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Old 10th Sep 2010, 7:24 pm   #41
Kat Manton
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hi,

I'm now conducting listening tests with 3 x 27Ω in parallel with the driver (Russian mil-spec 2% 10W), one 1Ω between crossover and driver (Welwyn W23), original Celestion crossover circuitry otherwise.

The idea is to present the original crossover with something like the load it was designed for while knocking a bit off the level to compensate for the higher sensitivity of the SEAS tweeter.

The (rough) computer simulation suggests this has ironed out a lump (9dB @ 15kHz) in the original response, produces a slight rise (~3dB up @ 20kHz) but has, overall, flattened the response off. That includes a flatter combined response of the mid and treble drivers. That's with simple driver models, a resistor and an inductor in series. Real-world acoustic response and what's falling out of the simulation could be miles apart.

However, it seems to translate into something which sounds good - and is a vast improvement over the unmodified one (without really sounding different; it's still a Ditton 44.)

If I can drag myself away from playing music (difficult!), I think I'll modify the other 44 and see what this is like in stereo.

Regards, Kat
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Old 10th Sep 2010, 10:08 pm   #42
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hi Kat,Ive used the free software download at http://www.toaelectronics.com/speaker-software.asp I found it easy to use.
Andy.
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Old 11th Sep 2010, 11:50 pm   #43
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

tried the link does not ! work
regards
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Old 13th Sep 2010, 10:12 pm   #44
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hi,
(About the above link; the site doesn't appear to support direct links, but the software can be found by going up to the top level then 'drilling back down'. It appears to be Windows-only; I might see if it works under WINE. But as I doubt it features accurate models of Celestion or SEAS drivers, it's probably no better than the LTSpice simulation I'm using at present. LTSpice does work under WINE; the developer makes sure it does.)
Meanwhile, back in the laboratory... (OK; the living-room...)
The final incarnation of the tweeter-matching circuit (10Ω in parallel with the tweeter, 1.1Ω between it and the original crossover) seemed to result in good tweeter/mid integration, so I figured it was time to modify the other speaker, put them back in their correct positions and properly assess them as a stereo system.

(Why 1.1Ω and not 1Ω? I have some of each but can think of more other uses for 1Ω w/w resistors than 1.1Ω. It made no audible difference, 1Ω works just as well.)
Fitting the SEAS tweeter
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I'd previously made a template for the tweeter cut-out which fit the original recess, so it was easy to mark-out the second speaker. The hole needs slightly enlarging, with an additional cut-out to clear the terminals on the SEAS tweeter. Once marked, I made the necessary adjustments with flat and half-round wood rasps, then drilled the three mounting holes.

I've positioned the terminals at the top, this places the new mounting holes away from the original holes, otherwise the new T-nuts interfere with the originals (which I wanted to leave in place.)

As the flange of the SEAS tweeter is slightly smaller, this would leave a ring of bare chipboard visible, so I masked it and painted it with Humbrol matt black enamel.
Crossover repairs/modifications
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Testing all the components of this crossover revealed one of the green 1.5µF Erie capacitors making up the 4µF section of the tweeter filter was o/c. So I made up a replacement using four 1µF Russian NOS PETP capacitors which I had available. These are attached to a bit of tagstrip, wired in, zip-tied down then attacked with the glue-gun for good measure.

The two 72µF capacitors in the bass section were fine, but of the four replacements I'd purchased earlier, three measured around 66µF and one was 70µF. As I wanted both speakers fairly well matched, I've used one original capacitor and one new one in each speaker.

Everything was then attacked with the hot-melt glue-gun just to make sure it all remains in place. Some of the music we listen to could be described as 'bass-heavy' and I didn't want bits dropping off!

The 1.1Ω and 10Ω resistors were attached to another bit of tagstrip, a temporary measure as I wasn't sure this would be the final arrangement. This is currently attached using one of the crossover mounting nuts and probably will fall to bits if I leave it like that.

Next, I swapped some bits around, replacing the 4µF capacitor on the other speaker's (still outboard) crossover with four of the same 1µF capacitors already used, and replaced one of the new 72µF capacitors (~66µF measured) with a tested-good old one.
So... what's it sound like, then?
Once back in position on their stands and connected up, the sound was much better balanced. Repairing the bass filter section has made a dramatic difference to the bass compared to before blowing a tweeter. There's around another octave of it and it's better controlled. Previously, it'd be 'boomy' in some parts of the room and lacking elsewhere. Now it's all there, doesn't dominate and just sounds 'right'.

The biggest difference, though, is in the overall impression of clarity, detail and "naturalness". Much more musical detail can be made out, it's very easy to pick out any instrument and follow it (even those which are low in the mix.) Vocals sound very natural and convincing.

Imaging is much better, too. Probably as both speakers are a closer match than they were with duff capacitors in each crossover (and tweeters which were failing before I set fire to one of them...)

They pass one of my 'system quality tests' now. The system upstairs (Acoustic Research AR-6) sounds good outside the room (well, anywhere else in the house.) The system downstairs never did. It does now.

I think the surprise is how they also still sound the same; I was preparing myself for the possibility of having to get used to what might've ended up as completely new speakers.

But they're still Ditton 44s, just better. Maybe they sound how they did when they were new, maybe they sound better still? I suspect the latter, tweeter design/manufacture has come on a bit in thirty-odd years.

After I'd got them both sorted out and back in position, it was getting late. We decided to listen to a few tunes before going to bed. This turned into a caffeine-fuelled listening session lasting over 18 hours...

I just need to tidy up the crossovers (and put 1/3 of one of them back inside the cabinet), then I'm going to say this is finished (then get back to the EMT turntable.)

I'm now rather glad I fried a tweeter then chose not to pay a ridiculous price for what could easily be an unmatched "pair" of probably knackered thirty-odd year-old HF2000 tweeters. I have a much better pair of speakers than before

I don't consider myself to be an "audiophile"; I listen to music, not the system reproducing it. This system sounds like music, not hi-fi...
Cheers, Kat

Last edited by Kat Manton; 13th Sep 2010 at 10:23 pm. Reason: Formatting, typos
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Old 14th Sep 2010, 7:48 am   #45
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Thanks for the comprehensive write up Kat. Now that you have done all the hard work I'll try the same with my 66's. These have been in my store for 3 years now waiting for suitable tweeter replacements.

Happy listening,

Bob W
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Old 15th Sep 2010, 8:58 am   #46
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hi Bob,

I left out quite a lot; it's taken something like two weeks of almost full-time work and three all-nighters. But this is my idea of fun

I'd be inclined to consider this 'experimental' at the moment, until yourself and others have tried it. I'd suggest doing what I did; fit one tweeter but bring the wiring for it out through one of the original mounting holes. Remove the original crossover components and build them (with the attenuation/matching network) on a bit of tagstrip or something.

I had this arrangement connected to the tweeter via a 'choc-block' and the amp via a length of speaker cable with 4mm plugs on it connected to the terminals on the back. (I have the amp connected via wires wrapped around the terminals, this leaves the 4mm sockets free.) It makes it much easier to tweak things if needed.

If you find the tweeter level seems a bit high/low to you, having it wired like this means you can run the bass/mid drivers via their crossovers from one amplifier channel and the tweeter via its crossover from another amplifier channel (with both channels fed from the same mono signal.) Adjust as needed, then it should be easy enough to tweak the resistor values a bit.

But... I've been listening to more music and I've never heard them sound so good. I got my first pair in 1991 (somewhat scruffy early black baffle ones.) I sold those in 2002 and bought... another pair of Ditton 44. They've always been my main speakers, I listen to music a lot; I guess I could claim to be a bit familiar with the things.

What'll be interesting is the friend I sold my first pair to (she still has them; they're her main speakers) is going to pop round to find out what I've been up to. I'd like to know what she thinks (and if I end up having to do the same thing to another pair...)

Something I omitted previously is a photo of the SEAS tweeter after fitting it. Painting the recess matt black seems to have worked, the end result is quite tidy (something I hoped to achieve as the grilles live in a corner, not on the speakers.)

Cheers, Kat
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Old 26th Nov 2010, 5:20 pm   #47
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hi. This is my first post so hello to everybody. Just a quick question. The 10R resistor goes across the tweeter after the capacitors with the 1.1R resistor between the 6.0uF cap and tweeter negative?

Thanks
Chris

Last edited by Station X; 26th Nov 2010 at 5:48 pm. Reason: FSK and GI.
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Old 26th Nov 2010, 10:22 pm   #48
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Possibly correct, but just to make it clear, I've quickly knocked up the attached diagram. Words can be misinterpreted...
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Old 27th Nov 2010, 5:47 pm   #49
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Totally off the wall and too late I suspect, but as I believe Celestion still have a custom service, I wonder if they could be persuaded to make up a small batch of HF2000 tweeters, either complete or just the diaphragm assemblies, as there are a good few out there in need of refurbishment. Sadly, the site of the old works in Ipswich is now a housing estate, but I believe a custom service still exists for the pro market..

When new, Ditton 44's were usually plonked on the floor. lifting them up a good few inches (12" off the floor?) transforms them...
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Old 23rd Dec 2010, 4:44 pm   #50
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Thumbs up Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hello Kat,

I have applied the 19TFF using your "zobel" configuration to my small and ever popular Ditton 15XR models.

The application here worked great, and the components used were nowhere near the specification of yours. The typical story can be said for what happened to the HF2000's in these, and these quickly got replaced with some Audax TW025A0, making them full range again, and interestingly bright for "advanced" music, but missed that warmth, and more biased natural sounds that is produced from a piano, not that these were ever going to compare to the 44 and 66 range I know!

I loved reading this thread, and that was before joining, as I really just needed / wanted a solution to make them sound original, and ever fetching more money on a well known auction site, I was prepared to pay a certain price, but knowing the HF2000's record for reliability, and the age they are now, this was debatable, until reading here!

I had not the time to devote to this, or the equiptment to measure responses, and to say the least, I do not have the best amplifier in the world, I enjoy listening to music like yourself, decided to apply your solution!

Costs

£16.20 * 2 Tweeter 19TFF1
£8.00 Black sealant (they have had many tweeters in and most of the baffle around the magnet was cut away).
The resistors, only cheap ones, a 7W 1R, and 3*3W 27R

Two hours each speaker on differnt nights, and once the second speaker was completed, your caffine compared to a couple of beers, and they do sound pretty nice, picking out sounds and following them, and also discrete audio standing out, especially on seperation!

Bottom line, a big thank you, and if I get time, I will see about posting some pictures up! My next move should be replacing the "Elcap" capacitors

Many thanks

Pete'.
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Old 24th Dec 2010, 10:51 am   #51
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hi again, with the parts finally arrived a few days ago I plunged straight into doing this but I have ran into a problem that the speakers just don't sound the same after the mods they sound very closed in and the imaging and detail is very poor. I should point out that I also fully recapped the crossovers in both speakers as measurements on nearly all caps showed they had seen better days.

I have however forgotten which way the big piece of foam goes back into the cabinet as regards to the brace inside, does it go below or above this? Also the cut outs in the baffle for the tweeters have been greatly enlarged by the previous owner and it is not sealed, also I think the seals around the other drivers are gone as well.

Any suggestions would be greatly appreciated.

thanks
chris
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Old 25th Dec 2010, 2:22 am   #52
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hi Chris,
Quote:
Originally Posted by reddish75 View Post
the speakers just don't sound the same after the mods they sound very closed in and the imaging and detail is very poor.
This suggests the phasing of one or more drivers (or one loudspeaker) is incorrect.

Check all connections and trace all wiring ensuring it matches the posted schematics. The black terminal on the rear panel should connect to the '-' terminal on bass and mid drivers and the '+' terminal on the tweeters.

If you're unsure of the connections on any driver, connect a 1.5V cell to the driver. The dome or cone will move forward when the cell's +ve terminal is connected to the '+' terminal of the driver. (This is perfectly safe as long as you use 1.5V.)

Quote:
Originally Posted by reddish75 View Post
I have however forgotten which way the big piece of foam goes back into the cabinet
The thick oblong bit goes over the crossover panel, directly behind the bass driver. The other (thinner) big bit goes in a 'U' shape across the bottom of the cabinet and part-way up each side (held in position by the bit over the crossover panel.)

HTH, regards, Kat.
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Old 22nd Jan 2011, 6:44 pm   #53
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Hello Kat,

Congratulations on an excellent summary of a very interesting project!

I came across this thread while bumbling around the internet looking for information on possible replacements for rather dodgy sounding HF2000 tweeters in both my Ditton 44s (2 sets) and 25s. Strangely enough they all seem to have different problems but the main issue, when compared to the best (?) performing unit is a rather dramatic drop-off in output over 4Khz.

New Seas tweeters are on order along with various other components to match the new tweeters and to resurrect the crossover units so I am looking forward to seeing the difference. As you can guess at this stage my objective is good sound quality rather than outright originality!

Also resurrecting and re-working my home-built (1986!) Williamson Ultra-Linear with some updated components (some of the old electrolytics are looking a bit the worse for wear) so hopefully the combination will work well - the neighbours will probably be able to verify this......

Many thanks again for all the effort and a well thought out and planned project!

Cheers, Paul
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Old 1st Feb 2011, 2:25 pm   #54
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Kat.

Deservedly a lot of praise here, job well done. You guys know your stuff. I have some of these 44s and am considering purchasing some PMC 2TBs passive. I have already found some flying mole amps, got three for £450 i was chuffed at that. I can hardly afford them but the listening and collecting of music has been going on for sometime, now like all my years.

Do you think a novice who's willing to learn could attempt this tweeter and crossover mod, learning on the job? Also how you do measure crossover freq? With software and a microphone I suppose?

Regards Dan.

Last edited by Station X; 1st Feb 2011 at 3:03 pm. Reason: FSK, GI.
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Old 1st Feb 2011, 5:40 pm   #55
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

I have an old pair of Celestion Ditton 15xrs on my jukebox, and they sound much better than I imagined they would, I think mine are from the early 70s.
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Old 8th Feb 2011, 12:23 am   #56
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Talk about late to the party! I also have a pair of 44's with pooched HF 2000tweeters. Surfing thru the web (and this site in particular) tells me that even if I find a used pair they are not worth buying. The SEAS 19TFF1 HO737 seems to be an excellent replacement as per Kat's stupendous efforts and resulting satisfaction with the sound. I'm in Calgary, Canada and the SEAS supplier here only has a 20TFF H830 tweeter. The specs are almost identical, the differences being:

Recommended Frequency Range:
4000-20000 Hz (19TFF) vs. 2500-25000 (20TFF)

Short and Long Term Handling Power:
220W-90W (19TFF) vs. 200W-80W (20TFF)

Characteristic Sensitivity:
2.83V, 1m - 88db (19TFF) vs. 1W, 1m -89db (20TFF)

Free Air Resonance:
1700 Hz (19TFF) vs. 1500Hz (20TFF)

Moving Mass:
0.23 gm (19TFF) vs. 0.22 gm (20TFF)

All of these specifications are greek to me! Do these differences alone or together make a substantial difference in the sound and characteristics that I want (being those described by Kat after successfully installing the SEAS 19TFF's)?

Many thanks for any comments!
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Old 27th Mar 2011, 12:25 pm   #57
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

Kat, Thank you for providing EXACTLY the info I needed. I am the new owner of a pair of Ditton 44 fix-up-projects, bought for AU$40 with a blown left tweeter and right midrange. The sound produced with this configuration was promising to say the least.

I am new to "Hi-Fi" and will definitely replace my 5.1 amp with something fitting the Celestions.

My 44's are laminated baffle type, but the crossover boards are much more modern looking, with a press-on connector for all in & out wires.

Here's some pics and info to add to the thread.
1. Crossover board in situ
2. Under side
3. Top
4. Two boards, different printing and board material. Everything else has same values
5. HF2000 has fragile construction, the blown one has glue lifting and is open circuit.

More info and questions to follow.

Has anyone else had success with the tweeter upgrade? Any comments or recommendations?
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Old 27th Mar 2011, 1:04 pm   #58
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

ORIGINAL Component list in my Ditton 44 crossovers

Crossover board part number SP2271 ISS. 1

C1 ERIE 4.7uF 160
C2 ERIE 1.5uF 160
C3 ERIE 3.3uF 160
C4 .68 160 (smaller, not labled ERIE)

C5 ELCAP / 6 MFD / 50 V L.L. / 93-7734 (93-7723 on second board)
C6 ELCAP / 72 MFD / 50 V / 93-7723 / SP 2279
C7 ELCAP / 24 MFD / 50 V L.L. / 93-7734 / SP 2191
C8 ELCAP / 72 MFD / 50 V / 93-7734 / SP 2279

L1 RED PLASTIC VERTICAL / 1163
L2 GREEN FERRITE HORIZ / 1162
L3 RED PLASTIC VERTICAL / 873
L4 RED FERRITE HORIZ / 1161
L5 GREEN FERRITE HORIZ / 1162
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Old 1st Apr 2011, 12:03 pm   #59
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

New midrange arrived and is installed. I'm not really happy with the sound (admittedly there is still one blown tweeter).

Tested with Smog, Grant Lee Buffalo and Jeff Buckley on CD through PS3, Optical Digital into Kenwood KRF-V7050D amp. Sounds pretty good, good stereo image. The tweeters are crossed over really high, you can hear it - sounds only slightly off centre.

When I put some heavier rock (mp3) on it starts to fall apart. It may be that I have some low-bitrate mp3s. Gillian Welch sounds fairly good, but I almost want to go back to my original homemade 3ways.

Next: get the crossover caps checked by someone who knows what they're doing and replace the HF2000 tweeters.
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Old 1st Apr 2011, 12:57 pm   #60
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Default Re: Celestion Ditton 44 - HF 2000 tweeter replacement?

I'm thinking Vifa D25 because they are available (but are they made in China?) and match impedance with a resistor, tune with an attenuator. Any comments? This is a dead thread isn't it?
I'll keep posting developments.
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