Removing Amp from Event 20/20bas

AndrewMc · Post by **AndrewMc** » Thu Apr 01, 2004 3:58 pm

I'm planning to soffit mount, but I can't get beyond the fear of having powered monitors cooking inside a sofit & burning the place down.

I was thinking about removing the Amps from events 20/20bas and relocating the amp to a custom box in a rack and then putting a new plate on the back of the monitors.

I emailed Event & they were very helpful - saying it was possible but making sure the back of the monitor is sealed well is crucial.

Barefoot - do you have any comments or tips on this idea before I start destroying good monitors?

thanks
Andrew

eric · Post by **eric** » Fri Apr 16, 2004 12:43 am

They actually vent heat out of the bass port. It's all open and spooky inside. Mine are jammed in tight with no room for air to circulate around the cabinets. Thay have been left on overnight several times when I was too lazy to turn them off and They barely get warm to the touch.
Eric

barefoot · Post by **barefoot** » Fri Apr 16, 2004 2:40 am

I haven't ever seen inside a 20/20, but from your descriptions it sounds like the rear amplifier panel is also the panel that seals the back of the cabinet? [Makes me seriously wonder about microphonics, shielding, cabinet solidity, etc.] Anyhow, this could actually be an opportunity to make improvements. You could seal the rear with a heavy solid panel. You might also add some extra internal bracing. In any case, since you're soffit mounting, the cabinet dimensions don't affect the acoustics (baffle step). So you can always add mass to the outside of the cabinet.

Can you post some pics of the cabinet and amp with the amp removed?

Thomas

AndrewMc · Post by **AndrewMc** » Sat Apr 17, 2004 8:33 am

Will post some photo's when I open them up.

eric has me thinking that maybe I don't need to remove the amps. Sounds like it would be ok - my only concern is that I wouldn't be able to sleep - I know for sure I would forget to turn them off.

giles117 · Post by **giles117** » Sat Apr 17, 2004 8:42 am

A Buddy I know has soffited his Events and is QUITE pleased with the results. his Are Powered as well.

Also... I NEVER turn my Mackies Off and have NEVER run into an overheating problem.

Of Course this summer will tell. LOL But I am airconditioned up in this piece.

Bryan Giles

AndrewMc · Post by **AndrewMc** » Wed May 12, 2004 5:36 pm

As requested - here are some photo's of the event20/20bas with the back off

- pretty cool looking inside - the port can be seen on the pic - there is a 90degree bend in the port tube to make it longer I guess.

The back plate is very thick and heavy. This acts as a heatsink for the transformer and some components on the PCB.

It doesn't look practical to relocate the amp - it could be done, but I would have to run the wires for the drivers a long distance (4 wires for both drivers - x2 monitors) and perhaps that wouldn't do the sound quality much benefit? Although I have no clue really if that would be a non-starter. I could just use 2 high quality speaker wires per monitor.

I could relocate the transformer fairly easily. That would cut back on the heat. The back panel gets so hot you could fry an egg on it.

barefoot · Post by **barefoot** » Thu May 13, 2004 3:28 am

Yeah, I think you should go for it!

As long as you use a large enough gauge of speaker wire (12awg), the extra length will have a negligible effect. So, don't worry about that. A simple plate of metal, plywood, or MDF covered with bat of fiberglass will take care of the rear opening. You can mount the amplifier in the soffit wall.

One modification would be to brace the cabinet, like I mentioned. I can suggest a method in detail, if you're interested. Another modification would be to shield the amplifier. In any case, just pulling the amp out of the speaker cabinet will help. There is almost certainly some microphonics happening with those electrolytic capacitors.

Thomas

AndrewMc · Post by **AndrewMc** » Thu May 13, 2004 5:50 am

Thanks for the reply.

I'm definately thinking I should go for it. If I'm going to do it I should make as many improvements as possible - so the bracing and shielding sounds like something I should do.

I talked a little bit to event tech support & they were very helpful. They said the same thing about the wire length being no issue (they did say to make sure the lengths were the same for each driver or the high frequencies could get out of phase) - plus they also mentioned adding some fiberglass to the new MDF back plate.

I was thinking that I could put the 2 backplates inside a rack mount box - they'l then continue to act as heatsinks and then wire up new connectors and pots to the rack box.

The only part that really is scaring me is the 3 trim pots on each amp - they are snug on the board and glued to the heatsink - you can see one in the bottom right hand corner of the photo. I would need to relocate these to stepped pots with knobs on the new rackbox front. Event told me these are 20K ohm Cermet VL pot resistors. Getting these off the board could be a disaster.

There is also a small LED on the monitors - shows power and goes red if the amp is 6db off clipping. I would need to get new LED's and put these on the rack boxes also.

Thanks again for your advice - without it I know I would be closing these puppies back up.

AndrewMc · Post by **AndrewMc** » Sun May 23, 2004 4:00 pm

I'm ready to rock & roll with this

Barefoot, whenever you get chance to give me your advice on the potential improvements - mucho appreciated

barefoot · Post by **barefoot** » Wed Jun 02, 2004 3:50 am

Andrew,

Here's the easiest way I've found to brace an already built cabinet:

1. Cut and file ends of threaded 3/8" or 1/2" steel rods to the same outside width (or depth) as the cabinet.

2. Drill holes into the cabinet on opposing sides in locations towards the panel centers, but where the rods will not obstruct any internal components. The holes should be approximately 1/64" smaller than the rod diameters. These should be accurately positioned and drilled perpendicular to the cabinet walls.

3. Lock two nuts together on one end of the rod and thread the rod through one of the cabinet holes. Keep threading it unit it's about 1" from the other side of the cabinet.

4. Unlock the nuts from the rod end and thread them onto the rod from inside the cabinet, along with washers. They should go on in this order: Washer, Nut, Nut, Washer.

5. Lock the nuts together in the center of the cabinet. Coat about 1" of both rod ends with slow curing epoxy or other adhesive, then thread the rod through the other side of the cabinet unit it's flush on both sides.

6. Unlock the nuts and bring them to both side of the cabinet. Tighten them firmly, but not so hard as to push out the cabinet walls and strip the holes in the wood. You can use glue to lock the nuts in place.

7. Wipe up any excess glue, let cure, and you're done!

Make sense?

Thomas

Jon Best · Post by **Jon Best** » Mon Jun 07, 2004 12:01 am

That's a damn good idea.

How about bracing a not-already-built cabinet? I wasn't going to bother with asking about this box, because I'm just building a single 15" ported bass guitar speaker (with an EV 15B s2 I already have), but I'd be interested to hear an opinion on bracing it without adding weight. I may just do what you have recommended above. For the record, it's 85l internal volume, with 2- 3" wide, 3ish" deep ports, 3/4" birch plywood. One tip I picked up somewhere- (maybe here?) I'm going to take it to the local spray-in pickup bedliner place and have them do the outside of the box.

AndrewMc · Post by **AndrewMc** » Fri Jun 25, 2004 2:58 am

Sorry for the dealy in responding. Many thanks barefoot for the detail on how to strengthen the cabinet. It all makes sense.

I will post some photos when I get to the stage of doing this mod.

Whenever you get a free moment - the other mods you suggest to shield the amps would be cool

Thanks again

Andrew