[bwana]

Source:    Pc using foobar2000
Dac:         Schitt Yggy
Preamp:   Schitt freya
Amps:      Sanders monoblocks
Speakers: Maggie 3.7i
Music:      LOUD

When I turn the preamp volume past halfway the volume increase becomes progressively less. Sound is about 90 db on a radio shack meter. Past 2 o'clock the tweeters start to fail. And eventually the 2.5 amp tweeter fuses blow.

I guess those sanders amps really deliver the juice but wtf?! Anybody else get this?

[Elizabeth]

Usually the failure of tweeter fuses is due to not enough power.. Not too much power.
When an amplifier starts to 'clip' the output is heavy on high frequency artifacts.. and thus the tweeters are overloaded.

If the amp was not overstressed.. the tweeters would not go South.
So #1 is amplifier(s) with MORE POWER. MINIMUM twice, better three times the output, and the best would be four times your curent power output. is what I would recommend.
Too much amp is never a problem (except in the wallet). Too little is a problem.

Other possibilities are the digital sections are producing tons of spurious HF artifacts and killing the tweeters.
This is less likely, but could be another reason.
And finally the output of the preamp at higher volumes is over loading the amplifier input stage.. and causing distortion artifacts to overload the tweets. This is another reason to buy a different amp.

Added: After thinking about this.. I would place the most likely blame on the preamp overloading the amp input. The main reason for this is the op mentioning "the volume control does progressively less"..
So the preamp output is already overloading the amplifier at 1/2 rotation of the volume control.
I would say this a a fault of the AMPLIFIER, not so much the preamp. Perhaps a bad pairing of preamp and amp. Anyway, one of them would have to be changed.. and I would tend to place the blame on the amplifier.
Now perhaps something is broken in the input of the amp? I suggest finding a more compatible amp. One which is not going be overloaded by a signal from a preamp.
This may be wrong though, as if the preamp has a internal problem which is overloading some stage in the preamp... Anyway, yeah you have a problem, and it is not the speakers.
One way or another, something in the chain is overloading the electronics at some point.
Best bet is if you can try some other preamp or amp.. if you can borrow one.

More... I wonder if the op has tried to 'boost' the output? If he say took the XLR output of the preamp, and jury rigged a IC from XLR to RCA, to the amp RCA input. That would certainly be overloading a normally 'good' input stage easily. The XLR output is 6dB stronger than a RCA output.
SO I wonder if the op has done this? IT would explain the problem. Solution is don't ever do this.
Another test is to place resistors  between the pre and amp. to reduce the max and stop the overload of the input stage of the amp. If a resistor solves the problem. IE no more blown fuses and the volume above 12 o'clock does more.. Then the problem is known. Too much voltage from the preamp is overloading the input stage of the amp.

Used to be the 'standard' was 0.5 volts prior to CD. After CD the standard really was moved to 2 volts (which is the 'pro' standard, the consumer was 0,.5 volts like in most FM tuners, and phono stages) So an old amplifier designed for the previous 0.5 volt standard could easily be overloaded with a 2 volt input. Just a thought.

[*Scotty*]

My two cents,for what its worth, is that you are probably clipping the amps. The Maggie 3.7i, or any maggie, will only play just so loud. After a certain point they quit getting louder because you have reached the limit of the diaphragms excursion. At this point more power goes in and not much happens but blown fuses or burned panels in extreme cases.
 The RatShack meter really can't see peak SPLs as it is made to measure average sound pressure levels and not peak levels. The peak happens and the meter goes HUH. Your peaks could be well above 90dB perhaps as high as 110dB peak SPL, no real way to tell for sure.
 I suspect that even with a pair of Magtech Monoblock Amplifiers with 2000 watts/ch 4 ohms you would still pop fuses, it just might happen a 2:30 on the dial instead of 2 o'clock and it still would not sound any louder.
Scotty

[Davey]

How does an amplifier specified with voltage gain of 26db (x20) and 2 volts required for full output achieve a 1600wpc/8ohm power rating???

The 26db gain and 2 volts tell me this amplifier clips at 40VRMS.  That's a 200wpc/8ohm rating, yes???



Dave.

[bwana]

The sanders amps are driven to maximum output with 2v. I measured the freya putting out 5v at max on its rca outputs (which I am using). I could not find the actual spec. I like to use the tube out put as opposed to the jfet buffer on the freya.

Anyway, it seems I am 'overdriving' the magtech. So if the music gives a sinusoids peak, I wonder if the amps just clip all the volts above 2v. This would give a square wave output and conceivably damage a 'regular' cone speaker - right? After all when an amp clips because it can't put out more juice, is it not the squareness of the waveform that causes the speaker magnet to shear off the cone?

But this is a planar magnetic film with super fast response. It can't really die like a regular speaker.?

[*Scotty*]

It would be useful to know the voltage output of the preamp when the volume is at 2 o'clock. A 1kHz sinewave test tone recorded at -20 dB and fed into the preamp with the volume set a 2 o'clock might get us useful info.
 Information on the magtech's clipping behavior would be helpful. Does 2.1volts or 2.2volts in result in hard clipping or does it take 2.5 volts
to induce clipping.
 My amp, for example, will clip when fed more than 1v., which is the voltage required for full power out. It is rated for 108w/8 ohms it will be into clippping at 112 watts out.
 What is the full rated power of your amps into a 4 ohm load?
Scotty

[Armaegis]

After all when an amp clips because it can't put out more juice, is it not the squareness of the waveform that causes the speaker magnet to shear off the cone?

It's a couple of factors... clipping causes "square" waves which actually creates all sorts very high frequency content which then get magnified. This can force the speaker cone/film to move much faster than it can handle. This can cause your amp to oscillate. This can cause your amp to overheat and behave erratically. This can cause your speakers to burn out (that electrical energy is no longer going to mechanical motion and instead holds and dissipates as heat). All of these are bad mojo and can let out the magic smoke.

[mick wolfe]

Did you try the Freya in its passive mode? Take the tube gain stage out of the equation for starters. Seems like the Sanders amps would have WAY more than enough power without clipping. Especially if they're the ones rated at 2000 watts into 4 ohms. Seems like you'd melt the speakers before clipping would set in.

[SteveFord]

FWIW, I can play my 3.7s  loud enough to drive me out of the room and never pop a fuse or a ribbon.
 

[bwana]

My two cents,for what its worth, is that you are probably clipping the amps. The Maggie 3.7i, or any maggie, will only play just so loud. After a certain point they quit getting louder because you have reached the limit of the diaphragms excursion. At this point more power goes in and not much happens but blown fuses or burned panels in extreme cases.
 

This is what roger sanders said too( designer of the amps). His solution: don't play the music too loud.

@Steveford
How loud do your Maggie's get on a decibel meter? (There are apps for a smartphone that can measure this)

I also spoke w a hifi dealer near me. He said he's heard that the fuses start to blow when  tweeters start dying. Something about the membrane causing short circuits.

[G Georgopoulos]

It's a couple of factors... clipping causes "square" waves which actually creates all sorts very high frequency content which then get magnified. This can force the speaker cone/film to move much faster than it can handle. This can cause your amp to oscillate. This can cause your amp to overheat and behave erratically. This can cause your speakers to burn out (that electrical energy is no longer going to mechanical motion and instead holds and dissipates as heat). All of these are bad mojo and can let out the magic smoke.

you're right (damaged tweeter), that's what i reckon too..

[*Scotty*]

I also spoke w a hifi dealer near me. He said he's heard that the fuses start to blow when tweeters start dying. Something about the membrane causing short circuits.

 Highly unlikely. When things burn in half you have open circuits not partial shorts in the membrane.
You can damage the tweeter if you hurriedly replace blown tweeter fuses and successively build up heat in the tweeter foil to the point that it is damaged and fails. If the fuse is bypassed eventually the tweeter will also behave as a fuse element and burn in half.   
Scotty

[Letitroll98]

Do you have ESL or Magtech Sanders amps?

[bwana]

Magtech

[poseidonsvoice]

How does an amplifier specified with voltage gain of 26db (x20) and 2 volts required for full output achieve a 1600wpc/8ohm power rating???

The 26db gain and 2 volts tell me this amplifier clips at 40VRMS.  That's a 200wpc/8ohm rating, yes???



Dave.

http://sanderssoundsystems.com/products/amplifiers/magtech-monoblock-amp

If the above link is the amplifier that the OP is using then I agree with Davey. There is a spec here that doesn't make sense. I really wonder what the rail voltage is on this amp.

Best,
Anand.

[Davey]

http://sanderssoundsystems.com/products/amplifiers/magtech-monoblock-amp

If the above link is the amplifier that the OP is using then I agree with Davey. There is a spec here that doesn't make sense. I really wonder what the rail voltage is on this amp.

It seems pretty clear the Sanders 1600/8 and 2000/4 specifications are complete nonsense.  Bandwidth to 100khz doesn't help either....assuming that specification is not nonsense too.

bwana is most likely driving his amplifier to clipping in the middle/bass portion of the frequency range and the effects of that clipping are being felt by the tweeters and tweeter fuses.

Until this situation is fully sorted and understood, the volume needs to be turned DOWN. 

Dave.

[bwana]

thank you for your replies. Yes, that's the amp I am using x2. The sound is lovely. The image is detailed and I can even pick out the instruments on the invisible stage in front of me. The maggies are 1/3 into the room against the side walls w toe in. I guess I need to get different speakers if I want loud, right?  Anyway, I put a piece of tape on the preamp to remind me not to exceed the threshold.

I also thought that a crossover might help by routing the low freqs to a sub and that way spare the maggies some of the heavy lifting. Unfortunately, I already purchased a great dac. All the crossovers  work in the digital domain which means they have a/D circuitry, then the software, then D/a circuitry. Kind of a waste of a great DAC. Of course, I could get a lynx card for the pc and do the crossover in the pc but then I'll 'only' have 24/96 output from the coax digital outs of the card. Currently using USB out and it works really well. No noise whatsoever. Of course, I've gone to the trouble of getting a separate USB card and feeding it power from a separate external linear power supply so its isolated from the noisy pc ps.

[G Georgopoulos]

  Anyway, I put a piece of tape on the preamp to remind me not to exceed the threshold.

A damaged tweeter won't sound good even at low levels,it's faulty,and could get worse (blow your amp fuses)
,my advice is change it with a new one.

[Davey]

Another factor here is the (rumored) series crossover utilized in the 3.7i.  This creates a "contamination" between the drivers that doesn't exist with a standard, parallel crossover.
It's difficult to know if this is the smoking gun causing the failure.....but it's certainly not helping.

Yet another pitfall that series crossovers bring to the table. 

Dave.

[Paul McNeil]

If you turn the volume up high enough to blow the tweeter fuse, and you have sufficient power from your amp (no clipping), then perhaps you need a subwoofer or two. With this, in my opinion, necessary addition, you would not go so high, the accurate bass you would get from the subs would blow you out of the room at this level, as I know from my 1.7s. And, with subwoofer supplementation you would never complain about excessive treble, and insert resistors, etc. You'd be too wrapped up in the music.