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#1 Budget DSP Options

Posted: Sun Dec 12, 2021 10:36 am
by Ray P
As I'm new to DSP I thought this might be the best place to post this.

The context is that I'm working on an open baffle project. I am planning on rolling off the bottom-end of the 'full-range' units at about 150Hz by bandwidth limiting the amps that will drive them.

I need the integrate the bass units, with the design suggesting a -3dB point at 80Hz and needing some low-end lift. To power the bass units I have a 100WPC (8ohms) Class D stereo amp. I think, at least inially, the obvious way to approach the integration of the bass units is with a DSP solution.

I posted a 'WTB' listing for a MiniDSP 2X4 unit but on turning over some stones found two more possible candidates, both cheaper than the MiniDSP (not that the small cost differential is really a factor for me at this budget point)

The first is this one;

https://www.thomann.de/gb/the_t.racks_dsp_4x4_mini.htm

which seems to be generally similar to the MiniDSP (2 extra inputs, but I don't need them) and with, perhaps, a better ADC/DAC chipset(?) but seemingly clunkier, but usable, software.

The second is this one, which is specifically for subwoofer integration;

https://www.soundimports.eu/en/dayton-audio-dsp-lf.html

It looks to only be configurable via a smartphone app.

One assumption I have made is that the 48KHz sampling rate of all these solutions isn't something that has much bearing at these low frequencies.

Just wondering if anyone can offer any experiences or advice?

Depending on how it works out the use of a DSP solution might be an interim arrangement that may get superceded by an analogue crooover/equalisation project.

#2 Re: Budget DSP Options

Posted: Sun Dec 12, 2021 10:57 am
by ed
that t.racks unit looks awesome from the screenshots....I'm not usually taken by bolting modules together, it removes some of the challenge of hair shirt development....but I'm seriously considering that for my slob.

The eq facility seems almost identical to a plug I use in the studio, and if memory doesn't let me down, seems similar to the dsp that Nick showed me some years ago at a meet.

At the moment I've got Fane sovereign and Betsy K lined up for the job, but with that I could try a tweet as well.

#3 Re: Budget DSP Options

Posted: Sun Dec 12, 2021 11:47 am
by Ray P
I just watched the Spanish YouTube video on the t.tracks Ed - My understanding of the Spanish commentary didn't get beyond 'Hola' but watching helped my understaning of its operation. I need to get my head around the input/output connections - I think I would just need some RCA plug to mono 1/4inch Jack leads to use it in the usual single-ended connection scenario.

#4 Re: Budget DSP Options

Posted: Sun Dec 12, 2021 5:54 pm
by vinylnvalves
Depending on what you mean by budget the Hypex units which are basically a plate amp with a DSP built in are good value. (Cheap compared to a Lake :) ) Troels has been using them for the bass duties on a number of his more recent speakers such as this http://www.troelsgravesen.dk/Ekta-2D.htm. If I were to buy a DSP again, ( I have my Nadja and a spare) I would probably have gone this way. Chris can probably and point you to other examples, I have heard a number of systems using the Behringer Nuke amps doing the bottom end, they with have limited crossover capability compared to modern equivalents. The big question if where you want to do IIR or FIR crossovers the later need more process power.

#5 Re: Budget DSP Options

Posted: Sun Dec 12, 2021 6:58 pm
by Ray P
Cheers Steve, though I already have an amplifier for the bass drivers - going for an amplifer solution just adds cost for no benefit and detracts from the flexibility of 'upgrading' to an analogue crossover or different amplifier?

On the 'big question' I would prefer to have no crossover, which is why I'm looking to avoid one on the full-range unit and only looking for a DSP solution for integrating the bass section

#6 Re: Budget DSP Options

Posted: Sun Dec 12, 2021 8:12 pm
by vinylnvalves
You could boost the LF by using a bigger capacitor (1000uf). It will give you about 4 db gain.. if that’s enough.

#7 Re: Budget DSP Options

Posted: Mon Dec 13, 2021 7:53 pm
by rowuk
Don't forget that every DSP solution has a (not so small) degree of latency. If the upper range has an analog or no crossover, the DSP solution will delay the bass if it is on the same baffle...

#8 Re: Budget DSP Options

Posted: Mon Dec 13, 2021 8:01 pm
by Ray P
It's not forgotten and is an part of exploring the topic - not sure if I would be able to hear a few milliseconds and to complicate things the rest of the fullrange/bass signal paths are quite different.

#9 Re: Budget DSP Options

Posted: Tue Dec 14, 2021 8:16 am
by ed
Ray P wrote: Mon Dec 13, 2021 8:01 pm not sure if I would be able to hear a few milliseconds and to complicate things the rest of the fullrange/bass signal paths are quite different.
you'd be surprised!.

Absolute bain of my life...from time to time the midi chain will misbehave in the studio setup, usually because an interface driver has failed but there's nothing as frustrating as pressing a piano key and hearing the result 5 to 10 ms later, instead of the 1.7 ms which is normal in my system.

In a xover, logic dictates that if the same instrument is being reproduced around the xover frequency then one part of the note will appear sooner or later than another part. My naive common sense says that will result ina blur. In some cases you may not even realise that you can hear latency.

#10 Re: Budget DSP Options

Posted: Tue Dec 14, 2021 12:22 pm
by Ray P
Cheers Ed, that's interesting.

It's one reason why I see DSP as an interim solution and plan to replace it with a passive crossover/equalisation solution once I work out the best FR curve to achieve the integration.

#11 Re: Budget DSP Options

Posted: Wed Dec 15, 2021 7:23 pm
by Ray P
After some deliberation I'm going to order a MiniDSP 2X4 HD. Although I don't really need it for sorting out the bass on the SLOB I reasoned that it is the best option to recycle into a 'second room' active system using some class D amp modules I have to hand and a pair of really nice Mission 773 floorstanders I've been given.

#12 Re: Budget DSP Options

Posted: Thu Dec 16, 2021 7:03 pm
by rowuk
With the MiniDSP, you can use the low pass for the grunt and the high pass for the melody range - no latency issue. Infinite ability to experiment with slopes and frequency - and a multi band digital EQ for further experiments.