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Old 28th July 2010, 07:54 PM   #31
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I was imagining...

Main amp with sub. Out > active filter > left amp > voice coil 1
-------------------------------------> right amp > voice coil 2

(sorry about the dashes, couldn't find a placeholder...)

You keep the advantages of a DVC system.
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Old 28th July 2010, 08:33 PM   #32
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Quote:
Originally Posted by Cal Weldon View Post
The signals are either in phase, mono or summed to center in the frequencies that would normally be sent to a subwoofer.


See above. You guys are worrying about the wrong things.
Have you ever looked at a lowpassed signal on a XY scope?

sub 80Hz are often out of phase, varying in strength and doing any other type of pirouette.
You can not assume the bass signal to be mono because it is simply not true in reality. Many say it should but I have seen numerous new recordings with varying content between the channels.
Sure many do have mono content in the bass region but even in those recordings they are differences.

Sending each half of a stereo signal to a DVC driver will cause unexpected things to happen.

Take a for example a simple pan. One VC will start with the full signal and one with nothing.
First of all you are now using half the motor strength. Second you are dissipating a lot of back EMF into the other channel.
At the middle if the pan you VCs are working together giving full strength.

This will give different Qes and BL through the pan.

Now a pan might not happen like that but much content bounce around at times and I would expect the sound to change to the worse.

Electronic music should have the habit to sum it to center right?
Well I guess not as I see a lot of O, ah and squiggles.


Using two amps to power a DVC is fine. Just make sure the signal is the same.
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Old 28th July 2010, 10:16 PM   #33
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Originally Posted by Boscoe View Post
okay that helps what would I need at the INV, NOR and SEL connections?
A changeover switch goes there. SEL is the selecting bit, NOR is to route normal-phase signals and INV is to route inverted-phase signals.
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Old 28th July 2010, 10:37 PM   #34
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If you were listening from down the hall, would you know if somebody pressed the "MONO" button? Even if you could detect the change (as you likely would), would it sound worse?

I don't know. Anybody know?

Footnote: "listening" to visual traces can be misleading.
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Old 29th July 2010, 11:36 AM   #35
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Bypass any potential problems by feeding both amps with the same signal. (summed to mono and low passed).

David, perhaps look at it from an artist's/recording studio's point of view. Most "hifi"s are small affairs, often put on a shelf. There would be no point what so ever in including bass that was out of phase between channels, as it would simply cancel out, and not be reproduced. That's also why few bother with low bass (<40Hz) any more - 99% of systems won't reproduce it.

You say there's differences between the channels where it's summed to mono. How have you tested this? Exactly how much difference is there?

bentoronto, I shall try flicking between mono and stereo, see if anything turns up...
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Old 29th July 2010, 12:06 PM   #36
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Quote:
Originally Posted by chris661 View Post
Bypass any potential problems by feeding both amps with the same signal. (summed to mono and low passed).

David, perhaps look at it from an artist's/recording studio's point of view. Most "hifi"s are small affairs, often put on a shelf. There would be no point what so ever in including bass that was out of phase between channels, as it would simply cancel out, and not be reproduced. That's also why few bother with low bass (<40Hz) any more - 99% of systems won't reproduce it.

You say there's differences between the channels where it's summed to mono. How have you tested this? Exactly how much difference is there?

bentoronto, I shall try flicking between mono and stereo, see if anything turns up...
More than 99%. Maybe 99.9999%.

There may be "visual" differences but that's not the same as auditory differences - even little differences or insignificant phase/time shifts look big on a dual trace scope. But often look milder when viewed as an X-Y plot or unhearable by ear.

You may be able to detect a difference among two speaker mono, single speaker mono, and two speaker stereo (and maybe other permutations). But that isn't the same as picking which is best (I am ignoring the benefits of spacing woofers around your room). I've opted for one grand corner Kliipschorn rather than two wee boomy bass reflexes.

Mono button - but remember, you should be down the hall when testing.
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Old 29th July 2010, 12:42 PM   #37
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I have a hall just outside my room, which is handy.

I was trying bi-amping my system with an active crossover, and my tripath amp isn't working properly, so there's a delay in the testing, I'm afraid.
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Old 29th July 2010, 02:47 PM   #38
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btw plate amps often come with crossover bild in.
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Old 29th July 2010, 05:21 PM   #39
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"But often look milder when viewed as an X-Y plot or unhearable by ear."

The difference between L and R is not insignificant when viewed on XY scope. Many recordings leave you with a "circle" if you leave the decay time long enough.

You are welcome to test it yourself.
Soundcard Scope
Lowpass filters are built in if needed. Decay time is limited when using filters though.

"Bypass any potential problems by feeding both amps with the same signal. (summed to mono and low passed)."

That Is what I have been saying, but people insist that the signal is mono below 80Hz in all recordings which is simply not true.


I would love to test the difference but I don't have a DVC sub.
Remember we are NOT talking stereo vs mono subs here. That is a matter for another discussion.
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Old 30th July 2010, 09:22 PM   #40
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Originally Posted by chris661 View Post
I have a hall just outside my room, which is handy.
snip
Well, I did my own experiment about whether mono sounds different than stereo down the hall. Seems dumb not to know elementary things like this, but I just wasn't certain.

Anybody want to guess before I give the answer?

First of all, inside your music room, if you put yourself in some odd location like behind one speaker, there's no stereo illusion. Need I add "duh"? There is an obvious although not profound change in ambiance, of course. But barely the illusion of the Dudamel Simon Bolivar Youth Orchestra recorded by DGG - big stage stuff - you get at the sweet spot. Nothing at all like that sweet spot ambiance when listening in an odd location with a stereo feed or much less than the stereo feed ambiance when listening in mixed mono, at least in my fairly damped room.

Now down the hall 15 feet, there is a slight difference in sound but not like you'd care to prefer A to B really.

So I think that stereo channels are created to serve certain wonderful purposes at the sweet spot. But away from that seat, it is just squiggles on a scope and you can play left, right, stereo, or mix to mono and not much different to the listener who gets them after playing into a room down the hall (unless maybe the engineer is doing funny stuff).

Anybody else try this 2 minute "experiment" in mixing channels?
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Last edited by bentoronto; 30th July 2010 at 09:25 PM.
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