Adding a third sub to cancel "Deep Mid-Bass Null"

[sigbergaudio]

Well, I didn't get REW working on the laptop, so I'm back to walking back and forth between the computer and subs. I've tried to find a place that would be acceptable to the wife, but no luck, so I still have my null. Not only that, but I must have moved those subs all over the room and still the null absorbs all the bass amplitude; when I increase it too much the subs go into clipping and distortion. Also, when I moved the subs, I played ARC’s distance setting thinking it would change the timing and still nothing; I don't think ARC's distance setting changes anything. In fact, when I move the subs to some areas, the null frequency changes; it feels like I'm chasing my tail.

I please need help with my next move.

The plan would be to get a DSP so would I be ok with the included room correction software or should I go for better software like "Acourate"(more taps) If I cannot get the null corrected, then I would try a 3rd sub.

Which DSP would best suit the plan?
Should I go for the better software?
Can I use a cheaper, smaller sub?

I do realize this is going to cost a learning curve, time and money: I just want the subs to work properly. I don't want to fail because I didn't spend extra $$$$.

Thank you for your time.

You will not be able to fix the null with DSP I am afraid. If you're not able to find placement alternatives where the null is removed, you will have to live with it.

 

[NTK]

You will not be able to fix the null with DSP I am afraid. If you're not able to find placement alternatives where the null is removed, you will have to live with it.

That is not totally true. If you do it correctly, which I must say may not be an easy feat, you can turn a sub into an "active bass trap".

For example, this concept is what enables double bass arrays (DBA) to work. The subs at the rear wall act as active absorbers, which has the effect of "removing" the rear wall and turn the place (works best with a rectangular room) into an endless rectangular tube. DBA can, with varying degrees of effectiveness, remove all room modes.

 

[sigbergaudio]

That is not totally true. If you do it correctly, which I must say may not be an easy feat, you can turn a sub into an "active bass trap".

For example, this concept is what enables double bass arrays (DBA) to work. The subs at the rear wall act as active absorbers, which has the effect of "removing" the rear wall and turn the place (works best with a rectangular room) into an endless rectangular tube. DBA can, with varying degrees of effectiveness, remove all room modes.

Well, as far as I have understood, a DBA is not on the table. We are in a situation with three subwoofers, and he has so far not found a location where they don't excite the null. So while this continues to be the case, I would suspect DSP will not resolve the issue at hand.

 

[NTK]

Well, as far as I have understood, a DBA is not on the table. We are in a situation with three subwoofers, and he has so far not found a location where they don't excite the null. So while this continues to be the case, I would suspect DSP will not resolve the issue at hand.

I'm using the case of DBA only to illustrate the concept. With the correct DSP, a sub place next to a wall can significantly alter how the wall reflects sound, which is in effect "altering the room geometry" with respect to the sound waves bouncing around in the room.

[Edit] Another example of DSP is turning 2 stacked subs into a cardioid sub.

 

[sigbergaudio]

Are you suggesting this to be a way forward in the situation this thread is about?

 

[NTK]

Are you suggesting this to be a way forward in the situation this thread is about?

IMO, using a third sub with DSP is certainly a possible solution to the problem posed in the thread title.

 

[Keith_W]

Well, I didn't get REW working on the laptop,

I am sorry I missed your earlier message. You HAVE to get REW working before you consider any DSP package. If you can't get REW to work, then none of the DSP packages would work either. There is no DSP package on the market that has magical properties that will make them work if REW doesn't work. If anything, all of them are more restrictive in terms of measurement layout.

In post #54 you said you tried ASIO4ALL, FlexASIO, and Java. None of these will work, I suggested VB Matrix specifically for a very good reason - it is the only software that is able to take two DAC's and report them as a single multichannel DAC. Read this post again. I am happy to help you get it working. Start by listing what DAC's you own, what microphone, and how you are connecting your DAC's to your amps/speakers.

If that is too hard, then the next purchase should be a multichannel interface with as many DAC channels as you need. Since it appears you need 4 channels, I suggest the RME Babyface Pro or Motu M4. If you are considering a third sub, you will need 5 channels - so look for a 6 channel DAC.

Once you get REW working, then we can talk about different software packages.

 

[Richx200]

The sub doesn't care about the couch.

I still have a problem with the middle of the floor

Well, as far as I have understood, a DBA is not on the table. We are in a situation with three subwoofers, and he has so far not found a location where they don't excite the null. So while this continues to be the case, I would suspect DSP will not resolve the issue at hand.

I have only two subs at this time, trying to avoid buying another

 

[Richx200]

I am sorry I missed your earlier message. You HAVE to get REW working before you consider any DSP package. If you can't get REW to work, then none of the DSP packages would work either. There is no DSP package on the market that has magical properties that will make them work if REW doesn't work. If anything, all of them are more restrictive in terms of measurement layout.

In post #54 you said you tried ASIO4ALL, FlexASIO, and Java. None of these will work, I suggested VB Matrix specifically for a very good reason - it is the only software that is able to take two DAC's and report them as a single multichannel DAC. Read this post again. I am happy to help you get it working. Start by listing what DAC's you own, what microphone, and how you are connecting your DAC's to your amps/speakers.

If that is too hard, then the next purchase should be a multichannel interface with as many DAC channels as you need. Since it appears you need 4 channels, I suggest the RME Babyface Pro or Motu M4. If you are considering a third sub, you will need 5 channels - so look for a 6 channel DAC.

Once you get REW working, then we can talk about different software packages.

Sorry for the misunderstanding. The computer I couldn't get REW to work on was the laptop I bought, so I wouldn't have to walk to the other end of the house each time to check REW on the desktop (runs REW fine). Also, wife not happy about wires on the floor.

I did try to get the VB Matrix going, but had trouble with the timings, they didn't look right and confusing.

I have two DACs Matrix Elemental I and a Topping D70 Pro Sabre, Mic UMM-6. A Zidoo Z10 Pro streams music to the Topping via USB, analog out to (two RCA) to Anthem MRX 1140 analog in, both subs connected to the 1140s sub preamp out to each SVS SB4000 LEF in. For movies, Nvidia Shield TV Pro and Panasonic DP-UB820 HDMI out to 1140s HDMI in. The speakers are arranged with surround, back and ceiling powered by the Anthem MRX 1140. The fronts are1140 preamp out to an Anthem PVA-7.

I do have a Korg DS-DAC-10R interface (attached manual)

I am trying not to buy another sub, (wife aggro) although I think it would be easier to fix the null with it.

 

[Keith_W]

Well there is your solution then. Run the cables on the floor and tell your wife that it will stay there for one day. Run all the REW measurements you need, then feed the results into MSO. Load the filters into the PC and take a verification measurement. If you are happy with the result, you now have your filters and you can rest easy knowing that you will not need a third sub. Then your remaining problem is to figure out how to insert the filters into your playback chain.

It is unusual that the laptop you bought can't run REW. I did not think the hardware requirements were that high.

 

[Flaesh]

Wouldn't the couch block the sub?

It depends. It works better without a sofa than with a sofa. The location of the sofa may matter more (yeah, lol). Some distance from the transdusers is required to form a plain wave. See link in signature and https://www.audiosciencereview.com/...of-the-double-bass-array-configuration.37943/

 

[Richx200]

Well there is your solution then. Run the cables on the floor and tell your wife that it will stay there for one day. Run all the REW measurements you need, then feed the results into MSO. Load the filters into the PC and take a verification measurement. If you are happy with the result, you now have your filters and you can rest easy knowing that you will not need a third sub. Then your remaining problem is to figure out how to insert the filters into your playback chain.

It is unusual that the laptop you bought can't run REW. I did not think the hardware requirements were that high.

I had run REW and moved the speakers a number of times, the problem is that the problem frequencies are requiring 25-40dbs to correct. Also, REW does allow for a test run with the calculated filters; assuming a plus 30-40db on the problem frequency. After I run ARC Genesis, I have maybe10dbs on the 1140 and 5-10dbs on the SVS. When I max out the bass; as per REW's filters it will either have no change and no bass or clipping, and it gets sloppy.

SVS does provide a PEQ in each sub that allows adjustments for 3 filters +-6 dB and bandwidth for each filter. Even after using SVS, I cannot correct the null.

If I could work out the filters and timing, I would need a DSP and maybe software to get them into the system.

The wife is cool with the wires for now

 

[Keith_W]

Your reply did not indicate that you tried MSO. What is the result with MSO?

 

[Richx200]

Your reply did not indicate that you tried MSO. What is the result with MSO?

Since most of MSO instructions use the MiniDsp for demonstrations; I ordered a MiniDSP Flex 2x4. When it arrives, I'll continue moving around the speakers and taking measurements. I'll try to get the placement, EQ and timing right.

I'll let you know how it works out