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Major difference in speaker level settings


USNRET
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I finally got all three front Belles configured alike with drivers, horns, crossovers, etc. I started setting the levels and noticed that the left has to be set about 4dB hotter than the other two to achieve equal output. Hummm, I know I need to check wiring but asuming that all wires had good connections and are in phase, what would cause this? After wiring checks I think I will swap amp channels and take a look at that (Emo XPA-5)

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Could also be the room.

Yes, could be.

What kind of signal are you using to balance? I think there is no ideal choice. Many use band limited pink noise, e.g., 500 - 2K.

Others use music. Don't use a single tone. Don't use bass because the position in the room can make a big difference.

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I started setting the levels and noticed that the left has to be set about 4dB hotter than the other two to achieve equal output. Hummm, ...what would cause this?

A picture of your room might help.

I've also found that being off-axis in measurement position (microphone) can make a 1 dB difference, easy. If the room and room placement happens to also decrease the SPL from that side, I can understand 4 dB difference. Are you averaging more than one microphone position?

Chris

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Edit: no test tonight; all kiddos down with the stomach bug so no 'loud noises'.

I will investigate further tonight. I am using an analog RS meter mounted at ear level on a tripod at one location. Onkyo PR-SC5507 pre/pro self generated tone (noise). I set volume to achieve 85 dB at the SPL meter with 0 correction to the center speaker and then set left and right to match. I will jot down the numbers tonight and try to get a better picture of the room assuming that trying the suggested remedies does not reveal the problem.

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sample the AC voltage across each channel

At crossover input from amp using True RMS DVM at the reference level volume (or any volume as long as the amplitude and frequency 'should be' equal to the other speakers measured?)
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Voltage measuring will have to wait but here is some info. Analog RS meter "C" weighted and slow using pre/pro built in test. Meter on coffee table (mic up) at a height between top of bass bin and bottom of squawker. L & R slightly toed in but left more so (make my couch comfy spot better in 2 channel).

As you can see I was off in my first post's levels (old memory cells).

Speaker: L C R

Distance: 89" 72" 93"

Meter at 82dB -9.0 -12.0 -6.5

I will next swap L&R Pre > Amp cables, re-measure and if nothing proven proceed with the voltage checks. Later

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  • 2 weeks later...
  • 2 weeks later...

This took a little bit before I stumbled across the error of my ways. I still don't know WHY this would cause the issued but.........

After measuring, swapping cables, etc with inconclusive results I found that somehow my pre/pro had an in-correct setting. The fronts were set to "Bi-Amp". Changing this to the correct setting resolved the issue. Only minor PIA is that I found that this pre/pro doesn't let you change the tone volume with the master volume knob so with my speakers I have to set the center at -12 which is the minimum and adjust the others to it to get 85 dB at the couch.

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Why not set the speakers to be 75 db at the listening position. This is the standard setting for HT. The accurracy of the setting is in question when speakers are setup at the extreme of the calibration program. What is the max/min. speaker settings for the calibration program?

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I've found that setting my center Belle 6 dB lower (using SPL meter at listening position) than the combined output of my two flanking Klipschorns is just about right.

If you have a helper, try sitting at the sweet spot and while listening to a well-recorded vocal (e.g. James Taylor), have helper raise the volume of the center Belle until it is just noticeable. Shift your listening position left and right of center and note that the vocal image seems to stay more centered than with the center Belle off.

You will probably discover that raising the center Belle level to match each of the flanking loudspeakers (i.e. 85 dBL 85 dBC 85 dBR) is too much center fill.

Lee

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I've found that setting my center Belle 6 dB lower (using SPL meter at listening position) than the combined output of my two flanking Klipschorns is just about right.

That's because at the main LP, the center speaker is probably a shorter distance to you than the mains (assuming that the mains are equidistant from the center). In my setup, all 4 speakers are at different distances to the main LP. I set the center to 75db at 0 trim. Then I set the rest of the speakers accordingly. You also have to account for sensitivity of the speakers. USNRET doesn't have that problem since his LCR are the same.

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My Belle Klipsch center is set at the same SPL as each of my flanking Klipschorns, but the signals are being sent through an AV preamp that adjusts for the fact that the Belle is closer to the sweet spot seat (automatic time/distance adjustment in the pre-pro). It sounds just right for movies and many music CDs/SACDs, etc., BUT it is not right for some music disks. I think it depends on the kind of microphone placement the recordists were using. Before I had an AV pre-pro the Belle needed to be softer, which is consistant with the wide stage stereo articles in the Klipsch Audio Papers, written decades before AV pre-pros.

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Note: I only use the front three in HT 5.1 mode while using the same L&R with a completely different, discrete 2 channel rig. The center is not active in 2 channel even though I win a few bets with folks believing the center is playing.

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