Home Theater Forum and Systems banner

1 - 17 of 17 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Hi all,

I'm new to the forum (first post) and pretty new to REW.
I started using REW a few weeks ago on a W10 based laptop using a Behringer UCA222 external sound card + a switch box to measure speaker impedance and T/S parameter. I was able to get fairly good results on some small 4" mid ranges laying around.

I recently bought a new Macbook Pro (2016) with macOS Sierra installed - will REW work on it? (I saw support until OSX 10.11)

Additionally, I would like to measure T/S specs of a subwoofer (a pretty big one) - do I just add an amp between the sound card and the sense resistor as well as a voltage divider on the soundcard inputs?



Thanks,

David
 

·
Premium Member
Joined
·
6,711 Posts
Should work fine of 10.12 but you may need to set the replay buffer size to 16k in the REW soundcard preferences.

You can measure sub drivers with a PC headphone output, but an amp and appropriate dividers will give better results.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #3
Thank you for a quick response, John.

I'll find some time to test over the weekend and report back with experience.
 

·
Registered
Joined
·
42 Posts
Thank you for a quick response, John.

I'll find some time to test over the weekend and report back with experience.
Any update on this Kinser? I tried on my computer running Sierra and it wouldn't download. I don't remember the reason stated, but it worked fine on Capitan. Thanks
 

·
Registered
Joined
·
42 Posts
Any update on this Kinser? I tried on my computer running Sierra and it wouldn't download. I don't remember the reason stated, but it worked fine on Capitan. Thanks
Ok, scratch that. I just tried again and it worked. At first it was doing the same thing- it didn't seem to actually download tthe file and did not create a disk image, but instead under downloads there was just a file that the computer didn't know how to open. Kinda weird, but it seems to be working fine.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #6
Hi satx,

I had no issues downloading, installing or running REW on sierra so far and it seems to run very stable with no issues.

My sound card calibration and impedance testing is a different story though - can't seem to get realistic readings.
I purchased a Behringer UCA222 online that turned out to be a fake, but it works and is pretty clean for what it is.
I've ordered some cheap eBay TDA2030 kits to build a simple 5-10W amp to provide a solid signal for testing subwoofers. I'll then rebuild my jig with some ceramic resistors I have laying around. Hopefully this will yield better results.

Cheers,

David
 

·
Registered
Joined
·
42 Posts
Hi Kinser,

Thanks, it's working for me just fine too.

How do you know that the results you're getting aren't realistic? Are they not repeatable or something? Did you read the help file to do the various calibrations?

If your resistor is off then your impedance will be off too, but it shouldn't be unrealistic looking, just slightly inaccurate. I use something like this http://www.digikey.com/product-detail/en/riedon/101-100RX/696-1546-ND/4832931

The hardest part I've found with making spl readings is getting the computer's soundcard settings correct, but it's a lot easier, for me anyways, on a Mac.

Let me know if I can try to help
 

·
Registered
Joined
·
9 Posts
Discussion Starter #8
I'm seeing inconsistent reading each time I measure the same driver.

I think my current jig may have a dry solder spot somewhere and above that, a friend took my DMM and has yet to return it, so I have no way of testing it.
Its also hard to rely on the internal headphone amp in the sound card to provide a sufficient signal for a 2kw subwoofer when wired to a 1 ohm load.

I've used Dayton DAT's (belongs to a friend) to provide the first batch of t/s parameters, but after a break in, I want to remeasure at home, with my mac :)

I'm not doing any SPL measurements at the moment, might incorporate the hardware in the future if I see a need for it.
 

·
Registered
Joined
·
42 Posts
Ok, in that case there's definitely something wrong. Have you tried adjusting your soundcard settings? And why don't you just reflow the solder joints? Also, are you sure that your jig is wired correctly?

Have you tried measuring the subwoofer with the headphone out? If it doesn't go into protect then I think you should be fine for basic impedance measurements. I've found that my mac computer's internal amp seem to have more power than the internal in my Windows computers.

I honestly never trust my own T/S measurements using rew, so I don't think I can help too much. I use it for impedance and spl sweeps only. You need to either build a test box for the driver under test and know the volume very accurately or add accurate weight to the cone to get you Vas figure. Also, the numbers will be level dependent from what I understand, so you will likely get different results at different volume settings.

Also, Frequency measuerments are where it's at really. The T/S values are necessary to design a proper enclosure, but after that, you will probably want to see and adjust the actual FR in your room. I use a very simple setup consisting of a Dayton mic with cal file and a little Bheringer mic preamp; about $100 total and well worth it.

Evan
 

·
Registered
Joined
·
9 Posts
Discussion Starter #10
I'm not sure what soundcard settings I can adjust on the mac, but I've tried both outputs on the UCA222 and I still suspect a problematic jig.

I'm mainly into car audio, so I have an SLP LAB meter that I use for measuring in cabin SLP. The Dayton mic might come in handy when setting up the front stage as I am working with an 8ch DSP with 31 band EQ per channel.

I'll redo the jig with the TDA2030 as well as a 33 ohm 25w sense resistor (this is what I have laying around) and see how it goes.
 

·
Registered
Joined
·
14 Posts
I hope this is an appropriate thread for this question...

I've been running a freshly downloaded version of REW on a MacBook Pro, using an external mAudio usb interface for the mic, and the laptop's toslink output via a miniDSP openDRC-DA8 for the stimulus, and getting inconsistent results. Perhaps I just need to adjust some default setting in the preferences? Buffer size?

Some frequency response measurements work fine, but roughly half yield truncated high frequency measurements (it looks like the high frequencies fall of a cliff around 10 KHz). Those measurements also seem to have impulse responses with extra-large wiggles before the main spike. In addition, every once in awhile (but much less often), the system just seems to receive no signal even though I can hear the speaker receiving the stimulus.

I'm a new user so I apologize if I'm just repeating something that's been discussed before. I didn't find anything with my search.

Thanks,
Few
 

·
Registered
Joined
·
14 Posts
Thanks for the prompt response. If memory serves, I was having trouble when using 5.17. I'll freshen things this evening and try again.

Few
 

·
Registered
Joined
·
9 Posts
Discussion Starter #14
I've been on 5.16 since I started this thread.

Will update to 5.18, rejig (got new parts but still waiting on TDA amp) and retest.
 

·
Registered
Joined
·
14 Posts
I wanted to report back after updating to REW 5.18 and gaining some experience with it. I run into fewer problematic scans than I did with the earlier version, but still encounter them intermittently. Are there particular settings I should use to minimize the likelihood of a faulty frequency scan?

Thanks very much.
Fwe
 

·
Premium Member
Joined
·
1,400 Posts
I wanted to report back after updating to REW 5.18 and gaining some experience with it. I run into fewer problematic scans than I did with the earlier version, but still encounter them intermittently. Are there particular settings I should use to minimize the likelihood of a faulty frequency scan?

Thanks very much.
Fwe
Some Tips:

(A) If you're currently doing multiple sweeps for each data capture, don't.
- It's a known issue that multiple>successive sweeps can sometimes mess up the final result.

(B) Make sure all your Sampling Rates agree with each other ( in your Mac's control panel, within REW and any choices that are within dedicated soundcard driver software ).

:)
 

·
Registered
Joined
·
14 Posts
I'm doing single sweeps but thanks for the advice. I'll double-check on the sampling rates. They may not match up.

Thanks again.
Few
 
1 - 17 of 17 Posts
Top