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Old 14th March 2007, 06:10 AM   #21
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Hello, sure I can test, predictive reliability of the old product under expected / unexpected conditions, tells me weather I can recoat/salvage or toss, if yours is badly cracking etc, well……………………….if this was the space shuttle this all would be mute. Coils touching is bad right? Heh.

1- coils appear ok with that test ;-).
2- under a large mag glass look for any cracking at all, and of course the color and shape change; I used a specialy made curved feeler gage.

I took a very small needle and tested for adhesion and flex of former & coil, remember this is a 3-piece unit! The coil former is very stout, it's the rest that concerns me. However I treated mine just for added measure… over time the hair leads loosen at former pass point, this must be fixed too!

Guess I should ask> have you removed the coil from the gap? This is not a suggestion just a question? Note: When I cleaned the gap I actuality hade pieces of metal from the original machining process still in the gap! :-(......


I really wish I could just see this; it would be so much faster……….
For the time I have spent getting you started I could have assessed the work and been under way……….I have the glue types, removal products, jigs………..I just don’t have the time to do it for you right now…

I will be more than happy to help, i've been roped into putting a new stereo in my wife’s new Corolla as of late and it requires custom this and that…

Note: When you take all the screws out you must lift the whole assemble out level, if yours is not keyed, mark it for reference.


Until Next time.
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Old 15th March 2007, 05:33 AM   #22
Grahame is offline Grahame  United States
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Looks like I'll have to wait until you have some free time.

Now worries though, I've had these speakers long enough, I can wait a bit longer to put them right.

Any pictures you have of the process would be much appreciated, as they will probably make things a lot clearer to me.

E.g. after removal of the large round black, metallic collar/wire guard, what next - I didn't see any obvious way to disassemble further, and I didn't want to break anything.

I guess this one will run and run.

waiting patiently....

Hope everyone else in the same/similar situation is finding this conversation useful.

Failing repair, anyone have any ideas for drop-in replacements for the tweeters and / or mid dome than don't muck up the voicing too much. I don't know if I'd like the change, after all this time.
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Old 15th March 2007, 07:17 AM   #23
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Hello again

Ok if you want to go about it that way, after unscrewing it, lift it straight up, there are 2 rubber mats sandwiching something harder, lift all 3 up evenly! If you slip the coil former can be damaged beyond repair, so be very careful.
You will then have the entire 3-piece assembly out!
Take close up pics and send!
Hear we go!

I really am wondering how this is going to work over the Internet?

How much is freight to me at 97007.

I have decided to work up a price for you per unit restored, im just having this feeling your going to ruin these fragile assemblies. No offence it’s just hard/tricky work and none of the shops are doing it in fear of something going wrong, which can happen…..

Let me know your thoughts? There is an NOS stock set on eBay right now for 250.00 EACH !!!! Plus shipping, however, what people don’t realize are the glues and coatings vulcanize over time regardless of usage..............

Anyway let me know you’re thought, as I will need to do this soon, April will be impossible.

I’ve attached images i think?; do you have an email where I might just send you a pic of my finished unit?

Mike
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Old 15th March 2007, 07:19 AM   #24
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i'll ask a fellow if has anymore nos stock replacement diaphrams for the hf2000..........didn't know you needed those too?


Mike
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Old 13th April 2007, 04:04 PM   #25
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Hi tonedef2,

in the interim period I have looked but I cannot find the original Celestion brochures I had nor the old magazine which I think listed the cross-over frequencies for the 66, thus will comment below on a few things and you can post your responses if you , and Grahame, are still pursuing this 66 matter.

The slight metallic edge you wrote about in the other thread -{that we discussed new components for the cross-overs in}- remember that you have just reconditioned those domes thus after removing all the old stuff in and around them you have improved their Transient Response, thus faster sound - this can sound brighter- and remember that all domes do have a significant break-up resonance, and for that medium diameter dome its first break-up resonance will be in the Audio band, thus you could be hearing it more-so now.
Yes, the break-up frequency will be above the cross-over point, but not so far above and the cross-over slope will not be so steep in that speaker to have rolled down the level very much by the time the break-up frequency has been reached.
Did you hear any of that metalic edge sound before you did the restorations ?

It could be in the low end of the tweeter, as again owing to the only medium slope roll-off of that cross-over there will still be significant signal voltage at the tweeter's Fs, thus when the speakers are driven at higher volume levels the tweeters' resonance will be audible.

Similarly, the mid-dome will be operating not far above its Fs, thus it will buzz if driven hard. I'll hazard a guess its Fs is about 500 Hz - its not likely to be any lower.
You can find its Fs with a frequency sweep oscillator; a 6.8 ohm resistor -{ 5 watt}- and a voltmeter, or a DMM that is capable of close to accurate measurements in the Audio-band - some aren't, as their AC ranges are only designed to measure the Electricity Mains supply voltage and a few harmonics above.
Such AC ranges in DMMs can roll-off from about 400 Hz.

Those types of speakers, despite its size, were not cabable of clean sound at the higher volume levels that similar drive units in modern speakers are now.

The 66 is a cleverly assembled Compromise. All three of its active drivers are operating very close to the edges of their useable band-widths - woofer at its top end; mid-dome at both ends; tweeter at its low end - quite a feat for drivers of that period and a tribute to the quality Celestion were capable of - particually that woofer and mid-dome.

The HF2000, and probably the HF2001, tweeters were not great drivers. Better results can be got substituting those with a suitable ScanSpeak or SEAS or Hiquaphon -{spelling ? }- tweeter, but as some changes would need to be made to the tweeter Hi-pass leg at least of the cross-over, it is simpler to keep the Celestion tweeters if still work OK and their characteristic sound does not annoy. The old Kef T27 tweeters are not any better, merely different.

The ABR is the cause of the bass sound that Graham Maynard does not like, but to get loud lowest octave bass in that period - and buyers wanted such - that was one of the ways to achieve it. Again, its a Compromise, but with careful placement with regard to distances from walls in the room its quality versus quantity can be fine-tuned a little.
If back against the wall is the only placement option and the excessive bass is not wanted, then install a sealing gasket around the edge ot the ABR and screw a thick, stiff wooden panel across the front to block off the ABR entirely. So long as high volume levels are not required the active 12' woofer will cope OK and give tighter bass response.
I am presuming the user's Amplifier is capable of good quality bass here.

If I have understood correctly, your 66s tonedef2 are the same model as Grahame's in those photos he posted ..?..
Those cross-overs - the inductors look very well made and would be expensive to replace, thus keep those !
The dull green capacitors may be the old Film/Foil Polyester types of that era - is there any letters and numbers printed on them you can read and post here ?

Those look to be in the Tweeter filter - you can trace the wires to check this ..?..

The black encased axial capacitors are probably some type of Polyester, but whether Film/Foil or Metallized Film type I do not Know. Is there anything prined on them that you can read and post here ..?..

I've written a lot, and perhaps forgotten a few things, thus post any thing else about the 66s here, and I'll comment if I can.

You are very brave, and quite obviously confident and skilful, to have done that mid-dome restoration you have describe tonedef2 - I wish may hands to brain co-ordination was that good !

Regards,
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Old 13th April 2007, 09:33 PM   #26
Grahame is offline Grahame  United States
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Hi guys,

Googling back to this thread

http://www.diyaudio.com/forums/showt...188#post268188

Gives the Cross over values @

Bass [500Hz] Mid [5KHz] Treble

Quite by chance, the same query showed that someone is "parting out" a '66

e.g

http://cgi.ebay.com/Celestion-Ditton...QQcmdZViewItem

Check out his other auctions - we may have to act in concert on this


Re: The Bass - I recall mentioning the fact that I had '66's and got the reply - "ah - thats when they were interested in reproducing Organs and Steam Trains!" Subwoofers - who needs 'em!


Nice to know that the engineers back then knew the fine art of compromise, and could operate at the limits of the then current technology.

The ebay link has some photo's of the crossovers.

When I have some time, next time I open them up again, I'll try and get some better shots of the cross overs, and see If I can get the values off the components.

I'd still like to keep them true to the original vision if possible, failing that come up with some drop in replacements for the tweeters + mids + possibly a new crossover - but I'd like to avoid that if possible - having grown up with the sound of these - and being a cheapskate at heart!

My problem is that at "mild" volumes one of the Mids will buzz/break up - sounds like increased sibilance - just enough to be very aggravating - its a shame, as other than that I'm very happy with them.

G.
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Old 14th April 2007, 02:27 PM   #27
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Hi Grahame,

500 Hz is very low for cross-over to a mid-dome, and particually for a 2" dome of that vintage. I strongly suspect the buzz you are hearing is related to the dome being overdriven at its Fs, and likely in conjunction with its internal deterioration matters that tonedef2 described.
I do not know of any other domes that will simply "drop in", thus you would likely have to cut or some other way modify the front panels of your 66s to fit a different dome {or a small cone driver}, and the few affordable mid-domes will require changes to the cross-over, and none seem to be capable of any power capacity at 500 Hz even with a -6dB Linkwitz/Riley 4th Order - which itself is difficult to make work well for a passive cross-over at 500 Hz !
For the few current reasonably priced domes you would have to shift the cross-over point up to 800 Hz or higher, and that means changing the low-pass section to the woofer also, and probably all the tweeter filter, because all components interact to some degree in passive cross-overs, and especially so for all slopes > 1st order, and you will have to x @ > 1st order slope to mid-dome if keeping the x-over point low enough to work with the woofer.
The woofer may be able to be crossed over higher than 500 Hz, and I'd have speculated that it was - eg: 800 Hz minimum to that dome.

Be a "cheakskate" - so am I to some degree - but this time be sensible or you may have to later spend a lot of money, unless you have additional skills that I do not know about.

I strongly recommend you do either, and preferably both the offering options :-

(1) Buy that MD500 from the ebay seller - I see he has no higher bids yet. Take a chance it will be working at least almost as well as he says. It will cost you a lot more than that asking price to buy new domes and have suitable cross-overs designed, even if you then buy and assemble the components for them yourself.

(2) Take up tonedef2's offer to have your DM500s reconditioned. I am confident from his comprehensive descriptions that he knows what he is doing and has the skills to do the job.

If you buy the spare dome then you can send your faulty dome to tonedef2 for reconditioning, then compare the finished results with the other 2 domes you would have, then decide whether to send another one for reconditioning, and that still would leave you with one spare in case of an accident at any time in the future.

There is no need to upgrade to modern domes, as those ones do work well - I have heard them - perhaps the best of that type available then and better than the low budget ons in some speakers these days, and you do seem to like the sound.
Similarly, keep the tweeters at least for now, and till you hear the 66s with the faulty dome replaced.

Next would be to replace the old capacitors with a good quality for audio, polypropylene type, and listen to results to hear just what those mid-domes and tweeters are capable of.

We can discuss capacitors in the future, but for now be careful to not buy ones which may be of some-what larger capacitance than their specification as such will lower the cross-over points, and the MD500s will not like that, nor perhaps the HD2000s.

Do post any thing you can decipher that is printed on the old capacitors, as this will assist me to further consider the cross-over.
Can you trace the wiring and draw the circuit, including the Inductors and connection points to the drivers ?
I could then tell you the cross-over type at least in part.
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Old 14th April 2007, 03:23 PM   #28
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Quote:
Originally posted by Grahame



Nice to know that the engineers back then knew the fine art of compromise, and could operate at the limits of the then current technology.


G.

Some Engineers today can do the same, but problem is that Accountants basically run the Loudspeaker Companies and they follow the economic ideas of cut-and-run Bankers, which is to use the cheapest possible components and materials, but make the product look visually appealing, and forget about audio quality beyond it being able to make a half-way agreeable sound when operated within the Fine Print of the Warranty -{which most buyers do not read}-and only Service Life for long enough till the buyer has tired of it and the new model is out on the Market, so that the process can be repeated and more money brought in , etc ... you may know this already, and thus maybe why reading a DIY Forum !

Hey tonedef2, are you still out there ?
What say you to the above !

regards,
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Old 17th April 2007, 05:23 AM   #29
Grahame is offline Grahame  United States
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Default Woot! guess who won on ebay?

Quote:
Originally posted by alan-1-b


I strongly recommend you do either, and preferably both the offering options :-

(1) Buy that MD500 from the ebay seller - I see he has no higher bids yet. Take a chance it will be working at least almost as well as he says. It will cost you a lot more than that asking price to buy new domes and have suitable cross-overs designed, even if you then buy and assemble the components for them yourself.

(2) Take up tonedef2's offer to have your DM500s reconditioned. I am confident from his comprehensive descriptions that he knows what he is doing and has the skills to do the job.

If you buy the spare dome then you can send your faulty dome to tonedef2 for reconditioning, then compare the finished results with the other 2 domes you would have, then decide whether to send another one for reconditioning, and that still would leave you with one spare in case of an accident at any time in the future.

There is no need to upgrade to modern domes, as those ones do work well - I have heard them - perhaps the best of that type available then and better than the low budget ons in some speakers these days, and you do seem to like the sound.
Similarly, keep the tweeters at least for now, and till you hear the 66s with the faulty dome replaced.

Next would be to replace the old capacitors with a good quality for audio, polypropylene type, and listen to results to hear just what those mid-domes and tweeters are capable of.

We can discuss capacitors in the future, but for now be careful to not buy ones which may be of some-what larger capacitance than their specification as such will lower the cross-over points, and the MD500s will not like that, nor perhaps the HD2000s.

Do post any thing you can decipher that is printed on the old capacitors, as this will assist me to further consider the cross-over.
Can you trace the wiring and draw the circuit, including the Inductors and connection points to the drivers ?
I could then tell you the cross-over type at least in part. [/B]
Alan,

Like the title said, luck was with me today, and I should shortly be the owner of another MD500 and a pair of crossovers!

I'll let you all know how the "new" MD500 sounds, and I'll see what I can do about reading values off the crossover components.

As a point of interest, the crossovers in my cabinets are on a printed circuit board. The crossovers in the auction look like point-to-point wired.

Hopefully the circuit topology + printed values are the same in each case.

Is there any software/drawing tool that would help in the layout of the circuit?

When I have the cross over + capacitor values, I'd appreciate any help with sources, recommended brands, costs etc.

Looking forward to the fun(!) ahead.

Grahame
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Old 17th April 2007, 03:56 PM   #30
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Default Congratulations !

Grahame, I am very pleased for you that you have the MD500, and the spare x-overs - particually as you said those seem to be differently assembled than yours.
Hopefully those have the same value Inductors as yours, but if not, then which-ever is the later designed x-over will likely be the one to have the most suitable values of inductance in the filters for the MD500.
Check history on the alternate versions of the x-over with tonedef2 when he has time again -{from his above post it seems he is busy in April}.

Anyway, you will have one set of x-overs to change capacitors in, and the other to use as Reference - if same inductors.

Capacitors - I should have included in last Post to check those old plastic caps for Leakage - I have found such in old MKT {a metallized Polyester type}, and read of such occuring in old KT {a fil;m/foil polyester type} caps.
If leakage in one of the Series connected caps to either the MD500 or the HF2000 then the driver can be damaged as insufficient of the below cross-over frequencies may be received by the driver - not designed to handle the larger diaphram excursions that such would cause !

I recommend you do this before you install your replacement MD500, so as to not risk damaging it.
I will post how to check caps for leakage if you are not familiar with such. All you need is a 9 volt battery, or a low to DC volts wall-wart power supply; a DC voltmeter or DMM with DC range; and a soldering iron .

Time run out - have to post this before this computer shuts down !

regards,
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