what is the cresendo amps well wat ive heard that these are the only amps which drives the tripple 270mm or quad 270mm magnet based woofers.... and he said that the magnet size is overdamped...so we have to use something really powerful amp...
but what cresendo means???
why cant chip amps drive such huge drivers....?
If so velodyne uses the class D chip amps to drive their monsters...
what can class D chip amps drive the Huge magnet structed Woofers?
but what cresendo means???
why cant chip amps drive such huge drivers....?
If so velodyne uses the class D chip amps to drive their monsters...
what can class D chip amps drive the Huge magnet structed Woofers?
hi
most probably people in chip amps will not be able to help , post this in solid state (where all the solid guys are actually ) and ull get all your repies
suranjan
most probably people in chip amps will not be able to help , post this in solid state (where all the solid guys are actually ) and ull get all your repies
suranjan
Yes,
and later on the 'Millennium Crescendo' ...
Very cool design but belongs to the solid state fraction. 😉
mik
and later on the 'Millennium Crescendo' ...
Very cool design but belongs to the solid state fraction. 😉
mik
Jep, I made dozens of them. Never a problem. Lots of mods. and rock stable. The best amp. Elektor ever made. Made all the amps. from Elektor but this 1 stayed. Still use 4 of them.
Wasn't it the original Crescendo that oscillated quite frequently ( or was that the other, later one ? ).
yes, jean-paul. It was the first Crescendo amp (1982) that oscillated pretty havely when used wired wound resistors. Mine amp runs perfectly since 1998.
With the Crescendo ME, I had first also a few problems wih oscillation, but these were solved by making better PCBs.
But I wouldn't know why many other amps couldn't drive these woofers, there are much better diy amps than the crescendo's.
With the Crescendo ME, I had first also a few problems wih oscillation, but these were solved by making better PCBs.
But I wouldn't know why many other amps couldn't drive these woofers, there are much better diy amps than the crescendo's.
Attachments
Hi all.
I have had zero to do with on chip power amps but here's a possible theory (we physicists are good at theories) - Chip amps are marketed on power output and so this is the primary goal, reactive load driving ability which would cause considerably higher package and output stage dissipation, is not! So the output stages probably have some restrictive SOA protection included which is why they don't drive reactive loads so well.
Just a theory.
Greg
I have had zero to do with on chip power amps but here's a possible theory (we physicists are good at theories) - Chip amps are marketed on power output and so this is the primary goal, reactive load driving ability which would cause considerably higher package and output stage dissipation, is not! So the output stages probably have some restrictive SOA protection included which is why they don't drive reactive loads so well.
Just a theory.
Greg
the original crescendo schema:
http://www.audiofanatic.it/Schemi/Tipo/Stato_solido/finali/pic_finaliSS/70W_MOS_2SK135_2SJ50.jpg
http://www.audiofanatic.it/Schemi/Tipo/Stato_solido/finali/pic_finaliSS/70W_MOS_2SK135_2SJ50.jpg
hi
the person who started this thread had intended to have very expensive speakers made from us like the - triple stacked 220 mm magnet drivers he mentioned above
to be able to customise use - we had enquired on the amp power & type , and the customer was interested to power these with a LM series chip amps
we advised otherwise and crecendo may have come up during the conversation
I would appreciate if some of you could recommend a chip amp which delevers :-
500 w rms - pure sine wave 20 hz to 20 khz , with a peak current > than 150 amps - required to drive such heavy drivers as 4 X stacked 220 mm that is 8 inch magnets and each stack of magnet 25 mm ie 1 inch deep
the low frequency driver will be a 6 layer - underhung design
if ther are no chip amps - then other suitable diy amps
thanks
suranjan
the person who started this thread had intended to have very expensive speakers made from us like the - triple stacked 220 mm magnet drivers he mentioned above
to be able to customise use - we had enquired on the amp power & type , and the customer was interested to power these with a LM series chip amps
we advised otherwise and crecendo may have come up during the conversation
I would appreciate if some of you could recommend a chip amp which delevers :-
500 w rms - pure sine wave 20 hz to 20 khz , with a peak current > than 150 amps - required to drive such heavy drivers as 4 X stacked 220 mm that is 8 inch magnets and each stack of magnet 25 mm ie 1 inch deep
the low frequency driver will be a 6 layer - underhung design
if ther are no chip amps - then other suitable diy amps
thanks
suranjan
Excuse me, could you tell us the Rdc value for that driver?
Could you also tell us the value of Fs, Vas and Qes parameters?
Note that an instantaneous current of 150A flowing through the standard 6 ohm Rdc voice coil of an 8 ohm driver would produce a voltage drop of 900V and 135 kilowatts of instantaneous dissipation in the magnet wire. In other words: 900 volts would have to be applied to a 6 ohm Rdc voice coil in order to cause 150A to flow.
Note also that the magnitude of the reactive back-EMF seen by the voice coil is always smaller than the magnitude of the active EMF applied first by the amplifier.
Could you also tell us the value of Fs, Vas and Qes parameters?
Note that an instantaneous current of 150A flowing through the standard 6 ohm Rdc voice coil of an 8 ohm driver would produce a voltage drop of 900V and 135 kilowatts of instantaneous dissipation in the magnet wire. In other words: 900 volts would have to be applied to a 6 ohm Rdc voice coil in order to cause 150A to flow.
Note also that the magnitude of the reactive back-EMF seen by the voice coil is always smaller than the magnitude of the active EMF applied first by the amplifier.
Hi Suranjan,
I think you need to recheck those figures as Eva indicates they are rather 'wild' .
I'd be happy to help (for a fee) but feel I'm probably close enough here in Australia when you come to audition.
Cheers,
Greg
I think you need to recheck those figures as Eva indicates they are rather 'wild' .
I'd be happy to help (for a fee) but feel I'm probably close enough here in Australia when you come to audition.
Cheers,
Greg
hi ,
no probs with ure cals - what would you say to a pro audio crest amp delivering 1200 w rms sine at 8 ohms with much more than 150 amps peak current delivering capacity - driving two jbl 18 s or ev 18 inch drivers , quite common place
if these setups have been performing trouble free for some time now
my one 18 inch driver handles an entire such load without any problem of compression or over heating ,
suranjan
transducer design engineer
no probs with ure cals - what would you say to a pro audio crest amp delivering 1200 w rms sine at 8 ohms with much more than 150 amps peak current delivering capacity - driving two jbl 18 s or ev 18 inch drivers , quite common place
if these setups have been performing trouble free for some time now
my one 18 inch driver handles an entire such load without any problem of compression or over heating ,
suranjan
transducer design engineer
8 ohm 18" bass drivers usually show 5 ohm Rdc on their voice coils.
On the other hand, 1200w sine into 8 ohms are achieved with 139 volts peak, so peak current will hardly go above 25 A per driver.
Stop snake-oil science, use a small current sense resistor and an oscilloscope to see current waveforms.
On the other hand, I have driven horn-loaded 15" 4 ohm drivers with chip-amps. TDA7294 (hybrid bipolar/MOSFET IC) appears to be reliable driving 4 ohms with +-40V rails when adequate cooling is provided, even though that implies an highly reactive load, 10A peak currents and more than 150W sine output.
I have used that cheap setup for small open-field parties with 25 or 35 people, and it was quite easy to produce more SPL than required even with a single 3-way all-horn chip-amp tri-amplified channel. Note that proper horn loading produces about 10dB efficiency improvement, so the same SPL is accomplished with ten times less power in comparison with direct radiators.
On the other hand, 1200w sine into 8 ohms are achieved with 139 volts peak, so peak current will hardly go above 25 A per driver.
Stop snake-oil science, use a small current sense resistor and an oscilloscope to see current waveforms.
On the other hand, I have driven horn-loaded 15" 4 ohm drivers with chip-amps. TDA7294 (hybrid bipolar/MOSFET IC) appears to be reliable driving 4 ohms with +-40V rails when adequate cooling is provided, even though that implies an highly reactive load, 10A peak currents and more than 150W sine output.
I have used that cheap setup for small open-field parties with 25 or 35 people, and it was quite easy to produce more SPL than required even with a single 3-way all-horn chip-amp tri-amplified channel. Note that proper horn loading produces about 10dB efficiency improvement, so the same SPL is accomplished with ten times less power in comparison with direct radiators.
hi
please measure a pro audio amp the references i am giving and check out their peak current output , not just the cacl of watts to rms volt and the regular amps the amplifier may supply , we have done our measurements with mr. HMMS Deen who was the technical director to elektor india ( south asia ) in a very elaborate lab set up quite a few year s ago with pro audio amps and the crecendo for that matter and the elektor mosfet 500 w ( bridge able to 1000 w ) this gave a peak current of 128 amps in the speaker lines
only then did we acquire comparable pro audio amps at that time , mostly all the crest we tested speacially their class h topology amps were measuring at abiut the figures i am mentioning
there is much more to this , anologously all i can point out to -
HCC ampilifiers in high end use -
A normal QSC or Peavey amp rated at 1000 watt does not devolop the same SPL as that of some of their own more expensive amps like the QSC Power Lite or their competitors
It is all to do with the peak amp current capabilty at the out - put
take care
suranjan
please measure a pro audio amp the references i am giving and check out their peak current output , not just the cacl of watts to rms volt and the regular amps the amplifier may supply , we have done our measurements with mr. HMMS Deen who was the technical director to elektor india ( south asia ) in a very elaborate lab set up quite a few year s ago with pro audio amps and the crecendo for that matter and the elektor mosfet 500 w ( bridge able to 1000 w ) this gave a peak current of 128 amps in the speaker lines
only then did we acquire comparable pro audio amps at that time , mostly all the crest we tested speacially their class h topology amps were measuring at abiut the figures i am mentioning
there is much more to this , anologously all i can point out to -
HCC ampilifiers in high end use -
A normal QSC or Peavey amp rated at 1000 watt does not devolop the same SPL as that of some of their own more expensive amps like the QSC Power Lite or their competitors
It is all to do with the peak amp current capabilty at the out - put
take care
suranjan
hi
by the way non of the peak current calcs i am refering to are - the simple dummy load calcs , but current real time speaker output ,
it may be a bit expensive for diy to carry out this test , mods here advise manufacturers like us to keep our stuff simple , but i think i can let some of my experience
suranjan
by the way non of the peak current calcs i am refering to are - the simple dummy load calcs , but current real time speaker output ,
it may be a bit expensive for diy to carry out this test , mods here advise manufacturers like us to keep our stuff simple , but i think i can let some of my experience
suranjan
Please, could you stop your snake-oil science?
Peak currents flowing through a single speaker (ie: no passive crossover), with music signal applied, are always substantially smaller than the values predicted for a full swing sine signal and a resistor dummy load.
For example: With +-40V *regulated* rails, a horn loaded 15" driver measuring 3.3ohm Rdc, and using music signal (low-pass filtered at 250Hz), it's actually quite hard to get more than 8A peak, even when allowing for some clipping, and despite the fact that the peak voltage across the voice coil was 38V.
And I can tell because I've done that experiment (and obviously, the test amplifier didn't have any current limiting protection).
Note that low frequency drivers only show low impedance in a small frequency range, usually 100 to 300Hz. Below 100Hz driver/box resonance(s) cause impedance peak(s) of dozens of ohms, and above 200Hz impedance also suffers a progressive increase due to voice coil inductance.
Allways trust your experiments more than the ones done by who knows who, who knows when and who knows where.
Damn outrageous current myths!!
I have ever measured the total mains peak-current consumption of an entire PA set consisting on four QSC EX1600 and four QSC EX4000 amplifiers, driving a total of *sixteen* turbosound TMS-4 cabinets, these ones (2" tweeter, 10" midrange, 18" bass) :
Mains voltage was around 215V rms, 290V peak, measurement method was a current transformer placed on main fusebox. I used an oscilloscope in order to precisely monitor both mains current and voltage waveforms. Peaks in current waveform never exceeded 30A during bass transients, even when everything was clipping. Average mains current consumption was fluctuating between 4 and 7 A.
It was a live performance and a band was playing.
Peak currents flowing through a single speaker (ie: no passive crossover), with music signal applied, are always substantially smaller than the values predicted for a full swing sine signal and a resistor dummy load.
For example: With +-40V *regulated* rails, a horn loaded 15" driver measuring 3.3ohm Rdc, and using music signal (low-pass filtered at 250Hz), it's actually quite hard to get more than 8A peak, even when allowing for some clipping, and despite the fact that the peak voltage across the voice coil was 38V.
And I can tell because I've done that experiment (and obviously, the test amplifier didn't have any current limiting protection).
Note that low frequency drivers only show low impedance in a small frequency range, usually 100 to 300Hz. Below 100Hz driver/box resonance(s) cause impedance peak(s) of dozens of ohms, and above 200Hz impedance also suffers a progressive increase due to voice coil inductance.
Allways trust your experiments more than the ones done by who knows who, who knows when and who knows where.
Damn outrageous current myths!!
I have ever measured the total mains peak-current consumption of an entire PA set consisting on four QSC EX1600 and four QSC EX4000 amplifiers, driving a total of *sixteen* turbosound TMS-4 cabinets, these ones (2" tweeter, 10" midrange, 18" bass) :
Mains voltage was around 215V rms, 290V peak, measurement method was a current transformer placed on main fusebox. I used an oscilloscope in order to precisely monitor both mains current and voltage waveforms. Peaks in current waveform never exceeded 30A during bass transients, even when everything was clipping. Average mains current consumption was fluctuating between 4 and 7 A.
It was a live performance and a band was playing.
hi
...
i would like to know :- the type of the bass drivers used and the type of cabs they were loaded in ,
did you have a digital peak hold capacity in all your instruments
but you said you minitored the ac voltage and current wave form - i would like to know how this would be really importatnt was your set up running on generators - then i guess one should need to check what thay are feeding ,
220 v X 7 amps per amplifier would be driving to the limit - the amps were driven well
at that time how was one the current monitored on voice coil
another important thing we both need to look at is that , in my mind in am from the beginning have a picture of 1 driver with a 4 inch voice coil
my experiments were carried out on 2 jbl 2242 s or 2 evx 180 b in a isobaric push pull box ( 1 box ) and on my 1 - 18 inch dual gap dual voice coil - this voice coil was in a differential set up that is 1 per magnetic gap
these are the drivers which pulled the amount of peak current which i am refered to - 3 & 2 inch vice coils did not pull much current at all - neither did horn loaded cabs or w bass bins , or scoops - front firing did , dual chamber both chamber ported band pass did - and the most was from these push pull designs like the peavey DTH
and why i needed my customer to have an amp with such a capapcity was only as he was requesting a similar driver mentioned above - though for - sub woofer use in a big ht set up
suranjan
...
i would like to know :- the type of the bass drivers used and the type of cabs they were loaded in ,
did you have a digital peak hold capacity in all your instruments
but you said you minitored the ac voltage and current wave form - i would like to know how this would be really importatnt was your set up running on generators - then i guess one should need to check what thay are feeding ,
220 v X 7 amps per amplifier would be driving to the limit - the amps were driven well
at that time how was one the current monitored on voice coil
another important thing we both need to look at is that , in my mind in am from the beginning have a picture of 1 driver with a 4 inch voice coil
my experiments were carried out on 2 jbl 2242 s or 2 evx 180 b in a isobaric push pull box ( 1 box ) and on my 1 - 18 inch dual gap dual voice coil - this voice coil was in a differential set up that is 1 per magnetic gap
these are the drivers which pulled the amount of peak current which i am refered to - 3 & 2 inch vice coils did not pull much current at all - neither did horn loaded cabs or w bass bins , or scoops - front firing did , dual chamber both chamber ported band pass did - and the most was from these push pull designs like the peavey DTH
and why i needed my customer to have an amp with such a capapcity was only as he was requesting a similar driver mentioned above - though for - sub woofer use in a big ht set up
suranjan
I have broken my usual policy of not editing other members' posts. This was to remove some racial/ethnic references in Eva's post and the response from Hunter.Racism and stereotyping are ugly and do not belong here.
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