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Sonnova Sonnova is offline
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On Sat, 3 Nov 2007 11:39:34 -0700, Arny Krueger wrote
(in article ):

"Sonnova" wrote in message
...

On Thu, 1 Nov 2007 16:08:10 -0700, Arny Krueger wrote
(in article ):


"Sonnova" wrote in message
...


Simple. Hook a bookshelf speaker system rated at "200 watts" to a 25
Watt/channel Wiliamson amplifier and notice that it keeps blowing
tweeters
(and is not oscillating).

The bookshelf tweeter probably has a real-world (not spec sheet) power
capacity of under 10 watts.


Most tweeters are like that,


Not these days, not in quality speakers. Please see my other recent post on
the matter.

that's (one reason) why they have at least a
capacitor in series with them


The capacitor is a part of a filter that routes lows to the woofer and highs
to the tweeters in the interest of smooth response.


Actually, it's purpose is to keep low frequency (and thus large,
low-frequency voltage swings) out of the somewhat fragile tweeters rather
than to route high frequencies to the tweeter - although it does that.


and sometimes a fuse.


Or other part like a light bulb that protects the tweeter from abuse.


Lightbulbs are very nonlinear devices and I would think that they would act
more like a compressor than anything else. I can't imagine that this solution
would sound all that good, but you're right, it would work because as the
filament heated-up, it's impedance would rise.

The fuse doesn't usually
blow in these cases because the cooked tweeter is not due to excess
current,
but rather because it's voice-coil duty cycle has been continuously
exceeded
by a clipping amplifier.


Excess current and exceeding the duty cycle are two ways of describing the
identical same process.


Not exactly. With duty cycle we are dealing with an average amount of AC
current over time, with a fuse we are dealing with peak current, usually
instantaneous (most speaker protection fuses tend to be fast-blow variety).
It is very possible, even probable that a puny amplifier will be unable to
pump out enough current to blow a fuse, but in hard clipping can continually
energize the voice coil of a small speaker like a tweeter, not giving it time
to cool-off between cycles. in such a case, said tweeter overheats and burns
out. All of this without once blowing the fuse. Ferro-fluid in the voice-coil
gap has reduced this phenomenon in most better speaker systems these days,
and most no longer suffer this indignity.

I know a guy who once was powering a pair of Magnapan MG-3s (no letter
suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the
Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan
factory about this, the tech noticed that he had replaced tweeters in his
MG-3's several times. He asked the guy about his peripheral equipment. When
our audiophile mentioned the ST-70, the tech told him that that was the
problem. The amp was blowing the tweeter because it was too small (I had told
him the same thing) and he recommended that the guy replace the amp with
something bigger - on the order of at least 100 Watts/channel. He did so by
replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew another
tweeter. I bought his ST-70 and use it to this day with a pair of Polk
bookshelf speakers connected to my computer. It's fine for that application.
BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my VTL
140's. I never once blew a tweeter and I had those speakers for 12 years.
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Norman M. Schwartz Norman M. Schwartz is offline
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Default speaker efficiency

"Sonnova" wrote in message
...
I know a guy who once was powering a pair of Magnapan MG-3s (no letter
suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the
Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan
factory about this, the tech noticed that he had replaced tweeters in his
MG-3's several times. He asked the guy about his peripheral equipment.
When
our audiophile mentioned the ST-70, the tech told him that that was the
problem. The amp was blowing the tweeter because it was too small (I had
told
him the same thing) and he recommended that the guy replace the amp with
something bigger - on the order of at least 100 Watts/channel.


Isn't the problem here that these speakers of are _both_ low efficiency and
low impedance? Can't any "high current" 100 watt amp can drive these
speakers more easily to high volumes, without clipping, blowing fuses and/or
damaging the ribbons than can any garden variety 200 Watt/channel amp?

He did so by
replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew
another
tweeter.


Adcom amps are famed for their ability to drive LOW impedance loudspeakers.
(Before switching to Bryston monoblocs, I succeeded in driving a pair of
Tympani IVa with a pair of bridged Adcom GFA 555 without incident for many
years.)

I bought his ST-70 and use it to this day with a pair of Polk
bookshelf speakers connected to my computer. It's fine for that
application.
BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my
VTL
140's. I never once blew a tweeter and I had those speakers for 12 years.

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Sonnova Sonnova is offline
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Default speaker efficiency

On Sun, 4 Nov 2007 10:14:07 -0800, Norman M. Schwartz wrote
(in article ):

"Sonnova" wrote in message
...
I know a guy who once was powering a pair of Magnapan MG-3s (no letter
suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the
Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan
factory about this, the tech noticed that he had replaced tweeters in his
MG-3's several times. He asked the guy about his peripheral equipment.
When
our audiophile mentioned the ST-70, the tech told him that that was the
problem. The amp was blowing the tweeter because it was too small (I had
told
him the same thing) and he recommended that the guy replace the amp with
something bigger - on the order of at least 100 Watts/channel.


Isn't the problem here that these speakers of are _both_ low efficiency and
low impedance? Can't any "high current" 100 watt amp can drive these
speakers more easily to high volumes, without clipping, blowing fuses and/or
damaging the ribbons than can any garden variety 200 Watt/channel amp?


Sure, they are fairly low efficiency (88dB/Watt/meter, IIRC), but they aren't
particularly low impedance. But 35-watts/channel is simply too small of an
amplifier and it spent a lot of time in clipping - especially on rock music.

He did so by
replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew
another
tweeter.


Adcom amps are famed for their ability to drive LOW impedance loudspeakers.
(Before switching to Bryston monoblocs, I succeeded in driving a pair of
Tympani IVa with a pair of bridged Adcom GFA 555 without incident for many
years.)


Maggies are a very easy load. Most are 6 ohms and it's almost totally
resistive.

Speaking of the Magneplanar line of Tympani loudspeakers, I once had a pair
of Tympani IIIc (all SIX panels) that I powered with a Hafler 101 amp on the
midrange/top and a Marantz transistor amp (don't remember the model number)
on the bass panels. Never had any trouble with them or the amplifiers with
which I was driving them. What finally made me replace the Tympanis was that
Magneplanar used to use an adhesive to glue the voice grid to the Mylar
diaphragms which was reactive with ultraviolet light. I had the speakers down
at the open end of the living room (these speakers took up a LOT of room and
ended up being 9 ft X 7 ft fully expanded) where they were near the sliding
patio door. On nice days, I'd open the patio doors to let air circulate
through the house and sunlight would stream through the screen door and hit
the Maggies. Over time, this broke the glue down into a substance that
actually attacked the voice-grid wires (which were aluminum) of the tweeter
and midrange panels nearest the door and ate through them! Magneplanar wanted
me to send the entire speaker system back to them to be refurbished and by
the time I would have spent the money to order a couple of shipping crates
from Magneplanar, paid the freight, and the fee they wanted to rebuild the
speakers, I was more than 3/4 of the way to a new pair of MG-3Bs. I sold the
Tympani's to a guy who thought that getting them refurbished was a bargain,
and I bought the MG-3Bs. I have Martin-Logan electrostatics now, but would
dearly love to have a pair of Magnepan MG-20s.

I bought his ST-70 and use it to this day with a pair of Polk
bookshelf speakers connected to my computer. It's fine for that
application.
BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my
VTL
140's. I never once blew a tweeter and I had those speakers for 12 years.


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Norman M. Schwartz Norman M. Schwartz is offline
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Posts: 146
Default speaker efficiency

"Sonnova" wrote in message
...
On Sun, 4 Nov 2007 10:14:07 -0800, Norman M. Schwartz wrote
(in article ):

"Sonnova" wrote in message
...
I know a guy who once was powering a pair of Magnapan MG-3s (no letter
suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the
Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan
factory about this, the tech noticed that he had replaced tweeters in
his
MG-3's several times. He asked the guy about his peripheral equipment.
When
our audiophile mentioned the ST-70, the tech told him that that was the
problem. The amp was blowing the tweeter because it was too small (I had
told
him the same thing) and he recommended that the guy replace the amp with
something bigger - on the order of at least 100 Watts/channel.


Isn't the problem here that these speakers of are _both_ low efficiency
and
low impedance? Can't any "high current" 100 watt amp can drive these
speakers more easily to high volumes, without clipping, blowing fuses
and/or
damaging the ribbons than can any garden variety 200 Watt/channel amp?


Sure, they are fairly low efficiency (88dB/Watt/meter, IIRC), but they
aren't
particularly low impedance. But 35-watts/channel is simply too small of an
amplifier and it spent a lot of time in clipping - especially on rock
music.

He did so by
replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew
another
tweeter.


Adcom amps are famed for their ability to drive LOW impedance
loudspeakers.
(Before switching to Bryston monoblocs, I succeeded in driving a pair of
Tympani IVa with a pair of bridged Adcom GFA 555 without incident for
many
years.)


Maggies are a very easy load. Most are 6 ohms and it's almost totally
resistive.

Speaking of the Magneplanar line of Tympani loudspeakers, I once had a
pair
of Tympani IIIc (all SIX panels) that I powered with a Hafler 101 amp on
the
midrange/top and a Marantz transistor amp (don't remember the model
number)
on the bass panels. Never had any trouble with them or the amplifiers with
which I was driving them.


IIIc 6 panels?; Tympani 1 series are 6 panels (e.g., IU, IC (both 8 ohms,
ID). 8 panels are the tympani III series, tympani III, 8 ohms and tympani
IIIB (4 ohms).

I had tympani IIIB (all EIGHT panels), 4 ohms impedance and neither a "200"
watt amp, (GAS Ampzilla II) nor a 75 watt tube amp (ARC D-76a) could drive
either the tweeter or mid range panels without clipping. Piano chords are
especially demanding of watts and current.

What finally made me replace the Tympanis was that
Magneplanar used to use an adhesive to glue the voice grid to the Mylar
diaphragms which was reactive with ultraviolet light. I had the speakers
down
at the open end of the living room (these speakers took up a LOT of room
and
ended up being 9 ft X 7 ft fully expanded) where they were near the
sliding
patio door. On nice days, I'd open the patio doors to let air circulate
through the house and sunlight would stream through the screen door and
hit
the Maggies. Over time, this broke the glue down into a substance that
actually attacked the voice-grid wires (which were aluminum) of the
tweeter
and midrange panels nearest the door and ate through them!


I had Tympani ICs (6panels!) and UV in skylight coming through closed
windows broke down that adhesive! (At least that's what Magnepan informed
could, would and did happen), and BTW having the cartons for these Tympanis,
I DID have them refurbished; the tweeters were replaced (too far damaged)
and everything with the UV-resistant resistant glue.

Magneplanar wanted
me to send the entire speaker system back to them to be refurbished and by
the time I would have spent the money to order a couple of shipping crates
from Magneplanar, paid the freight, and the fee they wanted to rebuild the
speakers, I was more than 3/4 of the way to a new pair of MG-3Bs. I sold
the
Tympani's to a guy who thought that getting them refurbished was a
bargain,
and I bought the MG-3Bs. I have Martin-Logan electrostatics now, but would
dearly love to have a pair of Magnepan MG-20s.

I bought his ST-70 and use it to this day with a pair of Polk
bookshelf speakers connected to my computer. It's fine for that
application.
BTW, I too had a pair of Maggie's; MG-3B's in my case, running off of my
VTL
140's. I never once blew a tweeter and I had those speakers for 12
years.


  #45   Report Post  
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Sonnova Sonnova is offline
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Posts: 1,337
Default speaker efficiency

On Sun, 4 Nov 2007 19:25:24 -0800, Norman M. Schwartz wrote
(in article ):

"Sonnova" wrote in message
...
On Sun, 4 Nov 2007 10:14:07 -0800, Norman M. Schwartz wrote
(in article ):

"Sonnova" wrote in message
...
I know a guy who once was powering a pair of Magnapan MG-3s (no letter
suffix) with a Dyna Stereo 70. It sounded fine, but he kept blowing the
Maggies' ribbon tweeters. Once, while talking to a tech at the Magnapan
factory about this, the tech noticed that he had replaced tweeters in
his
MG-3's several times. He asked the guy about his peripheral equipment.
When
our audiophile mentioned the ST-70, the tech told him that that was the
problem. The amp was blowing the tweeter because it was too small (I had
told
him the same thing) and he recommended that the guy replace the amp with
something bigger - on the order of at least 100 Watts/channel.

Isn't the problem here that these speakers of are _both_ low efficiency
and
low impedance? Can't any "high current" 100 watt amp can drive these
speakers more easily to high volumes, without clipping, blowing fuses
and/or
damaging the ribbons than can any garden variety 200 Watt/channel amp?


Sure, they are fairly low efficiency (88dB/Watt/meter, IIRC), but they
aren't
particularly low impedance. But 35-watts/channel is simply too small of an
amplifier and it spent a lot of time in clipping - especially on rock
music.

He did so by
replacing the Dyna with an ADCOM GFA-5500 (200 W/PC) and never blew
another
tweeter.

Adcom amps are famed for their ability to drive LOW impedance
loudspeakers.
(Before switching to Bryston monoblocs, I succeeded in driving a pair of
Tympani IVa with a pair of bridged Adcom GFA 555 without incident for
many
years.)


Maggies are a very easy load. Most are 6 ohms and it's almost totally
resistive.

Speaking of the Magneplanar line of Tympani loudspeakers, I once had a
pair
of Tympani IIIc (all SIX panels) that I powered with a Hafler 101 amp on
the
midrange/top and a Marantz transistor amp (don't remember the model
number)
on the bass panels. Never had any trouble with them or the amplifiers with
which I was driving them.


IIIc 6 panels?; Tympani 1 series are 6 panels (e.g., IU, IC (both 8 ohms,
ID). 8 panels are the tympani III series, tympani III, 8 ohms and tympani
IIIB (4 ohms).

I had tympani IIIB (all EIGHT panels), 4 ohms impedance and neither a "200"
watt amp, (GAS Ampzilla II) nor a 75 watt tube amp (ARC D-76a) could drive
either the tweeter or mid range panels without clipping. Piano chords are
especially demanding of watts and current.


You are correct. I miss-remembered, the IIIs did have EIGHT panels, the bass
panels for each channel were doubled-up (4) and then one each on both sides
for midrange and tweeter panels. After all, it's been more than 20 years!
However, I had no problem driving these speakers with the Hafler 101 and the
200W/channel Marantz, but then my listening room wasn't all that big (14 X 16
or thereabouts).

What finally made me replace the Tympanis was that
Magneplanar used to use an adhesive to glue the voice grid to the Mylar
diaphragms which was reactive with ultraviolet light. I had the speakers
down
at the open end of the living room (these speakers took up a LOT of room
and
ended up being 9 ft X 7 ft fully expanded) where they were near the
sliding
patio door. On nice days, I'd open the patio doors to let air circulate
through the house and sunlight would stream through the screen door and
hit
the Maggies. Over time, this broke the glue down into a substance that
actually attacked the voice-grid wires (which were aluminum) of the
tweeter
and midrange panels nearest the door and ate through them!


I had Tympani ICs (6panels!) and UV in skylight coming through closed
windows broke down that adhesive! (At least that's what Magnepan informed
could, would and did happen), and BTW having the cartons for these Tympanis,
I DID have them refurbished; the tweeters were replaced (too far damaged)
and everything with the UV-resistant resistant glue.


IIRC, that they wanted something like $250 for a set of crates, another $300
for round-trip shipping by truck and something like $1200 to rebuild them.
They did say that the rebuild included new tweeter panels, new Mylar
diaphragms all-round and that they had changed to a new adhesive for the
voice-grid wires that was not sensitive to UV. I do remember the name of the
guy I dealt with at Magneplanar because it was, what I thought, an unusual
name: Wendell Diller.


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Norman M. Schwartz Norman M. Schwartz is offline
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Posts: 146
Default speaker efficiency

"Sonnova" wrote in message
...
either the tweeter or mid range panels without clipping. Piano chords are
especially demanding of watts and current.


You are correct. I miss-remembered, the IIIs did have EIGHT panels, the
bass
panels for each channel were doubled-up (4) and then one each on both
sides
for midrange and tweeter panels. After all, it's been more than 20 years!
However, I had no problem driving these speakers with the Hafler 101 and
the
200W/channel Marantz, but then my listening room wasn't all that big (14 X
16
or thereabouts).


Well, we have come full circle here. Your IIIs, just as all the Tympanis, up
to the 1C, were both low efficiency _AND_ of 8 ohm ("purely resistive")
impedance. That's why the were/are comfortably driven by your amps and well
as my Audio Reseach Corporation tubed D-76As (75 watts). Then came the
Tympani IIIB, the 1D, the IV and IVa; their impedance was decreased.
Reading from my Tympani IVa manual; Bass--4ohms, Midrange and ribbon
tweeter--3ohms. These low impedance loads "suck" the current out of those
Hafler amps (as they did all of mine) and most of the amps of their day.
Having attempted it I can testify to the fact that one needs a "high
current" amp to drive today's big Maggies. I do successfuly drive their baby
SMG to loud volumes in a secondary system in a very large room with the 200
watt Ampzilla II, blowing no fuses (neither amp nor speaker), nor destroy
speaker drivers.

IIRC, that they wanted something like $250 for a set of crates,


I stored mine. (The "crates", being the cartons they were delivered in.)

another $300
for round-trip shipping by truck and something like $1200 to rebuild them.
They did say that the rebuild included new tweeter panels, new Mylar
diaphragms all-round and that they had changed to a new adhesive for the
voice-grid wires that was not sensitive to UV. I do remember the name of
the
guy I dealt with at Magneplanar because it was, what I thought, an unusual
name: Wendell Diller.


I provided the receipt for the rebuild of my Tympani 1C to the person I sold
them to, so I can't quote my cost. (Shipping those 8 panels is more costly
than 6 panels.) I was very pleased with my rebuilt speakers, they both
looked and sounded better than new, everything was new including the
terminals. As I spoke to him via telephone about 6 months ago, I can testify
that Mr.Diller was still working there. Magnepan's customer support is
outstanding as is their repairs department. They deserve every ounce of the
high regard in which they are held.
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Sonnova Sonnova is offline
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Posts: 1,337
Default speaker efficiency

On Tue, 6 Nov 2007 16:03:40 -0800, Norman M. Schwartz wrote
(in article ):

"Sonnova" wrote in message
...
either the tweeter or mid range panels without clipping. Piano chords are
especially demanding of watts and current.


You are correct. I miss-remembered, the IIIs did have EIGHT panels, the
bass
panels for each channel were doubled-up (4) and then one each on both
sides
for midrange and tweeter panels. After all, it's been more than 20 years!
However, I had no problem driving these speakers with the Hafler 101 and
the
200W/channel Marantz, but then my listening room wasn't all that big (14 X
16
or thereabouts).


Well, we have come full circle here. Your IIIs, just as all the Tympanis, up
to the 1C, were both low efficiency _AND_ of 8 ohm ("purely resistive")
impedance. That's why the were/are comfortably driven by your amps and well
as my Audio Reseach Corporation tubed D-76As (75 watts). Then came the
Tympani IIIB, the 1D, the IV and IVa; their impedance was decreased.
Reading from my Tympani IVa manual; Bass--4ohms, Midrange and ribbon
tweeter--3ohms. These low impedance loads "suck" the current out of those
Hafler amps (as they did all of mine) and most of the amps of their day.
Having attempted it I can testify to the fact that one needs a "high
current" amp to drive today's big Maggies. I do successfuly drive their baby
SMG to loud volumes in a secondary system in a very large room with the 200
watt Ampzilla II, blowing no fuses (neither amp nor speaker), nor destroy
speaker drivers.

IIRC, that they wanted something like $250 for a set of crates,


I stored mine. (The "crates", being the cartons they were delivered in.)

another $300
for round-trip shipping by truck and something like $1200 to rebuild them.
They did say that the rebuild included new tweeter panels, new Mylar
diaphragms all-round and that they had changed to a new adhesive for the
voice-grid wires that was not sensitive to UV. I do remember the name of
the
guy I dealt with at Magneplanar because it was, what I thought, an unusual
name: Wendell Diller.


I provided the receipt for the rebuild of my Tympani 1C to the person I sold
them to, so I can't quote my cost. (Shipping those 8 panels is more costly
than 6 panels.) I was very pleased with my rebuilt speakers, they both
looked and sounded better than new, everything was new including the
terminals. As I spoke to him via telephone about 6 months ago, I can testify
that Mr.Diller was still working there. Magnepan's customer support is
outstanding as is their repairs department. They deserve every ounce of the
high regard in which they are held.


Oh, I agree, but these days I'm real happy with my Martin-Logan Vantages.
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