Using REW+Roon/MiniDSP for extreme EQ

[Nic]

TLDR: Would REW work not just for slight room correction, but to measure the room to account for speakers that require an EQ with +/- 20dB adjustments?

Longer version: As mentioned in the setup thread - I’ve got Bose 901 Series IV speakers (and I’m not likely to upgrade any time soon). The speakers come with an active EQ (currently between my pre- and power-amp), and it’s by far the weakest link in the system (I’ve had it rebuilt twice, and it’s on the way out again). As you can see here (scroll down 1/3 of the way), it does some pretty aggressive EQ.

After not really paying attention to HiFi for ~15 years, I came back to discover that DSP is a thing, and it works. My right wall is shorter than my left, so the soundstage has always been off-centre. I tweaked the speaker DSP settings in Roon and got it perfectly centred. Amazing! I then read Magnus’s excellent post about using REW to build room correction curves for a convolution EQ and got to wondering if it’s possible to replace the 901’s EQ (either in Roon, or with a MiniDSP).

It turns out Deer Creek actually sells a MiniDSP unit with the 901 curves. However I’d like to also do room correction.

So one option is to install the MiniDSP, then use REW to do room correction and add it to Roon (meaning no room correction for vinyl).

A second is to use REW to get the room correction curves and then either load it on to the 901 EQ’d MiniDSP (unsure if I can do this - have emailed them to ask), or add another MiniDSP with the room curves.

The third option is to pull the current EQ out, and use REW to do room correction, which I’m hoping might also build the 901 EQ curves at the same time. I’m wondering if that’s actually likely? Does REW work at such extremes (+/- 20dB) - or is it more just for small adjustments? I figure I can test in Roon, and if it’s working well, load in to a MiniDSP and get EQ+Room correction for my vinyl as well.

So am I dreaming, or is the third option possible? Are there any other options I’m missing (and yes, I realise replacing the 901’s is the obvious one!)

[NOA]

Hi Nic,

Nice question.

I’m no deep expert in this but I think in principle the third option should work. Whether REW allows for +/- 20 dB correction is just worth a try. For convolution in Roon you need to upload correction file for each resolution. I could imagine that with 16 bit digital headroom could become critical with huge correction.

If I were you I‘d create convolution files in REW and upload them in Roon to see how it sounds, pay attention to bit depths. If it works you can figure out how to do it with a miniDSP (no experience here) and replace the BOSE EQ at all.

Cheers
NOA

[Joe_Gratz]

REW allows for such extremes --though of course there are issues with headroom, etc. I have used REW to do a truly stupid convolution (speakers under the bed in the bedroom – compensating for the resonance of the springs and the dampening of the highs by the mattress, etc.), which involved 20 dB swings, and it worked great. Not a purist setup by any means, but it does the job.

[Nic]

Thanks @NOA and @Joe_Gratz.
Sounds like it’s worth a shot, particularly given it’s the cheapest option.
I’ll see how I go and report back.

[Nic]

So step 1 of working out a plan was getting the Umik-1 and trying out some measurements on REW. The Umik arrived yesterday, and I got some time today to have a play around.

This was a crack at just doing a measurement and generating correction curves in REW (following @Magnus’s guide), with the existing 901 EQ in place (dark green was the measurement, light green the predicted outcome with curves, and blue the target)…

I figure all that weirdness <60Hz is due to the small drivers in the 901s, and they basically hit some low-end resonant frequency? As a result I set REW not to generate EQ curves in that range.

The roll-off after 10kHz is also…abrupt! The weird thing about that is that the 901s can often sound a little too harsh in the highs.

Just loading in these curves made a noticeable and pleasant difference. Not enough to elevate 901s to a ‘serious listening’ level, but definitely more detail and lot less of the colouration/warmth that the 901s deliver.

Anyway, the purpose of all of this was to see if I could replace the 901 EQ, not just do room correction with it. So I took it out of the loop, and did another measurement. If you’ve never heard the 901s running without the EQ, imagine 20 crappy laptops all playing out of their speakers in unison, facing the back wall of your room. So I was expecting some pretty major curves, and was a bit surprised at the result…

Again the <60Hz craziness is there, but REW did a stellar job of things! I loaded these up in to Roon and it sounded brilliant in comparison! An immense amount of detail, and what at first I felt was a very thin sound, after 10-15 minutes I got used to and realised just how dense the old sound was.

One thing I did notice was walking around the house - it was like having standard speakers, where once out of the listening spot things don’t sound great. With the default 901s and EQ one of the great things is walking around the house and the music is really everywhere. So it was interesting that re-creating the 901EQ in REW removed a lot of that, but delivered a lot more detail when in the listening position.

So the first step of the experiment seems to have worked! I now have everything hooked up in a way that I can listen to my vinyl through the 901EQ, or listen to Roon through the 901EQ with digital room correction, or listen to Roon with purely digital EQ. My ears are a bit tired for today, but over the weekend I’ll spend some time doing some more comparisons (and probably re-doing my REW work a few times!).

[ogs]

You should try to find out what that ‘60 Hz craziness’ is and get rid of it. Ought to look more like an even measurement curve similar to the upper range. Otherwise REW seems to do an excellent job. Not running the signal through the Bose equaliser will give you better sound.

Remember that Roon can handle several convolution jobs in series so if you can do a sweep of the Bose equaliser (line in/out) and make a separate filter for the EQ curve you could use the correction you make with the 901 EQ in place on the second convolution.