First experience with room correction - some guidance needed

[pranabindu]

This is my first post, and I'm a new AS member, though I've been lurking as an unregistered lookie-loo for a few months.

 

I just made my first DRC filter, and I feel like I need some guidance as to where to go next.  I used Audiolense XO, using Mitch Barnett's guide here (thank you!).  I used the settings he recommended in that guide, building a target that is flat to 1kHz, descending in a straight line to -7dB at 20kHz, linear phase.

 

The nice thing about the filter is that individual sounds/instruments are better defined within the soundstage.  They are more separate and more sharply defined.  Part of that seems to be a blacker background, but that might just come down to the fact that the individual sounds/intruments are better delineated.  Imaging does not seem to have been improved, by my room is bad for that (strong asymmetry).

 

However, the filters sound harsh to me.  It's as if the digital sheen that some audiophiles complain about was turned up several notches.  It's too much.  I breathe a sigh of relief when I switch off the filter, though it would be nice to have some of that definition back.

 

I will play with the different filter settings and target curves, but I was hoping y'all might have suggestions about what settings would best address the harshness issue.  It's not distortion - everything is clean.  It's just too clean, too sterile.  It reminds me of when I figured out that I had been skipping my favorite tracks, when shuffling the library, because they were lossy files and made my brain hurt.  Not quite that bad, but along that spectrum.

 

Equipment: DeVore Fidelity O/96; VTL ST-85; Lamm LL2.1; Musical Fidelity V90; HifiBerry; Roon ROCK on a NUC with USB storage in a separate room.

 

Thank you for any help you might have.

[skatbelt]

Looking at your equipment: could it be that your DAC is causing the harshness / digital sheen you experience? Beautiful speakers, beautiful pre-amp, beautiful amplifier but that DAC....

 

Other remarks: DRC when done right does make a system sound balanced. But a first perception could be that of a certain lean-ness. This is because most clean-up/correction is often done/needed in the lower frequencies. In general, I think a lot of audiophiles tend to strive for and are used to a fuller sound than reality (what was actually recorded and mastered). This can work for certain genres bus leads to unbalanced representations of other types of music and also leads to the misconception that this or that speaker is good for rock but not for classical music. A (good) speaker is not picky on genres is my belief.

 

I am a strong believer in DRC in addition to room treatment and proper speaker placement. Harshness is not something I experienced as a result of DRC. A somewhat lean sounding system is. This is can be often corrected with slightly adjusting microphone placement in relation to the MLP and by the way the rest of the room is measured ( I use Lyngdorfs RoomPerfect and this system uses random measurements in the room besides a measurement on the MLP).

[pranabindu]

Yeah, the DAC is the weak link.  The harshness at issue has some history in the system - before I tried room correction.  I upgraded to the O/96 from the O/93, and that abrasive feel to the sound was more prominent in the smaller speakers.  The O/96 mellowed it, but didn't get rid of it.  Adding a rug in front of the system eliminated it, so I thought it was related to the amount of reverberant sound power in the room.  But the DRC filter brought it back.  Weird.  I don't think that history excludes the DAC as the problem entirely, but it had given me hope that I could live with the DAC longer.

 

I trust my wife's ears (she's part bat), and she really liked the filter.  I'm thinking that it's probably my own prejudices about the sound I'm used to.  I don't think it's a reaction to the leanness, though, because the bass response in my room, without correction, is pretty good.  The only measured issue is a 10-15 dB dip centered around 100Hz.  Otherwise, it's close to flat (hallelujah).

 

I'm gonna keep playing with it, and I'll try to listen my way out of whatever bias might be in play.  Also, I think I might be able to plunk down for the PS Audio DirectStream DAC by the time they have their next sale.

 

I should also try my old Perpetual Tech DAC in the filtered system, to see if I can discern the role the Musical Fidelity is playing in the harshness.

 

Thank you for your endorsement of DRC.  I had never heard of the problem I had with it, so I suspected that my experience was not typical.

[Mike48]

If it's easy, try a minimum-phase filter. You might like that better. I am not a theoretician, but I know one; his opinion is that room problems are minimum-phase problems and should be dealt with minimum-phase filters. I do NOT want to get into a discussion of theory, but I DO think you should trust your (and your wife's) ears as to which is better.

 

I had a mastering-grade digital equalizer (Weiss EQ1 LP) that would do linear phase filters. When I used it for room correction, I preferred the minimum-phase filters.  So again: trust your ears.

 

Also: try a little rise in the bass (say, a gentle 2dB rise below 200 Hz).  Many target curves have that.

 

No measurement perfectly reflects what you will hear, so don't be afraid to experiment.

[pranabindu]

Thanks @Mike48!  I do plan on experimenting more.  I already went through a second round of experimenting: I made multiple filters, but with only two target curves.  I played with linear vs. minimum phase, and I did, indeed, prefer minimum phase.  My conclusion from that second round of experimentation was that I needed to play with target curves.

 

I also have a nagging suspicion that my room wouldn't benefit that much from DSP correction filters.  The bass response is really good on its own, and the only objections I have are unimpressive imaging and not much stage depth.  I have no clue if DSP can help with imaging and depth.

 

Also, I worry about the whole purity-of-signal thing.  It's such a pervasive audiophile "virtue," that it's difficult to avoid suspicions that all that processing will end up doing more harm than good.  I don't know.  It's frustrating that the sound before correction is probably acting as a prejudice.  Makes the A/B process a bit aporetic....

 

For those reasons, I've been spending my free time building room acoustic treatments.  It's taking some time, because they have to pass the WAF test.  She is very accommodating, but I know there are limits.  I added an area rug between the system and me - that had positive WAF and very positive effects on the acoustics.  I'm building two eleven-pointed star-shaped frames for absorption panels made from Owens Corning 703 (hendecagrams!).  Those will be attached to the first-reflection points on the half of the vaulted ceiling that is above the listening space.  The side walls, surprisingly, present no first reflection points (open concept on the left, bay window on the right that reflects at each panel on the space between the speakers).  Turns out, those mitre joints are difficult to make.  After that, I will have my go at some fractal QRD's for the front wall.  I've been trying to buy some SMT V-Wings, but I haven't heard back from the owner in a long time.

 

As to DSP, I also want to experiment with limiting the correction to frequencies below 500 or so.  Even though I think my room's bass response is great, a lot of folks (especially at the Roon forums) advise against correcting above 400 or 500.  Worth a try, I guess.

 

Thanks again for the suggestions.

[Mike48]

@pranabindu: Harshness is tough to deal with. Your DAC is hardly the last word, but none of the reviews categorize it as harsh. I usually associate harshness with speakers with a rising treble response (the O/96 does not seem to have that) or very bad digital conversion, on the electronics side. On the acoustical side: unabsorbed first reflections or slap echo (a separate but related problem). So you are on the right track with room treatment, and I agree with the use of diffusion on the front wall. Make sure you sit far enough away from the QRDs -- If I were closer than 8 feet, say, I might consider other forms of diffusion instead. And do walk around the room, clapping, to see how much slap echo there is. The less, the better.

 

Regarding DSP and imaging: in my experience, it can improve imaging, both specificity and stability, by reducing differences in realized response from speakers in an asymmetrical room. However, the quality of the DSP algorithm becomes more important as you increase the upper frequency limit. Some algorithms/hardware can cause a bit of hardness as a side effect, but DSP has gotten much better lately. Now I'm using an Anthem STR Preamp, and I run DSP up to 5kHz and get the best sound I ever have -- which means very little to you unless you live close by (Portland, OR) and want to visit. So again, let your ears be the judge.

 

DAC quality does affect imaging, in my experience. Also, I got far better imaging with my former DAC after adding a Mutec MC-3+USB reclocker. I still use it -- easier than doing more listening tests.

 

I hope some of that stimulates some thought.