Best approach to EQing and Dirac DSP?

[Old_School_Brad]

This will likely not be sufficient, as the MiniDSP does not show true peak volume but RMS volume only. There is a high risk of clipping when you are close to 0dBFS.

Better attenuate the master volume by 9dB, as 9dB AFAIK is the max. boost Dirac applied in its MiniDSP implementation.

I asked for a true peak display in the MiniDSP forum but never received a feedback from the company.

That's correct. By analyzing the difference between the measured response and the target curve, you can identify the EQ boost being applied and make the necessary adjustments to the system. Personally, I also test with tones in areas where a boost might occur. One should always leave plenty of headroom. However, my own target curve focuses on cutting rather than boosting, as I find this approach delivers better results. Additionally, I have ample gain available downstream to compensate.

 

[Sir Sanders Zingmore]

Yeah, I think that's how you'd describe what I'm doing, along the lines of the Dirac pic below.

View attachment 410250

Thanks again to all and Happy Thanksgiving!

That's a very odd looking target curve - it's telling Dirac to add a boost of over 10dB at just below 200Hz (as well as two other smaller but still unusual deviations)

 

[markstein]

That's correct. By analyzing the difference between the measured response and the target curve, you can identify the EQ boost being applied and make the necessary adjustments to the system. Personally, I also test with tones in areas where a boost might occur. One should always leave plenty of headroom. However, my own target curve focuses on cutting rather than boosting, as I find this approach delivers better results. Additionally, I have ample gain available downstream to compensate.

You can simply do a full sweep with REW, using USB connection. Without correction and with Dirac filters applied. Then it should be clear how much attenuation is required at a minimum.

I personally would also attenuate the source by 3dB to mitigate the risk of intersample overs in the MiniDSP ASRC. You can subtract these 3dB from your overall attenuation.

 

[klettermann]

Thanks, yet again, for the comments. It's hard to overestimate the value here. Everything I've done thus far has been with actual understanding ranging from zero, at the start, to something only slightly greater than that. So I'm starting over from scratch. And it's fun anyway. I have strong experimental design & technical background (chemical R&D), but new to acoustical science. Any my listening space if a wonderful lab to explore all this stuff. Anyway, a few comments on the comments.....

Just to chime in with my own experience - use the MMM method to correlate your static sweeps and make sure you're not correcting something that only exists in one place in time/space. I would use the miniDSP EQ to then get rid of the worst offenders up to about 400-500Hz as I find presenting Dirac with something halfway decent allows better correction filters in the end.

I personally would stop correcting at about 300-500 Hz upwards and let Dirac handle the bass correction only. Never liked Dirac full correction in my untreated unsymmetrical living room. Btw. I also never liked Acourate full correction. Sounds liveless and boring.

These 2 relate to each other. In establishing the MLP I did lots of MMM measurements and concluded that they weren't materially different from the MLP itself. So I kept on just using the MLP measurement. As for low end correction via Dirac vs MiniDSP EQ, I'll try both. That said I was quite happy with letting Diract deal with the broad mid- and high end shelves. More to follow. Cheers,

 

[klettermann]

. . . . . As for the level issue, I'll go back and reexamine what I'm doing. Thus far I'm not aware of any problems though, but who knows? To be sure, I'm focus on lowering the peaks. rather than raising dips.

 

[klettermann]

That's a very odd looking target curve - it's telling Dirac to add a boost of over 10dB at just below 200Hz (as well as two other smaller but still unusual deviations)

Yes! That was a very early curve while I was experimenting with Dirac. It happens to be the only one where I took a screen shot and Dirac doesn't work unless the computer
is plugged into the MiniDSP (please correct me if there's a way!). This is a significant flaw IMO. It would make life a lot easier if I could use it offline to make changes.

 

[klettermann]

You just made me stop and think The first SBIR frequency is a cancellation, but this is with a monopole design! With a monopole, the back wave is in phase with the forward wave. The reflection from the front wall is in-phase with the incident wave. By the time the reflection travels back to the speaker, half a period has passed, so it is now out-of-phase which results in a cancellation. With a dipole, the back wave is out-of-phase with the forward wave. So the first SBIR frequency should be reinforcement. You should be seeing a peak at 70Hz if you have your dipole placed 48" from the wall. Then again, I don't know enough about dipoles to know if dipoles behave as dipoles at long wavelengths, or whether they are omnis. As you can gather, what you see (if it is SBIR) depends on whether the rear wave is in-phase or out-of-phase with the forward wave.

I will need to defer to somebody more knowledgeable than me about this and humbly warn you that I might be in error. I am confident that my understanding of SBIR with monopoles is correct, not so confident about SBIR with dipoles. So i'll shout out to @NTK and @Duke.

Regardless, there is no practical benefit of knowing whether that cancellation at 94Hz is due to SBIR or a room mode, because either way the solution is the same. You can choose to ignore it (which is what I would do, because it is so narrow) or you can use another speaker or subwoofer to fill it. I for one, acknowledge that tilting at windmills is fun and you learn a heck of a lot in the process. So get yourself a horse and a lance and go for it!

I thought it might be illuminating to see the room layout. Note also that there are big ASC bass traps in the front corners. I struggled a long time to with the subs and other positioning to get it is good as I could. It's always a compromise! Cheers,

 

[markstein]

That's correct. By analyzing the difference between the measured response and the target curve, you can identify the EQ boost being applied and make the necessary adjustments to the system. Personally, I also test with tones in areas where a boost might occur. One should always leave plenty of headroom. However, my own target curve focuses on cutting rather than boosting, as I find this approach delivers better results. Additionally, I have ample gain available downstream to compensate

That's correct. By analyzing the difference between the measured response and the target curve, you can identify the EQ boost being applied and make the necessary adjustments to the system. Personally, I also test with tones in areas where a boost might occur. One should always leave plenty of headroom. However, my own target curve focuses on cutting rather than boosting, as I find this approach delivers better results. Additionally, I have ample gain available downstream to compensate.

Hi, this is not what I meant to say.

You can measure the frequency response of your MiniDSP with Master volume at 0dB and all EQs disabled (digital in - digital out) and then again with Dirac filters enabled and - let's say -10dB master volume. You will exactly see the Dirac filter curve and can check how much headroom is required to avoid clipping.

 

[Old_School_Brad]

Hi, this is not what I meantime to say.

You can measure the frequency response of your MiniDSP with Master volume at 0dB and all EQs disabled (digital in - digital out) and then again with Dirac filters enabled and - let's say -10dB master volume. You will exactly see the Dirac filter curve and can check how much headroom is required to avoid clipping.

Your suggestion follows a similar approach but introduces additional steps that may not necessarily improve accuracy. It’s worth noting that the measured response in Dirac cannot be directly compared 1:1 with a single measurement in REW. Dirac gathers data from multiple measurement points to create an averaged response, though the specific weighting applied by its algorithms remains unclear. In theory, you could approximate a similar response in REW by using MMM across the same area where Dirac measurements were taken. However, the details of how Dirac processes this information are not fully known.

In conclusion, the simplest and most effective approach would be to directly compare the target curve with the measured response within Dirac itself.

 

[Mort]

My partner thinks I've lost my mind, and she's right!

Mine is right there with yours. Thank you for the write up.

 

[markstein]

Your suggestion follows a similar approach but introduces additional steps that may not necessarily improve accuracy. It’s worth noting that the measured response in Dirac cannot be directly compared 1:1 with a single measurement in REW. Dirac gathers data from multiple measurement points to create an averaged response, though the specific weighting applied by its algorithms remains unclear. In theory, you could approximate a similar response in REW by using MMM across the same area where Dirac measurements were taken. However, the details of how Dirac processes this information are not fully known.

In conclusion, the simplest and most effective approach would be to directly compare the target curve with the measured response within Dirac itself.

You still don't understand.

I am not talking about acoustic measurement of the room/loudspeaker setup, but about measurement of the Dirac filter curve applied by the MiniDSP DSP pipeline (measurement via USB digital in -> digital out).

 

[Old_School_Brad]

You still don't understand.

I am not talking about acoustic measurement of the room/loudspeaker setup, but about measurement of the Dirac filter curve applied by the MiniDSP DSP pipeline (measurement via USB digital in -> digital out).

Oh.
I believe comparison between the measured response and the Dirac house curve should suffice. Especially when you aim to avoid excessive boosting.

 

[ViperDom]

After reading through the responses one big potential miss i am seeing is the Timing of your subwoofers.
This should be done Prior to running DIRAC or doing any sort of EQ.

Forget about the calculations/tools. Just bang out the measurments in 5ms increments like the following videos demonstrate.
It will be pretty obvious in what ballpark the FR is most desirable. Zero in on this range and re-run with 2sec increments to dial in max amplitude.
OP, with your dual sub setup the process is to optimize the timing of one sub with relative to the other, then adjust both(as one virtual sub) to sync with the mains. For example: Sub1 needs 15ms to be happy with Sub2. OK. Now you compare both subs combined with the mains adjusting them equally untill everyone is happy. So the result may be Sub1(45ms) Sub2(30ms). There will maintain the 15ms delta between subs.

 

[ViperDom]

Also, wanted to add:
SBIR calcs are legit, but in my experience actual measurements may not agree. You can tell me moving a speaker away from the wall by x amount will cause y change, but if the microphone says otherwise then it has the final word. Therefore you are better off simply taking multiple measurements in set increments with REW allowing you to visually see what exactly is going on. Start with speakers against wall. Measure. Move out in 6" increments taking measurements as far as you could possibly tolerate the most forward position. Look at the FR results overlayed. What looks desirable to you? Perhaps the 36-48 range is way better than below/above, OK, Now measure within that range with 3" increments to see if you can dial it in further. Do the same with your listening position. Much easier as all you need is to prop up a tape measure and set the mic tripod along it to bang out measurements at whatever increment/distance you desire.