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Fuses for later Acoustic Research (verticals,post classic)


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Does anyone have a list of what kind of slow blow fuses the later AR speakers needed to use? I remember the old AR 3A series fuses, but after that I have no information.

I have a pair of AR 8Bs and would like fusing information on what to use for them.

Hi Allen

I am not familiar with your particular model AR speaker.

A fuse is the best dollar you can spend in a stereo system, accidents do happen and they can be expensive or in a lot of cases original replacement

drivers are not available and certainly not for under a dollar.

If there is a powerhandling figure listed somewhere similar to any of the classic speaker ratings of the 4 posted AR fusing sheets, I would lean that

way, plus go to a slightly lower value.

Carl is correct in using a fast blow fuse which are more readlily available and only about $.25 each, as opposed to the now very expensive and hard

to find, at an attractive price, FNM/FLM slow blow type.

Be sure to use an open style fuseholder to help allow the glass fuses to keep cooler at least.

After much thought I feel now that the fuseholders should be at the amplifier rather than at the speaker end.

My reasoning is because if there is a short, pinched under furniture, etc, the fuse at the speaker will not protect the amplifier.

Fast or slow at an appropriate rating will most often help protect from the usual transients that cause the speakers to burn out.

Of the many times I've read about fusing speakers, only AC wall outlets electricity will not be stopped in time.

High temperature speaker voice coils burn from too much DC which is usually when the amp has run out of steam and is sending DC to them.

The damage is cumulative so that if someone hears their speakers distorting from over driving, the damage is now irreversible.

20120304 5:45 PM UPDATE

As a point of interest, Heathkit used a 3 amp fast blow glass fuse in an enclosed chassis type fuseholder for their model AS-103 - 103A speaker kit.

This model speaker was using the Acoustic Research AR-3A driver components and crossover circuit.

Heathkit provided the enclosure and some parts that also allowed bi-wiring with banana plugs.

Heathkit also mentioned in their assembly manual that you can bi-wire or bi-amp them, one or both I believe.

I do not remember AR ever suggesting that with the AR-3 or the AR-3A.

Heathkit only mentioned this wiring feature, no schematic or pictures was provided.

We have no feedback here from Heathkit as to whether there was many or any AR speakers damaged using the 3 amp fuse.

Perhaps it was AR that suggested that fast blow size and type of fuse rather than the slow blow fuses printed on 4 sheets posted here plus perhaps

with individual speaker owners sheets.

AR was suggesting for use with the AR-3A using Buss FNM 1 1/4 amp slow blow fuses in an open style fuseholder.

Fusetron also makes the FLM 1 1/4 amp slow blow fuse, which is the equal fuse.

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I want to thank everyone for their replies. I have yet to find fusing information except on the original AR speakers from the ancient 1960s series. AR did recommend slow blow, not fast blow fuses for the speakers in those days.

Hi again

If you or anyone else has the operating power rating for these speakers, a suitable fast blow fuse can be calculated from that data.

Barring no one comes forth with that data, i would suggest that you look at the very conservative AR-4/4X speaker rating.

This particular model used a Buss 6/10 amp slow blow FNM fuse in an open fuseholder.

Littlefuse FLM 6/10 fuses will also do.

If these are not available, very difficult to find at an attractive price, then go with a 1 amp fast blow glass fuse in an open style fuseholder.

Always have a few spares onhand.

Because, as I explained earlier, I do not know your particular speaker, I do not know what complementary drivers they use.

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  • 3 weeks later...

I have a suggestion for all of you. Instead of fuses go with magnetic breakers. They protect better then any fuse, and have the advantage of tripping in a small fraction of a second. The one that would be just the ticket for use with speakers is one that looks and functions like a toggle switch. They are made in many, many values, trip speeds, and designs so there is one that will do the job nicely. I have used magnetic breakers for many years in my hamradio gear, and they have saved my old vacuum tube rigs so many times. go here:


Allied Electronics has 55 pages of them.

There is one thing to consider modern solid state audio amp's are lighting fast in their response times, when compared to Vacuum tube or early solid state equipment. If something is going to happen it is going happen so fast that a slow type fuse might not blow fast enough this is where a magnetic breaker is ideal.

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