

what other speakers have you owned or used? I’m curious what you think of the sound outside it’s staging. There is no denying that the SDA tech works. These speakers project a sound image like nothing else. However, a good review needs to address not only their one trick, but how they handle everything else. These are not cheap after all. I am forming an opinion but want to listen to them more before putting this in my review.

I also have to warn everyone that it is highly likely that this speaker will not have measurements like @shadyJ would normally include. These are just too big and taking measurements is going to be difficult. Unless a small army of people want to drag these out of my listening room and carefully set them atop a 6’ stand, withSoundUnited giving their blessing, I don’t see how we can do it. Instead, James and I plan to try two techniques that we have toyed with as an alternative for large speakers. We shall see id they work out.

I also plan to take binaural measurements and do a binaural listening video. The binaural measurements will be used to try and measure the degree of crosstalk cancelation. I am not certain this will work. Traditionally, studies measuring the effectiveness of crosstalk cancelation take a binaural measurements and calculate the difference between the left and right ear. A system that works perfectly would be such that a left channel sweep would be, say, 85dB in the left ear, but 0 dB in the right. That won’t happen in practice, but a substantial reduction in the right channel would lead us to believe its working effectively.

in addition I want to examine combfiltering. One or the arguments In the literature in support of crosstalk cancelation is that it substantially improves the response consistency of the center image relative to the left and right channel by reducing comb filtering. The literature suggest that this is audible and is one of the claimed benefits of a 3-channel front stage. By measuring a binaural impulse of the left, right, and lef+right I can compare and test this theory. If the left+right is highly correlated with the left and right separately (and this correlation is higher than with SDA off) then we can again conclude that it’s working as intended.

I figure I should take advantage of who I am and my tools and try to do the best review I can. Plenty of people will review this speakers subjective performance. Many will measure its basic frequency response. I want to measure it’s crosstalk cancelation ability, since that’s what makes it unique.
 
davidscott

davidscott

Audioholic Ninja
Congrats! The model 7Bs that I owned back in the early 80s had maybe the best midrange I ever heard. Close anyway to the large Magnepans a friend of mine owned. Enjoy!
 
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