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In Reply to: RE: A warning from Magnepan posted by josh358 on April 15, 2017 at 14:02:12
It is funny that of all things it was the finish on the grills that went first on speakers nearing 20 years of service. I really don't understand how this pair survived looking so youthful. Maybe someone lacquered them early on?
Follow Ups:
Or found a way to polish them?
This is the external crossover. Low pass, 18dB/octave at about 250 Hz. High pass, 12dB/octave at about 400 Hz. I prefer to use an active crossover, at least for the low pass section.
Edits: 04/16/17 04/16/17
I just bought a pair of IV's and I have found also an original Magnepan XO -1 crossover, BUT on the little black box is written: crossover freq. 210 pfd, speaker model T-1D amp. imput impedence 470K. So it seems this one is not good for biamping my IV. Please help, thanks.
The XO-1 is not a true crossover, it is just a volume control for the bass. The bass driver need to keep its coil. The tweeter section can have its capacitor at line level right at the input of its power amplifier.
The XO-1 is intended for passive biamping. Some have installed inside a high pass capacitor matched to the input impedance of the amp driving the mid/tweeter section. The markings on the one you have are indicating that it is intended for an ARC tube amp to drive the tweeter of the T 1D. That means the box was likely back from the day when ARC did the marketing for Magnepan.
Calculating from the values, The crossover was a 500hz so is a fit for the T IV rather than the T-1D If you have a tube amp to power the top end it might match the input impedance if it is around 500K. SS amps are rarely that high and most commonly at 10-50k.
You can modify this XO-1 to either allow passive biamping by shorting out the capacitor inside with a wire, or switching it with a value that matches your power amp for the top drivers. e.g. 6nF or 0.006uF for a 50K input impedance or 30nF or 0.03uF for a 10K input impedance.
When bypassing the internal XO-1 cap you use the separate biamp markings on the passive speaker level box via the diagram on the crossover box if you have the one with two sets of input connections like the MG3.x box. If you have the box with a single set of connectors then you should use the internal capacitor option. .
When using the capacitor (the one appropriate to your amp) you do not connect the top amp via the speaker's crossover box, just the bass amp will go through it.
Many Thanks Satie, I would like to use my IV-A with 2 ADCOM GFA 555.Do you have the manual of the XO-1? It seems impossibile to find. Thanks again.
The 555's 22k ohms input impedance requires 0.0144uF so either a 0.014 or 0.015 uF will do.
Does anyone have a copy of the schematic for the external box?
I have reached out to Magnepan for the schematic and they have been very kind supplying documents. Unfortunately they keep sending everything except the Tympani IVA schematic!
You can find it here, http://www.integracoustics.com/MUG/MUG/tweaks/mikebarney/Tympani-4a_xo.gif
I placed a link to a picture one of my own crossoverboxes in the other thread. Any more information you need? I have a pair of T-IVa that is the procees of modifying.
Email me, I'll send it on.
Thanks for the offer. I see you don't accept email from the Asylum.
OK, should be fixed.
Really? Sorry about that, that was supposed to be turned on. I'll go change it. (Not sure if it's intentional but your profile said doesn't accept mail too, which is why I didn't just send it to you.)
Weird. I thought mine was set to on.
Looks like we're both in the same boat -- a glitch in the Asylum software? Because people have never had trouble emailing me in the past and I know I didn't turn it off.
Yes must be some sort of glitch. Just changed mine.
I usually get quite a bit of email from the Asylum. Had not seen any lately now I know why!
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