Looking for a solution for EQ, control and active crossover.

[Wiggle8]

I've been reviewing this forum but am somewhat overwhelmed by the options. I am looking for a reasonably priced solution to accomplish the following:

1)Accept the following inputs:
Optical output from Apple TV
Coaxial output from an aptX bluetooth receiver
Ability to act as a network music server is not required as of now but would be a welcome option.

2) Provide volume control via some kind of physical knob

3) Perform crossover and EQ from 2-channel sources to 2-way speakers. Ideally using FIR filters. Provide output via analog line level (volume controlled) to two external 2-channel amplifiers (4 analog signals total). Leaving the option of future expansion for an external subwoofer or upgrade to 3-way speakers.

I have a reasonable degree of DIY skills and can usually stumble through programming but would also not mind a simple solution. I am looking for "reasonable to good" sound quality. I don't want to pay a premium but if there is a sweet spot of cost to performance I'd like to be there.

Solution can be all in one unit or include external support devices such as USB soundcards if needed. My first feeling was a mini-PC with some kind of USB soundcard. The digital inputs are proving to be a limiting option though. Would not mind a more affordable RPi unit if it can be configured for my requirements.

Thank you for the help

 

[CharlieLaub]

I recommend getting a miniDSP 4x10HD and not trying to roll your own solution. It provides all the functionality you seek:

• volume control via a physical knob
• digital coax input
• digital Toslink input
• EQ/crossover functionality
• analog outputs

The only thing it does not do it FIR filtering.

You could put together the following:

• Raspberry Pi
• LADSPA based EQ/filtering with ASLA or ecasound to feed it audio
• multichannel DAC or multiple USB adaptive mode DACs
• if DAC unit does not have digital inputs, then add miniDSP USB streamer
• Not quite sure how to get Toslink input (coax digital inputs are more common) but you could build a Toslink to coax converter on a small PCB using power taken from the R-Pi
• Volume knob?
• All of this would be a cobbled together mess, so you would need to make it neat and put it in a box.

Is it worth the trouble when you can get all of that right away in a supported commercial product? I doubt it.

 

[leoman]

Wiggle8, If you are using a PC (I assume that's an option considering where you posted) you could run foobar2000 on it. It has, via plugins, the capacity to read your default input device, run it through a DSP stack of your choice and output to as many channels as your sound card will support. A 7.1, either USB or PCIe, would give you at least 6 channels with one more as subwoofer (I say that because I'm not sure about rear L/R channel separation), or a basic 8-in-8-out USB DAC could be used (I'm sure the UDAC-8 is good, though it costs more than a typical 7.1 soundcard). A PCIe 7.1 card with 192/24 capability can be had for around $45. A USB card for around the same or less will generally max out at 48/16.

Foobar will let you:
1. use default input via a recording plugin
2. run a FIR EQ in the DSP stack (I use ReaFIR)
3. run FIR crossovers after the EQ using convolver-VST configured for multiple-channel output
4. send it to your soundcard outs via WASAPI
5. reserve the flexibility to go to 3-ways (plus sub)
6. and finally, I do believe, act as network music server; see the foobar2000 plugin pages for UPnP/DLNA etc.; I don't use it but a little reading will tell you if it's adequate for your purposes.

Sorry, no knob, but you could always make a passive box with two dual pots or one quad pot to act as voltage dividers (or just use the foobar volume control).

Best of all, except for the computer and soundcard it's all free including RePhase, with which you can make your crossover FIRs for convolver (ReaFIR has its own FIRs). Convolver-VST will also, in its config file, let you set per-channel delay, matrix your ins/outs including mixing down, and do several other things besides (of course) specifying your FIR crossover file for that channel. The processing power of a laptop or sff desktop for audio is impressive. Your sound should be far better than "reasonable to good." Your FIRs can be huge, and you can add other DSP plugins of your choice to the stack.

As for two inputs, you will have to pick between them someplace. There are options, but how about just an optical-to-coax converter for your toslink line and a simple passive DPDT switch to choose between inputs? I'm assuming your coax output is digital. If you are talking analog, most soundcards have analog plus toslink inputs.

 

[Kjeldsen]

You could skip number 2. and just eq via RePhase and convolver VST.

You could also skip number 3 and use ReaFIR for both eq and crossover (if foobar can use multiple instanses of ReaFIR)

my point is that there is no reason to use two different FIR machines, when you can use just one.

 

[Wiggle8]

Sounds like a PC or the minidsp options are the best. Would a low end laptop have enough muscle to run these FIR filters? Was thinking about getting an inspiron 1100 and a USB sound card to do double duty as a portable measurement machine.

 

[Kjeldsen]

I have only little experience with FIR filters, and simple 2 way filters do work on low en machines.

The easiest way to make filters on a PC is using Equalizer APO and RePhase

 

[Wiggle8]

Thanks. I have used those tools on a desktop and they worked quite well. That machine has a beefier processor of course so wanted to make sure there wouldn't be too much strain on the low end laptop.

 

[Kjeldsen]

I'm thinking of buying a tronsmart ara x5 for my next PC DSP project.

It's fanless and should be able to do some FIR i hope.

 

[leoman]

Foobar will run two instances of ReaFIR, but convolver will act as your channel matrix/mapper (as MiniDSP products do) and you can split each input channel into several output channels and filter each with a FIR crossover. In addition, convolver will permit per-channel level adjustment, output delay etc. I use ReaFIR instead of another convolver instance for my stereo EQ because it has real-time adjustment, something you won't need with the crossover. I'm running convolver on a 1.6G Acer Aspire, not a powerful machine. I run 8 channels for my multiway speakers, and use about 40% CPU. I'm using 192k sample rate and 32k tap (131k FFT) FIR filters. More modest numbers will drop CPU to much lower levels. Also, RePhase gives you a ton of options for your crossover filters and specifies the latency of each when you generate the file.

It's written up elsewhere better than I can do here:
http://www.diyaudio.com/forums/pc-based/302545-computer-audio-old-schooler.html

 

[Kjeldsen]

I actually think Foobar has FIR eq build in?
I'm not a Foobar user anymore so can't try it out. And still you don't really need real-time adjustment for eq. I also like it when doing som quick testing when building new speaker, but in everyday use, you don't really need it.

 

[leoman]

Foobar2000 has no native FIR nor native multichannel features. It's all in the plugins, and convolver has both capabilities with an excellent multichannel feature set targeted specifically at crossovers.

 

[plasnu]

I would recommend professional audio USB interface. You can buy a really good sounding 4ch AD DA for $250, such as Focusrite, Steinberg, etc. Check Gearslutz.com to research them.

I don't know why OP needs FIR. IIR sounds better than low tap FIR that many hardware option offers. Even $500000 speakers are not phase corrected, and sound fine.

Many professionals would agree that the best FIR today is by DMG Audio, and price is carzy low for what it does, but requires high spec PC to do high tap FIR. If you are ready to pay a few hundred bucks for FIR, don't consider anything else.

 

[Kjeldsen]

FIR can do linear phase, IIR can't

Lyngdorf Steinway choose FIR, but you don't have to do FIR crossovers to get a phase linear in room response. You could just correct any speaker with any crossover with a "phase eq" like RePhase/Convolver, Dirac, Thuneau, Lyngdorf and there might be more out there.

I't can be done to sound very very lifelike, but to me it's not that essential. As Plasnu mention, IIR can also sound very good, and you can design a IIR speaker crossover without messing up the phase totally.

 

[Wiggle8]

I would recommend professional audio USB interface. You can buy a really good sounding 4ch AD DA for $250, such as Focusrite, Steinberg, etc. Check Gearslutz.com to research them.

I don't know why OP needs FIR. IIR sounds better than low tap FIR that many hardware option offers. Even $500000 speakers are not phase corrected, and sound fine.

Many professionals would agree that the best FIR today is by DMG Audio, and price is carzy low for what it does, but requires high spec PC to do high tap FIR. If you are ready to pay a few hundred bucks for FIR, don't consider anything else.

Any thoughts on a low cost interface such as the Behringer UMC404HD versus a good sound card such as the Xonar U7?

In the case of the Behringer as well, is it equipped with four or six outputs? Do the "main outputs" count as a distinct set?

 

[Loafmeat]

Hello,

so here a solution. It is with LINUX but not so complicate with scripts it is with GUI.

X-over realized by Laptop, Open Source and 7.1 AV Receiver over Display Port / HDMI

https://1drv.ms/b/s!AnKX4vLSHn4Nh5ty6YD-Ge9iJbJ8qA

It is working with HDMI and 7.1 (5.1) sound card.

regards
Guenter

 

[Wiggle8]

Ended up going for the Xonar U7. Currently have it setup with Eqapo on a Windows 10 basic laptop. Seems to be working great so far. Using 96k/24 bit with FIR filters. Have the input from my aptx Bluetooth box and it actually works very well. Some fine tuning still required but happy so far.

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