Glue gun for bonding components to the crossover board?
Hi sba, thanks for photos of your crossover upgrades.
What is the white gunk holding down the caps?
Propose to apply dots of "hotgun" glue to bond pairs of caps together (eg. 2x 36mF =72mF; 2x 12mf =24mF; 3.9mF +2.4mF =6.3mF) then glue down all components to the board. This should make it firm - quite permanent yet feasible to remove by careful use of a scalpel.
Otherwise the bits may buzz. The brass bolts & nuts secured the coils - as if they were loosely coupled, these would ring and decay away over a finite time, so smudging the sound.
Yet the combined weight of the crossover board, together with the flexibility of the substrate, could still resonate. Any ideas on bracing it somehow?
Have redesigned for the new components so they fit in (tagged board, early model). The freshly-potted coils will attach closer to the edge of the board, making room for the fatter Solen caps.
Hi sba, thanks for photos of your crossover upgrades.
What is the white gunk holding down the caps?
Propose to apply dots of "hotgun" glue to bond pairs of caps together (eg. 2x 36mF =72mF; 2x 12mf =24mF; 3.9mF +2.4mF =6.3mF) then glue down all components to the board. This should make it firm - quite permanent yet feasible to remove by careful use of a scalpel.
Otherwise the bits may buzz. The brass bolts & nuts secured the coils - as if they were loosely coupled, these would ring and decay away over a finite time, so smudging the sound.
Yet the combined weight of the crossover board, together with the flexibility of the substrate, could still resonate. Any ideas on bracing it somehow?
Have redesigned for the new components so they fit in
(tagged board, early model). The freshly-potted coils will attach closer to the edge of the board, making room for the fatter Solen caps.To be or not to be... padding resistors
Alan
To begin with, I will try without and hear how they sound "on the rocks". Confess that I am not sure about inserting resistors of these values into the crossover - wouldn't this cause power loss and alter the sensitivities of drivers relative to each other?
Please describe the audible outcome of inserting these resistors. How was this oscillation characterised?
(Buzzing can arise from other causes eg. adhesive separating from the drivers, cabinet panels ringing.....
)
Alan
To begin with, I will try without and hear how they sound "on the rocks". Confess that I am not sure about inserting resistors of these values into the crossover
- wouldn't this cause power loss and alter the sensitivities of drivers relative to each other? Please describe the audible outcome of inserting these resistors. How was this oscillation characterised?
(Buzzing can arise from other causes eg. adhesive separating from the drivers, cabinet panels ringing.....
)Dampening the cabinet walls
Have mentioned considering purchasing Dynamat Xtreme (usually marketed for "In Car Entertainment" to treat car body panels). Would appear that it is a bitumen compound with a foil backsheet and a tacky contact surface.
Would be cheaper to paint cabinet inner walls with a thick even layer of bitumenous gunk. Such stuff is sold for making repairs to flat roofs and for sealing the underside of cars. A tin might cost £12 - compare with Dynamat costing £60 (although an advantage of Dynamat is it is less messy to apply).
While gunk is tacky, apply foil and smooth it down. Instead of fouil, perhaps a rigid material like (very) thin Formica if you can. The idea being that relative movement of the cabinet wall against this other layer will stretch and pull the bitumen.
Repeat this treatment a few times to build up layers if you like.
---
Try bracing the cabinet wall that faces the bass driver by inserting a wood post between the wall and the rear of the bass magnet. This requires moving the crossover down to the bottom compartment, near to where the terminals enter the cabinet.
---
Around the terminal recess, the cabinet wall flexes more than anywhere else. Inside, one can see that there is little strength to the cabinet there - where a small piece of 3/8" chipboard is fixed inside. I have considered replacing it with one of larger area, onto which the crossover could be mounted.
---
Both of these changes would reduce the amount of vibration, yet any residual vibration would be higher in frequency and so possibly more troublesome. Did Celestion knowingly make panels flimsy to tune them to a low frequency?
Have mentioned considering purchasing Dynamat Xtreme (usually marketed for "In Car Entertainment" to treat car body panels). Would appear that it is a bitumen compound with a foil backsheet and a tacky contact surface.
Would be cheaper
to paint cabinet inner walls with a thick even layer of bitumenous gunk. Such stuff is sold for making repairs to flat roofs and for sealing the underside of cars. A tin might cost £12 - compare with Dynamat costing £60 (although an advantage of Dynamat is it is less messy to apply).While gunk is tacky, apply foil and smooth it down. Instead of fouil, perhaps a rigid material like (very) thin Formica if you can. The idea being that relative movement of the cabinet wall against this other layer will stretch and pull the bitumen.
Repeat this treatment a few times to build up layers if you like.
---
Try bracing the cabinet wall that faces the bass driver by inserting a wood post between the wall and the rear of the bass magnet. This requires moving the crossover down to the bottom compartment, near to where the terminals enter the cabinet.
---
Around the terminal recess, the cabinet wall flexes more than anywhere else. Inside, one can see that there is little strength to the cabinet there - where a small piece of 3/8" chipboard is fixed inside. I have considered replacing it with one of larger area, onto which the crossover could be mounted.
---
Both of these changes would reduce the amount of vibration, yet any residual vibration would be higher in frequency and so possibly more troublesome. Did Celestion knowingly make panels flimsy to tune them to a low frequency?
Harnfield-- Using cable ties to secure the coils is a good idea....I used those for the two large air coils on my JBL crossover ( post# 198). It sounds like you'll be building a new board....try to get the coils as far apart from one another as you can. On the original point-to-point board, the three largest coils are perhaps too close to one another
(see- http://www.troelsgravesen.dk/coils.htm ) ).
I have not come across any lit about potting the coils; however, I've seen concerns about un-natural resonances created by capacitors because of the vibrations inside the cabinets. On the 1970’s JBL crossovers that I've seen, the capacitors are entombed in sand inside cardboard barrels. If you're interested, here's a very, very long (too long) thread about capacitor vibrations and other stuff--
( http://www.audioheritage.org/vbulletin/showthread.php?p=69183 )
For my JBL speakers, by the way, I mounted the boards externally to the back with dampening material in between. For aesthetic, re-sale, and other reasons this might not work for many people....but it works for me. When I redo my 66 boards, I might do the same thing.
Because the boards for the JBLs are on the exterior, I left the caps and resistors floating between the solder strips without any adhesive at all. On the pics of my 66 boards, everything was glued down using an extra-thick tacky adhesive that I purchased at a hobby store.
In addition to the horrible original JBL crossovers, the cabinets had barely any dampening...just a little piece of fiberglass. I looked into Dynamat and similar products but found them very expensive. Instead I ended up using a slightly thinner product from the local home improvement store....self-adhesive backed bitumen roof flashing , 12” x 30’ = 29 $ us (I suppose this could be doubled up too.) On top of that I installed a layer of egg-crate shaped foam. One could also add some poly-wool filler to finish it off.
Alan-- Thank you very much for the resistor information...there's a lot of work ahead.
******
sba
(see- http://www.troelsgravesen.dk/coils.htm ) ).
I have not come across any lit about potting the coils; however, I've seen concerns about un-natural resonances created by capacitors because of the vibrations inside the cabinets. On the 1970’s JBL crossovers that I've seen, the capacitors are entombed in sand inside cardboard barrels. If you're interested, here's a very, very long (too long) thread about capacitor vibrations and other stuff--
( http://www.audioheritage.org/vbulletin/showthread.php?p=69183 )
For my JBL speakers, by the way, I mounted the boards externally to the back with dampening material in between. For aesthetic, re-sale, and other reasons this might not work for many people....but it works for me. When I redo my 66 boards, I might do the same thing.
Because the boards for the JBLs are on the exterior, I left the caps and resistors floating between the solder strips without any adhesive at all. On the pics of my 66 boards, everything was glued down using an extra-thick tacky adhesive that I purchased at a hobby store.
In addition to the horrible original JBL crossovers, the cabinets had barely any dampening...just a little piece of fiberglass. I looked into Dynamat and similar products but found them very expensive. Instead I ended up using a slightly thinner product from the local home improvement store....self-adhesive backed bitumen roof flashing , 12” x 30’ = 29 $ us (I suppose this could be doubled up too.) On top of that I installed a layer of egg-crate shaped foam. One could also add some poly-wool filler to finish it off.
Alan-- Thank you very much for the resistor information...there's a lot of work ahead.
******
sba
Re: Potting the air-cored inductors
Probably the sound will improve to some degree, though vibration by very small amount in an inductor will not cause the same degree of audible problem as vibration within a capacitor, as within a capacitor vibration can cause piezoelectric effect, which is a voltage generation, thus signal to the speaker.
Also, vibration is likely to cause greater variation of capacitance than of inductance, given the very small distances moved.
After being potted, coils cannot be easily unpotted.
I wrap mine tightly with a strong plastic insulating tape, to reduce vibration, and then tie them down tightly with plastic or nylon cable ties.
I think it would be good to remove the steel bolt-head.
I do not know its degree of change on the field, this would have to be measured, but if it is entirely outside of the coil, its effect will not be large unless the size of the steel piece is very large.
harnfield said:
Am told that speaker sound improves if the coils are potted in thermally-conductive epoxy so that they cannot physically move.
***************************************************
I expected the bolts and nuts securing the coils to the board to be brass.Not exactly - the head was attracted to a speaker magnet when placed near, and so is made of steel. Still, the bolt shank and nut are indeed of brass.
Having this piece of steel near the centre of the coil increases its inductance slightly, with the adverse effect of some hysteresis. Air cored coils are supposed to handle larger signals and remain more linear than ferrite-cored inductors. Even if small, this steel has more hysteresis than ferrite, I guess.
I propose to dispense with the steel-brass bolts - instead fixing each coil with plastic cable ties.
Then if the crossover frequency for the bass unit rises, by how much?
Comments most welcome
Probably the sound will improve to some degree, though vibration by very small amount in an inductor will not cause the same degree of audible problem as vibration within a capacitor, as within a capacitor vibration can cause piezoelectric effect, which is a voltage generation, thus signal to the speaker.
Also, vibration is likely to cause greater variation of capacitance than of inductance, given the very small distances moved.
After being potted, coils cannot be easily unpotted.
I wrap mine tightly with a strong plastic insulating tape, to reduce vibration, and then tie them down tightly with plastic or nylon cable ties.
I think it would be good to remove the steel bolt-head.
I do not know its degree of change on the field, this would have to be measured, but if it is entirely outside of the coil, its effect will not be large unless the size of the steel piece is very large.
Some errors in my post #74 - corrected below
Corrections and some Additions are inside the Quote Box below :-
For the Tweeter part of the x-over :-
In the oldest 66s are the seeming Paper-in-Oil caps {PIOs}.
I do not know their Dissipation Factors, not even typically as I have no data, though it could be found in old Text Books in some Libraries.
I don't expect it to be as high as Electros though.
PIOs do have lower Dielectric Absorbsion than Electros, but not as low as Polypropylenes.
{The original PIO types, which used Mineral Oil, and some new manufactured PIOs still do, but one brand apparently uses Vegetable Oil which has higher Dielectric Absorbsion. I don't know why they use it !}.
In the later 66s are the Polyester, probably Mylar, caps, and probably Metallized type -{now known as MKT caps}.
These have significantly lower Dissipation Factor than Electros, but it is still not linear, however calculated ESR figures are less than 0.1 ohm at all relevant frequencies for the tweeter.
BUT, these caps do have significant Dielectric Absorbsion and it is audible.
Polypropylene caps are much cleaner sounding.
There is no need to add ESR compensating resistors to new caps for the treble section, but if one does not like the slightly more forward sound the polypropylene caps allow the tweeter to produce than the older 66s' PIOs, then try adding a 0.47 or 0.5 ohm non-inductive resistor in Series between the closest to tweeter cap and the tweeter.
5 watt will be sufficient with such low resistance, thus the Mills MRA-5 non-inductives will be fine.
Of course one can add the same resistors to the later 66s' tweeters if want to.
Corrections and some Additions are inside the Quote Box below :-
alan-1-b said:
For the Tweeter part of the x-over :-
In the oldest 66s are the seeming Paper-in-Oil caps {PIOs}.
I do not know their Dissipation Factors, not even typically as I have no data, though it could be found in old Text Books in some Libraries.
I don't expect it to be as high as Electros though.
PIOs do have lower Dielectric Absorbsion than Electros, but not as low as Polypropylenes.
{The original PIO types, which used Mineral Oil, and some new manufactured PIOs still do, but one brand apparently uses Vegetable Oil which has higher Dielectric Absorbsion. I don't know why they use it !}.
In the later 66s are the Polyester, probably Mylar, caps, and probably Metallized type -{now known as MKT caps}.
These have significantly lower Dissipation Factor than Electros, but it is still not linear, however calculated ESR figures are less than 0.1 ohm at all relevant frequencies for the tweeter.
BUT, these caps do have significant Dielectric Absorbsion and it is audible.
Polypropylene caps are much cleaner sounding.
There is no need to add ESR compensating resistors to new caps for the treble section, but if one does not like the slightly more forward sound the polypropylene caps allow the tweeter to produce than the older 66s' PIOs, then try adding a 0.47 or 0.5 ohm non-inductive resistor in Series between the closest to tweeter cap and the tweeter.
5 watt will be sufficient with such low resistance, thus the Mills MRA-5 non-inductives will be fine.
Of course one can add the same resistors to the later 66s' tweeters if want to.
Re: To be or not to be... padding resistors
Hi harnfield,
I'll answer each of your points and type my replies inside the Quote Box following each of your points :-
Hi harnfield,
I'll answer each of your points and type my replies inside the Quote Box following each of your points :-
harnfield said:Alan
To begin with, I will try without and hear how they sound "on the rocks".
-----> Certainly do this, this is the opportunity to hear the drivers connected to somewhat different Impedances than were in the original x-over when it was new -{and likely substantially different Impedances in the x-over now with the age effect in those old caps !}.
____________________________________________________
Confess that I am not sure about inserting resistors of these values into the crossover
-----> No, because these resistances I have specified are likely, or very close to, those which were inside those old black electrolytic caps, thus with the resistors the relative drivers' sensitivities should be affected the same as Celestion originally did.
____________________________________________________
Please describe the audible outcome of inserting these resistors. How was this oscillation characterised?
The oscillation to whatever degree audible will be heard as a tonal colouration in the affected parts of the frequency spectrum and will change the relative levels between instruments and voices in the mix to some degree.
If it is very high, it will cause obscuring of fine details, and in general will make the speakers sound Low Budget, rather like panel vibrations but at higher frequencies.
____________________________________________________
(Buzzing can arise from other causes eg. adhesive separating from the drivers, cabinet panels ringing.....
-----> Yes, but one can try to eliminate all types, and hear the differences between types whilst doing so.
Resistor values
Alan
Most indebted to you for explaining Dissipation Factor and estimating values.
I have 3 types of old resistors to hand, once used for crossovers. In ascending order of length (3/8 inch, 3/4 inch, 2 inch) are labelled W21, W22 or W24 and bear a manufacturers mark - an Ohm symbol with the letter W in the centre of the Ohm. They have an enamel coating of colour British Racing Green and are marked 5% tolerance.
Would be most grateful if you would confirm or rectify my idea to use these as follows:
1.1 ohm in series with C8 (ie. 2.2 ohm, two together in parallel)
1.4 ohm in series with C7 (ie. 2.4 ohm & 3.3 ohm in parallel)
3.3 ohm in series with C5
could insert 1.65 ohm instead of 1.4 ohm (ie. 3.3 ohm in parallel)
---
Am considering not inserting any ESR compensation in series with C6 so that bass will roll off a bit more with increasing frequency, bearing in mind that a bit more energy is being directed to the lower frequencies of the mid unit. I understand that the bass will be giving out a bit less energy, requiring the 1.4 ohm to be increased to reduce the mid energy to restore the balance.
Another reason for inserting only next to C7 and not C6 is that at 500Hz the ESR was about 0.2 ohm and diminishes further at lower frequencies, yet the padding capacitors would remain 1ohm.
If you agree with this last point, would it be better to insert next to C6 and not C7 ? (instead of next to C7and not C6)
---
This tweeter section had 4 microFarad and 6 microFarad of the "Metallized" type of capacitor (early "woodie" with tag board). Intend that Solen replacements will be 3.9 microFarad and 6.3 microFarad (could make this a lower value eg. 5.7 microFarad).
Thanks for reading down this far!
Alan
Most indebted to you for explaining Dissipation Factor and estimating values.
I have 3 types of old resistors to hand, once used for crossovers. In ascending order of length (3/8 inch, 3/4 inch, 2 inch) are labelled W21, W22 or W24 and bear a manufacturers mark - an Ohm symbol with the letter W in the centre of the Ohm. They have an enamel coating of colour British Racing Green and are marked 5% tolerance.
Would be most grateful if you would confirm or rectify my idea to use these as follows:
1.1 ohm in series with C8 (ie. 2.2 ohm, two together in parallel)
1.4 ohm in series with C7 (ie. 2.4 ohm & 3.3 ohm in parallel)
3.3 ohm in series with C5
could insert 1.65 ohm instead of 1.4 ohm (ie. 3.3 ohm in parallel)
---
Am considering not inserting any ESR compensation in series with C6 so that bass will roll off a bit more with increasing frequency, bearing in mind that a bit more energy is being directed to the lower frequencies of the mid unit. I understand that the bass will be giving out a bit less energy, requiring the 1.4 ohm to be increased to reduce the mid energy to restore the balance.
Another reason for inserting only next to C7 and not C6 is that at 500Hz the ESR was about 0.2 ohm and diminishes further at lower frequencies, yet the padding capacitors would remain 1ohm.
If you agree with this last point, would it be better to insert next to C6 and not C7 ? (instead of next to C7and not C6)
---
This tweeter section had 4 microFarad and 6 microFarad of the "Metallized" type of capacitor (early "woodie" with tag board). Intend that Solen replacements will be 3.9 microFarad and 6.3 microFarad (could make this a lower value eg. 5.7 microFarad).
Thanks for reading down this far!
those old W series resistors
harnfield,
from your description I think it is likely those old resistors were made by the British "Welwyn" company.
Welwyn currently make those three W series and also a W23 series, {and many other series of different types of resistors}.
Their resistors are good quality, I have some and no problems with any of mine.
The Company is long in the business and has a good reputation.
I think your samples are from older production because:-
the current production W21 is 1/2" x 3/16", and is rated at 2.5 watts @ 70 degrees C .
Yours being shorter would be no more than 2 watts, and perhaps only 1.5 watts if they are thinner than 3/16" {5.6mm}.
the current prod. W22 is 7/8" x 5/16", and is rated at 6 watts @ 70 dgrees C.
Yours being shorter would be no more than 5 watts, and may be only 4 watts if thinner.
{they do make a 7mm, {9/32"} thickness which is 4.3 watts, and is also 7/8" long}.
the current prod. W24 is 2 1/8" x 5/16", and is 12 watts @ 70 degrees C.
Yours being shorter would be 10 or 11 watts, depending on its thickness.
{the W23 is 1 1/2" x 5/16" and is 9 watts}.
I have quoted the 70 degrees C ratings, because most resistors' power ratings are quoted at 70 degrees C, though wirewound types have a slightly higher power rating at 25 degrees C, but this is of little use unless the resistor is forceably cooled !
All resistors must be derated for power as they get hotter, and those Welwyns {new production} are down to only 54% of their power rating when they are at 200 degrees C {yes, quite hot}, and zero power at 315 degrees C {no, I've never run a resistor that hot !}.
Inside a speaker cabinet it gets warm from the heat from the magnet on the woofer at moderate volume levels, thus a resistor will not cool down in there whilst the music is playing, but usually no problems because reputable manufacturers use resistors of power ratings about 3 to 5 times higher than they will have to disperse in normal operation of the speakers, thus they only get warm and not hot {unless the speaker is severely overdriven}.
I always use sufficient rating to enable the resistor to stay cool for most of the time, and I have specified for that condition here with the Mills MRA-5 of 5 watts.
I specified those Mills primarily because they are very good quality, and of small size, thus can be fitted more easily onto the circuit boards with some space between them and other components.
{never put a resistor touching another component, nor even hard against another resistor - leave a gap to allow for cooling, and a space underneath - not touching the board if the resistor is going to get warm in application}.
In the Parallel to bass and mid drivers' locations in the 66s' x-over it is not necessary to use non-inductive for the resistors because the inductance of such low ohms resistors will be very low.
In the Series connected resistor to the 24uF cap to the mid driver it is better to use a non-inductive resistor,
and if using resistors in Series to the tweeters do use non-inductives.
Thus you can use some of your W series resistors,
more on these in the next Post.
harnfield,
from your description I think it is likely those old resistors were made by the British "Welwyn" company.
Welwyn currently make those three W series and also a W23 series, {and many other series of different types of resistors}.
Their resistors are good quality, I have some and no problems with any of mine.
The Company is long in the business and has a good reputation.
I think your samples are from older production because:-
the current production W21 is 1/2" x 3/16", and is rated at 2.5 watts @ 70 degrees C .
Yours being shorter would be no more than 2 watts, and perhaps only 1.5 watts if they are thinner than 3/16" {5.6mm}.
the current prod. W22 is 7/8" x 5/16", and is rated at 6 watts @ 70 dgrees C.
Yours being shorter would be no more than 5 watts, and may be only 4 watts if thinner.
{they do make a 7mm, {9/32"} thickness which is 4.3 watts, and is also 7/8" long}.
the current prod. W24 is 2 1/8" x 5/16", and is 12 watts @ 70 degrees C.
Yours being shorter would be 10 or 11 watts, depending on its thickness.
{the W23 is 1 1/2" x 5/16" and is 9 watts}.
I have quoted the 70 degrees C ratings, because most resistors' power ratings are quoted at 70 degrees C, though wirewound types have a slightly higher power rating at 25 degrees C, but this is of little use unless the resistor is forceably cooled !
All resistors must be derated for power as they get hotter, and those Welwyns {new production} are down to only 54% of their power rating when they are at 200 degrees C {yes, quite hot}, and zero power at 315 degrees C {no, I've never run a resistor that hot !}.
Inside a speaker cabinet it gets warm from the heat from the magnet on the woofer at moderate volume levels, thus a resistor will not cool down in there whilst the music is playing, but usually no problems because reputable manufacturers use resistors of power ratings about 3 to 5 times higher than they will have to disperse in normal operation of the speakers, thus they only get warm and not hot {unless the speaker is severely overdriven}.
I always use sufficient rating to enable the resistor to stay cool for most of the time, and I have specified for that condition here with the Mills MRA-5 of 5 watts.
I specified those Mills primarily because they are very good quality, and of small size, thus can be fitted more easily onto the circuit boards with some space between them and other components.
{never put a resistor touching another component, nor even hard against another resistor - leave a gap to allow for cooling, and a space underneath - not touching the board if the resistor is going to get warm in application}.
In the Parallel to bass and mid drivers' locations in the 66s' x-over it is not necessary to use non-inductive for the resistors because the inductance of such low ohms resistors will be very low.
In the Series connected resistor to the 24uF cap to the mid driver it is better to use a non-inductive resistor,
and if using resistors in Series to the tweeters do use non-inductives.
Thus you can use some of your W series resistors,
more on these in the next Post.
which Capacitors ?
I am not sure which caps you are refering to with C6 and C7.
In rwthomkins' Post # 162 on Page 7 the first Link line is for the Ditton 66 P.C.C. and lists C6 and C8 as 72uF,
C7 as 24uF, {and C5 as 4uF}.
Yes, such numbering is a little strange, instead of using 7 and 8 for the bass section 72 uF caps.
the third Link line for the older Ditton 66 T.B.C. has different numbering for the caps, and is logical !
I will Post an alternate way we can identify the caps so that owners of both types of 66s can follow the discussion more easily, but next time as I have to go now.
____________________________________________________
Do you have the 66 version which uses the Light Green caps in the treble section of the x-over -
- see Grahame's photos on Page 2 in Posts' # 31 and #32,
or those with the darker green caps -
- see photos in Post #47
Which ?
I am puzzled why you mention using 6.3uF or 5.7uF ...
why not simply 6uF, if you have the older 66s ?
I will Post more on this next time.
____________________________________________________
Which of your Resistors' values do you have in which W series ?
I will recommend positions better if I know power ratings of each of the values {2.2 , 2.4 , 3.3 ohms}.
harnfield said:
I am not sure which caps you are refering to with C6 and C7.
In rwthomkins' Post # 162 on Page 7 the first Link line is for the Ditton 66 P.C.C. and lists C6 and C8 as 72uF,
C7 as 24uF, {and C5 as 4uF}.
Yes, such numbering is a little strange, instead of using 7 and 8 for the bass section 72 uF caps.
the third Link line for the older Ditton 66 T.B.C. has different numbering for the caps, and is logical !
I will Post an alternate way we can identify the caps so that owners of both types of 66s can follow the discussion more easily, but next time as I have to go now.
____________________________________________________
Do you have the 66 version which uses the Light Green caps in the treble section of the x-over -
- see Grahame's photos on Page 2 in Posts' # 31 and #32,
or those with the darker green caps -
- see photos in Post #47
Which ?
I am puzzled why you mention using 6.3uF or 5.7uF ...
why not simply 6uF, if you have the older 66s ?
I will Post more on this next time.
____________________________________________________
Which of your Resistors' values do you have in which W series ?
I will recommend positions better if I know power ratings of each of the values {2.2 , 2.4 , 3.3 ohms}.
choices of Resistors and Capacitors
Hi there sba
Thanks a lot Alan. I thought they were good ones - kept them for over 30 years. Image on this datasheet is exactly what they look like:
http://www.welwyn-tt.com/pdf/datasheet/W20.PDF
More accurate measurements:
W21 7/16" x 3/16" dia
W22 3/4" x 1/4" dia
W24 2" x 1/4" dia
I am using the circuit diagram from the Ditton 66 PCC datasheet. Sorry did not notice that Celestion relabelled the components!
so...
1.1 ohm in series with 72microF - C8 (ie. two of 2.2 ohm W24 in parallel)
1.4 ohm in series with 24 microF - C7 (ie. 2.4 ohm & 3.3 ohm both W22 in parallel)
3.3 ohm W24 in series with 4 microF - C5
could insert 1.65 ohm instead of 1.4 ohm (ie. using two of 3.3 ohm W22 in parallel)
also...
Have found 1.0 ohm W21 to put in series with C6, however you may warn that it will get hot! (Datasheet rates it at 3W and up to 100v.) Would it do?
[Please ignore my paragraph "Another reason .... not C6 is that at 500Hz the ESR was about 0.2 ohm and diminishes further at lower frequencies, yet the padding capacitors would remain 1ohm." The impedance of C6 rises to 22 ohm at 100Hz so the ESR is not significant - it is the 1:4 ratio around the crossover frequency that matters, your point exactly.]
---
My cheap multimeter is unsuitable for these low resistances - it thinks the bass coil is DC 1 ohm - 2 ohm, and the 2.2 ohm resistors are about 1 ohm. Could you suggest a more reliable device, perhaps that mightmeasure capacitors & inductors? I know that bridges with calibrated components are the textbook way, but maybe there is a cheap-ish device out there!
---
My Ditton 66s are old "woodies" with MF500 and the smaller dustcap on the T1600 woofers. They have tag circuitboard, and use 24 microfarad rather than 28 or 30 for C7. The tweeter capacitors are made up of banks of 2 microFarad bound together with cloth tape with a cable tie to the board. They are a rather pretty faded brown/plum colour, marked "METALLISED 2.0uF 150v DC WKG I UH".
Nonetheless, will replace them with the nearest Solens. Replacing 4 by 3.9, and 6 by 5.7 or 6.3 (ie. 3.9 + 1.8 or 3.9 + 2.4).
---
I recall that sba received 62 microF capacitors. Instead of needing padding resistance of 1 ohm for 72 microF capacitor, why not replace both by this 62 microF? Would yield about the appropriate impedance around 500Hz, while rolling off a bit steeper. This would be compensated by more energy emerging from the mid unit at the low end of its range because the resistor of 1.5 ohm padding out the 24 microF capacitor is lower than the ESR of 3 ohm at 500 Hz. That is... the Potential Divider of this L network lets more voltage through to the second L section, and hence to the mid driver.
---
Please take a look at Tony Gee's audiophile capacitor test:
http://www.humblehomemadehifi.com/Cap.html
- as far as I can tell by looking at this page, Tony was testing capacitors similar to those we sourced:
http://www.madisound.com/manufacturers/solen/fastcaps.php
His scoring: Solen 6.5 SoniCap 8.5
But then SoniCaps are pricier
---
Particularly note Tony's tip to add 10nF Vishay Roederstein MKP1837
in parallel with all capacitors, which "take away the "grainy" edge..... gain in clarity and transparency making instruments better separable from each other, the violins in an orchestra are a group of individual violins instead of one mass. Jazz drum brushes sound more like a brush than a "shush".
http://uk.rs-online.com/web/search/...d=searchProducts&searchTerm=MKP1837&x=20&y=12
Costs only £8.40 for 10 capacitors (minimum order quantity)
---
Have read the test for capacitor microphony, now plotting to detach the crossover, and place it separately outside the cabinet. I expect that any physical contact with the back panel would excite vibrations in the crossover components.
Now how to make that elegant?
---
As I have to hand, am rewiring with Nordost SPM.
---
Also installing 4 terminals (better ones) instead of the old terminals. "Bi-wiring" will allow the power amp to control the motion of the bass unit independently of the other drivers, without any back EMF flowing through the circuitboard itself.
Some say they cannot hear the difference with Bi-wiring or without. However I have the necessary biwire speaker cables so will biwire.
Hi there sba
Thanks a lot Alan. I thought they were good ones - kept them for over 30 years. Image on this datasheet is exactly what they look like:
http://www.welwyn-tt.com/pdf/datasheet/W20.PDF
More accurate measurements:
W21 7/16" x 3/16" dia
W22 3/4" x 1/4" dia
W24 2" x 1/4" dia
I am using the circuit diagram from the Ditton 66 PCC datasheet. Sorry did not notice that Celestion relabelled the components!
so...
1.1 ohm in series with 72microF - C8 (ie. two of 2.2 ohm W24 in parallel)
1.4 ohm in series with 24 microF - C7 (ie. 2.4 ohm & 3.3 ohm both W22 in parallel)
3.3 ohm W24 in series with 4 microF - C5
could insert 1.65 ohm instead of 1.4 ohm (ie. using two of 3.3 ohm W22 in parallel)
also...
Have found 1.0 ohm W21 to put in series with C6, however you may warn that it will get hot! (Datasheet rates it at 3W and up to 100v.) Would it do?
[Please ignore my paragraph "Another reason .... not C6 is that at 500Hz the ESR was about 0.2 ohm and diminishes further at lower frequencies, yet the padding capacitors would remain 1ohm." The impedance of C6 rises to 22 ohm at 100Hz so the ESR is not significant - it is the 1:4 ratio around the crossover frequency that matters, your point exactly.]
---
My cheap multimeter is unsuitable for these low resistances - it thinks the bass coil is DC 1 ohm - 2 ohm, and the 2.2 ohm resistors are about 1 ohm. Could you suggest a more reliable device, perhaps that mightmeasure capacitors & inductors? I know that bridges with calibrated components are the textbook way, but maybe there is a cheap-ish device out there!
---
My Ditton 66s are old "woodies" with MF500 and the smaller dustcap on the T1600 woofers. They have tag circuitboard, and use 24 microfarad rather than 28 or 30 for C7. The tweeter capacitors are made up of banks of 2 microFarad bound together with cloth tape with a cable tie to the board. They are a rather pretty faded brown/plum colour, marked "METALLISED 2.0uF 150v DC WKG I UH".
Nonetheless, will replace them with the nearest Solens. Replacing 4 by 3.9, and 6 by 5.7 or 6.3 (ie. 3.9 + 1.8 or 3.9 + 2.4).
---
I recall that sba received 62 microF capacitors. Instead of needing padding resistance of 1 ohm for 72 microF capacitor, why not replace both by this 62 microF? Would yield about the appropriate impedance around 500Hz, while rolling off a bit steeper. This would be compensated by more energy emerging from the mid unit at the low end of its range because the resistor of 1.5 ohm padding out the 24 microF capacitor is lower than the ESR of 3 ohm at 500 Hz. That is... the Potential Divider of this L network lets more voltage through to the second L section, and hence to the mid driver.
---
Please take a look at Tony Gee's audiophile capacitor test:
http://www.humblehomemadehifi.com/Cap.html
- as far as I can tell by looking at this page, Tony was testing capacitors similar to those we sourced:
http://www.madisound.com/manufacturers/solen/fastcaps.php
His scoring: Solen 6.5 SoniCap 8.5
But then SoniCaps are pricier
---
Particularly note Tony's tip to add 10nF Vishay Roederstein MKP1837
in parallel with all capacitors, which "take away the "grainy" edge..... gain in clarity and transparency making instruments better separable from each other, the violins in an orchestra are a group of individual violins instead of one mass. Jazz drum brushes sound more like a brush than a "shush".http://uk.rs-online.com/web/search/...d=searchProducts&searchTerm=MKP1837&x=20&y=12
Costs only £8.40 for 10 capacitors (minimum order quantity)
---
Have read the test for capacitor microphony, now plotting to detach the crossover, and place it separately outside the cabinet. I expect that any physical contact with the back panel would excite vibrations in the crossover components.
Now how to make that elegant?
---
As I have to hand, am rewiring with Nordost SPM.
---
Also installing 4 terminals (better ones) instead of the old terminals. "Bi-wiring" will allow the power amp to control the motion of the bass unit independently of the other drivers, without any back EMF flowing through the circuitboard itself.
Some say they cannot hear the difference with Bi-wiring or without. However I have the necessary biwire speaker cables so will biwire.
Welwyn W20 series resistors
Alan
Phoned Welwyn who say W24 inductance 40 nH -100 nH for value 1 ohm to 3 ohms --> ie. impedance of 3 - 6 ohms at 10kHz.
Too high.
Looking but not found yet a contact number or webpage for Mills data. They state that "low" inductance but see comments about top-end roll off in discussions about Duelund resistors v. Mills on partsconnexion website:
http://www.partsconnexion.com/catalog/resistors.html
I know of aluminium handmade foil resistors, but they would cover a good part of the back panel of the loudspeaker!
Alan
Phoned Welwyn who say W24 inductance 40 nH -100 nH for value 1 ohm to 3 ohms --> ie. impedance of 3 - 6 ohms at 10kHz.
Too high.
Looking but not found yet a contact number or webpage for Mills data. They state that "low" inductance but see comments about top-end roll off in discussions about Duelund resistors v. Mills on partsconnexion website:
http://www.partsconnexion.com/catalog/resistors.html
I know of aluminium handmade foil resistors, but they would cover a good part of the back panel of the loudspeaker!
thanks for help with these Welwyn resistors
Alan
Truly sorry, my choices of Welwyn were aimed at using up the values that I have.
In my last post, I wrote that Welwyn inductance was too high - reactance at 10kHz would equal or exceed the nominal resistance - doubling again by 20kHz. Such roll off at top end is surely undesirable unless need to tame an ascending response(would guess the natural response curve of the HF2000 is fairly even up to say 22kHz after which it declines from cancellation effects of the width of the driver surface).
(Yet when using two Welwyns in parallel --> halves the unwanted inductance.)
Then again current Welwyns use steel core in the termination (my older ones probably too) whereas Mills use copper instead which should sound better. Mills is supplied for audiophile application (including by Sonicraft, makers of Sonicaps) whereas Welwyn make no claim in regard for audio application.
To conclude - am now looking for a UK website to order Mills
This UK website only stocks the 12W at £4:
http://www.hificollective.co.uk/components/mills.html
- twice the $3.50 US price from partsconnexion (or Sonicraft)
Might you know another UK source
- or would you order direct from US?
---
Maplin have LCR multimeter model GW26D for £45, although spec only +/-8% accuracy for caps (+/-5% for inductors)
Or on eBay, one that looks better, Digitech DMM for $45 (buy-it-now) spec.d at +/-2.5% (can be trusted?):
http://cgi.ebay.co.uk/Digital-LCR-I...ageNameZWD2VQQcmdZViewItem?_trksid=p1638.m122
---
Have no oscilloscope.
So what about this gadget on eBay which seems to turn a PC into an oscilloscope:
http://cgi.ebay.co.uk/5-Channel-Por...ryZ45008QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Other gadgets of this kind are listed too.
Whereas conventional oscilloscopes seem to start from £200.
many thanks!
Alan
Truly sorry, my choices of Welwyn were aimed at using up the values that I have.
In my last post, I wrote that Welwyn inductance was too high - reactance at 10kHz would equal or exceed the nominal resistance - doubling again by 20kHz. Such roll off at top end is surely undesirable unless need to tame an ascending response(would guess the natural response curve of the HF2000 is fairly even up to say 22kHz after which it declines from cancellation effects of the width of the driver surface).
(Yet when using two Welwyns in parallel --> halves the unwanted inductance.)
Then again current Welwyns use steel core in the termination (my older ones probably too) whereas Mills use copper instead which should sound better. Mills is supplied for audiophile application (including by Sonicraft, makers of Sonicaps) whereas Welwyn make no claim in regard for audio application.
To conclude - am now looking for a UK website to order Mills
This UK website only stocks the 12W at £4:
http://www.hificollective.co.uk/components/mills.html
- twice the $3.50 US price from partsconnexion (or Sonicraft)
Might you know another UK source
- or would you order direct from US?
---
Maplin have LCR multimeter model GW26D for £45, although spec only +/-8% accuracy for caps (+/-5% for inductors)
Or on eBay, one that looks better, Digitech DMM for $45 (buy-it-now) spec.d at +/-2.5% (can be trusted?):
http://cgi.ebay.co.uk/Digital-LCR-I...ageNameZWD2VQQcmdZViewItem?_trksid=p1638.m122
---
Have no oscilloscope.
So what about this gadget on eBay which seems to turn a PC into an oscilloscope:
http://cgi.ebay.co.uk/5-Channel-Por...ryZ45008QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Other gadgets of this kind are listed too.
Whereas conventional oscilloscopes seem to start from £200.
many thanks!
Riedon resistors instead of Mills?
Yup bought all the Solen caps:
two 12 microF in parallel for C7
two 36 microF in parallel for C6, C8
3.9 microF for C5, {C3+C4}
3.9 + 1.8 microF for {C1+C2}
also bought a 2.4 microF to substitute for that 1.8 microF if need to lift the top a bit
---
already have these tiny 0.01 microF and 0.1 microF Vishay MKP1837 capacitors ready to try in parallel with C7,{C3+C4}, {C1+C2}
http://uk.rs-online.com/web/search/...d=searchProducts&searchTerm=MKP1837&x=20&y=12
---
please read this page:
http://www.welbornelabs.com/mills.htm
"We are now replacing the Mills resistors with the new Riedon 10W non-inductive wirewound resistors. We think these Riedons sound much better than the Mills, they are less expensive and are approximately half the size of the Mills so we will be gradually phasing them in stock."
Also read something similar observation elsewhere.
So propose to order these total quantities of Riedon resistors from Welborne:
4 x 1 ohm for bass section C6, C8
4 x 7 ohm (in parallel for 3.5 ohm) for mid section C5
8 x 0.8 ohm (in series for 1.6 ohm) for mid section C7, and to keep in case need to insert (parallel for 0.4 ohm) to tame the HF2000
$56 plus $30 for express delivery plus UK VAT * customs clearance = £57
---
I wonder what would be the potential resonant frequency with the Vishay MKP1837 across 24 microF capacitance, compared with putting the Vishay MKP1837 across BOTH the Solen capacitors and the Riedon resistors (not just across the capacitors) which will have finite if small inductance.
I guess the Vishay should be across only the Solen capacitors. Just wondered, that's all.
Look forward to reading your comments on Tony Gees "shoot out":
http://www.humblehomemadehifi.com/Cap.html
Yup bought all the Solen caps:
two 12 microF in parallel for C7
two 36 microF in parallel for C6, C8
3.9 microF for C5, {C3+C4}
3.9 + 1.8 microF for {C1+C2}
also bought a 2.4 microF to substitute for that 1.8 microF if need to lift the top a bit
---
already have these tiny 0.01 microF and 0.1 microF Vishay MKP1837 capacitors ready to try in parallel with C7,{C3+C4}, {C1+C2}
http://uk.rs-online.com/web/search/...d=searchProducts&searchTerm=MKP1837&x=20&y=12
---
please read this page:
http://www.welbornelabs.com/mills.htm
"We are now replacing the Mills resistors with the new Riedon 10W non-inductive wirewound resistors. We think these Riedons sound much better than the Mills, they are less expensive and are approximately half the size of the Mills so we will be gradually phasing them in stock."
Also read something similar observation elsewhere.
So propose to order these total quantities of Riedon resistors from Welborne:4 x 1 ohm for bass section C6, C8
4 x 7 ohm (in parallel for 3.5 ohm) for mid section C5
8 x 0.8 ohm (in series for 1.6 ohm) for mid section C7, and to keep in case need to insert (parallel for 0.4 ohm) to tame the HF2000
$56 plus $30 for express delivery plus UK VAT * customs clearance = £57
---
I wonder what would be the potential resonant frequency with the Vishay MKP1837 across 24 microF capacitance, compared with putting the Vishay MKP1837 across BOTH the Solen capacitors and the Riedon resistors (not just across the capacitors) which will have finite if small inductance.
I guess the Vishay should be across only the Solen capacitors. Just wondered, that's all.
Look forward to reading your comments on Tony Gees "shoot out":
http://www.humblehomemadehifi.com/Cap.html
another thread about bi-passing with small value cap
http://www.diyaudio.com/forums/showthread.php?threadid=60603
also discusses:
- isolating the crossover
- wrapping tweeter capacitors in sorbothane
---
http://www.audioasylum.com/cgi/t.mpl?f=mug&m=97306
mentions:
- Cannock resistors superior to Mills ((note sure if Cannock go down to the low values or as high power))
- embedding in Repti-Sand
- panel damping with Dynamat Xtreme
Read elsewhere about damping with another material called Blackhole BH-5
---
tried to find datasheet from Riedon website however their website seems down at present:
http://www.riedon.com/
in the photo on Welbornes webpage, the Riedon resistors have "42 2" written on them and appear to be wirewound. No luck so far with web search for any alternative vendor to Welborne, who might supply the exact values (0.5, 1, ~1.5, 3.3 ohm) perhaps.
http://www.diyaudio.com/forums/showthread.php?threadid=60603
also discusses:
- isolating the crossover
- wrapping tweeter capacitors in sorbothane
---
http://www.audioasylum.com/cgi/t.mpl?f=mug&m=97306
mentions:
- Cannock resistors superior to Mills ((note sure if Cannock go down to the low values or as high power))
- embedding in Repti-Sand
- panel damping with Dynamat Xtreme
Read elsewhere about damping with another material called Blackhole BH-5
---
tried to find datasheet from Riedon website however their website seems down at present:
http://www.riedon.com/
in the photo on Welbornes webpage, the Riedon resistors have "42 2" written on them and appear to be wirewound. No luck so far with web search for any alternative vendor to Welborne, who might supply the exact values (0.5, 1, ~1.5, 3.3 ohm) perhaps.
Re: choices of Resistors and Capacitors - CONTINUED -
harnfield,
you're going too fast for me to keep up with, but researching and finding things is good, how-ever do allow yourself time to think about the veracity of some claims before you buy. Remember, all the small-business sellers sometimes have other reasons behind changing a brand line than simply audio quality ... and when you find some extraordinary claims about significant improvements in sound quality as result of a seemingly irrelevant change then search more Forums to see if counter-claims, especially on this 0.01uF and 0.1uF cap bypass business - these claims have been going on for years ... more later about such.
I will continue from where I left off yesterday, and Post inside the Quote Box again :-
I have to finish now, but do Post a list of the resistors' values that you have in each Welwyn size, and the number of each.
You can use some of them with little worry about the Inductance.
Don't rush into buying the Riedons yet, and you may need two other resistors now also ... more next time.
harnfield,
you're going too fast for me to keep up with, but researching and finding things is good, how-ever do allow yourself time to think about the veracity of some claims before you buy. Remember, all the small-business sellers sometimes have other reasons behind changing a brand line than simply audio quality ... and when you find some extraordinary claims about significant improvements in sound quality as result of a seemingly irrelevant change then search more Forums to see if counter-claims, especially on this 0.01uF and 0.1uF cap bypass business - these claims have been going on for years ... more later about such.
I will continue from where I left off yesterday, and Post inside the Quote Box again :-
harnfield said:
I recall that sba received 62 microF capacitors. Instead of needing padding resistance of 1 ohm for 72 microF capacitor, why not replace both by this 62 microF? Would yield about the appropriate impedance around 500Hz,
-----> its NOT Impedance we want to change as simply such.
Leave aside Impedance for a moment, and consider the components which make up Impedance :-
Resistance and Reactance, and
Reactance can be either Capacitive or Inductive.
Capacitance and Inductance act in opposite Phase to each other, thus when applied in Series with each other they will Resonate at one specific frequency and cause zero Impedance at that frequency, unless some series Resistance is in the circuit also.
When applied in Parallel with each other the same inductance and capacitance will cause resonance at the same specific frequency but will cause very high impedance at that frequency {infinitely high if no series resistance present - impossible to occur with actual components} unless some series resistance is in at least one arm of the parallel circuit to reduce the magnitude of the resonance.
A resistor in parallel with a parallel inductance/capacitance tends to discharge the circulating resonance, and reduce its impedance.
For more on this peculiar phenomenon, research "Tank Circuit{s}".
Many DIY, and some Professional, speaker cross-over designers do not know or understand tank circuit effect well enough.
The degree of resonance reduction in both circuit types depends on the amount of resistance.
In the Series L-C-R circuit, the Resistance is the only component of the Impedance at that specific frequency.
In the parallel L//C circuit with either {or both} Series or Parallel Resistance, the total Impedance is purely resistive but is greater than simply the resistance of the resistor - strange as such may seem.
An example of this latter case is the Impedance peak one sees on a plot of impedance versus frequency at the Fs {resonant frequency} of a speaker driver.
This is caused in part by Mechanical equivalents of inductance and capacitance and resistance in the materials which the driver is made from.
If you plotted the mechanical impedance of the resonances in the walls of a speaker enclosure you would find peaks which corresponded to the vibrational resonances in the walls.
The ESR simulating resistor in series with C6/72uF is to reduce significant onset and magnitude of resonance between the capacitive reactance of the 72uF and the inductive reactance of the bass driver's voice-coil, which without the external to driver resistance would be greater audible as the driver will reproduce it whilst it oscillates through the resistance of the voice-coil whilst that voice-coil resistance is reducing it after the signal from the amplifier has ceased sending it.
Thus we need resistance increase in C6, not reactance increase, which changing to 62uF would cause and simply shift the tank resonance to a slightly higher frequency.
Similarly, we add a small amount of resistance to C8/72uF as it is also in parallel with the driver's voice-coil,
even though separated partially by the inductance and resistance of L5,
the effect of L5 will simply reduce and change a little the tank resonance, but not completely.
To completely stop the resonance one would have to apply larger resistors than simply the small values that were in the old electrilytic caps, but such amount of resistance would reduce the high frequency filtering ability of the caps, thus we have to trade-off, and I suggest we simply apply what is as close as possible to what would have been the case in the original speaker when it was new.
____________________________________________________
while rolling off a bit steeper. This would be compensated by more energy emerging from the mid unit at the low end of its range because the resistor of 1.5 ohm padding out the 24 microF capacitor is lower than the ESR of 3 ohm at 500 Hz. That is... the Potential Divider of this L network lets more voltage through to the second L section, and hence to the mid driver.
-----> a little more, not a lot, and remember you are using 24uF with MF500 mid instead of the original 30uF, thus you will be losing some lower mids.
The series resistor changes a Slope of the filter from steeper to gentler, though small change in this 1.5 ohm case.
This is why I suggested in prevoius Post that you may wish to increase the mids output from the bass driver by using 3.3ohm in series with C6, {not with C8, apply first to C6, and decide by listening if enough or too much or not enough}.
____________________________________________________
Please take a look at Tony Gee's audiophile capacitor test:
http://www.humblehomemadehifi.com/Cap.html
- as far as I can tell by looking at this page, Tony was testing capacitors similar to those we sourced:
http://www.madisound.com/manufacturers/solen/fastcaps.php
His scoring: Solen 6.5 SoniCap 8.5
But then SoniCaps are pricier
-----> I had seen and read that awhile ago.
******
Particularly note Tony's tip to add 10nF Vishay Roederstein MKP1837
-----> this is a sound effect caused by the small cap changing the wave-shape of the music, as result of the much faster Pulse Rise Time of the small cap.
The effect is NOT in the recorded music, thus it is a Distortion, even if a pleasant one, but not every-one likes it {there are lots of Posts about this matter around on various Forums}.
It may work OK with some music and not with other music, and more-so with some tweeters and less-so with others.
I may Post more about this matter at some later time , if time available to do so.
___________________________________________________
Some say they cannot hear the difference with Bi-wiring or without. However I have the necessary biwire speaker cables so will biwire.
-----> Bi-wiring works to greater or lesser degree depending on the drivers and the type of x-over circuit, and with the complex x-over in the 66s it is likely to work well and give clearer sound and better dynamics,
to be worth the work involved doing the job !
I have to finish now, but do Post a list of the resistors' values that you have in each Welwyn size, and the number of each.
You can use some of them with little worry about the Inductance.
Don't rush into buying the Riedons yet, and you may need two other resistors now also ... more next time.
correcting a MISTAKE in my above ...
I typed that one too fast !
I wrote :-
"In the parallel L//C circuit with either {or both} Series or Parallel Resistance ... "
... a mistake !
Correct is :-
In the parallel, L//C, circuit with a Series connected Resistance in either or both arm/s of the circuit the total Impedance is purely resistive at the resonant frequency, and is greater than simply the resistance of the resistor, {or the combined result of two resistors if one in each arm}.
____________________________________________________
In that circuit the resonant frequency shifts either up or down depending on which arm has the greater resistance inserted in it.
The parallel, L//C, circuit with a Parallel connected Resistance behaves differently, and is not relevant to the cross-over in the Celestion 66.
___________________________________________________
the Post #217 paragraph continues correctly from :-
"A example of this latter case is the Impedance peak one sees on a plot of ... "
I typed that one too fast !
I wrote :-
"In the parallel L//C circuit with either {or both} Series or Parallel Resistance ... "
... a mistake !
Correct is :-
In the parallel, L//C, circuit with a Series connected Resistance in either or both arm/s of the circuit the total Impedance is purely resistive at the resonant frequency, and is greater than simply the resistance of the resistor, {or the combined result of two resistors if one in each arm}.
____________________________________________________
In that circuit the resonant frequency shifts either up or down depending on which arm has the greater resistance inserted in it.
The parallel, L//C, circuit with a Parallel connected Resistance behaves differently, and is not relevant to the cross-over in the Celestion 66.
___________________________________________________
the Post #217 paragraph continues correctly from :-
"A example of this latter case is the Impedance peak one sees on a plot of ... "
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