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TOPIC: 6 Subwoofer EQ using the Mini-DSP

6 Subwoofer EQ using the Mini-DSP 2 years 8 months ago #5053

  • kwcouch
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Just wanted to report my general assessment of my experience using the mini-dsp 2x4 balanced box with the advanced 4-way xover module to EQ a 6 sub-woofer system used for home theater.

The objective is to EQ the subs to achieve 2 primary goals: To achieve a flat frequency response from 15Hz to 60 Hz and to balance the peaks and nulls across a 5 seat listening area (15' span). The second goal of achieving the generally flat response across a 15' listening area is the bigger challenge. Part of the reason I have 6 sub-woofers (besides the obvious SPL) is to distribute their placement in the room to achieve a more uniform sound.
Sorry I did not take a lot of pics... but I am posting a picture of my two 15" TC-Sounds subs integrated into my front wall( also have 6 12" drivers but you can ignore those for this review), and my 18" Dual Passive Radiator (TC Sounds) sub. I also have two SVS Ultra subs, and a 15" Earthquake sub that are not shown. My room is 60% sound treated and is 20' x 30' x 9' ceiling. I am using the 4 outputs of the Mini-DSP to control 1) Two Front TC Sounds 2) 2 SVS subs on right side 3) 18" TC Sounds on back-left and 4) 15" Earthquake on front-left. The input to the mini-dsp is tied to the LFE output on my Denon receiver.

The bottom line: I am very happy with the flexibility and outcome of the results. I used the BW filters on each of the 4 channels which gives me a very sharp roll off on each end of the filter. On the low end, I can push my subs to 17 Hz, but still have a significant roll off at 13 to 15 Hz to protect them from being over driven. On the high frequency roll off (60Hz), I can easy integrate my other speakers for a seemless frequency response.
The 6 PEQ adjustments on each channel allow me adjust for peaks and nulls. There are many combinations that will change the outcome when you are dealing with so many subs. It is time consuming and is a little bit of trial and error. In the end I was able to get reasonable flatness at all listening positions.. however, I did optimize a bit more at the main listening position in the center.
The mini-dsp balanced version allowed me to push both PA amps using XLR inputs and plate amps using RCA inputs. The .9V input on the DSP matched well to the my Denon LFE output and the 2V output lined up nicely with my PA amps and with my plate amps. I could gain down the level for the plate amps using the individual output controls on the mini-dsp. I even had to invert the phase on one of my subs in order to get the best response.

I do have one negative that I have found. When you power down the mini-dsp, it creates a significant pop on the outputs. Since I have auto-sensing amps on two of my subs that stay on for a couple of minutes after the last detectable signal, I have not been able to find a good way to eliminate this pop on power down. My current solution to the problem is not to power down the mini-dsp. I just leave it on all the time and the problem does not occur. If anyone has any suggestions on how to fix this, I would be interested. I think there is a small module that mini-dsp has which will add a 3 second delay on power off... but if it does not eliminate the pop... my plate amps will still pick it up.
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6 Subwoofer EQ using the Mini-DSP 2 years 8 months ago #5077

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Wow... that's indeed a lot of subs!!
Please don't take it bad but I wouldn't want to be your neighbor... ;-)

Sounds like a great project and thanks for sharing your setup. Quick question on the tuning, have you tried to see if REW would be able to help on the tuning? It indeed sounds like a lot of potential tweaking required to make these 6 subs work together.

With regards to the power down, the order for a processed system should be:
- Turn ON DSP/Sources
- Turn ON AMP
....
- Turn OFF AMP
- Turn OFF DSP
one way could be a power bar with sequencing. The other one (more DIY and being on AC power you have to be a LOT more careful) would be to find a power bar/AC plug with a contact closure that you could drive with a circuit like a miniDC. (integrated delay minidsp.com/onlinestore/detail/8-accesso...dc-isolator?sef=hcfp.. Just a thought.

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6 Subwoofer EQ using the Mini-DSP 2 years 8 months ago #5106

  • kwcouch
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I do use REW to run the sweeps to EQ my subs as well as the rest of the system.

I also use current sensing power strips, except for my subs that have auto-sensing inputs. This allows me to plug them into the wall near their location. The auto-sense does not cut off the subs for several minutes... thus the popping from the mini-dsp still exists. Still keeping my mini-dsp on all the time... no problems with popping. Hopefully this does not cause any adverse effects on the mini-dsp.
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