From: chrisc@gold.gvg.tek.com (Chris Christensen)
Newsgroups: rec.audio
Subject: Re: Pro Logic Center channel speakers
Keywords: pro logic
Date: 10 Nov 92 00:22:18 GMT
Article-I.D.: gold.5516
Organization: Grass Valley Group, Grass Valley, CA

In article <464@bit.UUCP> grego@bit.UUCP (Grego Sanguinetti) writes:
>In article <5495@gold.gvg.tek.com> chrisc@gold.gvg.tek.com (Chris Christensen) writes:
>> <in response to center channel speaker inquirey>
>>I have posted, at length, on the center channel speaker issue.  I
>>won't get into detail now but I will spout my personal observation....

>And I usually counter with an alternate viewpoint, also at length....
>(All do respects to Chris, who's opinions I respect).

I _can_ be bought with gratuitous compliments...  :-)

>>If your atempt is to reproduce the theater sound system in the home,
>>then you must use a full size speaker that is identical to the
>>left and right speakers.

>The only thing you "must" do is enjoy yourself! I spent the bucks for a
>full blown Pro-log system several years ago for one purpose:
>to get the maximum excitement out of my video system.

Yea I forgot that factor,  It's been a really stressfull time........

>I have tried a number of different speaker combinations and found that
>electrostatic and planar speakers produced the most exciting effects. However
>they didn't work well for the center channel. For one thing they are too
>big. The other problem is imaging. In my opinion, the center channel should
>be a point source. It should be quite obvious that the sound is comming
>from the middle of the screen.

Here is the comment that I was looking for!  For the most bang in the
surround effect world the speakers should match so that the amplitude
cancellation between the front speakers and rear speakers have a
chance to "create" the surround effect.  Defuse field speakers like
electrostatics are fun to listen to but lack the point of source that
will produce the best effect (correct me if I'm wrong......).

>With this in mind I chose to use two small (8") speakers on each side of
>the monitor, run in mono (of course). They are old Altecs and have a nice
>warm sound especially suited for voice. They also work well for explosions!

I would like someone who has a pro-logic system and doesn't believe
that there is any low frequency information from music and effects in
the center channel to connect up the center channel to a left or rignt
and see for your self.  Or go to a theater that has a suitable Dolby
Stereo system and listen........

I wouldnt't be surprised that the pro-logic people that brought us
mis-matched center channel power to have brought us limited bandwith
also.  I will have to refer to my Dolby Stereo Spec Manual but as I
remember it the center channel is full bandwith.

Also another poster suggested that a subwoofer would seem to solve
the wimpy center channel problem ( I paraphrase of course..).  Yea a
subwoofer will save the whole problem ('cept for the Maggies....).

Two full size speaker systems, one reduced bandwith center channel
(with the same mid-n-high drivers that the left and right has) with a
subwoofer will work wonders!  The big improvment here is the sub....
And don't under power the sub!  Please.  At least 2X the left/right
power.

>I do agree that the center speaker and the L-R mains should work well
>together. It is important that sounds that move from the center to one
>side transition smoothly. I worked that with trial and error and a touch
>of EQ.

>>To correctly and accurately reproduce dialog the bandwith of the
>>center channel speaker should be flat (not -6 dB down) for the
>>bandwith of 100Hz to 10 kHz.

>Yes, as I remember from the liturature the center channel is rolled off
>below 100Hz. That's still pretty low though. You need good bass response
>to make Lurch sound good B^)

My comment wasn't intended to justify limited bandwith center channel
speakers or to suggest that the center channel is a limited bandwith
channel.  Sorry if that's the way it reads...

My intent was to give an example of a system that was required to
reproduce the voice correctly to show how futile a reduced bandwith
speaker is for center channel......

>>The theater systems that you are trying to duplicate in the home are a
>>minimum of three full size speaker systems in the front and array of
>>speakers for the rear.

>I also don't agree with the wall of sound behind the listener, but I'll
>save that for a different post.

My information comes fron technical puplications from Dolby as well as
others.  Based on this post and my other postings on the subject I am
surprised that anyone would disagree with me  :-)

>>I don't want to hear flames about architectural problems relating to a
>>full size center channel speaker,   that's what you should spend you
>>time solving....

>Yeah right Chris no problem, Martin-Logan talks about how their speakers
>are transparent right?

:-)

-- 
Chris Christensen                  The opinions I express are my own,
chrisc@gold.gvg.tek.com            and sometimes they are wrong!
916-478-3419 FAX 916-478-3887      After all, I *AM* only human.
Newsgroups: rec.audio