View Full Version : Ditton 66 for dummies ...
Hi - I've had a warm welcome in the intro forum. This feels like a friendly place - thanks to all the respondants so far.
As I mentioned there - I think every piece of audio equipment I own comes under the 'past masters' remit. I haven't upgraded or introduced anything new since 1989.
I've spent the intervening years just enjoying the sound it made. The problem I've come across though follows a 2 year layup of the equipment due to
"decorating" reasons. Now that I've reininstated everything to where it belongs I've noticed the sound to be flat, uninvolving and right speaker biased - not as I remember it once was. I know that there
may be an element of rose tinted spectacles going on but I really don't think so.
The setup is:
Audiolab 8000A amp
Systemdek turntable with Linn arm / AT cartridge
Nakamichi RC202 tape (I have a large tape collection ..)
Sony CDP228esd CD.
Celestion ditton 66.
I made the decision (largely due to the vastly impressive sticky thread in this forum) that I need to give my Dittons some TLC. They're looking a bit sad & secondhand and I suspect that they are the source of the
problems above. The drive units seem to be mostly ok but I've noticed that the metal dome on one of the tweeters is beginning to come a little lose, the mids seemed fine until I tried a tone test cd & at about 100 hz & above there's an unpleasant almost mechanical sound on the right mid. The bass units both appear fine. My suspicion is falling on the crossovers.
The left side crossover has some different capacitors to the right. I'm sure Celestion didn't release them like that - the person I bought them from in 1989 worked for celestion so I would hope that they would be kosher but
I'm wondering if the crossovers in general might be a bit tired now & letting the side down?
If there are any 66 owners out there willing to help an amateur out I'd gladly trade knowledge for beer tokens ...
Thanks - sorry it's a long post,
John
walpurgis
15-08-2014, 10:40
Hi John.
The HF2000 tweeter phase plate (perforated metal cover dome) is well known for coming loose. It's just held on by thin double sided tape and can be refixed easily. Care should be taken in it's removal though. I'd suggest doing both as the adhesive on the 'good' one will be suspect too.
The odd sounding midrange unit may not be defective. It could well be a capacitor in the crossover failing. I'd suggest taking both mid units out and measuring the DC resistance at the connections. It should be around 6 ohms I believe. If that's OK test them using a capacitor in series, 8Mfd should do and listen at moderate volume on a music signal for output, they should sound similar. Check all crossover capacitor values. Most on AOS will likely tell you to upgrade them for modern equivalents. I'm sure somebody here can show you a crossover circuit or you can find one online.
Here goes, just found this. It may help:
http://i57.tinypic.com/30wbcl5.jpg
I'd be inclined to remake all soldered joints too, including at the terminals, which may benefit from replacing. You may want to upgrade the internal wiring quality too.
DarrenHW
15-08-2014, 11:53
the mids seemed fine until I tried a tone test cd & at about 100 hz & above there's an unpleasant almost mechanical sound on the right mid. The bass units both appear fine. My suspicion is falling on the crossovers.
Hi John, I have Ditton 44's not 66's and I'm only in the early stages of restoring / modding them and I'm by no stretch of the imagination an expert, but I suggest simply rotating the drivers 180 degrees as the first place to start if you have not already done so. On the first pair of 44's I picked up I had a issue which sounds similar to yours which was caused by sagging in the rubber, I rotated it and problem solved, I have since treated the surrounds with a rubber restorer in an attempt to keep them in good shape.
The left side crossover has some different capacitors to the right. I'm sure Celestion didn't release them like that - the person I bought them from in 1989 worked for celestion so I would hope that they would be kosher but
I'm wondering if the crossovers in general might be a bit tired now & letting the side down?
The second pair of 44's I picked up have miss matched (yet what appear to be original) capacitors, so maybe some pairs left the factory this way?
Ken (Qwin) is the man to offer the best advice, is it his thread you referred to in your earlier post (http://theartofsound.net/forum/showthread.php?31916-Renovation-of-Celestion-66-Studio-Monitors&highlight=ditton)?
Thanks for the advice - I'll check the things you mention.
Does the fact that mine is one with the printed circuit board make any difference to the values on the diagram please?
A problem I forgot to mention, which may be diagnostic I don't know, is that occasionally the left speaker goes 'dead' with no output at all. If I put the balance completely over to that side & turn the wick up on the amp for a second it springs into life suddenly (and quite loudly). It will stay good for some time after that. My suspicions were that there is a bad connection (possibly the terminals you mention).
It does surprise me that we go to the expense of running decent cable throughout the signal path to suddenly hit what looks a lot like half a strand of bell wire inside the cabinet. Was that a deliberate design feature or a cost saving exercise?
John
The 66 is from before fancy speaker cable was invented.
walpurgis
15-08-2014, 15:22
Rotating the 66 midrange driver is unlikely to cure anything. It has a relatively low compliance suspension, and the old rotation dodge is most likely to work on units that have soft high compliance surrounds that have sagged, more usually bass units.
The cutting out and then coming back on under power is typical of dirty contact areas, perhaps new plugs & sockets may help, it could also be a 'dry' soldered joint. I doubt the use of a PCB has any influence on what you are hearing.
Rigster - The circuit posted is for the early tag board x-overs and has slightly different values for two caps.
Find the later diagram linked on my thread.
Nipping out to hear some live blue's, will give a better answer tomorrow.
Good point Martin - I hadn't considered that.
Sorry Geoff. I didn't mean the effect on the audio of the PCB. I meant does the fact that it is the PCB board mean that the components are different?
Thanks,
John
walpurgis
15-08-2014, 19:44
Good point Martin - I hadn't considered that.
Sorry Geoff. I didn't mean the effect on the audio of the PCB. I meant does the fact that it is the PCB board mean that the components are different?
Thanks,
John
Ken seems to have answered that. Somebody here may have a Ditton 66 PCB crossover diagram showing values. Yours should be marked though.
Geoff/ Ken - I found the PCB Xover diagram having re-read the thread more thoroughly. Thanks. It looks daunting.
The Xover pictured (PCB) is almost exactly the same as the ones I have but it seems to me that one of the caps on the board I thought was completely original might not be original either.
It's starting to look a bit messy.
Can I ask if anyone has sucessfully restored the thin laminate finish on the top of these speakers? One of mine (in its past I hasten to add) was used extensively as a coffee table and the surface is deeply marked and an edge chipped
to the point where the fibre/ particle board beneath is exposed. I did ask a cabinet repairer for a quote but at £200 per speaker I thought I'd learn to love the defects ...
Thanks all
John
I don't know much about this sort of thing but re the cosmetic issues you could consider wrapping the speakers in carbon fibre like you can get for cars. Would hide the veneer problems and make the speakers look very modern and up to date. But that might cost more than a re-veneer, I don't really know. If you could do it for say £50 a cab that would be worth considering. It would look good done properly. Anyways just a thought.
walpurgis
16-08-2014, 09:35
If you just have a couple of chips in the veneer, use my trick. Have a look round a boot sale or the charity shops for a cheap item having similar veneer and take some off that to cut and let into the damaged areas (cut and trimmed with a craft knife). Use a good contact adhesive. Any small gaps can be filled with colour matched filler. Once the whole panel is rubbed down with fine sandpaper and repolished with 'white polish' then waxed you'd be hard put to see any faults.
Don't be put off changing caps. Just check that what you intend to use is suitable and of good quality. There are dedicated 'speaker' type caps available (of varying quality).
Here are both cicuit diagrams from my thread, I believe they are also in "the Knowledge".
http://www.jkwynn.co.uk/Project_Images/66/66_15.pdf
;)
I don't know much about this sort of thing but re the cosmetic issues you could consider wrapping the speakers in carbon fibre like you can get for cars. Would hide the veneer problems and make the speakers look very modern and up to date. But that might cost more than a re-veneer, I don't really know. If you could do it for say £50 a cab that would be worth considering. It would look good done properly. Anyways just a thought.
Carbon fibre vinyl. (http://www.ebay.co.uk/itm/3D-Carbon-Fibre-Vinyl-Wrap-Air-Bubble-Free-Black-Multi-sizes-/200974170606?pt=UK_Wallpaper&var=&hash=item2ecafe79ee)
https://www.youtube.com/watch?v=PT9IzhEkSaY
Also: http://www.ebay.co.uk/itm/Single-Layer-Real-Carbon-Fibre-Fiber-Sheet-Wet-Lay-1mm-2sqm-/251158592413?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3a7a37fb9d but probably harder to work with.
Thanks for the help and the links for the fabric. If possible I'd like to keep the veneer look if I could but it may be Hobson's choice if I can't work with it. Ultimately I'd rather spend money making them sound good rather than cosmetics so I may have no option.
I need to strip them down and measure the resistances of the drives, rewire & replace the terminals & build up courage for the xover.
Ken - how did you attach the wire from the xover to the terminals you chose please? Is it captured by the locking nuts or did you solder the wire to them? I want to replace the terminals as they're pretty shot at & I'd rather follow a known good path - I'm going to follow your choice on the internal wiring. It seems that you rated it.
Thanks again
John
Right decision Jon, though you could go for gold, LOL:)
https://www.youtube.com/watch?v=bcLV5wA8XGY
walpurgis
16-08-2014, 19:12
Oh, so tasteful. Tacky looking joke mobile! :rolleyes:
I'm not sure that's the exact look I'm going for but I take our point ...
Probably the first thing I'll try is v fine grade sandpaper & try to take down the marks in the veneer (they're too large an area for the cutting and replacing Geoff. It would easier, if possible, to replace the veneer in total) and see where I go from there. If I make it worse then I might have a go at a vinyl covering as you suggest Martin - it's a good option.
Has anyone on here (or know of anyone) who has addressed veneer problems on these at home?
I'm more worried about lack of hours driving a soldering iron. I would say I'm in the area of "ok amateur". I do have a friend who is a whiz as it was his job for several years. I'll probably pay him in alcohol to do it.
Aplogies for all the questions. I'm keen not to mullah these speakers after so many years.
John
Having heard two pairs last weekend I can say that they are a very good speaker and well worth fully restoring. Really good midrange on them especially. If there was a modern equivalent I reckon it would retail at £7K or thereabouts.
I couldn't agree more Martin. One of the things I've noticed since firing them up again though is that they are extremely mid range heavy - almost as if the bass & treble have given up trying. That doesn't seem right as my predominant memory of listening to them in the past was the other way round.
They're that good when sorted? Really? That surprises me & makes me more nervous ...
walpurgis
16-08-2014, 20:39
Well that's not right. I've not heard a pair for a long time, but my recollection is of a powerful, detailed, but even and smooth sound.
Here are both cicuit diagrams from my thread, I believe they are also in "the Knowledge".
http://www.jkwynn.co.uk/Project_Images/66/66_15.pdf
;)
They are now! Apologies for taking so long to add this information to the Scans. And thanks for making them available to us: surprisingly for such a popular speaker, your contribution is the first and only entry we have so far under "Celestion".
If anyone else has information on Celestion speakers that they can scan, they would be very welcome addition. Please post any such scans in "The Knowledge Café". Thanks
Regards
Barry (aka 'Fount Master')
"how did you attach the wire from the xover to the terminals you chose please? Is it captured by the locking nuts or did you solder the wire to them? I want to replace the terminals as they're pretty shot at & I'd rather follow a known good path - I'm going to follow your choice on the internal wiring. It seems that you rated it."
At the moment I have the original solder ring tags soldered on the leads from the x-over and these are held in place on the rear of the binding posts with brass nuts.
It is better to have them soldered and once I have finished tweeking then I will do this. Large binding posts and thick copper cables require a lot of heat to achieve a good solder joint so you have to make sure there is nothing that can melt including spacers and even the rear name plate that the posts sit on. If you slip the nut on the cable and then pull the cable through the hole and outside the cabinet, solder the wire to the post and push the post back in and slide the nut down the cable and tighten it on the back of the post.
The Black Rhodium wire is excelent, the thick silicone jacket is very flexible and insulates the wire from in-cabinate vibration and does not melt or shrink back when you solder it.
"Can I ask if anyone has sucessfully restored the thin laminate finish on the top of these speakers?"
Never had to do this but I would either remove the hole of the laminate from the top and apply new. Or fill the damaged area and apply new over the top. Both these methods have the same problem of matching the finish to the rest of the cabinet. Although the finish is described as Teak it is in fact something else which I can not remember. It is varnished and the varnish will have aged taking on a nice amber colour, this would have to be replicated by the use of stain or a tinted varnish. It would be very difficult to match a patch repair, both in wood type and varnish colour to blend in with the rest of the panel. It would be much easier to re veneer the whole panel and better still to do the whole cabinet (both). But I suspect that is not what you wanted to hear. A localised invisible repair is VERY dificult to achieve and will require a high skill level.
Rigster - I just read some of your earlier posts.
It's difficult to tell where sound is comming from when listening to the drivers. A 100Hz tone is unlikely to cause much distortion on the Mid driver as the cross over point is 500hz so that frequency will be mainly covered by the bass driver.
You think you have different makes of cap on the two boards, this would not be good.
Lack of bass - First thing I would do is renew your 72uf bass caps with Alcap 100v bi-polar Electrolytics from Falcon Acoustics they are cheap, will fit on the board and will revive the bass content - they did on mine - they wont adversely effect other parts of the circuit.
Can you photograph your boards and post the pics so we can see which caps have been changed in the past and what type/value they are?
Rigster - I just read some of your earlier posts.
It's difficult to tell where sound is comming from when listening to the drivers. A 100Hz tone is unlikely to cause much distortion on the Mid driver as the cross over point is 500hz so that frequency will be mainly covered by the bass driver.
You think you have different makes of cap on the two boards, this would not be good.
Lack of bass - First thing I would do is renew your 72uf bass caps with Alcap 100v bi-polar Electrolytics from Falcon Acoustics they are cheap, will fit on the board and will revive the bass content - they did on mine - they wont adversely effect other parts of the circuit.
Can you photograph your boards and post the pics so we can see which caps have been changed in the past and what type/value they are?
Out of spec electrolytic bass caps usually degrade by drying out and the ESR increases, often dramatically. Had this been the case with the series HF cap, then a significant drop off (not to mention shifting of crossover point) would occur. However, in the bass, these caps are generally shunted after the series inductor to increase the crossover slope, so adding impedance here has less effect on output, it just affects the slope. At worse, it means a 2nd order crossover for example (although electrically, the 66's use 4th order for the bass) could tend more towards first order. That in itself will not reduce lower bass output. Dry solder joints causing excessive impedance might, so first thing to check I would suggest is that electrical connections are all sound.
However, as Ken says, it's not ideal from a speaker matching perspective to use mixed capacitors unless their electrical parameters are the same (in which case, it matters not a jot for bass shunt duties as it wont affect timbre).
Thanks Ken / Reffc,
If I've done this correctly the xovers should be visible below. The first picture is the one I thought was completely original but I have my suspicions about C5 - it seems too modern?
The second picture is the one even I can see doesn't look original. I'm troubled that there are only 2 yellow caps instead of the 4 green ones to start with, never mind the C5 replacement.
Does this make any sense?
13020
13021
13022
John - The C5 blue electrolytic should be 4uf but looks physically too large, check it’s value. I would fit new electrolytics in this position on both boards, from Falcon.
The Green Pair of C1 at 4.7uf + C2 at 1.5uf = 6.2uf. The large Yellow cap should be this value.
The other Green Pair of C3 at 3.3uf + C4 at 0.68uf = 3.98uf (4uf) the smaller Yellow cap should be this value but appears to have 4.3 written on it.
I would replace these caps on both boards with Polyprops of your choice to the correct values. Either as parallel pairs or single caps depending on availability of the values. Use the same arrangement on both boards.
Then at least you will have the right values and same make caps on both boards.
dantheman91
18-08-2014, 20:01
Ken knows his onions..........:cool:
Thanks again Ken / Reffc
I'll take both boards out & swap the caps over. Is there an online seller of these caps that you would recommend from experience please?
It's good of you both to help.
John
Hi John
For the 4uf and 72uf bipolar electrolytics I would suggest using the 100v Alcan items sold by Falcon Acoustics : http://www.falconacoustics.co.uk/alcap-claritycap-solen-audio-capacitors/alcap-electrolytic-capacitors-high-power-100v/alcap-72-00uf-100v-dc-high-power-electrolytic-capacitor-nonpolarised-reversible-series.html
There is an option on these for Falcon to grade the caps which are nominally +/- 10% to 5% or 2%, it’s worth the extra 50 pence or so each, to have this done, for closer matching. This is what I have used.
For the Tweeter series caps of 6.2 and 4uf use any good Polyprop cap. I used Sonicap Gen 1 from the States, these take a couple of weeks to deliver and work out quite expensive with postage, VAT, Import duty and small order and cross border paypal surcharges. But they do produce items of the exact values: http://www.soniccraft.com/sonicaps.htm and are good for high frequency applications.
If you want something less expensive and from the UK, you could use ClarityCap SA range. They come in 6.2uf and 3.9uf which is close enough for the 4uf and is used by many people as 4uf is not a common value. These are stocked by HiFi collective which I have purchased from many times. http://www.hificollective.co.uk/components/claritycap_sa.html
If, while your at it, you wanted to renew the 24uf main series cap in the Mid Range then the Ansar Supersound (Polyprop) of 25uf would fit the bill: http://www.cricklewoodelectronics.com/Cricklewood/product.php?productid=2063&cat=155&page=1
Or, If ordering from Sonicraft, they also do a 24uf. Sonicraft are the only company I have come across producing all the exact values, while not being in the price realms of some of the more exotic capacitors, they are still a fair chunk of cash for the larger sizes after all the additional taxes etc are added.
Thank you Ken - that was exactly what I needed. I spent a fruitless few hours trying to find what was required but I really don't understand electronics too well.
I really want to do my speakers justice so I'm very grateful for the time you've spent helping. It's my birthday soon so I might be getting components as presents. Imagine my family's faces when I open them ...
Thanks again,
John
Edit: Do I need to put resistors in as well when I swap out these caps? Your renovation thread makes clear that they had a significant effect on the sound.
The 24uf needs a resistor in series after it, the electrolytics do not and I'm still working on the tweeter caps, at present I don't have any resistors with these and I'm doing listening tests.
I have the earlier speakers using 30uf in the mid range and 6uf not 6.2 for the Tweeter.
You will need approx 1.5 Ohm with the 24uf though personal taste might mean you go one side or the other from this value.
I use Mills MRA-12 (12w 1%) resistors from sonicraft. Welwyn from RS are pretty good and even the mundorf MOX from HiFi Collective.
If I was you I would wait until my listening tests for the resistor options are finished and I've got the voicing right, you may as well benefit from my experimenting. I will be publishing the results on my thread, diagrams, parts list etc.
The Cap selection is OK it's only the additional resistors I am juggling to get the speakers sounding as the originals. They sound pretty damn good now, I just want to make sure I squeeze every last drop from them.
Ken
The MRA12 from Sonicraft - is it the same resistor as:
http://www.hificollective.co.uk/catalog/resm1085-mra12-mills-resistor-p-1281.html
from hifi collective?
If so it'd easier for me to get them from there instead.
I'm not going to get the resistor(s) yet. I want to see how you finalise your speakers.
The capacitors I am ordering now though.
Thanks,
John
The MRA-12 at HFC are 5% accurate the ones at Sonicraft are 1% accurate otherwise they are the same.
In most of these applications it is more important to have as close a matching pair between the two x-overs than a spot on nominal value.
So as long as the values are out by the same amount it should not make too much difference. I have used a couple of these for speed and when I could not get the right value from anywhere else. The 5% are quite expensive here, the 1% from the States are roughly the same numerical price only in dollars.
The Mundorf MOX resistors are 2%. I ordered a bunch of these today from HFC and have a box full of various values from experimenting. I tend to use these, which are a lot cheaper, till I have worked out the right values then get the Mills from the states and swap them out. I prefere the Mills and think they sound better in some locations, but not by much. ;)
John - Don't know if you've ordered your caps yet?
I just noticed that HFC do a 2uf in the ClarityCap SA range, you could use two to make up the 4uf. Just drop one in to each position taken by the two green caps C3 and C4 on your board.
Should have spotted that earlier.
Hi Ken
Thanks for the heads up. The caps from Falcon are on their way already. I'll be getting the other caps on payday. I'm going to give them all to my expert soldering friend at the end of the month.
Can I just ask another quick question please? I take it your xovers are hard wired and don't have the edge connectors?
I'm just trying to work out how to install the wiring into this connector without butchering it.
Thanks,
John
Hi John
Mine are tag board with point to point wiring.
On the PCB type some folks solder the leads direct to the tracks, but there is not much room if your leads have a decent amount of copper.
With nearly all of these kind of connectors, the metal recepticals in the connector are push in and have a tag which springs up and locks into a slot to prevent them comming out. I am not familiar with this connector but would presume it is the same. If you can spot this and release the receptical with a pin or watch makers screw driver it can be withdrawn. They are usually crimped on to the wire, you can try and uncrimp it or just cut the wire and solder the new on to the end of the reseptical. You could even leave a short length of original wire and join the new on to this.
To be honest I don't like any of these soloutions.
Depending on whether you are bothered about originality, you could buy a piece of paxolin board and make your own version of the earlier tag board x-over. If you look at the pictures on my thread it is very easy to follow and is all on the top surface, there are no wires or parts on the underside. You can buy three way solder tags that could be fixed to the board using small nuts/bolts or pop rivets and use these to solder your parts to. The inductors should just unbolt from the PCB and your fitting new caps anyway.
This would give you a much better quality point to point x-over and allow thicker connecting wires to drivers/binding posts, it's worth thinking about.
The other thing that stands out like a sore thumb is the inductor orientation. You will almost certainly be getting inductive coupling between those big air cored inductors (ie acting like transformers) because they're too closely spaced on the same axis. Not sure if it's possible to turn a few through 90 degrees? (involving desoldering, re-fixing using cable ties and hot melt glue and re-soldering).
Thanks again - I'll take a closer look at the edge connector & see if there's a way to take the decent cable to the board. Failing that I reckon you're both right & a complete redesign is in order, complete with different X, Y, & Z orientation for the inductors.
Lots to consider. The laminate issue is forgotten for now.
John
Hi John
Hold off on buying a 24uf Polyprop for the mid range.
I am having lots of difficulty in trying to get a polyprop + ESR simulating resistors to work in this location without it having a nazel sibilant distortion in the upper mids crossing over to the tweeter. Most noticable on brass instruments when blown hard in the climax of a piece, not the highest notes but in the upper half of their range. Some folks might let this go, because the overall sound is very nice, but I just couldn't live with it as it is.
I have tried many combinations of values/type of resistor but they all have a down side. The best I could get was a combined value of 1.65 Ohm made up of 3.3//3.3 Ohm Mox resistors, Mills MRA-12 were not as good at reducing the fault but were more transparent overall and single resistors were much worse than parallel pairs giving the same value. Unequal values in parallel pairs gave a strange echo in piano notes. The 3.3//3.3 pairing flatened some piano notes around the x-over point to make adjacent notes sound the same, coming accross as being incorectly played, not quite like Les Dawson but it felt like the same note was being played in succession in complex pieces rather than different notes. None of the combinations gave results that I would be happy to live with long term. These things were not picked up at a local bake off and the speakers were well received, but I have specific test pieces of music that highlight some of these faults and where I look for certain traits when auditioning. I say this so you can appreciate these are subtle faults not allways evident on first listening or with an easy track.
I have a few alternative things to try, but it looks like this circuit needs the variable ESR that the original Electrolytics in this location brought into play. I started with a pair of Low Loss electrolytics in this position but these L.L. are also low in ESR and did not sound good at all, certainly not as good as the stock ancient ones I removed.
This one location is the only area I am unhappy with, but it has a big impact in the mid range output.
I will report back on my progress. :)
Thanks Ken - after a 2 year layup of my speakers I'm not in a hurry to bring them back into service. I'm more than happy to await your final verdict.
I take there are none of the caps made the same way as the originals any more, anywhere?
I'll replace the other caps & see how mine sound with the original 24 mid range left in for now until you have finished your deliberations. I'm genuinely excited to get the sound back out of these that I remember from long ago.
I've said it before but I am grateful to you for sharing your hard earned knowledge ...
Thanks
John
The original Elcap which were used extensively are no longer available.
Falcon recon the Alcap electrolytics they sell are the closest to sounding like an Elcap. I have found this to be true in some applications and not true in others.
The Mid range series cap is so important to the voicing of the mid range on the 66's that I would like to use some form of Polyprop for it's extra trancparency, but if need be I will try a single Alcap here as well.
I am going to try a combination of a cheap Polyprop (25uf) and an electrolytic (5uf) in parallel to make up the total of 30uf I need for my early version 66's. My theory here is I will get some of the benefits of the trancparency of the large value Polyprop and some of the ESR function of the smaller Electrolytic. I don't know if this has been tried before or what the result will be but its worth a go. If it works I will purchase a better quality Polyprop to substitute. :D
John, I also notice that on your pictures, the 24uf in the mid range is a 50v Low Loss Electrolytic, all the others are normal 50v.
Does the fact that it's a low loss cap make any difference to the sound? I'm guessing that they should all be one or the other ?
I'm becoming more and more surprised that my speakers made any sound at all ...
John - I think those Low Loss caps are original.
They did use mixtures of both to achieve the right effect.
LL caps have lower ESR than the ordinary electrolytics so yes, they will have a different sound.
John - don't be too worried about your x-overs.
Looking at your pictures I would say the top one is original appart from the 4uf in the mid range which has had a similar type of replacement electrolytic put in place.
The other board has also had this component changed but to a different make (the blue one) Neither of these changed parts will make a huge difference to the sound but for peace of mind and for only a few quid, it is better to make them both the same make and preferably the Alcap that you have ordered.
The Yellow Polyprops that have been used on the Tweeter filter on the second board are an issue. They appear to be only approximately the right value so better to change these and on both boards to the same make of the correct value. My experience of changing the original Tweeter caps, is that the modern Polyprops are a bit more efficient than the older design film caps they replaced. Consequently the Tweeter contribution seems a little louder than prior to changing them. This is easily remidied by using about -0.5db attenuation on the tweeter using an L-Pad, with a series resistor of 0.22 Ohm and a Parallel resistor of 68 Ohm. I did this on mine when changing to Polyprops for the tweeter and I couldn't hear any negative or unwanted changes to the high frequancy sound, just a little less of it. This seemed the right amount to integrate with the output from the other drivers, I tried -1db and that was too much.
If you need to know more about where the resistors go I can explain further but I will be showing this on my thread anyway.
As for renewing the other original but very old parts then I am still working on that as you know but renewing the 72uf electrolytics with the 100v Alcaps gave very possetive results with the bass with no down side. It's the mid range that is the tricky area, as soon as I touched these the balance and magic of the mid range was compromised, so that part is still a work in progress.
Morning Ken,
Payday - time to oder some more caps and cables. I've recieved the 4 & 72's from Falcon - excellent service from them btw. Today I'm ordering the tweeter caps from HFC (the sonicraft ones were just a little too much). I'm going to leave the 24 midrange completely alone until you're happy with the set up on yours. The midrange is too strong on mine at the moment so I'm hoping to regain some of the upper & lower ends in any case.
I'll order the cable you rate as well & get my expert friend to do all the soldering ...
Hopefully this time next week my old faithfuls should have a new lease of life.
Hi John
Yes hold off on the midrange 24uf cap and don't buy any resistors.
I'm getting there slowely tried another three combinations today they are now sounding very good indeed but there are another couple of things I want to try.
You will find it's not the mid range that gets rained in, it just sounds faster and cleaner, less tubby with new caps. It's the increase in Tweeter output that puts the mid range into proportion. The bass wont alter much but I think that by renewing the 72uf's even though parallel in the circuit, which shouldn't contribute much to the sound, actually it does. The bass comes accross to my ears anyway as slightly faster and more precise, cleaner sounding. This all contributes towards the effect of the midrange output being reduced but it really isn't its just the more noticeable output from both extremes and the extra mid range trancparency gives that impression.
Hi John
I've done some testing using the MD500 midrange (mine are the early MF500) and a 25uf series cap in the mid range and it works fine.
Just buy a pair of 25uf LOW LOSS 50v bi-polar Alcaps from Falcon accoustics. It's important that they are the low loss type. Note that they do not have 24uf.
No resistors are required, anywhere in the circuit.
Try this and see what you think.
If you feel the tweeter wants its level reducing I can advise on series and Parallel resistor values to create an L-Pad to lower the level, but I think it sounds about right without anything.
I have tried all kinds of combinations and types of caps including a mix of 80% PP and 20% Lytic which worked ok, but the cheaper LL lytic on its own was the best for your model with the MD500 midrange. (I have a set of both mid ranges).
Fantastic Ken, thanks so much for all of your help.
I'm currently burning in the 72's using your circuit design. On Friday I'll start the others. I'll order the 25's you recommend and once they're all burnt in I'll give them all to my expert friend to attach.
I'm really looking forward to hearing them again.
I'll let you know what the results are like.
John
John - Hows the work going on the x-overs?
Morning Ken,
The caps are all burned in & I'm passing the whole shooting match to my expert friend this evening over a beer or 2.
I'll ask his advice about connecting the larger wire to the x-over as well but I suspect that I won't be able to wait & that I'll put them back together for now with the new caps just to hear them working properly again.
The cosmetics on mine are going to have to wait for another day ...
Have you finished fine tuning yours?
John
Still working on them.
I have fitted the Seas 19TFF1 Tweeter which is a bit of an upgrade and looking at moving the x-over away from the big bass driver magnet and into the lower chamber. Keeping all the original parts intact so they can be returned to stock, in case I ever want to sell them.
walpurgis
29-09-2014, 10:29
Is there a reason for the tweeter change?
I particularly like the HF2000 for its sweet, smooth and uncoloured sound. Having used this unit many times in various projects, usually as a super tweeter, I reckon it's the best moving coil unit of its type that I've heard. Far better than the Coles and T27 for instance. I'm aware that in the 66 it's at the lowest end of its frequency limit and other tweeters may integrate better, but I'd certainly be rather unwilling to do away with it, unless I was opting for a ribbon driver maybe.
I've not used that particular SEAS tweeter, but does it sound better?
If you look at my 66 renovation thread it's all explained there.
But in summary. The HF2000 is basically good.
Any Tweeter suffers in the 66's application due to the x-over being electrically resonant, so it's being fed distortion.
The Seas Tweeter is slightly better, sweeter, cleaner and has an extended response like the HF2000, all round it's a damn good un.
It seems less prone to the resonance created by the 66 circuit so sounds much cleaner in this particular use.
I put this ability down to the ferofluid damping in the Seas unit, but its a guess, I have no proof that that is the case, either way listening tests show definate improvements in this area when using the Seas. It's a very easy fit both phisically and electrically and seems to dove tail very well with the mid range. The caps and inductor values need adjusting in the HF section of the x-over for it to work properly.
Ken - Thank you so much ... I've got my babies back.
I've just put the recapped xovers back in and given them some running and from the moment the first note emerged it was obvious they were vastly cleaner, brighter & have an almost completely restored bass.
After an hour of listening I'm captivated by them again. They aren't perfect but the improvements are huge.
My expert soldering friend - Ralph - had some horror stories about the caps he removed as well. Both of the yellow caps were incorrect, one C5 was 4.7 mfd & one of the 72's was quite literally falling apart.
They still need a little something on the bass side - I'm using the bass control on the amp to pick it up a little but that could just be down to where they are in the room and the laminate floor not being an ideal surface to put them on. On really complex pieces they can sound a tiny bit 'confused' is the best way I can describe it but I'm waiting to see if the caps burn in a little more and it settles down a bit.
I haven't swapped the posts or the wiring over yet - that's a job for later when I can convince Ralph to come over again and bring his nuclear powered iron with him, that and I was way too excited at the thought of hearing them again that I didn't want to wait. I did consider the idea of making a set of your custom plinths for mine. Did you say you were willing to send the moulds out in your restoration thread?
In summary, not 100% yet but I'd say 85% of the way there. Bearing in mind I believe I started somewhere in the mid-forties I'm a very happy listener today. I'm genuinely grateful to everyone who helped me in this thread but most especially to Ken who never seemed to get in a flap at my dumb questions ....
John - Glad you are getting a sound more like you expected.
What did you finaly end up using for the 24uf series cap in the midrange filter?
JohnB has first dibs with the mould for the base. He is comming up to the North East in a couple of weeks and will collect it then.
You could arrange to get it from him as I have no use for it now. :)
Morning Ken,
They sound so much better than they did. I tried lots of reference pieces (to me) but when I tried RichB's suggestion of track 1 from Robbie Robertson's 'How To Become Clairvoyant' the room just lit up with sound. It was a few seconds before I realised I was grining from ear to ear.
I used your suggestion for the 24's - the 25uf LL 50v bi-polar Alcaps from Falcon. The mid-range is reigned in much more than it was but that could be the effect you described to me earlier of simply the bass & treble rising around the mid.
As I said previously I still have some issues to address but in the scheme of things if I were to leave them alone now I wouldn't be unhappy. I need to be careful not to make the perfect the enemy of the good.
Thank you for the kind offer of the loan of the shuttering. I'll contact John B & see if I can pick them up from him when he's finished with them.
I find myself hoping that the rest of the family want to go shopping so that I can 'listen' to some music rather than have music on in the background ....
Thanks again,
John
just had a look at your crossover pdf and comparing the later type ditton 66 pcb board to the same ditton 44 board they use the same capacitors except C5 on the 66 is 4uf and on the 44 its 6uf.
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