2nd Posting - Someone Please Advise!

[hermanv]

I am now very confused! The 'what I thought I'd learned was a dustcap' is completely off of the other mid-range driver in the other speaker yet that speaker plays perfectly!

One of the functions of a dust cap is to keep grit out of the magnet/coil structure. Since a fair amount of dirt is magnetic it will fly in and wedge in the gap causing all kinds of difficulties. I think you need to fix this.

There is a fairly hardcore set of do it yourselfers at DIY audio, another forum that might turn up a spare driver.

http://www.diyaudio.com/

Also there is the "Loudspeaker Designers Selection Guide". A large, labor of love kind of site. Links to all kinds of driver manufacturers, design guides, driver data base, crossovers etc. This one is pretty awesome, anyone contemplating speaker projects or design should visit.


http://ldsg.snippets.org/index.php3

[royphil345]

I can't really tell by your pics if there's a opening in the middle of the dome where a dustcap might have been, or if you're saying the whole black dome part is off. I've never seen a dome speaker with a dustcap, doesn't mean there isn't one.

There may be an additional piece that keeps the voice coil centered with the dome glued on top of that? In any case, The mid drivers are going to need repair / replacement. Having someone test the impedance of the mid drivers with a multi-meter might be helpful if you have to find a new replacement. I'd test both. A driver with a shorted voice coil can give a lower reading. Test both and believe the higher number if the readings don't match. If you were lucky enough to find a replacement driver with very close magnet size and impedance measurement, the results would probably be quite good. Would still try have the originals repaired or find a used set in better shape first.

[sparki]

Can somebody tell a female who is only just about to attempt a speaker repair for the first time how to tell what is wrong with a mid-range driver in a 3-way speaker? What should I do to tell whether it's the actual speaker cone or the wiring or cross-over which is at fault please? I have looked all over the Internet for advice to no avail. Failing that can anyone recommend a beginner's easy to understand book which would take me through from the beginning. The fault by the way is a sort of fuzziness at higher volumes, I have swopped speaker cables around and it's still the same speaker so it's not my amp or cd player or anything. Thanks in anticipation. The speakers in question are vintage Celestion Ditton 66s, I know I will have to probably wait a long time to find the replacement part required but these speakers are so amazing I won't give up on them. Failing that can anyone recommend a speaker repair Docter in Berks or Oxon please.

I have a pair of these myself. Brilliant sound. I can reccomend you try Audio Gold in
crouch end London. They have a website. Contact Ben Shallcross. Hope you get it sorted.
Sparki

[Laneyflower]

Thanks Sparki, have only just seen your message, I used to live in Crouch End. However, in the meantime, can anyone tell me please -----------

My mid-range drivers are called MD-500S. I have just found for sale an identical sized and looking mid-range Celestion drivers with exactly all the same technical specs (in perfect working order) but they are called MF-500s.

Does anyone please know the difference between the MD-500 and the MF-500. Both have exactly the same tech specs, same size and identical appearance. Could it be the MF is a newer version of the MD??????????/

[Laneyflower]

Answering my own question here. The drivers are identical except the MF-500 nominal loading is 50w, the MD-500 is 80w. I suspect the MFs are from C Ditton 44s. They are both impedence 8 ohms, range 0.5 to 5 Khz and (don't know what this means DIN 45). I am loathe to put in lesser volume drivers. Sparki, I am waiting to hear from a man in Denmark who repairs these, if no joy, I will try your contact in Crouch End, thank you so much for that

[glendean]

I had similar problem with the midrange in mine as well, a very faint distortion I could just hear on piano pieces. I new it wasnt the drivers as I had them recently updated with new capacitors.

So I purchase a couple MD500's from ebay that were suppose to be unused (kept for spares). I pulled out the midrange just a few days ago and put in one of the replacement speakers. Same distortion but ten fold worse. Thinking either my soldering job to the speaker lugs was to blame or the speaker had deteriated from dampness etc (is over 30 years old so can happen). So installed the second speaker and thankfully the sound was totally clear, no distortion at all.

Im no speaker expert but thougt the midrange being a dome speaker would be impossible to recone. You may have to be patient and wait for a speaker to show up on ebay. They seem to show up every three months or so. Hopefully it wont be a dud.

The image you provided looks exactly like all four of mine so I wouldnt worry about looking for missing dust covers.

Regards

Glen

[Laneyflower]

Thanks for everyone's help and advice. Sparki, Audiogold referred me to a gentleman who repairs and rebuilds speakers for them including these particular mid-range ones and I am about to send it off to him for repair for the sum of £52 which includes carriage back to me. He is obviously very experienced and is just today returning to somebody an identical one of these very drivers that he has repaired the coil in! I will post on here with a hopefully happy ending when the speaker is returned and back in it's cabinet!!

[ToneDef]

Hello, i have the same celestion ditton 66's, very happy with them also.
Can you put me in touch with the fellow that repaired your MD500's?

Also check this link out, you may find it very interesting>

http://www.diyaudio.com/forums/showt...84#post1260884

[pixelthis]

Have you tried the obvious? Sometimes a midrange starts to fuzz just because the screws that lock it in aren't tight, or the wood/MDF/particleboard it's screwed into gives way. I've had this happen to me on 3 different speakers now. Some screws just don't get along with MDF all that well.

Hopefully your driver swapping will reveal a bit more to us.

Try bolts and washers (a relatively new invention) and if all else fails real wood
might be nice.
Manufacturers have a reason for using MDF for their speakers, they're cheap.
Not being a smart-aleck but I thought the main reason to build your own speakers was the advantage of using real wood (scared of termites?)

[kexodusc]

Manufacturers have a reason for using MDF for their speakers, they're cheap.
Not being a smart-aleck but I thought the main reason to build your own speakers was the advantage of using real wood (scared of termites?)

Holy thread revival, Batman.

MDF isn't a shortcut. Only recently have I seen speakers below $1500/pr start to use MDF of decent thickness. Most still don't. My old PSBs and Paradigms didn't use MDF, they took shortcuts. MDF is more expensive than the cheaper pressboard/particleboard materials used by a lot of speaker companies. And, MDF is only cheap compared to some oak and birch plywoods. But if you include the cost of finishing MDF with veneer, it's not usually cheaper.

Real wood isn't used very often because it's very hard to find solid wood with perfect consistency that isn't porous, doesn't have knots or other imperfections, and won't deteriorate or warp quickly over time. There's a lot of extra effort involved for no measurable performance improvements (though probably a lot of make-believe ones). Some quality birch and oak plywoods are generally preferred to real wood, yet give that real wood effect.

Having used MDF, birch, and oak plys, I still prefer MDF. It's synthetic, so its consistency is near perfect, it's dense and consistently stronger, or at least stronger for less money. This results in lower cabinet resonances and better damping from superior structure - better sound. And it's way easier to work, cutting and routering MDF is way easier than a lot of wood and plywoods. Rounded edges, countersunk drivers, angles, etc. Everything's just a bit easier.

I found the birch and oak plys to be pretty close though, a bit harder on my bits maybe. They did save some time on the finishing aspect. Sound wise, some people claim to be able to hear the difference - I cannot and tried awfully hard to.

MDF is nasty bad stuff though - I somehow manage to eat a few ounces everytime I work with it, despite masks/respirators etc.

[GMichael]

Holy thread revival, Batman.

MDF isn't a shortcut. Only recently have I seen speakers below $1500/pr start to use MDF of decent thickness. Most still don't. My old PSBs and Paradigms didn't use MDF, they took shortcuts. MDF is more expensive than the cheaper pressboard/particleboard materials used by a lot of speaker companies. And, MDF is only cheap compared to some oak and birch plywoods. But if you include the cost of finishing MDF with veneer, it's not usually cheaper.

Real wood isn't used very often because it's very hard to find solid wood with perfect consistency that isn't porous, doesn't have knots or other imperfections, and won't deteriorate or warp quickly over time. There's a lot of extra effort involved for no measurable performance improvements (though probably a lot of make-believe ones). Some quality birch and oak plywoods are generally preferred to real wood, yet give that real wood effect.

Having used MDF, birch, and oak plys, I still prefer MDF. It's synthetic, so its consistency is near perfect, it's dense and consistently stronger, or at least stronger for less money. This results in lower cabinet resonances and better damping from superior structure - better sound. And it's way easier to work, cutting and routering MDF is way easier than a lot of wood and plywoods. Rounded edges, countersunk drivers, angles, etc. Everything's just a bit easier.

I found the birch and oak plys to be pretty close though, a bit harder on my bits maybe. They did save some time on the finishing aspect. Sound wise, some people claim to be able to hear the difference - I cannot and tried awfully hard to.

MDF is nasty bad stuff though - I somehow manage to eat a few ounces everytime I work with it, despite masks/respirators etc.

Yes, MDF does have better sound characteristics than most "real" woods. I use it on my DIY speaker projects as well. I didn't even flinch when I saw they use it to make the speakers I just ordered.
But Kex man, don't breath that stuff in. It will kill you. I know, I know. Easy to say, not so easy to do.

[kexodusc]

Yes, MDF does have better sound characteristics than most "real" woods. I use it on my DIY speaker projects as well. I didn't even flinch when I saw they use it to make the speakers I just ordered.
But Kex man, don't breath that stuff in. It will kill you. I know, I know. Easy to say, not so easy to do.

Bah, a little formaldehyde never hurt nobody...

[GMichael]

Bah, a little formaldehyde never hurt nobody...

Tell that to all the frogs in Biology classes all over the world.

[kexodusc]

Tell that to all the flogs in Biology classes all over the world.

Man, what medieval school did you go to where biology class floggings were the norm?
Funny thing, that stuff is used as a preservative - you figure it'd help ya. Guess that's only if you're a mummy.

[GMichael]

Man, what medieval school did you go to where biology class floggings were the norm?
Funny thing, that stuff is used as a preservative - you figure it'd help ya. Guess that's only if you're a mummy.

I was hoping that I changed that before anyone saw it. Oh well.

Sure, it preserves. It preverves death.