Supravox:
I agree that when one is spending 1000 Euros that one can't take any chances. I wonder if the QC problems are just the field coil versions. Even Fertin seems to have a problem coming to terms with the weight that loads the driver basket. On this thead we have heard about the bolted frame loosening up.
I am actually looking at the 215 midels which cost a rather reasonable 170 euro ea. AND was planning on using a tweeter (some models seem to have better respnse than others) But even that is too much if they fall apart and I am stuck with them thousands of miles away! I guess we have to rely on our french friends to keep us informed as to when the products are worthy of buying. One trick The Supra people have appears to be using multiple layers of paper to make the cones. Constrained layer damping-a good idea.
As far as the lacquer goes. It continually amazes me that people assume that a high end speaker manufacturer hasn't considered brushing thier speaker cones with lacquer. (this is the mentality that "they are all idiots" ) I'm sure it sometimes does help-especially with cheaper speakers, but to do something irriversable like this seems pretty silly to me. The C37 stuff is marketed -yes marketed, as a panacea to be slapped on any and all parts of your system. To add more injury to insult, people probably use multiple thick layers-"If a little is good then.....
So I think the lacquer disaster on that guys drivers is more a commentary on human nature than the sound of the drivers 🙄 Hey-I know- lets glue a second layer of paper on yourFertin cones!!! over your dead body I'll bet!😀
I agree that when one is spending 1000 Euros that one can't take any chances. I wonder if the QC problems are just the field coil versions. Even Fertin seems to have a problem coming to terms with the weight that loads the driver basket. On this thead we have heard about the bolted frame loosening up.
I am actually looking at the 215 midels which cost a rather reasonable 170 euro ea. AND was planning on using a tweeter (some models seem to have better respnse than others) But even that is too much if they fall apart and I am stuck with them thousands of miles away! I guess we have to rely on our french friends to keep us informed as to when the products are worthy of buying. One trick The Supra people have appears to be using multiple layers of paper to make the cones. Constrained layer damping-a good idea.
As far as the lacquer goes. It continually amazes me that people assume that a high end speaker manufacturer hasn't considered brushing thier speaker cones with lacquer. (this is the mentality that "they are all idiots" ) I'm sure it sometimes does help-especially with cheaper speakers, but to do something irriversable like this seems pretty silly to me. The C37 stuff is marketed -yes marketed, as a panacea to be slapped on any and all parts of your system. To add more injury to insult, people probably use multiple thick layers-"If a little is good then.....
So I think the lacquer disaster on that guys drivers is more a commentary on human nature than the sound of the drivers 🙄 Hey-I know- lets glue a second layer of paper on yourFertin cones!!! over your dead body I'll bet!😀
SUPRA VALID POINT
Hi,
As far as I can tell,one singled out person having had a misfortune (maybe even self-inflicted) doesn't tell the whole story.
Fine,so QC may not be up to par but how many really high end companies are?
I wonder.
Naturally in these small audio circles news travels fast and bad news even faster.
Amongst my friends are at least ten that use the Supravox and are aware of Fertin's existence.
None of them has had any quality problem with the Supravox so far.
So what if you want to use a tickler tweeter?
We do have a choice don't we?
Fertin speakers may not need it,but I see no point in advocating wideband preamps and amps to killl the spectrum on the receiving end.
What's the point of this anyway?
From what I can observe neither Fertin nor Supravox are perfect but surely at 1.000 bucks a pop I won't buy either of them if they didn't come with some sort of warranty against manufacturing defects?
All too many people abuse their speakers and in that case I would void warranty as well,but as long as this hasn't been firmly established I would honour customers.
After all even handmade small run speakers sold factory direct should allow for some margins,wouldn't you think?
And don't you think the Fertins are less fragile when it comes to fixing them and supporting them to a baffle.They're not.
What's the point in pursuing something that is so far out of reach even to people living just across the border?
I visited the Lowther factory and talked to the people behind the speakers and still found them a PITA to deal with.
I can only conclude that companies like Fertin want to remain small and keep a low profile but if it takes me six months to get my goods they better live up to my expectations.
As far as doping speakers with C37 or whatever goes,I always shy away from irreversible tweaks no matter what anybody says about results until I'm absolutely convinced about these results.
Sounds pretty much like politics to me,
Cheers,
Hi,
As far as I can tell,one singled out person having had a misfortune (maybe even self-inflicted) doesn't tell the whole story.
Fine,so QC may not be up to par but how many really high end companies are?
I wonder.
Naturally in these small audio circles news travels fast and bad news even faster.
Amongst my friends are at least ten that use the Supravox and are aware of Fertin's existence.
None of them has had any quality problem with the Supravox so far.
So what if you want to use a tickler tweeter?
We do have a choice don't we?
Fertin speakers may not need it,but I see no point in advocating wideband preamps and amps to killl the spectrum on the receiving end.
What's the point of this anyway?
From what I can observe neither Fertin nor Supravox are perfect but surely at 1.000 bucks a pop I won't buy either of them if they didn't come with some sort of warranty against manufacturing defects?
All too many people abuse their speakers and in that case I would void warranty as well,but as long as this hasn't been firmly established I would honour customers.
After all even handmade small run speakers sold factory direct should allow for some margins,wouldn't you think?
And don't you think the Fertins are less fragile when it comes to fixing them and supporting them to a baffle.They're not.
What's the point in pursuing something that is so far out of reach even to people living just across the border?
I visited the Lowther factory and talked to the people behind the speakers and still found them a PITA to deal with.
I can only conclude that companies like Fertin want to remain small and keep a low profile but if it takes me six months to get my goods they better live up to my expectations.
As far as doping speakers with C37 or whatever goes,I always shy away from irreversible tweaks no matter what anybody says about results until I'm absolutely convinced about these results.
Sounds pretty much like politics to me,
Cheers,
Variac said:
The mounting point for the RCAs pictures was a pr of big bolt holes (and big bolts) coming right off the electro-magnets horseshoe. The front was press fittied against the baffle. Anything this heavy really needs to be supported under the magnet.
dave
Fertin "problems"
All,
Jean Michel LeCleac'h, the person who told me about the Supravox problems does not own those drivers himself, he reports problems at public events like hifi shows with things like the magnet coming off. More than one event (methinks, a company not managing to have flawless products for demo at a hifi fair where it is utterly important to make a 1st class impression, is not winning my trust with a $2000 per pair product). Additionally he reports problems some buddies of him had. So far i have no reason to doubt what he reports, 1st Jean-Michel has no stock in that deal himself (he is into hornspeakers and Onken-like EBR emclosures) and nothing to win or lose and 2nd, i know him personally and would go as far as to buy a used car from him.
He also reported there are Supravox out there performing very well.
The only amplifiers i know so far going spung when input signal applied and the OPT secondary deprived from the load are tube amplifiers like the one i am using.
As the eventual current peak suddenly finds no load to work into and the rising voltage fighting to make the current flow anyway causes winding2winding shorts.
But, i asked a competent EE buddy, under unlucky circumstances a SS amp can blow as well, for instance if the output devices stand 50V and the B+ is 49 V. At ear-deafening levels the speaker and its XO could surge high enough to kill the output devices....
I do not deny that a differential/PP preamp is the best place to do the absolute polarity switching. Will be hard to do it with a SE topology, particularly with tube/OPT preamps as inverting polarity of an OPT at least costs sonic deterioation; it may cause further problems.
But switching at the speaker is better than nothing, it works fine as i did it -- one does not have to do the switching at insane levels, on can mute the preamp signal too.
Fertin:
i'd like to tell you all i initially had problems with my Fertins. A packing mistake damaged one whizzer cone. Herr Kühn from BlackForest Audio managed to get me a matched pair back and i had to pay no further money. I was very satisfied with that way to handle it, he could have claimed i did the damage and it would have been next to impossible for me to prove i did not.
Basket not stable: traditonally those drivers with heavy motors and practically all FC drivers are to be mounted at the motor. From my understanding the Fertin basket is prone to break somewhen in the future if the basket alone carries the motor.
This is not a manufacturing flaw, this is due to basket design and the statement comes from me personally out of my understanding as mechanical designer: under flexation the glue joints get some peeling-type stress and according TME glue joints do not survive peeling stress under vibration forever. I personally have no problem with that as the motor has an M10 tapped hole at the backside, allowing safe and stable mounting.
----------
Greets,
Bernhard
### moderator edit ###
I have abridged my post; it had statements in it no longer applying and i apologize for the initial nuisance aswell as for the delay of this removal remark.
dice45
All,
Jean Michel LeCleac'h, the person who told me about the Supravox problems does not own those drivers himself, he reports problems at public events like hifi shows with things like the magnet coming off. More than one event (methinks, a company not managing to have flawless products for demo at a hifi fair where it is utterly important to make a 1st class impression, is not winning my trust with a $2000 per pair product). Additionally he reports problems some buddies of him had. So far i have no reason to doubt what he reports, 1st Jean-Michel has no stock in that deal himself (he is into hornspeakers and Onken-like EBR emclosures) and nothing to win or lose and 2nd, i know him personally and would go as far as to buy a used car from him.
He also reported there are Supravox out there performing very well.
The only amplifiers i know so far going spung when input signal applied and the OPT secondary deprived from the load are tube amplifiers like the one i am using.
As the eventual current peak suddenly finds no load to work into and the rising voltage fighting to make the current flow anyway causes winding2winding shorts.
But, i asked a competent EE buddy, under unlucky circumstances a SS amp can blow as well, for instance if the output devices stand 50V and the B+ is 49 V. At ear-deafening levels the speaker and its XO could surge high enough to kill the output devices....
I do not deny that a differential/PP preamp is the best place to do the absolute polarity switching. Will be hard to do it with a SE topology, particularly with tube/OPT preamps as inverting polarity of an OPT at least costs sonic deterioation; it may cause further problems.
But switching at the speaker is better than nothing, it works fine as i did it -- one does not have to do the switching at insane levels, on can mute the preamp signal too.
Fertin:
i'd like to tell you all i initially had problems with my Fertins. A packing mistake damaged one whizzer cone. Herr Kühn from BlackForest Audio managed to get me a matched pair back and i had to pay no further money. I was very satisfied with that way to handle it, he could have claimed i did the damage and it would have been next to impossible for me to prove i did not.
Basket not stable: traditonally those drivers with heavy motors and practically all FC drivers are to be mounted at the motor. From my understanding the Fertin basket is prone to break somewhen in the future if the basket alone carries the motor.
This is not a manufacturing flaw, this is due to basket design and the statement comes from me personally out of my understanding as mechanical designer: under flexation the glue joints get some peeling-type stress and according TME glue joints do not survive peeling stress under vibration forever. I personally have no problem with that as the motor has an M10 tapped hole at the backside, allowing safe and stable mounting.
----------
Greets,
Bernhard
### moderator edit ###
I have abridged my post; it had statements in it no longer applying and i apologize for the initial nuisance aswell as for the delay of this removal remark.
dice45
I'm surprised that you make a distinction between bad design and bad quality control. They both result in broken speakers.
I understand that the Fertin problem can be cicumvented by careful mounting, but it would be nice if a $1000 item was designed competently. Even if they are assuming the motor is mounted to support it, I still think (and really it appears that you also, from your words) the construction should certainly be better.
As to Supravox, I think your sample is pretty small. It certainly points to a big problem, but In fact it could be limited to just the models with field coil.(I realize this thread is about a field coil speaker though) In fact the magnet falling off at the show might have been due to shipping damage. I think your warning was very timely, but I think you should also consider that more investigation is merited before stating that there is a huge problem with Supravox speakers. Without any more information I have to admit I'm not too enthusiastic about ordering any though!! BUT, I now know about a speaker company that has quite interesting products, unique in fact, and will try to find out more about them. For this I am greatful to FDegrove. I hope someone else knows about them and will enlighten us
HI Variac,
you wondered why c37 (if that is just proper coating) is not applied by manufacturers.
So did I..
Now a friend told me, that in speaker manufacturing it was very costly to apply a coat and let it dry, even more so with thin 5-20 thin coatings.
C37 maybe
the opposite of what the industry does. E.g. Audax with their HDA series- applying a foil- quick and easy.
So it may be for obvious reasons no mass producer does coat drivers in such a way.
??
kind regards
Philipp
you wondered why c37 (if that is just proper coating) is not applied by manufacturers.
So did I..
Now a friend told me, that in speaker manufacturing it was very costly to apply a coat and let it dry, even more so with thin 5-20 thin coatings.
C37 maybe
the opposite of what the industry does. E.g. Audax with their HDA series- applying a foil- quick and easy.
So it may be for obvious reasons no mass producer does coat drivers in such a way.
??
kind regards
Philipp
I can see that applying multiple layers of a liquid can get costly, but I also find it impossible to believe that putting this stuff on a carefully engineered product is always going to be an improvement
Hi Mark,
needn´t always do good, you are right.
Careful designed however may mean-
-> careful designed, but cost effective
See what I mean?
I would not go further than use it onusual paper-cones, given the c37 is applied very thin & in many coats right now
btw I do have experienced the C37 plus papercones being a great synergy in my case 😎
kind regards
Philipp
needn´t always do good, you are right.
Careful designed however may mean-
-> careful designed, but cost effective
See what I mean?
I would not go further than use it onusual paper-cones, given the c37 is applied very thin & in many coats right now
btw I do have experienced the C37 plus papercones being a great synergy in my case 😎
kind regards
Philipp
I see what you mean, your argument makes a lot of sense and more importantly you have clearly heard the difference, which always counts for a lot around here. Lots of people have an opinion without doing the work (especially me!) 😉
Fertin basket
Mark,
i pointed out the glue joint thing is my paranoia, maybe they don't break, who knows. And who knows, maybe there are recessed rivets buried under the basket's powder coating, i was assuming this is a glue joint.
My impression, looking at the driver, is that it is quite competently designed.
The Fertin 20EX is made in in small quantities and having a basket die-casted is maybe not the smartest move.
The chosen solution results in a basket not impeding the air too much and making use of a 12mm thick pole plate having tapped holes. Allowing the basket and spider to be independently adjusted for concentricity.
I have not mused if and how a hypothetical die-casted basket would stand the stress.
I would certainly not suggest to mount the Fertin's FC motor on a PHY-style basket.
Then, have a look at the Lowther PM4A.
No FC, just a very heavy AlNiCo magnet.
Have a look! the magnet has a flange, a foot.
Ok, may i suggest you ignore my warnings? I have no stock options here. Go ahead, order from Supravox!
You know what upsets me, Mark?
My intention is to provide info for maximum success of anyone pondering if to follow that path. Obvioulsy not appreciated.
Better, i keep my toys for myself and make a product ou of my ideas .... and stop making a fool out of myself here.
----------
Bernhard
Mark,
i pointed out the glue joint thing is my paranoia, maybe they don't break, who knows. And who knows, maybe there are recessed rivets buried under the basket's powder coating, i was assuming this is a glue joint.
My impression, looking at the driver, is that it is quite competently designed.
The Fertin 20EX is made in in small quantities and having a basket die-casted is maybe not the smartest move.
The chosen solution results in a basket not impeding the air too much and making use of a 12mm thick pole plate having tapped holes. Allowing the basket and spider to be independently adjusted for concentricity.
I have not mused if and how a hypothetical die-casted basket would stand the stress.
I would certainly not suggest to mount the Fertin's FC motor on a PHY-style basket.
Then, have a look at the Lowther PM4A.
No FC, just a very heavy AlNiCo magnet.
Have a look! the magnet has a flange, a foot.
Ok, may i suggest you ignore my warnings? I have no stock options here. Go ahead, order from Supravox!
You know what upsets me, Mark?
My intention is to provide info for maximum success of anyone pondering if to follow that path. Obvioulsy not appreciated.
Better, i keep my toys for myself and make a product ou of my ideas .... and stop making a fool out of myself here.
----------
Bernhard
It seems to me you are getting too upset. That is the only way you could make a fool out of yourself here. You certainly wouldn't want to be the sort of person that threatens to take his toys and go home.. something you once accused me of. Perhaps you had this reaction because the Supravox comments were mixed in with Frank's phase comments. In fact, that was what I was trying to ameliorate a bit- I felt your comments to Frank about the Supra recomendation were excessive, about phase more justified. I think your comment was valid, but feel that the truth is that we really don't have enough info on all the Supra products, etc. and should stay open minded to more info, rather than demanding that all agree with you and your friend that they are crap. My Supravox interest was not for field coils at all and I will return to the thread where the lower level models were being discussed. It is these lower level models that I was considering and shouldn't have entered the fray regarding the field coils. In fact I have decided to not discuss speakers at all anymore until I have finished mine. Interestingly they will have Fostex drivers instead of Supravox because I want to buy them soon and I don't have enough info on Supravox-reliability to risk buying them after your warning! Plus the Fostex look really cool!
Variac said:
I don't think you will be disappointed with the Fostex. They should be a magnificient driver. There is probably as much research in that single driver as has been spent to get Supravox going -- not to say that throwing huge amounts of money at something make them better -- but the Fostexs are well thought out -- now if they would just start making them with alnico or neo or field-coils ... yummmm
dave
Greets,
I have read with great interest the thread on the Fertins and would be interested in the group purchase.
The only experience I have with FR was a pair of Lowthers in Medallion II cabs but sold those and now use some Unity speakers/TAD2001 and Altec 828/515. The FR concept just seems more elegant.
Keep me posted!
Thanks!
Bob.Obo
I have read with great interest the thread on the Fertins and would be interested in the group purchase.
The only experience I have with FR was a pair of Lowthers in Medallion II cabs but sold those and now use some Unity speakers/TAD2001 and Altec 828/515. The FR concept just seems more elegant.
Keep me posted!
Thanks!
Bob.Obo
fertins
I guess nothing is going to happen with FC drivers in this context.
Just as well. Unusually, I have the money but no time to start a speaker development project just now and I know I can get Fertins from Black Forest. Still, if anyone comes up with a smokin' deal on FC drivers, contact me privately at phclark@qwest.net. I'm taking this thread off my personal bar.
It's been a slice.
Peter C
I guess nothing is going to happen with FC drivers in this context.
Just as well. Unusually, I have the money but no time to start a speaker development project just now and I know I can get Fertins from Black Forest. Still, if anyone comes up with a smokin' deal on FC drivers, contact me privately at phclark@qwest.net. I'm taking this thread off my personal bar.
It's been a slice.
Peter C
Just curious, do y'all think this driver would be good for an open baffle? If not, what type of cabinet do you think? If (big if) I did this, I would be mating it with the LeRibbon tweeter....
MANUFACTURER: ATD
MODEL 17LB
DATE 10/3/2001
Fs 99.7823
Cone Diameter 130.0000
ZMax 36.4923
Re 6.0000
Qms 4.1739
Qes 0.8213
Qts 0.6863
Mms 6.10g
Vas 19.5
dBSPL 92
Power: 100W
L 1kHz 0.7270
L 10kHz 0.1338
Z Min 6.6145
Z AVG 10.2670
http://e-speakers.com/products/atd-wide-range.html
http://e-speakers.com/products/atd-tweeters.html
At 1/3 the cost of a Fertin setup, you think it would sound decent? I'm interested in experimenting/experiencing the open baffle sound but at a lower cost.
MANUFACTURER: ATD
MODEL 17LB
DATE 10/3/2001
Fs 99.7823
Cone Diameter 130.0000
ZMax 36.4923
Re 6.0000
Qms 4.1739
Qes 0.8213
Qts 0.6863
Mms 6.10g
Vas 19.5
dBSPL 92
Power: 100W
L 1kHz 0.7270
L 10kHz 0.1338
Z Min 6.6145
Z AVG 10.2670
http://e-speakers.com/products/atd-wide-range.html
http://e-speakers.com/products/atd-tweeters.html
At 1/3 the cost of a Fertin setup, you think it would sound decent? I'm interested in experimenting/experiencing the open baffle sound but at a lower cost.
Fs of 100 is a little high, you need a bass unit to complement this driver.
Depending on the size of the baffle, I believe there would be a problem with how much air the driver can move = not enough linear travel of the voice coil.
Also there is a 5dB peak at 4kHz that looks ugly and needs a notch filter.
So... view this driver as a midrange in a 3-way!
/Peter
Depending on the size of the baffle, I believe there would be a problem with how much air the driver can move = not enough linear travel of the voice coil.
Also there is a 5dB peak at 4kHz that looks ugly and needs a notch filter.
So... view this driver as a midrange in a 3-way!
/Peter
rear sound radiation & bass
There is the posibility to cover the backside of the driver with cloth, wool or glassfiber. this will increase the power handling in the bassregion, give a little more bass output, & it also makes it less important to treat the wall behind the speakers with absorbing material. This calls for a bit of trial & error, but if it results in a better sounding speaker... I'm going to try it on my (really ugly)open baffles anyway...
/Per
There is the posibility to cover the backside of the driver with cloth, wool or glassfiber. this will increase the power handling in the bassregion, give a little more bass output, & it also makes it less important to treat the wall behind the speakers with absorbing material. This calls for a bit of trial & error, but if it results in a better sounding speaker... I'm going to try it on my (really ugly)open baffles anyway...
/Per
DONE THAT.
Hi,
IME,it takes away the openness of the OB and you don't get more bass out of it anyway.
Try it if you like though,😉
Hi,
IME,it takes away the openness of the OB and you don't get more bass out of it anyway.
Try it if you like though,😉
You can try with a Tipole arrangement like my bass section on Tipolo project
ciao
Filippo
www.audiofanatic.it
ciao
Filippo
www.audiofanatic.it
Final Chapter
Dave at one point suggested an angled cut to hole on the fieldcoil side of the driver. I did that and it opened up the soundstage in every direction. Thanks, Dave.
Now reasonably confident that the drivers have run in I would characterize the strong points of the driver/open baffle as: singing, lilting presentation and oustanding presence/transparency. Bass did eventually fill in and is reasonable enough with careful placement.
During the course of the thread we noted that low powered pp suited these speakers more than SET but no explanation was offered why this is so. Recently, on another board, KYW offered this little nugget:
"> I suppose the conclusion is there will be advantage in
> using field coil drivers in an OB where one can change
> the driver Q to suit.
Up to a point - yes. You really need to start with a Driver having a Qe of 0.5 or more (up to Qe 1.5 or so will be okay) and a sufficiently large baffle. The lower the Driver Qe for a given Fs the larger the baffle has to be (plane baffle, folding back "wings are an idea that is not ideal acoustically IMHO) for the same LF cutoff.
Go below 0.5 Driver Qe and you will NEVER have a large enough baffle to get a reasonably flat response at LF. You can BTW raise the Drivers effective Qe by driving it from a high source Impedance Amplifier.
For example, Brian Cherry uses a PP Amp with 45's that I would estimate to have around 6.5 - 8 Ohm output Impedance without negative feedback used. He comments how this amplifier produces much better bass with his open baffle Fertin's than the Billie Kit, which of course has "only" around 2.5 Ohm output Impedance.
If we do the numbers, using the high output impedance Amplifier will almost double the Qe, so our Qe = 0.45 Fertin de facto turns into Qe = 0.9. On comparison the 300B SE Amplifier will raise the Qe only to around 0.6.
The above should also explain why Brian finds the high output impedance Amplifier a little uncontrolled on Box Speakers where the 300B SE Amp rules."
I include this just to complete the discussion for reference.
Thanks to all for their input.
Brian
Dave at one point suggested an angled cut to hole on the fieldcoil side of the driver. I did that and it opened up the soundstage in every direction. Thanks, Dave.
Now reasonably confident that the drivers have run in I would characterize the strong points of the driver/open baffle as: singing, lilting presentation and oustanding presence/transparency. Bass did eventually fill in and is reasonable enough with careful placement.
During the course of the thread we noted that low powered pp suited these speakers more than SET but no explanation was offered why this is so. Recently, on another board, KYW offered this little nugget:
"> I suppose the conclusion is there will be advantage in
> using field coil drivers in an OB where one can change
> the driver Q to suit.
Up to a point - yes. You really need to start with a Driver having a Qe of 0.5 or more (up to Qe 1.5 or so will be okay) and a sufficiently large baffle. The lower the Driver Qe for a given Fs the larger the baffle has to be (plane baffle, folding back "wings are an idea that is not ideal acoustically IMHO) for the same LF cutoff.
Go below 0.5 Driver Qe and you will NEVER have a large enough baffle to get a reasonably flat response at LF. You can BTW raise the Drivers effective Qe by driving it from a high source Impedance Amplifier.
For example, Brian Cherry uses a PP Amp with 45's that I would estimate to have around 6.5 - 8 Ohm output Impedance without negative feedback used. He comments how this amplifier produces much better bass with his open baffle Fertin's than the Billie Kit, which of course has "only" around 2.5 Ohm output Impedance.
If we do the numbers, using the high output impedance Amplifier will almost double the Qe, so our Qe = 0.45 Fertin de facto turns into Qe = 0.9. On comparison the 300B SE Amplifier will raise the Qe only to around 0.6.
The above should also explain why Brian finds the high output impedance Amplifier a little uncontrolled on Box Speakers where the 300B SE Amp rules."
I include this just to complete the discussion for reference.
Thanks to all for their input.
Brian
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