oh my......look at these capacitor prices!
http://www.vacuumtube.com/capacito.htm
http://www.audiolamp.com/page30.html
http://www.audience-av.com/capacitors/a_prices.php
http://www.vacuumtube.com/capacito.htm
http://www.audiolamp.com/page30.html
http://www.audience-av.com/capacitors/a_prices.php
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
compared to
serial # 344
(2)
Arco 1.05
2,2 / 10
100 v -
****************************
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
*****************************
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
*****************************
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
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.
********
All of the ERIE capacitors in the treble sections are crumbling in my hands.
sba
****************************
TREBLE SECTION I
serial #249
(2)
ERIE
A 304
Metallised
2-0 uf 150 v
TYH
compared to
serial # 344
(2)
Arco 1.05
2,2 / 10
100 v -
****************************
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
*****************************
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
*****************************
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
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.
********
All of the ERIE capacitors in the treble sections are crumbling in my hands.
sba
I just noticed another difference in my speakers--
The older blackies have the MF 500 midrange rated at 50 w
and the newer woodies have the MD 500 midrange rated at 80 w .
[ I weighed a midrange (I forgot which one) and it was around 6 lbs .]
Also.....the newer woodies have a larger paper gasket surrounding the tweeter.
The older blackies have the MF 500 midrange rated at 50 w
and the newer woodies have the MD 500 midrange rated at 80 w .
[ I weighed a midrange (I forgot which one) and it was around 6 lbs .]
Also.....the newer woodies have a larger paper gasket surrounding the tweeter.
Hello all,
sba you have a bit of a mess there, would think that someone or ones have swaped and or alterd those 66's, but can't be sure, may be factory too!
You are goning to be very pleased with the sound when where done, as your cap values are probably all over the board...
My crossovers where bench tested and found to be within spec so after i resored the mid dome i was amazed at the quality of reproduction...now we are working on the speakers older design limitations...
More later a-boating we will go......🙂
sba you have a bit of a mess there, would think that someone or ones have swaped and or alterd those 66's, but can't be sure, may be factory too!
You are goning to be very pleased with the sound when where done, as your cap values are probably all over the board...
My crossovers where bench tested and found to be within spec so after i resored the mid dome i was amazed at the quality of reproduction...now we are working on the speakers older design limitations...
More later a-boating we will go......🙂
Hello three 66ers !
I see a lot of interesting developments and new problems identified - more than I will have time to address in this session, so I'll start with some, do as much as I have time for, and will not forget the others, so don't worry, I'll get to everything eventually !
I'll post a few comments inside the Quote Box for specific clarity :-
The 9.2 ohm HF2000 could be either :-
(A) an alternate model with twice the impedance voice-coil - such is common, and it may have been manufactured to use with a higher impedance mid or mid-bass driver in a different Celestion speaker, or, so that two tweeters could be used in Parallel for higher output treble level in a larger speaker, as those tweeters along with most tweeters of that era were fairly low power dissipation and became defective under the heat condition of high signal level drive {the adhesives would melt, and sometimes even the wire itself, and then if made of paper the coil formers would burn. Modern tweeters use high-temp capable formers and adhesives}.
Thus a sample of such tweeter could have got mixed up with a batch of the lower impedance ones and then installed - doesn't say much for Quality Control Inspections ! , unless a Service-man installed it later after the original tweeter became faulty, not realizing which impedance version was to be used.
(B) that tweeter is failing as result of its voice-coil rubbing against something, or similar mishap, which has worn away part of the diameter of the wire strand at one or more places - thinner wire has higher resistance.
____________________________________________________
Is that tweeter still working ?
Play some music with a lot of Cymbals or Steel String Acoustic Guitar or Violins - quietly - and put your ear very close to the tweeter.
If it is working then listen to the other tweeter- at exactly the same ear distance - to hear if any any significant difference in output ... but, choose music where the same treble information is is both channels, ... or if you have an Audio Frequency Oscillater or a CD with Test Tones, then play some tones that are significantly above 5 kHz {so the mid-driver's output does not interfere}. Try between 8 kHz and 12.5 kHz. When the frequency gets to 16 kHz you may have difficulty hearing it, and as the frequency is swept higher - from about 6 kHz upwards, the degree you hear it depends very much on the angle your head is at towards the sound source. Try twisting your head - you may be surprised !
If no test tones, and you can't reliably hear the tweeter distinct from the mid-driver with music, then disconnect the mid-driver, BUT .. then you must only use low level signal, because when there is no terminating resistive impedance to that dual filter in the mid-range x-over there becomes 2 resonant points of almost short circuit {at two specific frequencies} - yes, even though you have not joined the 2 wires from the driver together.
There is only the two low DCRs of the two inductors as Load to your amplifier, thus use low volume output so as to not draw excess current from your amp which may damage your amp's output stage.
If you are worried, connect a resistor - a cheap 5 watt wire-wound is sufficient - of a resistance between 6.8 <--> 10 ohms where the MD500 would have been connected.
Post whether the 9.2 ohm HF2000 is working, and if at similar output level to the 4.6 ohm one.
I am VERY surprised that you are not hearing a difference in part of the treble spectrum, because the electrical effect of a double impedance tweeter connected to that treble filter will cause its cut-off to be at half the frequency, that is at 2.5 kHz instead of 5 kHz !
Thus there will be an octave of overlap between the MD500 and HF2000 in one of your 66s and not in the other.
No, that does not necessarily result in higher output between 2.5 k and 5 kHz, because in the 66 the two drivers are connected with one in the opposite Polarity to the other, thus there will be some cancellation of output as well as some addition - which where in that Octave, and in about another octave both below and above, will depend on the Phase relationships between the two drivers themselves as well as those caused by the mis-terminated treble filter.
But, all this should result in one 66 having significantly different Tone in part of its lower treble spectrum to the other 66 !
If the HF2000 is still working OK, then good, but don't play your 66 any louder than in the past, because that HF2000 being driven an octave below is putting a lot more power into it than the 66 design intended.
The extra power is still being dissipated in the tweeter even if it is being acoustically cancelled by phase differences, thus the tweeter can be damaged if driven harder.
I have two options for you to continue to use that HF2000 if it is stll working OK, thus post your assessment of it.
____________________________________________________
sba,
try the above listening test with your Blackie #344, and compare audibly with Blackie #249.
The 25% higher DCR tweeter in #344 may simply be sample variation, or an accidentally overwound voice-coil, OR, as it seems your two Blackies were originally from different Production Batches the differences in the tweeters may have simply been two different Production Types - one for each period {such was an occasional event then}.
Also, swap the two Blackie cross-over boards - each to the other speaker.
Put the board with the two yellow 2.2uF Arcos into Blackie #249, because with the lower impedance tweeter there it will require larger capacitance to give close to the same crossover frequency that you will then get with the two 2uF Erie A304 caps put in circuit to the higher impedance tweeter in #344.
Yes both boards have the same summed equivalent of 6uF for the other treble filter cap, and the likely same value of inductance in the filter inductor, but with the boards swapped you will have closer to the same cross-over frequency than you currently have.
When you do that, have a look around the inductor coils, and at the under side of the board, to see if any Part Numbers for those inductors.
I am wondering if Celestion used different value inductance in the early model 66 than in the later model 66, at least in the mid-range filter, given that they have 30uF there instead of the 24uF used in the later models.
30uF there will significantly lower the cut-off frequency below the 500 Hz of the specification of the later model, thus the older MD500 will be working a lot harder as it has to move greater distance in-out to reproduce the lower frequencies sent to it via the 30uF cap, and it is a lower power rated MD500 !
I see a lot of interesting developments and new problems identified - more than I will have time to address in this session, so I'll start with some, do as much as I have time for, and will not forget the others, so don't worry, I'll get to everything eventually !
I'll post a few comments inside the Quote Box for specific clarity :-
Grahame said:
The 9.2 ohm HF2000 could be either :-
(A) an alternate model with twice the impedance voice-coil - such is common, and it may have been manufactured to use with a higher impedance mid or mid-bass driver in a different Celestion speaker, or, so that two tweeters could be used in Parallel for higher output treble level in a larger speaker, as those tweeters along with most tweeters of that era were fairly low power dissipation and became defective under the heat condition of high signal level drive {the adhesives would melt, and sometimes even the wire itself, and then if made of paper the coil formers would burn. Modern tweeters use high-temp capable formers and adhesives}.
Thus a sample of such tweeter could have got mixed up with a batch of the lower impedance ones and then installed - doesn't say much for Quality Control Inspections ! , unless a Service-man installed it later after the original tweeter became faulty, not realizing which impedance version was to be used.
(B) that tweeter is failing as result of its voice-coil rubbing against something, or similar mishap, which has worn away part of the diameter of the wire strand at one or more places - thinner wire has higher resistance.
____________________________________________________
Is that tweeter still working ?
Play some music with a lot of Cymbals or Steel String Acoustic Guitar or Violins - quietly - and put your ear very close to the tweeter.
If it is working then listen to the other tweeter- at exactly the same ear distance - to hear if any any significant difference in output ... but, choose music where the same treble information is is both channels, ... or if you have an Audio Frequency Oscillater or a CD with Test Tones, then play some tones that are significantly above 5 kHz {so the mid-driver's output does not interfere}. Try between 8 kHz and 12.5 kHz. When the frequency gets to 16 kHz you may have difficulty hearing it, and as the frequency is swept higher - from about 6 kHz upwards, the degree you hear it depends very much on the angle your head is at towards the sound source. Try twisting your head - you may be surprised !
If no test tones, and you can't reliably hear the tweeter distinct from the mid-driver with music, then disconnect the mid-driver, BUT .. then you must only use low level signal, because when there is no terminating resistive impedance to that dual filter in the mid-range x-over there becomes 2 resonant points of almost short circuit {at two specific frequencies} - yes, even though you have not joined the 2 wires from the driver together.
There is only the two low DCRs of the two inductors as Load to your amplifier, thus use low volume output so as to not draw excess current from your amp which may damage your amp's output stage.
If you are worried, connect a resistor - a cheap 5 watt wire-wound is sufficient - of a resistance between 6.8 <--> 10 ohms where the MD500 would have been connected.
Post whether the 9.2 ohm HF2000 is working, and if at similar output level to the 4.6 ohm one.
I am VERY surprised that you are not hearing a difference in part of the treble spectrum, because the electrical effect of a double impedance tweeter connected to that treble filter will cause its cut-off to be at half the frequency, that is at 2.5 kHz instead of 5 kHz !
Thus there will be an octave of overlap between the MD500 and HF2000 in one of your 66s and not in the other.
No, that does not necessarily result in higher output between 2.5 k and 5 kHz, because in the 66 the two drivers are connected with one in the opposite Polarity to the other, thus there will be some cancellation of output as well as some addition - which where in that Octave, and in about another octave both below and above, will depend on the Phase relationships between the two drivers themselves as well as those caused by the mis-terminated treble filter.
But, all this should result in one 66 having significantly different Tone in part of its lower treble spectrum to the other 66 !
If the HF2000 is still working OK, then good, but don't play your 66 any louder than in the past, because that HF2000 being driven an octave below is putting a lot more power into it than the 66 design intended.
The extra power is still being dissipated in the tweeter even if it is being acoustically cancelled by phase differences, thus the tweeter can be damaged if driven harder.
I have two options for you to continue to use that HF2000 if it is stll working OK, thus post your assessment of it.
____________________________________________________
sba,
try the above listening test with your Blackie #344, and compare audibly with Blackie #249.
The 25% higher DCR tweeter in #344 may simply be sample variation, or an accidentally overwound voice-coil, OR, as it seems your two Blackies were originally from different Production Batches the differences in the tweeters may have simply been two different Production Types - one for each period {such was an occasional event then}.
Also, swap the two Blackie cross-over boards - each to the other speaker.
Put the board with the two yellow 2.2uF Arcos into Blackie #249, because with the lower impedance tweeter there it will require larger capacitance to give close to the same crossover frequency that you will then get with the two 2uF Erie A304 caps put in circuit to the higher impedance tweeter in #344.
Yes both boards have the same summed equivalent of 6uF for the other treble filter cap, and the likely same value of inductance in the filter inductor, but with the boards swapped you will have closer to the same cross-over frequency than you currently have.
When you do that, have a look around the inductor coils, and at the under side of the board, to see if any Part Numbers for those inductors.
I am wondering if Celestion used different value inductance in the early model 66 than in the later model 66, at least in the mid-range filter, given that they have 30uF there instead of the 24uF used in the later models.
30uF there will significantly lower the cut-off frequency below the 500 Hz of the specification of the later model, thus the older MD500 will be working a lot harder as it has to move greater distance in-out to reproduce the lower frequencies sent to it via the 30uF cap, and it is a lower power rated MD500 !
sba said:
Well, I read I mis-spelt your original "blacky" to blackie,
and your original "woody" to woodie, and now every-one is doing that, including yourself, thus I suppose you don't mind ... ?
Who are thes guys anyway - are they members of the Rolling Stones, or members of the Bay City Rollers ?
OK, so "Blackie" is the name of one of Eric Clapton's guitars, so perhaps Woodie or Woody is his cousin ? - well guitars are basically made from wood ...
____________________________________________________
Is your spare woofer from the same production batch as one or other of the samples in your different 66s, or seeming later manufacture ?
____________________________________________________
The "tower arrangement" - do you have the top of tower pair standing in the same orientation as the lower pair, or , do you have the upper pair upside-down ?
One orientation will give a different sound to the other, in both treble and bass response, and some other audible aspects.
Try both and hear, {if you haven't already done so}.
Which orientation do you prefer ?
The Rolling Stones...........given the choices, you?
I prefer super synthetic snake oil myself.
ToneDef2 🙂
I prefer super synthetic snake oil myself.
ToneDef2 🙂
Alan,
You, too, could own a specially named pair of 66s......Blackies
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=290148248147&ssPageName=STRK:MEWA:IT&ih=019
You, too, could own a specially named pair of 66s......Blackies
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=290148248147&ssPageName=STRK:MEWA:IT&ih=019
**************
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:
100.0µF = 100µF 100V + 5.0µF 225V +1.0µF 625V (=106µF, within 10% of 100µF)
11µF = 10.0µF 200V + 1.0µF 600V + 0.10µF 800V
5.0µF = 4.0µF 200V + 1.00µF 600V + 0.10µF 800V
3.3µF = 3.0µF 225V + 0.22µF 625V + 0.10µF 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
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:
100.0µF = 100µF 100V + 5.0µF 225V +1.0µF 625V (=106µF, within 10% of 100µF)
11µF = 10.0µF 200V + 1.0µF 600V + 0.10µF 800V
5.0µF = 4.0µF 200V + 1.00µF 600V + 0.10µF 800V
3.3µF = 3.0µF 225V + 0.22µF 625V + 0.10µF 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
Hi all,
It looks as though I must replace all the caps....I guess I’ll start with blackie’s boards, see how things go, and then do woodie‘s 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)....
.....I’m 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
It looks as though I must replace all the caps....I guess I’ll start with blackie’s boards, see how things go, and then do woodie‘s 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)....
.....I’m 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
sba said:
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
sba said:
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 !
sba said:
I'm about to be Shut-Down, sorry - have to go , more next time !
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
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
Check also ...
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.
sba said:
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.
the old Capacitors
sba,
see my comments I've added inside the Quote Box below for each section on capacitors --->
sba,
see my comments I've added inside the Quote Box below for each section on capacitors --->
sba said:
more about the diffraction control
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 ?
tonedef2 said:
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 ?
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.
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.