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Multi-Way Conventional loudspeakers with crossovers

celestion 66 needs Mid-range
celestion 66 needs Mid-range
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Old 31st October 2012, 04:47 AM   #921
reggie is offline reggie  Australia
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Location: melbourne australia
Hello Alan (et al).

Thanks for the mention (your post #918) and thanks again for your efforts on my/our behalf. After 8 years of retirement I sometimes forget people have other things (meaningful things) to do every day.

Re: Paul Speltz interconnects – I swap between home- made with cat 5 cable; home-made with pure silver wire (with Teflon cover) with Eichmann connectors and Mapleshade pure copper foil “Ultrathin”. I have to be honest. I really cannot hear a difference so I’m not about to try anything else.
Re: existing crossover wire – The original wire appears to be long gone. I guess when the crossovers were re-done in the 90’s.
Re: Bi/Tri wiring. It would be interesting to tri-wire, at least initially with my new external crossovers to come. Also, one (of) the beauties of mono-block amplifiers is that they can be placed close to the speakers. Hence minimal speaker wire.
Re: SBA’s comment (post #914) regarding new woofers and baffle treatment for the 66’s. Firstly I look forward to your further coverage of the diffraction problem and secondly: is there a reasonably priced “better” 12in woofer replacement available for the 66’s??.

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Old 31st October 2012, 10:58 AM   #922
nigel pearson is offline nigel pearson  United Kingdom
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This has been a very enjoyable thread . It is almost like a fishing competition where naturally other fish will appear . To understand the Ditton 66 ( Thames Ditton Surrey , also called Rola , Celestion ) it is useful to know what was going on in the river so to speak . Some see the Isobarik loading and ABR as valiant attempts to do a little better . My experience with ABR is rather good . The Klipsche Forte looks to fail before it begins . Not so , it is rather good . I owned a pair Dynaco A25 ( ? ) . There had resistive port loading as did Proac ( CELEF , half Celestion , half KEF ) . Royd had a variation of port loading which I wish had come to production . Two identical frequency resonant port arrangements where the tubes were different lengths and diameter I believe ? The net effect was to reduce port turbulence and I suspect Q .

KEF had something a bit like Isobarik in the 107's . Strangely for them paper cones . Sadly when a company tries harder people show less interest than would seem logical . I can only imagine the KEF followers didn't approve . The KEF CUBE active EQ device might have been the reason . In the words of the KEF Rep the EQ box was KEF and KEF are not amplifier people in the eyes of the buyer . The 105 was better received , although to me out of Concerto and 107 was my third choice . The B&W 801 was I suspect hatched out of seeing KEF 105 .

I liked the idea of blocking off the ABR . Two speakers for the price of one . How like the Ditton 44 I wonder ?

We had this with British motorcycles . BSA Norton , AJS-Matchless , Royal Enfield .Seemingly as different as chalk and cheese to their supporters . In truth all clones of the Triumph twin ( which was derived from a Riley Pathfinder engine , and back into Daimler Dart V8 ) . Same river really .

The standard solution to diffraction was to put the unit in a glass sphere ( a light fitting ) or better . A friend has done this with his Leak speakers . As the 12 inch bass unit is almost a sub woofer it presents less problems than expected with integration . This has progressed to an open back design with no parallel sides . Other speakers had the unit raised up on a shaped step . 105 being the first mold breaker ( also Leak ) .
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Old 13th November 2012, 05:07 AM   #923
DennyG is offline DennyG  Australia
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Default Update on USB audio interface & pair of 66's: $1225

I now have a 2nd hand M-Audio 'USB Audiophile' audio interface for future spkr testing. Not tried it yet but it has reasonably good specs and zero latency apparently.

A Sydney, Australia pair of 66's just went for AUD1225 on ebay: Item 221147740783
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Old 15th November 2012, 01:43 AM   #924
TechnoDweeb is offline TechnoDweeb  Canada
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Location: Ottawa, Canada
Wow! I've been browsing as a silent listener for a while now, and I am amazed at the knowledge, talent, and good will on this forum. It is the reason I joined back when I was waiting to get my Celestion 66s. Now I have them and I am sad to say, I am finding them harsh to my ears. Having read this thread, I am really not worried, as I believe I will fix that harshness either through recapping/restoring the 66s, or by restoring my MAC1900. As a temporary fix, I have thrown in an EQ to smooth out the harshness.

Soon the snow will be falling, and I will have time to start really digging into these babies. In the meantime, I have been given a dead NAD 7240PE to practice with.

SBA, the 4100 is a really nice beast. If I find one, I will definitely jump at it! I find myself browsing kijiji daily with the hopes of finding new treasures.

Alan, I will definitely be taking pictures as I open up the 66s. In talking with the original owner, he thinks he left the original wiring and definitely did replace the caps with electrolytics. He said 22 years ago he knew a lot less than he knows now. He does regret putting them in.

I will be following your suggestions on this thread. I am really looking forward to it. I have never learned so much theory on one thread before. Thanks for everything!
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Old 1st December 2012, 08:01 PM   #925
alan-1-b is offline alan-1-b  United Kingdom
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Default Technical , Music recordings and other comments ; Diffraction

G'day reggie , and all interested readers here ,

I'll post some replies to reggie from #905 on page 91 , and also from #921 on this page , and include some other points relevant to upgrades.

Originally Posted by reggie View Post

1(a). I have played with the tweeter polarity so many times now. The present iteration is that the polarity is reversed at the tweeter terminals. However my pre amp is a valve OTL (a TRAM 2) which the designer, Thorsten Loesch, said reverses polarity so my speaker wires are reversed at the power amps. I have also tried reversing only the midrange. I’ve tried all combinations but cannot truly say I hear a difference. Also, I’m not sure what the polarity is at the crossover itself. Regarding the recessed HF It may be relevant to quote from a review compiled by High Fidelity Magazine on the “Ditton 66” (wood faced) in the late 70’s....”Triangles, bells and such, which have their energy concentrated almost exclusively at the higher frequencies, are reproduced very well, albeit perhaps not quite in perfect loudness balance with the rest of the orchestra. In listening tests the reduced relative high-end response shows up mainly as a lack of sparkle and transient response that, though fairly good, is not up to the best we have heard. On the other hand, that same characteristic lends a sweetness to the sound that is quite appealing. There is no trace of harshness or hiss and yet the highs are indeed there – right out to 16kHz...” Is this relevant?
1(b). I have had wool felt around the tweeter (and midrange) since early last year. I got the idea from some of your earlier posts and from a 2005 article I found on the internet by a David Ralph entitled “Diffraction doesn’t have to be a problem” (www,speakerdesign.net). What I seemed to achieve was a greater focus to the music.
2(a). I will go back and look for the advice you provided to DennyG re listening to violin music.
2(b). I have 3 classical CD’s: (i) Beethoven Concerto for Piano, Cello and Orchestra in C combined with Boccherini’s Concerto for Cello and Strings in G (ii) The Best of Boccherini and (iii) Pegolesi”s Stabat Mater with Gillian Welsh soprano (which I really like) but in general I’m more middle of the road, with some left of centre stuff.
3. Ok
4. Ok

What I’m hoping to get from this is: (a) improved clarity (which I interpret to be a greater intimacy with and insight into the music, (b) a tighter bass (nb. I’ve closed off the bass reflex speaker with no readily apparent loss of bass (my speakers are near room corners) and (c) maybe a small increase in efficiency (to get the Celestions to sing I have to turn up the volume slightly more than my wife appreciates)(even with the door shut). Quoting again from High Fidelity Magazine (stop me if you’ve heard this before)...”Although the efficiency of the Ditton 66 is about 3 and ½ dB below what we have come to consider average – CBS reports an on-axis sound pressure level of 83 and ¾ dB at 1 meter from a 0.dBW noise level, 250 Hz to 6kHz – it is an easy speaker to drive. The impedance curve is relatively smooth and well contained. Except for a 22.5ohm peak at resonance (49Hz) the load stays between 4 and 10.5 ohms throughout the audio band. We rate the impedance as 4.6 ohms (the minimum reached just above resonance) but over the important midrange the curve averages about 2 ohms higher: low, but not so low as to be dangerous...” and so on (there’s more of this technical stuff).

Several more questions please. Given my desire to try the Morel midrange at some future time (the MF500’s are not going to last forever - they are already 36 + years old and I need the Celestions to last another 20 years (I’m 63) will these new crossovers be compatible?

1(a)- it seems your brain/hearing does not give priority to Polarity.
Be grateful for that , because for some listeners it is a priority ,
however your brain/ear will likely have another type of priority that some of us do not have.
I will try to discern what it may be from your posts , and hopefully address it in replies.

Celestion's original plot of Amplitude versus Frequency for the 66 shows a slightly lower output of about -2dB , { if I am remembering correctly } ,
for Treble from their HF2000 relative to upper midrange output from the mid-dome ,
and that is in accord with the Listening Test comments made by the "High Fidelity" magazine reviewer.
The SEAS tweeter I have been recomending will not be -2dB with relative to the mids , nor will Hiquphon OW1 ,
and your Hiquphon OW2 will have higher output than the mid-dome , but we can get it to match closer in level.
1(b)- I recommend to DennyG and sba , and to TechnoDweeb if you are intending to do some measurements ,
that you go to :
David Ralph's Speaker Pages
and read the four articles in the "Diffraction" section if you have not yet done so.
There is some other useful stuff in Dave's pages also , and maybe more as I have not had time to read it all yet ,
but thanks to reggie for posting about this web-site !
2(a)- to be continued at a later time.
2(b)- (i) and (ii) - Boccherini was a Cellist , thus if the two recordings you have are of good audio quality they will likely be useful to evaluate the relative levels and quality from the mid-domes versus the lower midrange from the woofers , as Cello covers all of the midrange , and in fact covers from upper bass to upper mids well.
The other instruments on these recordings , if well balanced in the recordings , will give some references around the complete frequency range of the 66.
(iii) - Pergolesi's "Stabat Mater" is excellent music to use to assess from upper bass through to treble with the instruments , and the two vocalists cover from lower to upper midrange , and a little into the treble for the soprano singer ...
and she will likely be Gillian Fisher on this recording reggie !
if it is the one on Hyperion label with the Kings Consort and Robert King.
The Hyperion recording has very good audio quality.

Gillian Welch , { if spelling is not Welsh } , is a USA singer of a roots type of folk and country music , sort of a development of Appalacian music and related { used to be called Hillbilly music years ago ! } and which is not highly commercialised Nashville C&W ... thankfully !
I have her first three albums , and all are well enough recorded to be useful to assess the relative quality of output from loudspeakers.
(3)- refer to about the Cello recordings above.
(4)- The upper bass problem may be owing to how you have blocked off the ABR/passive radiator.
Is it still in the cabinet , and with some thing fixed over its front ? ,
or , is it removed and something fixed into the open space ,
and if this latter then how thick and stiff is the new fixing and how well sealed so no air gaps around it ?
New point: (9)- so you have no ABRs , new tweeters , think you may change the mid-domes , and later ask in #921 about alternate woofers ...
what is it that will still be a Celestion 66 ?

You likely do not need alternate woofers - are yours in any way damaged ?
Can you attach the entire "High Fidelity" magazine review here , including any plots and technical measurements ? ,
or if not , then please what year/month/volume or issue number is it , in the event someone may be able to find a copy ?

Last edited by alan-1-b; 1st December 2012 at 08:07 PM. Reason: to add two sentances
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Old 8th December 2012, 09:30 PM   #926
TechnoDweeb is offline TechnoDweeb  Canada
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Well, It looks like I will be starting the 66 recap project soon. First I need to resolve a problem on my MAC1900 of the left channel shutting down. Is there a thread here on troubleshooting a MAC1900? I suspect that the 1900 may force me to go all out now. Doesn't make sense to fix one problem only to get hit with another shortly later, and the age of the MAC1900 is around 1973/74 timeframe. I opened it up last night and was really impressed with the quality of workmanship inside this beast. It is rather ironic, as the left channel cut out after a brief crackling, just before I left home to pick up a pair of gorgeous Celestion Ditton 44s with nicely sun bleached rosewood enclosures. After I reseated the MACs cards and inspected for obvious problems, I ABed the 44 and the 66, and then the 44 and my Tannoy MX4s. The 44s won the comparisons, and that included having my daughter and houseguest as unbiased listeners. Grandson said too loud, and covered up his ears.

A bit on my background. I studied industrial controls and ended up with a 23 career with Digital Equipment Corp, Compaq Computers, and then finally another company that shall remain un-named. I have worked extensively with oscilloscopes at my first job in the R&D department of a small CAD/CAM company in the mid 80's. We designed, built, and fixed custom boards to enhance the throughput of the CAD/CAM systems, so I leaned to wire-wrap, troubleshoot, and repair down to the chip level. From there, I went to Digital field service, where I worked on PDPs, VAXes, and Alpha servers along with all types of tape drives from the large 9 track drives utilizing to 4 ml DAT drives. However, I have not touched anything like this since 1999. As you can see, I am definitely not an analog audio person. It is a whole new world for me. I did design and build a pair of bass reflex speaker cabinets in the late 70s, and they sounded pretty good on my Marantz 2235(?), I think. I am certain I will need help as I walk through this process.

Fortunately, I still have my Weller soldering station, Tektronix oscilloscope, and a couple of Fluke multimeters (models 73 and 75), as well as the soldering and desoldering skills and techniques required to repair temperature sensitive IC chips.

I digress. My goal is to get the MAC working so I can run the 44s on it, and that will allow me to listen to beautiful music as I work on the 66s. I will be taking lots of pictures, which I will include either on this thread, or a new one if I need to. This has become an obsession for me. I am also enjoying the people I've been meeting in my pursuit of this passion. I've met 3 really nice guys with the same passion as mine, and surprisingly enough, the same appreciation to similar music.

As I type this message, the MAC 1900 is drifting a little. Now the right channel is drifting in and out. Should I stop playing it? Do you think the 44s are overdriving this receiver? I ran it with the 66s for well over a month with no issues, but maybe this is just the symptom of the problem. I suspect I may have a transistor on it's last legs. Need to get out the theory books on troubleshooting transistors...
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Old 9th December 2012, 03:39 AM   #927
sba is offline sba
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That's a bummer technodweeb.

You can get help at Terry Dewick's MAC thread --

McIntosh - Hints and Kinks - AudioKarma.org Home Audio Stereo Discussion Forums

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Old 9th December 2012, 05:26 PM   #928
TechnoDweeb is offline TechnoDweeb  Canada
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Thanks sba!

I've just finished going through the whole thread. Tons of information on it.

Here is what I think has happened to me. The MAC1900 is able to drive 4 to 16 ohm loads, however I have always been nervous about the 4 ohm loads after reading a few comments on threads. But I've been even more nervous about drive a 4 ohm load on A, and an 8 ohm load on B.

Friday night, I had forgotten both A and B on, and I think I was driving mixed loads. The MAC shutdown the left channel to protect it after driving both loads for about an hour. Last night, I was reorganizing my set up for the 44s, and I had a flakey contact on ground of the right speaker, and I think the MAC shutdown that channel as a result. After I had completed the new set up, I have been running the MAC continuously with no problems. Mind you I suspect that some of the components are at borderline of tolerances so it doesn't take much to push it past, and initiate circuit protection. If I am right, it seems the protection circuitry actually still works!

Now hopefully, I have some time to play with the 66s. Stay tuned...
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Old 29th December 2012, 07:30 PM   #929
alan-1-b is offline alan-1-b  United Kingdom
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Default types of Felt and application to 66 ; Mac 1900 with Celestions

Hi TechnoDweeb ,

you are right to be cautious about using your Mac 1900 with 4 ohms to one set of outputs when simultaneously 8 ohms to the other set of outputs.
I would not do it.
I do not have a McIntosh amplifier , though I know these are very good amplifiers ,
however almost no amplifiers will drive a pair of 4 ohm l'speakers simultaneously with another pair of l'speakers of any impedance.
If you need to drive 4 loudspeakers simultaneously than buy a Krell amp ,
or a dedicated 4 channel amplifier.
Celestion 44 and 66 both vary in load between 4 and 8 ohms , and both have fairly steep phase angles over parts of their impedance.
-{see the Impedance plots that some participants have posted in this thread}-
When high phase angles in the impedance the amp has to supply greater voltage and current than when low phase angle/fairly flat impedance ,
thus amp is working hard enough driving a 44 or 66 pair without adding another pair !

From your description of their sound it seems the caps in your 44s are in OK condition still ,
but I would soon replace the 24uF or 30uF -{whichever is in the midrange filter}- soon ,
because if it starts to leak significantly the mid driver will be damaged.
There is a Celestion 44 thread I have posted a lot in here:
Crossover nightmare!!!!!!!
started by:
*** *** *** *** ***

For Diffraction control , and following the information posted by reggie and the Link I posted above in #925 , look now at:
SAE & Sheet Felt
for technical specifications about Felt.
The relevant specifications for sound absorption are:
Wool Content - preferably at least 95%
Air Perm - the highest number possible
Noise Reduction Coef - the highest number possible , and note that this will always be less than 1 , it will be a decimal , eg: 0.52 .

Ignore all the other specifications listed , as those are for other applications.

SAE specification felts are best , buy at least SAE F-5 , but F-10 is much better.
-{David Ralph used either F-11 or F-13 as he couldn't get F-10 , but those are less wool % and not as good for what we are doing}-
F-10 is more expensive but is worth it.

If you cannot find or afford SAE felt , then buy "Industrial" felt that has an S rating.
S1 is the softest and most absorbent for sound , and is 95% wool.

If you can only buy unspecified felts then buy Soft or Very Soft , and not Medium , Firm , Hard grades ,
and ask for 100% wool.
Composites , usually Wool + Rayon , even if Soft grade , are not as good for what we are doing .
-{ but they could be used inside enclosures that use later era Plastic cone drivers }-.
Unspecified felts are usually known as Craft Felt , and are available from Craft stores and Haberdashery stores ,
but usually these are no thicker than 2mm , which is OK to soft roll up to stick under the top lip of the 66 enclosure , but not suitable for the David Ralph described applications.

You may find a Soft felt sold as Saddle Felt elsewhere , but I do not know how thick those are ,
and most are likely to be equivalent to Medium or Firm grades.

More attractive to look at than what David Ralph has pictured , and somewhat better for sound absorption ,
is to cut a Star shape out and use the remaining piece around the tweeter.
A 6 point star cut-out is best , but a 5 point will suffice.
4 points are not sufficient.

The inner point of the felt frame must be at the Top and pointing down to the tweeter , and it can go over the tweeter flange to almost to the dome.

Alternately , cut a Star cut-out for the top , and a zig-zag of Acute angles down the 2 sides to make a frame to go around tweeter and mid-dome with no felt in between the drivers.

Acute angles present much better surfaces for absorption than 90 degree angles and Obtuse angles.

If you have a large piece of felt it can cover to almost the edges of the front panel to meet the raised edge section.
Suitable thicknesses are available , but you will likely have to buy Mail-order.

I have to go now - will return when time available.

Last edited by alan-1-b; 29th December 2012 at 07:31 PM. Reason: to add a phrase
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Old 30th December 2012, 01:28 AM   #930
TechnoDweeb is offline TechnoDweeb  Canada
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Thanks for the information Alan!

Things have changed here again. This will be my last posting on the Ditton 66 thread, but not on the Ditton 44 thread. I found a fully restored Sansui 9090 last Saturday, and traded my 66s for it and some cash. I also bought a pair of Kef Concerto's on Sunday with the cash. I was having buyers remorse because I felt I had spent way more than I wanted to on the 66s. This trade leaves me feeling better about things. Now I have enough clean power for when I want to crank it up. I'm getting closer to the sound I am looking for. And I look forward to working on the 44s.

My only regret is that I never did open up the 66s, but I did get some pictures of them. I think I said they were brownies before, but they are actually blackies.

One last point of interest is that the 44s have felt around the tweeter. I wonder if putting felt around the 66 tweeters would have sweetened them up?

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