View Full Version : fused speakers

09-04-2003, 11:18 AM
A recent discussion of damping talked of wire gauges and lengths but no mention was given to fuses. Crown amplifier manuals of the 70's recomended that inline fuses be used to protect the speakers and the amplifiers.

Does anyone use fusing? How does that effect damping?


09-04-2003, 11:37 AM
Fuses are for people who can't afford recone kits :rotfl:

Real men and women let their loudspeakers suck it up or die trying :D

09-04-2003, 11:49 AM
OMG I crack myself up! :p :p :p

Of course posting crap like that is a sure way to cause my strapped Citation 22's to suddenly go medieval, blow all their output transistors and take my 4430's with them... I'll keep you all posted...

Alex Lancaster
09-04-2003, 12:26 PM
Fuses are for DJ's who do not really know what they are doing, or like brakes in cars, real men use the horn!

Yeah right.


09-04-2003, 02:05 PM
OooOOoooo... Citation 22s! (drool)... :bouncy:

G, do you have the Citation 21 to go with them? I remember REALLY liking that pre, both with the Citation 22 and with big iron like Urei 6290 amps.

We once had a store demo system set up, with the Technics SL-P1200 pro CD player, running into the Citation 21, thru the 6290, into 250Ti's. Talk about UNLIMITED dynamic range!!
:rockon1: :rockon2: :band: :dancin:


09-04-2003, 02:09 PM

Yes, fuses DO act as resistors, and I HAVE heard the effect of a fuse, with regards to the damping of the bass of a speaker system. If the system is relying heavily on electrical damping, it can make the difference between tight and slightly boomy bass.

Fuses are also funny animals... sometimes they'll get "wounded", but won't completely blow. I've measured impedences in the 1 ohm and higher range... whoops, there goes ALL your damping!

If you use a fuse, be sure to check in on it after any hard use...


09-07-2003, 12:11 AM
If fuses that are not designed specifically for current limiting function posessed significant internal resistance, they would "nusiance blow" constantly, due to the heat generated in the "R" component of "I squared R".
Think about it.
Also, is your use of fuses with loudspeaker loads intended to protect against:
1). Anamolous DC components, etc., in amp outputs,
2). Excess real (musical) signal currents,
3). Both?
Let's be realistic, and say BOTH.
Small glass fuses (3AG etc.) types can and will generate rapid heat buildup and therefore rapid and possibly premature opening. Dismiss glass fuses altogether for speaker protection.
Type FRN (250 volt max., dual-element, time-delay) types are what you want. In these, two elements (fusible links) are connected in series. One element is designed to open very quickly in the event of a short-circuit "downstream" from the fuse. This would roughly correspond to the DC anomalies scenario. Conceivably.
The second element allows a power-over-time response (time-delay).
I seem to recall that Acoustic Research's (ca. early 1970's) recommendation for protectve fuses on the AR-5 (10" woofer, acoustic-suspension, three-way) was the FRN- 7/10 (amp) fuse, and the FRN- 1 1/4 amp type for AR-3A's. Both to be used in open fuseholders (spring clip on each end). (Effective heat dissipation, under high loads).
As far as resistance, and back to the crux (effect on amp/speaker damping) of the original question, let me offer a quick, real-world check, for reference.
I have in my hand an FRN-10 type fuse. With my Fluke model 79 series II DVM, set to "low ohms" (40 ohms max scale, 0.01 ohm resolution), I measure exactly...
0.05 ohms across it. I had to subtract out the inherent 0.07 ohms of the slinky, "low resistance" Fluke (read also $$) test leads to get that reading (Rtotal = 0.12 ohms, minus 0.07 ohms= 0.05 ohms).
Assuming clean, tight spring clips, wire terminations, and fuse surfaces, that's a resistance in the fuse of...0.05 ohms, or five one-hundredths of one ohm.
How much effect on damping would you assume this will impart?
BTW, I did blow a few of those FRN's on the AR-5's and AR-3A's, on quite loud levels with a very powerful amplifier. Those loudspeakers were inefficient power hogs with IMHO cheesy drivers. If you drove, for example, a new (fresh alnico flux strengths) 4311 or L-100 (with their more efficient and more robust drivers) hard enough, on clean unclipped musical material, hard enough to blow those 7/10 amp fuses..that would be a very high spl generated.
There is a nifty speaker protection scheme on Drew Daniel's website (http://www.drewdaniels.com) also, which you should check out. It's in the "tech topics" area.