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Discussion Starter · #1 ·
I'd like to request a so-called "time locking" feature for some future version of REW. This feature as implemented in HolmImpulse is discussed briefly in a thread in the PartsExpress forum.

Although the discussion in that thread is centered around driver time alignment in loudspeaker design, my reason for requesting this feature is different. I am writing some software that I will offer for free, dealing with automated optimization of multiple subwoofer setups with individual EQ of each subwoofer using devices like the miniDSP. It will be available sometime next year. Earl Geddes describes the optimization idea in a video and its accompanying PowerPoint presentation.

If all goes well, the software should work fine using REW measurement setups having XLR microphones and separate USB sound adapters, provided that a loopback timing reference is used. But I've noticed that the newer USB microphones are becoming very popular now. However, these eliminate the possibility of a loopback timing reference AFAIK, causing the situation discussed in the HTS thread "Can REW predict 2sub performance from single sub measurements?".

Without this feature, I'd have to tell people that they'd need to buy a mic and USB adapter, which won't go over well if they already have one, especially so if they have gone to the extra expense of getting an individually calibrated one from CSL or a similar outfit. I don't want to tell people to use HolmImpulse, as I consider REW to be the de facto standard for many reasons. A "time lock" feature in REW would eliminate the need and expense of purchasing another mic and a USB adapter.

Thanks for reading.
 

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I'd like to request a so-called "time locking" feature for some future version of REW. This feature as implemented in HolmImpulse is discussed briefly in a thread in the PartsExpress forum.

Although the discussion in that thread is centered around driver time alignment in loudspeaker design, my reason for requesting this feature is different. I am writing some software that I will offer for free, dealing with automated optimization of multiple subwoofer setups with individual EQ of each subwoofer using devices like the miniDSP. It will be available sometime next year. Earl Geddes describes the optimization idea in a video and its accompanying PowerPoint presentation.

If all goes well, the software should work fine using REW measurement setups having XLR microphones and separate USB sound adapters, provided that a loopback timing reference is used. But I've noticed that the newer USB microphones are becoming very popular now. However, these eliminate the possibility of a loopback timing reference AFAIK, causing the situation discussed in the HTS thread "Can REW predict 2sub performance from single sub measurements?".

Without this feature, I'd have to tell people that they'd need to buy a mic and USB adapter, which won't go over well if they already have one, especially so if they have gone to the extra expense of getting an individually calibrated one from CSL or a similar outfit. I don't want to tell people to use HolmImpulse, as I consider REW to be the de facto standard for many reasons. A "time lock" feature in REW would eliminate the need and expense of purchasing another mic and a USB adapter.

Thanks for reading.
Sounds good

So what you are saying is the time aligning would be able to be done with a USB mic e.g. UMIK-1, UMM-6?
 

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Discussion Starter · #3 · (Edited)
So what you are saying is the time aligning would be able to be done with a USB mic e.g. UMIK-1, UMM-6?
Yes, that's the idea.

If such a feature were implemented, the answer to the question "Can REW predict 2-sub performance from single sub measurements?" would be "Yes, provided that you choose 'Set t=0 at IR peak' in Analysis Preferences for the first measurement, then enable time locking for subsequent measurements".

Edit: Add "or use loopback as a timing reference with a separate XLR mic and USB adapter" to the above.
 

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Yes, that's the idea.

If such a feature were implemented, the answer to the question "Can REW predict 2-sub performance from single sub measurements?" would be "Yes, provided that you choose 'Set t=0 at IR peak' in Analysis Preferences for the first measurement, then enable time locking for subsequent measurements".
Sounds really good.

This could be done with main speakers as well not just subs?

Interesting to se what John thinks.
 

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Discussion Starter · #5 ·
As far as the integration of mains to subs, yes. Of course, the higher the frequency, the more sensitive the phase becomes to mic position. I have only done measurements to 200 Hz, so I don't have experience related to finding the frequency above which phase matching becomes impractical.
 

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As far as the integration of mains to subs, yes. Of course, the higher the frequency, the more sensitive the phase becomes to mic position. I have only done measurements to 200 Hz, so I don't have experience related to finding the frequency above which phase matching becomes impractical.
That would have merit if you could do higher frequencies than 200hz.
 
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