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Maximizing effect of DSP in 5.1 setup

digipete, modified 10 Years ago.

Maximizing effect of DSP in 5.1 setup

Padawan Posts: 99 Join Date: 6/18/11 Recent Posts
I have the most awesome Genelec 5.1 setup:

3 x 8260A
2 x 8250A
1 x 7271A

I have the setup in my living room and it is way too small, untreated with way too much windows. :cry:
I need all the DSP help I can get (apart from fitting as much treatment as will fit).

Is there any way to force the 8260 and 8250's to use their DSP powers only above the chosen SUB X-over freq. - say 85hz? :?

And hey - thanks for making such great equipment. :D
ilkka-rissanen, modified 10 Years ago.

Re: Maximizing effect of DSP in 5.1 setup

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Hey,

Wow, that's a sweet setup for sure! 8-)

Unfortunately it is not possible to force AutoCal to set filters only above certain frequency, and there is a clear reason for that. It is essential to make the whole frequency response flat even though there is a subwoofer in the system because it ensures a proper summation of the signals (speakers + subwoofer). The crossover filters aren't ultimately steep but they have a certain slope instead, for example 12 dB/octave, so if you have a strong room mode for example at 50 Hz and you wouldn't filter it out from the main channels, it would show up in the sum frequency response because the crossover filter couldn't filter it out before summing up to the subwoofer. The closer the crossover frequency you are (say ~40 - 85 Hz range) and the stronger the room modes are, the more important it is that the modes are filtered out.

The only way to play with the filters is to do it manually. If you feel that you would need more filters above the crossover range (a very rare case!), you could manually assign for example only one filter with high attenuation value and low Q value for the sub 85 Hz range and leave the rest for above. But I don't recall a single case where this kind of "trick" would have resulted in any better (subjective) end result than the AutoCal calibration.

Would it be possible to send screen captures of the Interactive Response Editor window (where you can see the measured and corrected frequency response) for all speakers and subwoofer? You can post the pictures here or send them to my private email.

Thank you!
digipete, modified 5 Years ago.

Re: Maximizing effect of DSP in 5.1 setup

Padawan Posts: 99 Join Date: 6/18/11 Recent Posts
Hey Ilkka, thanks for your informative answer.

I have covered most of the rear wall with LP's and books, and that helped a bit.
Significant room treatment unfortunately has to wait for various reasons

I have a dip of 6dB @ 120hz, probably due to the room size (4,5 x 4,5 x 2,5m).
I include the Interactive Response Editor window for the left front speaker where the dip is large.
I include the rest for good measure ;)

Any recommendations?
digipete, modified 5 Years ago.

Re: Maximizing effect of DSP in 5.1 setup

Padawan Posts: 99 Join Date: 6/18/11 Recent Posts
Screen capture continued . . .
ilkka-rissanen, modified 10 Years ago.

Re: Maximizing effect of DSP in 5.1 setup

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Hi,

Based on the screen shots, it looks like AutoCal is doing excellent job in smoothing out your frequency response. I am now sort of baffled when it comes to your original question: what kind of extra DSP power do you require? The small bumps in the mid range can't and shouldn't be fixed with electrical filtering but acoustical treatment instead.
digipete, modified 10 Years ago.

Re: Maximizing effect of DSP in 5.1 setup

Padawan Posts: 99 Join Date: 6/18/11 Recent Posts
Hi Ilkka

I agree, AutoCal is great, and everything sounds really good.

I was looking to to fix the 7dB dip at 120hz on the front left, that's all.

I'll wait till I can treat the room more and see how it goes then.

Thanks

DigiPete
ilkka-rissanen, modified 10 Years ago.

Re: Maximizing effect of DSP in 5.1 setup

Yoda Posts: 2564 Join Date: 3/23/09 Recent Posts
Hi Pete,

Unfortunately no DSP can't and shouldn't fix room mode dips because they are caused by acoustic cancellations and boosting them will just eat headroom out of the system and on top of that won't even sound any better. So acoustic treatment is the only way to go forward here. Luckily I can comfort you by saying that the dip doesn't look that bad: it's only 5 dB deep and less than half octave wide. I have seen much much worse in many so-called professional rooms. :)