SongTowers FR Question (not flat from 1k-20khz) with RoomEQ

DMurphy · « **Reply #60 on:** 27 Jun 2009, 03:02 pm »

Yup--it's old school, but it works. Unfortunately, most tuners don't seem to have defeatable interstation hiss controls anymore. If I want to spot a frequency response issue quickly, I just tune between stations on my trusty Marantz 2100 and compare.

avahifi · « **Reply #61 on:** 27 Jun 2009, 03:27 pm »

Actually I use a test CD with tracks I have compiled from several sources.

Several are white noise and various square waves I normally use for DAC testing, along with an all bits turned on 20KHz sine wave and a couple of zero dB tracks too for noise testing.

I can make you a copy if you wish, Dennis.

You will be amazed to see how bad most CD players and DACs are on the square waves, clipping and tons of distortion is the norm.

Regards,

Frank Van Alstine

Nuance · « **Reply #62 on:** 27 Jun 2009, 06:36 pm »

Quote from: avahifi on 27 Jun 2009, 03:27 pm

You will be amazed to see how bad most CD players and DACs are on the square waves, clipping and tons of distortion is the norm.

Regards,

Frank Van Alstine

Really? Yikes!

Can you recommend a good DAC that doesn't perform poorly on the square wave test? I'd like to get one for my squeezebox eventually.

zybar · « **Reply #63 on:** 27 Jun 2009, 06:39 pm »

Quote from: Nuance on 27 Jun 2009, 06:36 pm

Quote from: avahifi on 27 Jun 2009, 03:27 pm

You will be amazed to see how bad most CD players and DACs are on the square waves, clipping and tons of distortion is the norm.

Regards,

Frank Van Alstine
Really? Yikes!

Can you recommend a good DAC that doesn't perform poorly on the square wave test? I'd like to get one for my squeezebox eventually.

What do you think he is going to recommend??

Here are some measurements for a stock Transporter:

http://www.stereophile.com/computeraudio/207slim/index4.html

George

avahifi · « **Reply #64 on:** 28 Jun 2009, 03:11 pm »

Nuance, all you need is a copy of my test CD and a decent dual trace scope. Play the square wave tracks on a variety of CD players and DACs and note that the problems you will see are really nasty on many units.

No opinions or debate required about this after you make the tests.

Regards,

Frank Van Alstine

Nuance · « **Reply #65 on:** 28 Jun 2009, 04:52 pm »

Quote from: zybar on 27 Jun 2009, 06:39 pm

Quote from: Nuance on 27 Jun 2009, 06:36 pm
Quote from: avahifi on 27 Jun 2009, 03:27 pm

You will be amazed to see how bad most CD players and DACs are on the square waves, clipping and tons of distortion is the norm.

Regards,

Frank Van Alstine
Really? Yikes!

Can you recommend a good DAC that doesn't perform poorly on the square wave test? I'd like to get one for my squeezebox eventually.

What do you think he is going to recommend??

Here are some measurements for a stock Transporter:

http://www.stereophile.com/computeraudio/207slim/index4.html

George

His own stuff, I'd imagine. I forget he offered DAC's. DOH! I'll be getting one of his then, down the road.

I cannot afford the Transporter, but thanks for the links to the measurements.

Nuance · « **Reply #66 on:** 28 Jun 2009, 04:54 pm »

Quote from: avahifi on 28 Jun 2009, 03:11 pm

Nuance, all you need is a copy of my test CD and a decent dual trace scope. Play the square wave tracks on a variety of CD players and DACs and note that the problems you will see are really nasty on many units.

No opinions or debate required about this after you make the tests.

Regards,

Frank Van Alstine

True true. Well, I assume you engineer your DAC's so they don't have this issue, which is why I'll buy one of yours when finances permit. Speaking of which, what is the main difference between the Ultra and Insight DAC? I'll probably go with the Insight unit, but I'd at least like to know.

rahimlee54 · « **Reply #67 on:** 28 Jun 2009, 05:29 pm »

Quote from: avahifi on 28 Jun 2009, 03:11 pm

Nuance, all you need is a copy of my test CD and a decent dual trace scope. Play the square wave tracks on a variety of CD players and DACs and note that the problems you will see are really nasty on many units.

No opinions or debate required about this after you make the tests.

Regards,

Frank Van Alstine

Is there somewhere we could get a copy of this test cd? I'd like to try it out around my house.

Thanks

Art_Chicago · « **Reply #68 on:** 28 Jun 2009, 06:27 pm »

Quote from: Nuance on 28 Jun 2009, 04:54 pm

Quote from: avahifi on 28 Jun 2009, 03:11 pm
Nuance, all you need is a copy of my test CD and a decent dual trace scope. Play the square wave tracks on a variety of CD players and DACs and note that the problems you will see are really nasty on many units.

No opinions or debate required about this after you make the tests.

Regards,

Frank Van Alstine
True true. Well, I assume you engineer your DAC's so they don't have this issue, which is why I'll buy one of yours when finances permit. Speaking of which, what is the main difference between the Ultra and Insight DAC? I'll probably go with the Insight unit, but I'd at least like to know.

there was an AVA Insight+ DAC on A'gon for 650 or so. Lasted less than a day, so I missed it. OITP got T-8 DAC for that cheap from ebay.
In case Frank does not see this post, Ultra uses tubes for voltage and mosfet for current if I am not mistaken.

avahifi · « **Reply #69 on:** 29 Jun 2009, 05:51 pm »

Now, if somebody out there who knows a lot more about computers than I do will help me, here is what I would like to do.

Upload my test CD (uncompressed) up here somewhere where anyone who wants to download it and burn their own test CD from it can do that.

I use a Mac computer (OS10.4) and this stuff is a bit more complex than my pay grade allows. Very clear step by step distructions are required.

Regards,

Frank Van Alstine

jsalk · « **Reply #70 on:** 29 Jun 2009, 08:01 pm »

Quote from: avahifi on 29 Jun 2009, 05:51 pm

Now, if somebody out there who knows a lot more about computers than I do will help me, here is what I would like to do.

Upload my test CD (uncompressed) up here somewhere where anyone who wants to download it and burn their own test CD from it can do that.

I use a Mac computer (OS10.4) and this stuff is a bit more complex than my pay grade allows. Very clear step by step distructions are required.

Regards,

Frank Van Alstine

Frank -

If you want to send me a copy, I can create an .iso file that can be used to burn copies. I can then post it for anyone to download.

- Jim

Nuance · « **Reply #71 on:** 29 Jun 2009, 09:32 pm »

^ That would be great!

Thanks to Jim and Frank.

avahifi · « **Reply #72 on:** 3 Jul 2009, 08:04 pm »

Jim and Mary Salk visited me a couple of days ago so we could play the HT3s with the little Ultravalve 60 prototype amplifier. It was interesting and great to see them in person again.

I did give Jim a copy of my test CD with the white noise and square wave tracks, along with some music tracks I listen to. Jim says he will be able to post it on the web for any to download and burn test CDs for themselves.

I have to write some notes as to how to best use the CD and I will do that early next week.

Happy 4th.

Frank Van Alstine

audiocrazy · « **Reply #73 on:** 22 Jul 2009, 05:53 pm »

Sorry it took long but I've taken few measurements with the calibrated mic. I got the mic calibrated from 5Hz-25Khz and got narrow band measurement file for both 0 degree and 90 degree mic positions.
The 1st measurement is 0 degree and 2nd with 90 degree using both speakers. As you can see there is a huge variation in higher frequency. I'll post individual speaker measurements later.
The solid black line is from mic calibration file.

Nuance · « **Reply #74 on:** 22 Jul 2009, 06:08 pm »

You aren't still using a calibration file from Home Theater Shack, are you? Since you had the mic professionally calibrated, I'd imagine you don't need to use any calibration file with REW.

Anyway, the second graph looks better through the HF's. That's 90 degrees off-axis?

DMurphy · « **Reply #75 on:** 22 Jul 2009, 06:09 pm »

I'm still not quite following this. What does the 0 vs 90 mic setting refer to?

Nuance · « **Reply #76 on:** 22 Jul 2009, 06:13 pm »

Quote from: DMurphy on 22 Jul 2009, 06:09 pm

I'm still not quite following this. What does the 0 vs 90 mic setting refer to?

Wondering the same thing. I am guessing axis?

If the HF's are better "off-axis," toe your speakers in more toward you, audiocrazy. Then measure again. Also, like I said, don't use any mic calibration file through REW.

audiocrazy · « **Reply #77 on:** 22 Jul 2009, 06:22 pm »

Quote from: DMurphy on 22 Jul 2009, 06:09 pm

I'm still not quite following this. What does the 0 vs 90 mic setting refer to?

0 degree means the mic is pointing towards ceiling when taking measurement
90 degree means the mic is pointing towards speaker.

Brandon when the mic is calibrated you get a calibration file that you use instead of generic calibration file. Each mic has different freq response and when the mic is calibrated you get an offset value to the freq where the mic has a varation from the normal response.
Here are the individual measurements of L & R speakers with 90 degree mic position.
Blue is Right and Purple is Left

Here are the individual measurements with 0 degree mic position

DMurphy · « **Reply #78 on:** 22 Jul 2009, 07:43 pm »

OK So it looks like we're making progress. I assume from the deviations between the two speakers that you haven't moved the speakers next to each other for the individual measurements?

Nuance · « **Reply #79 on:** 22 Jul 2009, 08:02 pm »

Quote from: audiocrazy on 22 Jul 2009, 06:22 pm

0 degree means the mic is pointing towards ceiling when taking measurement
90 degree means the mic is pointing towards speaker.

Brandon when the mic is calibrated you get a calibration file that you use instead of generic calibration file. Each mic has different freq response and when the mic is calibrated you get an offset value to the freq where the mic has a varation from the normal response.

Gotcha. Good to know, thanks.

Well, technically you are suppose to place the mic at the listening position pointed straight up at the ceiling (zero degrees, as you called it). This will be the listening position measurement, while the other can be considered an on-axis measurement (90 degrees, as you called it). Based on that logic I'd say you need to toe the speaker in more. How much toe-in were you using when you took the above measurements?

Obviously the graph below is the better of the two concerning high frequencies.