The Caruso I put in yesterday was no diversion from the balancing of a speaker . It needs everything to be correct so as not to the diminish the ember of the original performance . One thing I do find with the 1903 Caruso is it makes my ears do what they do in real life . No idea how that is possible . My son noticed the same . I hate to get mixed up in the cult of Caruso . Problem is it would be stupid to say it's not hi fi thus I can not listen .
When I first heard 78's through correctly driven Quad 63's I found it possible to go into a time machine . If as little as possible distracts , the mind invents the missing octaves . Bass is one that usually is OK .
If 78's or ancient LP's sounds bad and the condition of the discs is OK it usually is things wrong that are universally wrong that makes it sound strange . Get the EQ right is a priority . The cheap way is to buy a Leak Varislope and build a buffer ( OPA 2604 ) .
An extreme example of little things being right is what I am listening to right now . My hairdresser brought her boom box made hi fi to repair . It has drive units seldom seen in the cheapest transistor radio these days . However they are not one million miles removed from mid range units . The boxes the thinnest MDF which gives them a chance ( not plastic ) . Two applications of PVA glue ( 10 % water ) as thin as possible ( not on the surround ) . Some Thomas Fast special foam offcuts I couldn't bring myself to throw away and bingo they sound OK . In fact the BBC R3 voice is unusually good . Listening now the Bach Toccata & F . Even that is reasonable . It probably has taken as long to write about it as do it ! This is not a universal fix . I found out that ripped valve radio speakers sounded better after this repair . The trick is to use as little as possible ( a Rizla paper to the cone rear to look almost like new when dry ) . Lets be clear this way of doping usually sounds better than the plastic cone speakers and has equally strengths where they do ( clout ) . I suspect 2 octaves of distrotion reduction with this boom box . The likelihood is 200 to 6 kHz now ( 100 to 10 kHz - 10 dB at a guess ) . Absolutely no tizz nor chestiness ( Thanks Thomas ) !
Poulenc . I went to a R3 recording of the Gloria a few months back . Bliss . The Organ concerto I heard in York Minster before the fire . His life a bit like mine . He stopped talking and did .
When I first heard 78's through correctly driven Quad 63's I found it possible to go into a time machine . If as little as possible distracts , the mind invents the missing octaves . Bass is one that usually is OK .
If 78's or ancient LP's sounds bad and the condition of the discs is OK it usually is things wrong that are universally wrong that makes it sound strange . Get the EQ right is a priority . The cheap way is to buy a Leak Varislope and build a buffer ( OPA 2604 ) .
An extreme example of little things being right is what I am listening to right now . My hairdresser brought her boom box made hi fi to repair . It has drive units seldom seen in the cheapest transistor radio these days . However they are not one million miles removed from mid range units . The boxes the thinnest MDF which gives them a chance ( not plastic ) . Two applications of PVA glue ( 10 % water ) as thin as possible ( not on the surround ) . Some Thomas Fast special foam offcuts I couldn't bring myself to throw away and bingo they sound OK . In fact the BBC R3 voice is unusually good . Listening now the Bach Toccata & F . Even that is reasonable . It probably has taken as long to write about it as do it ! This is not a universal fix . I found out that ripped valve radio speakers sounded better after this repair . The trick is to use as little as possible ( a Rizla paper to the cone rear to look almost like new when dry ) . Lets be clear this way of doping usually sounds better than the plastic cone speakers and has equally strengths where they do ( clout ) . I suspect 2 octaves of distrotion reduction with this boom box . The likelihood is 200 to 6 kHz now ( 100 to 10 kHz - 10 dB at a guess ) . Absolutely no tizz nor chestiness ( Thanks Thomas ) !
Poulenc . I went to a R3 recording of the Gloria a few months back . Bliss . The Organ concerto I heard in York Minster before the fire . His life a bit like mine . He stopped talking and did .
If the dome is held by screws the dome often is very easy to remove . If you find a soft surface which has the right shape use a pencil rubber to ease the dome out into the form . Pay attention to the coil staying in shape . If you preserve the ferro-fluid that damps the dome . It isn't always fitted . I would risk the minutest amount of candle wax on the dome back to prevent brake up modes . I suspect the micro mass will not reduce transient response . In fact a system pulled out of resonance is faster .
Best of luck .
Best of luck .
LT-Spice ; frequency bandwidth ; domes and cones ; turntables ;
G'day Denny ,
indeed it seems a good music festival you were fortunate to be able to attend !
As you have the LT-Spice , and if you have time available ,
it will still be interesting and likely useful to see the effect of the upper midrange crossover filter on the dome-mid.
I refer you to my Post #952 on Page 96 for the details of how to proceed.
*** *** ***
'ullo Nigel ,
I agree , that when the midrange is correct from a recording that for the bass and treble one's mind can invent the missing octaves ,
however that may only be for those of us who were conditioned since childhood by hearing only limited frequency range recordings and/or single cone wide-range driver loudspeaker systems.
Perhaps the children of the 1980s and since have heard more Bass and Treble , even if low quality through Boom-Box audio systems and similar in-car audio systems ,
and as such their brains are formed around hearing Bass and Treble , and even accentuated over the midrange ... as some of those replay systems are that their parents have owned.
I do not know how they hear - I know only how I hear , and how those people with whom I engage in comparative listening sessions seem to hear.
Very clever about putting a tiny amount of Wax on the back at the Apex of a metal dome !
I should have thought of that ...
With a few of the old Paper dome tweeters , when there was no damping material in the cavity behind , I put some soft Fibreglass wool.
That substantially reduced treble resonances.
I was reluctant to apply PVA to paper tweeters , because the addtional stiffness resulting can cause a larger break-up resonance around a narrow frequency band ,
and likely in the audible spectrum.
I have used PVA with very thin paper on the backs of mid and bass paper cone drivers for repairs to good effect.
Audibly much better than the entirely Plastic cone drivers are the recent very thin dual layer of plastic + metal that KEF used for their iQ* , XQ* , iQ** , XQ** series of loudspeakers ,
however KEF have now changed that for the new iQ*** series ,
and I do not know to what , nor have I heard any of this new series.
I should have expected a lover of Rim-drive , Idler-wheel turntables to state that a Belt is a primary problem ... and I do not entirely disagree ,
and perhaps with a very low vibration motor the Idler wheel will not feed significant vibration into the platter to either interfere with the stylus tracking the groove nor to modulate the rotational speed ,
however , one is going to need a notionally perfect circle idler wheel with perfect centre fixing to the motor shaft to commence to achieve stable speed ,
and as you do not like high mass platters , then how does one maintain sufficient Rotational Inertia for the multi-varying stylus' load drag through the vinyl to the platter to not modulate the speed of the platter ?
I have not been able to inspect the Loricraft Garrards 501 and 601 to see the quality of idler wheels , etc ...
nor have I heard either in use yet , however you will know what is in both , etc ... any comments about ?
G'day Denny ,
indeed it seems a good music festival you were fortunate to be able to attend !
As you have the LT-Spice , and if you have time available ,
it will still be interesting and likely useful to see the effect of the upper midrange crossover filter on the dome-mid.
I refer you to my Post #952 on Page 96 for the details of how to proceed.
*** *** ***
'ullo Nigel ,
I agree , that when the midrange is correct from a recording that for the bass and treble one's mind can invent the missing octaves ,
however that may only be for those of us who were conditioned since childhood by hearing only limited frequency range recordings and/or single cone wide-range driver loudspeaker systems.
Perhaps the children of the 1980s and since have heard more Bass and Treble , even if low quality through Boom-Box audio systems and similar in-car audio systems ,
and as such their brains are formed around hearing Bass and Treble , and even accentuated over the midrange ... as some of those replay systems are that their parents have owned.
I do not know how they hear - I know only how I hear , and how those people with whom I engage in comparative listening sessions seem to hear.
Very clever about putting a tiny amount of Wax on the back at the Apex of a metal dome !
I should have thought of that ...
With a few of the old Paper dome tweeters , when there was no damping material in the cavity behind , I put some soft Fibreglass wool.
That substantially reduced treble resonances.
I was reluctant to apply PVA to paper tweeters , because the addtional stiffness resulting can cause a larger break-up resonance around a narrow frequency band ,
and likely in the audible spectrum.
I have used PVA with very thin paper on the backs of mid and bass paper cone drivers for repairs to good effect.
Audibly much better than the entirely Plastic cone drivers are the recent very thin dual layer of plastic + metal that KEF used for their iQ* , XQ* , iQ** , XQ** series of loudspeakers ,
however KEF have now changed that for the new iQ*** series ,
and I do not know to what , nor have I heard any of this new series.
I should have expected a lover of Rim-drive , Idler-wheel turntables to state that a Belt is a primary problem ... and I do not entirely disagree ,
and perhaps with a very low vibration motor the Idler wheel will not feed significant vibration into the platter to either interfere with the stylus tracking the groove nor to modulate the rotational speed ,
however , one is going to need a notionally perfect circle idler wheel with perfect centre fixing to the motor shaft to commence to achieve stable speed ,
and as you do not like high mass platters , then how does one maintain sufficient Rotational Inertia for the multi-varying stylus' load drag through the vinyl to the platter to not modulate the speed of the platter ?
I have not been able to inspect the Loricraft Garrards 501 and 601 to see the quality of idler wheels , etc ...
nor have I heard either in use yet , however you will know what is in both , etc ... any comments about ?
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Some times the dome is held by three wedge shaped clips . A couple of flat blade screw drivers will ease them off . Rotate until free . I think a spoon will make a good form . The rubber refereed to is the tip of the pencil type . A new one would be best .
With a belt drive getting the power to the platter is the question . I have no objection to belt . Idler is hard work and has many almost impossible problems . Lenco's are very good . The idea of a stiff belt like a leader tape is practical . Verdier's smooth resistance via the oil also .
PVA for other than bass units seems to add too much mass except when the cheaper units .
I am hooking up my Magneplanar bass and Eminence 12 LTa mid top when I get a moment ( tax return next ) . I a looking for dynamics an verve more than accuracy . The idea is to estimate how the open baffle best be configured ( 4 x 2 ply , top 1/3 central or offset 12Lta + 15 inch bass QTs 1.2 to bottom 1/3 ) . A frame and cardboard at stage one . As I have highly accurate speakers I can tolerate what by physics alone can not be accurate as a party speaker ( It must play Caruso well ) . My friend John says at hi fi levels I might get a pleasant surprise from a drive unit looking bad by even transistor radio standards . <1 g balls ( 3 ) of cotton wool to tame the whizzer cone that has mid-range boost .
Eminence Beta-12LTA 12" Full-Range/PA Driver 290-409
With a belt drive getting the power to the platter is the question . I have no objection to belt . Idler is hard work and has many almost impossible problems . Lenco's are very good . The idea of a stiff belt like a leader tape is practical . Verdier's smooth resistance via the oil also .
PVA for other than bass units seems to add too much mass except when the cheaper units .
I am hooking up my Magneplanar bass and Eminence 12 LTa mid top when I get a moment ( tax return next ) . I a looking for dynamics an verve more than accuracy . The idea is to estimate how the open baffle best be configured ( 4 x 2 ply , top 1/3 central or offset 12Lta + 15 inch bass QTs 1.2 to bottom 1/3 ) . A frame and cardboard at stage one . As I have highly accurate speakers I can tolerate what by physics alone can not be accurate as a party speaker ( It must play Caruso well ) . My friend John says at hi fi levels I might get a pleasant surprise from a drive unit looking bad by even transistor radio standards . <1 g balls ( 3 ) of cotton wool to tame the whizzer cone that has mid-range boost .
Eminence Beta-12LTA 12" Full-Range/PA Driver 290-409
Re: post 952 - frequency bandwidth
The spoon idea is a beauty.
I've had a go with the LTSpice software to produce the plots 2 and 3 as per post 952 in this thread.
Unless I am intepreting the design incorrectly plot 1 will be a line at 0db. I don't know yet how to combine the plots so plots 2 & 3 are on separate charts. The circuits used to generate the plots are included. I've used separate components in the circuits for clarity. Can these be further refined?
The spoon idea is a beauty.
I've had a go with the LTSpice software to produce the plots 2 and 3 as per post 952 in this thread.
Unless I am intepreting the design incorrectly plot 1 will be a line at 0db. I don't know yet how to combine the plots so plots 2 & 3 are on separate charts. The circuits used to generate the plots are included. I've used separate components in the circuits for clarity. Can these be further refined?
LTSpice plots ; Tweeter Dome damping ; Open Baffle woofer
G'day Denny ,
Great stuff !
Both circuits as you have drawn and used are correct.
About the plots:
Likely the 0dB line is for a no filter prediction.
To test that , take out the 1.8 ohm resistor from the Input to the filter , and have no resistor there ,
unless your program requires a resistor with that capacitor , and if it does then put 0.10 ohm there.
Try the above with the 0.34mH + 3.9uF + 3.9 ohm circuit.
We can then see the action of the 1.8 ohm resistor.
The .34mH + 3.9uF + 3.9 ohm circuit simulation prediction for 5kHz is very close to what I have all along hoped for following my own estimations.
To try an alternate which will show us further , please do a simulation with 3.9uF + 2.7 ohms there ,
and with the 1.8 ohms in at the Input so that we can compare the new simulation directly to the original with the 1.8 ohms in.
The 4.2mH + 4.7uF circuit attenuates too much at 5kHz ,
and indicates that Celestion allowed for the specific Impedance characteristic of their driver at 5kHz better than was predicted by a self-proclaimed crossover designer here in the UK
who seems to trust only his particular computer program but seems to not know how to correctly program it.
Unfortunately he has ruined at least two Celestion owners' 66s , and seemingly ruined their enthusiasm for their 66s ,
and unfortunately he is still advertising his Service !
I have two ideas , of which one may work well for owners of the MD500 version of the dome
for samples which have a degree of rough frequency response around 5kHz or a little lower ,
however so as to not confuse readers of this thread , let us look at the two I have described above before we introduce any other variations.
***
After some time in my mind on the modification idea that Nigel described to damp a resonance in a metal dome tweeter I have remembered a potential problem if one uses Candle Wax.
For some metal domes , the metal itself is directly joined to the cylindrical Former around which the voice-coil is wound.
The voice-coil heats up when the music is playing , and will heat quite a lot with loud music , and more so with modern high-power tweeters that some users of play to very loud.
This heat will conduct from the coil into the former and into the dome , and thus soften the wax , and will melt it in a high-temperature application.
The molten wax , even though it is only a very small quantity ,
will in part flow into the gap between the voice-coil and the surrounding magnet pole ... and solidify there after the play session is finished.
Sure , it will melt again during the next session , but it will be where one does not want it - clogging the gap ,
and where if anything is useful it is only the specific chosen viscosity Ferro-fluid one wants there in some tweeters , and nothing there in others.
Better than candle wax to damp a metal dome will be a version of the Silicone adhesive filler that is used to seal around metal roof panels and metal pipes.
Ideally the formulation that is for outside roofing metal , because that is a high-temperature stable type , and very long life.
There are several formulae of these Silicone sealants.
Some are specifically for Plastics , some for Ceramics and Masonary { concrete cement } , some for Rubber , and some for Metals , etc ...
Most types will bond to several different types of materials , so look at all the alternates of them in a Hardware store and choose one that includes Metal.
If it will also bond to Ceramics and/or Masonary { concrete cement } that will be useful , because:
you will only need a very tiny quantity to make two tiny centre blob smears behind the domes of your two tweeters ,
and will have almost an entire tube remaining ...
which can be used if you buy the large low DCR inductors for your crossover's woofer filter that I have posted to Reggie about recently.
Use a Ceramics/Masonary bonding silicone to hold the inductors onto a board { of either wood or a suitable plastic I posted about for Reggie }
and tie the inductors tightly with Nylon cable ties through the board.
The Silicone will damp the inductors to reduce resonance which can otherwise modulate the magnetic field around the inductors to audible consequence.
These Silicone sealants cure to flexible , and can be cut with a sharp blade ,
thus the inductors can later be removed with no damage to their Ceramic insulation that other adhesives may grip too tightly to { or not grip to at all }.
***
'ullo Nigel ,
that Eminence woofer has too high Fs , 50 Hz , to be useful for low bass.
There are some open-baffle enthusiasts who use recent and current model Eminence Pro woofers in the application you want to try.
I have forgotten the particular Model they use , but I will find it and post that here then.
For now , if you are looking through the Eminence catalog ,
choose a woofer that has Fs at 40 Hz or lower in frequency ... down to 30 Hz will be audibly useful.
For its Qt to be useful for Open-baffle with no Equalizer circuit needed , choose a model with Qt between 0.9 and 1.2 .
The lower the Fs , the larger the Qt can be with little audible degredation.
You seem to like under-damped loudspeakers , but anything with larger Q than a 30Hz/Qt 1.2 or 40Hz/Qt 1.0 will really resonate a lot with low bass !
G'day Denny ,
Great stuff !
Both circuits as you have drawn and used are correct.
About the plots:
Likely the 0dB line is for a no filter prediction.
To test that , take out the 1.8 ohm resistor from the Input to the filter , and have no resistor there ,
unless your program requires a resistor with that capacitor , and if it does then put 0.10 ohm there.
Try the above with the 0.34mH + 3.9uF + 3.9 ohm circuit.
We can then see the action of the 1.8 ohm resistor.
The .34mH + 3.9uF + 3.9 ohm circuit simulation prediction for 5kHz is very close to what I have all along hoped for following my own estimations.
To try an alternate which will show us further , please do a simulation with 3.9uF + 2.7 ohms there ,
and with the 1.8 ohms in at the Input so that we can compare the new simulation directly to the original with the 1.8 ohms in.
The 4.2mH + 4.7uF circuit attenuates too much at 5kHz ,
and indicates that Celestion allowed for the specific Impedance characteristic of their driver at 5kHz better than was predicted by a self-proclaimed crossover designer here in the UK
who seems to trust only his particular computer program but seems to not know how to correctly program it.
Unfortunately he has ruined at least two Celestion owners' 66s , and seemingly ruined their enthusiasm for their 66s ,
and unfortunately he is still advertising his Service !
I have two ideas , of which one may work well for owners of the MD500 version of the dome
for samples which have a degree of rough frequency response around 5kHz or a little lower ,
however so as to not confuse readers of this thread , let us look at the two I have described above before we introduce any other variations.
***
After some time in my mind on the modification idea that Nigel described to damp a resonance in a metal dome tweeter I have remembered a potential problem if one uses Candle Wax.
For some metal domes , the metal itself is directly joined to the cylindrical Former around which the voice-coil is wound.
The voice-coil heats up when the music is playing , and will heat quite a lot with loud music , and more so with modern high-power tweeters that some users of play to very loud.
This heat will conduct from the coil into the former and into the dome , and thus soften the wax , and will melt it in a high-temperature application.
The molten wax , even though it is only a very small quantity ,
will in part flow into the gap between the voice-coil and the surrounding magnet pole ... and solidify there after the play session is finished.
Sure , it will melt again during the next session , but it will be where one does not want it - clogging the gap ,
and where if anything is useful it is only the specific chosen viscosity Ferro-fluid one wants there in some tweeters , and nothing there in others.
Better than candle wax to damp a metal dome will be a version of the Silicone adhesive filler that is used to seal around metal roof panels and metal pipes.
Ideally the formulation that is for outside roofing metal , because that is a high-temperature stable type , and very long life.
There are several formulae of these Silicone sealants.
Some are specifically for Plastics , some for Ceramics and Masonary { concrete cement } , some for Rubber , and some for Metals , etc ...
Most types will bond to several different types of materials , so look at all the alternates of them in a Hardware store and choose one that includes Metal.
If it will also bond to Ceramics and/or Masonary { concrete cement } that will be useful , because:
you will only need a very tiny quantity to make two tiny centre blob smears behind the domes of your two tweeters ,
and will have almost an entire tube remaining ...
which can be used if you buy the large low DCR inductors for your crossover's woofer filter that I have posted to Reggie about recently.
Use a Ceramics/Masonary bonding silicone to hold the inductors onto a board { of either wood or a suitable plastic I posted about for Reggie }
and tie the inductors tightly with Nylon cable ties through the board.
The Silicone will damp the inductors to reduce resonance which can otherwise modulate the magnetic field around the inductors to audible consequence.
These Silicone sealants cure to flexible , and can be cut with a sharp blade ,
thus the inductors can later be removed with no damage to their Ceramic insulation that other adhesives may grip too tightly to { or not grip to at all }.
***
'ullo Nigel ,
that Eminence woofer has too high Fs , 50 Hz , to be useful for low bass.
There are some open-baffle enthusiasts who use recent and current model Eminence Pro woofers in the application you want to try.
I have forgotten the particular Model they use , but I will find it and post that here then.
For now , if you are looking through the Eminence catalog ,
choose a woofer that has Fs at 40 Hz or lower in frequency ... down to 30 Hz will be audibly useful.
For its Qt to be useful for Open-baffle with no Equalizer circuit needed , choose a model with Qt between 0.9 and 1.2 .
The lower the Fs , the larger the Qt can be with little audible degredation.
You seem to like under-damped loudspeakers , but anything with larger Q than a 30Hz/Qt 1.2 or 40Hz/Qt 1.0 will really resonate a lot with low bass !
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More LTSpice plots
I'll try putting the new plots inside a .PDF file. Also included is a plot of the combined 1+2+3 from the previous post.
View attachment Post 1007.pdf
I use that high temp silicone around a metal flue. It is very heat resistent. I measured the damaged tweeter and it looked bad so I tracked down a replacement but will attempt a repair if I can get it apart.
I'll try putting the new plots inside a .PDF file. Also included is a plot of the combined 1+2+3 from the previous post.
View attachment Post 1007.pdf
I use that high temp silicone around a metal flue. It is very heat resistent. I measured the damaged tweeter and it looked bad so I tracked down a replacement but will attempt a repair if I can get it apart.
Looking for the Optimum resistance
Great stuff Denny !
First we see that the 1.8 ohm input resistor attenuates the signal by a fraction more than 1dB ,
thus I think it likely that when the lower DCR inductors are used in the woofer filter this 1.8 ohm resistor will not be needed in the midsrange filter.
The resistor in Series with the 3.9uF capacitor will still be needed , because that resistor reduces Resonance.
See in the 2.7 ohm versus 3.9 ohm plots:
Normally one would expect that when less Impedance , 3.9uF + 2.7 ohm , in Parallel with the driver ,
the Series inductor , 3.4mH , would filter more of the treble off ,
but here we see the 3.9uF + 2.7 ohms filters less , and the 3.9uF + 3.9 ohm filters more ...
See the wide , banana shaped area between the 2.7 ohm and 3.9 ohm plots.
That shows the broad-band resonance caused by the 3.9uF cap resonating with the .179mH inductance of the driver's voice-coil
- broad-band because the 8.97 ohm of the driver's voice-coil has reduced the Q of the resonance
-{ but plays the resonance out through the dome to the listener }.
The 3.9 ohms reduces that Q further , more so than 2.7 ohms , { and both reduce the resonance before it can be played by the dome }.
One might then think that the larger Resistance in Series with the 3.9uF cap the more the Q of the resonance is damped ... yes ...
BUT , when the Resistance there gets too large the Impedance of that Parallel arm will be high enough to reduce the amount of filtering the 3.4mH inductor can do.
What is the optimum resistance for that arm to reduce the Q of the resonance but not reduce the filtering off of the treble above the crossover point ?
From those two plots we can only conclude that the optimum is larger than 2.7 ohms ,
and that 3.9 ohms is closer to the optimum than 2.7 .
Let us try to zoom in on the optimum , but with regard to the limited resistance values readily available in 5 watts.
{ 4.3 ohms in 5 watts is only available from one seller.}
Denny , please plot two more for comparison.
Have the 1.8 ohms input in the circuit.
Use 3.4mH for the inductor and 3.9uF for the capacitor , so as to be the same as for the 2.7 and 3.9 ohms circuits ,
but plot with 3.3 ohms and 4.7 ohms as alternates for the resistor ,
because I do not know which side of 3.9 will be the optimum resistance.
The optimum resistance may be larger than 4.7 ohms , such as 5.1 or 5.6 , 6.2 , 6.8 even ,
but 7.5 or 8.2 is unlikely because when it gets close to the 8.97 ohm effective resistance of the driver's voice-coil the effect of the filter will be less.
If you don't get a maximum filtering with 3.3 ohms , then try some values larger than 4.7 , but only if 4.7 filters more than 3.9 did.
Great stuff Denny !
First we see that the 1.8 ohm input resistor attenuates the signal by a fraction more than 1dB ,
thus I think it likely that when the lower DCR inductors are used in the woofer filter this 1.8 ohm resistor will not be needed in the midsrange filter.
The resistor in Series with the 3.9uF capacitor will still be needed , because that resistor reduces Resonance.
See in the 2.7 ohm versus 3.9 ohm plots:
Normally one would expect that when less Impedance , 3.9uF + 2.7 ohm , in Parallel with the driver ,
the Series inductor , 3.4mH , would filter more of the treble off ,
but here we see the 3.9uF + 2.7 ohms filters less , and the 3.9uF + 3.9 ohm filters more ...
See the wide , banana shaped area between the 2.7 ohm and 3.9 ohm plots.
That shows the broad-band resonance caused by the 3.9uF cap resonating with the .179mH inductance of the driver's voice-coil
- broad-band because the 8.97 ohm of the driver's voice-coil has reduced the Q of the resonance
-{ but plays the resonance out through the dome to the listener }.
The 3.9 ohms reduces that Q further , more so than 2.7 ohms , { and both reduce the resonance before it can be played by the dome }.
One might then think that the larger Resistance in Series with the 3.9uF cap the more the Q of the resonance is damped ... yes ...
BUT , when the Resistance there gets too large the Impedance of that Parallel arm will be high enough to reduce the amount of filtering the 3.4mH inductor can do.
What is the optimum resistance for that arm to reduce the Q of the resonance but not reduce the filtering off of the treble above the crossover point ?
From those two plots we can only conclude that the optimum is larger than 2.7 ohms ,
and that 3.9 ohms is closer to the optimum than 2.7 .
Let us try to zoom in on the optimum , but with regard to the limited resistance values readily available in 5 watts.
{ 4.3 ohms in 5 watts is only available from one seller.}
Denny , please plot two more for comparison.
Have the 1.8 ohms input in the circuit.
Use 3.4mH for the inductor and 3.9uF for the capacitor , so as to be the same as for the 2.7 and 3.9 ohms circuits ,
but plot with 3.3 ohms and 4.7 ohms as alternates for the resistor ,
because I do not know which side of 3.9 will be the optimum resistance.
The optimum resistance may be larger than 4.7 ohms , such as 5.1 or 5.6 , 6.2 , 6.8 even ,
but 7.5 or 8.2 is unlikely because when it gets close to the 8.97 ohm effective resistance of the driver's voice-coil the effect of the filter will be less.
If you don't get a maximum filtering with 3.3 ohms , then try some values larger than 4.7 , but only if 4.7 filters more than 3.9 did.
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Alan,
This is a plot for the mid range circuit with a range of resistances from 2.7 to 8.2:
Just for the record the basic circuit for the LTSpice model is the first circuit in post #1006 (circuitforplot2.jpg). Note I'm using 0.34mH in series with the mid unit not 3.4mH as you have written (L4).
This is a plot for the mid range circuit with a range of resistances from 2.7 to 8.2:
Just for the record the basic circuit for the LTSpice model is the first circuit in post #1006 (circuitforplot2.jpg). Note I'm using 0.34mH in series with the mid unit not 3.4mH as you have written (L4).
other useful variations for the circuit
Good one Denny ,
you have spotted my mistake:- 3.4 instead of .34mH - thankyou for identifying that !
Interesting results , and I was about to post that it may not be possible for the LTSpice to correctly model exactly what happens in a real-time Reactive circuit ,
but then I remembered a related matter applicable to that type of circuit which I had forgotten ... despite having used it once myself !!
Taking the above into account , all interested readers note in Denny's plots that for resistances larger than 4.7 ohm the Right end of the plot starts to curve upwards , that is lessens its downward bend.
This indicates the resistor is no longer contributing much to reducing the resonance of the output ,
but has now in combination with the 3.9uF cap effectively becoming a Zobel circuit opposing the Inductive Reactance of the mid-driver
and reducing the Load seen by the .34mH inductor to closer to resistive ,
and in particular somewhat lower resistive than Celestion intended for this filter.
As result of the Zobel action and the reduced Load the filter sees , the crossover point has been lowered in frequency , successively for each resistance larger than the 4.7 ohm shown.
As the 4.7 ohm plot is mostly so close to a straight line sloping downwards , there is effectively no resonance in the upper midrange.
Between 3.9 and 4.7 ohm may cause closer to a straight line through what was the resonant area ,
thus if you are buying from Sonicraft in the USA you could buy 4.3 ohm to use -{ no other sellers have 4.3 ohm in a quality 5 watt resistor }.
The Zobel action is further confirmed by the lesser Phase Angle shown in the plots for the higher resistive circuits than for the lower resistive circuits.
Fortunately , 3.9 ohm shows the best result at 5kHz for the Celestion specified 5kHz crossover point ,
so lets keep 3.9 ohm there , unless your particular sample of MF or MD 500 needs greater or lesser attenuation around the 5 kHz area.
Reggie ,
if your components have arrived , I recommend you do not install a 2.7 ohm resistor there.
Start with 3.9 ohm , or 3.3 ohm if you did not buy 3.9 .
Denny ,
there are two more variations of the circuit that can be useful ,
which-ever depending on whether samples of the 500 dome have deteriorated to some break-up in the region a little higher in frequency than 5kHz ,
or at 5kHz and and a little lower in frequency.
Remember , sba's plots taken from 6 samples , { two plots later in the thread than the first four } , showed several variations for these old domes ,
as did the two plots taken of WayneSwann's samples , and also the four you did near-fields for.
Thus , if this is interesting to you Denny , please plot the following:
Keep the 1.8 ohm input resistor and the 3.9 ohm output resistor in circuit , and keep all else , and change only as follows:
One circuit: use 0.34mH with 4.7uF as the output capacitor.
Other circuit: use 0.42mH , with 3.9uF as the output capacitor
{ and that includes the 3.9 ohm resistor for both circuits }.
Good one Denny ,
you have spotted my mistake:- 3.4 instead of .34mH - thankyou for identifying that !
Interesting results , and I was about to post that it may not be possible for the LTSpice to correctly model exactly what happens in a real-time Reactive circuit ,
but then I remembered a related matter applicable to that type of circuit which I had forgotten ... despite having used it once myself !!
Taking the above into account , all interested readers note in Denny's plots that for resistances larger than 4.7 ohm the Right end of the plot starts to curve upwards , that is lessens its downward bend.
This indicates the resistor is no longer contributing much to reducing the resonance of the output ,
but has now in combination with the 3.9uF cap effectively becoming a Zobel circuit opposing the Inductive Reactance of the mid-driver
and reducing the Load seen by the .34mH inductor to closer to resistive ,
and in particular somewhat lower resistive than Celestion intended for this filter.
As result of the Zobel action and the reduced Load the filter sees , the crossover point has been lowered in frequency , successively for each resistance larger than the 4.7 ohm shown.
As the 4.7 ohm plot is mostly so close to a straight line sloping downwards , there is effectively no resonance in the upper midrange.
Between 3.9 and 4.7 ohm may cause closer to a straight line through what was the resonant area ,
thus if you are buying from Sonicraft in the USA you could buy 4.3 ohm to use -{ no other sellers have 4.3 ohm in a quality 5 watt resistor }.
The Zobel action is further confirmed by the lesser Phase Angle shown in the plots for the higher resistive circuits than for the lower resistive circuits.
Fortunately , 3.9 ohm shows the best result at 5kHz for the Celestion specified 5kHz crossover point ,
so lets keep 3.9 ohm there , unless your particular sample of MF or MD 500 needs greater or lesser attenuation around the 5 kHz area.
Reggie ,
if your components have arrived , I recommend you do not install a 2.7 ohm resistor there.
Start with 3.9 ohm , or 3.3 ohm if you did not buy 3.9 .
Denny ,
there are two more variations of the circuit that can be useful ,
which-ever depending on whether samples of the 500 dome have deteriorated to some break-up in the region a little higher in frequency than 5kHz ,
or at 5kHz and and a little lower in frequency.
Remember , sba's plots taken from 6 samples , { two plots later in the thread than the first four } , showed several variations for these old domes ,
as did the two plots taken of WayneSwann's samples , and also the four you did near-fields for.
Thus , if this is interesting to you Denny , please plot the following:
Keep the 1.8 ohm input resistor and the 3.9 ohm output resistor in circuit , and keep all else , and change only as follows:
One circuit: use 0.34mH with 4.7uF as the output capacitor.
Other circuit: use 0.42mH , with 3.9uF as the output capacitor
{ and that includes the 3.9 ohm resistor for both circuits }.
Last edited:
Hello Alan (et al).
Received the last of my parts Thursday so will start assembly next week - after I source some ply. I note your advice about the resistors, thank you. I have been thinking of lifting my speakers up a bit to get the tweeter(s) at ear level (I am 194cm tall)(fortunately I usually sit down to listen heh heh) so my idea is to build small stands that will not only support the Celestions but also (eventually) contain the finished crossovers. Have you any thoughts on this..heat/vibration etc.??
Regards
Reggie
Received the last of my parts Thursday so will start assembly next week - after I source some ply. I note your advice about the resistors, thank you. I have been thinking of lifting my speakers up a bit to get the tweeter(s) at ear level (I am 194cm tall)(fortunately I usually sit down to listen heh heh) so my idea is to build small stands that will not only support the Celestions but also (eventually) contain the finished crossovers. Have you any thoughts on this..heat/vibration etc.??
Regards
Reggie
LTSpice plots , + interim to Reggie
Interesting results Denny ...
First I will remind readers of my initial statement about this LTSpice simulation - that is it is only accurate at 5kHz ,
because below 5kHz the driver's Inductance is larger and its Resistance is smaller ,
and above 5kHz the driver's Inductance is smaller and its Resistance is larger.
As result of the above , the slopes of the 2 plots Denny has above will not be Parallel when measured with an MD or MF 500 mid-dome ,
however the difference will be as shown at the 5kHz point.
In reality with a mid-dome the result with .42mH + 3.9uF will be a slightly gentler slope ,
and the result with .34mH + 4.7uF will be a slightly steeper slope.
What the LTSpice result does demonstrate is that 0.42mH is too much inductance for even the possibly most deteriorated peaky sample of a Celestion 500 dome.
At most I think a standard available 0.39mH inductor would be sufficient for such.
The 0.34mH + 4.7uF result will be useful for 500 domes that may be sagging a little in output at and below 5kHz and breaking up at frequencies higher than 5kHz.
Denny ,
so that we can clearly compare the 2 most useful modification circuits ,
please post a File with these 2 together , because each is on a separate page in this thread , so a comparison plots' file will be useful for:
0.34mH + 3.9uF + 4.7 ohm
0.34mH + 4.7uF + 3.9 ohm
If you want to see the differences between those and the circuit I have recommended in the past ,
and if you can get 3 colours to work in the File as before ,
then include the 0.34mH + 3.9uF + 3.9 ohm circuit also.
Include the 1.8 ohm input resistor with all 3 circuits.
*** *** ***
G'day Reggie ,
I read you have noticed what I've now found about the output resistor's action in the mid-dome filter ,
thus I apologize if I mislead you into buying a resistance for that which may not be optimum ,
however , if you bought only one option of resistor for there , then you may as well use it and listen to the result ,
then report here the audible effect of upper midrange/lower treble -
- both yours' and your wife's findings with favorite Vocals' recordings.
About height of stands:
I think the optimum height to listen at will be with ears at the half-way point between mid-dome and tweeter , or very slightly above the half-way point ,
because the 5kHz region output from each will add together better there than at tweeter height.
Do not worry that being slightly off-axis to the tweeter may cause slightly less of the highest treble frequencies to be directed to your ears ,
because the Hiquphon tweeter being only 19mm diameter will have good off-axis response to higher treble frequencies than your ears can now hear ,
and your wife may not want to hear the very slightly louder output around 16kHz that listening directly on-axis to tweeter may allow ,
and I think it likely she will hear any discontinuity in the sound around 5kHz if not listening on the optimum axis , or close to that.
Best for stands , and particually for heavy loudspeakers , are 3 legs ...
and simplest to get right or as close as possible to by a DIYer is to make from wood.
Thus I can describe how to for wooden uprights of about 3" to 4'' wide and 1.5" to 2.5" thick.
All 3 legs do not need to be same thickness nor width , and there will be less co-incident resonance in the stands if all 3 legs are not equal mass.
For neatness , one has 2 legs in the front of equal dimensions , and a slightly thicker , wider one at the back ...
and that arrangement will be distributing the loudspeaker's weight quite well.
Work out a the suitable height of stand you need , then post that here if you want me to describe further how to make simple wooden stands.
You will need to be able to use a Saw , mostly , and a sharp Chisel for some sections.
The parts can be glued together , and with long screws to hold all together whilst the glue is setting.
The screws through the wood will prevent the glue joints breaking if the stands happen to be accidentally dropped
and land with any force at any impact critical angle.
If you can find an attractive grain wood , then it can look nice stained with a suitable colour.
Plainer or ugly wood can be painted with a matt-finish , suitable colour paint.
Soft wood such as Pine is fine , and is much easier to cut and chisel than hard wood.
There will be 2 cross brace panels in each stand , for which you can use Pine plank between 0.75" <--> 1" thick ,
or same thickness of Plywood.
Area of each of these shelf-type cross braces will be not larger than the area of the bottom of the loudspeaker enclosure.
Yes , the crossover for each loudspeaker could be put on one of the shelf braces in the stand underneath.
Interesting results Denny ...
First I will remind readers of my initial statement about this LTSpice simulation - that is it is only accurate at 5kHz ,
because below 5kHz the driver's Inductance is larger and its Resistance is smaller ,
and above 5kHz the driver's Inductance is smaller and its Resistance is larger.
As result of the above , the slopes of the 2 plots Denny has above will not be Parallel when measured with an MD or MF 500 mid-dome ,
however the difference will be as shown at the 5kHz point.
In reality with a mid-dome the result with .42mH + 3.9uF will be a slightly gentler slope ,
and the result with .34mH + 4.7uF will be a slightly steeper slope.
What the LTSpice result does demonstrate is that 0.42mH is too much inductance for even the possibly most deteriorated peaky sample of a Celestion 500 dome.
At most I think a standard available 0.39mH inductor would be sufficient for such.
The 0.34mH + 4.7uF result will be useful for 500 domes that may be sagging a little in output at and below 5kHz and breaking up at frequencies higher than 5kHz.
Denny ,
so that we can clearly compare the 2 most useful modification circuits ,
please post a File with these 2 together , because each is on a separate page in this thread , so a comparison plots' file will be useful for:
0.34mH + 3.9uF + 4.7 ohm
0.34mH + 4.7uF + 3.9 ohm
If you want to see the differences between those and the circuit I have recommended in the past ,
and if you can get 3 colours to work in the File as before ,
then include the 0.34mH + 3.9uF + 3.9 ohm circuit also.
Include the 1.8 ohm input resistor with all 3 circuits.
*** *** ***
G'day Reggie ,
I read you have noticed what I've now found about the output resistor's action in the mid-dome filter ,
thus I apologize if I mislead you into buying a resistance for that which may not be optimum ,
however , if you bought only one option of resistor for there , then you may as well use it and listen to the result ,
then report here the audible effect of upper midrange/lower treble -
- both yours' and your wife's findings with favorite Vocals' recordings.
About height of stands:
I think the optimum height to listen at will be with ears at the half-way point between mid-dome and tweeter , or very slightly above the half-way point ,
because the 5kHz region output from each will add together better there than at tweeter height.
Do not worry that being slightly off-axis to the tweeter may cause slightly less of the highest treble frequencies to be directed to your ears ,
because the Hiquphon tweeter being only 19mm diameter will have good off-axis response to higher treble frequencies than your ears can now hear ,
and your wife may not want to hear the very slightly louder output around 16kHz that listening directly on-axis to tweeter may allow ,
and I think it likely she will hear any discontinuity in the sound around 5kHz if not listening on the optimum axis , or close to that.
Best for stands , and particually for heavy loudspeakers , are 3 legs ...
and simplest to get right or as close as possible to by a DIYer is to make from wood.
Thus I can describe how to for wooden uprights of about 3" to 4'' wide and 1.5" to 2.5" thick.
All 3 legs do not need to be same thickness nor width , and there will be less co-incident resonance in the stands if all 3 legs are not equal mass.
For neatness , one has 2 legs in the front of equal dimensions , and a slightly thicker , wider one at the back ...
and that arrangement will be distributing the loudspeaker's weight quite well.
Work out a the suitable height of stand you need , then post that here if you want me to describe further how to make simple wooden stands.
You will need to be able to use a Saw , mostly , and a sharp Chisel for some sections.
The parts can be glued together , and with long screws to hold all together whilst the glue is setting.
The screws through the wood will prevent the glue joints breaking if the stands happen to be accidentally dropped
and land with any force at any impact critical angle.
If you can find an attractive grain wood , then it can look nice stained with a suitable colour.
Plainer or ugly wood can be painted with a matt-finish , suitable colour paint.
Soft wood such as Pine is fine , and is much easier to cut and chisel than hard wood.
There will be 2 cross brace panels in each stand , for which you can use Pine plank between 0.75" <--> 1" thick ,
or same thickness of Plywood.
Area of each of these shelf-type cross braces will be not larger than the area of the bottom of the loudspeaker enclosure.
Yes , the crossover for each loudspeaker could be put on one of the shelf braces in the stand underneath.
Last edited:
Well if this isn't coming back from the dead I don't know what is.
Back in 2009 I posted about possibly repairing a set of studio 66's v2's... then I went and got into a motorcycle accident, after nearly dying, and spending nine months in the hospital,and almost 4 years of recovery, I'm back! And looking to restore the 66'rs to their prior glory.
I have ordered a bunch of caps already, and I have 4 hF 2000's(possibly needing repair, but I am pretty much starting from scratch.
What I need is a diagram of the layout of the crossover along with any updates that would that would be necessary to complete them. I have read mention of resistors?
Also wondering what type of wiring I should be using in order to get them back to great condition.
I have a soldering station and consider myself to be a reasonably good solderer. I hope to work on these throughout the winter although I have a few other projects as well (1998 bmw m3 vert resto)
It is great to hear that this thread is still active though.
Keep up the great work fellas!!!
Back in 2009 I posted about possibly repairing a set of studio 66's v2's... then I went and got into a motorcycle accident, after nearly dying, and spending nine months in the hospital,and almost 4 years of recovery, I'm back! And looking to restore the 66'rs to their prior glory.
I have ordered a bunch of caps already, and I have 4 hF 2000's(possibly needing repair, but I am pretty much starting from scratch.
What I need is a diagram of the layout of the crossover along with any updates that would that would be necessary to complete them. I have read mention of resistors?
Also wondering what type of wiring I should be using in order to get them back to great condition.
I have a soldering station and consider myself to be a reasonably good solderer. I hope to work on these throughout the winter although I have a few other projects as well (1998 bmw m3 vert resto)
It is great to hear that this thread is still active though.
Keep up the great work fellas!!!
replies to 1015 , 1016 , and alternate LTSpice plots to try
Thankyou Denny ...
For the Celestion original and the 2 modification circuits the variations can be clearly seen , and those can be applied to variations in samples of the mid-domes -
- see Page 50 , #499 , for the variations between sba's 4 samples.
Very interesting is your particular modified circuit , where the presence of the Parallel connected 82 ohm resistor has removed the resonance that 2.7 ohm allowed ,
and increases the phase angle of the filter , which will change the output level where the mid-dome and tweeter add ,
-{ which seems to be a little above 5kHz , perhaps closer to 6kHz from some of sba's other plots }.
Thus you have evidence now of the effect you heard !
{ the audible difference lower in the midrange around the 500 Hz crossover point is not shown , and we'd have to change some things to show that }.
{ The slightly larger components at .35mH and 4.0uF caused the slightly lower output at 5kHz than the Reference .39 + 3.9 plot ,
and actually it is a slightly lower effective crossover frequency with the .35 + 4.0 .}
***
To date we have been looking only at the electrical components of the filter's effect ,
however if anyone has remembered at least two of my much earlier posts in this thread ,
the actual filter includes the Impedance variations of the mid-dome and the rolloffs at each end of its bandwidth.
To show better what is actually occuring at 5kHz let us now include the driver's voice-coil Inductance in the filter ,
and measure the output across the voice-coil's Resistance only.
Denny ,
use the same circuit components as before to as far as your numbered L4 , and change as follows:
L4 ; C4 + R5 ; L6 at 0.179mH , draw as a T shaped output filter ,
that is with each L at either side of the top of the T , and C4 + R5 as the leg of the T.
R7 , at 8.97 ohm , is now to be the Output.
Thus configure your LTSpice to measure across R7 only.
Draw that circuit and post it here so that I can be sure you have it correct.
Plot as follows the same 3 as your previous above with:
3.9uf + 3.9 ohm ; 3.9uF + 4.7 ohm ; 4.7uF + 3.9 ohm , all with L6 as 0.179mH ,
and measure across R7 at 8.97 ohm.
Expand the Vertical Axis scale back to that of your first plot , because I think there will be a larger Phase Angle for each with this measurement ,
and we do want to see it on the plot.
If you want to include your specific mod with the 82 ohm , then observe carefully where to connect it in the filter -
- from the junction of the other 3 components at the top of the T , and other end to the bottom of the leg of the T.
*** *** ***
'ullo G.O.A.T.145 ,
I remember your unusual name from previously in this thread , and I did reply to your Post there.
I am very happy that you have survived your accident !
You are "restored" and now your 66s are to be !!
There are photos of an opened HF2000 on Page 49 in #483 , if such may assist you.
There may have been another opened HF2000 later in this thread ... I have forgotten.
There are several diagrams of the crossover , each with variations of the capacitor and resistor values.
To advise you which one to use , post here the exact capacitor values you have ordered.
We have been further working on one of the resistor values on this page and the previous page.
I will list all the resistors after you post the caps you have ordered ... so do that AFTER you receive them and check what is printed on each of them.
Also , what Brand and type did you order ?
For the wiring , use the original Celestion wire , as it is good quality for this application , and better than low priced modern wires.
Thankyou Denny ...
For the Celestion original and the 2 modification circuits the variations can be clearly seen , and those can be applied to variations in samples of the mid-domes -
- see Page 50 , #499 , for the variations between sba's 4 samples.
Very interesting is your particular modified circuit , where the presence of the Parallel connected 82 ohm resistor has removed the resonance that 2.7 ohm allowed ,
and increases the phase angle of the filter , which will change the output level where the mid-dome and tweeter add ,
-{ which seems to be a little above 5kHz , perhaps closer to 6kHz from some of sba's other plots }.
Thus you have evidence now of the effect you heard !
{ the audible difference lower in the midrange around the 500 Hz crossover point is not shown , and we'd have to change some things to show that }.
{ The slightly larger components at .35mH and 4.0uF caused the slightly lower output at 5kHz than the Reference .39 + 3.9 plot ,
and actually it is a slightly lower effective crossover frequency with the .35 + 4.0 .}
***
To date we have been looking only at the electrical components of the filter's effect ,
however if anyone has remembered at least two of my much earlier posts in this thread ,
the actual filter includes the Impedance variations of the mid-dome and the rolloffs at each end of its bandwidth.
To show better what is actually occuring at 5kHz let us now include the driver's voice-coil Inductance in the filter ,
and measure the output across the voice-coil's Resistance only.
Denny ,
use the same circuit components as before to as far as your numbered L4 , and change as follows:
L4 ; C4 + R5 ; L6 at 0.179mH , draw as a T shaped output filter ,
that is with each L at either side of the top of the T , and C4 + R5 as the leg of the T.
R7 , at 8.97 ohm , is now to be the Output.
Thus configure your LTSpice to measure across R7 only.
Draw that circuit and post it here so that I can be sure you have it correct.
Plot as follows the same 3 as your previous above with:
3.9uf + 3.9 ohm ; 3.9uF + 4.7 ohm ; 4.7uF + 3.9 ohm , all with L6 as 0.179mH ,
and measure across R7 at 8.97 ohm.
Expand the Vertical Axis scale back to that of your first plot , because I think there will be a larger Phase Angle for each with this measurement ,
and we do want to see it on the plot.
If you want to include your specific mod with the 82 ohm , then observe carefully where to connect it in the filter -
- from the junction of the other 3 components at the top of the T , and other end to the bottom of the leg of the T.
*** *** ***
'ullo G.O.A.T.145 ,
I remember your unusual name from previously in this thread , and I did reply to your Post there.
I am very happy that you have survived your accident !
You are "restored" and now your 66s are to be !!
There are photos of an opened HF2000 on Page 49 in #483 , if such may assist you.
There may have been another opened HF2000 later in this thread ... I have forgotten.
There are several diagrams of the crossover , each with variations of the capacitor and resistor values.
To advise you which one to use , post here the exact capacitor values you have ordered.
We have been further working on one of the resistor values on this page and the previous page.
I will list all the resistors after you post the caps you have ordered ... so do that AFTER you receive them and check what is printed on each of them.
Also , what Brand and type did you order ?
For the wiring , use the original Celestion wire , as it is good quality for this application , and better than low priced modern wires.
Last edited:
Correct circuit point , but not L4 value
G'day Denny ,
the Circuit is correct , and yes , measure the output from the point you marked " Mid " across the 8.97 ohm resistor R7 ,
as that is now the driver load for this test.
I see you have L4 at 0.42mH.
Let's forget 0.42mH , as it is too large to likely be useful to anyone here.
Use 0.34mH for L4 , as that is the middle/average of what has been found in 66s to date.
If you want to do a plot with your 82 ohm in circuit , connect it from the top of C4 to the bottom of R5.
G'day Denny ,
the Circuit is correct , and yes , measure the output from the point you marked " Mid " across the 8.97 ohm resistor R7 ,
as that is now the driver load for this test.
I see you have L4 at 0.42mH.
Let's forget 0.42mH , as it is too large to likely be useful to anyone here.
Use 0.34mH for L4 , as that is the middle/average of what has been found in 66s to date.
If you want to do a plot with your 82 ohm in circuit , connect it from the top of C4 to the bottom of R5.
Last edited:
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