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Solving Bass Nulls with DSP or not ?

levimax

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Some interesting comments. I stumbled here after fighting my own demons (bass nulls). I have a massive dip (measured) in my room at/around LP from 70-95 Hz. Since I can't fill these with eq, and moving speakers/position is not an option - the only solution seems to be adding sub(s).

Question is, if the null starts at 70Hz & most subs have LF cut offs at 60-80 Hz - how would adding sub/subs help (assuming 90% of the frequency they'd produce is below my null?). Any informed comments would be most appreciated.
It does work out, I can't 100% explain physics but I believe with multiple sources for same frequency you will often get reinforcement from one location to offset nulls from another. In any case see below, 2 subs added with LR4 80 Hz crossover and 100 Hz null filled in (orange is original blue is after 2 subs added).

before after Subs.jpg
 

Audiofool1Q84

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It does work out, I can't 100% explain physics but I believe with multiple sources for same frequency you will often get reinforcement from one location to offset nulls from another. In any case see below, 2 subs added with LR4 80 Hz crossover and 100 Hz null filled in (orange is original blue is after 2 subs added).

View attachment 251115
These are great results! I don't have the luxury of adding 2 subs but adding one should help I suppose. Interestingly, the null significantly reduces if I stand up & listen - my hypothesis is that changing speaker height may also help at least move my nulls further up the frequency range. Onward ho then..
 

levimax

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These are great results! I don't have the luxury of adding 2 subs but adding one should help I suppose. Interestingly, the null significantly reduces if I stand up & listen - my hypothesis is that changing speaker height may also help at least move my nulls further up the frequency range. Onward ho then..
See attached I got from another member here that was very helpful for me adding two subs. Moving thing around makes a big difference. I used MMM / RTA "live" while I moved thing around and it made a big difference just moving the subs several inches. I ended up with the 2 subs on the side of the LP as suggested. Good luck.
 

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FeddyLost

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Question is, if the null starts at 70Hz & most subs have LF cut offs at 60-80 Hz - how would adding sub/subs help (assuming 90% of the frequency they'd produce is below my null?)
First, you'd better define the reason for this null at least with REW RoomSim and see if adding the sub will help at all.
In fact, if you have mic and something like DSP for manual correction, most probably you'll be able to make 2.1 with steep crossover maybe up to 100 Hz (if your sub is located not in front of you).
If you will use shallow slope, you'll have too much midbass sound from subwoofer and it will localize itself.
Or you'll need to get subwoofer with possibility to use high order crossover.

Without more details I can't recommend anything more specific.
 

Dumdum

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First, you'd better define the reason for this null at least with REW RoomSim and see if adding the sub will help at all.
In fact, if you have mic and something like DSP for manual correction, most probably you'll be able to make 2.1 with steep crossover maybe up to 100 Hz (if your sub is located not in front of you).
If you will use shallow slope, you'll have too much midbass sound from subwoofer and it will localize itself.
Or you'll need to get subwoofer with possibility to use high order crossover.

Without more details I can't recommend anything more specific.
In my car I play under seats to 170 and cannot localise the midbass drivers, and they pan around the stage with the midrange very nicely, it’s all about phase integration, if you hear then at 100hz to 150hz it’s certainly phase and level integration and not the crossover point

Also if you have phase issues (from standing waves and reflections) at the crossover point ie 80hz in this case then move the crossover further away from it, the phase is not great where the null is, and crossovers depend on phase being good through the crossover region

Smaart (any version, I have V7, di2 and V9 now) is a massive help for speeding up setup times for dsp controlled cars and houses both
 

FeddyLost

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In my car I play under seats to 170 and cannot localise the midbass drivers, and they pan around the stage with the midrange very nicely, it’s all about phase integration, if you hear then at 100hz to 150hz it’s certainly phase and level integration and not the crossover point
If one have shallow crossover slope like 12 Db/oct and have some front-faced subwoofer aimed directly on LP, something higher than 80 Hz is not recommended.
If you have 4th order and floor-firing sub, it's entirely different case, so it depends.
 

Dumdum

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If one have shallow crossover slope like 12 Db/oct and have some front-faced subwoofer aimed directly on LP, something higher than 80 Hz is not recommended.
If you have 4th order and floor-firing sub, it's entirely different case, so it depends.
Use 24db slopes, it’s the best way to avoid nulls in crossover regions and it works perfectly… my subs are in the centre of my windscreen (I suffer nulls a lot in a car) and at no point sound like they are behind me
 

Audiofool1Q84

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Thanks @FeddyLost & @Dumdum - a lot of what you've suggested unfortunately goes a bit beyond my current understanding and resources. I have some more reading to do I guess when time permits & then revisit your suggestions. Thanks again.
 
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