Is it possible to partially fry the horn?
 

Greetings,

I think I blew the horn in my Mesa Boogie PowerHouse 412. It seems to work OK at low volumes, but at high volumes it sometimes produces just a farting sound (like "prrr, prrrr") and cuts out momentarily. The other speakers are fine. Is that possible that a partially damaged horn would do that or is it the amp that's having a problem?

Once I played with a bit too much distortion and felt a burning smell coming from the horn. I switched everything off and let it cool down; it worked afterwards and I thought I got away with it, but I have a feeling that something's melted.

Is there any good way to test it? It seem like it's glued to the cab (is it really?), so I can't easily take it out and check.

Thanks in advance

MP

Yep, you probably damaged the horn, and yes that is very common, and yes it is possible for it to still sound OK at lower volume.

Another possibility is it could be physically vibrating, like if a glued seam got loose, or a bolt got loose, or a plastic part got a small crack in it, etc.

No worries, thanks for clearing this up. It's not vibration, I'm pretty sure, there is a distinctive sound that comes out of it and it's not vibration.

Is it bolted to the chassis or can it indeed be glued? I couldn't see any bolts. Gluing seems a bit drastic, but who knows?

Is there any online shop where I could order a replacement? Mesa sells spare parts online, but they list the drivers only. Couldn't find any horns on their website.

http://www.parts-express.com/cat/hor...ed-tweeters/35
This is a good reliable company, but I don't know about shipping to Oz.

It does seem weird if they just glued the horn in, but it is entirely possible. Saves on the cost of screws! Are there screw holes in the mounting flange of the horn, where you can see no screws? Or are there no visible screw holes? If no visible holes, then I'd scrape away any paint that might be hiding those holes, see if maybe it was screwed in and then filled/painted over. If the holes are visible, with no screws in them, then try carefully cutting around the edges of the flange with a box knife while pushing from the back of the horn, to see if an edge will lift up a bit and reveal the situation better.

I'll have a closer look. There are no visible screws (there are on the other speakers and they come out easily). I can probe around to find out, although the horn is firmly set in in place and doesn't want to move. I can pry it gently to see if it's been glued. I'd be disappointed if it had, all other Mesa stuff seems to be perfectly serviceable, this would be quite a fail. Yeah, one shouldn't appreciate caring for the cost of a 4 screws on a ~3k$ cab (that' show much they are/were in Au).

Anyway, I'm more focused now. I can give it to the tech shop although they will take ages to fix it and I'm pretty handy with a soldering iron.