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Discussion Starter #1 (Edited)
I took a few measurements in the main listening position in my setup at various SPL levels to get an idea of how much bass I "need", and how close I am to getting there with low distortion. I'm wondering if folks on the forum have done the same / have SPL numbers with distortion graphs available at their main listening positions (MLP)?

(is there a way to average the SPL / distortion over the frequency range that is industry accepted?)

Here's my setup:

Code:
Denon X4400H 5.2.4 (no subwoofer, instead running front LR full range, pre-out > MiniDSP 2x4 HD)
24dB LR HPF @ 60Hz for Behringer iNUKE NU1000DSP > HSU front speakers
24dB LR LPF @ 60Hz for Crest Pro-LITE 7.5 amp > 2x18" Dayton Ultimax sealed
I am not utilizing the amp(s) to their full potential, I've yet to perfect the gain structure (and EQ/integration). But it's a decent start.

Measuring with the MiniDSP UMIK with its calibration file. First, comparing the -10dB, -5dB and -2dB measurements below. We can see that distortion is under control (at/under 20% THD) at -10dB AVR volume, or between 100-112dB. When going up 5dB, THD rises to 20-30% under 23Hz, SPL levels around 105-115dB
Going up another 3dB with the AVR now at -2dB, we see around 105-118dB at the listening position - with distortion creeping up to 35% at 20Hz and more below.

So it would appear that I am limited to around 100-112dB between 12-100Hz at the MLP if I want to keep distortion below 20%. However, the system is capable of more if more distortion is allowed under 23Hz. Considering one of these drivers produces around 106dB @ 20Hz according to Data-Bass, the room gain is real.

Full album: https://imgur.com/gallery/fRaAxzX



 

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Discussion Starter #3
Interesting post, thanks for sharing...

I'd be curious about the distortion, and how much is being contributed by each component (like identifying the weakest link, etc).
The distortion levels are posted. In terms of what contributes - it's most likely the subwoofer setup - asking too much of the drivers. I could lower that distortion by offloading some work the drivers are doing by going ported, but I don't have the room for it.
 

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The distortion levels are posted. In terms of what contributes - it's most likely the subwoofer setup - asking too much of the drivers. I could lower that distortion by offloading some work the drivers are doing by going ported, but I don't have the room for it.


Sorry for any confusion, I read the results as total distortion of mains plus subs since you are running your speakers as large. I was curious what distortion would look like for each speaker individually... my guess is actually that the low bass distortion is more from your mains than subs actually and might improve by setting the speakers to small and crossing at something like 40 or 60hz?

Then again, that would totally mess up any integration work you did through map and the mini dsp and require starting over on that...

The subs should be way more output at a lot lower distortion for a given spl than your mains is all.

Like I said, I like the data and info, thanks for sharing. I might actually sweep the mains set to full to find out where they distort to optimize the crossover to eliminate that distortion since you can...
 

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Discussion Starter #5
Sorry for any confusion, I read the results as total distortion of mains plus subs since you are running your speakers as large. I was curious what distortion would look like for each speaker individually... my guess is actually that the low bass distortion is more from your mains than subs actually and might improve by setting the speakers to small and crossing at something like 40 or 60hz?

Then again, that would totally mess up any integration work you did through map and the mini dsp and require starting over on that...

The subs should be way more output at a lot lower distortion for a given spl than your mains is all.

Like I said, I like the data and info, thanks for sharing. I might actually sweep the mains set to full to find out where they distort to optimize the crossover to eliminate that distortion since you can...
Apologies for the confusion, I edited the first post to include the crossovers. The subs and mains are crossed at 60Hz, respectively (24dB LR). Perhaps adding a HPF @ 10Hz for the subs, and/or changing to a 48dB slope between subs/mains might be worth a try. At these levels you might be right - the added distortion might be from the mains.

(I could just measure again with the mains muted)
 

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Apologies for the confusion, I edited the first post to include the crossovers. The subs and mains are crossed at 60Hz, respectively (24dB LR). Perhaps adding a HPF @ 10Hz for the subs, and/or changing to a 48dB slope between subs/mains might be worth a try. At these levels you might be right - the added distortion might be from the mains.

(I could just measure again with the mains muted)
Got it, missed that update! Things definitely get complicated in a setup like you have... good luck, hopefully you can find some zen (at 110db, lol)!
 
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