needs correction !
When I Post in a hurry without having carefully re-read what I wrote I sometimes miss that I have forgotten something, or have used a poor choice of words, such as for the below !
You will not be able to make accurate resistance readings with the L-pads connected to the x-over,
because the capacitors in the circuit will attempt to charge up with the current supplied by the meter to the resistors,
and they will simultaneously discharge through the L-pads,
thus you will get an unstable, and likely quite inaccurate reading, and the battery will drain fast in your meter !
What I meant to write was:- carefully disconnect the L-pads from the circuit in such way as to not move the setting knobs from the positions you chose after listening, so that you retain exactly the resistance settings.
Then measure the DC resistance in each arm of each L-pad with respect to the contact point under the setting knob.
That is, the arms are from each side of the contact point under the knob.
Measure fairly quickly, because the low resistances here will be draining your meter's battery, and if the current drops too low there will not be sufficient voltage drop across the resistor for the meter to be able to accurately calculate resistance.
This advice applies for all resistances up to about 500 ohms approximately.
******************************************************
You were correct to connect the Bi-wiring to Mid + Treble together with Bass separately.
I suspect the Wilmslow fellow does not know, or understand, the good aspects and the compromises in the 66 design.
*******************************************************
Hah dloper, there you are posting again at the same time as I am ! , but I have to go now.
I'll comment further on those and your other earlier points next time.
*******************************************************
Hi jwt,
if you can't buy Mail-Order from the USA, can you from continental Europe, such as Italy ?
{or Holland or France ?}.
There is very limited available in the UK that is not physically too large to fit neatly on the circuit boards.
I'll write more about where to buy next time.
Though if you are re-wiring now, leave OUT the thick cable, especially from the mid and treble circuits !
It's probably OK in the bass circuits.
Can you Post photos of your crossovers ?
Like those attached to some earlier posts in this thread,
and/or Post a diagram of each crossover so that I can see the differences you are describing.
What is the model number of your Dynaudio mid-domes ?
Read the entire Thread through before you buy anything or spend a lot of time changing things.
I'll comment on your other points next time.
When I Post in a hurry without having carefully re-read what I wrote I sometimes miss that I have forgotten something, or have used a poor choice of words, such as for the below !
You will not be able to make accurate resistance readings with the L-pads connected to the x-over,
because the capacitors in the circuit will attempt to charge up with the current supplied by the meter to the resistors,
and they will simultaneously discharge through the L-pads,
thus you will get an unstable, and likely quite inaccurate reading, and the battery will drain fast in your meter !
What I meant to write was:- carefully disconnect the L-pads from the circuit in such way as to not move the setting knobs from the positions you chose after listening, so that you retain exactly the resistance settings.
Then measure the DC resistance in each arm of each L-pad with respect to the contact point under the setting knob.
That is, the arms are from each side of the contact point under the knob.
Measure fairly quickly, because the low resistances here will be draining your meter's battery, and if the current drops too low there will not be sufficient voltage drop across the resistor for the meter to be able to accurately calculate resistance.
This advice applies for all resistances up to about 500 ohms approximately.
******************************************************
You were correct to connect the Bi-wiring to Mid + Treble together with Bass separately.
I suspect the Wilmslow fellow does not know, or understand, the good aspects and the compromises in the 66 design.
*******************************************************
Hah dloper, there you are posting again at the same time as I am ! , but I have to go now.
I'll comment further on those and your other earlier points next time.
*******************************************************
Hi jwt,
if you can't buy Mail-Order from the USA, can you from continental Europe, such as Italy ?
{or Holland or France ?}.
There is very limited available in the UK that is not physically too large to fit neatly on the circuit boards.
I'll write more about where to buy next time.
Though if you are re-wiring now, leave OUT the thick cable, especially from the mid and treble circuits !
It's probably OK in the bass circuits.
Can you Post photos of your crossovers ?
Like those attached to some earlier posts in this thread,
and/or Post a diagram of each crossover so that I can see the differences you are describing.
What is the model number of your Dynaudio mid-domes ?
Read the entire Thread through before you buy anything or spend a lot of time changing things.
I'll comment on your other points next time.
Last edited:
Hi alan-1-b
I disconnected an l-pad and measured the resistances across the 3 pins with the wiper at the point where I prefered listening. I hope that's what you meant as there is no other point on the l-pad where I get a reading.
I don't understand the results I got from an 8 ohm L-pad, but here they are.
Pin 1 - 2, 40 ohm
Pin 1 - 3, 40 ohm
Pin 2 -3, 1 ohm
I checked the meter across the bass terminals and got the expected 6 ohms.
Aside from that, I'd ditch the L-pads if I could restore the original tonal balance. I still think I'm losing out on bass extension, although the L-pads do let me compensate comparative gain loss. I wish I'd discovered this forum before I'd started...
I disconnected an l-pad and measured the resistances across the 3 pins with the wiper at the point where I prefered listening. I hope that's what you meant as there is no other point on the l-pad where I get a reading.
I don't understand the results I got from an 8 ohm L-pad, but here they are.
Pin 1 - 2, 40 ohm
Pin 1 - 3, 40 ohm
Pin 2 -3, 1 ohm
I checked the meter across the bass terminals and got the expected 6 ohms.
Aside from that, I'd ditch the L-pads if I could restore the original tonal balance. I still think I'm losing out on bass extension, although the L-pads do let me compensate comparative gain loss. I wish I'd discovered this forum before I'd started...
Last edited:
L-pads, and modifications to the circuit.
How many variations of circuits suitable for L-pads there are I do not know,
however there are 2 basic types:-
(1) a single track of resistive element connected as a Potentiometer
with an electrical connection to each end of the resistive element and a connection to a sliding point which makes contact with the resistive element.
(2) two separate tracks of resistive element with an electrical connection to one end of one element
and a separate electrical connection to the opposite end of the other element.
The third electrical connection is to the sliding contact point, which in this type is TWO internal contact points - one to each resistive element - both move when the knob is turned.
The advantage of this type is that two different Resistances for the elements can be used, and thus it can be configured as what is named a Constant Impedance L-pad,
actually its Constant Resistance and the Impedance does change when its connected to most types of speakers because most speaker drivers have an Impedance which varies with Frequency, however it is closer to Constant Impedance than can be achieved with a single element L-pad.
It seems from the resistances that dloper has posted that the type he has is single resistive element.
It is Specified as 8 ohm because it is intended to be used with an 8 ohm nominal impedance driver.
It's actual resistance needs to be at least 5 times higher than the nominal impedance of the driver so that when it is mostly in electrical Parallel connection with the driver the total impedance presented to the amplifier is only a little less than 8 ohms.
This type can work OK with most Solid State amplifiers, but for use with most types of Tube amplifiers a dual-element, Constant Impedance type should be used, and yes, those are more expensive, usually more than twice the price if a good quality one.
**********************************************************
ELECTRICALLY CONNECTING AN L-PAD
It seems from dloper's description that he MAY have his L-pads connected
back-to-front ... though I am not sure.
The correct electrical connection, for SAFETY of the amplifier, and for as close as can be got to constant impedance is:-
One of the end terminal connections connected to Ground/Earth, or -ive rail of the cross-over, or speaker -ive point.
The other end terminal connection connected to the Amplifier's +ive speaker terminal.
The middle, sliding terminal connection connected to the Speaker driver, or the +ive terminal of the cross-over input for dloper's case where he is using a single L-pad to attenuate two drivers.
If the centre, sliding connection is made to the Amplifier then when it is turned fully OFF there will be a SHORT CIRCUIT across the amplifier's output !
Even when it is not fully OFF, but only turned down a little, its lower Parallel resistance then will prevent the amplifier from delivering the maximum voltage swing of the signal, and thus the dynamics of the sound will be reduced,
not only the volume level one wants reduced.
Also, this lower parallel resistance will cause a shift of the cross over points, thus change the Tone to some degree.
If dloper has this back-to-front connection he may be hearing some of these effects even though he only sets his centre knob down a very little,
{which his reported measurements indicate}.
Even when connected correctly there is still, in dloper's case, 40 ohms in electrical parallel with the ENTIRE 66 loudspeaker,
because he has the pad across the Input to the cross-over,
because he is attenuating 2 drivers with a single L-pad.
{the 3rd pad connection causes only those 2 drivers to reduce in volume}
This total parallel connection will affect the Transient Response of the entire loudspeaker,
and mostly in the case of the 66, given that its type of bass-loading is reflected back into its electrical impedance, it will be affecting the transient response of the bass more so than the mids and treble.
Fortunately dloper can audibly identify this distinction, thus I think he will be able to hear the benefits of a better type of connection for L-pad,
and for some other modifications later.
With reference to the Part Numbers of the T.B.C. schematic:-
the 6 ohms resistance reading dloper got when measuring across the L-pad when connected to the cross-over is in fact the total resistance of the 40 ohm potentiometer in electrical parallel with the series resistance path of
L3 + L2 + the DC resistance of the bass driver.
{the capacitors at the inputs to the mid and treble sections of the cross-over block the meter from including resistive paths through the mid-dome, tweeter, and their associated Inductors in the cross-over}.
dloper, try this connection for your L-pads:-
Connect one end to -ive, as you have it at the end of L1 will be OK,
as long as that is basically a zero resistance path to the -ive terminal connection of the mid-driver.
Connect the other end to the junction point of L4 and C3 -{T.B.C. schematic}.
Disconnect the mid-driver +ive from this L4/C3 junction and connect the mid-driver +ive to the middle slider terminal of the L-pad.
Yes, now it will only attenuate signal to the mid-driver,
however whilst you are doing that, completely REMOVE the new small CPA 0U68 J450 capacitor from the board.
That will reduce the tweeter volume a little,
though this is not the ideal way to do it,
and later, after you have decided on an L-pad setting for the midrange,
I will be advising resistor values to connect,
and you can then insert either 0.47 or 0.5 ohm in electrical Series with the remaining CPA 5U6 J400 capacitor - that will shift back the cross over frequency correctly as well as maintaining the small volume level attenuation to the tweeter.
A resistor in Series instead of the L-pad will work better for the midrange attenuation, AND will allow for removal of the CPA 2u2 J400 capacitor not affecting the correct cross over frequency.
Remove the CPA 2u2 J400 now also, so that when you decide the L-pad setting by listening, and then measure its resistance from Pin 2 to each end, I can estimate the optimum resistor size to insert there.
Later a resistor will have to be added in electrical series with C3 to simulate the ESR of the original so as to restore the correct slope of the cross-over filter there, but for now you will be able to get a bit closer to a sound you like,
I hope ...
The above will not entirely restore the original transient response of the bass,
because Wilmslow put 80uF caps in the filter instead of 72uF,
however with a small resistor in electrical series with each of those caps they can be made to simulate 72uF closely enough for their particular functions in that circuit,
OR, if you are going to be adding resistors there, would you prefer to change from those 80uF caps ?
There are small size 72uF electrolytic caps available, but if I was changing caps there I would install polypropylene caps because they will last forever, however they will need ESR simulating resistors added.
How much space is there to neatly fit resistors on your boards for all the positions I have described ?
And, how far towards trying to achieve an Ideal do you want to go ?
Post and descibe the sound after you have done the L-pad and capacitor changes.
How many variations of circuits suitable for L-pads there are I do not know,
however there are 2 basic types:-
(1) a single track of resistive element connected as a Potentiometer
with an electrical connection to each end of the resistive element and a connection to a sliding point which makes contact with the resistive element.
(2) two separate tracks of resistive element with an electrical connection to one end of one element
and a separate electrical connection to the opposite end of the other element.
The third electrical connection is to the sliding contact point, which in this type is TWO internal contact points - one to each resistive element - both move when the knob is turned.
The advantage of this type is that two different Resistances for the elements can be used, and thus it can be configured as what is named a Constant Impedance L-pad,
actually its Constant Resistance and the Impedance does change when its connected to most types of speakers because most speaker drivers have an Impedance which varies with Frequency, however it is closer to Constant Impedance than can be achieved with a single element L-pad.
It seems from the resistances that dloper has posted that the type he has is single resistive element.
It is Specified as 8 ohm because it is intended to be used with an 8 ohm nominal impedance driver.
It's actual resistance needs to be at least 5 times higher than the nominal impedance of the driver so that when it is mostly in electrical Parallel connection with the driver the total impedance presented to the amplifier is only a little less than 8 ohms.
This type can work OK with most Solid State amplifiers, but for use with most types of Tube amplifiers a dual-element, Constant Impedance type should be used, and yes, those are more expensive, usually more than twice the price if a good quality one.
**********************************************************
ELECTRICALLY CONNECTING AN L-PAD
It seems from dloper's description that he MAY have his L-pads connected
back-to-front ... though I am not sure.
The correct electrical connection, for SAFETY of the amplifier, and for as close as can be got to constant impedance is:-
One of the end terminal connections connected to Ground/Earth, or -ive rail of the cross-over, or speaker -ive point.
The other end terminal connection connected to the Amplifier's +ive speaker terminal.
The middle, sliding terminal connection connected to the Speaker driver, or the +ive terminal of the cross-over input for dloper's case where he is using a single L-pad to attenuate two drivers.
If the centre, sliding connection is made to the Amplifier then when it is turned fully OFF there will be a SHORT CIRCUIT across the amplifier's output !
Even when it is not fully OFF, but only turned down a little, its lower Parallel resistance then will prevent the amplifier from delivering the maximum voltage swing of the signal, and thus the dynamics of the sound will be reduced,
not only the volume level one wants reduced.
Also, this lower parallel resistance will cause a shift of the cross over points, thus change the Tone to some degree.
If dloper has this back-to-front connection he may be hearing some of these effects even though he only sets his centre knob down a very little,
{which his reported measurements indicate}.
Even when connected correctly there is still, in dloper's case, 40 ohms in electrical parallel with the ENTIRE 66 loudspeaker,
because he has the pad across the Input to the cross-over,
because he is attenuating 2 drivers with a single L-pad.
{the 3rd pad connection causes only those 2 drivers to reduce in volume}
This total parallel connection will affect the Transient Response of the entire loudspeaker,
and mostly in the case of the 66, given that its type of bass-loading is reflected back into its electrical impedance, it will be affecting the transient response of the bass more so than the mids and treble.
Fortunately dloper can audibly identify this distinction, thus I think he will be able to hear the benefits of a better type of connection for L-pad,
and for some other modifications later.
With reference to the Part Numbers of the T.B.C. schematic:-
the 6 ohms resistance reading dloper got when measuring across the L-pad when connected to the cross-over is in fact the total resistance of the 40 ohm potentiometer in electrical parallel with the series resistance path of
L3 + L2 + the DC resistance of the bass driver.
{the capacitors at the inputs to the mid and treble sections of the cross-over block the meter from including resistive paths through the mid-dome, tweeter, and their associated Inductors in the cross-over}.
dloper, try this connection for your L-pads:-
Connect one end to -ive, as you have it at the end of L1 will be OK,
as long as that is basically a zero resistance path to the -ive terminal connection of the mid-driver.
Connect the other end to the junction point of L4 and C3 -{T.B.C. schematic}.
Disconnect the mid-driver +ive from this L4/C3 junction and connect the mid-driver +ive to the middle slider terminal of the L-pad.
Yes, now it will only attenuate signal to the mid-driver,
however whilst you are doing that, completely REMOVE the new small CPA 0U68 J450 capacitor from the board.
That will reduce the tweeter volume a little,
though this is not the ideal way to do it,
and later, after you have decided on an L-pad setting for the midrange,
I will be advising resistor values to connect,
and you can then insert either 0.47 or 0.5 ohm in electrical Series with the remaining CPA 5U6 J400 capacitor - that will shift back the cross over frequency correctly as well as maintaining the small volume level attenuation to the tweeter.
A resistor in Series instead of the L-pad will work better for the midrange attenuation, AND will allow for removal of the CPA 2u2 J400 capacitor not affecting the correct cross over frequency.
Remove the CPA 2u2 J400 now also, so that when you decide the L-pad setting by listening, and then measure its resistance from Pin 2 to each end, I can estimate the optimum resistor size to insert there.
Later a resistor will have to be added in electrical series with C3 to simulate the ESR of the original so as to restore the correct slope of the cross-over filter there, but for now you will be able to get a bit closer to a sound you like,
I hope ...
The above will not entirely restore the original transient response of the bass,
because Wilmslow put 80uF caps in the filter instead of 72uF,
however with a small resistor in electrical series with each of those caps they can be made to simulate 72uF closely enough for their particular functions in that circuit,
OR, if you are going to be adding resistors there, would you prefer to change from those 80uF caps ?
There are small size 72uF electrolytic caps available, but if I was changing caps there I would install polypropylene caps because they will last forever, however they will need ESR simulating resistors added.
How much space is there to neatly fit resistors on your boards for all the positions I have described ?
And, how far towards trying to achieve an Ideal do you want to go ?
Post and descibe the sound after you have done the L-pad and capacitor changes.
Last edited:
Hi alan-1-b
I'm confident I've got the L-pads wired correctly, if not optimally. The spec for the L-pads can be seen at http://www.public-adress.fr/pr-562/...eur-a-impedance-constante-Monacor-AT-62H.html
I've got them wired on the other side of the bass xover, with pin 3 after L3, Pin 2 before C4 and Pin 1 going to the -ve rail between the -ve connection to the bass driver and L1.
Pins 3 to 2 are wired in series with the original connection between L3 and C4 broken.
After originally installing the L-pads, I powered up the amp with the wiper in the middle. I tried carefully sweeping it both ways fully, and there was no ill effect to the amp.
Anyway, I'm away for a few days, but will try the suggested mods on my return. I would like to squeeze everything possible from my 66s, so I'm quite happy to try anything. I'm also going to rebuild the crossovers once I've got them sounding at their best.Thanks again.
I'm confident I've got the L-pads wired correctly, if not optimally. The spec for the L-pads can be seen at http://www.public-adress.fr/pr-562/...eur-a-impedance-constante-Monacor-AT-62H.html
I've got them wired on the other side of the bass xover, with pin 3 after L3, Pin 2 before C4 and Pin 1 going to the -ve rail between the -ve connection to the bass driver and L1.
Pins 3 to 2 are wired in series with the original connection between L3 and C4 broken.
After originally installing the L-pads, I powered up the amp with the wiper in the middle. I tried carefully sweeping it both ways fully, and there was no ill effect to the amp.
Anyway, I'm away for a few days, but will try the suggested mods on my return. I would like to squeeze everything possible from my 66s, so I'm quite happy to try anything. I'm also going to rebuild the crossovers once I've got them sounding at their best.Thanks again.
the Monacor AT-62H L-pad
It is good that Monacor provide a schematic with connection indications,
so that users can install the L-pad correctly.
That schematic is of a two tracks', potentially Constant Impedance {Constant Resistance}, L-pad.
If it is actually "Constant" when connected to a near to 8 ohm driver, then when you have it disconnected next,
measure between pins 3 and 2 for each end setting of the wiper, and between pins 2 and 1 for each end of the wiper's setting.
3 <---> 2 should give close to 8 ohm and close to 0 ohm.
2 <---> 1 , in the case of your sample it seems gives 40 ohm and likely close to 0 ohm.
Ideally for "constant" would be for the 2 <---> 1 to have about 50 ohm for its Maximum, though some types may be as high as 100 ohm,
and 40 ohm is OK for your application,
and that is just within the Monacor specification of -20% {wrt 50 ohm}.
If the 3 <---> 2 Maximum is a lot larger than 8 ohm the L-pad is not an 8 ohm constant type.
An 8 ohm "constant" L-pad is only close to "constant" when connected as shown in the Monacor schematic to an approximately 8 ohm driver.
When measured 3 <---> 1 when connected to such driver it will never be less than close to 8 ohm,
and thus the amplifier will always see a safe load with all settings of the wiper.
If the driver is disconnected, the amplifier will see a load between 8 ohms and the Maximum of 2 <---> 1, depending on the wiper position.
Even connected as you describe dloper, the L-pad is electrically in Parallel with the bass circuit in the manner I described in my previous Post,
and thus why it affects the entire bass-circuit performance.
Post your audible impressions after you have listened awhile to the changes I recommended,
and then we can discuss what you may prefer to do next.
**************************************************
Address me simply as Alan - its quicker and easier to type,
and there has been no other Alan contributing to this Thread to date -
{any out there ?} - {and where is rwtomkins ? - perhaps enjoying a well-earned rest after recent Thread Duty !}
It is good that Monacor provide a schematic with connection indications,
so that users can install the L-pad correctly.
That schematic is of a two tracks', potentially Constant Impedance {Constant Resistance}, L-pad.
If it is actually "Constant" when connected to a near to 8 ohm driver, then when you have it disconnected next,
measure between pins 3 and 2 for each end setting of the wiper, and between pins 2 and 1 for each end of the wiper's setting.
3 <---> 2 should give close to 8 ohm and close to 0 ohm.
2 <---> 1 , in the case of your sample it seems gives 40 ohm and likely close to 0 ohm.
Ideally for "constant" would be for the 2 <---> 1 to have about 50 ohm for its Maximum, though some types may be as high as 100 ohm,
and 40 ohm is OK for your application,
and that is just within the Monacor specification of -20% {wrt 50 ohm}.
If the 3 <---> 2 Maximum is a lot larger than 8 ohm the L-pad is not an 8 ohm constant type.
An 8 ohm "constant" L-pad is only close to "constant" when connected as shown in the Monacor schematic to an approximately 8 ohm driver.
When measured 3 <---> 1 when connected to such driver it will never be less than close to 8 ohm,
and thus the amplifier will always see a safe load with all settings of the wiper.
If the driver is disconnected, the amplifier will see a load between 8 ohms and the Maximum of 2 <---> 1, depending on the wiper position.
Even connected as you describe dloper, the L-pad is electrically in Parallel with the bass circuit in the manner I described in my previous Post,
and thus why it affects the entire bass-circuit performance.
Post your audible impressions after you have listened awhile to the changes I recommended,
and then we can discuss what you may prefer to do next.
**************************************************
Address me simply as Alan - its quicker and easier to type,
and there has been no other Alan contributing to this Thread to date -
{any out there ?} - {and where is rwtomkins ? - perhaps enjoying a well-earned rest after recent Thread Duty !}
Last edited:
Hi Alan - I've been away for a wee while. Anyway, I had a look at my crossovers again, and with the mods I've made with the L-pads and bi-wiring, I've got myself a little confused with the circuit diagram. I don't want to take any electrical chances with amp or speakers, so I think I'd better rebuild the crossovers completely to make sure I don't destroy anything. I hope you can bear with me for a week or two until I get sorted out.
Plan ahead
Hi dloper,
there will likely be an amount of other modifying yet to do,
such as installing ESR simulating resistors which will need additional spacing,
before you get a result you are completely happy with,
thus I recommend you do not do too much work that you may have to REPEAT later !
Simplest is to re-connect the L-pads in the way I suggested,
and remove the 2 unneccessary small value capacitors from each board.
Those capacitors removed cannot cause any damage to either the speakers or the amplifier,
nor can the L-pad when connected as I described.
Don't worry too much, but only be careful when making soldering joints to ensure that all connections will conduct electricity.
Hi dloper,
there will likely be an amount of other modifying yet to do,
such as installing ESR simulating resistors which will need additional spacing,
before you get a result you are completely happy with,
thus I recommend you do not do too much work that you may have to REPEAT later !
Simplest is to re-connect the L-pads in the way I suggested,
and remove the 2 unneccessary small value capacitors from each board.
Those capacitors removed cannot cause any damage to either the speakers or the amplifier,
nor can the L-pad when connected as I described.
Don't worry too much, but only be careful when making soldering joints to ensure that all connections will conduct electricity.
Hi Alan - I made the mods you mentioned last night, so I'll get back to you when I've listened a bit more.
First impressions are good. I didn't notice any obvious difference in the bass, but various parts of the room are now buzzing and rattling, which I didn't notice before. The treble actually seems better defined now. Guitar and percussive notes are sharper (in a good way!). With a little attenuation on the mid, voices can reach loud and high peaks with no sense of strain. I thought the attenuation might place voices further back in the mix, but they can still hang in the air quite dramatically.
First impressions are good. I didn't notice any obvious difference in the bass, but various parts of the room are now buzzing and rattling, which I didn't notice before. The treble actually seems better defined now. Guitar and percussive notes are sharper (in a good way!). With a little attenuation on the mid, voices can reach loud and high peaks with no sense of strain. I thought the attenuation might place voices further back in the mix, but they can still hang in the air quite dramatically.
Hello again Alan -
I’ve spent a while listening to a wide variety of music now and I even fixed the rattling cupboards.
After reading my first impressions again, I’d say that the bass has improved. It’s easier to follow bass lines now, especially where there are several things going on at once; they seem better differentiated, more interesting and more fun. My partner, who has little interest in hi-fi apart from enjoying excellence and who tolerates my hobby with aloof dignity, listened tonight and felt that the bass, whilst better, still lacks a bit of extension. I’d agree with that. It sounds great, but not quite a ’66.
The treble also, as per my first impression, is better defined. Spitty sibilance is not an issue, even on some of my more ’difficult’ discs where vocals can be distracting. King Crimsons Red is the only HD CD I have, and the percussion on that is much easier to follow. I find that Red is a very difficult test. There is so much going on it’s easy to trip up a system, but the treble copes without a problem. My partner also noticed the improvement. She hates King Crimson, so I played her some Bjork, Debut.
The same applies to the mid-range, which I’m running with a little attenuation. Vocalists can sing as loudly and passionately as they like without strain. Hard vocals or any ringing, annoying instruments are a particular bugbear of mine. I find that the over accenting of portions of the mid-range, whether it’s a speaker or room issue, tires me out and blurs my perception of everything else that is going on. The mid-range doesn’t suffer from any of that but on the other hand I think perhaps there is a little ‘excitement’ missing. And no, reducing the attenuation doesn’t seem to help. There is what I’d describe as a slight lack of lifelike texture to some instruments and voices.
Overall, a worthwhile improvement and a system that is more fun to listen to. Whilst it was difficult to pick fault previously, I’d say now that it did sound a little bland. What I’d like to see now would be a little more dynamics in the mid-range and a little more extension to the bass. If there is anything more to be had from the tweeter, even better.
It’s very difficult to write one’s impressions of a component without sounding like a plagiarising hi-fi hack (a stereotype?), so I hope you can follow my impressions. I’m still playing with the L-pads, within a narrow range, so I might take a wee while to finally decide my ideal. Thanks for your patience and info.
I’ve spent a while listening to a wide variety of music now and I even fixed the rattling cupboards.
After reading my first impressions again, I’d say that the bass has improved. It’s easier to follow bass lines now, especially where there are several things going on at once; they seem better differentiated, more interesting and more fun. My partner, who has little interest in hi-fi apart from enjoying excellence and who tolerates my hobby with aloof dignity, listened tonight and felt that the bass, whilst better, still lacks a bit of extension. I’d agree with that. It sounds great, but not quite a ’66.
The treble also, as per my first impression, is better defined. Spitty sibilance is not an issue, even on some of my more ’difficult’ discs where vocals can be distracting. King Crimsons Red is the only HD CD I have, and the percussion on that is much easier to follow. I find that Red is a very difficult test. There is so much going on it’s easy to trip up a system, but the treble copes without a problem. My partner also noticed the improvement. She hates King Crimson, so I played her some Bjork, Debut.
The same applies to the mid-range, which I’m running with a little attenuation. Vocalists can sing as loudly and passionately as they like without strain. Hard vocals or any ringing, annoying instruments are a particular bugbear of mine. I find that the over accenting of portions of the mid-range, whether it’s a speaker or room issue, tires me out and blurs my perception of everything else that is going on. The mid-range doesn’t suffer from any of that but on the other hand I think perhaps there is a little ‘excitement’ missing. And no, reducing the attenuation doesn’t seem to help. There is what I’d describe as a slight lack of lifelike texture to some instruments and voices.
Overall, a worthwhile improvement and a system that is more fun to listen to. Whilst it was difficult to pick fault previously, I’d say now that it did sound a little bland. What I’d like to see now would be a little more dynamics in the mid-range and a little more extension to the bass. If there is anything more to be had from the tweeter, even better.
It’s very difficult to write one’s impressions of a component without sounding like a plagiarising hi-fi hack (a stereotype?), so I hope you can follow my impressions. I’m still playing with the L-pads, within a narrow range, so I might take a wee while to finally decide my ideal. Thanks for your patience and info.
Next step
Don't worry about sounding like a "hi-fi hack" - you have given a good description, which I hope I am understanding correctly ...
But first, King Crimson's "Red" - I haven't heard that for many years,
but do remember liking some of it, and it has not recently come into my mind when buying, but soon could be as good as ever ... !
Which is the version to buy for good sound, but not at the cost of excess audio processing diminishing some qualities of the performance ?
The standard CD ? ; the 40th Anniversary CD set ? ; the Japanese manufactured CD ?
OK, maybe I should go and steal the original vinyl LP from the owner I gave it to as a gift years ago !!
The last K.Crimson album I listened to was "USA", which I have the vinyl LP of, and like some of it a lot !
I think I liked some of "Starless And Bible Black" , but have forgotten ...
ahem, now maybe your have dismissed me altogether ...
******************************************
Keep in mind that whenever ONE frequency band in a multiway speaker is changed, the other frequency band(s) seem different also -
this is a Psychoacoustic effect created in the brain, and is difficult to hear past,
however, with some experience, and careful sequential listening, one can attribute some audible phenonema to specific parts of the circuit.
You will NEVER get the exact same bass response that you remember,
unless you can find good condition, working samples of ALL the original capacitors, which you won't ...
however we can get closer than you are now.
Those 80uF caps in the bass filter are rolling off the upper-bass response too steeply, and that does affect one's perception of the lower bass also -{as above}.
Rarely are electrolytic caps the exact value printed on them, and more often they measure a bit larger, but old 72uF + larger is still less than 80uF + larger.
There is one source of 72uF audio crossover suitable electros available,
if you want to try for possible authenticity, but I don't recommend that, because they will still have limited lifespan ...
and I think it better to keep the 80uFs in circuit and try to trick them into behaving like 72uF, which can be done with a small value resistor connected in Series with each,
AND, for those resistors you can use the same resistance as I would use to simulate the ESR of the old 72uF caps when replacing with polypropylene caps,
thus you can keep the resistors in-circuit and install polyprop's later if you decide to, and have no limit to service life.
Which option do you want to do ?
Also, the upper mids are being filtered off too steeply by the 4uF polypropylene cap in parallel with the mid-dome, because the original electro there
had some series resistance also, thus if you add a series resistor there as if it is part of the cap you will likely restore the "excitement".
Also, a very small resistor, about 0.5ohm, connected in series with the 5u6 cap in the treble filter will increase the Impedance sufficiently for the treble cross-over point to be returned to where it was with 6uF cap there originally,
AND that resistance is so small it will not noticeably attenuate the treble output, but can better balance the treble and mid audio characteristics.
Adding the small parallel cap to the 5u6 to try to simulate 6uF does NOT work with music.
It creates a Sound Effect, and which some listeners like and others hate, because it changes the Transient Response of the signal.
Adding capacitors in Parallel is valid for increasing the amount of Charge{Energy} that can be stored, and that is for Power Supply use , etc ...
but rapidly fluctuating, multi-frequency music signals are NOT simple energy store&release functions.
You could install a new 6uF or 6u2 or a parallel pair of 3uF caps there, but as you seem to like the basic sound with the 5u6 there,
lets leave it there for now and install a small resistor whilst you are installing the other resistors.
When resistors are installed in all the locations I've described, then you listen again and fine-tune the L-pad for mids' balance.
After that you can measure the L-pad's pin 2 resistance to both 1 and 3, and Post and I will estimate a suitable resistor for there,
or simply keep the L-pad in circuit,
but you will need to hear with the other resistors installed to be able to knowledgeably decide.
Are your cross-over boards the old directly wired type with plenty of space around the components - so as to be able to fit resistors in fairly easily -
or are they the later hole-through, PCB type boards which have less space to work around ?
Suitable resistors can all be bought in the UK if you can buy Mail Order from Farnell.
What do you prefer to do now ?
Don't worry about sounding like a "hi-fi hack" - you have given a good description, which I hope I am understanding correctly ...
But first, King Crimson's "Red" - I haven't heard that for many years,
but do remember liking some of it, and it has not recently come into my mind when buying, but soon could be as good as ever ... !
Which is the version to buy for good sound, but not at the cost of excess audio processing diminishing some qualities of the performance ?
The standard CD ? ; the 40th Anniversary CD set ? ; the Japanese manufactured CD ?
OK, maybe I should go and steal the original vinyl LP from the owner I gave it to as a gift years ago !!
The last K.Crimson album I listened to was "USA", which I have the vinyl LP of, and like some of it a lot !
I think I liked some of "Starless And Bible Black" , but have forgotten ...
ahem, now maybe your have dismissed me altogether ...
******************************************
Keep in mind that whenever ONE frequency band in a multiway speaker is changed, the other frequency band(s) seem different also -
this is a Psychoacoustic effect created in the brain, and is difficult to hear past,
however, with some experience, and careful sequential listening, one can attribute some audible phenonema to specific parts of the circuit.
You will NEVER get the exact same bass response that you remember,
unless you can find good condition, working samples of ALL the original capacitors, which you won't ...
however we can get closer than you are now.
Those 80uF caps in the bass filter are rolling off the upper-bass response too steeply, and that does affect one's perception of the lower bass also -{as above}.
Rarely are electrolytic caps the exact value printed on them, and more often they measure a bit larger, but old 72uF + larger is still less than 80uF + larger.
There is one source of 72uF audio crossover suitable electros available,
if you want to try for possible authenticity, but I don't recommend that, because they will still have limited lifespan ...
and I think it better to keep the 80uFs in circuit and try to trick them into behaving like 72uF, which can be done with a small value resistor connected in Series with each,
AND, for those resistors you can use the same resistance as I would use to simulate the ESR of the old 72uF caps when replacing with polypropylene caps,
thus you can keep the resistors in-circuit and install polyprop's later if you decide to, and have no limit to service life.
Which option do you want to do ?
Also, the upper mids are being filtered off too steeply by the 4uF polypropylene cap in parallel with the mid-dome, because the original electro there
had some series resistance also, thus if you add a series resistor there as if it is part of the cap you will likely restore the "excitement".
Also, a very small resistor, about 0.5ohm, connected in series with the 5u6 cap in the treble filter will increase the Impedance sufficiently for the treble cross-over point to be returned to where it was with 6uF cap there originally,
AND that resistance is so small it will not noticeably attenuate the treble output, but can better balance the treble and mid audio characteristics.
Adding the small parallel cap to the 5u6 to try to simulate 6uF does NOT work with music.
It creates a Sound Effect, and which some listeners like and others hate, because it changes the Transient Response of the signal.
Adding capacitors in Parallel is valid for increasing the amount of Charge{Energy} that can be stored, and that is for Power Supply use , etc ...
but rapidly fluctuating, multi-frequency music signals are NOT simple energy store&release functions.
You could install a new 6uF or 6u2 or a parallel pair of 3uF caps there, but as you seem to like the basic sound with the 5u6 there,
lets leave it there for now and install a small resistor whilst you are installing the other resistors.
When resistors are installed in all the locations I've described, then you listen again and fine-tune the L-pad for mids' balance.
After that you can measure the L-pad's pin 2 resistance to both 1 and 3, and Post and I will estimate a suitable resistor for there,
or simply keep the L-pad in circuit,
but you will need to hear with the other resistors installed to be able to knowledgeably decide.
Are your cross-over boards the old directly wired type with plenty of space around the components - so as to be able to fit resistors in fairly easily -
or are they the later hole-through, PCB type boards which have less space to work around ?
Suitable resistors can all be bought in the UK if you can buy Mail Order from Farnell.
What do you prefer to do now ?
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Hi Alan - I don't know many people who appreciate King Crimson -an acquired taste I think. My CD player includes HDCD decoding and the version of Red I have is a 24 bit HDCD remaster 30th anniversary edition. I haven't compared it with any others. One copy in the house is more than enough as far as my partner is concerned. If I had the choice it would still be on vinyl. Unfortunately I sold the lot in the early eighties, including my original Ditton 66s, to buy a hang glider.
Anyway, I've already rebuilt the crossovers on slightly larger boards from the original TBC board and I did away with the bi-wiring option meantime to keep things simpler for myself. I've left space to allow for any further mods, so I'm quite happy to add some series resistors, which is the mod I'd like to try first. I'd appreciate some recommendations on sizes and voltages. This is an uneducated question, but does it make a difference if I put the resistors in before or after the caps, relative to the +ve rail?
Anyway, I've already rebuilt the crossovers on slightly larger boards from the original TBC board and I did away with the bi-wiring option meantime to keep things simpler for myself. I've left space to allow for any further mods, so I'm quite happy to add some series resistors, which is the mod I'd like to try first. I'd appreciate some recommendations on sizes and voltages. This is an uneducated question, but does it make a difference if I put the resistors in before or after the caps, relative to the +ve rail?
correcting a mistake, plus a Buying question.
Ooops, despite Proof-reading my Post, it still has one slip !
I should have written:-
"those 80uF caps in the bass filter are rolling off the lower-midrange response too steeply, and that does affect ... etc ... "
*******************************************************
Can you buy Mail-order from Farnell ?
All the necessary resistors are listed in their on-line catalog,
but if you cannot buy from there I'll try to find another source, but it may be from USA,
unless you will buy from two separate sources and/or accept less suitable types of resistors.
Most are cheap - around 30p. , but one is about 3.55 - double for two speakers, {and no cheaper elsewhere in the UK}.
If you don't want a 3.55 x two resistor(s) then I'll list a cheap one,
but it won't work as well - it's for the tweeter circuit.
Look at:- Farnell / Electronic Component Distributors / Suppliers / Electronics, Electrical Parts, Electrical Components and Wholesale Electronics.
and go to their UK page, and check all their Sales Conditions, such as Payment modes accepted, and whether there is any Minimum Price Order,
or Minimum number of Items order. {I always buy a lot of things on any single occasion.}
Electrical circuit placing I'll mention later, and I doubt it will be any problem.
*******************************************************
HDCD - well, it seems to be being phased out, and not available on most
-{if any}- new models of players, and its not in my not-so-old Marantz Special Edition -{modified}- player ...
so I don't have a reason to steal anyone's 30th Anniversary issue,
nor buy one at what may be an exhorbitant price from who-ever selling !
I'll look for what else interesting for "Red" that may be available.
Hang-gliding ... and you're still alive ! -{too much King Crimson !!}-
-{the fellow I gave "Red" to as a gift was into underwater deep diving, and he was a K.Crimson enthusiast}.
Ooops, despite Proof-reading my Post, it still has one slip !
I should have written:-
"those 80uF caps in the bass filter are rolling off the lower-midrange response too steeply, and that does affect ... etc ... "
*******************************************************
Can you buy Mail-order from Farnell ?
All the necessary resistors are listed in their on-line catalog,
but if you cannot buy from there I'll try to find another source, but it may be from USA,
unless you will buy from two separate sources and/or accept less suitable types of resistors.
Most are cheap - around 30p. , but one is about 3.55 - double for two speakers, {and no cheaper elsewhere in the UK}.
If you don't want a 3.55 x two resistor(s) then I'll list a cheap one,
but it won't work as well - it's for the tweeter circuit.
Look at:- Farnell / Electronic Component Distributors / Suppliers / Electronics, Electrical Parts, Electrical Components and Wholesale Electronics.
and go to their UK page, and check all their Sales Conditions, such as Payment modes accepted, and whether there is any Minimum Price Order,
or Minimum number of Items order. {I always buy a lot of things on any single occasion.}
Electrical circuit placing I'll mention later, and I doubt it will be any problem.
*******************************************************
HDCD - well, it seems to be being phased out, and not available on most
-{if any}- new models of players, and its not in my not-so-old Marantz Special Edition -{modified}- player ...
so I don't have a reason to steal anyone's 30th Anniversary issue,
nor buy one at what may be an exhorbitant price from who-ever selling !
I'll look for what else interesting for "Red" that may be available.
Hang-gliding ... and you're still alive ! -{too much King Crimson !!}-
-{the fellow I gave "Red" to as a gift was into underwater deep diving, and he was a K.Crimson enthusiast}.
Last edited:
Hi DIY Audio, i am a new member of this forum...but i do own a pair of the original Celestion Ditton 66 Sudio Monitors....Looking at this lovely long thread..i can tell, i have the first generation speakers...black faced........inside the coils are visable in cross over and you can see caps where changed to the green type..coupled up to make variuos uf's......well my beloved monitors have started playing up..... One tweeter has cut out......after checking...i noticed that the caps on crossover has died....Hf2000 needs replacing to.....oh dear.....so glad wiilslow audio has a shop on ebay.......but the struggle continues find to find a pair of tweeters if im so lucky....lol...start playing my AR 9's but would love to find a original tweeter.....for celestion 66's....oh people of the thread hear my cry.......
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Hi P.T.R.D. Are you sure the tweeter has died, and isn't just playing possum by being attached to dead caps? Ebay would be your best bet for HF2000s but they go for well over a hundred quid the pair. As for your caps, pay heed to alan-1-b. I replaced mine without knowing about this thread and I've got a bit of remedial work to do now, trying to restore the sound to something approaching the original concept.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hi Alan - I had a look at Farnells web site and it looks like I'll be able to order stuff with a credit card. I don't mind spending a few quid on parts that will work well. Once I'm done, I'll post a copy of the circuit diagram which hopefully will assist others. I do want to get back to the original sound as far as possible, so I hope the purists out there will understand that I don't want to be tinkering but the original sound was already lost to degrading components.
Hang gliding? Dangerous? I don't know what you mean. Tried skydiving too. That was too exciting. Settled for a proper glider in the end. Sport where you can sit down suits me.
Stuart
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hi Alan - I had a look at Farnells web site and it looks like I'll be able to order stuff with a credit card. I don't mind spending a few quid on parts that will work well. Once I'm done, I'll post a copy of the circuit diagram which hopefully will assist others. I do want to get back to the original sound as far as possible, so I hope the purists out there will understand that I don't want to be tinkering but the original sound was already lost to degrading components.
Hang gliding? Dangerous? I don't know what you mean. Tried skydiving too. That was too exciting. Settled for a proper glider in the end. Sport where you can sit down suits me.
Stuart
interim delay
Hello P.T.R.D.
be careful - what-ever you buy from Wilmslow you will have to be responsible for the sonic result -
- they do not seem to understand these old speakers well enough !
Read my earlier Posts, and I will return to this when time is available.
and hello Stuart/dloper,
I have very little spare time today and tomorow,
but I will get back to this when time is available.
Hello P.T.R.D.
be careful - what-ever you buy from Wilmslow you will have to be responsible for the sonic result -
- they do not seem to understand these old speakers well enough !
Read my earlier Posts, and I will return to this when time is available.
and hello Stuart/dloper,
I have very little spare time today and tomorow,
but I will get back to this when time is available.
Thank you Dioper/Alian-1-b...
I really love my celestion 66 Studio Monitors....checked tweeter is working but it sounds in bad shape....so i will look for a replacement/pair...oh lord.... playing my
AR 9's good speakers but really used to my celestions more....
Thanks everyone i have read all the threads, and i have learned so much about this great british speaker....I will keep intouch with the community and hopefully find the caps needed.......
Thanks
Diy Audio & Community
I really love my celestion 66 Studio Monitors....checked tweeter is working but it sounds in bad shape....so i will look for a replacement/pair...oh lord.... playing my
AR 9's good speakers but really used to my celestions more....
Thanks everyone i have read all the threads, and i have learned so much about this great british speaker....I will keep intouch with the community and hopefully find the caps needed.......
Thanks
Diy Audio & Community
Tweeters
Hello P.T.R.D.
to test your tweeter you will need to listen to it connected after a good working capacitor,
and NOT after any of those old capacitors in your 66s.
If you drive your tweeters from those old faulty caps the tweeters will become damaged !
Paying "well over a hundred quid the pair" for old HF2000s is NOT worth it !
Leave those expensive old HF2000s for Vintage-Collector type restorers.
For less money, better audio quality new SEAS HO737-08 , 19TFF1 tweeters can be used,
and those require only two resistors fitted to the 66 x-over to adapt for.
For low price, Coles CE 4001 tweeters will work OK, -{with resistors fitted}.
CE 4001 is very similar to HF2000.
I think that Coles may have made HF2000 for Celestion years ago.
Post here the Country or Nation that you are in, and I will Post where you can buy good new caps,
so you can try your HF2000, and then you can decide what to do next.
If, and only if, the sound from the tweeters in your AR 9s is clear - not distorted
- then try your HF2000 connected to the treble filter of the AR 9 x-over to hear how it sounds.
Try both HF2000s so that you can compare their sounds.
Post the result here.
Also, when you have the AR 9 open, have a look at the caps - if they are Electrolytic they should be replaced now,
because they are getting old and will become faulty.
Hello P.T.R.D.
to test your tweeter you will need to listen to it connected after a good working capacitor,
and NOT after any of those old capacitors in your 66s.
If you drive your tweeters from those old faulty caps the tweeters will become damaged !
Paying "well over a hundred quid the pair" for old HF2000s is NOT worth it !
Leave those expensive old HF2000s for Vintage-Collector type restorers.
For less money, better audio quality new SEAS HO737-08 , 19TFF1 tweeters can be used,
and those require only two resistors fitted to the 66 x-over to adapt for.
For low price, Coles CE 4001 tweeters will work OK, -{with resistors fitted}.
CE 4001 is very similar to HF2000.
I think that Coles may have made HF2000 for Celestion years ago.
Post here the Country or Nation that you are in, and I will Post where you can buy good new caps,
so you can try your HF2000, and then you can decide what to do next.
If, and only if, the sound from the tweeters in your AR 9s is clear - not distorted
- then try your HF2000 connected to the treble filter of the AR 9 x-over to hear how it sounds.
Try both HF2000s so that you can compare their sounds.
Post the result here.
Also, when you have the AR 9 open, have a look at the caps - if they are Electrolytic they should be replaced now,
because they are getting old and will become faulty.
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66 Mk1 - Blackie - bass <--> midrange crossover.
Such as listening to music !
-{ahmm, I do exercise outdoors every day}-
*********************************
I have mentioned applying the 66Mk2 x-over to Mk1 66 in a Post earlier in this Thread, because the older MF500 mid-dome is lower power capable than the later MD500,
thus if the x-over frequency to MF500 is raised a little the Mk1 66 can be played a bit louder.
This is part-relevant to what I will describe here now for dloper's case,
because he has a 25uF hi-pass filter cap to MF500 now instead of the original 30uF, and interim period 28uF, versions.
When only the cap is reduced a little, and the inductor is left as original,
the x frequency raises, but the filter's Slope is made a little less steep in the x-over region,
thus to combine optimally with the corresponding filter on the bass driver the bass filter should have its slope made a little less steep in the same region,
and maybe also raise its x frequency a little.
If you are restoring Mk1, I suggest trying a 68uF or a parallel pair of 33uF polypropylene caps for the C2 -{nearest to woofer}- ONLY,
and stay with 72uF for the C1, -{use 75uf poly or parallel 36uF pair or 33//39 or 30//40 - all are close enough to work well}.
With new Polypropylene caps, use the same value resistors for the ESR simulation as those I will list here for dloper to use to trick his 80uF electrocaps into behaving like 72uF and 68uF, - BUT NOTE :- this is a TRICK, and the 80uF caps are still 80uF,
thus do not buy 80uF caps -{unless you want whatever audible result dloper reports after he has tried this application}.
For the C1 position connect a 1 ohm wirewound, of not less than 4 watts rating,
in Series between the cap and the Ground/return connection.
For the C2 position connect a 1.5 ohm wirewound/minimum 4 watts,
in Series between the cap and Ground/return.
Stuart, for your 80uF electro application, larger than 1.5 ohm may be required with C2, but start with 1.5 and listen.
If you are not sufficiently satisfied then 2.2 or 2.7 or 3.3 or 3.9 ohms{maximum} can be tried later,
and we may be using the 1.5 ohm elsewhere then, depending on what you report as audible results.
The ESR simulating resistor to place in Series with the 25uF -{or 24uF}- new poly cap in the mids' filter will be decided after dloper had reported his L-pad settings following the other mods here.
For the 4uF, {or 3.9uF}, new poly cap in the mids' filter in the C3 position in parallel with the MF500,
connect a 3.9, or 4, ohm wirewound, minimum 4 watts rating, in Series between the cap and the Ground/return connection.
For buyers restricted to buying in UK, go to :-
Farnell / Electronic Component Distributors / Suppliers / Electronics, Electrical Parts, Electrical Components and Wholesale Electronics.
and to their UK site, and their Passive Components' Fixed Resistors' page.
Slide across the page to the Manufacturers' column in the Search box and select "Welwyn", the click on "Apply/Show Results".
Next, slide back to the "Series" and select their WP-S series, and then WP4S.
These are a 4 watt @ 25*C rated, enhanced pulse handling capacity resistor, thus will likely be very well assembled,
hence have little or none of the mechanical effects in them which can affect resistors sound quality.
Use these for the 1 ohm, 1.5 ohm, 3.9 ohm.
If there is no stock, then Welwyn's basic W series will work OK, use their W22, or higher number, series,
and remember that most wirewound resistors are rated at 25 degrees C, and not 70 degrees C like film resistors,
thus must be of sufficient power rating to be able to stay cool inside a loudspeaker enclosure.
When a resistor heats up, and particually if it fluctuates in temperature during operation, the sound will be affected.
Hot resistors work OK in Power Supplies, but not in audio signal paths.
Such as listening to music !
-{ahmm, I do exercise outdoors every day}-
*********************************
I have mentioned applying the 66Mk2 x-over to Mk1 66 in a Post earlier in this Thread, because the older MF500 mid-dome is lower power capable than the later MD500,
thus if the x-over frequency to MF500 is raised a little the Mk1 66 can be played a bit louder.
This is part-relevant to what I will describe here now for dloper's case,
because he has a 25uF hi-pass filter cap to MF500 now instead of the original 30uF, and interim period 28uF, versions.
When only the cap is reduced a little, and the inductor is left as original,
the x frequency raises, but the filter's Slope is made a little less steep in the x-over region,
thus to combine optimally with the corresponding filter on the bass driver the bass filter should have its slope made a little less steep in the same region,
and maybe also raise its x frequency a little.
If you are restoring Mk1, I suggest trying a 68uF or a parallel pair of 33uF polypropylene caps for the C2 -{nearest to woofer}- ONLY,
and stay with 72uF for the C1, -{use 75uf poly or parallel 36uF pair or 33//39 or 30//40 - all are close enough to work well}.
With new Polypropylene caps, use the same value resistors for the ESR simulation as those I will list here for dloper to use to trick his 80uF electrocaps into behaving like 72uF and 68uF, - BUT NOTE :- this is a TRICK, and the 80uF caps are still 80uF,
thus do not buy 80uF caps -{unless you want whatever audible result dloper reports after he has tried this application}.
For the C1 position connect a 1 ohm wirewound, of not less than 4 watts rating,
in Series between the cap and the Ground/return connection.
For the C2 position connect a 1.5 ohm wirewound/minimum 4 watts,
in Series between the cap and Ground/return.
Stuart, for your 80uF electro application, larger than 1.5 ohm may be required with C2, but start with 1.5 and listen.
If you are not sufficiently satisfied then 2.2 or 2.7 or 3.3 or 3.9 ohms{maximum} can be tried later,
and we may be using the 1.5 ohm elsewhere then, depending on what you report as audible results.
The ESR simulating resistor to place in Series with the 25uF -{or 24uF}- new poly cap in the mids' filter will be decided after dloper had reported his L-pad settings following the other mods here.
For the 4uF, {or 3.9uF}, new poly cap in the mids' filter in the C3 position in parallel with the MF500,
connect a 3.9, or 4, ohm wirewound, minimum 4 watts rating, in Series between the cap and the Ground/return connection.
For buyers restricted to buying in UK, go to :-
Farnell / Electronic Component Distributors / Suppliers / Electronics, Electrical Parts, Electrical Components and Wholesale Electronics.
and to their UK site, and their Passive Components' Fixed Resistors' page.
Slide across the page to the Manufacturers' column in the Search box and select "Welwyn", the click on "Apply/Show Results".
Next, slide back to the "Series" and select their WP-S series, and then WP4S.
These are a 4 watt @ 25*C rated, enhanced pulse handling capacity resistor, thus will likely be very well assembled,
hence have little or none of the mechanical effects in them which can affect resistors sound quality.
Use these for the 1 ohm, 1.5 ohm, 3.9 ohm.
If there is no stock, then Welwyn's basic W series will work OK, use their W22, or higher number, series,
and remember that most wirewound resistors are rated at 25 degrees C, and not 70 degrees C like film resistors,
thus must be of sufficient power rating to be able to stay cool inside a loudspeaker enclosure.
When a resistor heats up, and particually if it fluctuates in temperature during operation, the sound will be affected.
Hot resistors work OK in Power Supplies, but not in audio signal paths.
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a Tweeter resistor, for both Mk1 and Mk2 66s
The Mk1 66 have what seems to be metalized paper-in-oil capacitors in the treble filter.
These are fairly low ESR, and do not behave like electrolytic caps in most of an electro's higher parasitics' ways,
however they can leak electrically - particually as they age - thus do replace them with new polypropylene caps.
The Mk2 66 uses a Mylar-predecessor type cap in the treble filter, and usually they do not leak with age,
unless they have been severely overdriven.
They have substantially less parasitics than electros, but not as low as Polypropylene, thus with Mylars to tweeter and new Polyprop. to mids,
the tone may be not to one's liking, and if so, then install Polyprop. in the treble filter.
An ESR simulating resistor will not be necessary, BUT, to blend in tonally with the basic sound of a 66 in the midrange and bass,
a small value Series resistance may be required - this will depend on personal taste - for the type of sound one wants to hear.
About 0.5 ohm will probably be sufficient, unless you are changing to the new SEAS tweeter I listed in the #317 Post above.
0.5 ohms will probably be OK for the Coles CE 4001 tweeter.
The SEAS will require a larger resistance because it is more sensitive than the HF2000, and will thus be louder,
hence need attenuation.
{Both replacement tweeters will also require parallel connected resistors,
thus if you are replacing tweeters, Post here and state which type.}
Some Manufacturers' catalogs list 0.47 ohm, some list 0.5 ohm, some list 0.51 ohm, and some list as 500mohm, -{or similar}.
Connect this resistor in Series between the last capacitor in the filter and the tweeter.
For this particular application a non-inductive resistor is the best choice.
With only about 0.5 ohms little power will be dissipated, thus a 2 watt rated resistor will stay quite cool.
You can use the 5 watt rated Mills' MRA-5, -{there is no lower power rated Mills}.
Buyers limited to UK sellers can find effectively 2.25 watt rated "Caddock" brand resistors at Farnell -{proceed as described in the last Post}.
Find Caddock's MP930 -{in 900 series}- cataloged as 500mohm.
This is 2.25 watts at 25*C.
The 30watt rating applies ONLY when the resistor is fixed to a Heat Sink,
and that is NOT practical for inside a loudspeaker enclosure,
and heatsinking is not neccessary here, but do mount the resistor in such way so that its body is not touching any surface.
The body needs to stay at the same temperature on all its surfaces,
so mount it standing on its connection legs only - the tabs to which one solders the connecting wires.
Scrape the tabs first, to remove residual surface contamination.
Make a small circle-loop with the connecting wire to stand the resistor in, after scraping the section of wire to clean.
Place the resistor in the wire, heat the joint, then apply the solder when the joint is hot enough, and remove the soldering iron as soon as possible,
because excess heat if long applied unevenly to this type of resistor may damage it, or otherwise reduce its high specification.
Hold so no movement whilst the solder is cooling.
"Vishay" make a similar type of resistor if you cannot buy "Caddock".
Caddock cost about 3.55, and are worth it,
but if you can only afford low price resistors, then Welwyn's WP2S
in either 470mohm or 560mohm will work well enough if you don't have hypercritical hearing ability.
**************************************************
Stuart,
apply all the above resistors to your 66s, and with the L-pad remaining connected in Series with the midrange filter input only.
Listen, and adjust the L-pad to best compromise position for your most critical recordings.
After a listening suitable period, Post your impressions here,
together what-ever else you may like to further achieve.
The Mk1 66 have what seems to be metalized paper-in-oil capacitors in the treble filter.
These are fairly low ESR, and do not behave like electrolytic caps in most of an electro's higher parasitics' ways,
however they can leak electrically - particually as they age - thus do replace them with new polypropylene caps.
The Mk2 66 uses a Mylar-predecessor type cap in the treble filter, and usually they do not leak with age,
unless they have been severely overdriven.
They have substantially less parasitics than electros, but not as low as Polypropylene, thus with Mylars to tweeter and new Polyprop. to mids,
the tone may be not to one's liking, and if so, then install Polyprop. in the treble filter.
An ESR simulating resistor will not be necessary, BUT, to blend in tonally with the basic sound of a 66 in the midrange and bass,
a small value Series resistance may be required - this will depend on personal taste - for the type of sound one wants to hear.
About 0.5 ohm will probably be sufficient, unless you are changing to the new SEAS tweeter I listed in the #317 Post above.
0.5 ohms will probably be OK for the Coles CE 4001 tweeter.
The SEAS will require a larger resistance because it is more sensitive than the HF2000, and will thus be louder,
hence need attenuation.
{Both replacement tweeters will also require parallel connected resistors,
thus if you are replacing tweeters, Post here and state which type.}
Some Manufacturers' catalogs list 0.47 ohm, some list 0.5 ohm, some list 0.51 ohm, and some list as 500mohm, -{or similar}.
Connect this resistor in Series between the last capacitor in the filter and the tweeter.
For this particular application a non-inductive resistor is the best choice.
With only about 0.5 ohms little power will be dissipated, thus a 2 watt rated resistor will stay quite cool.
You can use the 5 watt rated Mills' MRA-5, -{there is no lower power rated Mills}.
Buyers limited to UK sellers can find effectively 2.25 watt rated "Caddock" brand resistors at Farnell -{proceed as described in the last Post}.
Find Caddock's MP930 -{in 900 series}- cataloged as 500mohm.
This is 2.25 watts at 25*C.
The 30watt rating applies ONLY when the resistor is fixed to a Heat Sink,
and that is NOT practical for inside a loudspeaker enclosure,
and heatsinking is not neccessary here, but do mount the resistor in such way so that its body is not touching any surface.
The body needs to stay at the same temperature on all its surfaces,
so mount it standing on its connection legs only - the tabs to which one solders the connecting wires.
Scrape the tabs first, to remove residual surface contamination.
Make a small circle-loop with the connecting wire to stand the resistor in, after scraping the section of wire to clean.
Place the resistor in the wire, heat the joint, then apply the solder when the joint is hot enough, and remove the soldering iron as soon as possible,
because excess heat if long applied unevenly to this type of resistor may damage it, or otherwise reduce its high specification.
Hold so no movement whilst the solder is cooling.
"Vishay" make a similar type of resistor if you cannot buy "Caddock".
Caddock cost about 3.55, and are worth it,
but if you can only afford low price resistors, then Welwyn's WP2S
in either 470mohm or 560mohm will work well enough if you don't have hypercritical hearing ability.
**************************************************
Stuart,
apply all the above resistors to your 66s, and with the L-pad remaining connected in Series with the midrange filter input only.
Listen, and adjust the L-pad to best compromise position for your most critical recordings.
After a listening suitable period, Post your impressions here,
together what-ever else you may like to further achieve.
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