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After several changes in setup and room treatment I want to re-EQ my system. I'm running 2ch with 2 subs integrated into a single virtual sub. using REW and MiniDSP SHD Studio. My original setup sounded great but I made at least 2 mistakes:
Mixing XO types between subs and mains, and
EQing subs individually, then setting timing and summing them
The XO part is easy and makes sense to me. As for sub EQing, I now understand that this order is wrong --> First do time alignment, then level match, sum subs and EQ summed subs. Can anybody confirm that this is the right way? Any comments much appreciated. Thanks and cheers,
I mostly agree with this procedure, and it is very similar to what I did in my previous setup with good results. (I have Dirac ART now.)
What I would suggest is to start with level matching, then look at time alignment. I would start with the subs playing the exact same signal, i.e. zero relative delay. Try to apply some delays to one of the subs in steps - positive and negative - to see if the summed response improves. Also look at the decay graph or waterfall. Choose the delay that looks best.
I see that some people try to set a time delay for subs based on impulse responses. That is a flawed procedure, in my opinion.
I mostly agree with this procedure, and it is very similar to what I did in my previous setup with good results. (I have Dirac ART now.)
What I would suggest is to start with level matching, then look at time alignment. I would start with the subs playing the exact same signal, i.e. zero relative delay. Try to apply some delays to one of the subs in steps - positive and negative - to see if the summed response improves. Also look at the decay graph or waterfall. Choose the delay that looks best.
I see that some people try to set a time delay for subs based on impulse responses. That is a flawed procedure, in my opinion.
I figure delays using REW appointment tool and confirm in steps. But that's not the question, which is: EQ subs individually and then sum OR time align, sum and then EQ the new "virtual sub"?
1. Apply XO's, if any to the subs FIRST. XO's rotate phase and will change the time/phase alignment.
2. Make sure your mic is properly centred over the listening position. See my eBook in my sig for two procedures for mic centring. Sweep both speakers together, call this "L+R".
3. Time align each sub to "L+R" to remove any delays that are greater than half a period (half a period = 180 deg phase rotation)
4. Phase align the first sub to "L+R" to remove as many dips in the FR as possible. Call the summation "Sub1+L+R"
5. Phase align the second sub to Sub1+L+R, call the summation "Sub1+Sub2+L+R". If you have additional subs, keep adding them and check the summation every time.
6. Adjust volume and EQ to remove any peaks.
Note that time alignment and phase alignment both involve setting delays. The question is "how much delay is audible?". Current research does not answer the question about the threshold of group delay audibility, but a rule of thumb is that it is probably > half a period T (or even one period!) of the frequency in question. So my suggested time alignment threshold of <0.5T should be inaudible.
Keith,
Thanks much, but can you clarify 6? After all that alignment am I EQing the whole thing at once? Or individual speakers? This is what's unclear to me. Cheers,
Keith,
Thanks much, but can you clarify 6? After all that alignment am I EQing the whole thing at once? Or individual speakers? This is what's unclear to me. Cheers,
I essentially agree with @Keith_W's above comments and suggestions in his post #4.
In addition to @Keith_W's points, let me share a few important points as follows.
1. Generally speaking, all the DSP tuning factors/parameters in upstream digital domain, I mean XOs (filter types, slopes, XO-Fqs, Phases), Delays=Time Alignments, various EQ parameters, as well as Relative Digital Gains, etc., are more or less interdependent with each other, and hence we always have possibilities of getting into endless tuning spirals/pit-holes.
2. Frequent Gain tuning/change in DSP would increase possibilities of accidental/by-mistake damages for your treasure SP drivers. For example, if you misinput numerically typing gain increase of "+30 dB" instead of your intending "+3.0 dB", you would have damage or destroy your specific SP driver. I highly recommend you not to use numerical value typing-in for gain change, but you should use mouse-wheel up/down of 0.1 dB granularity if available in your DSP software, like DSP "EKIO" which I have been using throughout my DSP-based multichannel audio project.
3. Any of misinput/mistyping of XO Fq would also damage/destroy your midrange, tweeter, and/or super-tweeter. To avoid this risk, I recommend you using proper serial HiFi grade protection capacitors for these SP drivers, at least while your try-and-error tuning period. I myself, always use such protection capacitors all the way, of course after having confirmation of transparency and no sound-degradation at all with the capacitors in the Fq zones covered by the SP drivers.
As for the above point 2., i.e. relative gain control/tuning among the multiple SP drivers, my personal approach of utilizing the "best combination" of "DSP configuration in digital domain" and "analog domain tone controls using HiFi-grade preamplifiers and/or integrated amplifiers" would be of your reference and interest, I assume. In my post #931 on my project thread, I wrote as follows under the below spoiler cover.
I recently wrote again in my post #56 on a remote thread like these; Yes, as for safe and flexible tone controls (or I can say "relative gain controls among the multiple SP drivers"), my stance (policy) at least, is that we are encouraged to utilize the "best combination" of "DSP configuration in digital domain"and "analog domain tone controls using HiFi-grade preamplifiers and/or integrated amplifiers".
We need to note (and to respect for) that analog domain tone controls (relative gain controls among the multiple SP drivers) give no effect nor influence at all on the upstream DSP configuration (XO/EQ/Gain/Phase/Polarity/Group-Delay). I believe that this is a great merit of flexible tone controls in analog domain. We know well, on the other hand, in case if we would like to do the "tone/gain controls" only within DSP configurations, such DSP gain controls always affect more-or-less on "XO" "EQ" "phase" and "delay" of the DSP settings which will leads you to possible endless DSP tuning spirals every time; within DSP configurations, XOEQGainPhase and Delay are always not independent with each other, but they are always interdependent/on-interaction.
Just for your possible reference, my DSP-based multichannel multi-SP-driver multi-amplifier active system has flexible and safe analog level on-the-fly relative gain controls (in addition to upstream on-the-fly DSP gain controls) for L&R subwoofers, woofers, midrange-squawkers, tweeters, and super-tweeters, all independently and remotely. My post here shows you a typical example case for such safe and flexible on-the-fly analog-level tone controls. This my post(as well as this post) would be also of your interest.
By the way, the procedure I gave is for mono bass. I am aware from one of your previous threads that your subwoofers are in front and behind the listening position. If you wanted stereo bass, the EQ procedure is different.
I figure delays using REW appointment tool and confirm in steps. But that's not the question, which is: EQ subs individually and then sum OR time align, sum and then EQ the new "virtual sub"?
You should EQ the summed response, not the subs individually. The reason is that the subs work together to combat offensive modes. If you EQ individually, they will lose that ability.
You will find all the details in Floyd Toole’s Sound Reproduction. In the 4th Edition, it’s in Section 14.5.
By the way, the procedure I gave is for mono bass. I am aware from one of your previous threads that your subwoofers are in front and behind the listening position. If you wanted stereo bass, the EQ procedure is different.
You should EQ the summed response, not the subs individually. The reason is that the subs work together to combat offensive modes. If you EQ individually, they will lose that ability.
You will find all the details in Floyd Toole’s Sound Reproduction. In the 4th Edition, it’s in Section 14.5.
@Keith_W Your memory is right, mono bass @janbth Right, finally got it
Thanks, all clear. As an aside, I'm amazed how good it sounded despite being wrong! I look forward to hearing what it should have been all along. Cheers,
