Putting A Fuse In A Speaker Cab?

:?: :?: :?:

No Cab builders here with any input on this?

:?: :?: :?:

Somebody's gotta know the answer! If nothin' else, look on the back of your cab (2 x 12, 4 x 12 ,whatever you have) & tell me if there is a fuse there! :mrgreen:

Unlikely. The resistance of a fuse -- even though usually less than 1 ohm -- can cause a noticeable change in the volume and frequency response of a speaker, as amp driving impedances are very low, and the cab drivers ("speakers") themselves are usually only 4 to 8 ohms nominal. In reality "nominal" means mid-frequency spec. At some freqs, it would not be surprising for a driver to drop to 2 ohms, even if its nominal spec is 4. A lot of power could be lost in the fuse at those frequencies, leading to funky (bad) freq response. The damping factor of the amp/speaker system also will be changed if the fuse has significant resistance (even a 0.25 ohm can be significant). This will affect bass dynamics => ringing, loose or "flabby" bass.

The only speaker system drivers I've ever seen fused are magnetic tweeters. Tweeters are much more prone to burnout due to highly distorted signals creating so much harmonic power that the tweeters are overdriven to the point of burnout. No tweeters in your friends cab, correct? Then no fusing.

:?: :?: :?:

No Cab builders here with any input on this?

Jeez Kat, give us at least 24 hours on a weekend... 8)

Greg is correct (of course), fuses are not a good choice for a speaker cabinet.

Jeez Kat, give us at least 24 hours on a weekendlol

You mean you don't just sit here all day & continuously refresh the page like I do?!?! :lol:
No tweeters in your friends cab, correct? Then no fusing. I should have mentioned, it is a bass cab. No tweeters. I don't know where he got the idea that it should be fused... :?

There are a few powered bass cabs, which I assume would have fuses. The Bergantino IP series comes to mind, and the small Tech 21 Bass Engine. But those are exceptions, not the norm.

If a fused cab were hooked to a tube amp and the fuse blew while the amp was running at high output, the amp would be toast. Playing a tube amp unloaded (no speaker in the circuit) causes voltage spikes in the output transformer of 20,000+ volts. It acts like the induction coil in a car engine's spark plug circuit. The high voltage will cause arcing at the power tube sockets and may damage the sockets and tubes, as well as sparks puncturing the lacquer insulation in the transformer windings, leaving carbon tracks that will short out later. It's dangerous to play an unloaded tube amp even for an instant, as when switching from one speaker to another. Any such switching has to be done with a "make before break" arrangement. It's also a good idea to build into the amp either some form of voltage relief such as a spark gap or neon lamp, or a resistor shunting the transformer to lower its Q and reduce the induced voltage. A 5W 160 ohm resistor across an 8 ohm output jack is a good place to start. Won't draw off much power when the amp's operating normally, but can save the expensive transformer if you forget to plug in a speaker. It also works to use a shorting jack on the output that will put a dead short on the output when you unplug the cable. But the problem comes in if you have a cable plugged into the jack, but it's not plugged into anything at the other end. The shunting resistor is safer. (Could use both.)

There are a few powered bass cabs, which I assume would have fuses. The Bergantino IP series comes to mind, and the small Tech 21 Bass Engine. But those are exceptions, not the norm.

Those would be power supply fuses for the amp, not driver fusing.

Ricochet - good points. I should have thought of that, esp. about unplugging while the amp is "hot". My friend is not one to listen to advice, so he may have to learn this lesson the hard way. But, at least others on here will be able to benefit from all the good advice.

Thanks all! :)

Those would be power supply fuses for the amp, not driver fusing.

Sure, but the original post didn't distinguish.

On the same topic, when a bass cab has 200-300-etc watts spec'd for the woofers and a much lower power handling for the horn/tweeter, say 100w, it seems that the crossover is the control point, right? But aren't crossovers made with capacitors and inductors, rather than fuses?

Those would be power supply fuses for the amp, not driver fusing.

Sure, but the original post didn't distinguish.

On the same topic, when a bass cab has 200-300-etc watts spec'd for the woofers and a much lower power handling for the horn/tweeter, say 100w, it seems that the crossover is the control point, right? But aren't crossovers made with capacitors and inductors, rather than fuses?

Fuses are catastrophic protection elements. Crossover networks are intended to route various freq bands to the right drivers for best performance in normal operation.

Don't believe I've ever seen a tweeter in a bass cab or even an electric guitar cab. Only place I see them used for any good reason is in acoustic guitar (combo) amps and PA systems, as these process signals in the upper end of the audio freq range where a tweeter is actually useful. In those cases, the horn tweeter might be fused if it has a magnetic driver unit. This type tweeter also would require a crossover (yep, cap/ind/res network) to pass appropriate high freq signals to the tweeter, while keeping all that much higher power low frequency energy from reaching the tweeter coil and frying it. But when something in amp chain goes non-linear and clips -- the amount of high freq energy increases greatly right out of the amp as the harmonic content goes up. This will blow right through the tweeter highpass crossover network, and if high enough in power, fry the tweeter. So magnetic tweeters often get fused to protect against this. As tweeters are used in acoustic amps and PAs, high levels of non-linearity are not typical, and there should not be much of this unintended clipping -- unlike a high level distorto electric guitar amp (with no tweeter). Piezo horn tweeters don't usually require either a crossover or a fuse, as they "naturally" contain a highpass filtering characteric due to design and also are very tough compared to magnetic horn tweeters. But the piezos don't sound as good as magnetic tweeters either.

I have seen bass combos with tweeters. I thought it a bit odd, but there they were.

I have seen bass combos with tweeters. I thought it a bit odd, but there they were.

Are you sure they were tweeters? If they were horns, they could have been midrange drivers. Tweeters would make no sense -- except to marketeers.

Ricochet is correct, I too have seen them & wondered "why"? Acoustic makes a 50 watt combo with one in it.

http://www.musiciansfriend.com/product/Acoustic-AB50-1x10-Bass-Combo-Amplifier?sku=481621 :shock:

I have seen bass combos with tweeters. I thought it a bit odd, but there they were.

Are you sure they were tweeters? If they were horns, they could have been midrange drivers. Tweeters would make no sense -- except to marketeers.

???

Y'all need to get out more. :wink: It seems the majority of cabs have them.

And what's the difference between a 1" horn and a tweeter?

http://www.musiciansfriend.com/product/Epifani-UL210-500-Watt-2X10-Inch-Bass-Cabinet?sku=601047
http://www.musiciansfriend.com/product/Eden-D210XST-2x10-Bass-Cabinet?sku=606167
http://www.musiciansfriend.com/product/Aguilar-GS-112-Single-12-Bass-Speaker-Cabinet?sku=601030
http://www.musiciansfriend.com/product/SWR-Triad-3Way-Bass-Speaker-System?sku=602008
http://www.musiciansfriend.com/product/Ashdown-MAG-410T-4X10-Deep-Bass-Cabinet-with-Tweeter?sku=605032
http://www.musiciansfriend.com/product/Ampeg-SVT410HE-Bass-Enclosure?sku=481741 (1" horn on this one)
http://www.avatarspeakers.com/b212.htm ("The cab uses the new full 12 db mylar crossover network for both the tweeter and bass speaker sections for a more accurate response and for better power handling. There is a tweeter volume control on the back panel.")