I recently purchased a Pioneer Elite VSX-56TXi to upgrade from an A-35R integrated amplifier. I'm using the front and surround back channels to passively bi-amp a pair of Boston Acoustics VR-M60 bookshelf speakers hooked up with 10 AWG cables from Blue Jeans Cable.

My room is small and a bit odd (ceiling slopes both ways), but I am measuring at ear level with the mic facing upward at the center point of the speakers, which are roughly six or seven feet away.

I ran both the regular MCACC and the Advanced MCACC (Auto Pro), and they came up with similarly weird results. Take a look:

Left
63 Hz -0.5 dB
125 Hz -2.0 dB
250 Hz -3.5 dB
4 kHz -5.0 dB
11.3 kHz -5.0 dB
TRIM +1.0 dB

Right
63 Hz +4.5 dB
125 Hz +5.0 dB
250 Hz -2.5 dB
4 kHz -1.5 dB
11.3 kHz -3.0 dB
TRIM +0.5 dB

Judging by these results, the speakers must be incredibly bright... With the MCACC enabled, the brightness is tamed, but it just sounds wrong--over-EQ'd and lacking a ton of detail and resolution. Something strange is going on with the right speaker, and why are all of the frequencies being attenuated in the left channel?

What's my problem? Have I forgotten to do utilize some special mode in the receiver?

Left
63 Hz -0.5 dB
125 Hz -2.0 dB
250 Hz -3.5 dB
4 kHz -5.0 dB
11.3 kHz -5.0 dB
TRIM +1.0 dB


Is this speaker closer to something reflective? I think so because looking at this

Right
63 Hz +4.5 dB
125 Hz +5.0 dB
250 Hz -2.5 dB
4 kHz -1.5 dB
11.3 kHz -3.0 dB
TRIM +0.5 dB


I see that the bass is boosted and the treble rolled off less (but still might be because these speakers are perceived as bright by many auto-cal routines) indicating that this speaker is less-influenced by corner-loading or immediate boundaries.

We need pix.

What's my problem? Have I forgotten to do utilize some special mode in the receiver?

Remind me: Does the Pioneer have multiple EQ modes? If so, choose the one less intrusive or simply, the one you like best.

Thank you for the help, schticker! I'll add that I've removed the grills on both speakers since that measurement, and the midrange response has improved.

Is [the left] speaker closer to something reflective?
Yes! It's about a foot to the left and a few inches behind the front a TV. The TV is on a rolling stand, so I'll try moving it closer to the wall and out of the speaker's way. I had been thinking that it was far enough away not to cause significant reflections--maybe not.

We need pix.
I'll work on that. :D

Remind me: Does the Pioneer have multiple EQ modes? If so, choose the one less intrusive or simply, the one you like best.
Here are the EQing features... It has the normal Auto EQ, which is the typical surround setup (number of speakers, channel distance, channel level) plus a 5-band automatic EQ. Buried a little further into the submenus is Auto Pro, which does the same thing as Auto EQ but calculates and adds the room's reverb characteristics into the equation. Once it's done, the room's reverb characteristics can be viewed on-screen at each particular frequency (63 Hz, 150 Hz, etc.) for each channel.

There is a feature called "Advanced EQ Setup" that allows the reverb measurement time to be set, for example 0-20 ms, 10-30 ms, 20-40 ms, etc. up to 50-80 ms. The default is 20-40 ms. My small room is probably 12'x15'--is this a suitable time period?

Edit: I just read in the manual that if lower frequencies don't sound boomy, it might be better to measure the reverb at a further point than 20-40 ms, such as the 80+ ms used in the normal Auto EQ. I'll try that tomorrow.

Between the first measurements and the ones I'm about to list, I removed the woofers' speaker grilles and positioned the speakers at equal distances from the wall (roughly 11.5" to boost the bass response a bit).

Instead of Auto Pro, I used the standard Auto EQ, which uses a larger time window (after 80 ms) to measure the frequency response after the room's reverb has stabilized. Here are the EQ settings, before and after:

Left
63 Hz | -0.5 --> +5.0 dB
125 Hz | -2.0 --> 0 dB
250 Hz | -3.5 --> -2.5 dB
4 kHz | -5.0 --> -1.5 dB
11.3 kHz | -5.0 --> -4.5 dB
TRIM | +1.0 --> +0.5 dB

Right
63 Hz | +4.5 --> +6.0 dB
125 Hz | +5.0 --> +3.5 dB
250 Hz | -2.5 --> +1.5 dB
4 kHz | -1.5 --> -1.5 dB
11.3 kHz | -3.0 --> -4.5 dB
TRIM | +0.5 --> +0.5 dB

Now the speakers are closer to the other's response, though there's still something strange happening with the right speaker's lower frequencies. I bought them as demo speakers from Tweeter; the right speaker is several years older and is in worse condition than the left speaker, so I suppose this might be a result of overdriving it.

However, I'm more unsure of what's happening with the high frequencies. They're still quite a lot louder than the other parts. Maybe it's just the speakers' sound signature, after all. :rolleyes:

Well, a simple test is to swap the speakers left to right and see if the general response curve follows the speakers or stays at the same L/R location.

If you don't like the sound that Auto-EQ gives, don't use it.

Unless your room is acoustically treated and placement of the speakers and reflective objects are symmetrical, I doubt you are going to see all the numbers matching...IMO, of course.

Also, if you are standing anywhere near the mic at the time of the test, your body will be influencing the results too. Actually, pretty much everything in the room influences the result.

Thanks for the response, whoaru99.

I don't expect the speakers' frequency responses to be identical--my room is far from acoustically perfect. I've been laying down on the floor and breathing very quietly to avoid influencing the results. :cool:

Normally, I'd prefer to go without heavy EQ. The problem is that the speakers are unlistenably bright and fatiguing without it. :(

I'm assuming it's not the receiver; most people classify Pioneers as warm or neutral. I've tried different source components, but they aren't contributing to the problem either. I'm just afraid the problem lies with the speakers. Maybe they don't respond well to bi-amplification?

I think there is a better chance that the problem is the room than the speakers.

I doubt that those speakers are more than a very small amount different from each other when tested in an anechoic chamber. Put them in your living room and all bets are off.

Put some acoustic panels at the first reflection points and you'll think you just bought new speakers. Here is a good explanation of what those are and how to treat them.

http://www.realtraps.com/rfz.htm

Lots of information available on AVS on how to build your own if you don't want to buy them.

Thanks for the acoustics information, dae3dae3. I find that stuff endlessly interesting. If/when I build a studio monitoring setup, I'll be sure to keep reflections in mind. Also, I'm eager to read your "Ridicubass" guide.

Actually, I've solved my problem! :D

My speakers just didn't respond well to passive bi-amplification. I unhooked one set of wires and created jumpers with 12 AWG wire, and the response was suddenly balanced again (or at least as balanced as before).

Thanks for the help, guys!

I think I spoke a little too soon... The sound quality is still bright, but much closer to neutral. I'm still not sure what's wrong, or why the speakers would respond so poorly to bi-amplification.