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Old 14th August 2007, 04:48 AM   #111
sba is offline sba
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**************
SOUND CHECK---

I can't do a sound check on blackie's tweeters or crossovers, because I pulled the boards to get the capacitor info, and half of the capacitors crumbled apart. So the blackies are out of commission until I rebuild the boards.

Since we know that the two tweeters have slightly abnormal DCRs, you're suggesting, then, that we pay close attention to the replacement capacitance values in the treble circuit.....higher capacitance value in the crossover for the tweeter with the lower DCR....Is that correct?


***********************
CROSSOVER INDUCTORS---

These are the markings on the cloth tape of blackie's inductors:
1163
547
1358
1358
1359
The same as on Grahame's crossover layout (post # 34).



************************************************** ****
THE 30uf (24uf) CAP AT THE BOTTOM OF THE CROSSOVER---

I found this piece on the web:

Bypassing capacitors is a little like blending watercolors....
With capacitors, the signature of the base cap can be brightened, softened, darkened or lightened with the addition of the appropriate choice of bypass capacitor. The "perfect" tonal balance can only be determined by ear.

Classically, bypassing a capacitor means paralleling a very small cap (0.5% to 1% of the base cap) to improve the effective high frequency performance of the base cap. While this works to a point, the problem with simple bypassing it that it tends to sound a little discontinuous, with the large cap dominating the signature at the low end while the bypass cap dominates the upper extreme.

Cascade Bypassing (or simply "Cascading") is a bypassing method that yields the best and most homogeneous sounding combination of capacitance. Cascading is essentially paralleling smaller and smaller capacitors of increasing voltage to reach the target value. We usually suggest a cascade of 5% to 25% steps, with each smaller cap having a higher voltage rating. Cascading sounds better than simple bypassing because it yields an overall homogeneity to the sound of the equivalent capacitor

Examples of Cascade Bypassing are:
100.0F = 100F 100V + 5.0F 225V +1.0F 625V (=106F, within 10% of 100F)
11F = 10.0F 200V + 1.0F 600V + 0.10F 800V
5.0F = 4.0F 200V + 1.00F 600V + 0.10F 800V
3.3F = 3.0F 225V + 0.22F 625V + 0.10F 800V



Is this mumbo-jumbo?....I'm a novice! I wonder if Celestion was sort of "cascade bypassing" here at the bottom of the board, mounting a little 6uf 50v on top of the larger 24uf 25v cap.....or just simply assembling a 30uf total?

Also noticed--- While all the other caps seem to be non-polar (bi-polar), the large red-colored CCL 24uf 25v REV cap has colored markings on each end (black on the left, silver on the right, where the positive is connected). The black-colored end is also identified with a ridge.

More variations at this location---- The early woodie crossover ( serial# 13259 ) also has blackie's two cap configuration, except that the small ELCAP capacitor has been now been reduced from 6 mfd to 4 mfd.......
.....while the most recent woodie crossover ( serial# 27343 ) has but a single cap, a 24 mfd 50v L.L. N.P --exactly like the caps in Grahame's replacement crossovers (post #31).

So it seems that this particular location has evolved........from 30uf to 28uf to 24uf caps.....while the inductors have remained constant......and the power handling has increased from 50 to 80 w in the midrange driver.

Trimming back the total capacitance, then, at this location, should increase the safety of the midrange at the low end. Very good....I'm for that.

Lots to think about........no hurry


Sba
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Old 16th August 2007, 02:17 AM   #112
sba is offline sba
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Hi all,

It looks as though I must replace all the caps....I guess Ill start with blackies boards, see how things go, and then do woodies boards. No idea what this will cost.

Grahame & tondef2--- Did you ever get ESR cap readings from your crossovers? Were these included when you had your boards bench-tested? Sounds like you might have your own equipment, or know good technicians.

Now that all of you have sucked me into this project (he-he)....

.....Im wondering about this ESR cap thing.......it really seems to be one of the most important capacitance measurements. Moreover, many recommend that all replacement caps, even if new, be measured for ESR before installation. Apparently, even new caps, while measuring okay DCR and capacitance value, can fail miserably on ESR, and thus be worthless in a circuit.

sba
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Old 16th August 2007, 04:49 AM   #113
Grahame is offline Grahame  United States
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Quote:
Originally posted by sba
[
Grahame & tondef2--- Did you ever get ESR cap readings from your crossovers? Were these included when you had your boards bench-tested? Sounds like you might have your own equipment, or know good technicians.
sba [/B]
No such luck I'm afraid. I only have a multi-meter, a soldering iron, and an inquiring mind! There are ESR meters on the web - a bit too expensive for just a few measurements.

It seems like we need to get accurate values for the original parts, so we can replace them with equivalent parts, or construct a set of parts that has the same (or better) performance, and behaves in the desired manner.

I may be able to co-opt some better measuring gear in the next two weeks. If so I'll post my findings.

Grahame
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Old 16th August 2007, 03:58 PM   #114
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Location: Midlands
Quote:
Originally posted by sba
Alan,

You, too, could own a specially named pair of 66s......Blackies


Thankyou for the Link sba, but if I buy 66s I would prefer "Woody" vintage for the 80watt MD500.
I see the seller has spares for all the other drivers, but none for the MD500, and given tonedef2's experience and warnings about the MD500s {I forget if in this Thread or in one of the other threads} I am very wary of buying the oldest MD500s without actually hearing them first !
If some-one had a working pair of those B&O 5700s with the older MD500s, then buying the Blackie spares could allow owner to build a nice vintage speaker system !


Quote:
Originally posted by sba
**************
SOUND CHECK---

I can't do a sound check on blackie's tweeters or crossovers, because I pulled the boards to get the capacitor info, and half of the capacitors crumbled apart. So the blackies are out of commission until I rebuild the boards.

---> maybe you can, more on this later !

__________________________________________________ __

Since we know that the two tweeters have slightly abnormal DCRs, you're suggesting, then, that we pay close attention to the replacement capacitance values in the treble circuit.....higher capacitance value in the crossover for the tweeter with the lower DCR....Is that correct?

---> Yes, and more on this later ...

__________________________________________________ __


************************************************** ****
THE 30uf (24uf) CAP AT THE BOTTOM OF THE CROSSOVER---

I found this piece on the web:

Bypassing capacitors is a little like blending watercolors....
With capacitors, the signature of the base cap can be brightened, softened, darkened or lightened with the addition of the appropriate choice of bypass capacitor. The "perfect" tonal balance can only be determined by ear.

Classically, bypassing a capacitor means paralleling a very small cap (0.5% to 1% of the base cap) to improve the effective high frequency performance of the base cap. While this works to a point, the problem with simple bypassing it that it tends to sound a little discontinuous, with the large cap dominating the signature at the low end while the bypass cap dominates the upper extreme.

Cascade Bypassing (or simply "Cascading") is a bypassing method that yields the best and most homogeneous sounding combination of capacitance. Cascading is essentially paralleling smaller and smaller capacitors of increasing voltage to reach the target value. We usually suggest a cascade of 5% to 25% steps, with each smaller cap having a higher voltage rating. Cascading sounds better than simple bypassing because it yields an overall homogeneity to the sound of the equivalent capacitor

Examples of Cascade Bypassing are:
100.0F = 100F 100V + 5.0F 225V +1.0F 625V (=106F, within 10% of 100F)
11F = 10.0F 200V + 1.0F 600V + 0.10F 800V
5.0F = 4.0F 200V + 1.00F 600V + 0.10F 800V
3.3F = 3.0F 225V + 0.22F 625V + 0.10F 800V



Is this mumbo-jumbo?....I'm a novice!

---> there is some truth in this, but this is a complex subject, and would take me a long time to explain, thus I will only comment on its relevance to this Celestion project, and that is basically I doubt there would be much audible benefit, but we can discuss this more later, AFTER all of you have decided how you are going to fit the new caps on your old boards, because the Polypropylene caps, and anything else as good, are all larger size dimensions than those old Black electrolytics.
More on this later.

__________________________________________________ __ I wonder if Celestion was sort of "cascade bypassing" here at the bottom of the board, mounting a little 6uf 50v on top of the larger 24uf 25v cap.....or just simply assembling a 30uf total?

---> No, I very much doubt Celestion were doing such, and that pair on your board could possibly be some-one else's modification later ... thus check very closely the solder joints to all those 24uF and piggy-backed smaller caps, and compare the solder joints' colour , etc ... to the original solder joints around all the other components to see if its possible some were re-soldered later .?.

__________________________________________________ __

Also noticed--- While all the other caps seem to be non-polar (bi-polar), the large red-colored CCL 24uf 25v REV cap has colored markings on each end (black on the left, silver on the right, where the positive is connected). The black-colored end is also identified with a ridge.

---> That CCL 24Uf could be an electrolytic - more on this later as time is running out here.

__________________________________________________ __

More variations at this location---- The early woodie crossover ( serial# 13259 ) also has blackie's two cap configuration, except that the small ELCAP capacitor has been now been reduced from 6 mfd to 4 mfd.......
.....while the most recent woodie crossover ( serial# 27343 ) has but a single cap, a 24 mfd 50v L.L. N.P --exactly like the caps in Grahame's replacement crossovers (post #31).

So it seems that this particular location has evolved........from 30uf to 28uf to 24uf caps.....while the inductors have remained constant......and the power handling has increased from 50 to 80 w in the midrange driver.

---> These are the ones to check visibly to see if all seem originals or if later added - check the solder joints, and Post about.

__________________________________________________ __


I'm about to be Shut-Down, sorry - have to go , more next time !
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Old 17th August 2007, 05:34 AM   #115
sba is offline sba
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Alan--

Very good point about where to put these new and larger capacitors....I hadn't paid attention to their size.

On the older point-to-point boards ( I haven't seen the modern boards upclose) the limited space problem seems to be primarily at the 72uf and 24uf locations. This is probably unorthodox, but I think that, at those locations, the new larger caps can be mounted to the underside of the board......several holes drilled to place plastic zip ties in order to hold the caps in place....and several holes drilled for threading the leads to the top side. There's already a spare half inch underneath, so the entire board would need to be raised about another inch and a half. If this gets to close to the woofer, the board could be remounted to the side, or behind the ABR, or even (he-he) externally on the back, in a see-through Plexiglas enclosure.

sba
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Old 17th August 2007, 03:57 PM   #116
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Default Check also ...

Quote:
Originally posted by sba
[B
More variations at this location---- The early woodie crossover ( serial# 13259 ) also has blackie's two cap configuration, except that the small ELCAP capacitor has been now been reduced from 6 mfd to 4 mfd.......
.....while the most recent woodie crossover ( serial# 27343 ) has but a single cap, a 24 mfd 50v L.L. N.P --exactly like the caps in Grahame's replacement crossovers (post #31).

So it seems that this particular location has evolved........from 30uf to 28uf to 24uf caps.....while the inductors have remained constant......and the power handling has increased from 50 to 80 w in the midrange driver.




[/B]

Another possible reason for the larger series capacitance to the MD500 in the 50watt version is that perhaps that version of the driver had a different Fs to the later 80watt version, and thus a slightly different Impedance around the 500Hz area, and/or a slightly different Frequency Response at the low end of its useable spectrum.
Look at the Plots for the Morel and Vifa/Peerless mid-domes I posted Links to in an earlier long Post in this Thread so you can see what I mean by Impedance and Frequency Response around the lower end of such drivers' spectrum - the relevant atrea of spectrum is from the driver's Fs to at least one Octave above.

Thus, perhaps the older MD500s needed a larger cap.

OR, perhaps there was a change to the woofer's output around the approximately 300Hz - 600Hz region, and the MD500 had to be extended a bit lower in frequency to allow for that, compared to the later woofers.

Check both vintages of woofers to see if any evidence on their labels, or stampings on their chassis or back of their cones, or simple visible differences in the front of their cones, of differences between the vintages.
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Old 18th August 2007, 03:57 PM   #117
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Default the old Capacitors

sba,
see my comments I've added inside the Quote Box below for each section on capacitors --->

Quote:
Originally posted by sba
Alan-- I pulled the crossovers from the two older blackies and got the info from all of the capacitors:

****************************
TREBLE SECTION I

serial #249
(2)
ERIE
A 304
Metallised
2-0 uf 150 v
TYH

---> these are probably Paper-in-oil, and may still be OK if there is not evidence of substances leaking from within - look around where the leads connect to the body.
__________________________________________________ __


compared to
serial # 344
(2)
Arco 1.05
2,2 / 10
100 v -

---> these are a Plastic film cap, probably a Polyester dielectric type. They have long life unless over heated by by excess signal drive, etc ... , but are low-average audio quality compared to Polypropylene.
As they are each 2.2uF, X2 = 4.4uF , instead of Celestion's 4uF, check their solder joints to see if original, or if evidence of later soldering - they could have been installed by a modifier or repairperson.
__________________________________________________ __

****************************
TREBLE SECTION II

serial #249
(3)
ERIE
A 304
Metallised
2-0 uf 150 v
TYH

compared to
serial # 344
(4)
ERIE
A 316
Metallised
1.5 uf 150 v
D. CWKG
73 / 25

---> both are lkely paper-in-oil, as above. The "metallised" refers to a metal film bonded to the paper for one of the poles.
Look for signs of leaking substances around the lead wires into the body.
__________________________________________________ __

*****************************
TOP OF THE BOARD:

both blackies have (1) ELCAP 4 mfd 50 v

****************************
RIGHT SIDE OF THE BOARD:

serial #249
has, in two different locations--
ELCAP 72 mfd 50 v N.P.

compared to serial #344
which has, in two different locations, groups of three capacitors:
(2) ELCAP 30 mfd 50 v
+
(1) ELCAP 12 mfd 50 v

---> all these are old Electrolytic caps.
__________________________________________________ __

*****************************
BOTTOM OF THE BOARD:

serail #249
(1) ELCAP 6 mfd 50 v
+
(1)
CCL
24 uf
25 V.D.C. REV
WE 99RAS
MAY 73

compared with
serail #344
(1) ELCAP 6 mfd 50 v
+
(1)
CCL
24 uf 25 v REV
WE 99RAS
AUG 73

---> more Electrolytic caps.
__________________________________________________ __

The total here at the bottom of the board, 30 uf, seems to be 6 uf higher than some of the other boards which total only 24 uf (e.g., post # 34). Hmmmm.

---> see my prevoius Post for discussion of this, and more later...
__________________________________________________ __

********

All of the ERIE capacitors in the treble sections are crumbling in my hands.


----> outer Insulation only, the caps may still be OK to use, but I'll Post more on this as soon as time is available.
__________________________________________________ _


sba
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Old 20th August 2007, 04:09 PM   #118
sba is offline sba
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Thanks Alan.......I'll investigate further & post.
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Old 4th September 2007, 03:50 PM   #119
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Default more about the diffraction control

Quote:
Originally posted by tonedef2

Alan>

1-Yes the sound is cleaner, however im-having trouble with something that may look goodQ>so Alan how thin can I go on the wool? Can you save me time trying endless thicknesses, also if you look at the front baffle, you will see that the outer router grooves that run the length of each side have 2 reflecting points as well!!!
So I will (after hearing from Alan regarding wool thickness) try and cover the entire top section for a test, if positive then the hard part of fabricating something removable, that wont damage the wood and still accommodate grill placement can begin, L.


3-
Ill need to replace the cardboard around the tweeter after removal of rings, cardboard in integral too as its used to hold the diaphragm in place.


Alan could the simple application of 2 fairly thick and wide felted wool rings work to avoid the many reflecting & diffracting points on these baffles with the exception of the top overhang?


ToneDef2/ Pete

Hi Pete,

do take care with that cardboard ring part of the HF2000.
I know you're skilful at restoring, but if that cardboard tears in as far as the dome diaphragm of the tweeter then the dome itself may be damaged.

When you have sorted out the placement of the wool felt you will not need those oval diffraction stick-on accesories, thus I advise you carefully remove them when you are doing the wool-felt placement.
It will be better to listen with only the wool in various positions, without the ovals, so that you can clearly hear the effects of the wool placement options.
Also you would then not have the 8 kHz <--> 12 kHz response annomaly problem that the ovals cause.
Put the ovals around the tweeters of another pair of speakers - ones that you don't intend to spend a lot of time trying to get the best possible sound from - ones that have non-ideal cabinet edges, thus have treble diffraction problems also.

You could do as you wrote, and use two fairly thick and wide felted wool rings - one around the HF2000 and one around the MD500.
Cut the inner hole for each with a diameter so that it fits closely and neatly {no gaps} around the outside edge of the round front-plate of each driver,
though seeing how close the HF2000 and MD500 are, it would be acoustically better if you used a rectangle of wool felt to cover the area for both, and all the way to under the top lip of the cabinet, and all the way down to the top edge of the woofer chassis edge, and cut two holes in the rectangle.

If the wool is soft, then cut it the full thickness that will fit under the grille, but not thicker so that the grille would compress it, as that may reduce its absorption .
It will reduce absorption if it is compressed tight.

ALTERNATE :-

I have studied the photo you posted in #91 on page 4.

I have forgotten as so long since I've seen 66s.
How much space is under the grille to accomodate thickness, that is, how thick will fit ?

AND, around the bevelled edges of the cabinet under the grille, how much thickness will fit ?

If you want the job done for listening to be done with the grilles on, then I recommend you cut larger pieces of wool-felt - as thick as will fit under the grille, and place them from around both sides so that they cover the bevelled edges and bend around to cover the front baffle to at least 2" in from the flat front edges.
How far further in you extend the wool depends on how you want it to look.
If you will always listen with the grilles on, then wool visibility is not a problem.
If the wool will fit around the edges and cover the bevelled sections, then 2" in on the flat front may be sufficient, but take it to closer to the MD500 flange if you wish - to about 1/2" away.

If you use this option then you will not need to cut and fit the rectangular piece with 2 holes I described above - it will not be needed.

The grille could simply hold the long bent around wool pieces in place - one long vertical piece for each side.

Do not glue them to the back of the grille, unless with only a few small spots of adhesive, because the adhesive when hard will prevent the wool from absorbing the sound.

A strip across the top, under the grille and abbutted to under the top lip and width down to the top outer edge of the cardboard ring section of the HF2000 could be sufficient, but it likely will need another strip stuck on the outer of the grille, and of thickness to extend it to the outer edge of the top lip of the cabinet to sufficiently reduce audible diffraction.
This outside strip need only extend down about 3/4" <--> 1" below the lip - it does not need to extend as far as the under grille strip, as sound will already be absorbed under the grille, and above the grille the sound will be striking at an angle to the vertical.

To advise any better than this I need to know how much thickness will fit under the grille -
- for the front panel ?
- for the bevelled edges ?
__________________________________________________ __

If you want to listen with the grilles off, then I would advise differently.
__________________________________________________ __

Yes, those outer routed flats - vertically down each side of the cabinet outside the grille frame ...

Yes, they will cause diffraction, but what-ever you put over them you will have to look at - not a problem for me as I don't care too much about the visual, and often listen with eyes closed ...

If you have decided the full under-grille and around bevelled edges option I described above, then that will take care of almost all the treble and much of the midrange frequencies' diffraction {if the wool can be fitted thick enough}, and those outer flat sections will cause diffraction of mostly the sound from the woofer - mostly from 500 Hz down - audible, but less an audible nuisance than higher frequencies.

The under top lip diffraction of the treble is much more distorting of the tone and of details in the music than the lower frequencies diffraction, thus when you have got the top sections the way you are happy with the sound from, you may not wish to proceed further for little further improvement in sound at greater visual disturbance ...

I don't know ... tell me your preferences ?
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Old 5th September 2007, 10:58 AM   #120
ReLLaXX is offline ReLLaXX  Romania
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First of all, hello everybody... And second, I hope you can excuse my wnglish and also understand at least half of what I am writing.

Proud owner of Celestion 66's, more woodies than blackies. In a few days a full restauration process will begin, going from the cabinets to the speakers and crossovers. Everything I want to do is to take them back to the initial state, not transform them in something else.

So yes, last night (I have a few hours offset) I read all this topic taking notes and now I allready have a good starting point. I hope I am amble to start working, taking photos and show you some details in a few days. My work agenda is pretty ful those days, but I hope I will manage somehow.


So once again, thanks for the great imput on 66's, hope I can help also with a few ideas.

Got to go now, I will write more later.
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