Third channel demonstration

[colterphoto1]

At the 2008 Pilgrimage there was a demonstration of the electrical mono third channel using digital delay via DX38 unit. Was there any handouts or does anyone have any notes regarding that process?

A Forum member has contacted me regarding such a setup and I'm trying to find notes. I have the DFH already on the traditional 3rd mono channel.

[DoubleJ]

Here you go Michael!!

http://forums.klipsch.com/forums/p/106402/1072330.aspx#1072330

JJ

[colterphoto1]

Thanks JJ and Bob R!

I'll pass this info along.

I've attached it here for easier searching.

M

3rdChannelDelay.pdf

[jacksonbart]

I don't really swing that way.

[LarryC]

How much was the Belle delayed relative to the K-horns? I think I recall something like 6 ms.

[Guest " "]

Three speakers....in DSP terms...we call this Pro-Logic...most HT recievers support this ability.

[DrWho]

I think I would enjoy 3-channel stereo a lot more with 3 identical
channels....I found the timbre mismatch between the belle and khorn
terribly distracting [A]

As far as the delay - it should be just
enough such that the center channel wavefront arrives at the listening
position the same time as the LR channels. If you figure roughly 1ms
per
foot, and a wall about 20ft wide...the center channel would be about
10ft away and the LR speakers about 14ft. So that'd be about 4ms from
my crude back of the hand calculation. The spead of sound is closer to
0.9ms per foot, so you're looking at more like 3.6ms. I believe the actual delay was closer to 3ms.

If you want an easier
formula - it should always be about 18% the width of the room in feet when the
khorns are mounted in the corners.

(When sitting on-axis of two corner loaded speakers, you will always
be a distance of X from the center channel and 1.414X from the LR
mains, where X is half the width of the room. The difference in feet is
1.414X - 1X, which comes to .414X. Divide by two to convert for the
width of the room and you're looking at a difference of 0.207Y feet,
where Y is the width of the room. The speed of sound is 1132ft/s, so
take the inverse of that, multiply by 1000 and you're looking at
.883ms/ft....multiply that by .207Yft and you get .183Yms....or 18% the
width of the room measured in feet).

There will need to be a slight offset to account for propagation
delays through each speaker, which is rather difficult to do with the
Khorn + Belle combo because there's no way to line up all three drivers
(without individual time delays for each driver). I think that's one of
the big reasons that there was so much allowable play with the actualy
delay setting....since for different songs, changing the alignment
would introduce different patterns of comb-filtering (essentially
acting like a phasey equalizer).

Maybe one of these days I'll have the opportunity to hear it with 3
totally identical channels...I think that would combine the strong
central image with a whole new level of clarity (of course, it's only
going to have that clarity for a single listening position centered
between all 3 speakers).

[colterphoto1]

Can that 18% be counted on? Doesn't the math depend on where you're sitting in relation to the front wall? I.E., if you were sitting 1 foot from the front wall, there
would be considerable difference in distance from ear-center and
ear-main, whereas the further back the listener sits, the less the
distance, hence the less the needed delay to bring all three into
proper time domain.

As we've discusssed in other threads, 1/2 the width of the front wall is not commonly the 'best' seating location and not practicable by many furniture placement standards (WAF). I have determined that .7 to .8 x times the front wall width is the most commonly reported 'good soundstage' for Klipschorns.

I'll recalculate 'Doc's Delay' based on your formula.

[DrWho]

My math was assuming you were on axis with the LR Khorns....giving you a 90degree stereo spread before the center channel is added.

When perfectly time-aligned and at the same volume, the center channel will reduce your effective stereo spread to 45degrees. Generally, about 60degrees is considered ideal, which I think requires the center channel be about -6dB relative to the LR mains.

Without the center channel, sitting back .8x the front wall width lands you at about a 60deg stereo spread (I think it's 64 degrees to be exact) [8-|]

[colterphoto1]

are you restating that this is why the .8 works? If so, great.

I'm too tired to recalc the Doc's Delay, care to help?

[DrWho]

Yep.

What's Doc's Delay?

[colterphoto1]

just a cheerful little name for your easy-to-calc third channel delay.

[DrWho]

So you want an easy number for when sitting back .8x the front wall width?

[colterphoto1]

let's call it .75 the range seems to be .7 to .8

it'll likely be somewhat less than the delay at 45 degrees because the change in distance (between main-ear to center-ear) won't be so great.

[BuyOtherSoundEquipment]

I think I would enjoy 3-channel stereo a lot more with 3 identical
channels....I found the timbre mismatch between the belle and khorn
terribly distracting

Someone actually was complaining about that during the free-listening session... Jay I think it was. I could not distinguish any timbre difference at all, although it was my first time to hear Khorns... and a Belle. lol

I thought the three-channel concept was excellent, and really effectively filled in the gap.