DIY DSP Solutions

Max Warasila

Graduate
Feb 20, 2013
1,157
49
48
Richmond, VA
MiniDSP is great, but it doesn't provide a great solution for pro audo loudspeaker applications. Does anyone have a good solution for a FIR capable DSP with balanced line level I/O?

Thanks.
 

Linas Martinenas

New member
Dec 5, 2019
2
0
1
Santa Clarita
I have got the BSS London BLU-16 of off the ebay for $260 and tax, and the extra output card for arroud a hundred. Not diy but not that much more than minidsphd plus the rack drawer, balanced to unbalanced converters and the converters other way if to buy all that stuf. Also blu has less limitations on fir taps usage. Bss audio architect does accept .csv export from popular software packages. I don't have four ways system, so I did set Vrx932la plus a sub for a test as a three way. Got pretty decent impulse response. Phase is within 40 deg down to 100 Hz and within +/- 7 deg from 300 to 20k, not too terrible for the first try. Crossovers are 96 lr at 1k and acoustic lr 24 at 85 Hz for sub, with some iir flattening before fir filters.
Just to see the DSP usage i added another pair of ways to make it into four ways.
The blu16 now is set with three inputs and eight outputs. Each of the mains consist of input gain, delay and system eq set all as stereo pair, the super high channel with another parametric eq , delay, fir filter, limiter, gain. Highs are similar, but uses bss crossover set as high pass lr 24 at 800 hz to clean up the low end of the fir. The crossover also includes delay and gain controls. The lows uses parametric eq down low, linear phase lr96 fir on top and the stereo crossover at 85 hz. Driver time allignment is implemented as a delay inside the crossover block.
Input 3 is for aux fed subs and feeds two of the otputs with delay between them to set the radiation pattern. It also features shared gain control with mains, parametric eq, and the crossover with subsonic filter and limiters.
The limiters are of two stage variety, suposedly peak and rms but bss is little unclear on to which of the stages the controls belong to.
My Fir filters have 820 taps at 1 khz crossover and 320 taps at 3 khz (not in use with vrx), to keep overal delay under 10 ms. Maximum of 6700 fir taps can be specified , I don't know if per filter or total.
All of this did put DSP utilisation to 80% or so.
Access to the unit is over the wired ethernet, but wifi via router works just fine.

Hope this helps some...
 

Peter Morris

Senior
May 8, 2011
1,009
98
48
Australia
As a crossover / processor absolutely. I think I'm getting even better results (y) :) (y)

The Lake may still has advantages in terms of being a system tool with its groups, Mesa EQ and its easy to use brick wall filters etc.
 

Max Warasila

Graduate
Feb 20, 2013
1,157
49
48
Richmond, VA
The linea-research devices are top of the line. I had a brief chance to talk with Ben Ver at NAMM this year, but he got a call from his wife (I think?) and I never got back around to his booth. It's got almost every feature I'd like, especially if you go with the full amplification solution. Only problem is the price tag it comes with! I do agree with Peter regarding the lake as a better system-tech tool, even though the linea-research stuff has better loudspeaker optimization tools specifically. IIRC, it has a decent API though, so it might be possible to do whatever you want on top of it depending on the scale you're looking at.

However, I'm really looking into doing some more low-level work, so even though these are amazingly good tools, they still aren't what I'm looking for. I may just have to pony up for the full SHARC and make my own balanced input daughter board.
 

Jim dee

Freshman
Jul 12, 2015
32
3
8
New Zealand.
As a crossover / processor absolutely. I think I'm getting even better results (y) :) (y)

The Lake may still has advantages in terms of being a system tool with its groups, Mesa EQ and its easy to use brick wall filters etc.
So they have all the features required make perfect settings for the your PM boxes.

Do they not have brick wall filters?

You say system tool.... What thing is it missing compared to the lake?

I'm taking it that you'd recommend it over the lake for most users?

I ask I'm using an xta 448 and getting nice results with out delving into FIR
which I will do soon or later but at the same time if there better new stuff going around then I like the idea of keep ahead of the options on the market
 

Peter Morris

Senior
May 8, 2011
1,009
98
48
Australia
The advantage of the Lake was its ability to do linear phase crossovers, both brick wall and a FIR LR 24dB/Oct slope. To my ear things with a flat phase response sound more real.

The PM 90/60 works best with the 24 dB slopes to maintain vertical pattern control as narrowing low frequency band is merged with the widening HF band at the crossover point.

The ASC48 will do a new LIM 24 dB/Oct linear phase crossover with less issues than the Lake FIR simulation and you can overlap the bands if needed. The latency associated with this approach can also be less and you can cross to the subs with a linear phase crossover and have a latency less than 15ms .... which I think is about the maximum for many small applications. Here is some info on this approach ...

http://linea-research.co.uk/wp-cont...Tech Docs/CrossoverFilters White Paper -C.pdf

The thing that is great with the Lake is it EQ page … almost unlimited filters of any shape you want.

You can see some of them on this video

In terms of price it cost me about half what a Lake would cost and it is 4 way stereo which requires 2 x Lake LM26’s.

I bought mine for Audio Bands Australia - http://www.audiobrands.com.au/ Don and his team are great 😊
 

Moritz Bachmann

New member
Nov 7, 2019
10
1
3
24
Austria
have you heard about the Aurora DSP?
It started as a DYI project and they implement a lot of features the users come up with.
I think I will give it a try, because it is cheap anyway. If I it doesn't fit my needs, I will use it for my livingroom.
What do you guys think about it?

 

Linas Martinenas

New member
Dec 5, 2019
2
0
1
Santa Clarita
Surely that Lake video on EQ looks impressive...
But I think BSS London Blu is still more of the pro solution if we are comparing to minidsp implementations , at comparable price if buying iit used. Here is the screenshot of Audioarchitect with my little Blu-16 loaded to 97% of dsp capacity. Four 960 tap fir filters and two of 300 taps.

Audio Architect 3ways with Sub.png

All of the controls shown functions live over WiFi . Eq bands are only of shelf or "bell" variety but fully parametric, graphically or by typing. However there is no front panel access at all since it's an installation product. But to load a different fir filter the AA session has to be disconnected, and then unit reloaded with the update. No level shifts or pops or pauses in the audio while performing this though. Connectors are of the Phoenix variety.
Here is the example of VRX932:
Spl, phase and impulse response, passive and biamped with 820 tap fir 48db/oct crossover at 1 khz.

SPL_PHASE_DRIVERS_VRX932LA.pngSPL_VRX932LA.png
Impulse_Resp_vrx932_biamp_fir_1k.pngImpulse_Resp_vrx932_passive.png
 

David Westom

Freshman
Mar 19, 2017
7
0
1
MiniDSP is great, but it doesn't provide a great solution for pro audo loudspeaker applications. Does anyone have a good solution for a FIR capable DSP with balanced line level I/O?

Thanks.
There is also the DRAC-88 series which use the miniSHARK module for FIR processing, its 8 in 8 out both balanced and unbalanced.