Tang Band W4-1658SB distortion measurements

[fjhuerta]

I wonder - did I do them right?

I measured them in-baffle. The measurements are for two woofers in series, at 50 cms away, and SPLs of around 97 dBs.

The woofers are in-cabinet.

I don't know why the sweep stopped there. Supposedly, I configured it from 200~20 KHz.

Still, I assume I could use this woofer very high up, if I'm reading the graph correctly.

[fjhuerta]

I took two more today, to see if I could increase the measurement range. I also took them on woofer axis, instead of on the design axis (the tweeter).





I see some definite trends, although my noise floor isn't as low as I'd like it to be (you can see I took these measurements in the morning, with more ambient noise everywhere). Still - can I conclude the woofers are extremely clean up, and so, I can use them as high as I want to? Or, am I missing something?

[pedroskova]

I've never used Soundeasy, but it would appear that the program only "believes" that it can record up to ~10k - 12k, depending which graph you're talking about. Maybe you could check the sound card setup? It looks like a 22k - 25kHz sampling rate. With a 44kHz sampling rate, the second harmonic would reach 10kHz.

[fjhuerta]

I don't know why, but it all looks too clean to me to be true...

[Jed]

Something looks off with the fundamental SPL. However, maybe others that use Soundeasy could chime in. I don't use that software, personally.

[jkrutke]

I have to agree, something looks wrong with your fundamental, and the harmonics floor is abnormally high. It almost looks like there's a massive 15-20 dB droop in the top end. Can you post a response curve?

You might be clipping a preamp either in your sound card or mic pre, it might pay to mess with the levels a bit. Try a lower level semi-near field (10 cm) of an unfiltered known driver to see what you get.

[fjhuerta]

Here it is. 10 milliseconds, speaker lifted around 1.7 meters off the ground, taken at 1 meter, unsmoothed and unfiltered. No floor or wall bounce (am I right in assuming the graph is correct right to 100 Hz)?

There is a drop of around 10 dB, indeed on the top end. That's the natural FR of the driver.

When I looked (closely) at T-B's published specs, the drop is there, too. It's just not noticeable because of the scale they chose.

I know the measurements can't be right. I'll try to take some more tonight... thanks for your help!

[fjhuerta]

I assume something is wrong with my measurement setup. This is the best I can get, and measurements won't go any higher.

[Notorious_AK]

I get similar results as first three graphs when I forget to turn mic preamp on. there may be a problem with your preamp. is phantom power on?

[fjhuerta]

Yeah, if phantom power was off, I wouldn't be able to get a reading...

I think I'll try ARTA