Noise from sub with miniDSP - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 20 Old 06-26-2018, 04:52 AM - Thread Starter
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Noise from sub with miniDSP

I have a 460HO and inuke3000DSP in a sealed enclosure. There is a very large dip at 35 hz and peak at 45 hz in my room via REW. Like +12/-12db. Funny thing is I don't remember such a peak and valley with my other subs...

So I used the inuke dsp to flatten out the response and it sounded ok. I have had a minidsp 2x4 for about a year and tried to use it once and put it back on the shelf. So I decided i am ready to use the minidsp instead and use it with my svs sb12nsd subs too.

I spent the whole day testing and tuning got a really nice flat response with all 3 subs. Throw in some test scenes and hear something that sounded like distortion or slight bottoming out at a certain frequency. I suspected that the boost at the 35hz was too much and over driving the driver. I used some test tones to narrow down the frequency it was happening at and confirmed my suspicion. I adjusted the dsp back to 0 and I was still getting the noise. I kept removing more adjustments to try to isolate where it as coming from to no avail.

I removed the minidsp and used the inuke dsp the noise is gone.

Do you guys have any suggestions or recommendations?
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post #2 of 20 Old 06-26-2018, 05:01 AM
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Quote:
Originally Posted by LGERIC View Post
I have a 460HO and inuke3000DSP in a sealed enclosure. There is a very large dip at 35 hz and peak at 45 hz in my room via REW. Like +12/-12db. Funny thing is I don't remember such a peak and valley with my other subs...

So I used the inuke dsp to flatten out the response and it sounded ok. I have had a minidsp 2x4 for about a year and tried to use it once and put it back on the shelf. So I decided i am ready to use the minidsp instead and use it with my svs sb12nsd subs too.

I spent the whole day testing and tuning got a really nice flat response with all 3 subs. Throw in some test scenes and hear something that sounded like distortion or slight bottoming out at a certain frequency. I suspected that the boost at the 35hz was too much and over driving the driver. I used some test tones to narrow down the frequency it was happening at and confirmed my suspicion. I adjusted the dsp back to 0 and I was still getting the noise. I kept removing more adjustments to try to isolate where it as coming from to no avail.

I removed the minidsp and used the inuke dsp the noise is gone.

Do you guys have any suggestions or recommendations?
Could be the input voltage for miniDSP over saturated. Try out RCA line attenuator (-6db) and check if that solve your problem.
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post #3 of 20 Old 06-26-2018, 05:02 AM
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Originally Posted by LGERIC View Post
I have a 460HO and inuke3000DSP in a sealed enclosure.

I guess that's one way to deal with the fan noise.


After removing all of the EQing, was the noise still isolated to a particular frequency? (or seem to be).
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post #4 of 20 Old 06-26-2018, 05:38 AM - Thread Starter
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The noise seemed to be isolated about 35 Hz. Which I had about +12 db to flatten out the dip. The strange thing was when I dropped it to zero the noise was still there.

I did not hear the same thing from the svs subs. They required very little peq.

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post #5 of 20 Old 06-26-2018, 05:49 AM
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Quote:
Originally Posted by LGERIC View Post
The noise seemed to be isolated about 35 Hz. Which I had about +12 db to flatten out the dip. The strange thing was when I dropped it to zero the noise was still there.

I did not hear the same thing from the svs subs. They required very little peq.

did you put a +12dB peak to flatten that out? If so, I wouldn't go higher than 6dB. You could do a cut for the rest of the frequencies to limit that dip and then run the gain higher on the amp.

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post #6 of 20 Old 06-26-2018, 12:28 PM
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Quote:
Originally Posted by LGERIC View Post
The noise seemed to be isolated about 35 Hz. Which I had about +12 db to flatten out the dip. The strange thing was when I dropped it to zero the noise was still there.

I did not hear the same thing from the svs subs. They required very little peq.


From everything I’ve read it’s better to reduce than gain when you have valleys so you don’t drive the amp too hard in one frequency.


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post #7 of 20 Old 06-26-2018, 02:00 PM - Thread Starter
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I think what I might try next is to import a file from REW and see what happens. I was just manually making adjustments to flatten the response.
I attached a pic of the final with all 3 subs after audyssey. I don't have access to any files right now.
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post #8 of 20 Old 06-26-2018, 04:10 PM
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Quote:
Originally Posted by LGERIC View Post
I think what I might try next is to import a file from REW and see what happens. I was just manually making adjustments to flatten the response.
I attached a pic of the final with all 3 subs after audyssey. I don't have access to any files right now.
The picture wont load for me
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post #9 of 20 Old 06-26-2018, 04:18 PM
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Is it possible that you have a filter enabled in the MiniDSP you aren't seeing? Something like a filter on the input and you're looking at the output filters thinking they are all turned off?

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post #10 of 20 Old 06-26-2018, 04:56 PM
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Could you try one of your other subs without the minidsp?
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post #11 of 20 Old 06-26-2018, 06:30 PM
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12db of boost isn't a good idea. Did you take a bunch of measurements in and around the listing position to verify the dips are everywhere?
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post #12 of 20 Old 06-27-2018, 11:55 AM - Thread Starter
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No I didn't take multiple measurements. But I did get the same results on 2 separate days of measuring. I am confident enough that the mic. is close enough to the same spot for my taste. I am going to put one of the other subs in the same place to see if I get the same response. I am also going to reset the minidsp completely and try it hooked up with no filters to see if I there is any changes.

Is it safe to assume I should expect no change in the graph with or without it hooked up and all settings to default?

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post #13 of 20 Old 06-27-2018, 08:29 PM
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Quote:
Originally Posted by LGERIC View Post
I removed the minidsp and used the inuke dsp the noise is gone.
Do you guys have any suggestions or recommendations?
It's likely that you never removed the filter IMO. You can attenuate the 35Hz at -6dB to verify this. 12dB of boost requires a lot of headroom from your signal chain, amplifier and driver. For example, many new AVR's on the market output 1.2Vrms from the sub out. This is ~1.7V peak. If you boost that by 12dB it would need to go up to ~6.8V peak. The mini can't output that much voltage so it will send a clipped signal to your sub amp.

Another thing that can be happening is that your signal to the input of the mini is too high and clipping the unit. If you're running a sealed sub there is no advantage whatsoever to put the mini in your signal chain. It will only add rolloff to your signal down low and take away from ULF. My advise is to only use the mini for your other subs not inline with the NU3000DSP. You can also flatten the NU3k's response to 10Hz on top of eliminating the low end rolloff from the mini to maximize low end response.

Also, your crossover area looks bad. It's likely that you aren't aware of the phase issue with the nukes. If memory serves, if you're bridging the output of a 3k, you'll need to flip the polarity of the leads to the sub or reverse the phase in the DSP section.
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post #14 of 20 Old 06-28-2018, 03:31 AM - Thread Starter
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Thanks for the input. You are absolutely right I don't NEED the mini for the inuke. I was just trying to simplify things. But hey if it ain't gonna work then I won't add it to the inuke and just try it for the SVS subs only.

I have seen in the past how to lower filters in the inuke. I never really thought I would need it. I will check into that.

I havn't looked into the phase yet. Should i do this first? I know about the distance tweak for the crossover region. I wanted to get the subs dialed in before moving on to something else. Is there a best practice to check the phase with the other subs in REW? I have always just done it by ear in the past.

Unfortunately I don't have a lot of time to play with this stuff especially with the kids being out of school for the summer. I hope to gain some more knowledge and have a plan before jumping back in.

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Last edited by LGERIC; 06-28-2018 at 03:42 AM.
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post #15 of 20 Old 06-28-2018, 03:59 AM
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My understanding is that the polaity of the output from the inukes is reversed and you either need to change the polarity in the inuke's setup or just reverse the leads to the sub.


I have to ask though, what is the distance tweak? Change the distance for the sub in the AVR until the phase of the sub matches up with the bottom end (at the crossover frequency) of the mains?
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post #16 of 20 Old 06-28-2018, 07:22 AM
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I have to ask though, what is the distance tweak? Change the distance for the sub in the AVR until the phase of the sub matches up with the bottom end (at the crossover frequency) of the mains?
Basically, you use that tweak to ensure that your sub(s)/mains are constructively combining throughout the crossover range. mtg90 has an awesome write-up on it here. Third post on that page goes into a lot of detail on the subject.
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post #17 of 20 Old 06-28-2018, 11:52 AM
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Basically, you use that tweak to ensure that your sub(s)/mains are constructively combining throughout the crossover range. mtg90 has an awesome write-up on it here. Third post on that page goes into a lot of detail on the subject.

Woah, awesome. Thank you.
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post #18 of 20 Old 06-28-2018, 09:15 PM
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Originally Posted by LGERIC View Post
I havn't looked into the phase yet. Should i do this first?

Is there a best practice to check the phase with the other subs in REW? I have always just done it by ear in the past.
You don't have to do it by ear now that you have a measurement mic and REW. With only your nuke sub: set distance to what it really is in feet/meters and do a sweep. Then reverse polarity and do another sweep. The sweep that shows the most output at the crossover region is correct. Tweak distance from there.

When you add any other subs to the equation if at the same levels they subract from the sub bandwidth's SPL then the new subs are out of phase. Reverse polarity on them and it should add to the SPL.

Here is a polarity test that you can do if you are still unsure or want to double check.
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post #19 of 20 Old 07-03-2018, 07:51 PM - Thread Starter
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So I finally had a chance to play with this again. These are the results. I'm sorry I dont have the patience to fgure out how to upload the actual files. Here is a pic of the final fr. No noises. removed the mini dsp. Only using the inuke dsp. I used the hps because it was seriously flat to 10hz. and it was sounding funny at the really low scenes.

As it looks right now it is sounding better. I will play around with it or some more to see if I can get it any flatter. Thanks to everyone who gave me advice.
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post #20 of 20 Old 07-04-2018, 06:10 AM
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As others have mentioned, it's very likely the MiniDSP was being overdriven at the input. I have a bunch of them, being used in cars, small active home speaker systems, and until about 6 months ago, my HT. I've only experienced an issue with the HT subs, and during loud bass passages the sub drivers would often make a "click" type of sound...similar to a driver bottoming out, but not exactly. Right around last Christmas, I replaced the MiniDSPs in the HT with a BiAmp TesiraServer, and haven't experienced the same noise. Granted, this isn't a very scientific approach to troubleshooting said noise, but it did lead me to believe the MiniDSP was the culprit. With that said, I have no qualms with MiniDSP products. They're a fantastic cost/feature/functionality product, when used correctly.

Also, bumping any EQ to +12 is asking for trouble. The true, proper way to use an EQ is to cut only, but of course, we all use them to bump things into line, anyway. If adding gain with an EQ, it should really be limited to +3, maybe +6 in extreme situations. Anything beyond that is demanding a ridiculous amount of more power from the amplifier at those frequencies, and is likely to add distortion and heat in both the driver, and amplifier. Huge dips in response are usually room related, if the driver and enclosure are chosen and built correctly. The real fix to those issues is placement in the room, as difficult as that may be in most people's homes. For example, if I moved my seating position 2' forward, I'd be in bass heaven, but my room is small, and moving the couch is not an option for me. Trial and error with placing the subs helped, and adding additional subs to fill the dip also helped, a lot.
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