Fuze Protection

[Hibernator69 47]

I've read a few posts recently about people installing fuzes somewhere between the speaker and the amp.  

 

Anybody have any advice on what I should be looking for?

 

I noticed Parts-Express has some things on closeout, but have no idea if that's along the right lines or overkill.  

 

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=070-820&scqty=1 

 

http://www.parts-express.com/pe/pshowdetl.cfm?&Partnumber=070-850&scqty=1

 

 

 

 

 

[SteveFord 1,125]

http://www.parts-express.com/cat/fuse-holders/1423

 

Fuses for the tweeters are a good thing although others will cite possible sound degredation and disagree.

 

[TNRabbit 371]

It's a good way to protect expensive speakers if you run them on the ragged edge frequently. If you're a quiet listener, probably not necessary

[Hibernator69 47]

Let me try and summarize: if the dual M1.0ts are lighting up like a Christmas Tree, run don't walk and get some fuzes installed.

 

I don't think I've seen more than 3 lights yet (and that for the base speaker, so maybe at worst something for the tweeter might be reasonable.

 

In the latter case do you mean just the tweeter and add the fuse inside the cabinet after the crossover, or outside the cabinet before the speaker binding posts?

[zumbini 6,150]

Those big fancy fuse blocks you linked to are normally used in car installations.

They are designed to be visually impressive so they are mounted externally.

For home speakers I usually install screw cap fuse holders in the jack panels like this:

 

 

I you prefer not to drill holes in your jack plates, install in-line fuse holders or mount fuse blocks on the inside. 

Either way the fuses should be installed between the positive speaker terminal and the internal passive crossover. 

 

As for sizing, your best bet is to contact the OEM and ask them for their recommendation.

If the OEM is defunct or won't cooperate a fuse sizing chart like this can get you close.

(I recommend starting with a smaller fuse than the one indicated and working up.) 

 

[avguytx 229]

I'd be more inclined to use a small car interior light bulb like what ElectroVoice and other companies used inside of some of their cabinets.  I had some Interface C's at one point and they used them in there plus many, many car audio companies use the bulbs in their passive crossover networks for dissipating any "overage" of current to save doing a lot of Return Authorizations for blown tweeters.  They've always worked well and my Lightning Audio components use them, too.  (as did many Rockford components)  Just my $.02.

 

http://www.parts-express.com/pe/showdetl.cfm?partnumber=260-231 

 

My Norman Lab Model 9's used two manual reset circuit breakers in them but I completely bypassed them because they were a) tripping quite early, b) didn't make good connection and the sound would just quit at even low volume and, c) I could tell a major difference in the mids and highs once they were removed.  To replace them was $10 each and I didn't care to do that.  The only reason they were there was to keep customers from killing their drivers if they were under (or over) powering them.

[Hibernator69 47]

 

 

Those big fancy fuse blocks you linked to are normally used in car installations.

They are designed to be visually impressive so they are mounted externally.

For home speakers I usually install screw cap fuse holders in the jack panels like this:

 

 

I you prefer not to drill holes in your jack plates, install in-line fuse holders or mount fuse blocks on the inside. 

Either way the fuses should be installed between the positive speaker terminal and the internal passive crossover. 

 

As for sizing, your best bet is to contact the OEM and ask them for their recommendation.

If the OEM is defunct or won't cooperate a fuse sizing chart like this can get you close.

(I recommend starting with a smaller fuse than the one indicated and working up.) 

 

 

 

 

Took me a while to figure out the 2nd picture was the same panel from the inside. I take it the screw cap fuse is nice because you can change it easily if it blows?

 

I'll check the NHT manuals and call them if I have too. They are not real big on support for the older legacy products anymore though.

 

If I read the chart correctly, if I have a 6 ohm speaker, rated for 50-250w (don't know if that's continuous, lets assume it is), then I would want a 5amp fuse for the mid/high section 4x250w = 1000w peak. But maybe start with 3 or 4 amps and see if they blow frequently?

 

Why/when do you choose slow blow or quick blow?

[Hibernator69 47]

For a specific example:

 

My NHT VT-2 can be biamped. But it is split into a subwoofer and a mid/high (basically a VS-2 speaker). I haven't opened up the speaker to look, but am I correct to assume we're only talking about one fuse to protect the mid/high section (and not a separate fuse for each driver after the crossover)?

 

Also it seems there is little reason to worry about the bass, correct? Or is that only true in this case because the internal LPF to the subwoofer is still in effect and the woofer will never see huge peaks above much 125Hz?

 

 

[zumbini 6,150]

 

 

I'd be more inclined to use a small car interior light bulb like what ElectroVoice and other companies used inside of some of their cabinets.  I had some Interface C's at one point and they used them in there plus many, many car audio companies use the bulbs in their passive crossover networks for dissipating any "overage" of current to save doing a lot of Return Authorizations for blown tweeters.  They've always worked well and my Lightning Audio components use them, too.  (as did many Rockford components)  Just my $.02.

 

http://www.parts-express.com/pe/showdetl.cfm?partnumber=260-231

 

Your link does not work but I found the item by looking up the part number (260-231).

 

It appears to be a type of fuse but I can't find any info about how to properly size them.

 

FYI - They are 1-3/8 x 3/8 so they will not fit in a standard fuse holder (1-1/4x1/4) 

[avguytx 229]

 

 

 

I'd be more inclined to use a small car interior light bulb like what ElectroVoice and other companies used inside of some of their cabinets.  I had some Interface C's at one point and they used them in there plus many, many car audio companies use the bulbs in their passive crossover networks for dissipating any "overage" of current to save doing a lot of Return Authorizations for blown tweeters.  They've always worked well and my Lightning Audio components use them, too.  (as did many Rockford components)  Just my $.02.

 

http://www.parts-express.com/pe/showdetl.cfm?partnumber=260-231

 

Your link does not work but I found the item by looking up the part number (260-231).

It appears to be a type of fuse but I can't find any info about how to properly size them.

 

FYI - They are 1-3/8 x 3/8 so they will not fit in a standard fuse holder (1-1/4x1/4) 

 

Typically, I never installed them (nor have I seen them) into a fuse holder type setup.  They were soldered inline and either zip tied to a baffle or glued in place.  Some others I have seen use a small 12V 1-amp light bulb and solder in in the same fashion.

 

In my early car audio days, (mid 80's to mid 90's) it was always funny when customers would come back to the store and say they "swear they could see light coming from under their dashboards when they were jamming at night".  It was those light bulbs in the crossover networks doing their jobs!  haha 

[zumbini 6,150]

....I take it the screw cap fuse is nice because you can change it easily if it blows?....

Yes, accessibility is the main reason I mounted them externally.

 

....If I read the chart correctly, if I have a 6 ohm speaker, rated for 50-250w (don't know if that's continuous, lets assume it is), then I would want a 5amp fuse for the mid/high section 4x250w = 1000w peak. But maybe start with 3 or 4 amps and see if they blow frequently?

The chart is just a guide but yes, that sounds about right, and definitely err on the side of caution.

I started with MDL3/4 on my tweeters based on the OEM's recommendation of MDL1-1/2.

Over the course of 2 years I worked my way up to MDL2 and just recently bumped that to MDL2-1/4.

(Turned out that this particular driver was brand new to the OEM and they had under-rated it intentionally.) 

 

....Why/when do you choose slow blow or quick blow?....

Again I used the OEM's recommendation (time delay for the tweeters; fast acting for the mids).

I suspect that Legacy made the choice based on the predicted failure mode for each driver.

As I understand it, tweeters have small voice coils that do not shed heat very efficiently.

When driven hard the VC can heat up to the point where the coil wire coating melts and a short occurs.

(This can happen to smaller mids too but more often they suffer mechanical failure due to over-extension.) 

 

My NHT VT-2 can be biamped. But it is split into a subwoofer and a mid/high (basically a VS-2 speaker). I haven't opened up the speaker to look, but am I correct to assume we're only talking about one fuse to protect the mid/high section (and not a separate fuse for each driver after the crossover)?

Yes, as long as you adjust fuse size to reflect that the mid/highs only see a portion of the power applied to the speaker.

For instance, if the speaker is rated for 250 watts it's likely that the mids/tweeters see only 1/3 to 1/2 of that.

(My mains are 2-way speakers with a ribbon tweeter between two 6.5" mids in a D'appolito configuration.

There is also a conventional 1" dome tweeter on top that can be adjusted from 0-100 for "ambience".

Frequency response is 3dB down at 50 Hz so low bass is supplied by a pair of 12" subs.)

 

....Also it seems there is little reason to worry about the bass, correct? Or is that only true in this case because the internal LPF to the subwoofer is still in effect and the woofer will never see huge peaks above much 125Hz?

It is much less likely that you will damage an 8" or larger diameter woofer in "normal" use.

However, all bets are off if the amp fails or you were to accidently short the speaker leads.

 

 

[Hibernator69 47]

Thanks Z for the info about power splitting. To help me understand I just think of my VT tower as a two way system like your legacy speaker, but at this point Ive learned enough to open it up and adjust accordingly.

 

Any good place to pick up fuses locally (Radio S, Car parts store?), or do you just check Amazon and/or Parts Express?

[Hibernator69 47]

 

 

I'd be more inclined to use a small car interior light bulb like what ElectroVoice and other companies used inside of some of their cabinets. I had some Interface C's at one point and they used them in there plus many, many car audio companies use the bulbs in their passive crossover networks for dissipating any "overage" of current to save doing a lot of Return Authorizations for blown tweeters. They've always worked well and my Lightning Audio components use them, too. (as did many Rockford components) Just my $.02.

http://www.parts-express.com/pe/showdetl.cfm?partnumber=260-231

My Norman Lab Model 9's used two manual reset circuit breakers in them but I completely bypassed them because they were a) tripping quite early, b) didn't make good connection and the sound would just quit at even low volume and, c) I could tell a major difference in the mids and highs once they were removed. To replace them was $10 each and I didn't care to do that. The only reason they were there was to keep customers from killing their drivers if they were under (or over) powering them.

 

LOL, took me a while (and a couple more posts that followed) to understand how this would help. For some silly reason thought this was in parallel and old absorb high currens. But how would you ever know if it blew? Snicker away chuckleheads ... You all had questions like that once, even if it was when you were 8 and rebuilding your dad's Chevy big block at the time.

 

:-)

[zumbini 6,150]

...Any good place to pick up fuses locally (Radio S, Car parts store?), or do you just check Amazon and/or Parts Express?

When I'm in a hurry I check my local Radio Shack (poor assortment), then Lowes or Home Depot.

When I have time I look around but usually wind up ordering from Newark (a Bussman distributor).

I recently bought a 50 pack of MDL2-1/4's on ebay for $7.50 shipped. 

 

BTW - I'm not adverse to a bulb-type fuse as avguytx suggested but I have no idea how to size one for the application.

[weitrhino 1,443]

Hibernator,

 

You might find this thread useful in learning about fuses and protection.   If breakers are more to you liking you may find what you need here.

[Torr 8]

sweetwater. com sells those lamp fuses also.....