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Old 15th April 2014, 09:43 PM   #1051
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Glad the tweeter phasing works . As said both are wrong . The BBC sound seems to favour the so called out of phase option . This produces the recessed mid-band and gives an illusion of greater depth . This wrongness is 2 db typical . Mordaunt Short used the opposite phase and had a sound much loved by Naim owners .

The Fostex I thought of are these .
Fostex FE103En DIY Bass Reflex Bookshelf Speakers / Nearfield Monitors

About phasing . I was given some JPW Sonata speakers to give to a friend . The tweeter was so dull as to sound disconnected . I had to play the tweeters alone to be certain . A series resistor was removed and the phase reversed . That was just about OK . I doped the cones with PVA glue and used some scraps of high grade damping to fill the boxes . Blutak gaskets . After a week I realized they had become rather nice speakers , plenty of reverberant detail . Only when they went I missed them . Some LS3/5A a friend has not automatically better . The Sonata cabinet is nicely made if wondering . I would say 1 star to 5 star at almost no cost . The PVA was a risk . It worked . I have repaired ancient radios with it . All sound better . That wasn't the aim with old radios .
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Old 16th April 2014, 03:56 AM   #1052
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OK I managed to sort out the bass problem. My first thought was the crossover.. But after having it reviewed all is well. Checked every wire. Then I realized that the Ditton 66s I acquired came with a slightly different bass driver - I believe it's the newer version, it had a much larger dust cap. Anyway, I thought maybe this is the culprit, it may have different specs. I threw in the older bass drivers and voila! The bass problem is totally gone. Whew that's a relief, I thought I was going to have to reuse the old crossovers which I didn't want to do, I think it's important the coils have space between them.

Now that they are working properly I'll get some listening in and report back.


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Old 16th April 2014, 02:27 PM   #1053
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Sorry for the double post here, I'm a little confused about something between version 1 and 2 of the 66.

I've been reading that the crossover in version 2 (the PCC model) is different as in it has a steeper 24dB fourth order linkwitz-riley crossover.. however, when I look at the schematics for both the TBC and PCC model, they look identical.

What I'm trying to get at here is what difference did they make to the crossover with the newer bass driver? Clearly something has to be different, because my handmade crossovers that I took from my custom celestion 44 project use the inductors from the TBC crossover, yet when I plugged it into my 66s which have the newer bass drivers (the bigger dust cap) the bass driver was too loud, pop in the old bass driver as I described above and the bass goes back to normal. Yet, looking at the crossovers, nothing seems different, except one is tidier looking than the other, and the TBC model used a 30uF capacitor on the mid filter vs. a 24uF capacitor, but that shouldn't affect the bass driver. Any ideas?
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Old 20th April 2014, 02:52 PM   #1054
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Hello all, I have a pair of ditton 66 speakers that I got about a year and half ago. The tweeters are burnt out and I have have been able to get two used on ebay $$$$.
They are 4.5 and 4.7ohm readings. I was wondering if that is the standard for the 66's units.
I have been going over all your info on this post and have enjoyed it and also been confused many times. Lol
I have removed my crossovers that are the old style not printed board type.
I ordered new caps and resistors to match the specs of the printed curcuit style crossovers and their values.
I am still kinda wondering if and why I need to wire in the other resistors? The values I got were 1R for the 72uf, 1.5R for other 72uf. Base
1.8R for 24uf line and 2.7 for 4uf. Mid
None for the tweeter side. Does this sound right.
I am using all original ditton speekers.
Really looking forwards to being able to enjoy these speakers.
I am totaly open to any other ideas that might help to improve the sound of these.
I will post pics as I change up the crossovers.
Thanks all
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Old 21st April 2014, 04:32 PM   #1055
Qwin is offline Qwin  United Kingdom
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Jeffery88 - I have only recently aquired 66's and have been wading through this very long thread and other sources before starting any work on my own x-overs.

There is much confusion about 66 models but as far as I have been able to uncover it goes like this:

Series Two is a compleately different design and the ABR is round the back and not on the front baffle. They really should have called this something other than 66 but were perhaps wanting to build on the 66 reputation, it is rare in comparison.

There never was an official MkI and MkII models of the 66. The product was continually updated throughout its life, but some of the changes roughly coincided with the change of the front baffle from the original Black painted (Blackies) to the later veneered baffle (woodies). Owners have started refering to the earlier versions as MkI and the later versions as mkII, not to be confused with the much later Series Two mentioned above. The boundries for changes are blurred and some blackies had some of the later features in them and some of the woodies had earlier ones probably due to cross over in stock of new/old parts. Later Woodies had PCB x-overs but some of the first of these had the older tag board x-overs. Even the tag boards varied, the very first Blackies had air cored inductors which later where wound on to plastic bobins.

Later Bass drivers had a larger dust cap but performed the same I believe.

The mid driver was originaly the MF500 which was later changed to the MD500 of identical appearance. The later mid had a higher power rating and from 50w it went to 80 watts. But the earlier mid had a flatter extended frequency response to above 6kHz and B&O used this in their 5700 model crossed over at 6k. The later MD driver barely makes the 5K crossover point used for the 66's, don't ask me which is the better sounding driver I have read claims for both. The change over point seems to have been roughly when the Woodies came on line but I could'nt swear to it.

The HF2000 tweeter fitted in the woodies with the PCB x-over were type T.2373 and had a pair of caps with a combined value of 6.2 uf in the circuit. The earlier version of the tweeter was T.1637 and used a value of 6.0 uf. In addition, there was a midrange change of capacitance in the x-over from 30uf (for MF500) to 24uf (for MD500). They used different multiples of caps from time to time to create the same total values, appart from that, the x-overs didn't change in terms of schematic from first to last production.

I hope you and others find this helpfull, I think I've got it right, please jump in if anyone knows to the contrary.

Last edited by Qwin; 21st April 2014 at 04:37 PM.
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Old 21st April 2014, 10:32 PM   #1056
Qwin is offline Qwin  United Kingdom
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Silversurfer1 - electronics is not my field so I am only going off what I have read in the thread.

Tweeters - mine both measure 4.7 Ohm so yours are in the right area.

The reason we add the resistors in series with the capacitors is that the original low quality Electrolytic capacitors had a reasonably high resistance. When we replace these with modern Polyprop caps which have a fairly low resistance we are changing the circuit characteristics, so we need to add additional resistors to get back to the original values and have a circuit that functions the same as Celestion intended all be it with better quality parts.

Now the question is, what type of capacitor are your replacements eg the 72uf?

The reason we don't need the resistors in the Tweeter circuit is that Celestion used a better quality film cap there, that has a low resistance similar to the replacement Polyprops we will be using, so resistance will be roughly the same.

I am in the same position as you as far as trying to work out the values of resistors to add and I think you have it right apart from the 2.7 Ohm for the 4uf, I think this should be 3.3 Ohm. The chap that was using 2.7 Ohm had 3.3 Ohm in his other speaker and the difference was to address an inbalance in the output from his two mid range drivers. 3.3 is the correct value normally I believe - you could really do with alan-1-b comming along and confirming this as he seems the authority on this, and I could also do with that point being clarified.

I hope I have put this in a way that makes sense to you.

Last edited by Qwin; 21st April 2014 at 10:37 PM.
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Old 22nd April 2014, 04:03 AM   #1057
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Qwin, Thanks for the response to this post and my questions. It sounds like you have gained a great deal of info on the ditton 66's.
The resistor install makes sens and know I remember. I am using Axon for the 72uf in the form of two 36uf. I think they are close to the solen caps and clarity for mid and hi.
Yes Alan-1-b really knows his stuff and these speakers.
I pulled these figures from a drawing that was posted on page 85 #845. By Denny G. The values were recomended from Allen-1-b but yes maybe some changes were made afer.
That is one reason I posted to see if anyone else found something better.
This is a great post on these speakers and I enjoyed your input to help bring light to the history and changes they have gone through.
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Old 22nd April 2014, 09:31 PM   #1058
Qwin is offline Qwin  United Kingdom
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Silversurfer1 - You could be right about the 2.7 Ohms for the 4uf cap.

So many different conversations and some values are to correct driver inbalance so it gets very tricky to work out what to use.

I thought I would post these measuremants taken from one of the x-overs in my "Blackies" Some folks might find the values of use.

Click the image to open in full size.
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Old 25th April 2014, 01:42 PM   #1059
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Hey Qwin, Great lay out of your crossovers! So i noticed that you have the 30uf in the mid. Are you going to replace with the 24?
How close are you to re capping these baby's?
I noticed that the values are not to far out, How do the speakers sound?
Do you know if the tweeters are the original ones?
My caps should be hear soon so looking forwards to being able to enjoy these bad boys.
Have fun
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Old 26th April 2014, 02:55 PM   #1060
Qwin is offline Qwin  United Kingdom
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Silversurfer1 - Hi I will be going with the 24uf when I build new crossovers. Sticking these back in while I work on them.
Not heard mine or any other 66 for that matter, bought them purely on reputation. If you want to see my progress check out my thread on the Art of Sound linked below.

Renovation of Celestion 66 Studio Monitors
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