baffled_loudspeaker

Thanks for all the input! I don't like the sound of messing with toluene (yikes!) so I've sent it to Larry / Vintage AR. I appreciate the help though! I'd have to buy a replacement surround from him regardless.

The seller used M-3035 adhesive. Do you know what could dilute it? Also, you're sure there's a masonite ring under the outer edge of the surround on the 12" AR-9 woofer? It's not just bonded to the metal basket? Thanks again.

That's a great idea. I'll ask. Thank you for the tips on the solvents too. Thank you for the offer! I'm in Austin, TX now but I did used to live in Boston, dang.

I purchased a pair of AR-9s a few months ago and they're absolutely amazing. Unfortunately, the person who re-surrounded the woofers did not spend the time to align the coil in the gap, and there's a rub. I can "push" the cone radially outward and it'll stop rubbing for a short time, but it returns in a few minutes. I think this will eventually short the coil I've tried rubbing a little bit of acetone on the replacement glue and I was unable to remove any of it. Does anyone have any suggestions? Would someone be willing to repair this for me? Or sell me an original woofer? Thank you!

Are you referring to @AR surround's loudness problem? Or something regarding the crossover schematics? You are making me look closer at the -9 schematic, and that redrawn -9 schematic has the tweeter, UMR, and LMR transducers wired in opposite phase from the AR-90 schematic (below). @fedeleluigi, can you comment on the accuracy of your AR-9 schematic and the wiring colors and polarities?

For the record, this is my SPICE analysis of the voltage transfer function of the AR-90 crossover. This does not include the impedance of the transducers, only a resistor equal to the DCR. This is also not the acoustic output of the speaker, which is a whole nother can of worms. I intend to complete both of these in the future, time permitting. My true goal here is to replace this crossover with bi-amping or tri-amping (quad-amping?) and an active crossover.

To summarize the thread, we've figured out that the -9 and -90 have the same UMR crossover. The popular -9 crossover schematic floating around the internet was incorrect in two ways. Luigi Fedele's updated AR-9 crossover schematic (attached) is supposedly accurate and shows that the it is the same as the -90. I say supposedly because I haven't verified it myself, but I have no reason to doubt the other contributors in this thread. We have an AR engineering drawing of the -90 schematic. As to why you're experiencing greater output from tweeter and UMR of your setup, I would first suggest that this is due to acoustics. I say that because both transducers are too loud - they're separate drivers and separate sections of the crossover. The thing they have (nearly) in common is the acoustic path, particularly the distance from the speaker to the listener and angle / directivity. I'd experiment with these variables before modifying your speakers! A good thing to keep in mind is the Rayleigh distance, which is an approximation of where the nearfield of a baffled piston ends and the farfield begins. The farfield is where the pressure radiated from a transducer begins to decline at 1/R. The Rayleigh distance is R_0 = [surface area of the piston] / [wavelength of interest].

Haha well that explains it! Thank you Luigi! This should be updated in the Library section.

Yes! But why?!

Ah, thank you for the correction, Stimpy. I was working from that incorrect schematic! I've updated my SPICE simulation, see attached. The 8uF cap reduces the discrepancy between the 9 and the 90, but the the inductor on the 90 still gives it an additional ~+0.8 dB of output to the UMR. Why should these two crossovers be any different?

Looking at the AR-9 and AR-90 crossover schematics, there's a difference in the upper-midrange schematic. There's no 1.37 mH in parallel on the -9 and the 6uF parallel cap in the -9 is 8uF on the -90. It amounts to a +1.5dB difference in the passband for the -90. Anyone know why the -90 UMR is different, despite both models having the same LMR, UMR, and tweeter? The -90 has more components despite it being the lower-priced speaker, and it's not a demonstrably worse crossover, it's just louder. The rest of the two crossovers are identical. I've attached a SPICE analysis of the two crossovers. The UMR driver is represented by a 4 ohm resistor. There's a second plot with the -91 just for comparison. (The AR-91 also has a different UMR crossover, but it's obviously cost-reduced)

Hi folks, I'm looking at the AR-90 crossover and modeling the transducers. I would love to have the Thiele-Small parameters of the transducer, a thread from 2007 already gives some of the parameters for the mid and woofer. Has anyone measured the other transducers? Thanks!

Two stories I can relate about a similar occurance at another New England speaker company I used to work for. One tower speaker of a pair was designed with a power supply and amp in the base, the other was fully passive, and a proprietary connector connected them. However, this made the two speakers weigh very differently. One felt unnaturally light thus cheap. To fix that, the passive speaker was designed with a brick in the base. An engineering-spec brick. Revision notices had to be issued whenever the brick manufacturer changed formulations or went out of business, and the new one had to be re-weighed. This company also had a longstanding rule of no food at your desk or workstation. The aboveboard story is that this was a carryover from when people did manual drafting, and it's expensive to redraft or copy an E-size plot due to food stains. The belowboard story is that, back in the day, someone had bought the very recognizable flagship product and a few weeks later it started to smell. They called customer service, complained, and CS thought they were confused, suggested it was their pet or likely something else in the house, and they hang up. The customer called back repeatedly over time. Finally, CS sends out a technician, this being the days of technician house visits. They open up the cabinet and find a rotting half-eaten sandwich.

Thank you Roy! I appreciate the detail. Wouldn't have figured that the SS model, with the same PN, is not what I have. Upon further investigation, I think every transducer in my AR-90 have been replaced. The most recent owner recently had them reconed because the surrounds were disintegrating, but that suggests that they were first replaced a long time ago and might be AB Tech-era replacements, similar to the tweeter. No idea if I should spend $200 and recap them myself or find a better pair.

I have a pair of AR-90 that have the Simply Speakers 1200084 replacement tweeter. It's very old and has crumbling foam on the surface. Can anyone speak to a difference between this one and the Midwest Audio replacement?