Re: multiband xover

On Sun, February 10, 2013 3:49 am, John Rigg wrote:
> On Fri, Feb 08, 2013 at 11:52:06PM +0000, Steve Harris wrote:
>> On 8 Feb 2013, at 21:38, Patrick Shirkey wrote:
>> > On Sat, February 9, 2013 8:00 am, Steve Harris wrote:
>> >> The existing algorithm uses the FFT data, which makes a poor x-over -
>> I
>> >> can't remember exactly why, I think there might be ringing in the
>> freq
>> >> domain or something?
>> >>
>> >
>> > Do you think that might have been fixed with the switch to the
>> > Kaiser-Bessel window?
>>
>> It could yes, but I'm too rusty on exactly what that would do.
>
> I just tested 0.97.14 (Debian testing package) with a spectrum analyser.
> With noise input, soloing the compressor bands shows fairly wide,
> periodic,
> out-of band peaks about 90dB below the signal level. That's probably
> inaudible
> in a compressor, but might be a concern in a PA crossover.
>
> There's also some low level aliasing when compressing a constant-level
> sine wave. This is worst with short attack and release times, and depends
> on the amount of gain reduction. Raising the threshold well above the
> signal made it disappear, as did bypassing the band under test. At the
> worst
> settings I tried it was about 100dB below the signal level. This was with
> a
> 9kHz sine wave, 48kHz fs. By contrast, SC4 mono running as a plugin in
> ardour2 has a totally clean output with the same test signal.
>

The Kaiser-Bessel window algorithm was added in 0.97.16

If you have the 0.97.14 running then you will be able to compile the
latest cvs version for testing too.

just

sh autogen.sh
make
make install


--
Patrick Shirkey
Boost Hardware Ltd

------------------------------------------------------------------------------
Free Next-Gen Firewall Hardware Offer
Buy your Sophos next-gen firewall before the end March 2013 
and get the hardware for free! Learn more.
http://p.sf.net/sfu/sophos-d2d-feb