CLIO Clinic

[JuniorJBL]

Hey Zilch!

How goes the CLIO setup? Have you done any measurements yet?

[Zilch]

Hey Zilch!

How goes the CLIO setup? Have you done any measurements yet?

Heh. JuniorJBL sent me a computer for the "Lab," which is now up and running, folks.

Mr. Widget's gonna help and shorten the learning curve here....

[Keep them JBL Monitor Blue grille cloth orders comin', now.... ]

[Zilch]

Heh:

[Robh3606]

Hello Zilch

You can change the scale to SPL so you not reading in volts. Just set-up with your test signal to get an SPL reading. Set up the Mutimeter to read Preasure. That will give you a base SPL with you test signal. Be careful with the signal levels. Start way down and come up.

Rob

[Zilch]

Thanks, Rob. I switched to pressure, now.

I KNOW I'm supposed to be movin' on beyond RTA, but it's a lovely full-screen one with multi-color plots and lotsa parameters to tweak.

[Also, gotta re-read the FFT chapter in D'Appolito.... ]

[Robh3606]

I KNOW I'm supposed to be movin' on beyond RTA, but it's a lovely full-screen one with multi-color plots and lotsa parameters to tweak.

Hello Zilch

Lot's to tweek your not kidding we have 3 ways to measure and then some. It will take us a couple of months to really learn the software. First thing I did was check out the RTA against the Behringer. This one is a bit better. The Sine and MLS blow the RTA away.

Rob

[silne3]

Greetings,

I have a Clio win 6.5 and I am trying to measure the T/S parameters of my 2225H.

Unfortunately the results that I get are far off from JBL. Anybody tried to measure T/S parameters of JBL drivers?

I also ran the speaker with 10W, 25Hz signal for 8 hours (burn in). The speaker was on a table, so the back of the magnet was covered. Do you think that the voice coil was damaged from the heat generated inside the driver?

[Zilch]

I haven't tried T/S with CLIO yet, but Mr. Widget earlier demonstrated that the conditions under which the impedance measurement is taken can vary the results considerably. Certainly, if you tested as you burnt in, i.e., with the port blocked, the values are dubious.

http://audioheritage.org/vbulletin/s...4&postcount=14

Suggestion: Get Woofer Tester 2, if you don't have it, and use that for comparative testing, parameter by parameter. It also outlines the methodology in more detail. With WT2, I get results generally in the range of JBL specs. With experience, I appreciate more that these are not "hard" numbers; they vary considerably with measurement technique. Contiguous runs under the same conditions get results that differ in detail, even. It's not an exact science, as I believe anyone who has attempted it can confirm.

Regarding your burn-in, I'd guess that if the driver is still working and sounding good, at 10W you did no serious damage. Do you recall how hot the magnet was when you turned it off?

[silne3]

The second time I measured the T/S I mounted the woofer 3 feet above the floor and the readings were still far off, I think that this is because of reflections from the walls and floor.

What is the recommended mounting of the loudspeaker for measuring T/S?

The unit is working fine; I just want to know if there is a chance for heat to build up in the unit, and if this heat can damage the voice coil?

[4313B]

Post the results you are getting.

[Zilch]

It's a better mic than the Behringer (rear); even RTA's are "cleaner."

DR Pro DR210 stand with extension boom was $49 at Guitar Center.

First runs MLS with a buncha waveguides.

[All kinda "peaky" at 18 kHz with 1200 Hz FFBREQ....]

And 5235 FFBREQ 800 Hz (red + orange) and 1200 Hz (blue + orchid) voltage drives.

[Zilch]

RTA (green), MLS (orange)

Sorry, I tried smaller, but the lines disappeared....

[silne3]

I placed the woofer on the table and raised it 1 feet.
The T/S are not the same as JBL but when I used them in WinISD the results where close to JBL.
Because their is close relation between the parameters they adjust each other.
Yellow line is Free air.
Red line is delta mass - 71 gram. The bump at 180Hz is from the mass.

I will use the 2225H as a subwoofer in a 8 cubic foot enclosure from the 1983 audio magazine.

[Zilch]

What is the recommended mounting of the loudspeaker for measuring T/S?

Mr. Widget suggests suspended, WTPro says on a rigid fixture, and another member says clamped to a bench. I test on the concrete floor sitting up on steel blocks.

I gave up on delta mass after several attempts and went to delta compliance in a known test box. I'm not about to mess with sticking mass to the cones with clay, nope. Your bump at 180 Hz suggests you may be having problems with delta mass, too.

As an aside, 2225 is the wrong driver for the '83 Kramer/Timbers subwoofer design. Consider reconing it to 2235H for that. Also, 8 cu.ft. was for the 18" 2245H driver, though the smaller B380 for 15" 2235H is also detailed near the end of the article:

http://www.lansingheritage.org/html/.../1983-subs.htm

[Zilch]

No calibrated turntable?

Not a problem -- move the mic instead:

1) Center pivot made from heavy old mic stand base with freewheeling pulley. Barbell weight plate would hold position securely, as well.

2) Device Under Test. Pivot is beneath the support dolly, directly below acoustic center, determined by aligning time to impulse identical from all angles. Dolly allows finding it within 0.1" easily. Upper pedestal is AR4x with insulated face.

3) Tape marks the calculated measurement angles in the requisite arc, these at 15°. I could confidently obtain 5° resolution at this distance, perhaps 2° or 1°, even.

4) Triangle of nylon cord keeps the distance and mic alignment exact. There's room for several inches of insulation under it here, but I've found that doesn't much matter, as I'm windowing at floor bounce. Getting the DUT up to 1/2 ceiling height helps considerably.

5) PT-F95 w/2426H, modified AM HP filter, in 15° increments.

Beamwidth waterfalls and classic polar plots next....