Has anyone here measured a TD15M? (I have them)

[dumptruck]

(edit: I should have said "I am trying to measure them" in the title, because that's what I meant. There are now measurements posted later on in this thread, and there will be more.)

Much discussed, rarely measured. I've totally stumped myself measuring these, as I'm getting a mystery reflection 2.45ms out in the impulse, exactly the same every time, seemingly regardless of whether the woofer is on a baffle, in a box, in free air, near a boundary, or whatever you like. I am a total beginner at driver measurement, but it's only these woofers giving me this weirdness - not other drivers. If there's anyone out there that wants to compare some graphs here, please speak up! Thanks.

[1audiohack]

Originally Posted by dumptruck

Much discussed, rarely measured.

Too funny as I have often thought the same thing.
I have a pair coming but can't help you yet.
So, if you sweep the TD and then change nothing else but the driver the mystery blips gone?

[dumptruck]

Yes, it's just this driver (both of them - I have a pair). I have posted the details elsewhere, and I will copy them over here when I'm feeling less lazy (so, tomorrow).

[twest820]

I recall there being an issue with the cone on the 15M ringing that would show up that way---you should be able to dig it up the relevant DIYA thread with some searching. Is this MLS or swept sine/chirp measurement?

[DeonC]

Hi there

Have a look at the thread 'Is the AE TD15M the ultimate mid driver?'. There are several measurement graphs posted there.

Enjoy,
Deon

[dumptruck]

Originally Posted by twest820

I recall there being an issue with the cone on the 15M ringing that would show up that way---you should be able to dig it up the relevant DIYA thread with some searching. Is this MLS or swept sine/chirp measurement?

It shows up in either type, or at least I'm 99% sure it does. I will see if I can find that thread.

Originally Posted by DeonC

Have a look at the thread 'Is the AE TD15M the ultimate mid driver?'. There are several measurement graphs posted there.

Those are mine.

[dumptruck]

Originally Posted by dumptruck

It shows up in either type, or at least I'm 99% sure it does. I will see if I can find that thread.

Well, I couldn't find the thread you are talking about. To clarify about MLS vs log sweep, I saw the issue in a long log sweep measurement, and then switched to MLS for a bunch of fast measurements trying (and failing) to eliminate the issue. Unless there was some massive coincidence where the log sweep had a normal reflection in the same spot, it is the same for both types of measurement.

[Flaesh]

Is the AE TD15M the ultimate mid driver?

[dumptruck]

If you are showing me that thread because there is something in it about this, you'll have to be more specific because I didn't see it. I have several posts in that thread, and I am the only one that posted measurements in that thread (I think).

[bwaslo]

Dumptruck,
MLS and sweptsine (or chirp) should show the same as far as real reflections go. But MLS can sometimes show phantom impulses from nonlinear distortions, while log swept sine is immune to that kind of phenomenon (with log swept sine, phantom impulse occur before the real impulse, so they don't get into the result). So if the second impulse shows with swept sine, it is probably real.

It isn't a reflection off your mic stand, is it? The TD15M has a lot of HF output, so it will show impulse peaks more sharply than other big drivers, and its size gives it lots of opportunity to excite nearby objects or surfaces. Look for things that are 14 to 24 inches from your mic or the woofer.