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Solving Bass Nulls with DSP or not ?

Andysu

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Sounds like a summer project :D
you , betcha it is . so get cracking at it for sub bass ASR sub bass science and beyond .
 

Willem

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Just get a measurement microphone and familiarize yourself with REW and measure what is actually happening in your real room. No need for another in this case physical simulation.
 
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atoprak

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Have almost no preference, experience about these microphones ?
What would you prefer.... It would be good If I can use the ame microphone when (again If) I buy a DSP later...
 

Willem

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The Umik-1 is more or less the default for many systems. It certainly is for REW. The probably best (and free) software to equalize multiple subwoofers is Multi Sub Optimizer(MSO). It presupposes REW measurements, and effectively a UMIK-1 with its calibration file. However, you could use others. Mind you, MSO is not easy, nor is REW, although the web is full of video tutorials.
An Antimode 8033 is a much easier but not nearly as good dsp eq unit. It does the job automatically, but cannot eq individual subs. It uses its own mic, so if you also want to make REW measurements you would still want to have a Umik-1. Fortunately the Umik-1 is not that expensive. To be honest, I believe that without it no serious attempt at good low frequency response is feasible.
 

Willem

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I am a quite frugal type myself, so I suggest to go step by step:
1 A Umik-1 calibrated microphone. Without getting the facts about current actual response it will be impossible to improve things. Move the one and only subwoofer around, and perhaps also the main speakers, to find out the best location. Cost about 80 pounds.
2 If that is not enough (it probably is not), get a second small subwoofer like the BK Gemini. Again measure response, and move both subs around for the best response. This will probably be quite a bit better. Cost 255 pounds.
3 Add Multi Sub Equalizer and MiniDsp 2x4 HD. Cost, another 200 pounds or so. This will be hard work, but the result wil be the best you can have. If you cannot face the idea, get an Antimode 8033, for a convenient solution that is really easy to implement, even if not quite as good as MSO.
 

FeddyLost

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First, what happens when I stand up right at my listening position. If I standup .. everything is fine... the bass changes like night & day ...
1) looks like bass null between floor and ceiling
2) different height also affect different configuration of floor and ceiling bounce

I mean in some cases, even If the overall sound is not that laud, I hear my kitchen window (almost 30ft away from the listening position )rattling or receive some complaint about the very low end noise from the ones at the first floor.
Looks like your sound insulation is not very good. In a framework house it's very often, as floor/ceiling is not massive enough to stop LF.

I'd try to measure what exactly is going on and then solve problems step by step with measurements "before and after".
 
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atoprak

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I just ordered Umik-1 to see what is going on in real.
When I got the product and the measurements, I will post them here and discuss how we can fix the problems or enhance the general sound and the the possible gains with an addition of DSP into my signal chain.
 

Willem

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I just found this interesting experiment by Brent Butterworth, comparing 4x8 inch subs, 2x12 inch subs and one 15 inch sub: https://www.soundandvision.com/content/subwoofers-4-2-or-1-0 The outcome is more or less as theory would predict, with a tradeoff between smoothness/definition on the one hand and extension on the other. It should be noted that this is a more than ten year old test, and small subwoofers have improved quite a bit, thanks to a combination of powerful amplifcation and dsp eq to bring up the low end. What was not tested but what is advocated by some people such as Earl Geddes, is one big subwoofer for deep extension combined with one or more small ones for smoothness.
 
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Willem

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And since you seem to be in the UK and already own a BK subwoofer, I notice BK have just introduced a successor to the 10 inch Gemini, with auto on/off: the P10-150 GEM.
 
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sonitus mirus

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Maybe you could temporarily set up the subwoofer at your listening position, and than take several measurements at various spots around the room. If the null is reduced at one of these locations, try placing the subwoofer in that spot, if possible and the placement is reasonable. It is not a perfect method, but it is better than trying to move the subwoofer all over the place and gets you fairly close to the same idea.
 
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atoprak

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And since you seem to be in the UK and already own a BK subwoofer, I notice BK have just introduced a successor to the 10 inch Gemini, with auto on/off: the P10-150 GEM.

Well, I actually living in Netherlands. I know the brand and almost order from the manufacturer but seen a second hand in NL and picked that one ... It was an experiment for me since (as I understand so far) I am working against the physics :) ..
 
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atoprak

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Well, thanks for all...
Since I have received Umik-1 and did some measurements, I will create another topic with them and looking for your advices.
 

mhardy6647

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Sometimes I wonder about my reading comprehension. I read "Bass nulls" in the title of this thread as Brass balls.
 

Flaesh

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I am trying to get some sensible positioning for the possible second sub ..
;)
1660173849541.png

Ref is front only
 

Steve Dallas

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I don't have time to read the thread, but I thought I would drop a few graphs. My home office is a cube. Here is its AMROC.

My desk chair position is at the rear 1/3 point, or 2/3 from the front wall if you prefer.

KEF R3 measurements with no subs and no correction and nulls clearly visible:

KEF R3 Left Uncorrected.png



KEF R3 Right Uncorrected.png



With DRC by Dirac Live Standalone and no subs:

KEF R3 Left Dirac to 1000Hz.png



KEF R3 Right Dirac to 1000Hz.png
 

FrantzM

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Hi

I haven't read all the replies in this thread, a few come out has extremely important foe the OP to read and re-read. In particular post #4 a from @Willem and post #5 from @DonH56 ... Their latter posts were as usual very informative. My own post will simply rehash what these people and others have said. ZIt bears repating.

However good your speakers are in the low bass, however extended and distortion-free, they could be in the bass. Oncein a room , many strange to and bad things can and usually happens. The bass response is a mess with peaks and nulls.. You can equalize the peaks but should't or can't EQ the nulls. These are as said earlier black holes : Null suck power for no results.
Conclusion: Don't try to EQ nulls.

What to do then? It is a mystery to me why this has not become the de-facto standard for audio enthusiasts? Use at least 2-subwoofers. 3 preferably. It is usually better to use 3 less expensive subwoofers than one superior for the same cash outlay.. Say, the audio enthusiast has a #1500.oo budget for bass? The best advice is to get, for the same budget a Umik-1 at $100.oo, a miniDSP 2 x 4 for $125 (The 2x4 HD is the better model but for bass purposes and most consumer subwoofers, expecting 1.0 volt input for full output, the 2x4 although limited, does work) , a $20.oo donation to REW although you could go ungrateful and download REW for free, a $20,oo donation ro MSO (Multiple Subwoofer Optimizer), although you could also go ungrateful ... an the balance about $1250, for 2, preferably 3 less expensive , likely smaller subs.. And they don't even have to be all the same ... It will take a while to get there and a lot of learning and a bit of frustration but the results are usually glorious.

Seriously. Bass require subwoofer. ideally subwoofers as in 2 or preferably 3. Regardless of the low end extension of your mains. You want to deal with peaks and/or nulls? Get a sub. Then get another , now with 2, you are getting there...3 ? with time and care in setup using REW, MSO with a miniDSP_ 2 x 4 HD? Heaven!

Peace.
 
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