'horn removal' or: deconstructing an A5/A7/828?

[gearfreak]

Open to thread search suggestions if anyone has any, I've not had much luck so far.

Anyone deconstructed their A5/A7/828 cabinets with a view towards saving the horns or cabs for reuse?

Presumably one or the other gets destroyed in the process... but maybe there are some tricks/pitfalls to learn from.

Mine are late model, mostly MDF or whatever is not the plywood, with full width-baffle... but I'm interested in hearing anyone's experiences with whatever type.

thanks!

[rogerh113]

I did deconstruct a pair of Altec Magnificent cabs, and the process went very well. Those cabs were vintage plywood, so what you have may behave differently. I was also planning to reduce the width and depth of the cabs to accommodate a different driver, so I could afford a bit of damage at the very sides.

Everything came apart pretty much intact, with the real key taking your time and loosen the elements bit by bit. Probably even more important in your case. My primary tool was a putty knife that I could pound with a hammer (metal handle on the putty knife). You need to start at one end of a joint, and slowly tap up the putty knife from the inside (if possible), Once it is up, wiggle it out and slide in a spacer (another putty knife) into the little gap, and move a bit further down the joint. Once the joint is opened a bit, you can insert larger tools in there and slowly pry it apart. I also removed the base horns intact, and gave them to a fellow Altec forum member.

It does take time, but it can be done.

[GM]

How barbaric! FWIW, I was taught to at least use a heat gun. Best is to soften glue joints with denatured alcohol or acetone if a really tough one, though usually the latter will ruin any sort of finish, so use small art brush, tiny syringe, etc., even when working on the inside and soften in increments.

Still the most popular it seems and there's others I wasn't aware of, so options abound : softening furniture glue joints to dissassemble - Google Search

GM

[gearfreak]

Thanks to you both!

So rogerh113, in your case you took the outer panels apart then reconstructed the boxes afterwards?

My line of thinking was that I could coax the horn out without exploding the exterior... maybe that's the wrong idea then. :-)

[GM]

Dunno, maybe get some insight from build pics? mfk-projects Vintage Altec

GM

[rogerh113]

Actually I gutted the inside of the cabinets first, just leaving the shell. Then I took apart the shell.

When I rebuilt the cabs, I used hide glue. If they happened to use hide glue when they were originally built, then water and heat will release it. If you have never used hide glue, then it is great stuff to work with and you might want to give it a try.

This is the finished product - my first, and likely only, speaker build project.

[gearfreak]

...Those cabs were vintage plywood, so what you have may behave differently...

I think we have found this out for sure.

a) remove cleats from mounting baffle board
b) putty knife and 5lb mini sledge
...and a lot of persuasion, and the baffle is out.

What this reveals:
- there are ~26 brads/nails holding the baffle at:
-the cabinet sides (no glue)
-the baffle opening (to structural uprights hidden in the horn cavities) w/glue
-the horn 'angle board' w/glue
-the baffle sits in a dado slot where it meets the 'top' of the cabinet

... and confirmed as suspected initially, the horn 'angle board' is dado'd into the sides of the cabinet. This pretty much kills the idea of removing the horns intact, while preserving the outer cabinet.

I'd be nice to keep the 'angle board' in situ as a cross-brace (and potentially the basis for driver support).
I could swiss-chees it with hole-saw(s) to make it less acoustically obstructive.

Ultimately though, if
-the front of the cab is to remain the front,
-the new baffle board is to be recessed (not just a full width/height board tacked on)

...then it will need to come out.

[GM]

Yikes! OK, you for sure have 828 cabs whereas Roger's are 825.

Anyway, just from your description, sounds like you can use a magnet to find any nails that need punching through the outer panels to allow one side to be pried open enough to disengage the dado, then slid out the back. Putty mixed with sawdust makes a great hole filler.

GM

[gearfreak]

Thanks GM. Yup, 828's. Thanks for the expansion suggestion, but I don't think these thin-ish sides would survive it.

The horn 'angle-board' dado extends to the front face, suggesting it might be 'slid' out, but: nails.
I don't want to bother with body work so will just rip it down the middle and hope to keep the kerf clear of the "port frame", to remain a brace.

I've always expected to brace the interior, and would like to see what I can come up with for post-tensioning.

So yeah, this is not about saving the horns anymore, in case I threw the plot for everyone.
It's just about reusing a big box to be an easy ~13? cuft experiment (sealed) for the 416-8C.

There are 4 cabs.
So the progression then could be to ~26 cuft (sealed) experiments - and then potentially on to an MLTL.


What strikes me now, is should I make use of this 'slot-loaded' (for lack of term) baffle from the horn?

The LF target is only up to 250/300hz or so, so seems it might be feasible, but I will need to re-research.

[GM]

You're welcome!


Bummer. Only barbed/ringed nails faze me, but it is what it is, so in round numbers the cab is just barely an acceptable 'room' ratio, hence minimal damping requirements.


When getting serious about panel bracing in large cabs, especially one that's a high aspect ratio, it normally starts with vertical boards on edge with 'tie' bars or similar offset at an acoustic or golden ratio to somewhat randomize panel resonance. Top/bottom plates can often just need a diagonal board on end if the top is massive, so always recommend something heavy/removable on top if not built in.


Empty, ~15 ft^3, good size for most Altec/GPA 15" tuned to Fs with some form of EQ, though too big for 803A unless significant EQ is used due to much higher Fs.


Re sealed, with such a high Vas driver there's no audible difference between ~14-26 ft^3, so might as well do some form of MLTL and plug the vent to compare.


Re using the sloped panel to create a folded horn of sorts; probably can get something decent as an odd shaped path length vented [mass loaded] TL [MLTQWT], so will see what hornresp has to 'say' as time permits. The driver's total specs sets the cab's impact on it, so 20 or 20,000 Hz, it makes no difference where the XO point is or its slope order, just how acoustically far away it is from the XO point.


GM