Combining Virtual Bass Array and Alternative to VBA Pre-filters

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Ecwl
Posts: 43
Joined: 19 Feb 2021 01:05

Combining Virtual Bass Array and Alternative to VBA Pre-filters

Post by Ecwl » 15 Dec 2021 04:41

So even though many people have had great results using the Alternative to VBA pre-filters alone, I have always found in my system, that the Virtual Bass Array pre-filters sound better. This is regardless of where I set the cut-off amplitude for the Alternative to VBA pre-filters.

I finally did some more extensive listening to test as to what the issues were and what I found was that with VBA, it really addresses my primary longitudinal resonance frequency really well. If I were to use Alternative to VBA pre-filters, what would happen is that I can set the cut-off amplitude very low (and 1-2dB above final target) in which case the primary longitudinal resonance frequency still resonates but the bass also sounds slightly too anemic. But if I set the cut-off amplitude a little higher above the final target (e.g. 10dB), I actually no longer get anemic bass and the non-primary longitudinal resonance bass peaks do sound better but the primary longitudinal resonance frequency peak would resonate even more. And since the dominant resonance in the room is the longitudinal frequency, the VBA pre-filter always sounds better.

After thinking about it for a while, I realized I can create an Alternative to VBA pre-filter after the VBA pre-filter so that the VBA pre-filter would address the primary longitudinal resonance frequency and and the additional Alternative to VBA pre-filter would address the other bass peaks but less aggressively.

The process is more tedious because first I have to convolute Pulse48L & Pulse48R with the VBA pre-filters first in order to create the Alternative to VBA pre-filter. Moreover, I ended up setting the cutoff amplitude for the Alternative to VBA pre-filter at about 5dB above the target amplitude as I did not want excessive bass peak removal from the pre-filter.

It's getting late in the evening so I probably won't be able to do further extensive testing tonight. But it seems the combination of properly constructed VBA prefilters and additional Alternative to VBA prefilters did achieve better bass response than either approaches alone.

I think this is perhaps pretty esoteric. Moreover, I'm not sure if I have optimally set the cutoff amplitude of the Alternative to VBA prefilters yet. But I thought I would mention this approach to people in case they are interested in trying it.
Ecwl
Posts: 43
Joined: 19 Feb 2021 01:05

Re: Combining Virtual Bass Array and Alternative to VBA Pre-filters

Post by Ecwl » 17 Dec 2021 18:20

I just noticed that adding an Alternative to VBA broad bass peaks pre-filter actually increases the RT60. I was wondering if Uli can explain why that is.

Fortunately, the increase in RT60 didn't seem to affect the sound significantly enough in my system and the benefits of the Alternative to VBA filter seems to be worth the compromise.

In the end, after quite a bit of experimentation, I'm currently using a VBA pre-filter to reduce my primary longitudinal room resonance (that a simple Alternative to VBA broad bass peaks pre-filter alone could not adequately take care of) and then I create an Alternative to VBA pre-filter to take care of the remaining bass peaks <200Hz. By setting the Alternative to VBA pre-filter at about 2dB above the target frequency response, the combination of these two pre-filters seems to give my system the best sound I can achieve so far.

I'm really appreciating that all these filters and settings are about what compromises I want to live with. I think if people find that the Alternative to VBA pre-filter is not adequately addressing their primary longitudinal room mode resonance, they may want to try what I'm doing by combining a VBA pre-filter with a new Alternative to VBA pre-filter. On the other hand, I can see how in some systems, the Alternative to VBA pre-filter might increase the RT60 to an unacceptable level so they would have to rely on no pre-filter or just the VBA pre-filter.
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