Trying to align and Eq 4 subwoofers with REW, Umik1 and Minidsp 2by 4 HD. Is this output what I should expect?

warek

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Hi all

Thanks for the forum. I have 4 identical 18 inch sealed subwoofers with Hypex DS8 plate amps. The room 5.3*4.5 metres with 2.7 metres ceiling. This room is used for watching movies and the subs have been individually measured, moved around, remeasured and then taken a combined measurement. The subs are basically close to 4 corners of the room. I probably do not need 4 subwoofers in this room but they came from a different house and a much larger movie room that was lacking bass. I have not tried only EQ 1-2 subwoofers.

I am trying to achieve more bass below 30 hz.. The subs designer has modelled the subs as one sub can produce 120dB of output about 25Hz and at 20-15hz and below it can still produce 110dB

I have tried time aligning the subs in REW and have tried them in all combination over the last few 3-4 months. Eg 1234, 4321, 3241, 3421. Time alignment gives me a better aligned response with lower bass and removes some dips than simply playing all 4 subs together. It gives me delays on some subs and suggest invert polarity on 1 or 2 subs depending on which order I start with. My concern is that when I then try and Eq the aligned response and import into the file into minidsp 2*4hd and measure the actual response is not close to the predicted response. I also find that when I enter the time delay and inverse polarity from the aligned response into the minidsp that the actual response is worse than if I leave the delays all blank and ignore the suggested inverse.

I get a reasonable result if I try and have a 2db room/house curve and a target level around 81 hz. If I try and add a larger 3,4,5,6 db house curve the actual results are much more ragged.
4 subs non aligned and aligned sum.jpg
actual Eq results.jpg


I think I am making progress, and this is the best results I have so far. I am now listening to a few action movies with good bass soundtracks.
Is this the kind of result that I would expect? These are non smoothed results. In the image of the actual results Sweep 9 config 1 has a low shelf at 35 hz with 4 db gain and a Q of 1.0 entered on the input side of the MInidsp 2by4HD. Sweep 6 has a 20 HZ peak filter 5 db gain entered into the minidsp input side.
One thing I am finding hard to follow is that I have a 105 db output at 42 HZ before EQ and EQ is applying 15 Db cut to this peak. I have tried to manually reduce the amount of cut at this frequency but without great success in actual results

I have not spend much time adjusting subs with mains but have mains crossover set at 100 hz, and the subs are running full range. The mains are two way speakers with 8 inch bass driver
I do not have any experience trying to phase align the subwoofers using impulse overlays and have not looked at this feature. is this an important thing I should do?

Thanks for any suggestions?
Have a good day
Kevin
 

warek

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Thanks, I have watched this video several times. Either I am missing something or is my result to be expected?
 

JStewart

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My concern is that when I then try and Eq the aligned response and import into the file into minidsp 2*4hd and measure the actual response is not close to the predicted response.
You'll need to overcome this first. With REW, the measured will be identical to predicted.
 

hemiutut

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Thanks, I have watched this video several times. Either I am missing something or is my result to be expected?
Are the 4 18" subwoofers placed in the best possible locations? I say this because between 15-20 Hz they should give more gain. You can always try another filter at 18 Hz with +8-9 dB for those frequencies. 4 18" subs is a lot, but for the rest I see a very coherent frequency response, normal with 4 well-optimized subwoofers
 

FargateOne

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My AV System  
Preamp, Processor or Receiver
Rotel RSX-1562
Additional Amp
Bryston 3B3 for fronts mains
Universal / Blu-ray / CD Player
Cambridge CXU
Front Speakers
B&W 804 D2
Center Channel Speaker
B&W HTM4D2
Surround Speakers
B&W 705
Subwoofers
SVS PC-2000 and SVS PC-2000 Pro
Other Speakers or Equipment
10 PEQ filters/channel in receiver with REW
Video Display Device
Samsung UN55ES8000
Other Equipment
miniDSP 2x4 HD
Hi all
I do not have any experience trying to phase align the subwoofers using impulse overlays and have not looked at this feature. is this an important thing I should do?

Thanks for any suggestions?
Have a good day
Kevin
I am hust an amteur, but with my 2 subs it appears that phase aligned them was the mos important part to get them play well together and @jtalden gave me so much help. Many info here among others:


 

warek

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Thanks for the links, I have made some progress and found more success with not using REW time alignment menu , instead I followed the you tube video home theatre gamer minidsp part 2 to set delays and phase. I then used REW to eq and produce file for export into the dsp.
latest results.jpg
 

warek

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Thanks for the replies and for looking at my posts. I will be on an extended holiday and will not be able to do any more with REW and Minidsp until October. Hope to get some more tips at that time and learn some more about REW
 
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