I suggest longer speaker leads connecting to terminal block on crossover-to facilitate swapping & testing.
Suggest terminal block on crossover to facilitate removal and reconnecting
Suggest terminal block segments as replacement for tags on paxolin base:enables capacitors/resistors to be experimentally changed easily.
Suggest terminal block on crossover to facilitate removal and reconnecting
Suggest terminal block segments as replacement for tags on paxolin base:enables capacitors/resistors to be experimentally changed easily.
Fine tune the freq. response
Hello Alan,
I am thinking of fine tuning the 66's treble/upper mids and need your advice. I don't know what specific frequencies I need to look at but the mic. measurements I've taken so far indicate that a good place to start may be the tweeter because the freq. response appears to increase by about 4-5 db when going from 4kHz to 5kHz which is the crossover point.
I have made a SPICE model of the crossovers and have looked at the effect (in db) on the voltage across the tweeter by adding small resistances at various points in the tweeter circuit. Depending on where these are placed I observe that the crossover point can be shifted up, the voltage attenuated etc. For example adding 1R in series with 4u, 2R in series with 6.2u and 1R in series with 0.14mH would shift the crossover point +1kHz, reduce the 6kHz level by more than 3db and by about 2db at 10kHz with a flat db out to 20k as opposed to a rising db. Overall the tweeter would be down by about 2-3db.
Would placing resistances in the tweeter circuit be a good way to fine tune or should I try Lpads or the like? Am I on the right track?
DG
Hello Alan,
I am thinking of fine tuning the 66's treble/upper mids and need your advice. I don't know what specific frequencies I need to look at but the mic. measurements I've taken so far indicate that a good place to start may be the tweeter because the freq. response appears to increase by about 4-5 db when going from 4kHz to 5kHz which is the crossover point.
I have made a SPICE model of the crossovers and have looked at the effect (in db) on the voltage across the tweeter by adding small resistances at various points in the tweeter circuit. Depending on where these are placed I observe that the crossover point can be shifted up, the voltage attenuated etc. For example adding 1R in series with 4u, 2R in series with 6.2u and 1R in series with 0.14mH would shift the crossover point +1kHz, reduce the 6kHz level by more than 3db and by about 2db at 10kHz with a flat db out to 20k as opposed to a rising db. Overall the tweeter would be down by about 2-3db.
Would placing resistances in the tweeter circuit be a good way to fine tune or should I try Lpads or the like? Am I on the right track?
DG
7 kHz target
Some who talk about this say 150 Hz and 7 kHz are ideal crossover points as regards niceness of sound ( if the drive units can do it ) . The phase shifts placed about there helps reduce listening fatigue . If possible don't do the 150 Hz one if designing something new . However if you do , a PA driver is ideal and cheap .
Thus a full range driver like Fostex crossing over to a Air motion tweeter might describe the perfect concept .If so I would crossover at 12 kHz ( higher the better ) . Quad ESL 63's come close to obeying these rules .
I mention this as 5kHz is very close . It might be possible to go a little higher . The order of crossover you use is important . Many use second order and invert the drive unit to compensate if a fixed arrangement .
Falcon Acoustics are a good source of advice .
A cheap alternative to an Air motion tweeter is a Motorola horn pietzo . These need a carefully designed crossover . Personally I would build it a Gain clone amplifier with 10 kHz input filtering ( select the input cap ) . Below 10 kHz they are the cheap nasty horns from discos . They will go up to 40 kHz and at low distortion on the small signals seen above 10 kHz .
Some who talk about this say 150 Hz and 7 kHz are ideal crossover points as regards niceness of sound ( if the drive units can do it ) . The phase shifts placed about there helps reduce listening fatigue . If possible don't do the 150 Hz one if designing something new . However if you do , a PA driver is ideal and cheap .
Thus a full range driver like Fostex crossing over to a Air motion tweeter might describe the perfect concept .If so I would crossover at 12 kHz ( higher the better ) . Quad ESL 63's come close to obeying these rules .
I mention this as 5kHz is very close . It might be possible to go a little higher . The order of crossover you use is important . Many use second order and invert the drive unit to compensate if a fixed arrangement .
Falcon Acoustics are a good source of advice .
A cheap alternative to an Air motion tweeter is a Motorola horn pietzo . These need a carefully designed crossover . Personally I would build it a Gain clone amplifier with 10 kHz input filtering ( select the input cap ) . Below 10 kHz they are the cheap nasty horns from discos . They will go up to 40 kHz and at low distortion on the small signals seen above 10 kHz .
Inductor resistance
These values were posted some years ago.
Has anyone else measured them? Could they post them here please.
These values were posted some years ago.
Has anyone else measured them? Could they post them here please.
another direction to take Celestion 66 in
To date I have primarily been advising about how to upgrade the 66 crossover
in such way as to keep the basic 66 sound that enthusiasts like,
but to add some greater transparency or clarity through.
An alternate to that is to try for higher efficiency
- to get the maximum output possible from the drivers, but still keeping resonant colourations to a minimum.
This will change the basic sound a little more than some enthusiasts of the originals may like,
however I will explain what and why I am proposing this alternate
and concerned listeners can decide whether to proceed this way.
Do ask questions if insufficient has been explained later,
but I will not have time to get through all of this alternate today,
so please be patient for a period of several posts.
What has lead me to this is the recent series of posts by DennyG,
thus I will here address his particular circumstances,
and hopefully the overall plan will be apparent through that.
--- --- --- --- ---
DennyG
- it seems from your recent posts that you are heading in a particular direction,
some by intent, and some by coincidence, thus as follows ...
First, the DC resistances of the Celestion inductors:
There has been a few other measurements posted earlier in the thread,
and those are sufficient for me to think that the ones you quoted of Grahame's are close anough to correct,
though they may read slightly higher than actual because of errors in meters' lowest resistance range.
If you want to know further, find earlier in this thread where I advised Wayne Swan how to calibrate the low resistance range
of his meter by using specific very close Tolerance test resistors.
We found some available in either 1 ohm and/or 4.99 ohm and/or 10 ohm that have either +/- 0.1% or +/- 0.25% Tolerance ,
however even +/- 0.5% or +/- 1% will be sufficient for checking the accuracy of your meter's lowest resistance range,
and subtracting any error figure from your measurements.
For what I am about to propose, it is only the DCR of the two inductors in the bass circuit that we need to be concerned about.
I remember your Spice simulation of earlier - in #788 on page 79
which I never got back to commenting on.
That can give a general idea of effects of changes, but not accurate,
because the program requires a fixed Resistance and a fixed Inductance for the driver's voice-coil,
but any moving coil driver's voice-coil resistance and inductance both change over the full frequency range,
thus any computer simulation that uses a fixed resistance and a fixed inductance can only give a correct result for the single frequency where those occur.
You can spend a lot of time doing Spice simulations, and a lot more time trying to decipher what they are predicting,
or you can spend your time doing other measurements that are more useful for determining the effects of changes in the crossover.
It seems from the plots you posted earlier that both your HF2000 tweeters have extened treble to beyond 16kHz at good level relevant to their output in the lower treble region,
thus I think both are worth persevering with ... and we'll try to deal with the difference between them in Impedance in such way as to cause equal treble output from both.
Your Sugden A28 - is it the original or the mark II version ?
You found the Bias had drifted way off in one channel.
I very strongly advise you carefully set the Bias in both channels as close you can to whatever the original specification is,
because this is a Class A amplifier and as such it runs quite hot.
If the Bias current is too high one or more output transistors will burn out,
and perhaps soon given how old the amp is.
You are in Australia, which has nominally 240 volts mains supply,
however my cousin there has measured the mains voltage at several times of the day in a large city there and found it is often higher than 240 volts and never lower.
Thus if the amp is receiving greater than 240 volts it will be drawing higher current through its Bias circuit than specification ,
unless its Power Supply is Regulated ... and I think it is not ... but do you have any information about that
or a Schematic of its circuit ?
For amplifiers suitable to drive Celestion 66 - there are more than a few, but the ones that will give sound at least as good as a well restored Sugden A28 are quite expensive ... if you want the Class A signature sound and a bit higher power output.
Look at the prices for the current models from Musical Fidelity and Pass Labs - quite expensive !
The current version of Sugden's A22 is lower price, and is arguably a better Class A sound than the old A28,
but it is no higher in power output.
You could change to a higher output amp if you will accept a Class AB type,
and there are few with good sound at moderate prices,
or you can restore your A28, or buy a new A22, and modify your 66s to be a little more efficient.
You might get almost 3dB higher output from them for same power input as currently, and that is technically equivalent to a doubling of amplifier power.
Thus before I proceed any further, what do you prefer to do ?
I have to go now, but I'll try to get back to this before as long as last time !
--- --- --- --- ---
Hi srsanford and nigel pearson,
thankyou for your comments and suggestions.
Yes, the drivers in the old KEF Concertos, and in some other old KEFs such as the 104aB, are good enough to justify time being spent optimising crossovers for them using modern components.
I did a little of that in a KEF thread a while ago, and will do some more when I have time available,
but any KEF will be in another thread and not in this Celestion thread.
I want to keep threads on specific topics, though we have covered a range of Celestion issues in this thread to date !
To date I have primarily been advising about how to upgrade the 66 crossover
in such way as to keep the basic 66 sound that enthusiasts like,
but to add some greater transparency or clarity through.
An alternate to that is to try for higher efficiency
- to get the maximum output possible from the drivers, but still keeping resonant colourations to a minimum.
This will change the basic sound a little more than some enthusiasts of the originals may like,
however I will explain what and why I am proposing this alternate
and concerned listeners can decide whether to proceed this way.
Do ask questions if insufficient has been explained later,
but I will not have time to get through all of this alternate today,
so please be patient for a period of several posts.
What has lead me to this is the recent series of posts by DennyG,
thus I will here address his particular circumstances,
and hopefully the overall plan will be apparent through that.
--- --- --- --- ---
DennyG
- it seems from your recent posts that you are heading in a particular direction,
some by intent, and some by coincidence, thus as follows ...
First, the DC resistances of the Celestion inductors:
There has been a few other measurements posted earlier in the thread,
and those are sufficient for me to think that the ones you quoted of Grahame's are close anough to correct,
though they may read slightly higher than actual because of errors in meters' lowest resistance range.
If you want to know further, find earlier in this thread where I advised Wayne Swan how to calibrate the low resistance range
of his meter by using specific very close Tolerance test resistors.
We found some available in either 1 ohm and/or 4.99 ohm and/or 10 ohm that have either +/- 0.1% or +/- 0.25% Tolerance ,
however even +/- 0.5% or +/- 1% will be sufficient for checking the accuracy of your meter's lowest resistance range,
and subtracting any error figure from your measurements.
For what I am about to propose, it is only the DCR of the two inductors in the bass circuit that we need to be concerned about.
I remember your Spice simulation of earlier - in #788 on page 79
which I never got back to commenting on.
That can give a general idea of effects of changes, but not accurate,
because the program requires a fixed Resistance and a fixed Inductance for the driver's voice-coil,
but any moving coil driver's voice-coil resistance and inductance both change over the full frequency range,
thus any computer simulation that uses a fixed resistance and a fixed inductance can only give a correct result for the single frequency where those occur.
You can spend a lot of time doing Spice simulations, and a lot more time trying to decipher what they are predicting,
or you can spend your time doing other measurements that are more useful for determining the effects of changes in the crossover.
It seems from the plots you posted earlier that both your HF2000 tweeters have extened treble to beyond 16kHz at good level relevant to their output in the lower treble region,
thus I think both are worth persevering with ... and we'll try to deal with the difference between them in Impedance in such way as to cause equal treble output from both.
Your Sugden A28 - is it the original or the mark II version ?
You found the Bias had drifted way off in one channel.
I very strongly advise you carefully set the Bias in both channels as close you can to whatever the original specification is,
because this is a Class A amplifier and as such it runs quite hot.
If the Bias current is too high one or more output transistors will burn out,
and perhaps soon given how old the amp is.
You are in Australia, which has nominally 240 volts mains supply,
however my cousin there has measured the mains voltage at several times of the day in a large city there and found it is often higher than 240 volts and never lower.
Thus if the amp is receiving greater than 240 volts it will be drawing higher current through its Bias circuit than specification ,
unless its Power Supply is Regulated ... and I think it is not ... but do you have any information about that
or a Schematic of its circuit ?
For amplifiers suitable to drive Celestion 66 - there are more than a few, but the ones that will give sound at least as good as a well restored Sugden A28 are quite expensive ... if you want the Class A signature sound and a bit higher power output.
Look at the prices for the current models from Musical Fidelity and Pass Labs - quite expensive !
The current version of Sugden's A22 is lower price, and is arguably a better Class A sound than the old A28,
but it is no higher in power output.
You could change to a higher output amp if you will accept a Class AB type,
and there are few with good sound at moderate prices,
or you can restore your A28, or buy a new A22, and modify your 66s to be a little more efficient.
You might get almost 3dB higher output from them for same power input as currently, and that is technically equivalent to a doubling of amplifier power.
Thus before I proceed any further, what do you prefer to do ?
I have to go now, but I'll try to get back to this before as long as last time !
--- --- --- --- ---
Hi srsanford and nigel pearson,
thankyou for your comments and suggestions.
Yes, the drivers in the old KEF Concertos, and in some other old KEFs such as the 104aB, are good enough to justify time being spent optimising crossovers for them using modern components.
I did a little of that in a KEF thread a while ago, and will do some more when I have time available,
but any KEF will be in another thread and not in this Celestion thread.
I want to keep threads on specific topics, though we have covered a range of Celestion issues in this thread to date !
Last edited:
Hello Alan,
66 Crossovers – I would be interested to see what you have in mind for the alternative crossovers. Are you simply suggesting lower DCR inductors for the bass circuit or are there other things that one can do to improve the crossover?
There wasn’t much reaction on my post #788 on the 66 crossover and I more or less put it aside. The spice models are limited as you say. However, they started me thinking and exploring crossovers in general. I now understand a lot more and want to continue down this road. I’ve been gradually revising the electronics basics I studied many years ago.
DCR of the inductors – I didn’t measure them and the only values I can find are those from Graham. Unfortunately no one else has posted any more results. I guess we assume they are close enough. I did use your suggested calibration method when I measured the DCR of my drivers.
Sugden A28 - is the original version. I put this amp aside some years ago when it had problems with input connectors (RCA) and the relay. It was difficult to get a reliable connection via RCA and no matter what interconnects I tried the sound would eventually start to distort. When I hooked it up again I realisedit basically still sounded good driving the 66’s so I hard wired an interconnect so I could eliminate the distortion and trialed it further. I’ve now replaced the RCA connectors and am now getting excellent results without distortion on any input.
I obtained the schematics for the A28 from Michel and he has helped me with bias settings etc. (This is the relevant thread: http://www.diyaudio.com/forums/solid-state/40886-sugden-p28.html). I haven’t been able to get any information from Sugden on bias adjustments which is disappointing. I don’t think they supply schematics either.
I’ve reset the bias on both channels and the amp now seems to be running nicely warm whereas previously it was just lukewarm. Sugden say in their marketing literature that the amp runs continuously at 10W class A. This rises to 20W class A when required by the incoming music. The maximum power is 35W class B. I’ve scanned the brochure which explains how this works: home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_brochure_c1984.pdf
I may eventually look at other amps (thanks for the amp suggestions) but will carry on with improvements to the A28, at least for now. The 66’s seem efficient enough to be driven by the A28 but time will tell.
The next step for the A28 is replacement of the electrolytics. I pulled a few out and they were all a bit lower than nominal (but not too bad) but one was completely shot. This bad cap was associated with the relay which I removed anyway and may not replace. I’ve purchased some Elna RFS and Nichicon KG caps for the job. It will be interesting to see if they change the sound or not. The amp is now 28 years old! Now that the amp is running hotter changing the caps should give me greater reliability at least.
Mains Voltage – This varies a lot and I’ve seen it range from about 220V to 250V depending where you are and time of day. It was about 245V when I did the bias adjustments. I don’t think the A28 main DC supply is regulated.
RE: #865 above, a Correction, and then a diversion from Celestion subjects.
CORRECTION : I typed Sugden A22 in #865. That is a mistake.
There is not, and probably never was, an A22.
The particular Sugden series of amplifiers I was refering to is A21 ,
of which there has been several models continuing to this day.
A21 is a fully Class A output stage amplifier, thus the difference enthusiast listeners hear between it and A28 -{which DennyG has posted about above}.
I suspect this difference may be only audible at higher volume levels where the A28 has gone into Class AB mode, but I would have to hear both amps again, and of similar vintage and in good condition/restored.
I would expect the latest model A21 to sound better at all volume levels than an old A28 ... but no insult to an A28 !
Denny,
I think Relays are a necessary evil ... if I understand correctly they protect the speaker drivers from the sometimes very loud THUMP which pushes the cones very hard very soon after the amp is switched on,
because the relay delays the output of the amp turning on till after the amp's power supply has charged up.
Technically the capacitors in series with midrange drivers and tweeters should be sufficient to protect those from damage by the voltage surge,
so I suppose the voltage surge causes the loud thump mostly through the bass drivers.
The relay failed in an amplifier I was using years ago, but in that case the amplifier would not switch its output stage on at all after the relay fail.
I had another amplifier to use, and no time to study repair of the first amp so I left it ... and it is still left ... one day I will study up on relays and repair that amp, however as it will need electrolytic caps replaced and possibly some other things done to it, it will be a long while till I get to it.
I always turn on the Source components before I turn on other amplifiers I have used since, and always have the Volume control at minimum before I turn amps on.
I get very small thump sounds when I turn on either of the amps I alternately use, and so small with one I suppose it has a relay, but the other may not have a relay ... I have never looked inside it, but I will when I get a Schematic as I want to check its Bias, and later replace electro caps, etc ...
however I think if an amp can be safely used without a relay circuit then that would be a good thing !
Hardwiring the Interconnect is a good idea !
You mentioned in an earlier post that the midrange sound hardens when the Sugden is pushed ... that could be you have reached full capacity of its power stage, or it could be that the power supply and/or line supply electrolytic caps are not holding sufficient charge.
I'd replace all Polar electrolytics in the circuit,
and if there are any Bipolar electros, such as for decoupling between amplification stages, I'd replace those also becasue if DC leaks from output of one stage to input of next stage that next stage will not be correctly biased.
The actual Bias you can adjust will be only for the output stage.
Every transistor in the amp needs a bias current, and in the earlier stages of the amp those are pre-set by the design.
Electro caps:
as the Black Gate capacitors are no longer manufactured, and very few values left to buy,
next best to buy are Elna Cerafine.
I would use those in all the amplifier, but if no Cerafines in suitable capacitance or Voltage rating for the large filter caps, then I'd use whichever Nichicon range in their specialist Audio caps is the high voltage type ...
{I have forgotten which}.
Elna Silmic are said to be the next best after Cerafine.
The enthusiasts say they sound different to Cerafine, but still good.
One fellow who has lots of time to experiment says he trys Cerafine and Silmic in every stage, and chooses which he likes the sound of best for each.
Ideally if one uses the same type of cap throughout the circuit, including in the Feedback paths, that will cause the cleanest sound -{assuming all are good audio quality caps},
but if you can't use same type for the largest filter caps, then try to use the same type for all the small signal sections and the feedback loop.
That should give cleaner sound than when using different type in feedback to what is used in the small signal forward path.
Elna RFS are Silmic, and Elna RBS are Silmic Bipolar.
Cerafine are type ROA, and perhaps another type I cannot find now.
A third Elna audio grade are Tonerex - ROB.
Nichicon do have Bipolars with the same type of internal substances as their Audio grade polarized caps, but simply with a different two-letter prefix for their model type.
Using a mixture of different quality audio grade caps can cause less clear sound than when using all of the same internal substances type.
This has been found in listening tests of Prototypes for amplifiers, eg: by Audiolab there was a listener report published years ago where the only cap changed in the circuit was a trial of several in a critical position of the feedback loop.
John Linsley Hood, famous for a Class A amplifier design, had written about that many years previously.
--- --- ---
I'll return to the current Celestion theme in the next post.
--- --- ---
EDIT: after nigel pearson who posted just after me {below in #868} -
Thankyou Nigel for the suggestions - these seem believeable, but will only work in limited applications,
as your 0.4 volts indicates.
I recommend that anyone who trys using Polarized electros with no Bias voltage proceed very carefully,
because they will fail, and sometimes explosively, if excess reverse polarity voltage is applied to them.
That is apparent in Nigel's post #868, but it does need emphasis !
I don't know much about relays Nigel - let's see what DennyG may know.
CORRECTION : I typed Sugden A22 in #865. That is a mistake.
There is not, and probably never was, an A22.
The particular Sugden series of amplifiers I was refering to is A21 ,
of which there has been several models continuing to this day.
A21 is a fully Class A output stage amplifier, thus the difference enthusiast listeners hear between it and A28 -{which DennyG has posted about above}.
I suspect this difference may be only audible at higher volume levels where the A28 has gone into Class AB mode, but I would have to hear both amps again, and of similar vintage and in good condition/restored.
I would expect the latest model A21 to sound better at all volume levels than an old A28 ... but no insult to an A28 !
Denny,
I think Relays are a necessary evil ... if I understand correctly they protect the speaker drivers from the sometimes very loud THUMP which pushes the cones very hard very soon after the amp is switched on,
because the relay delays the output of the amp turning on till after the amp's power supply has charged up.
Technically the capacitors in series with midrange drivers and tweeters should be sufficient to protect those from damage by the voltage surge,
so I suppose the voltage surge causes the loud thump mostly through the bass drivers.
The relay failed in an amplifier I was using years ago, but in that case the amplifier would not switch its output stage on at all after the relay fail.
I had another amplifier to use, and no time to study repair of the first amp so I left it ... and it is still left ... one day I will study up on relays and repair that amp, however as it will need electrolytic caps replaced and possibly some other things done to it, it will be a long while till I get to it.
I always turn on the Source components before I turn on other amplifiers I have used since, and always have the Volume control at minimum before I turn amps on.
I get very small thump sounds when I turn on either of the amps I alternately use, and so small with one I suppose it has a relay, but the other may not have a relay ... I have never looked inside it, but I will when I get a Schematic as I want to check its Bias, and later replace electro caps, etc ...
however I think if an amp can be safely used without a relay circuit then that would be a good thing !
Hardwiring the Interconnect is a good idea !
You mentioned in an earlier post that the midrange sound hardens when the Sugden is pushed ... that could be you have reached full capacity of its power stage, or it could be that the power supply and/or line supply electrolytic caps are not holding sufficient charge.
I'd replace all Polar electrolytics in the circuit,
and if there are any Bipolar electros, such as for decoupling between amplification stages, I'd replace those also becasue if DC leaks from output of one stage to input of next stage that next stage will not be correctly biased.
The actual Bias you can adjust will be only for the output stage.
Every transistor in the amp needs a bias current, and in the earlier stages of the amp those are pre-set by the design.
Electro caps:
as the Black Gate capacitors are no longer manufactured, and very few values left to buy,
next best to buy are Elna Cerafine.
I would use those in all the amplifier, but if no Cerafines in suitable capacitance or Voltage rating for the large filter caps, then I'd use whichever Nichicon range in their specialist Audio caps is the high voltage type ...
{I have forgotten which}.
Elna Silmic are said to be the next best after Cerafine.
The enthusiasts say they sound different to Cerafine, but still good.
One fellow who has lots of time to experiment says he trys Cerafine and Silmic in every stage, and chooses which he likes the sound of best for each.
Ideally if one uses the same type of cap throughout the circuit, including in the Feedback paths, that will cause the cleanest sound -{assuming all are good audio quality caps},
but if you can't use same type for the largest filter caps, then try to use the same type for all the small signal sections and the feedback loop.
That should give cleaner sound than when using different type in feedback to what is used in the small signal forward path.
Elna RFS are Silmic, and Elna RBS are Silmic Bipolar.
Cerafine are type ROA, and perhaps another type I cannot find now.
A third Elna audio grade are Tonerex - ROB.
Nichicon do have Bipolars with the same type of internal substances as their Audio grade polarized caps, but simply with a different two-letter prefix for their model type.
Using a mixture of different quality audio grade caps can cause less clear sound than when using all of the same internal substances type.
This has been found in listening tests of Prototypes for amplifiers, eg: by Audiolab there was a listener report published years ago where the only cap changed in the circuit was a trial of several in a critical position of the feedback loop.
John Linsley Hood, famous for a Class A amplifier design, had written about that many years previously.
--- --- ---
I'll return to the current Celestion theme in the next post.
--- --- ---
EDIT: after nigel pearson who posted just after me {below in #868} -
Thankyou Nigel for the suggestions - these seem believeable, but will only work in limited applications,
as your 0.4 volts indicates.
I recommend that anyone who trys using Polarized electros with no Bias voltage proceed very carefully,
because they will fail, and sometimes explosively, if excess reverse polarity voltage is applied to them.
That is apparent in Nigel's post #868, but it does need emphasis !
I don't know much about relays Nigel - let's see what DennyG may know.
Last edited:
I've seen it said all small signal electrolytic's sound best if unpolarised which seems the reverse of expectations . This means keeping them below 0.4V . The special ones even more so . My 100 Watt amp crosses that voltage at about 12 watts output which is already loud ( gain of 34 , 100 uF NP feedback cap ) . I have used the amp with higher gain . Maybe I benefited from that ? The sound was very good ( gain 101 to use with passive preamp .) . I am told the problem increases with voltage used .
I wonder if a 0.1 uF across the relay contacts would be useful ? Sometimes do that with fuses .
I wonder if a 0.1 uF across the relay contacts would be useful ? Sometimes do that with fuses .
Last edited:
Continuing about Celestion 66, including a Correction.
We will be applying lower DCR inductors, though in the bass circuit only.
The DCRs of the Celestion inductors are additionally posted somewhere,
perhaps someone simply stated his measured the same, or perhaps they were mentioned in the text, and not set out in form like Graham did.
It does not matter, because the resistances G found are about what I would expect for those inductors,
and high enough to lose significant signal when connected to a nominal 4 ohm driver.
Correction:
I stated in #865 :
You might get almost 3dB higher output from them for same power input as currently, and that is technically equivalent to a doubling of amplifier power.
.
That is a mistake, and obviously my brain was not fully in gear when I typed that !
There will be less than half that measurable if a simple amplitude plot made,
though such increase will be audible,
but the impact effect of faster Transients in the upper bass and lower mids will give the audible effect of significantly louder.
To fully appreciate that we need the midrange to play a bit louder also.
That is easily done by reducing the amount of series resistance I earlier posted about for the ESR simulating resistor connected to the 25uF cap.
Some of you will have 1.8 ohms there, or a little less or a little more.
After installing lower DCR inductors in the bass, next is to reduce the mids' resistor to maximum of 1 ohm, and perhaps lower.
You can decide this by ear - listen for the amount of midrange level in comparison to the new bass level.
The resistor in series with the 3.9uF or 4uF cap in the mids' circuit is not to be removed, nor made very low.
I think minimum about 2.7 ohm, maximum about 3.9 ohm.
Some resistance is necessary there or there will be excess resonant colouration - as I explained earlier in this thread.
Treble:
If you have installed SEAS 19TFF1/H737 tweeters you will have plenty of output to balance the increases in mids and bass.
If you have the original Celestion HF2000 tweeters you may not have enough level.
It seems from DennyG's measurements earlier in this thread that his samples of HF2000 are quite high in output,
and one more-so than the other,
but that is not what is shown on Celestion's own measured plot - there the treble is slightly lower in level than the mids,
thus before anyone changes anything, listen ...
relative to the mids and bass, how loud is the treble from your HF2000s ?
Denny,
before we proceed further, do you want to measure your HF2000s again - to determine exactly how much one may be louder than the other ?
For now, if you have one resistor in minimum of 27 ohms, or larger to maximum of 56 ohms, in not less than 5 watts if a wirewound type,
connect it in Parallel with the higher DCR tweeter, then listen.
This may not acheive much, but its worth a try.
Is the treble level same from both loudspeakers ?
If you can't buy a single resistor, then buy two of 56 ohm in 1 watt carbon film
{or greater power if available, or at least the largest body size 1 watter you see in the box,
because those dissipate heat better than the mini-size supposed 1 watters, which really should be de-rated for use}.
Connect them in Parallel : 56//56 = 28 ohms , only 2 watts but if you don't play the speakers too loudly this pair of resistors will not excessively heat,
because most of the signal is going through the tweeter, not through the resistor.
This is only an experiment - it may not produce a suitable result, but if it does a better resistor can be bought later.
sba
- who visits unexpected to this forum sometimes !
{I'll respond to that post in the other thread when I have time available.}
The JBL tweeters you have will almost certainly have sufficient output to match any increase in mids and bass level that can be achieved.
Everyone :
do you want to wind your own new bass inductors ?
They will need thick wire, and will be a bit more difficult to wind than small size thin wire inductors.
They will be larger physical size than the old inductors.
or, do you want to buy new inductors ?
I have to go now - but anyone interested, post what you would like to try with your 66s in the above regard.
We will be applying lower DCR inductors, though in the bass circuit only.
The DCRs of the Celestion inductors are additionally posted somewhere,
perhaps someone simply stated his measured the same, or perhaps they were mentioned in the text, and not set out in form like Graham did.
It does not matter, because the resistances G found are about what I would expect for those inductors,
and high enough to lose significant signal when connected to a nominal 4 ohm driver.
Correction:
I stated in #865 :
You might get almost 3dB higher output from them for same power input as currently, and that is technically equivalent to a doubling of amplifier power.
.
That is a mistake, and obviously my brain was not fully in gear when I typed that !
There will be less than half that measurable if a simple amplitude plot made,
though such increase will be audible,
but the impact effect of faster Transients in the upper bass and lower mids will give the audible effect of significantly louder.
To fully appreciate that we need the midrange to play a bit louder also.
That is easily done by reducing the amount of series resistance I earlier posted about for the ESR simulating resistor connected to the 25uF cap.
Some of you will have 1.8 ohms there, or a little less or a little more.
After installing lower DCR inductors in the bass, next is to reduce the mids' resistor to maximum of 1 ohm, and perhaps lower.
You can decide this by ear - listen for the amount of midrange level in comparison to the new bass level.
The resistor in series with the 3.9uF or 4uF cap in the mids' circuit is not to be removed, nor made very low.
I think minimum about 2.7 ohm, maximum about 3.9 ohm.
Some resistance is necessary there or there will be excess resonant colouration - as I explained earlier in this thread.
Treble:
If you have installed SEAS 19TFF1/H737 tweeters you will have plenty of output to balance the increases in mids and bass.
If you have the original Celestion HF2000 tweeters you may not have enough level.
It seems from DennyG's measurements earlier in this thread that his samples of HF2000 are quite high in output,
and one more-so than the other,
but that is not what is shown on Celestion's own measured plot - there the treble is slightly lower in level than the mids,
thus before anyone changes anything, listen ...
relative to the mids and bass, how loud is the treble from your HF2000s ?
Denny,
before we proceed further, do you want to measure your HF2000s again - to determine exactly how much one may be louder than the other ?
For now, if you have one resistor in minimum of 27 ohms, or larger to maximum of 56 ohms, in not less than 5 watts if a wirewound type,
connect it in Parallel with the higher DCR tweeter, then listen.
This may not acheive much, but its worth a try.
Is the treble level same from both loudspeakers ?
If you can't buy a single resistor, then buy two of 56 ohm in 1 watt carbon film
{or greater power if available, or at least the largest body size 1 watter you see in the box,
because those dissipate heat better than the mini-size supposed 1 watters, which really should be de-rated for use}.
Connect them in Parallel : 56//56 = 28 ohms , only 2 watts but if you don't play the speakers too loudly this pair of resistors will not excessively heat,
because most of the signal is going through the tweeter, not through the resistor.
This is only an experiment - it may not produce a suitable result, but if it does a better resistor can be bought later.
sba
- who visits unexpected to this forum sometimes !
{I'll respond to that post in the other thread when I have time available.}
The JBL tweeters you have will almost certainly have sufficient output to match any increase in mids and bass level that can be achieved.
Everyone :
do you want to wind your own new bass inductors ?
They will need thick wire, and will be a bit more difficult to wind than small size thin wire inductors.
They will be larger physical size than the old inductors.
or, do you want to buy new inductors ?
I have to go now - but anyone interested, post what you would like to try with your 66s in the above regard.
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Relays, Electrolytics for amps & 66 sound
The relay for the A28 is no longer available and there is no pin for pin replacement. I will probably replace it in due course as part of a full restore.
Hardwiring the interconnect worked well. However, the cable I used wasn’t the best for the job. I didn’t realize this until I ran a quick check on the new RCA connections by comparing the sound of the hardwired connection with all the RCA/RCA interconnects I had available. The best results, sound wise, were using my best (commercially made) interconnect (durrr). I was amazed at how much difference there is between individual interconnects. So I was confident in the new RCA connections and removed the hardwired one.
I have finished replacing all the electrolytics in the A28. I did some research and decided on the Elna Silmic (RFS) for the lower values and Nichicon KG for the 4700uF and 10000uF. Elna indicate in their product sheets that RFS caps are their highest grade so I went with them. They indicate that the grade order is ROB > ROA > ROS > RFS (highest). I’ve no doubt that the cap types all sound different but at this stage I’m not going to attempt a comparison between RFS/ROA in my A28! If I can find another A28 (or A21) I might use something different just for fun). It’s interesting what you say about using different brand caps as the originals were from various manufacturers and in various sizes. I generally used higher voltages than the originals and noted that the RFS caps were generally much larger than the originals even for the same voltage rating. All the electrolytics are polar type.
The results of the latest upgrade were astounding. The little Sugden seemed like a new amplifier and is now an even better match with the 66’s. They appear to go well together. The sound from both CD and phono is now quite superb. I can’t wait to do some more extensive listening. The 66’s keep amazing me.
During the cap upgrade process I hooked up my valve amp to the 66’s and the results (as before) were a very average sound (I use different speaker cables with this amp so must check that one day). The sound is probably best described as a ‘hole in the middle’ with obvious ringing in the treble. Amps are so important if one want’s the best from the 66’s.
The relay for the A28 is no longer available and there is no pin for pin replacement. I will probably replace it in due course as part of a full restore.
Hardwiring the interconnect worked well. However, the cable I used wasn’t the best for the job. I didn’t realize this until I ran a quick check on the new RCA connections by comparing the sound of the hardwired connection with all the RCA/RCA interconnects I had available. The best results, sound wise, were using my best (commercially made) interconnect (durrr). I was amazed at how much difference there is between individual interconnects. So I was confident in the new RCA connections and removed the hardwired one.
I have finished replacing all the electrolytics in the A28. I did some research and decided on the Elna Silmic (RFS) for the lower values and Nichicon KG for the 4700uF and 10000uF. Elna indicate in their product sheets that RFS caps are their highest grade so I went with them. They indicate that the grade order is ROB > ROA > ROS > RFS (highest). I’ve no doubt that the cap types all sound different but at this stage I’m not going to attempt a comparison between RFS/ROA in my A28! If I can find another A28 (or A21) I might use something different just for fun). It’s interesting what you say about using different brand caps as the originals were from various manufacturers and in various sizes. I generally used higher voltages than the originals and noted that the RFS caps were generally much larger than the originals even for the same voltage rating. All the electrolytics are polar type.
The results of the latest upgrade were astounding. The little Sugden seemed like a new amplifier and is now an even better match with the 66’s. They appear to go well together. The sound from both CD and phono is now quite superb. I can’t wait to do some more extensive listening. The 66’s keep amazing me.
During the cap upgrade process I hooked up my valve amp to the 66’s and the results (as before) were a very average sound (I use different speaker cables with this amp so must check that one day). The sound is probably best described as a ‘hole in the middle’ with obvious ringing in the treble. Amps are so important if one want’s the best from the 66’s.
If you get a chance could you do a simple list of caps you used in the Sugden and function ( feedback , input , next to VAS etc ) .
The representative of Sugden (and Castle speakers ) was Mr Eighteen ( yes ) . He was very smart like a butler on his day off . One day I said to him you must be nearing retirement soon . His answer was that he was in his 80's ! This was about 1980 .
The Sugden man I met at a show was like a very big bald-headed wrestler ( I don't think it was Mr Sugden ) . I was very young and a little frightened of him . That was until I spoke to him . Very cultured and lover of classical music . When Sugden closed it was because Mr Sugden was offered a job teaching at a local college I seem to remember . His brother who made Connoisseur turntables got a job there also if I am right ? I am not sure if Sugden was bought immediately . I am very pleased it continues . The A48 is beautiful and a bargain . Only company Julian Vereker of Naim said was a worthy competitor .
If you go active you can design bespoke amplifiers which up to 3rd order need no op amps to do the filter action . The gain clones would be suitable . JLH 10 watt class A ideal . The bass class AB would be fantastic . Even 4th order with a little thought . Opinions vary on this . I think BBC used 4th order ? The other ideal part of this is that the PSU of each amp can be made optimum . The tweeter amp might be fed from the main PSU with a simple RC filter ( 1 watt amp should be enough ) .
One could even fit a cheap Motorola horn disco tweeter . This was done by Proac ( Celef ) . If crossed over at 10 kHz they are remarkable ( Proac wasn't as far as I know crossed over like that ) . The nasty sound they often make is when being driven at 3 kHz . Even people with defective hearing can enjoy a super tweeter ( up to 40 kHz ) as done correctly it restores waveform shape ( square waves if you get it right will be possible at 2kHz ) . Celef was Celestion-KEF if I remember ? He mixed the parts . Celef like Dynaco liked resistive port loading ( drinking straws ) .Celestion's resistive port alternative was the ABR passive bass resonator ( also KEF and Klipsche )
The representative of Sugden (and Castle speakers ) was Mr Eighteen ( yes ) . He was very smart like a butler on his day off . One day I said to him you must be nearing retirement soon . His answer was that he was in his 80's ! This was about 1980 .
The Sugden man I met at a show was like a very big bald-headed wrestler ( I don't think it was Mr Sugden ) . I was very young and a little frightened of him . That was until I spoke to him . Very cultured and lover of classical music . When Sugden closed it was because Mr Sugden was offered a job teaching at a local college I seem to remember . His brother who made Connoisseur turntables got a job there also if I am right ? I am not sure if Sugden was bought immediately . I am very pleased it continues . The A48 is beautiful and a bargain . Only company Julian Vereker of Naim said was a worthy competitor .
If you go active you can design bespoke amplifiers which up to 3rd order need no op amps to do the filter action . The gain clones would be suitable . JLH 10 watt class A ideal . The bass class AB would be fantastic . Even 4th order with a little thought . Opinions vary on this . I think BBC used 4th order ? The other ideal part of this is that the PSU of each amp can be made optimum . The tweeter amp might be fed from the main PSU with a simple RC filter ( 1 watt amp should be enough ) .
One could even fit a cheap Motorola horn disco tweeter . This was done by Proac ( Celef ) . If crossed over at 10 kHz they are remarkable ( Proac wasn't as far as I know crossed over like that ) . The nasty sound they often make is when being driven at 3 kHz . Even people with defective hearing can enjoy a super tweeter ( up to 40 kHz ) as done correctly it restores waveform shape ( square waves if you get it right will be possible at 2kHz ) . Celef was Celestion-KEF if I remember ? He mixed the parts . Celef like Dynaco liked resistive port loading ( drinking straws ) .Celestion's resistive port alternative was the ABR passive bass resonator ( also KEF and Klipsche )
Sugden A28 replacement caps
The cap list for the replacements I used in the Sugden A28 is is available here:
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_Cap_replacement_list.pdf
Also indicated are the voltage ratings and dimensions for the original caps along with some of the markings.
There is no indication in the list as to the cap function. If you need that information I loaded the circuit diagram and pcb layout to here:
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_circuit.pdf
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_PCB_layout.pdf
These were kindly made available by Michel as gif's and I've turned them into PDF's.
The cap list for the replacements I used in the Sugden A28 is is available here:
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_Cap_replacement_list.pdf
Also indicated are the voltage ratings and dimensions for the original caps along with some of the markings.
There is no indication in the list as to the cap function. If you need that information I loaded the circuit diagram and pcb layout to here:
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_circuit.pdf
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_PCB_layout.pdf
These were kindly made available by Michel as gif's and I've turned them into PDF's.
Thanks Denny . That is very helpful . I am getting ideas for a new amp . I made one for some friends in Germany .They upgraded the caps . They found it too difficult to do what you have ( I assume ) . Apparently they will gift me an amp one day with the updates. I think a simple list would have made me happier ! I know Mundorf for the big caps and that's about all . They unwrap caps so I suppose I will never know !
It sort of makes sense unwrapping caps if believing about dielectrics and sound as we do . If you measure the outside of a cap there is a voltage ( to one terminal and the can ) . Thus the plastic will have some effect .
If wanting to market a cheap Audiophile cap ( Audiofool if you don't believe ) take a non-polar and paper sleeve it .
Someone said it removes your UL and other protection rights . For most circuits it isn't an issue . One could always re-certificate .
It sort of makes sense unwrapping caps if believing about dielectrics and sound as we do . If you measure the outside of a cap there is a voltage ( to one terminal and the can ) . Thus the plastic will have some effect .
If wanting to market a cheap Audiophile cap ( Audiofool if you don't believe ) take a non-polar and paper sleeve it .
Someone said it removes your UL and other protection rights . For most circuits it isn't an issue . One could always re-certificate .
Caps
Maybe the size of the cap affects the sound in addition to all the other variables. Some of the original caps were tiny compared to their replacements. I know very little on the ins and outs of caps and have never heard of 'unwrapping' them.
For the record I've updated the
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_Cap_replacement_list.pdf
file with the measured uF's of the old and (most of) the new caps and their % deviation from nominal.
I purchased the Sugden amp many years ago because it sounded better than some others I evaluated in the home environment including a small Naim amp. I also had a Connoisseur turntable at the time. I am a bit surprised at the A28 as it appears quite modest internally. It has a little hand written sticker near the transformer with a woman's name on it, the builder/tester perhaps. I wonder if anyone has attempted other mods to it. I guess we are straying from the 66 thread a bit!
Maybe the size of the cap affects the sound in addition to all the other variables. Some of the original caps were tiny compared to their replacements. I know very little on the ins and outs of caps and have never heard of 'unwrapping' them.
For the record I've updated the
home.exetel.com.au/justlucky/SugdenA28/Sugden_A28_Cap_replacement_list.pdf
file with the measured uF's of the old and (most of) the new caps and their % deviation from nominal.
I purchased the Sugden amp many years ago because it sounded better than some others I evaluated in the home environment including a small Naim amp. I also had a Connoisseur turntable at the time. I am a bit surprised at the A28 as it appears quite modest internally. It has a little hand written sticker near the transformer with a woman's name on it, the builder/tester perhaps. I wonder if anyone has attempted other mods to it. I guess we are straying from the 66 thread a bit!
As far as I know the golden rule is voltage . This forces better construction which creates Audiophile devices as a byproduct . DNM used slit foils to inhibit eddy currents in the fol . This was a neat trick . Non polar's make good small signal caps ( i.e. feedback cap )
DNM Products - Capacitors (overview)
Non-Polar Electrolytic Capacitors | ERSE
I feel talking about amps the Celestion's grew up with highly important . I had never heard a pair until a lady brought me some 66's to match with a modern amplifier ( I forget which one ) . I was stunned by the correctness of them . I suspect the interaction with Spendor who used the HF1300 tweeter had something to do with it . Klipsche Forte also . Nothing like I imagined and not much like the Heresy it is derived from . It sort of proves the point that drive units alone do not dictate the outcome . Cabinet and crossover perhaps 80% of it ? Talking of cabinets I hear Lockwoood Audio are back and producing the famous Lockwood Tannoys again . Spendor was a sort of baby Lockwood cabinet .
DNM Products - Capacitors (overview)
Non-Polar Electrolytic Capacitors | ERSE
I feel talking about amps the Celestion's grew up with highly important . I had never heard a pair until a lady brought me some 66's to match with a modern amplifier ( I forget which one ) . I was stunned by the correctness of them . I suspect the interaction with Spendor who used the HF1300 tweeter had something to do with it . Klipsche Forte also . Nothing like I imagined and not much like the Heresy it is derived from . It sort of proves the point that drive units alone do not dictate the outcome . Cabinet and crossover perhaps 80% of it ? Talking of cabinets I hear Lockwoood Audio are back and producing the famous Lockwood Tannoys again . Spendor was a sort of baby Lockwood cabinet .
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My original amp for the 66's was a Rotel tuner amp and this drove them well. I then used a Lecson AC1/AP1. I'd love to try a modern design amp with them. Perhaps I will take on building one myself!
I think you are correct Nigel about the contribution of both the cabinet & crossover.
I have a pair of SL600's which have fairly inert cabinets which, I think, contribute little to their overall sound. However, I have been thinking recently that the cabinets of the 66's may contribute somewhat to their overall 'sound'. Maybe the designers hit on a good combination of cabinet shape, materials and bracing.
I put my 66's aside when they no longer seemed to perform to my liking. I attempted to resurrect them, at one stage, after reading about how much better (someones?) speakers sounded when the crossover caps were replaced by Solens. I did that and still the speakers sounded 'wrong'. It wasn't until I came across Alan's suggestion of the addition of ESR resistors that they came back to life. I was amazed that such a small crossover modification could change the overall sound so much.
Interesting about SL600 . I love them and less so 6000's The 600 has a 22 kHz notch filter I seem to remember ? I am known for not liking low efficiency speakers . SL600 an exception . I never heard the remarkable sub woofers that use an open baffle . That seems so much better if the graphs don't lie . Lockwood Audio are back , their old cabinets are not what the computer says yes to ( T&S ) . Lockwood has a following . Plywood is back in fashion . I think a Plywood-MDF sandwich makes sense .
treble level
The last set of tests indicated the left tweeter (DCR=4.3R) had a higher sound output (of about 2db) than the right (DCR=5.2R). However, listening to them over a short period, the RHS seems to have more treble (soprano, is that suitable?) than the left. Maybe the midrange is contributing to this result as my tests on the left mid (MF500, DCR=7.3R) indicated a sound output about 1 db lower than the right mid (MD500, DCR=6.3R).
Is adding the 27-56R to the right tweeter still worth trying? I have a couple of 56R 10W ceramics. How would I best reduce the right mid by about 1 db or so? Would this be worthwhile or should I wait until I can do some more testing.........I think it would be a good idea if I repeated the tests on the HF2000's. I want to update my equipment a little as I have new laptop and need a usb audio interface so this may take some time to achieve. I was also thinking of getting a calibrated mic.
The new inductors sound interesting. Are there suitable commercial ones available?
The last set of tests indicated the left tweeter (DCR=4.3R) had a higher sound output (of about 2db) than the right (DCR=5.2R). However, listening to them over a short period, the RHS seems to have more treble (soprano, is that suitable?) than the left. Maybe the midrange is contributing to this result as my tests on the left mid (MF500, DCR=7.3R) indicated a sound output about 1 db lower than the right mid (MD500, DCR=6.3R).
Is adding the 27-56R to the right tweeter still worth trying? I have a couple of 56R 10W ceramics. How would I best reduce the right mid by about 1 db or so? Would this be worthwhile or should I wait until I can do some more testing.........I think it would be a good idea if I repeated the tests on the HF2000's. I want to update my equipment a little as I have new laptop and need a usb audio interface so this may take some time to achieve. I was also thinking of getting a calibrated mic.
The new inductors sound interesting. Are there suitable commercial ones available?
The BBC used autotransformers to get the levels right . It has a certain correctness about it . I suspect the inductance can be tuned at the same time ? Sowter in the UK might have something ? The LS3/5A one might suit ( try Falcon Acoustics ) . It might also damp the tweeters a bit as it has a low inpedance connection like active .
I have always though semi active worth trying . A buffer amp inside the box with filters built in . It could be a simple class A Source follower FET with suitable coupling cap and a nice big voltage . It would simple copy what is fed into it . Getting gain of less than 1 is easy if using a divider . I dare say a valve / tube cathode follower could be used . 6 and 12 db slopes are easy ( or something of 2 x 6 dB ) . "Inside" perhaps is best slightly outside . If you put the crossover outside sometimes it alters the filters a fraction as the magnetic field chances ( where inductors used ) . Bi wiring etc is worth it as it stops the drive units talking to each other ( they do at the crossover points , assuming voltage drive in these statements ) . When bi/tri wiring the sound can change dramatically and not always for the best . Retuning recuses that . If liking both try connecting single wiring to the tweeter then a very small resistance to the bass sometimes ( 0R047 x 2 ) . This will do more good than harm and is what I call alternative bi wiring . It seems all wrong . However it is the tweeter that objects most to single wiring
I have always though semi active worth trying . A buffer amp inside the box with filters built in . It could be a simple class A Source follower FET with suitable coupling cap and a nice big voltage . It would simple copy what is fed into it . Getting gain of less than 1 is easy if using a divider . I dare say a valve / tube cathode follower could be used . 6 and 12 db slopes are easy ( or something of 2 x 6 dB ) . "Inside" perhaps is best slightly outside . If you put the crossover outside sometimes it alters the filters a fraction as the magnetic field chances ( where inductors used ) . Bi wiring etc is worth it as it stops the drive units talking to each other ( they do at the crossover points , assuming voltage drive in these statements ) . When bi/tri wiring the sound can change dramatically and not always for the best . Retuning recuses that . If liking both try connecting single wiring to the tweeter then a very small resistance to the bass sometimes ( 0R047 x 2 ) . This will do more good than harm and is what I call alternative bi wiring . It seems all wrong . However it is the tweeter that objects most to single wiring
Amplifiers for Celestion 66, and for the Measurements ?
Hi Nigel,
what amplifier models, vintage or modern, have you found to work well with Celestion 66 ?
either to moderate volume level in a small room,
or to high volume in a large room.
Some about your other recent points:
With 44kHz Digital, which all CDs are, there is no Square Wave when one gets to only 3kHz !
I would try to get flat response in tweeter to 20Khz to keep correct waveshape, including with CD's 44kHz sampling rate.
The plastic wrap outside a capacitor is not a Dielectric,
because it has voltage charge against only one side of it,
thus I do not know why removing the insulation sleeve would improve the sound,
but if the sleeve was loose, a tighter one would better damp vibrations in the metal case.
Can you post a Reference to whatever whoever is claiming about sleeveless capacitors ?
DNM's ideas and designs for Slit Foil caps and T caps are sensible.
The German Roedestein company had a similar design to DNM's T-cap years ago - pehaps still do ...
They are now Vishay-Roedestein.
So far as I know DNM was the first for Slit Foils.
Most of those ERSE non-polars are not wonderful as they have 10% and 6% Dissipation Factors,
which is better than was the case many years ago,
but 5% D.F. non-polars are readily available now, and there are 3% now also,
which I see at least a few of ERSE's are.
Also, the D.F. is only specified at 1kHz, though it is usually similar or better at lower frequencies,
but usually worse at higher frequencies, except for special design low-impedance caps such as a few companies manufacture now for use in those high frequency power supplies.
Celestion had the 22kHz notch filter in the early SL6, but took it out later because it also caused audible effect lower in the treble.
I do not remember when it was removed ... but possibly when they changed from the copper dome to aluminium dome tweeter,
as the resonance was higher in frequency with the Al dome,
sufficiently so to be not audible, thus no need for a filter.
The SL600 and SL700 I heard had very clear treble, thus not likely a high treble filter present.
I last heard them many years ago, thus cannot comment about how their treble sounds compared to the best current metal domes,
but I have heard some not good metal domes interim !
I prefer bi-wiring, when done well, but that will require a new terminal block be installed in 66,
which some owners may not want to do, thus I have not mentioned it in this thread.
--- --- --- --- ---
Hi Denny,
you have certainly done a lot of work with capacitor replacements !
and as such you deserve the good result you are now hearing.
I have printed that A28 schematic to study,
though immediately I saw something which had recently entered my mind to ask you,
thus before we proceed further:
Which amplifier did you use between signal generator and 66 when you did the measurements for the Celestion drive units,
especially when for the tweeters,
your A28 {before you recondioned it} ?
or a Valve/Tube amplifier ?
or your old Rotel Receiver ?
or a fairly new model Solid State amplifier in good condition ?
Also, do you hear a loud, or quiet, thump sound through the speakers when you switch on the A28, now that it has no Relay ?
Music to listen to tweeters:
Soprano vocals' highest harmonics will mostly be in the upper midrange,
and only a little into the low treble.
For a reasonable quantity of instrument harmonics into the high treble there is really only Violin and Piccolo for pitched instruments,
and cymbals and very small bells otherwise.
I find solo violin recordings useful to hear quality of tweeters,
{though if tweeters are faulty, or poor quality new, such will be audible with soprano vocals and various instruments}.
Do you have any recordings of unaccompanied violin playing ?
The obvious ones are Bach's Partitas and Sonatas for solo violin,
of which there are numerous Artists to choose from, albeit performance styles are very different between some Artists,
and some sound too technical and not musical to me.
The oldest recordings do not have extended treble harmonics, thus less useful.
I can list a few that I think are musical, because there is little point in buying something you cannot stand to listen to,
as that makes it harder to focus listening when trying to hear channel balance, etc ...
There are solo violin works by later Composers, and as usual I have forgotten most of them, except Bartok
... but you make not like his as his works are often jarring or dissonant, though I do not remember what his solo violin works sound like.
What can you stand to listen to ?
Do you know anyone who gets the USA magazine "audioXpress" ?
If so, have a look at the June 2012 issue for the article about measuring speakers in rooms that are not anechoic chambers, etc ...
I do not have access to a scanner, thus I cannot post it here.
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sba,
{if you are viewing before too long has passed}, have a look at that "audioXpress" article if you can.
Even though you have a Gate Time with your measurement device there is stuff in that article which may be of use to you.
Hi Nigel,
what amplifier models, vintage or modern, have you found to work well with Celestion 66 ?
either to moderate volume level in a small room,
or to high volume in a large room.
Some about your other recent points:
With 44kHz Digital, which all CDs are, there is no Square Wave when one gets to only 3kHz !
I would try to get flat response in tweeter to 20Khz to keep correct waveshape, including with CD's 44kHz sampling rate.
The plastic wrap outside a capacitor is not a Dielectric,
because it has voltage charge against only one side of it,
thus I do not know why removing the insulation sleeve would improve the sound,
but if the sleeve was loose, a tighter one would better damp vibrations in the metal case.
Can you post a Reference to whatever whoever is claiming about sleeveless capacitors ?
DNM's ideas and designs for Slit Foil caps and T caps are sensible.
The German Roedestein company had a similar design to DNM's T-cap years ago - pehaps still do ...
They are now Vishay-Roedestein.
So far as I know DNM was the first for Slit Foils.
Most of those ERSE non-polars are not wonderful as they have 10% and 6% Dissipation Factors,
which is better than was the case many years ago,
but 5% D.F. non-polars are readily available now, and there are 3% now also,
which I see at least a few of ERSE's are.
Also, the D.F. is only specified at 1kHz, though it is usually similar or better at lower frequencies,
but usually worse at higher frequencies, except for special design low-impedance caps such as a few companies manufacture now for use in those high frequency power supplies.
Celestion had the 22kHz notch filter in the early SL6, but took it out later because it also caused audible effect lower in the treble.
I do not remember when it was removed ... but possibly when they changed from the copper dome to aluminium dome tweeter,
as the resonance was higher in frequency with the Al dome,
sufficiently so to be not audible, thus no need for a filter.
The SL600 and SL700 I heard had very clear treble, thus not likely a high treble filter present.
I last heard them many years ago, thus cannot comment about how their treble sounds compared to the best current metal domes,
but I have heard some not good metal domes interim !
I prefer bi-wiring, when done well, but that will require a new terminal block be installed in 66,
which some owners may not want to do, thus I have not mentioned it in this thread.
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Hi Denny,
you have certainly done a lot of work with capacitor replacements !
and as such you deserve the good result you are now hearing.
I have printed that A28 schematic to study,
though immediately I saw something which had recently entered my mind to ask you,
thus before we proceed further:
Which amplifier did you use between signal generator and 66 when you did the measurements for the Celestion drive units,
especially when for the tweeters,
your A28 {before you recondioned it} ?
or a Valve/Tube amplifier ?
or your old Rotel Receiver ?
or a fairly new model Solid State amplifier in good condition ?
Also, do you hear a loud, or quiet, thump sound through the speakers when you switch on the A28, now that it has no Relay ?
Music to listen to tweeters:
Soprano vocals' highest harmonics will mostly be in the upper midrange,
and only a little into the low treble.
For a reasonable quantity of instrument harmonics into the high treble there is really only Violin and Piccolo for pitched instruments,
and cymbals and very small bells otherwise.
I find solo violin recordings useful to hear quality of tweeters,
{though if tweeters are faulty, or poor quality new, such will be audible with soprano vocals and various instruments}.
Do you have any recordings of unaccompanied violin playing ?
The obvious ones are Bach's Partitas and Sonatas for solo violin,
of which there are numerous Artists to choose from, albeit performance styles are very different between some Artists,
and some sound too technical and not musical to me.
The oldest recordings do not have extended treble harmonics, thus less useful.
I can list a few that I think are musical, because there is little point in buying something you cannot stand to listen to,
as that makes it harder to focus listening when trying to hear channel balance, etc ...
There are solo violin works by later Composers, and as usual I have forgotten most of them, except Bartok
... but you make not like his as his works are often jarring or dissonant, though I do not remember what his solo violin works sound like.
What can you stand to listen to ?
Do you know anyone who gets the USA magazine "audioXpress" ?
If so, have a look at the June 2012 issue for the article about measuring speakers in rooms that are not anechoic chambers, etc ...
I do not have access to a scanner, thus I cannot post it here.
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sba,
{if you are viewing before too long has passed}, have a look at that "audioXpress" article if you can.
Even though you have a Gate Time with your measurement device there is stuff in that article which may be of use to you.
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