That’s very interesting Erik, thanks for posting. I don’t know enough to make a comment but have some questions for you and @hammer , if you would pardon my inquisitiveness:
What shape and (rough) dimensions is your room ? What sort of furnishing, carpet, wall coverings ? Any room treatments ?
What type of speakers ?
What were your thoughts about your system before you measured it, were the graphs consistent with expectations or something of a surprise ?
If you’ve had a chance now to listen to engine on/off, how do they compare (have seen @hammer’s comment above).
When you try to EQ for your room based on your listening position, it is better to do some kind of spatial averaging so that the EQ works when you move slightly away. You may get better results by making multiple measurements (imagine a 3D box and 8 corners and at the center) then using the average of those measurements for the EQ.
My initial observations on REW using an un-calibrated Radio Shack SPL:
REW showed the holes we suspected were there in the sound
Even a very smooth room EQ applied as a convolution in HQP produced interesting results but not something I’d want enabled
I think we the right hardware i.e., properly calibrated mic / SPL, and time spent in REW, a nice room EQ could be achieved.
I really enjoy the HQP integration with Roon - nice fit. There are some quirks, but certainly manageable. My use of HQP is for some very light lifting - mostly up-sampling redbook to 176KHz. I let my Meitner do the rest of the up-sampling as it does a superb job on its own.
My room is 17x30x10 (WxLxH). I sit about 14 feet from the speakers and that’s where I setup the mic. Furnishings, just living room furniture (i.e. coffee table, couch, etc) and tile floors. I do not have any room treatments.
My speakers are Vapor Audio Sundog’s with a RAAL 70-20XR tweeter and Accuton C158 woofer. I run the speakers with a HSU ULS-15 subwoofer. The cross-over on the speakers was designed, with Ryan from Vapor’s recommendation, to start rolling off below 170Hz and that’s where the sub would take over.
In regards to the expectations, I’m just experimenting for now. But long term, I’m looking to make improvements when I learned more about how to take measurements and use REW. And now that I see the how I had the sub setup, I’m glad that I went through this first exercise.
I haven’t done any comparison’s yet between the engine on/off, because HQP is running on a Debian Virtual Machine in another room. I haven’t taken the time to setup Teamviewer or VNC on that VM yet.
Some generic recommendations. I usually use 1/12th octave smoothing before running eq filter design in REW. The generated filters don’t look too bad though. With smoothing you are also less likely to end up with high-Q eq filters that usually sound bad.
Note that if you allow +9 dB boost, you need to check the max boost generated for the filters and set gain compensation in HQPlayer accordingly. That will drop the overall level for example by 9 dB, but avoids running to peak limiting when music content happens to contain frequency that hits the boost peak…
Another recommendation is to keep corrections only up to 1 kHz or lower, usually problems are in the bass range. However, do not try to fill up null points with excessive max boost (I’d recommend 6 dB max boost), that won’t be possible but attempting it will have adverse effects.
Coming up with good target curve is essential. Good starting point is straight line from 20 Hz to 20 kHz with about -6 dB drop at 20 kHz vs 20 Hz. One of the commonly referred and popular ones is the B&K house curve:
@jussi_laako thank you kindly for sharing - great suggestions actually. Been using HQPlayer for about 2 weeks now and spent some time a week ago with REW to develop a left and right convolution. These suggestions help tremendously.
Question - how critical is the mic / SPL? I see the miniDSP mic being recommended, but I can’t understand how a USD$75 mic can be accurate enough? I equate REW to calibrating and profiling a computer monitor for colour critical work, whereby a top quality meter is required and can’t be purchased for USD$75.
If you want better control over the EQ (i.e. do it manually) and also correct for the phase, importing the REW measurements into rephase is also a good option, then you can create the filters you need for HQP in rephase (warning, some steep learning ahead )
No, I use something even cheaper (ECM 8000), but I think UMIK-1 should work just fine. With the amount of uncertainty introduced by mic position/direction and room measurement in general, you do not need ultra-pricise expensive microphone as long as you have the calibration file for your mic. You can also check recommendations by Room EQ software vendors such as Dirac and Acourate and REW forum too.
I EQ headphones more than I do Rooms, so there may be other experienced folks here who can chime in. However the process I use to EQ are quite similar and of course I use a different kind of microphone for Headphone and in-ear measurements.
Hi @andybob, I finally got around to the A/B testing. But before doing so I tried to improve the room response by moving my Subwoofer around. I did not have much space to play with, but I moved it up against the wall and to the right about 1 ft. I was able to slightly better the low end dips. I took @jussi_laako EQ advice (thank you by the way) and created new filters.
I wish I had a better way to describe the improvement, but it’s as if everything is neater, tighter if you will. If I were single and could position my speakers and subwoofer anywhere I wanted, I’m sure there’s an optimal position where the recommended 6db max boost would yield a nice smooth curve. Since I don’t have that liberty, the improvement is probably not as good as it could be.
I took 3 measurements at various positions across my listening couch after calibrating the umik-1 using a 10 Hz to 22kHz sweep, both speakers and averaged them:
These plots are so good that you can limit correction to frequencies below 250 Hz. Above that the variations are small enough (within ±5 dB or so) to be left untouched.
I’m no expert (a keen beginner, still learning) but isn’t the desired output curve one that’s sloping downwards - B&K style? In that case wouldn’t a full range EQ be better?
As I understand it the problem with full spectrum EQ is that as the frequency rises, the response of the room becomes more local. So correcting a 5 dB hole in one location can create a 5 dB peak mere centimetres away. Averaging measurements can show up persistent features, but correcting for them can turn into a game of whack a mole. Lower frequencies have a less localised response (leaving aside nodes) and so are more amenable to global EQ.
I’d imagine that full spectrum EQ for headphones could work very well.
I’m going to start by adjusting my active woofers. I have them boosted a bit because I generally listen at lower volumes than the test (80 dB) and the bass response falls away a bit as volume decreases. I’ll make some changes and also try some tests at listening volume.
Before measuring I was mainly concerned about a hole in the mid-bass, which I can see at 60-100 Hz. I hope to straighten that out significantly by changing the active woofers and then applying some EQ.
@andybob These are impressive curves. Equalization or no. What speakers do you use? I have always been convinced that speakers, and their interaction with the room, are vastly more important than any electronics. Imagine upgrading the DAC to a femto-clock and seeing 5 or 10 dB response changes.
They’re Australian speakers made by Mike Kontor, Noteperfect Maestro. They use Morel drivers and the cross-over between mids and tweeters is really gentle and indistinguishable by the listener. I’ve substituted in some 8AWG North Creek inductors which hang off the bottom of the crossover box like the proverbial.
Edit: Here’s the said inductors installed under the crossover, with the speaker cables soldered on to the inside binding posts. The inductors are the only component in the midrange crossover.
The room it is facing into is L shaped, so there is no reflection from the left, the first reflection off the right wall has a long stretched canvas artwork on it, the carpet is on the floor and there is a blind behind the listening couch which is about 6 metres from the speakers.
I have an L-shaped room and always figured that it was killing my sound having reflections on the right but not the left (as in your case). Do you notice any significant impact?
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