Restomod Celestion Ditton 44/15XR/UL8.

[DarrenHW]

For the last few months buying Celestions has become a bit of a compulsion for me, this is almost my entire collection:

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That’s 2 Pair 15XR, 1 Pair UL8 (this is also the speaker mounted above the TV) and 2 Pair 44’s (the second pair aren’t shown as they’re setup as the rear speakers).

My intention is to use 5 speakers connected to an AV amp and swap speaker cables to the front for stereo listening. I am currently running this configuration:
Front / Stereo – Ditton 44.
Centre – UL8.
Rear – Ditton 44.

I started with a 15XR as the centre but swapped for the UL8 (which are 4-8ohm like the 44’s) as this is a far better combination.

Now I have an ensemble of speakers that work for AV I will be turning my attention to restoring them. I chose the title for this thread in homage of Ken’s (Qwin) 66 thread on which I am a somewhat habitual thread drifter (AKA: PITA). Unlike Ken I am unlikely to come up with interesting and valid principles, tips and information based on research, knowledge and experimentation but most likely school boy errors, questions and assumptions due to inaccurate research based on a lack of knowledge and ill judged promiscuity. In all honesty I’m starting this thread so that I can ask for help, advice and to generally tap into other members experience during this project. Celestions are pretty popular on here, so hopefully this thread will meander its way to something that may be useful for other Celestion owners and an alternative to the info offered on DIYAudio.

The restoration will be approached in the following order:
Service / modify the crossovers and rewire.
Experiment with the SEAS 19TFF1.
Build new speaker cabinets and experiment with dampening.

[DarrenHW]

I have already partially recapped a pair of 44’s following the thread on DIYAudio. Initially I was happy with the recapping but this comes with the caveat that I have never heard a stock pair of 44’s in good form. The first pair had issues with an imbalance on the Mid’s from left to right, when I removed the crossover this is what I found:

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the second pair have mismatched crossovers and significant damage to the cabinets.

After a bit of searching around I stumbled across the DIYAudio thread which is a spinoff of the 66 thread which covers recapping the crossovers with polypropylene capacitors. I read through the thread and ordered the caps and resistors to recap the tweeter and mid sections of the crossover:

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I was a happy boy, the Mid imbalance was resolved and the speakers sounded cleaner and more detailed. I did start to notice resonance issues (similar to those Ken experienced) occasionally when connected to the AV amp, this wasn’t an issue I’d notice when connected to the stereo amp so I put it down to the AV amp which I plan on changing, so wasn’t particularly concerned. However after completing the servicing of a Quad 405 and hooking it up to a recently acquired pre amp it started to become obvious that the speakers didn’t sound right and after talking with Ken it seemed we were both experiencing issues with similar material.

What I’m going to do now is follow Ken’s work on the 66 crossover (http://theartofsound.net/forum/showthread.php?31916-Renovation-of-Celestion-66-Studio-Monitors/page19) and replace the mid caps with new electrolytic’s.

The 44 crossover is very similar to the 66:

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The above schematic shows the value of C7 being 24uF however, from my own speakers and many featured on DIYAudio it would seem that this value varied when the speakers actually left the factory and can be 24uF or 30uF. The first pair of 44’s I recapped with 27uF, the pair I now intend on recapping are 30uF made up of 2 x 12uF and 1 x 6uF.

In order to retain this value using the LL Alcap’s Ken recommends and will need to replace these with 3 x 10uF Alcap’s.

[DarrenHW]

Celestion UL8.

A bit of an elusive speaker, I can find out very little about it.

1329113292

When I originally bid on these I thought they were essentially a 15XR in a different cabinet and would be useful for spares. However, after I collected them I stripped them down to perform a visual inspection and take measurements from the tweeter and mid/bass, I discovered the HD1000 and PL8 are 4ohm not 8ohm like the 15XR’s and the crossover has a lot more going on.

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The 16 + 12 MFD are for the tweeter and the 20 MFD is for the mid/bass.

Celestion 15XR.

These are unlikely to be used in the AV system, as much as I’d like to use them in the Kitchen I cannot accommodate them so will most likely be destined for the Shed / Gym. These are the simplest of the 3 Celestions I have to recap as they only contain 1 x 4.7uF 50v LL Elcap.

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Can anyone tell me why there is such a difference between the 15XR and the UL8 crossovers the board layout seems to be the same apart from the extra caps? I understand (sort of) that the inductors need to have different resistance but why the need for the additional caps in the UL8?

[ff1d1l]

Who is/are Resto? And what do their mods consist of?

[Ali Tait]

http://www.restomodsinreno.com/index.php/what-is-a-restomod

[DarrenHW]

http://www.restomodsinreno.com/index.php/what-is-a-restomod

Good explanation, I think it's a good term for what goes on here with vintage equipment. I did wonder whether "Bastardisation of Celestsion ..." would be a more appropriate title, just have to see how they turn out? :)

All caps now ordered, hopefully some progress next weekend.

[The Barbarian]

Nice Darren just do not fart about with the crossover design like a lot have the impulse to do. Angers me why they seem to think that the company who made the speaker in the first place did not know what they were doing.. Swap out Caps & Resistor like for like values & just enjoy. If you don't like how the original design sounds move em on.

[walpurgis]

Nice Darren just do not fart about with the crossover design like a lot have the impulse to do. Angers me why they seem to think that the company who made the speaker in the first place did not know what they were doing.. Swap out Caps & Resistor like for like values & just enjoy. If you don't like how the original design sounds move em on.

I tend to agree. The manufacturers were not stupid, they spent an awful lot of time in their design development and are likely to have got it right. I never change crossover components just for the sake of it. If the speaker sounds right, then it probably is. Of course suspect caps should be replaced, but only if necessary. The main job on old speakers is to update the terminals to accept modern cables and possibly install better quality internal wiring.

[DarrenHW]

Nice Darren just do not fart about with the crossover design like a lot have the impulse to do. Angers me why they seem to think that the company who made the speaker in the first place did not know what they were doing.. Swap out Caps & Resistor like for like values & just enjoy. If you don't like how the original design sounds move em on.

It seems I am already guilty of this by attempting to "improve" the crossover by replacing the Electrolytic's with Poly Props following the thread on DIYAudio. I have now ordered Electrolytic's to replace Electrolytic's (type for type) and looking forward to hearing how the two compare. I like the way the recapped pair sound (apart from their issues), I started buying Celestion's after hearing Marco's 66's, if the 44's come close to the 66 sound I'll be happy. The only area I think I can improve on the original design (although how significantly remain to be heard) is with the cabinets which I'll build from 25mm Baltic Birch Ply, again like the recap another job born out of necessity, but one I'm looking forward to, I've spent so much of my free time with the soldering iron lately I'm missing my router.


I tend to agree. The manufacturers were not stupid, they spent an awful lot of time in their design development and are likely to have got it right. I never change crossover components just for the sake of it. If the speaker sounds right, then it probably is. Of course suspect caps should be replaced, but only if necessary. The main job on old speakers is to update the terminals to accept modern cables and possibly install better quality internal wiring.

I (with hindsight) agree, I really wish I'd heard a pair of stock 44's before deciding to shop at the bottom of the market for restoration projects. Terminals and wiring will be addressed once the crossovers have been finalised, the dilema I have here is whether to replace the internal wiring with the same cable I'll be using as speaker cable or use something specifically for internal wiring?

[The Barbarian]

Darren im not on about changing to a different type of cap, god no i use Polyprops all the time {But swear by one type}, im refering to altering values & such. a cap value is a cap value regardless of the manufacturer.

[DarrenHW]

Sorry Andr'e I misunderstood. No, I won't change any values... again :o. I did rework the UL8 cross over, removing all the caps, installing a bridge and the 4.7uF LL that's in the 15XR, I thought having fewer caps in the cross over could be beneficial, especially as the mid/bass in the 15XR has no cap. I was wrong, this actually seemed to muddy the sound from the UL8, just goes to prove what you said earlier:


... Angers me why they seem to think that the company who made the speaker in the first place did not know what they were doing..

:spank:

[Reffc]

Celestion UL8.

A bit of an elusive speaker, I can find out very little about it.

1329113292

When I originally bid on these I thought they were essentially a 15XR in a different cabinet and would be useful for spares. However, after I collected them I stripped them down to perform a visual inspection and take measurements from the tweeter and mid/bass, I discovered the HD1000 and PL8 are 4ohm not 8ohm like the 15XR’s and the crossover has a lot more going on.

13293

The 16 + 12 MFD are for the tweeter and the 20 MFD is for the mid/bass.

Celestion 15XR.

These are unlikely to be used in the AV system, as much as I’d like to use them in the Kitchen I cannot accommodate them so will most likely be destined for the Shed / Gym. These are the simplest of the 3 Celestions I have to recap as they only contain 1 x 4.7uF 50v LL Elcap.

13295

Can anyone tell me why there is such a difference between the 15XR and the UL8 crossovers the board layout seems to be the same apart from the extra caps? I understand (sort of) that the inductors need to have different resistance but why the need for the additional caps in the UL8?

By the looks of it, they needed to steepen the acoustic roll-off of the bass driver, so whilst the 15 uses 1st order LF, the UL8 appears to use 2nd order. Given that the cabs are different, then this might explain the need to treat the woofer slopes differently. Polarity on the tweeter should be reversed if this is the case (easy to check). There is no need per se to have any different DCR for the bass inductor...the lower the better in fact since it's in the signal path and affects damping factor and speaker sensitivity.

[DarrenHW]

Hi Paul, thanks for the info. The polarity of the tweeter is indeed reversed (and is something I should have looked at before blindly reworking the crossover :doh:) and as I'm sure is clear from my previous posts I didn't even consider the effect the cabinet would have (and now after a quick google of your post), whether the frequency response of 4 and 8 ohm HD1000 / PL8 are the same or whether the "experiment" would cause phasing errors...

In my first post I wrote this:


Unlike Ken I am unlikely to come up with interesting and valid principles, tips and information based on research, knowledge and experimentation but most likely school boy errors, questions and assumptions due to inaccurate research based on a lack of knowledge and ill judged promiscuity.

Only a few posts in and I think I've covered school boy errors, questions and assumptions, highlighted my lack of knowledge, demonstrated ill judged promiscuity and in all likelihood due to my rush to reply will have covered inaccurate research in this post.

[Reffc]

Hi Paul, thanks for the info. The polarity of the tweeter is indeed reversed (and is something I should have looked at before blindly reworking the crossover :doh:) and as I'm sure is clear from my previous posts I didn't even consider the effect the cabinet would have (and now after a quick google of your post), whether the frequency response of 4 and 8 ohm HD1000 / PL8 are the same or whether the "experiment" would cause phasing errors...

In my first post I wrote this:



Only a few posts in and I think I've covered school boy errors, questions and assumptions, highlighted my lack of knowledge, demonstrated ill judged promiscuity and in all likelihood due to my rush to reply will have covered inaccurate research in this post.

LoL!

You've actually done something very valid Darren which is to realise those errors and learn...so not at all wasted effort on your part. Well done for having a go is what I'd say.

[DarrenHW]

Thanks Paul, that's the way I like to look at it too. I expect to make many error's along the way but see it as part of the learning curve and I'm determined to get a working knowledge of my system, it just might take a while.