Pink Noise Test w/ 340 Fronts/Center

[stumacdo]

Hi all,

Was trying to dial in some of my settings last night for my new 340 F/C/L and noticed something strange. When using my Avia calibration disc, there's an audio test called 'Pink Noise Test'. In the instructions for the test, they indicate that the timbre of the pink noise should closely match, especially if you are using matching speakers. Strangely enough, on this test, the timbre seemed quite different between the 340 SE Fronts and 340 Center. Correct me if I'm wrong, but I thought the 340c was basically the 340 se front build to sit horizontally instead of vertically ? I have to say that the actual sound from these speakers has been absolutely stellar, but I was just surprised that the timbre would be noticeably different. Anybody else try calibrating with this disc and found the same thing ?

[BradJudy]

How are your speakers positioned? The center channel can sound different because it is often positioned different. If it's on top of a TV, is it tilted down a bit to point toward the listener? Is it inside a cabinet (can change the affect of the sound coming from the port)?

[Quinn]

Is your center a 340SE c or a classic 340C?

[stumacdo]

Center Channel is mounted above TV (using B-Tech 521) and is the new 340 SE Center.

[PLincoln]

timbre is affected by more than just the speaker/drivers themselves...location has a lot to do with it as well.

[MichaelG]

I too used the Avia disk and noticed the same thing (I have 340SE for left and right and 340SE center) :confused: . The center comes out a little darker than the mains. I also have it mounted above the TV. I did find that by kicking it up a couple of notches in loudness the timbre seem to match better on the Avia. Other than that, in normal useage I can't tell any difference.

Michael

[Jonnyozero3]

I've noticed the same thing, even on the test noise tones from my HK avr. It's subtle, but it's there. Of course, I have CBM-170s and a CMT-340C, all classics, so I'm not 340s all in front like the OP. I think I can go without the EXBAC compensation when I upgrade to SE's (front PJ setup), so I'm curious if that will make a difference.

[davef]

timbre is affected by more than just the speaker/drivers themselves...location has a lot to do with it as well.

Absolutely correct --- it is a practical impossibility to exactly match the timbre of the center with the left right speakers due to the major differences in positioning. EXBAC does a very good job of compensating for some of the differences, but even that is limited because every room is different. We can only predict a certain behavior based on what I would call an average and compensate for that, but there is really no such thing as an "average" room or "average" positioning.

If you are really curious, use one of the left or right speakers as the center and note the difference in timbre.

Also, pink noise is not a good signal to use for determining timbre between speakers placed in different positions in a room, it is appropriate for level matching (energy output) but the signal is weighted such that every octave has equal energy. The frequency response of pink noise looks like this:

http://www.purebits.com/images/apnot31.JPG

Every consecutive higher octave is slightly deemphasized (less energy) such that every octave band outputs the same amount of energy. The result of this is that when determining timbre between speakers (which is fully dependant on frequency response), more emphasis is placed on the low frequency response, which is much more sensitive to room placement / standing waves etc.

If you used white noise (equal amplitude frequency response, or “flat”), you would notice timbre would be much closer – but still not exact, which would still be an impossibility since you are at a different distance and angle from the speakers, besides the different room placements.

Hope you find this useful!