Fusing AR-3as

[Guest OldRelayer]

I am in the process of buying a pair of AR-3a's. I obviously want to fuse them but I am a little confused. I thought I had it when I read you should use a fast blow 1 amp fuse, but then I read something about fusing the woofer separate from the mid and tweeter, which does make sense, it takes a whole lot more energy to drive the woofer. I don't have a clue how to do that, can some one explain, be gentle. I guess it must have something to do with the 3 connectors on the speaker? Is this an old version of bi-amping or bi-wiring? I do have a 4 channel amp, is there a better way of using the power other than using the amp in 2 channel mode?

Thanks

Barry

[Guest daveshel]

I'm thinking that fusing your tweeter is more useful. Most driver failure is caused by the square waves that result from overdriving your amp, and fuses won't help here. But damage to tweeters is just as likely to be caused by excessive power, and this is where a fuse will help. I've never used them, so I don't know what type to use.

Where the heck is Vern?

[dynaco_dan]

>I'm thinking that fusing your tweeter is more useful. Most

>driver failure is caused by the square waves that result from

>overdriving your amp, and fuses won't help here. But damage to

>tweeters is just as likely to be caused by excessive power,

>and this is where a fuse will help. I've never used them, so I

>don't know what type to use.

>

>Where the heck is Vern?

Hi guy's;

I heard my name mentioned.

Disregarding which brand speakers you have, back out of this topic and go to "other forum" and lookup the recent fusing topic of a month or so ago.

Print this out for reference material.

The final list, which isn't quite so truncated, should give most users an idea if, and only if, they are considering using a fast blow 1/4" x 1 1/4" fuse, in an open style fuseholder, for the entire speaker enclosure, whether 2 way, 3 way or 4 way.

Also for AR speakers only, go to the AR library, download and printout the varous fusing information sheets and keep them for a reference.

Also for Advent, go to the Advent library, download and print their fusing information as a reference.

Both AR and Advent, used Bussmann FNM slow blow fuses only, for their speakers.

I believe, Littlefuse (check their website catalog) makes an FLM series which is the equivalent.

For some reason, the Littlefuse brand, was not mentioned by, AR or Advent.

It's too late now to ask why.

They both did not suggest a fast blow fuse type or size, too bad.

Also go to the crownaudio.com website and download their very interesting look at fusing and speaker power requirements.

My interpretation is, fuse the tweeters with it's own appropriate sized fast blow fuse, same for mids and finally a slow blow for the woofers.

You can see that this would have be really neat, if the manufactures had included all of this when the speakers were made new, the research would have been done and not by us.

We cannot afford to experiment and find out what the drivers limits are, when the right one is found, it's too late.

As you might be aware, the only main speakers, that I can think of, that came with fusesholders, attached, and wired, in to the speakers early on, were the AR-LST and LST/2, with slow blow fuses and open fuseholders.

Heathkit, Heath/Ar co-developed the AS-103 (AR-3A equivalent) speaker system kit decades ago, there was a chassis mounted (not desired) fuseholder with a 3 amp fast blow fuse.

Using the AR-3A's AR recommended slow blow fuse at 1 1/4 amp and Heath's 3 amp fast blow fuse, only as a reference point, at least this was a starting point for discussions.

We of course, should be downsizing these, to a lower and safer level for our antiques, which use drivers that are difficult and expensive to find used, but not impossible.

Myself, I use a 1 amp fast blow fuse in an open style fuseholder, normally, for all of my speakers, and I buy extras and they are really cheap.

Now that I have said that, a 1 amp fast blow fuse will blow quite quickly, if you like the volume way up.

They haven't made the original OEM drivers for over 25 years, so fuses seem to be a great idea, Heh?

[Guest OldRelayer]

I still don't understand how you fuse the tweeter separate from the woofer? What is the meaning of the 3 posts on the back of the speaker, two are always bridged?

[dynaco_dan]

>I still don't understand how you fuse the tweeter separate

>from the woofer? What is the meaning of the 3 posts on the

>back of the speaker, two are always bridged?

>

>

>

>

Hi there;

If you went and at least read about those various fusing sheets and also visited crownaudion.com's website site, you should have a greater understanding about speaker fusing.

As I mentioned before, the speaker companies didn't provide us with the fuseholders, the individual fuse models or ratings, nor the easy means to easily do this.

If one wants to persue this path, some mechanical and electrical work is required.

The grill cloths would have to be very, very carefully removed.

Remove the woofer for access, locating the correct leads, running polarized leads to the rear outside of the enclosures, without compromising their seals.

Mounting open style fuseholders, labeling them correctly as to which drivers and fuse size and rating.

As you can see, it requires a few hours or so of technical work and only maybe $10 - 15.00 in parts each enclosure.

The enclosures would now have 2 - 3 open style fuseholders mounted on the rear of the enclosures surface.

Which can snag materials, or be damaged by passing or falling objects or by packing and moving them.

Good luck.

[Guest OldRelayer]

Ok, thanks, just trying to catch up.

[Guest Bret]

>As you might be aware, the only main speakers, that I can think of, that came with fusesholders, attached, and wired, in to the speakers early on, were the AR-LST and LST/2, with slow blow fuses and open fuseholders.<

Vern,

Add very early production 10pi's to your list.

Bret

[Guest linedrive]

Vern, do you have any thoughts on using a circuit breaker instead of a fuse? Have you ever seen this done with an AR3a? Thanks.

Ted

[dynaco_dan]

>

>Vern, do you have any thoughts on using a circuit breaker

>instead of a fuse? Have you ever seen this done with an AR3a?

>Thanks.

>Ted

I believe that a circuit breaker will not be anywhere near sensitive enough to even consider using for speakers.

I am referring to a standard mechanical house circuit breaker type, but at our lower amp ratings, if available, not some special solid state type, if there is such a device.

If you were to check out the specifications of a domestic house circuit breaker, you would see the loads and time periods before tripping.

The slow blow FNM fuses Advent and AR recommended are not interchangeable with 1/4" x 1 1/4" glass slow blow fuses either.

Check out the Littlefuse and Bussmann websites to see how many types of fuses there are.

For all intent and purpose, if one was to fuse, for example an AR-3A, you would need to run 3 polarized pair of wires out the rear of each enclosure, 2 pair for 1/4" x 1 1/4" glass open style fuseholders and one pair for the Bussmann #4421 open style fuseholder, or #4515 screw type to be mounted on the enclosures rear.

This is a few hours of technical and mechanical work, but it can be done.

Should you do it?

If the manufacturers had done it, we would now be on easy street.

We would even know what is the correct fast blow fuses for the tweeters and mids.

Is it worth the effort?

If you are technically proficient, yes.

If you are not, no?

Maybe you have a buddy that can help you.

We would then have a learning curve as to what size fast blow fuses are needed for the tweeters and mids.

The cost of this lesson would be a few blown drivers.

The other choices are, FNM and maybe blow tweeters, fast blow and perhaps blow more often, with deep bass passages.

Good luck with your choice and please let us know your decision.

[Guest pigs in space]

Someone mentioned early 10pi's being fused. I've attached a photo. Note that the photo is upside down. The fuse is a Fusetron dual element FNM 3 2/10. Not sure how to interpret the rating.

Has anyone looked into using PTC resettable fuses as an alternative to adding fuseholders, etc.? Here is an interesting article from Bourns, one of the manufacturer's of these devices:

http://www.bourns.com/pdfs/AppNotes_LSCN.pdf

For speaker protection, I'm not sure how their function would compare with a normal fast acting fuse. Advantages would be that they reset themselves once the current is removed, and they are as inexpensive as regular fuses.

[dynaco_dan]

>Someone mentioned early 10pi's being fused. I've attached a

>photo. Note that the photo is upside down. The fuse is a

>Fusetron dual element FNM 3 2/10. Not sure how to interpret

>the rating.

>

>Has anyone looked into using PTC resettable fuses as an

>alternative to adding fuseholders, etc.? Here is an

>interesting article from Bourns, one of the manufacturer's of

>these devices:

>

>http://www.bourns.com/pdfs/AppNotes_LSCN.pdf

>

>For speaker protection, I'm not sure how their function would

>compare with a normal fast acting fuse. Advantages would be

>that they reset themselves once the current is removed, and

>they are as inexpensive as regular fuses.

Hi there;

Bussmann FNM 3 2/10 amp is a correct size.

We an only guess, barring AR literature, as to it's power handling capabilities, in the 10pi's.

I never owned these speakers and this is the first time I read about such a large fuse, compared to the LST's even.

I would lower the fuse size down to a slightly more forgiving rating, because of their age.

Bourns PPTC seems to protect just the tweeter, as it appears.

If anyone has a few tweeters to sacrifice, there maybe an option.

Until a member comes up to the table with concrete evidence, I would stick to the original FNM fuses and even downsized, or fast blow fuses.

An even better method is the combination of slow blow for the woofers and fast blow for the uppers.

This is yet to be worked out.

Until someone comes up with that special combination, stick with a downrated FNM slow blow fuse.

Irregardless, we do want to protect our rare and valuable tweeters, and in the future this idea may be a godsend.

Good topic, thank you.

[Rlowe]

While I was looking at an AR newsletter in the Documents Section I found the following note by Tim Holl. It perhaps explains why some of the early AR11/AR10pi speakers had fuse mountings installed but later ones didn't.

Aug 1975

" To Fuse or Not to Fuse.

The 10pi and 11.

Fusing a speaker system, even with a fuse containing a thermal link as in the FNM series, can only give extra protection as Long as the units are not fed signals for which they are not designed. If an amplifier is overloaded or high frequency sine waves are fed to the system, fusing will not help. This is because the power handling of a speaker depends on the spectrum of normal speech and music where most of the energy occurs at middle and lower frequencies, and the tweeter thus does not have to handle high levels.

A fuse in series with a whole system will protect it only so long as that spectrum is maintained and is only of use on AR speakers where amplifiers of around 200 watts RMS per channel or greater are used. However, most domestic damage occurs to speakers with amplifiers of much lower power levels. In such cases, too much power is delivered at high frequencies although TOTAL power remains relatively low. It can thus be seen that a fuse sensitive to TOTAL power only helps in relatively few cases – a far better expedient is to use the volume controls sensibly.

Finally, a tweeter fuse might seem to be the answer. Unfortunately, the level of fusing required is such that the internal resistance of such a fuse would seriously attenuate the tweeter. We thus feel that it is best, to remove the fuse from production models and provide it in the type of instance shown where it is of real use (i.e. with high powered amplifiers) as an accessory.

Tim Holl.

[tysontom]

>While I was looking at an AR newsletter in the Documents

>Section I found the following note by Tim Holl. It perhaps

>explains why some of the early AR11/AR10pi speakers had fuse

>mountings installed but later ones didn't.

>

>Aug 1975

>" To Fuse or Not to Fuse.

>

>The 10pi and 11.

>

>Fusing a speaker system, even with a fuse containing a thermal

>link as in the FNM series, can only give extra protection as

>Long as the units are not fed signals for which they are not

>designed. If an amplifier is overloaded or high frequency sine

>waves are fed to the system, fusing will not help. This is

>because the power handling of a speaker depends on the

>spectrum of normal speech and music where most of the energy

>occurs at middle and lower frequencies, and the tweeter thus

>does not have to handle high levels.

>

>A fuse in series with a whole system will protect it only so

>long as that spectrum is maintained and is only of use on AR

>speakers where amplifiers of around 200 watts RMS per channel

>or greater are used. However, most domestic damage occurs to

>speakers with amplifiers of much lower power levels. In such

>cases, too much power is delivered at high frequencies

>although TOTAL power remains relatively low. It can thus be

>seen that a fuse sensitive to TOTAL power only helps in

>relatively few cases – a far better expedient is to use the

>volume controls sensibly.

>

>Finally, a tweeter fuse might seem to be the answer.

>Unfortunately, the level of fusing required is such that the

>internal resistance of such a fuse would seriously attenuate

>the tweeter. We thus feel that it is best, to remove the fuse

>from production models and provide it in the type of instance

>shown where it is of real use (i.e. with high powered

>amplifiers) as an accessory.

>

>Tim Holl.

>

The fuse holders on the early Advanced Development Division speakers, namely the first AR-10Pi and AR-11 models, were a hold-over from the AR-LST. When Tim Holl came on the scene around the time of the later-series ADD speakers, the fuse holders did go away. While a fuse might not save a speaker under all (or perhaps most) circumstances, it can provide a small level of protection against thermal burnout of the tweeters, particularly in fragile, older AR speakers. Perhaps the greatest benefit of fusing is the psychological reward of attempting to safeguard the speakers against thermal damage. It may not work, but at least you tried. I always dropped down a size (8/10 to 6/10) on the fuse for such speakers as the AR-3, but it would limit the output capability. Perhaps the safest way of protection, as Tim Holl said, is discrete use of the volume control.

--Tom Tyson

[tysontom]

>>Someone mentioned early 10pi's being fused. I've attached

>a

>>photo. Note that the photo is upside down. The fuse is a

>>Fusetron dual element FNM 3 2/10. Not sure how to

>interpret

>>the rating.

>

>Hi there;

>

>Bussmann FNM 3 2/10 amp is a correct size.

>

>We an only guess, barring AR literature, as to it's power

>handling capabilities, in the 10pi's.

FNM 3-2/10 is *much-too large* a fuse for the AR-10Pi. It was designed to handle the FNM 2.

Power-handling capability of the AR-10Pi was stated as: "May be used with amplifiers capable of delivering up to 150 watts continuous power-per-channel being driven to clipping 10 percent of the time, on normal musical source material." As we have stated before, the AR-10Pi could handle higher power levels than this -- peak power -- as shown in the Neil Grover live-vs.-recorded demonstrations put on by AR back in 1977. During those sessions the AR-10s were continuously driven to peaks of 800+ watts; and except for saturated transformers, the speakers seemed capable of handling this power without damage. There were two or three sets of AR-10s used at various stages for the live-vs.-recorded demonstrations. I have used the primary pair at home for many years, and they continue to work flawlessly.

--Tom Tyson

[dynaco_dan]

>>While I was looking at an AR newsletter in the Documents

>>Section I found the following note by Tim Holl. It

>perhaps

>>explains why some of the early AR11/AR10pi speakers had

>fuse

>>mountings installed but later ones didn't.

>>

>>Aug 1975

>>" To Fuse or Not to Fuse.

>>

>>The 10pi and 11.

>>

>>Fusing a speaker system, even with a fuse containing a

>thermal

>>link as in the FNM series, can only give extra protection

>as

>>Long as the units are not fed signals for which they are

>not

>>designed. If an amplifier is overloaded or high frequency

>sine

>>waves are fed to the system, fusing will not help. This

>is

>>because the power handling of a speaker depends on the

>>spectrum of normal speech and music where most of the

>energy

>>occurs at middle and lower frequencies, and the tweeter

>thus

>>does not have to handle high levels.

>>

>>A fuse in series with a whole system will protect it only

>so

>>long as that spectrum is maintained and is only of use on

>AR

>>speakers where amplifiers of around 200 watts RMS per

>channel

>>or greater are used. However, most domestic damage occurs

>to

>>speakers with amplifiers of much lower power levels. In

>such

>>cases, too much power is delivered at high frequencies

>>although TOTAL power remains relatively low. It can thus

>be

>>seen that a fuse sensitive to TOTAL power only helps in

>>relatively few cases – a far better expedient is to use

>the

>>volume controls sensibly.

>>

>>Finally, a tweeter fuse might seem to be the answer.

>>Unfortunately, the level of fusing required is such that

>the

>>internal resistance of such a fuse would seriously

>attenuate

>>the tweeter. We thus feel that it is best, to remove the

>fuse

>>from production models and provide it in the type of

>instance

>>shown where it is of real use (i.e. with high powered

>>amplifiers) as an accessory.

>>

>>Tim Holl.

>>

>

>The fuse holders on the early Advanced Development Division

>speakers, namely the first AR-10Pi and AR-11 models, were a

>hold-over from the AR-LST. When Tim Holl came on the scene

>around the time of the later-series ADD speakers, the fuse

>holders did go away. While a fuse might not save a speaker

>under all (or perhaps most) circumstances, it can provide a

>small level of protection against thermal burnout of the

>tweeters, particularly in fragile, older AR speakers. Perhaps

>the greatest benefit of fusing is the psychological reward of

>attempting to safeguard the speakers against thermal damage.

>It may not work, but at least you tried. I always dropped

>down a size (8/10 to 6/10) on the fuse for such speakers as

>the AR-3, but it would limit the output capability. Perhaps

>the safest way of protection, as Tim Holl said, is discrete

>use of the volume control.

>

>--Tom Tyson

Hi Tom;

Great advice from you as usual.

I have tried to pass on here what I know from my life experiences.

Seeing the crownaudio site's information is great as well.

We can only provide the information.

The individual driver fusing is something that I will maintain should be done,

Who will do all the leg work of evaluating which value fuse is a safe maximum.

There is also the work and materials to bring the wires out to meet the new fuseholders without diminishing the speakers value.

Yes, the resistance of a fuse does add some resistance to the load and will affect the damping factor.

If one has the choice of fusing as recommended originally, derating, a single fast blow fuse, or doing the individual driver fuseholders, the loss of a valuable tweeter is the alternative.

From my AR/Dynaco warantee servicing experience Dynaco A-25's went through about 100 to 1 woofers to tweeters.

AR/Dynaco drivers were usually the AR-4X woofers or AR-LST tweeters, and the Dynaco 10" woofer, which had burnt, charred voice coils, with about a 100 to 1 woofer tweeter.

For the AR-LST's usually all 8 of the tweeters were gone.

I don't remember an instance of warantee rejection by AR or Dynaco for any caused damage, even the obvious abuse.

Pat-4 pre-amps with stereo 120 amplifiers or SCA-80, mostly SCA-80 integrated amplifiers were the driving force.

Loud rock music seemed to be the most common cause behind the damage, overdriving the low powered amps too much.

Fusing wasn't an issue as I remember, except with my own personnal stereo system.

As with wearing a car seatbelt or a parachute, I do remember people sitting on their seatbelts to, most often the wearer will suffer less injuries than not wearing them.

It is infortunate that the manufacturers did not do all of the leg work for us, so that we could just pop in the correct fuses.

Going one step further, in household electrical boxes with the old standard sized screw-in fuses.

You can buy time delay fuses with standard bases and also with a reduced threaded base with an adapator.

You place the adapter on the fuse base and screw this setup in to the fusepanel.

You can now unscrew the fuse but the adapter remains locked into the socket.

You can now only use the appropriate sized fuse and no other in that specific sized adapter.

I read recently that an English speaker maker uses an odd ball (perhaps metric) speaker fuse.

It might be ok in a major city trying to find one but in a small town maybe impossible.

The end.