IB15 questions

[augerpro]

Hi everyone. I was wondering how the AE IB15 REALLY performed for say open baffle bass? I did a search and all the threads were pretty old. Any new info?

[chrismercurio]

You can use the Xbaffle software to predict.... but I don't have a pair or measurements.

[mpotoka]

What specifically are you looking for as far as information? I installed 4 of them in my theater about five months ago.

[augerpro]

I guess I'm wondering if there is any 3rd party measurements, are the TS parameters consistent, how high can they be run, distortion, impedance & inductance, etc. Just general performance questions. Obviously with 14mm xmax and Qts of .707 they model well for OB, but how do they REALLY perform?

[mpotoka]

Well I wasn't into the speaker designing thing yet when I put them in, so I didn't do any testing with them before installing. I am going to be selling my house in a few months, so I was planning on taking them out and finding other uses for them. I could take some tests then. Right now I don't have any way for measuing distortion, but I hope to have soundeasy by then.

I could go put my impedance jig on them, but how they are installed would probably make them all measure a little different. I could do some nearfield measurements if you were interested in that.

[ThomasW]

These are JohnJ's published specs for the newest version of the driver.

Fs: 16Hz
Qms: 6.8
Vas: 439L
Cms: .45mm/N
Mms: 220g
Rms: 3.239
Xmax: 18.5mm
Xmech: 25mm
Sd: 830sqcm
Vd: 3.07L (p-p)
Qes: .78
Re: 5.5ohm
Le: .33mH
Bl:12.49
Pe: 500W
Qts: .7
1WSPL: 86dB
2.83V: 87.3dB

There are several dozen of the new version in use. So far everyone is quite pleased with how they preform. But no one using them has a testing rig.

[mpotoka]

What would I need to properly test these? I figure its the least I can do compared to all the information I've gotten from here. I a picking up my M-Audio Firewire Solo later this week (bought on craigslist). I have an ECM8000 Mic, and have Speaker Workshop setup right now (although will have to re-do things once I get the firewire card)

[augerpro]

Thanks Thomas for info. mpotoka could you run an impedance and also do this: push the cone in to about xmax and run an impedance and then push it out to about xmax adn run an impedance. If it looks even somewhat decent I may just buy to test out.

[mpotoka]

I can do that once I have pick up my firewire card--I was using a laptop for measurements before, but my screen went caput about two weeks ago, so now it isn't portable anymore

[Dennis H]

For an OB, the biggie that T/S can't tell you is noise/chuffing from the backside of the driver. It can come from the pole vent and other places depending on the mechanical construction of the driver. You need to just set one naked on the bench, drive it to near Xmax at 20 Hz and listen for any noise.

[augerpro]

What the heck, I bought one. I'd like to compare it to the B&C 15NW76 for bass duties in open baffle, so I may still pick one of those up. The idea was to make an all pro audio speaker to see for myself if there was anything to the hype. But low Fs, long xmax, and a Qts of .7 is just to perfect not to check out.

[mpotoka]

Well I'm not sure I did this right, or what it is going to tell you. Black is the driver just sitting on the ground. Blue is with my hand pusing it out, Red is with my hand pushing the driver in. Should I have done this differently? I didn't include the phase data for the push in/out because it was a big mess.

[augerpro]

Thanks. As long as you push in/out to about xmax the info is as good as you can get with out a Klippel. Looks pretty good as a woofer-motor stays pretty linear up to 1k Hz- which should allow a high cross point with a passive crossover. Inductance is low for a 15" subwoofer. We'll see what the frequency response is and hopefully it can run up to 250Hz or so. I'm surprised there isn't a break up visible in the impedance.

[---k---]

Brandon,
I've never heard of this method of testing. Can you explain a bit more the principals of how it works, and how you are interpreting the graphs.

thanks,

[mpotoka]

Well I've got the woofer out, and I could get out a microphone and see what I get for a measurement. I suppose you really need it mounted in a baffle, and not laying on the ground?

[augerpro]

Zaph had posted it once in his blog, it's referred to as Le(x). It's just an informal way to see changes in inductance (and hence how linear the motor is) as the excursion increases for those of us who don't have a Klippel. It's just a rough estimate. Ideally the impedance at rest and at xmax both in and out would be identical. If this were a mid obviously it would be a pretty poor cross to a typical tweeter since the variation in impedance would drastically affect the response of a passive crossover. Here is more info: https://web.archive.org/web/20081212233459/http://www.klippel.de/pubs/Klippel%20papers/Loudspeaker%20Nonlinearities%E2%80%93Causes,Parame ters,Symptoms_06.pdf

[augerpro]

Well I've got the woofer out, and I could get out a microphone and see what I get for a measurement. I suppose you really need it mounted in a baffle, and not laying on the ground?

You don't have to bother, I have one coming. With an impedance of 28ohm @ 20k Hz obviously John is paying attention to the motor. And it's pretty linear in it's normal passband so I figure it's a safe buy to investigate further.