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 The Effect of Interaural Crosstalk

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Sonic.beaver



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PostSubject: The Effect of Interaural Crosstalk   Fri Apr 30, 2010 1:39 pm

Hi Michael and fellow Zonees!

Sonic read that interaural crosstalk – that is when the sound from the Right speaker reflects over to the left and mixes into the Left signal (and vice versa) has a big effect on the realism of the reproduced sound. Saw this on the Ambiophonics website www.ambiophonics.org

Engineers and audiophiles have recognised this for years and tried several ways to keep the Left and Right signals separated at the ears – there was the Monster Cable baffle placed between the speakers which some built into divider walls that split the room in two and extended forward to the listening chair, there was Bob Carver’s Sonic Hologram which some say worked quite well and the Polk Audio solutions which had the speakers connected to each other with some active circuitry to drive a sort of inverse phase cancellation.

The Ambiophonics people (Ralph Glasgal et al) now use Digital Sound Processing to cancel crosstalk in the digital domain and when used with speakers placed close together creates stunning realism with a >150 degree front soundstage with 360 degree wrap around ambience.

Michael, would you comment on how significant do you see interaural crosstalk to be in your experience and if any of your products can be configured to reduce crosstalk in the room?

Sonic
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Michael Green
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PostSubject: Re: The Effect of Interaural Crosstalk   Sat May 01, 2010 9:37 am

Thank you Sonic for this post. It's good to be back BTW.

DSPs of any kind present a problem for the listener. "the signal pases through parts". They produce a mask over the music that is very noticeable to the trained listener. The devices can be fun on a Hi Fi level like many other electronic effects units but they are not the fix it tool that they are pumped up to be. So if a person wants to play in the synthetic world (which again can be fun) DSPs can deliver a colorful presentation. For serious listening this would not be my personal cup of tea.

Interaural crosstalk must be dealt with on an environmental level in my book. It's a tricky subject to deal with and hasn't received the press that many topics have in the audiophile world. Reason being most audiophiles don't want to dedicate their room to the level needed to address this phenomenon correctly. AeroPlanes are excellent wave dividers along with Sound Shutters, however it takes a lot of time, effort, and constant movement of products (every recording) to get things positioned decently. One thing I have learned is there is no fixed placement solution to acoustical and mechanical crosstalk.

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Robert Harrison



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PostSubject: Re: The Effect of Interaural Crosstalk   Sat May 01, 2010 6:53 pm

Hello, Mr. Green and Sonic,

I once had a pair of Polk's Stereo Dimensional Array speakers. I was looking to buy the same model Polks as my friend George at that time (non-SDA), but hearing that "spread" effect in the store convinced me to get the SDAs. This particular model (Polk had a few different SDA designs then) featured a dome tweeter over two horizontal mid/bass woofers. The speakers were designated as LEFT and RIGHT, the reason being that the inner woofer (closest to the listener) played only the signal from that channel, while the woofer further away played an out-of-phase version of the signal from the opposite channel. This was accomplished via the use of an interconnect cable hooked up to both speakers and whatever circuitry might have been involved.

Well, after a while I found myself constantly removing the interconnect cable to listen to pure stereo. The faked, "wider" stage just didn't sound quite right to my ears compared to a straight stereo signal.

I found the same with a CD that came as part of ad in Boxoffice Magazine some years ago for some Smart Devices movie theater processors which featured the Sound Retrieval System (SRS). The CD had tracks which played a bit of music or soundtrack material in normal stereo and then again with an SRS "enhancement." As I had a surround sound system back then (multi-speaker surround being something else I tired of), I noticed that the SRS signals made the surround channel become dominant, so I reckon the process just messed with the phase to accomplish its particular effects.

Listening to this SRS CD in stereo, you could hear more going on all around the room from 2 speakers, but the character, the "feel" of it, let's say, again just didn't ring true with me. By the way, the SRS on those theater processors was only used after the matrix decoding on the front left and right screen channels only.
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Sonic.beaver



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PostSubject: Re: The Effect of Interaural Crosstalk   Sun May 02, 2010 7:22 am

Greetings Mr Harrison!

Good observations and thoughts on the Polk speakers. I have heard a pair of Spendor professional BBC monitors in a system using one of the more recent British room-correcting DSP systems and have to say I preferred the sound of the BC-1s unprocessed. For sure, the processor was not dealing with crosstalk but room resonances but I guess the result is instructional on the genre of these devices.

Now this system is a good one and the owner has great taste and collects LPs of great music from the Classical, Romantic and modern eras. On its own, you know you are listening to a quality system. Now if you read the DSP manufacturer’s MLSSA plots, you’ll think this solves everything. The device, through its measuring microphone, can reverse polarity in the decaying signal to correct for the room. This device sensibly deals with peaks and does not attempt to boost the valleys which could overload amplifiers. It is not exactly cheap (understatement).

With the DSP switched in, the first impression is “wow!”, where everything is clearer and more open but as listening progresses, you become aware of a sameness…every LP starts having the same timbral characteristics. There is an artificial clarity that pervades. Yes, bass is better, highs are clearer but the music is less real. It has become mechanical. And this could be the tale of these DSPs that correct for rooms, systems and crosstalk…

One exception is possible: Mr Green is the either the designer or consultant to the DSP manufacturer…:=)

Sonic
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Sonic.beaver



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PostSubject: Re: The Effect of Interaural Crosstalk   Mon May 03, 2010 9:26 am

Hi Michael

You said the the magic words to Sonic: " it takes a lot of time, effort, and constant movement of products (every recording) to get things positioned decently. One thing I have learned is there is no fixed placement solution to acoustical and mechanical crosstalk."

End of my interest in this topic...

Sonic
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Michael Green
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PostSubject: Re: The Effect of Interaural Crosstalk   Tue May 04, 2010 6:46 am

Hi Guys

Yes, this topic is typically approach by our audio experts with something to prove instead of physicists who will tell us that the only way to deliver sound on a some what of a consistent level is through continual tuning. It's not brain surgery, and I'm always amazed that people in this industry are permitted to make statements and build designs that defeat the purpose of music at it's very core. Tunees are living proof that we need to look at music as a multidimensional art form which we are participants of.

I'm not sure why audio designers have a tendency to be so fixed in their thinking. It may be the ego of having the answer that the others don't. I'm not sure but for myself I get excited over the act of tuning something in. The magic of the moment has always been a thrill for me. Tuning is not another method to get good sound, but rather the method of nature on a moving planet that will be in constant movement forever. We as listeners (who love our music) need to embrace this hobby on it's positives instead of making up things that only make us lazy listeners. I can't imagine a musician not wanting to stop and tune their instrument when it gets out of tune. Our stereos are the same, but maybe we don't want to except that the world is a changing continuum. How can these guys talk about fixed answers without looking up and seeing the clouds moving across the sky, or hear the oceans roar.

Here's a basic

The rotational speed of the Earth at the equator is about 1,038 miles per hour. The atmosphere at the equator is also slightly thicker due to rotation, and you weigh slightly less. At mid-latitudes, the speed of the Earth's rotation decreases to 700 to 900 miles per hour. These types or variations are huge in my book and definitely effect the sound of our systems in a big way.

I'm glad that at least here on the techno-zone we know that we are moving on a sphere that is not only spinning fast but is also moving at 18 miles per second while it spins. Sometimes I'm not sure what planet audio designers are from, but I do know that calling something absolute is only as good as the moment and is unlikely to ever be repeated exactly the same again. This should not be disheartening for the music lover, but instead we should feel privileged that we have the ability to take in "this magic moment".

Again thanks for bringing to our attention the technologies of audio that need to be looked at to see how or if they should be a part of our world. If they do become a part of our world we'll be there to tune it.

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