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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Audio Measurement and Testing => Topic started by: Hayden J. Nebus on August 11, 2017, 11:42:37 am

Title: Smaart 7 measurement delay limit?
Post by: Hayden J. Nebus on August 11, 2017, 11:42:37 am
Anyone know how much receive delay you can put on a Transfer measurement channel is smaart7?

I'm on windows with 8Gb RAM if it matters. This would be a electronic, not acoustic, measurement of two asynchronous, nominally coherent sources.

Just for grins a colleague in the R/E/P side of the biz wants to compare a few mastered wavs to some QC test pressings from the record plant. Only challenge I could think of is that it's a tall order to precisely time a needle drop.     
Title: Re: Smaart 7 measurement delay limit?
Post by: Erik Jerde on August 11, 2017, 12:23:37 pm
If my memory serves I believe you can use wav files in smaart.  Why not just record the output then line up and compare?
Title: Re: Smaart 7 measurement delay limit?
Post by: Mac Kerr on August 11, 2017, 01:34:52 pm
If my memory serves I believe you can use wav files in smaart.  Why not just record the output then line up and compare?

^^^This^^^   You're going to have an AD conversion anyway to get into Smaart, why not just make it at the recording stage. Compare the 2 recordings. You will still have the needle drop and all the other vinyl artifacts.

Mac
Title: Re: Smaart 7 measurement delay limit?
Post by: Hayden J. Nebus on August 11, 2017, 05:45:14 pm
If my memory serves I believe you can use wav files in smaart.  Why not just record the output then line up and compare?

Because I'm looking to blow an afternoon, not a week :-)

Another consideration is that the device under test is a system containing the playback rig as much as the plant, with a transducer and filter network at each end.

 I was thinking a couple of preamps and a handful of cartridges would produce a decent set of data that could be collected fairly quickly in near real-time.
Title: Re: Smaart 7 measurement delay limit?
Post by: Mark Wilkinson on August 11, 2017, 06:10:05 pm
Because I'm looking to blow an afternoon, not a week :-)

Another consideration is that the device under test is a system containing the playback rig as much as the plant, with a transducer and filter network at each end.

 I was thinking a couple of preamps and a handful of cartridges would produce a decent set of data that could be collected fairly quickly in near real-time.

According to manual, the default FFT size 64K, is good for about 440ms.  If you increased FFT to the max 512K, that should be good to about 3.5 sec.
Title: Re: Smaart 7 measurement delay limit?
Post by: Mac Kerr on August 11, 2017, 06:23:12 pm
Because I'm looking to blow an afternoon, not a week :-)

Another consideration is that the device under test is a system containing the playback rig as much as the plant, with a transducer and filter network at each end.

 I was thinking a couple of preamps and a handful of cartridges would produce a decent set of data that could be collected fairly quickly in near real-time.

I'm not getting why recording is an issue. You have a test pressing, you can record the preamp out from the playback turntable, or a mic of the full audio chain complete with speakers. The only additional time involved is the length of the recording, which you now have to play twice, once to record, once to analyze. In either case you are going to be digitizing the DUT, as the reference has been digitized, in order to get it into Smarrt so that seems a wash.

If it must be done live you can find a cue point in the master where you can start it in near sync with the DUT, but it may take a few tries to get the out of sync time within the usable window. If you need more than 2 tries recording will be faster and give you the option to repeat the test quickly for as many looks as you want.

Mac
Title: Re: Smaart 7 measurement delay limit?
Post by: Frank Koenig on August 12, 2017, 11:43:00 am
Hi Hayden,

With respect to delay: what others have said. What I wonder is if you will get sufficient coherence for a meaningful measurement with an LP recording in the signal chain. Records introduce artifacts, such as time variation (wow), that are essentially absent from the signal chains we unusually measure with Smaart. I'm guessing you will need to use A LOT of averaging, and might find that other tools are better suited to the purpose.  Interesting project, and please tell us how it turns out.

--Frank
Title: Re: Smaart 7 measurement delay limit?
Post by: Don T. Williams on August 12, 2017, 04:21:05 pm
I'm with Frank and his thoughts on this. Even with a strobe to indicate speed on the turntable, I wonder how close it stays to 33 & 1/3 RPM for the length of the recording.  And that was a two part process, the cutting lathe and the turntable playback.  I'm sure you can visually line up a starting point, but my guess is the timing (and synchronization) between the two will change over the length of the recording.  Maybe not a lot, but some.  This is just a guess, and that may not make any difference for what you are trying to do.  As Frank stated: interesting project.