Celestion ditton 44 crossover repair help needed please .

[Reffc]

Funnily enough I have a pair of '44's in now for a rebuild.

What I would say to anyone looking for a cheap LCR meter is few of them are any cop when it comes to inductance measurements as they usually test at much higher frequencies than required. The industry standard test frequency for inductance measurement of crossover inductors is 1KHz. A lot of those cheap and cheerful meters measure at 10, 12, or 15 KHz, some higher than that. The inductance measurements wont be accurate so beware. At least find out if the inductance test frequency can be varied before you buy. If not, it'll be as much use as a chocolate tea pot.

Also, I think Geoff mentioned DC rating being less than Impedance (AC) rating. That's more to do with the rated impedance figure being a generalised ball park figure. Speakers are usually rated at 4, 6 or 8 Ohms these days (there are exceptions) but that doesn't mean that's what they measure. Most 8 Ohm speakers have a true nominal impedance of around 6 to 7 Ohms (bass frequencies) but are described as "nominal 8 Ohm) rated speakers. Usually DC resistance will be quite close to minimum AC impedance at low frequencies. As impedance rises with frequency, and most of the amplifier's juice is needed between bass tuning frequency and around 1 KHz, the averaged figure is taken as 8 Ohms even though the true maximum rating might be say 5.5 or 6 Ohms.

[danilo]

A while back I was Keen on an LCR meter.
This seemed as Good a 'cheap' one as could be had.
Lotsa info on this thing and it's inevitable army of Clones.
http://www.ebay.co.uk/itm/DER-EE-DE-...AAAOSw--1Wr7PY

Happily I had a Lucid Moment and realised that I wouldn't be Futzing around with inductors ever again :-) So I didn't buy the thing.

[Qwin]

danilo - If you were considering spending that amount, might have been worth looking at the DATS (Dayton Audio Test System) available from Parts Express.
Its a system for measuring T&S parameters from an actual driver and for plotting impedance curves of said driver etc, all useful stuff when building speakers. But it has an accurate resistance, capacitance(including ESR value) and inductance meter, you load the software on a laptop and plug the special test probes into a USB port. Yes I have it.
You never know when you might get the urge to "Futz" again

andyrlb - how have you got on?

[danilo]

Thank you for the advise.
Happily I suffered a Lucid Moment... rare indeed.
After 40 Years of 'Dicking with' ( No other term seems an honest/ adequate descriptor
with MY Tannoy Gold Crossovers and after having tried most Every touted permutation and some of my own devising.
I abandoned the quest.
Consequently I've no anticipated needs for such test gizmos.

[Reffc]

danilo - If you were considering spending that amount, might have been worth looking at the DATS (Dayton Audio Test System) available from Parts Express.
Its a system for measuring T&S parameters from an actual driver and for plotting impedance curves of said driver etc, all useful stuff when building speakers. But it has an accurate resistance, capacitance(including ESR value) and inductance meter, you load the software on a laptop and plug the special test probes into a USB port. Yes I have it.
You never know when you might get the urge to "Futz" again

andyrlb - how have you got on?

A slight qualification to that advice Ken would be that you still cannot select the test frequency for inductance which is done automatically in DATs, so (as I have found) it is not suitable for accurate measurement of all types of inductors. It seems to work well on air and ferrite cored instructors where it is broadly in line with a calibrated inductance meter, but show it a cored inductor using a laminated core, and it is a country mile out, as it measures way too high. It does allow for inductive equivalent measurements of voicecoils and that does have some calibration options in the menu, but not for general inductor measurement.

Other than that, DATs is a very valuable little tool.

[Canetoad]

I've decided to rebuild the crossovers in my Ditton 44s. I bought a spare set on ebay ages ago and removed all the capacitors from them this afternoon. Both boards have the same components except for the tweeter circuit. Ones has 4 mfd (1+1+2) and 6 mfd (2+2+2) and the other has 4.4 mdf (2.2+2.2) and 6.6 mfd (3.3+3.3).

Which should I use for the replacements? I plan to use supersounds, so 4.4 and 6.6 will probably be the easiest to sort.

I'll be using Alcaps for the 72 and 6 mfd caps and Mundorf Ecaps for the 30 mfd midrange.

[DarrenHW]

Original schematic: http://theartofsound.net/forum/attac...8&d=1412318861

I'd go 4.0mfd and 2 x 3.3mfd but others may be more particular. I'd also suggest an Ansar bypass with the Mundorfs for the mid.