Anyone know how to perform distortion measurements w/ SoundEasy?

[bmaupin]

If you know how, please post the steps necessary to perform a Zaph-like distortion measurement. I cannot believe I cannot figure this out by clicking on every menu/option.

[bmaupin]

bump

[lhwidget]

With a driver loaded, connected, and ready to test, go to EasyLab-> Non-linear Parameters I.

That one produces the graphs Zaph publishes.

The Analog THD-IMD selection produces F2 - F9 graphs.

Don't forget ear plugs, it gets nasty loud through the midrange and seems to take forever

[r-carpenter]

woofer in free air or your loudspeaker. RCA to probes disconnected! Voltage to terminals 2.83 if you want to see standard distortions but you can also take sweeps at different voltage levels and see.

[bmaupin]

woofer in free air or your loudspeaker. RCA to probes disconnected! Voltage to terminals 2.83 if you want to see standard distortions but you can also take sweeps at different voltage levels and see.

Do you mean "disconnect the reference probe"?

[bmaupin]

Do I just click the "Sweep" button, or what series of buttons?

I put my setup away, but will try after work.

[augerpro]

Main thing is to make sure to use a Y splitter so the mic signal is sent to both the L&R inputs on the soundcard.

Set sampling at whatever your card is capable of running. Enter the frequency range (From & To) and click sweep.

[r-carpenter]

Do you mean "disconnect the reference probe"?

Yes, you only need one channel to measure distortions. If the left is connected to the reference probe, you'll get gibberish.
And yes, set up the range you want to sweep, 1000-20000 or 20-4000 for the woofer and "sweep"
For the woofer you may want to input motor parameters.

[augerpro]

BOTH input channels on the soundcard must be Y'ed together to the mic output. You don't use the Ref probe at all, but you can't just use one channel either, the plots are screwy and F1 will not be correct.

[ErinH]

Bumping this thread to seek help myself.

My setup is a XLR dual pre soundcard/preamp. For distortion measurements I have the output going to the amp, and the mic going in to the right input. Those are the only connections. Are you saying, above, that I would need to purchase an XLR splitter?

Additionally, with the settings shown below, I'm only able to measure up to 2.5khz and the sweep just stops. For no reason. Every time. Like clockwork. I've checked my preferences and nothing is jumping out at me. The distortion measurement tab seems like it's simple: set up the sweep range, push sweep. But, apparently I'm missing something
Note: Sampling rate is set to 48khz.

Here's a screenshot of my settings. Obviously I'm screwing up somewhere, but not sure where. Any help would be appreciated.

[benchtester]

I am not an expert and I look forward to further explanations.

But you appear to be in the "Non-linear Parameters Extraction"

At the bottom of the EasyLab pull-down is "Analog- THD, IMD" selection. I once got something similar to Zaph's graph here. I always get 9 harmonics, and I don't know how to reduce it to 5 (for clarity).

That's all I got ...


Edit: reading this thread:
http://techtalk.parts-express.com/sh...63#post1726363
I see that statements that Zaph is using the "Non-linear Parameters Extraction" screen (which may explain my harmonics issue). I guess I was wrong and eagerly await explanations.

[lhwidget]

Erin,
Did you see augerpro's post above yours?

[ErinH]

Erin,
Did you see augerpro's post above yours?

Yea. I was directing the XLR-splitter cable question to him, actually. If that will work for me, then I'll stop by RadioShack later to see if they sell a splitter.

[ErinH]

Just wanted to bump this one more time before I order the parts necessary to split an XLR cable.

I asked this question on SE and someone replied that a splitter is not necessary, and I should be using the "analog thd" tab (last one on the easylab list). But, that isn't what zaph uses. He also suggested the reason I'm not seeing response all the way out is because the driver is linear so I'm going to crank up the output and get the driver near xmax (manual states "high excursion"). Wanted to bump this thread in the meantime.

[bmaupin]

The directions given here worked for me - output from mic pre amp into both L & R soundcard inputs.

[ErinH]

Well, I'll give it a shot then.

My setup is a bit different than most in that my USB soundcard is both the soundcard and the preamp. There's no way for me to y the mic signal out because the Dual XLR only has one set of inputs; left and right and it's connected via USB to the PC. So, I'm just looking for clarity here that I can split the phantom powered mic into the same inputs that provide the phantom power to it. Make sense?


Starting to wonder if I need to purchase a soundcard like the m-audio transit and use the xlr dual pre only for phantom power, routing the outputs in to the m-audio transit. This crap is confusing.

[ErinH]

I futzed around with things last night and somewhat figured it out. I wound up having to use both my Dual XLR soundcard/preamps, though. I used the mobile pre to power the mic and ran the signal out via a splitter to the inputs of the ART dual pre piece. I got meaningful results but still had the distortion stop at about 2.5khz.

Additionally, when I tried to use this same setup for measuring FR, I couldn't get results because there was no input recorded (as evidenced by the no impulse response). I had to plug the mic directly (as before) into the ART dual pre and eliminate the mobile pre.

I'm thinking I'm going to have to buy a legitimate soundcard (instead of using the dual pre units) and use only ONE of the dual pre units for phantom power only and route it's signal in to the soundcard. I'm going to pick up a new soundcard locally and see what kind of results I get. If it doesn't work I'll take it back. Wish me luck, guys.

[bmaupin]

I had a MobilePRE and found it to be a poor soundcard for measurements - the levels changed for every measurement - no consistency.

I have a 96kHz sampling rate soundcard, set SE system freq range to 10Hz to 50kHz, show F4 and F5 plots, and the graph stops at 9k.

I highly recommend getting a 96k card.

[ErinH]

I actually just bought this to try:
http://www.bestbuy.com/site/Rocketfi...ci_sku=9180414

Not the greatest reviews, but looks like it might work for what I need it for (ie: I don't need fancy options). It does 96khz, so that's a plus. If I don't like it, back it goes.


I'm hoping this will work for the input/output and let the ART dual pre work for phantom power and use it's outputs to the soundcard's inputs.

[ErinH]

^ what are you using to power the mic and route the signal to your card's input?
Also, I know you're using a y-splitter out of your mic preamp and in to your soundcard L/R channels for distortion measurements, but what about SPL? Same thing?... just grab the pre-amp right signal, run it in to your sound card's right signal and use the sound card's left signal for the probe?

I'm now having a problem getting my dual pre unit(s) to output to the soundcard's inputs. Loopback test is fine, but when I tried to record with the mic I get the same results as I did with loopback... IOW, it looks like the mic isn't being powered and/or the signal isn't being routed from the dual pre unit mic input to the output. Maybe these units don't allow for this? Who knows... I'm stumped. Phantom power is enabled. Hopefully it's something in the settings but at this point I'm about ready to buy the behringer 802 preamp since it has RCA outputs and a lot of others use it with no issues. I can see if that's where the problem is.

If I know what you guys are using, maybe I can get an idea of my issue.


Edit: I think I just realized my problem...
my soundcard has stereo input, but it's only via a single 3.5mm connector. There's no way for me to route separate inputs for the probe and mic measurement in to it. I think I shot myself in the foot with this soundcard.
There is an aux input, too, but I'm not quite sure how to get to that pin since it's on the card itself.
Man, this stuff shouldn't be this damn hard. I'm about to give up.