Reduced bass output at higher levels? - AVS Forum
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post #1 of 9 Old 06-04-2011, 08:23 AM - Thread Starter
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I have been messing with this issue now for a few days on my own, and felt it is time to share with my fellows at AVS.

I recently revamped my home theater system by adding the following:

Using an RDL FP-UBC8 unbalanced to balanced converter I am running my 5.1 direct outs from my Onkyo 805 to a pair of Face Audio F500TS to run my LCR. I am running balanced out from the RDl to the balanced in on my sms1 then out to a qsc pl380 that is currently running a defunct mfw-15 with a dayton dvc 15 driver in it (I know...overkill, but new subs are next). I have dedicated 20 amp lines for the amps as well as Furman power regulators and PFi units.

Here is the issue. I have gone ahead and set my gain stage from Onkyo to amps, and then ran Audessey. When I am playing a bass heavy track I am very familiar with, the bass level (and subwoofer excursion) are in line with the level of my mains. Problem is, when I get close to -0- on the Onkyo, the bass (and excursion of the sub) is lower in level while the mains are obviously getting louder. It seems like there is a limiter of sorts butting in and clamping the sub out signal. I have checked to make sure all limiting is off on the amps, but still have the issue.

Any ideas as I was fine with a Face f500ts running the sub before without issue? Making me wonder if it is something to do with the QSC PL380?

Denon 4311ci with Mini DSP and antimode
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post #2 of 9 Old 06-04-2011, 08:32 AM
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Check the Onkyo for midnight mode or a sub limiter function.
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post #3 of 9 Old 06-04-2011, 08:45 AM
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See if Dynamic eq is turned on. That does boost bass at lower levels and then less and less as the volume is raised.
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post #4 of 9 Old 06-04-2011, 10:01 AM - Thread Starter
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I don't have Dynamic Eq on the 805. I checked and late night mode is not engaged and I can't find any sub limiter function.

Denon 4311ci with Mini DSP and antimode
L/R -DIYSOUND tempest towers (40" tall towers)
C - DIYSOUND alchemy 8
LS/RS - community D6

MACHTSUB SYSTEM
2-Stereo Integrity HST-18 D1 subs (happy dance) in dual 12 cuft ported tuned 16hz
Sub amp- inuke 12000dsp (byopc) bring your own power cord
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post #5 of 9 Old 06-04-2011, 04:06 PM
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low pass filter engaged on teh QSC? Using an input sensitivity setting other than 1.2V?
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post #6 of 9 Old 06-04-2011, 04:11 PM - Thread Starter
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High pass is off on QSC. I had the input sensitivity set to 32db, so I will switch to 1.2V and see what we end up with.

Denon 4311ci with Mini DSP and antimode
L/R -DIYSOUND tempest towers (40" tall towers)
C - DIYSOUND alchemy 8
LS/RS - community D6

MACHTSUB SYSTEM
2-Stereo Integrity HST-18 D1 subs (happy dance) in dual 12 cuft ported tuned 16hz
Sub amp- inuke 12000dsp (byopc) bring your own power cord
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post #7 of 9 Old 06-04-2011, 05:02 PM
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hopefully will help. on the 32 dB setting you get 32 dB of gain at about 2.6 V (which your Onk may not be able to put out) while on 1.2 you get 39 dB at 1.2 V. Thats a little over 10 dB more gain for a given input (so over 10 times the power out for given voltage in)
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post #8 of 9 Old 06-05-2011, 09:38 AM - Thread Starter
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Well, the bass is still reducing at higher levels. It just seems strange that this did not happen with the Face amplifier. I'm going to try a few different gain stage settings and see what happens. I'm kind of frustrated that going from a 500 watt into 4 ohm stereo (Face amp) to a 2500 watt into 4 ohm (pl380) resulted in less bass... Something is not right.

Any other ideas?

Denon 4311ci with Mini DSP and antimode
L/R -DIYSOUND tempest towers (40" tall towers)
C - DIYSOUND alchemy 8
LS/RS - community D6

MACHTSUB SYSTEM
2-Stereo Integrity HST-18 D1 subs (happy dance) in dual 12 cuft ported tuned 16hz
Sub amp- inuke 12000dsp (byopc) bring your own power cord
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post #9 of 9 Old 06-05-2011, 12:20 PM - Thread Starter
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Well...I forgot that I switched from "RCA in" to the SMS-1 to "Balanced XLR input" from the rdl unbal-balanced. So I switched it back to the RCA in direct from my Onkyo RCA sub out and TADA...Bass has been restored at higher levels.

It seems to me that there is some sort of limiting circuit in the SMS-1 that velodyne puts in there. Not sure how I could be overdriving the SMS balanced in(since I reduced the gain to it on a few gain restructures and it still clamped the bass at higher level. In all cases it was electronically limiting the signal.

Im just glad the bass is back

Denon 4311ci with Mini DSP and antimode
L/R -DIYSOUND tempest towers (40" tall towers)
C - DIYSOUND alchemy 8
LS/RS - community D6

MACHTSUB SYSTEM
2-Stereo Integrity HST-18 D1 subs (happy dance) in dual 12 cuft ported tuned 16hz
Sub amp- inuke 12000dsp (byopc) bring your own power cord
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