Celestion ditton 44 crossover repair help needed please .

Hi Guys & girls ,
Well I went and purchased a pair of ditton 44's in very good cosmetic condition, stupidly I didn't ( couldn't ) test them at the point of sale but I was assured they were fine .
Alas when I plugged them in I immediately knew that the muddy sound couldn't be right .... TWEETERS !!! ... Oh no more expense !!!
But fortunately ( I think ) the actual tweeters are working fine but it's something on the crossover, imo some capacitors, but I'm not sure which ones feed the tweeter(s) ( it's both speakers) I do have photos of the crossovers on this phone but I've no idea how I upload them . Btw they are mark 1 44's ( I'm told )I know nothing about electronics but I'm determined to get these up and running by myself and of course with the expert advice I'm hoping I'll get from you guys .




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I'd test the tweeters before doing anything further. Fortunately as the wire terminals are on the front, you can do this without removing them. just use a cheap multimeter (about a fiver from Maplins etc.). They should measure around 4 ohms.

Hi Walpurgis ,I have basically wired an amp only very low volume directly to the tweeter and to my ears they are fine . Do I replace the black things on the crossover ? ( caps )

Hiya,

Have a look at this thread should get you up to speed on changing caps :-
http://theartofsound.net/forum/showt...ng-ditton-44-s
Cheers :)

Quote:

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Originally Posted by andyrlb

Hi Walpurgis ,I have basically wired an amp only very low volume directly to the tweeter and to my ears they are fine . Do I replace the black things on the crossover ? ( caps )

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Hi Andy,
I've taken your various posts from other threads and collated them here to simplify things.

Quote:

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Originally Posted by andyrlb

Hi Madders,
Hope you don't mind me asking how you got on doing the refurbishment on your 44's ? I am in need of little advice about mine , basically I have no feed to the tweeters .
Regards
Andy

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As Geoff (Walpugis) has said the first place to start is to check your tweeters for continuity with a multimetre, like so: http://theartofsound.net/forum/showt...796#post745796. If your tweeters check out, test your inductors and wires, although these are highly unlikely to be the fault it only takes a couple of minutes to test.

I've put some arrows on your photo's to identify the tweeter caps and inductor:

http://i1324.photobucket.com/albums/...psoic4f0n2.jpg

If you do have any problems here I have spare inductors and some Jantzen CrossCaps and Alcap LL (I'm no longer using them as their not the best choice) you can have for the price of postage.

Quote:

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Originally Posted by andyrlb

Hi Jamie , I am about to replace the tweeter caps on my 44's but I'm not sure what to go for , any advice please

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I'd be as bold to say Ken's (Qwin) approach is the AoS recommendation: http://www.jkwynn.co.uk//Project_Images/66/66_XOver.pdf (don't worry that this is for Ditton 66's the crossovers are very similar and identical in the HF), that is 1 x 4uF Ansar PP and 1 x 4.7uF & 1 x 1.5uF Ansar PP, they are available from here: http://www.wilmslow-audio.co.uk/supe...itors-68-c.asp

For further reading Ken has fully documented his work on the 66's http://www.jkwynn.co.uk//66_HTML/66_Thumbs.html / http://theartofsound.net/forum/showt...ghlight=ditton

Hi Darren, thank you so much for your help , I suspected it was the black things that you've pointed out , at last !!!
I would be over the moon to use your bits and pay postage and more if need be . Top man .I had best go and buy a soldering iron now .
Pls let me know how you'd like to be paid etc .
Thanks

If tinkering with speakers is likely to be regular, invest in an LCR multimeter. I've been using one for years. An absolute must if you're serious.

Well I do appear to have "a thing " about speakers so I will follow your advice Mr Tact , thank you.

Quote:

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Originally Posted by andyrlb

Well I do appear to have "a thing " about speakers so I will follow your advice Mr Tact , thank you.

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This is the sort of thing: http://www.ebay.co.uk/itm/LCR-INDUCT...sAAOSw3mpXIV~W

You can the test inductors, capacitors, resistance and continuity.

By the way. Did you know that the DC resistance of moving coil drive units will measure less than the impedance rating (usually)? An 8 ohm speaker unit will typically read at 5 to 6 ohms.

Quote:

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Originally Posted by andyrlb

Hi Darren, thank you so much for your help , I suspected it was the black things that you've pointed out , at last !!!
I would be over the moon to use your bits and pay postage and more if need be . Top man .I had best go and buy a soldering iron now .
Pls let me know how you'd like to be paid etc .
Thanks

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Yes, the black things! I'll dig out the caps and get them packaged up over the weekend and drop you a PM. I have Jantzen CrossCaps for the tweeters and Alcap LL for the mids, you may as well replace the mid caps whilst your in there but if your keeping the speakers I'd highly recommend swapping them for Mundorfs and Ansars in the future.

Good spot on the LCR Geoff, that's quite a bargain!

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.

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.

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 :D

andyrlb - how have you got on?

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 :eyebrows:
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.

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Originally Posted by 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 :D

andyrlb - how have you got on?

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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.

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.

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.