Testing to see if a horn is blown

JimmyM · #1 08-03-2011, 10:56 PM

Hey, need quick advice here...got a friend's old Sunn PA cab here and the horn isn't working. Any way to test to see if the driver's blown vs. if it's a bad connection? I have a multimeter if that helps.

Sorry if I didn't do a search but I don't want to be all night looking stuff up. Thanks in advance!

PhiDeck · #2 08-03-2011, 11:05 PM

What kind of driver is behind the horn?
Can you access its terminals, and disconnect the crossover?

stingraysvt · #3 08-03-2011, 11:05 PM

Quote:

Originally Posted by JimmyM

Hey, need quick advice here...got a friend's old Sunn PA cab here and the horn isn't working. Any way to test to see if the driver's blown vs. if it's a bad connection? I have a multimeter if that helps.

Sorry if I didn't do a search but I don't want to be all night looking stuff up. Thanks in advance!

I use a 9v battery to test "pop" drivers and horns. If it pops you have a bad connection. No pop, need a new diaphragm.

You can ohm a speaker to see if you are still getting any impedance from the voice coil. It would be worth trying to see what kind of reading you get, a horn most likely will be 12-16 ohms maybe even 32....

vin*tone · #4 08-03-2011, 11:07 PM

At a guess......run a tone through it and check to see if there's voltage across the terminals out of the crossover?

JimmyM · #5 08-03-2011, 11:27 PM

Sunn monitors ???

That's the cab right there, although this one's alot more beaten up. The horn wires are soldered onto the "crossover," which I guess is more of a high pass filter, eh?

Anyway, it's blown. Just checked it with my meter and got nothing but OL. Just wanted to make sure I could use that to tell if it was blown. Thanks guys!

Doug Parent · #6 08-03-2011, 11:34 PM

I have one of those EV horns by the way. Came out of an EV cabinet. Actually, it's a tweet, not a horn. I found the spec sheet from the EV website. Great tweet with good dispersion, a real keeper.

bassmeknik · #7 08-03-2011, 11:34 PM

Quote:

Originally Posted by JimmyM

Sunn monitors ???

That's the cab right there, although this one's alot more beaten up. The horn wires are soldered onto the "crossover," which I guess is more of a high pass filter, eh?

Anyway, it's blown. Just checked it with my meter and got nothing but OL. Just wanted to make sure I could use that to tell if it was blown. Thanks guys!

If you are sure you had the leads firmly connected then an OL reading indicates open circuit and the driver is definitely no good.

JimmyM · #8 08-03-2011, 11:42 PM

Quote:

Originally Posted by Doug Parent

I have one of those EV horns by the way. Came out of an EV cabinet. Actually, it's a tweet, not a horn. I found the spec sheet from the EV website. Great tweet with good dispersion, a real keeper.

It's a horn loaded tweet...close enough

I'm sure our local speaker repair joint should have a driver for it. This is for a little 30's-40's jazz gig we do at a really low volume and I know the owner's used it for at least a year with it being blown because it was blown last year when we worked together, too. All of a sudden last Sunday, he says to me, "That cab has been sounding a little muddy lately." LOL!

georgestrings · #9 08-04-2011, 05:57 AM

Many horns/tweeters can be fixed by replacing the diaphragm on them, and they're not usually very expensive...

- georgestrings

billfitzmaurice · #10 08-04-2011, 06:19 AM

Quote:

Originally Posted by stingraysvt

I use a 9v battery to test "pop" drivers and horns. If it pops you have a bad connection. No pop, need a new diaphragm.
.

Never test tweeters with a battery, if you do hear a 'pop' it could be the driver being blown.

staindbass · #11 08-04-2011, 07:11 AM

+1 on the no battery on a tweeter. 9v would probably blow most home stereo tweeters. if anything use a 1.5 v battery. what kinda driver on the horn? i dont think piezo tweeters show a reading for ohms,- or continuity ?

will33 · #12 08-04-2011, 07:40 AM

Yeah, I haven't damaged one testing with a little AAA battery from your tuner or something, keep that 9v away from there. If it's a piezo and it doesn't work just get another assuming all the wirings hooked up, they're like $3.

will33 · #13 08-04-2011, 07:45 AM

If it's that ev in the link it's a driver, not a piezo. The filter parts can throw off your meter readings, test it across the terminals on the driver. Getting a replacement diaphram will be a good deal cheaper than replacing the whole unit.

billfitzmaurice · #14 08-04-2011, 07:59 AM

Quote:

Originally Posted by will33

The filter...can throw off your meter readings,

It does a lot more than throw them off, it prevents any reading at all.

MikeBass · #15 08-04-2011, 08:05 AM

Is there any spit in the mouth piece?????

burk48237 · #16 08-04-2011, 08:09 AM

I was kinda shocked when I saw this thread. Jimmy using a cab with a Horn, are the planets re-aligning?

The fact that it was your PA cab explains everything.

will33 · #17 08-04-2011, 08:17 AM

Yeah, the caps, but I still get readings sometimes. The filters works so I assume the dc from the meter is somehow going "the long way around" and somehow finding it's way from one lead to the other......weird.

billfitzmaurice · #18 08-04-2011, 08:22 AM

Quote:

Originally Posted by will33

Yeah, the caps, but I still get readings sometimes. The filters works so I assume the dc from the meter is somehow going "the long way around" and somehow finding it's way from one lead to the other......weird.

What you're reading is the cap(s) charging. When fully charged you should get no reading, as a fully charged cap will not pass DC. If you do get a reading after the cap(s) have charged you've got a bad cap.

will33 · #19 08-04-2011, 08:29 AM

Quote:

Originally Posted by billfitzmaurice

What you're reading is the cap(s) charging. When fully charged you should get no reading, as a fully charged cap will not pass DC. If you do get a reading after the cap(s) have charged you've got a bad cap.

Aha!

I've likely never held the leads on there long enough to fully charge a cap with their tiny current. Learn something new everyday.

BassmanPaul · #20 08-04-2011, 09:14 AM

Quote:

Originally Posted by stingraysvt

I use a 9v battery to test "pop" drivers and horns. If it pops you have a bad connection. No pop, need a new diaphragm.

You can ohm a speaker to see if you are still getting any impedance from the voice coil. It would be worth trying to see what kind of reading you get, a horn most likely will be 12-16 ohms maybe even 32....

Using a 9V battery across the terminals of a high range speaker is one of the better ways of destroying it. They are simply not designed to handle DC. An 8Ω horn will respond to DC resistance measurement the same way as a woofer. it will not be anything more than 8Ω. You cannot measure AC impedance with a multimeter.