Location: Dagenham Essex
Posts: 11,215
I'm Allen.
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Location: South downs
Posts: 3,477
I'm James.
How goes it ? I noticed another pair of 401's on eBay which could be handy for spares should you need any.
I now have the re-foam kits and am waiting for a day off to get to work on them. I'm too tired in the evenings! Will likely start tomorrow as I'm at home waiting for BT Infinity to be installed.
Great find Martin (just noticed this thread!). My only observation with the crossovers is that the two air-cored inductors on the RHS are a little close for being on the same axis (the influence from air cored inductors with the sort of current you'll get through them could be 150 to 200mm) so I'd be tempted to turn the axis of the top RHS (smaller) one over by 90 degrees and cable tie/glue in place.
Get rid of those caps (is that electrolytics they used for crossovers?) and replace with something like the Claritycap MRs or ESA polyprops instead. Resistors I'd test and if in tolerance leave well alone. L pads can also be tested but if replacing with an alternative fixed value solution, ensure that you understand any impedance ratio's for the "flat" setting as you may end up having to tweak a resistor value or two (don't know as I haven't looked closely at the circuit diagram but worth consideration?).
Thanks, Paul. Good advice about the inductors, I'll check. Being the US built ones, I'm hoping the point-to-point crossover board comes out easily. I will definitely be replacing the caps and I like ClarityCaps a lot. However, the 80uF and 66uF(?) will have to be replaced with good modern bipolar electrolytics.
I was going to measure the resistances of the pots in their factory set 'centre' positions and substitute with fixed resistors. Much to do!
Location: Yorks
Posts: 16,643
I'm Nobody.
I've just seen that the two big caps (60uF and 80uF) are simply in series, so I can replace them with a single 34uF cap. I could therefore use a Supersound 30uF in parallel with a 4uF. Better not to have the signal going through two caps in series.
Andre: yes, Ansar are really nice caps, too. Choices, choices...
The Centre position on the UK made 401 and 402's wasn't the "flat" setting. I'm sure I remember there being "calibration" positions marked on the backplate where the knobs were aligned to, the mid almost fully up I think from long-ago memory. Since the bass is so dry on these, I think I used to back the mid off a bit from the "calibration" setting, but since the updates to the crossover you're making may well alter this original setting, it'll have to be done by ear if you don't have means od measuring what they're doing.
Hint - if you like to rebuild classic speakers and bearing in mind your obvious reasonable disposable income, why not consider a dedicated software for measuring and a properly calibrated mic. I know it'll be probably expensive and I'm way out of date, but MLSA? used to work brilliantly in free space, the mic carefully set in distance from the speaker.....
Tear down these walls; Cut the ties that held me
Crying out at the top of my voice; Tell me now if you can hear me
Location: Yorks
Posts: 16,643
I'm Nobody.