Manual Response Testing - All 5.1 Channels

[pcasper]

Hello to all,

Preliminary searching has not revealed a solution to my problem...I hope someone here can help.

I use REW regularly to test and tune up my 5.1 system. I equalize the front L+R channels manually with the Audessey eq. function in my Integra DTC 9.8 processor. I inject the sweep from my laptop external soundcard via the analog Auxilliary input on the Integra front panel. This input is digitized, processed, equalized, converted to analog again and passed out to my external L+R amp. However, I am regularly frustrated trying to test the center, surround and sub channels, because there seems to be no way to inject the analog test signal into each channel such that it is processed in the same manner as the front L+R channels. I can use the analog multichannel inputs to drive each channel separately, but this bypasses the internal processing and equalization so all I can do is test but not equalize and retest.

I have gotten around this limitation so far, for instance, by driving the Left front channel, connecting the center speaker to the L channel amp, nulling the left channel equalization and readjusting the equalization for the center channel. Then I have to transfer the equalization settings to the Audessey center channel, restore the left channel settings, reconnect the speakers correctly, and hopefully I am done. The process is repeated for the surround and sub channels. It's a pain, it works, but there has to be an easier way.

Ideally, I envision a laptop-based software program that outputs a 5.1 encoded digital stream, with the test signal injected into the desired channel. It would be wonderful if REW did this.

I have a feeling that there is in fact an easy and fairly obvious way to do this, which I have been too dense to discover. If anyone here can enlighten me, I would be grateful and hopefully not too embarrassed!

I know I could just let Audessey do it all automatically, but the automatic function does not work well in my system, and I prefer to do it manually anyway, especially when I want to create a non-flat response, or I want to hear the effect of an adjustment immediately.


Thanks for any help,

Paul

[brucek]

It's a pain, it works, but there has to be an easier way.

Not that I'm aware of.........

brucek

[atledreier]

What's the technical reason why REW can't output a 5.1 bitstream?

[brucek]

What's the technical reason why REW can't output a 5.1 bitstream?

You would require a DD or DTS encoder licensing agreement, and that ain't cheap. On top of that, and the real show stopper, is that licenses are only available to companies that fulfil the licensing terms and whose products go through the verification and approvals processes. Licenses are not available to individuals.

This is an analog mono signal application for testing response. You have to get creative to do multichannel.......

brucek

[atledreier]

How about those that have a HDMI output in their computer that will also output audio. Many laptops have this already, and most newer ones will in the future. Could you output multichannel PCM over HDMI if the hardware allow it?

[brucek]

And how would you calibrate the analog line-in channel that accepts the analog SPL meter?

brucek

[pcasper]

Well, at least I did not miss something obvious! Thank you for your reply. I will just keep doing it the hard way.

On a side note, is anyone aware of a test cd or dvd that generates sustained full-band pink noise in each channel? The Essentials and Avia disks don't do it as far as I know, except maybe for the front L+R channels. You could just use the spectrum analysis feature of REW with this disk, but you would have to negate the soundcard calibration unless you could figure out a way to calibrate only the receive side.

Anyway, I want to take this opportunity to thank brucek and anyone else that has contributed to the development of REW. This tool is absolutely fantastic and I just marvel at it's capabilities every time I use it. I am a grizzled old retired engineer and I remember when we had to do everything on a slide rule, so the technology available today boggles my mind. You guys deserve a special place in the audio hall of fame.

Paul

[thewire]

pcasper wrote:

Well, at least I did not miss something obvious! Thank you for your reply. I will just keep doing it the hard way.

On a side note, is anyone aware of a test cd or dvd that generates sustained full-band pink noise in each channel? The Essentials and Avia disks don't do it as far as I know, except maybe for the front L+R channels. You could just use the spectrum analysis feature of REW with this disk, but you would have to negate the soundcard calibration unless you could figure out a way to calibrate only the receive side.

Anyway, I want to take this opportunity to thank brucek and anyone else that has contributed to the development of REW. This tool is absolutely fantastic and I just marvel at it's capabilities every time I use it. I am a grizzled old retired engineer and I remember when we had to do everything on a slide rule, so the technology available today boggles my mind. You guys deserve a special place in the audio hall of fame.

Paul

I used the blu sky test setup CD. After two days of calibration of volatages and levels I get this at the location next to ears.



I used Pink Noise fb to calibrate everything using the RTA in REW. After calibrating voltages, then changing them based on the difference between toslink (digital) and analog that I measured in my pre/pro, and based on the fact that my last AVR was damaged by full range analog input from my source.

This gave me a -10 setting on my analog source and 0 for the sub. I placed the mic at arms length between my left and right speakers and measured each channel at a time.

I played the full bandwidth pink noise for each channel without the sub and set them to 85dBc, ignoring that my RS Meter wanted to measure higher due to the strange looking peak around 3Khz. This lined it up above 70 in the RTA. I then calibrated the sub to +10dB higher in 1/3 octave using the RTA, which places it around 4dB higher on the dBFS measurement of the input that is near the RTA check box. The RS meter is not the best tool for such calibration by the way and you should be using a full range mic. I placed my surrounds at 82dBFS becuase I wanted to try it with Dolby Specs.

After all this I go back and measure with my RS meter each channel, this time turning on the sub output in my XA2 because the THX optimizer sub noise will not measure the crossover sub out in my pre/pro using it's internal crossover and full range signal from the XA2, and I measure 74dBc - 75dBc for the sub channel, and 74dBc -75dBc for the other channels. My pre/pro was at that time at -10.

Here are the test files I used.

http://www.abluesky.com/asp/catalogue/catalogue.asp?linkid=143

[au-734]

brucek wrote:

And how would you calibrate the analog line-in channel that accepts the analog SPL meter?

brucek

Wouldn't an analog pre-out on the rear of the AVR work assuming all signal processing in the AVR is off?

My Denon has 7.1 in but it does not go through an A/D/A loop so it is not easy to see how Audyssey adjusts the frequency response for the side and rear speakers. It is easy enough to work on the front left and right using stereo inputs, the side and rears are much more complicated.

Thanks for creating a great tool. Was this someone's graduate thesis project?

Cheers,

jr

[brucek]

Wouldn't an analog pre-out on the rear of the AVR work assuming all signal processing in the AVR is off?

The problem with using digital-out and analog-in to a soundcard is that the analog input requires its own calibration, which simply isn't possible. It's like one hand clapping - it doesn't work.

Either way, I don't think John is considering HDMI 5.1 PCM bitstream output for REW. The concentration is on analog I/O to test subwoofers and mains.....

brucek