Hardware for room eq

[Willem]

Reading Amir's review of the Paradigm PW-Link I wondered if there are any preferably affordable digital in digital out boxes like that Paradigm unit, but without its failings (I am not interested here in its other functionality). The MiniDSP is a well known and often used little box to upload REW correction curves to but it only has analogue in and analogue out, so you add both an ADC and a DAC to the chain, and not great ones at that. What I would like is a little box in the digital part of the chain that can do dsp room eq, preferably automatically, but I am OK with uploading REW correction files. I am currently using an Antimode 8033 to equalize my subwoofer and I am so happy with it that I would like to do the same for my main speakers. Right now I am trying to set a number of parametric filters for my RME ADI-2 AC, and that will be enough for the worst peaks, but something more sophisticated would be nice. In my home office I only use my desktop computer as a source, so there the Equalizer APO was enough to upload the correction files to. In my main system I have four (optical) sources so I would like to insert the unit right before the DAC. Does anyone have a suggestion, or is the market not yet ready?

 

[CuteStudio]

Behringer Ultracurve + matching mic. does the job.

 

[BDWoody]

Behringer Ultracurve + matching mic. does the job.

That looks like quite a capable little box... Do you have one?

 

[DonH56]

I think there are miniDSP versions that have digital I/O.

 

[CuteStudio]

That looks like quite a capable little box... Do you have one?

Yes! I actually bypassed the opamps and feed the DAC output straight out the back. I use it in conjunction with a Behringer rate converter which I feed 44.1 or 48k (it then creates a re-timed 88.2 or 96k) and I really now just use the Ultracurve as a DAC and display.

I have EQ'd rooms with it though, it's quite competent at doing it in my experience although an echoey room will always have odd nodes that are impossible to EQ a few inches away from the mic.

 

[Willem]

I just discovered that minidsp do indeed have a digital in digital out box, the miniDSP OpenDRC-DI. Unfortunately here in Europe it is some 50% more expensive than in the US, and you also need additional software. The combination looks a bit daunting to operate, but I will start reading.

 

[Soniclife]

They also have the shd studio with built in Dirac.

 

[Olli]

Or the MiniDSP DDRC22D if you like DIRAC.

 

[Xulonn]

I considered DDRC, but it turns out that all I need is a good microphone (~$100), and i can use REW (free) to create filters that I can implement with Daphile (free), the Linux-based player running on my Intel NUC HTPC.

Am I headed in the right direction?

 

[Willem]

That is probably like the Equalizer APO software for Windows that I use to upload REW correction curves onto my home office pc. That works very well.
However, this is for a system without a PC. The default for that was always the minidsp, but that only had analogue inputs and outputs so it used a double conversion from analogue to digital and back. I wouid have thought that staying in the digital domain would have made the unit simpler and hence cheaper and hopefully cleaner sounding. But the digital in digital out alternatives are far more expensive.

 

[Xulonn]

That is probably like the Equalizer APO software for Windows that I use to upload REW correction curves onto my home office pc. That works very well.
However, this is for a system without a PC. The default for that was always the minidsp, but that only had analogue inputs and outputs so it used a double conversion from analogue to digital and back. I wouid have thought that staying in the digital domain would have made the unit simpler and hence cheaper and hopefully cleaner sounding. But the digital in digital out alternatives are far more expensive.

Perhaps Topping or one of the other budget DAC manufacturers whose products measure well here at ASR will offer the option to use FIR filters in future products or upgrades. Whoever does it first (and correctly) will likely see a nice uptick in sales.

 

[TimW]

The default for that was always the minidsp, but that only had analogue inputs and outputs so it used a double conversion from analogue to digital and back. I wouid have thought that staying in the digital domain would have made the unit simpler and hence cheaper and hopefully cleaner sounding. But the digital in digital out alternatives are far more expensive.

The miniDSP nanoDIGI 2x8 is the least expensive digital in/out device they sell. No FIR or automated room correction though.

 

[q3cpma]

A simple SBC with brutefir should be able to act as a DSP easily (use the ethernet for the digital in).

 

[LTig]

That looks like quite a capable little box... Do you have one?

I do as well. Used it for a long time as DAC in my hifi system, with a single EQ setting, until it got replaced by an AV preamp. Afterwards used it to equalize a small PA system and use its feedback destroyer for a speaker mic.

It's definitely a very capable unit although its DAC does not measure great. Here are THD and IMD measurements of its DAC taken with an old Edirol UA25. The latter is not very good either but its loop back performance is about 10 dB better so the results should not be too far from the truth.

THD of 1 kHz sinus at -10 dB:

IMD of 19+20 kHz at -13 dB:

 

[mitchco]

While I am a big fan of Acourate and Audiolense on the PC for room correction, there seems to be limited hardware solutions. Limited in the sense of the number of FIR filter taps available. Depending on the platform like OpenDRC, Dirac, DEQX, the number if FIR filter taps is limited from around 2048 to 6144 taps: https://www.minidsp.com/forum/opend...s-like-opendrc-has-some-new-competition#21877

The lower in frequency you want to correct over a longer time period, the more taps you require. For comparison, on the PC, I run 65,536 taps of FIR correction.

A BruteFIR implementation may be your best bet...

 

[BDWoody]

I do as well. Used it for a long time as DAC in my hifi system, with a single EQ setting, until it got replaced by an AV preamp. Afterwards used it to equalize a small PA system and use its feedback destroyer for a speaker mic.

It's definitely a very capable unit although its DAC does not measure great. Here are THD and IMD measurements of its DAC taken with an old Edirol UA25. The latter is not very good either but its loop back performance is about 10 dB better so the results should not be too far from the truth.

THD of 1 kHz sinus at -10 dB:
View attachment 30876

IMD of 19+20 kHz at -13 dB:

View attachment 30877

That is a bit sloppy...

I am about to dig further into an older Krell Showcase preamp/processor which has an intimidatingly thorough EQ section, with lots of flexibility in terms of filters, slopes, band ranges, etc..., so I may try to use the Umik mic and REW to try to see what it would do, and adjust the krell to come as close as I can. I know I can load settings into roon, but if I can get the preamp sorted out, it might let me get pretty close for any source.

If that doesn't work out, I may look into some of these multichannel DAC options.

 

[Daverz]

I considered DDRC, but it turns out that all I need is a good microphone (~$100), and i can use REW (free) to create filters that I can implement with Daphile (free), the Linux-based player running on my Intel NUC HTPC.

Am I headed in the right direction?

Sounds like a plan. I use brutefir and the BrutefirDRC LMS plugin on my music server and DRC-FIR to generate the taps. Of course, if you want to do something more ambitious like a digital crossover, you'll need multiple digital outs. Check out March Audio's reviews of the Motu gear.

 

[Hipper]

I've had a Behringer DEQ2496 for fourteen years. I use it between a CD transport and DAC, so only in digital. It only has XLR inputs and outputs. It has a ten PEQ filters for the two channels, and 31 band GEQ per channel. It has an ADC and DAC which are said to be competent - I used the ADC when I had a turntable but never used the DAC. It also has other functions which I don't use.

I have in the past used its own Real Time Analyser but these days I use REW to create filters then add them manually to the PEQ.

I've never had any issues with it, can't hear any noise from it and have therefore resisted buying far more expensive solutions.

If you need an electronic crossover with some EQ the Behringer DCX2496 is also well thought of in some quarters. My speaker manufacturer used it and said its ADC and DAC were neutral.

http://www.decdun.me.uk/deq2496.html

Here's a long detailed review of one of the Antimodes:

https://www.whatsbestforum.com/threads/dspeaker-anti-mode-x4.26851/

 

[CuteStudio]

I do as well. Used it for a long time as DAC in my hifi system, with a single EQ setting, until it got replaced by an AV preamp. Afterwards used it to equalize a small PA system and use its feedback destroyer for a speaker mic.

It's definitely a very capable unit although its DAC does not measure great. Here are THD and IMD measurements of its DAC taken with an old Edirol UA25. The latter is not very good either but its loop back performance is about 10 dB better so the results should not be too far from the truth.

THD of 1 kHz sinus at -10 dB:
View attachment 30876

IMD of 19+20 kHz at -13 dB:

View attachment 30877

Did you measure the DAC after the dodgy output opamps or before (requires a small but popular mod)?

 

[LTig]

Did you measure the DAC after the dodgy output opamps or before (requires a small but popular mod)?

I'd say after - the DEQ2496 is not modified, and AFAIR I used the XLR output.

Do you have a link to this popular mod? And a link to the schematics? If i find time I could do the mod and measure before/after.