Properly using sweep files with acoustic timing reference in cars

[El Duderino]

I have a good deal of experience using the RTA function of REW, but I am looking at learning the impulse response process for car audio. My typical process is to confirm polarity, enter crossover filters, measure distances and enter them to determine delay, then measure each driver amplitude response individually, use level and EQ to make the far side hit my target curve, then make the near side match the far side in level and response. Finally, I measure amplitude with all drivers playing and look for cancellations which indicate timing errors or problems with the input signal (i.e., the OEM signal is using phase processing and this fact wasn't detected initially, so L and R channels are not in phase at all frequencies). I've been very happy with this process and have tuned literally hundreds of car audio systems this way.

The only reason I'm looking at taking the impulse response measurement now is that some products are now able to load REW EQ recommendations, and I am being asked how to do it. The last time I tried taking impulse response measurements, it was in the electrical domain and it was pre-acoustic timing reference capability (went in the AUX of the OEM head unit). Many OEM systems lack analog AUX inputs today, so the only way to do it is with the acoustic timing reference. I see the value of an auto-EQ process measuring phase, but since this is a relatively recent addition to the software, I'm failing to determine through reading the help file the proper way to use the acoustic timing reference track when measuring a fully-active stereo system where I can mute and measure each driver individually. Any assistance is appreciated.

 

[Sonnie]

Welcome to AV NIRVANA

I believe what you are looking for is near the bottom half of this thread... which discusses using REW's acoustic timing reference tracks.

miniDSP C-DSP 8x12 DL Tuning Step by Step Guide

I created a thread back in August 2019 on tuning my 2019 RAM with the miniDSP C-DSP with DL, but several things have changed since then, and I decided I'd do another write-up on how I've tuned my 2020 RAM truck. Disclaimer: This is not chiseled in stone by any means, and it's not necessarily...

www.avnirvana.com

As far as measuring each individual driver, you have to mute the other drivers within your DSP software... OR... unplug the cables on the amp channels that you don't want to measure, if you don't have the ability to do this in the software. With the miniDSP unit I use, I can mute all the channels within the software program.

 

[El Duderino]

Apparently part of the problem is, you have to use the latest Beta, and NOT be restricting yourself to non-beta versions, because the help file content on this matter is only going to be in the beta version. Deleted off one of my machines and installed the beta today, I can see that there's more content there to go through!