Did everyone else already know this?

[Retread]

I hadn't paid attention to audio for about 25 years, having bought a decent stereo system at the time and not been unhappy with it since. Getting into home theater pushed me into acquiring a surround receiver and new speaker system (Ventriloquist and VTF-3R). The receiver manual doesn't explain things like frequency response per channel, precisely what "Large" and "Small" mean, and more particularly what they mean for individual channels. I had assumed that a surround receiver was more or less like a stereo receiver, with the individual channels having wide frequency response unless set to "Small," in which case I had assumed the bass was sent to the sub, but that otherwise the frequency response would be the same for all the channels.

On Lwang's suggestion, last night I began hooking my TrueRTA spectrum analyzer across the various receiver speaker outputs and discovered my assumptions were not at all true! In particular, the center-front speaker output looks like a camel's back. Putting center-front in "Large" extends the bass, but there's still a major roll-off above a few hundred Hertz.

So, did everyone on this site already know that? If so, what's the definitive reference that explains all this?

For my own curiousity, I'm going to run spectrums all the channels in both Large and Small, and I'm going to try putting a calibrated mic close to the individual speakers to see what's coming out of them.

If there were any interest, I'd be willing to provide screen shots of the results. But I don't know of a way to post them on this site. The individual screen shots probably exceed file limits.

PS: I got interrupted in running spectrums by the arrival today of my new screen. 100" tab-tensioned, electrically operated, HiDef Gray Draper Premier. Totally flat, for all practical purposes. Also finer-grained finish than the previous one I junked.

[Lwang]

What are you using for source? Is it a full bandwidth freq sweep at a constant dBFS level?

The center's rolloff might be due to THX's Re-EQ (or generic equiv). It rolls off the highs in the center speaker so that it sounds more like those junky no-fi horn speakers in the theaters. You should be able to turn it off, either with a switch or don't run Dolby in THX mode.

I think to post, you have to shrink it first, and it has to be in gif, jpg, bmp or jpeg format. Best to use jpg/jpeg since it will use the least amount of space. Attach the file under "Attach file:" when posting a thread.

[Active Speaker]

My home theater system actual sounds the best in STEREO, not Dolby Digital OR DTS.

[Retread]

[QUOTE]Originally posted by Lwang
[B]What are you using for source? Is it a full bandwidth freq sweep at a constant dBFS level?

Two sources, both from TrueRTA generators. One is a full bandwidth chirp, and the other is full bandwidth pink noise. I feed these from my laptop into the left/right front panel ports on the receiver and set the input selector to "Video." I have two ways of feeding output to the laptop, from bananas plugged into the receiver speaker outputs and from a Radio Shack SPL meter. The SPL meter gives me a fairly flat full-range spectrum, but the speaker outputs on the center give the hump.

I have the new "Digital Video Essentials" DVD, and note it has a bunch of tests for surround, so I'll give it a try also.

The result on the center speaker output was a surprise to you?

[Lwang]

The result on the center speaker output was a surprise to you?

Depends on whether you have Re-EQ or its generic equivelent enabled for the center channel, either via DD-THX or some center-EQ switch.

You should overlay speaker-level out vs actual speaker out also.