I'm getting ready to drill some holes in my boat this weekend! One of the multiple projects will be the addition of a pair of speakers, where previously there were none. I'm going into fiberglass, and am thinking of fabricating some plywood backing for mounting of the speakers. The area is not one that sees water.

Questions - What's the best way to mount the backing board to the backside of the fiberglass, an adhesive like 4200 or 5200? Should the plywood be prepped in anyway prior to install - that is sealed or painted?

Here's a pic of the install in a 'sister ship' that I'm flat out copying.



Thanks for the idea txjole!

Will your boat now have 6 speakers? If so, any changes to the stereo to accomodate?

I ordered my boat with the 'standard' stereo, not wanting to pay Four Winns an additional $1200 for $300 of equipment. So, it came with 4 middle of the road Clarion coax speakers (two in the bow, two in the cockpit) driven by a Clarion CMD4 4x60W Head unit. I'm adding a Clarion APX480M 4x80W amplifier, two higher end Clarion CMCX7.1 7" two-way coax speakers and a 10" Polk Audio MOMO Sub into the cockpit. I'll leave the Head unit's 60W/channel to the stock speakers, 80W/channel from the amp to the new 7" speakers, and a bridged 160W to the sub. The head unit/amp combo allows for non-faded inputs to the sub, and faded rear inputs to the two-ways, so I retain fading control between the two stock speakers in the bow, and 4 in the cockpit.

Should be a decent upgrade for about $225 in stereo components and about $105 in wiring components. I snagged some real deals on equipment for those that notice my math doesn't look right, retail would be closer to $600. I was going to go Polk Audio db650 for the new aft speakers, but the appearance was so much different from the existing white grilled Clarions, I backed off after buying a set. Probably should have just bought two more sets and replaced the four stock speakers too. Oh well, at least I'm leaving room for future upgrades.

So is the consensus that regular treated plywood mounted with 5200 is fine for bracing material for the coax installs?

Is the glass really thin? When I added mine the was no reason to add any type of backing. In fact the factory installed ones didnt have it either.

Backing is not a bad idea in my mind. Also, don't forget to put enclusres if you can to help with low end response.

I think 4200 would be sufficient. It's "removable" if you ever find the need to latter.

Did you compare the Clarion CMCX7.1 7" and Polk Audio db650 in store? I was debating between these two also. Same thing as you , the looks of the Polks are holding me back. To bad they don't offer white speaker covers.

You actually don't need much of anything to hold it in place. Make the screw holes in the fiberglass just a little oversized, hold the backer in place with a few dabs of silicone and tighten the speaker in place.

Don't use 5200 or it can't be undone. If the glass is very flimsy then use a backer but it probably is not necesary.

Use the 4200. Not a bad idea to use some sealer of some kind. Don't worry about what it looks like. An enclosure is a good idea. Drill the wood before putting any screws in it..Not oversize, but same size of screws or starter holes for them. It'll make screwing in the screws a little easier and less likely the screwdriver will slip and go thru either the speaker itself or your finger and blood gets... um... yea you get the idea..

After cutting the holes I found that Four Winns applied some type of coating to the back of the fiberglass. Check out the piece cutout below - the coating is very uneven, less than 1/2" on one side and just shy of 1 3/4" on the other side of a six inch cutout. This variance in thickness was enough to discourage me from installing backing board on the first go round. I might revisit this in the future.

Some kind of sound insulation to keep the echoes away maybe?

I think you will be happy with the results without an enclosure. Unless you're talking about subs, you only need the mounting face. The idea is to seperate the front wave from the back wave since they will tend to cancel each other out. Similarly, having too many speakers playing the same source can cause cancelations,(think "noise canceling headphones".

+1

As long as the face/finished surface is even and will flush up against the back of the speaker flange, with enough depth, mount those puppies up.

I wouldn't worry about the varied thickness behind. That backing material might help dampen rattles and standing waves (a good thing).

I don't see a need for any backing board, I'd tap directly into the fiberglass (masked and predrilled)

That's just what I did.

Yeah!

How do they sound?

I dunno, I'm waiting to get the sub in before connecting the remote power lead to the amp. Maybe this weekend.

Doh! Wanted to do a before and after comparison with the two new speakers and amp, prior to adding the sub. I installed the amp in fairly tight quarters, as can be seen here based on the OEM install.



Guess I had the gain set too low, as I got no sound from the new speakers, and didn't want to go too far with the volume because of time of day and the fact that the head unit is still driving the old speakers. Unfortunately, the gain controls are on the far side of the amp, and inaccessible with the tools I had at hand. Guess I'll have to pull it and rig longer RCA jacks on a temporary basis, or use a mirror, flash light, and stubby screw driver to adjust gain where it sits. Then I'm gonna have pull this stunt again when I get the sub enclosure built and installed. Better stick to my day job.

Does the amp have an option for remote gain? If so, I would look into it. The deck may also have a output gain for the amp which could help.

No remote gain. But I did find that the head unit has a menu item for adjusting gain on the non-fader inputs I'm going to be using for the sub, thanks for the tip! Could come in handy.

Jim_R did you get it working? How does it sound. Nice install on the speakers they look real clean. Nice job.

Nice job...

Here is a tip.

I made a MP3 file that is basically a frequency sweep. Copy it to iPod or whatever you need to play it through your stereo.

Start with a low volume and run the MP3.

All loudspeakers have a resonant point where they vibrate uncontrollably. When put into an enclosure, mounted to a board, or whatever, this resonance is dampened, frequency shifted, or eliminated alltogether.

And even if eliminated, it can still vibrate the surface it is attached to, which can cause something else to vibrate. Say that cup holder - maybe at a certain frequency, it could vibrate due to the speaker. Its not a problem if it does, unless it is audible. Then you want to keep it from vibrating.

So the MP3 file is an aid in detecting unwanted audible vibrations in nearby components, kick panels, or other things.

I am sure we have all seen the kid that put a subwoofer into their car and the quarter panels are vibrating wildly and making an awful noise.

So what this MP3 file does is to sweep through all of the audio frequencies. The purpose is to detect any unwanted vibration in the speaker, surface it is attached to, or other nearby objects.

As the frequency sweeps, you might find that cup holder vibrating at one spot along the sweep. If not, crank up the volume a bit, and try it again. Continue cranking up the volume in steps until you are satisfied that nothing nearby is vibrating and making noise.

While not perfect due to the MP3 format, the waveform should sound fairly clean. If you hear any distortion, something is probably either vibrating. You may not be able to completely get rid of the anomalies, but you should be able to improve the sound.

If that cupholder is vibrating, a bit of VHB or silicone will secure it. You might also find you have to tighten down a screw or two near the speaker. You might also find that you may have to wedge in, glue in, or 5200 in a small stiffener piece of wood somewhere to completely get rid of the vibration.

I need to stress that vibration itself isn't usually what is annoying, but rather when the vibration causes a panel to audibly rattle is what you are trying to fix.

Anyway, its a nice way to perfect your sound system that you paid a lot of money to build.

Here is the MP3 file. I created the file so there are no copyright issues.

http://members.toast.net/boatguy/sweep.mp3

It doesn't cost anything to do this, and takes maybe 20 minutes out of your time, but in most cases will improve your sound system.

Nice Al. I will add this to my iPod. I used a 50Hz sine wave and a 1kHz sine wave at "0" level to set my amp levels. This will add to my ability to tune it in and find vibrations.

Thx.

NICE INSTALL

NICE INSTALL

I did adjust the gain this past weekend. The new speakers sound great. I installed a contour switch inline on the head unit remote power lead, figuring that there'd be some situations where I'd want to hear music, but not run the amp. So I used it to do a 'before and after' for the admiral. Even she agreed that the stereo sounds much better now. And, I have yet to install the subwoofer.

I did find time to custom build an enclosure for the sub that will fit under the rear bench, facing forward, and slightly downward. (The bench had a 75 degree angle to it, which accounts for the slight downward angle.)

Here's the box, all but wired and installed.



Al, thanks for the sweep mp3 file! I'm certain to need it after I install the sub.

Jim_R did you get that sub firing yet? Hows it sound?

Yup, got it dialed in last weekend - sounds great! Exactly what I was looking for, and a major improvement. It's real nice being able to hit a switch and hear the 'stock' stereo, then hit it again to bring the 'upgrade' online.