I said in my first post it's about the toughest thing you can ask a speaker to do, there's no disagreement that guitar amps can produce speaker punishing signals. My opinion is that even a speaker that's not officially an "instrument" speaker should be able to handle these signals at a low power.
Well it's best isn't much. The amp isn't a mysterious black box capable of unknown power during transients. A 5W amp can't produce a transient or square wave that's more than 10w. Say this amp can produce a 5W sine wave into 8ohms before clipping. It's clipping because it can't produce a voltage any higher than the peak value of this sine wave. This is a 6.33Vrms sine so it has a 8.9V peak. If you keep turning it up you'll eventually get a square wave with the same peak voltage and 8.9v into 8 ohms is 10 watts. No matter what signal you put into the front of this amp it can't produce more than 10w out. You can slam the preamp with the biggest transient you can imagine, still 10w out.
Is a 10w square wave enough to kill a 300w speaker? I doubt it, but better than that I've got a pair of woofers I'm going to throw out. You pick the signal and I'll kill one with a sine and the other with your signal and record how much power it took.
I agree that's very much more likely, that's why I posted. To answer the question of why did the speaker blow, it blew because he drove it too hard. It's true his speakers aren't specially designed for guitar, but look at these are very popular guitar speakers:
https://weberspeakerscom.secure.powweb.com/weber/12a125a.htm
http://professional.celestion.com/guitar/products/heritage/detail.asp?ID=6
https://weberspeakerscom.secure.powweb.com/weber/csig12.htm
http://www.jensenvintage.com/p12rlg.html
Standard round copper wire voice coils, sometimes even on paper formers, and not a cooling fin or vented pole piece in sight. Yet these are the style of speakers guitarists have been playing through for more than 40 years. They do have tight surrounds so maybe over-excursion is not a worry, but a square wave will heat those voice coils just as much as any other speaker. As I said before they simply used enough speaker to handle the amp, like the marshall 50W amp and it's 120W cabinet. There are high power guitar speakers now and some players do use them, but the vintage style is the most popular.
I'm sure we all agree it would be best if he spent a few hundred dollars on a cabinet full of guitar speakers, but since that's not realistic can't we tell him how to safely match an amp and speakers for guitar use? If you want to use little speakers like that you need to use a very tiny amp and it's not going to be very loud. If you want to use your big amp, you need way more speaker.
luckily guitar amps aren't dc coupled and roll off the bass quite a bit to produce a sound more in the range of an electric saw than a tuba. I can see how plugging a guitar into a phono input would be a very bad idea, but once again, he's using a line level synth that tries to recreate the sound of a recorded guitar amp. No 10hz signals are getting through that thing.
For what it's worth, when I tried out the amp modeller in the store they plugged it into active studio monitors for me, as if this was a recommended setup. It was this that got me thinking that plugging it through a hifi amp would be acceptable. The B&Ws were paired with a £200 Marantz transistor amp that used to drive them fine for CD and vinyl playback. I never turned the amp volume up more than a third, so it's not as if the speakers were being driven hard. I did, though, try out every sound on the modeller -- which is pretty much every guitar sound that exists.
I tried this. With the dead speaker, I got some crackling and white noise but the earth didn't exactly move. I tried the same with the working speaker, and got the same result but this time with bass presence. The broken speaker sounded very tinny in comparison.
So, what am I looking at here? Are the tweeters still OK, and can a worthwhile attempt be made at reviving the speakers? Or are the woofers the most expensive component, meaning that revival isn't really viable?
I tried this. With the dead speaker, I got some crackling and white noise but the earth didn't exactly move. I tried the same with the working speaker, and got the same result but this time with bass presence. The broken speaker sounded very tinny in comparison.
So, what am I looking at here? Are the tweeters still OK, and can a worthwhile attempt be made at reviving the speakers? Or are the woofers the most expensive component, meaning that revival isn't really viable?
I found this chart from a quick search on Google, might be helpful.
http://www.contrabass.com/pages/frequency.html
This chart shows why bass guitar cabinets need to be well designed.
And one other thing that makes the woofers 'bounce' is when you press the string down so far it touches one of the magnets. And to any musicians out there, fascinating experiment - get a set of earphones with muic playing through them, and with your electric/bass plugged in and turned on, move them near the pickups. THe music will play through them. I found it interesting at least.
http://www.contrabass.com/pages/frequency.html
This chart shows why bass guitar cabinets need to be well designed.
And one other thing that makes the woofers 'bounce' is when you press the string down so far it touches one of the magnets. And to any musicians out there, fascinating experiment - get a set of earphones with muic playing through them, and with your electric/bass plugged in and turned on, move them near the pickups. THe music will play through them. I found it interesting at least.
mga said:
Revival in a fashion, cheap, working, but not the same :
The other alternative is probably two of these :
http://www.wle-shop.co.uk/modules/shop/view.asp?catid=79&Prodcode=902.423
Though getting them to fit may be a problem, or not.
And of course they are not likely to sound correct but
they will be working in a fashion.
also see :
http://www.skytronic.co.uk/product/product.php?s=902.195
http://www.skytronic.co.uk/product/product.php?s=902.420
Local supplier :
http://www.skytronic.co.uk/about/storefinder.php
/sreten.
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