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Discussion Starter · #1 ·
Here is a plot of my in room frequency response. RS spl meter (C weighted, slow). My system is M&K 7.1 setup, S150THX front, right, center, SS-150 for sides and rear, 2 MX-5000 subs. Denon AVR-5803 using THX crossover frequency. I have not made any adjustment to the bass levels for the two subs. For this test, the subs were stacked near a corner.


Any comments are appreaciated. I am particularly concerned about the 95 Hz drop.
 

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Discussion Starter · #2 ·
Sorry,

I'll try to insert the picture again.
 

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The sub looks like it's +-3dB over it's range (i.e. pretty good for no EQ). For the upper frequencies, what speakers were playing? (i.e. did you send the 95Hz tone to all channels, just the sub, sub & mains, etc.). Where are the mains & surround channels placed in your room? What does the response for higher frequencies look like? Large dips could be caused by room interactions, speaker phase nulls (i.e. rears and fronts causing cancellation) or improper crossover adjustment. As you mentioned, the sub levels are higher than the rest of the system (~96dB vs. ~86dB) during this test...
 

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In regard to the 95hz dip, try reversing the phase (polarity) of the subs (switch on back) as this is close enough to the x-over freq. to be a possible cause but:


1. Although the Radio Shack is handy for "relative" level settings between channels, it is useless for response measurements, particularly at frquency extremes.

2. Even if you obtain better instrumentation the proper development of usable response charts requires multiple data points and educated analysis beyond the raw data.

3. Speaker/Room interaction probably accounts for more dramatic differences in performance in the lower octaves than any other single factor and these effects will vary significantly from one listener location to another.

4. You have excellent equipment (very similar to my own system), but if you want to obtain the ultimate in performance in your room, extensive analysis, acoustic treatments and/or a product like Audiocontrol's Diva would take it to the next level.

5. If your ears disagree with the test results, trust your ears and remember poor methodology can easily produce inaccurate test results.
 

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Discussion Starter · #5 ·
Thanks guys,


I was playing the granite audio test CD. I don't think it is strictly LFE and I am having my Denon use the normal THX crossover point (80Hz I think). I agree the levels are a little high but that is because I have both units at reference level. I will probably dial them down. The 55Hz is probably a room resonance. Any suggestions?


I will try some different locations this weekend and see what happens (now that I can make my own Canare cables). The RS values are corrected.

The 98db at 10 Hz is real and its strange to not hear much but the room starts shaking and air starts moving. Very cool.


I am attaching my room layout.
 

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I noticed that you stacked your 5000. The sub documentation says you'll get at least 6db boost if you stack.


I really love my 5000! You have a great setup.
 
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