speaker baffle or not for 8 inch speaker

[Hebert]

Hi,

I thought it would be fun to build the champ micro in a small cab with an 8-inch speaker and have it look a bit vintage radio so I found pictures of other people's amps and built what is shown in the attachment. But now I realize that with this design there is no baffle. Is this going to sound terrible with a speaker attached directly to the front? If it will sound bad could I just build a baffle and stick it inside against the front and attach the speaker to the baffle over the hole?

[jjasilli]

But the front is the baffle???

[Hebert]

yes you are right so perhaps all is good. I thought a baffle need to be "floating" connected by only two opposite sides. if not then great. thanks

[jjasilli]

Yes, all is good.  A baffle need not float.

[sluckey]

There is one thing that concerns me about your baffle...

Looks like you used the same glued up solid pine boards for the front as you used on the sides? Solid pine is very prone to cupping and will also shrink and expand across the grain. A 12" wide board may vary in width as much as 1/4" with seasonal changes in temp and humidity. Using glued up narrow boards to make a wide board tends to minimize cupping and shrinking/expanding, but doing so does not eliminate either.

My point is that front baffle is not very stable. As it moves it will try to distort the small speaker frame. Doesn't take too much pressure to warp a small speaker frame enough that the voice coil rubs. You could probably twist that small speaker frame with your bare hands, enough to make the speaker useless. Speaker and baffle will have to fight it out to see which is stronger. I would be tempted to mount the speaker on a 1/2" plywood baffle and mount the baffle inside the cab. Plywood is much more stable than solid wood. Maybe I'm being over cautious?

Also, on the cab, I notice the right side (as viewed from the back) has the grain running front to back. The other side has the grain running top to bottom, which is a more standard orientation. This will create a cross grain issue that will tend to pull fasteners loose, or pop glue joints, or even split wood. Woodworkers try to avoid this situation.

[jjasilli]

Sluckey makes valid points.  But since the box is already built, my suggestion is to keep it and finish as-is.  For future builds, Russian birch plywood baffles are generally preferred for guitar amps.  Russian birch has no gaps in the layers, and is harder than builder's grade plywood.  Also guitar speaker baffles are generally thinner, in the 1/2" range.  This improves bass response, because the speaker can more easily vibrate the baffle board as a whole.  That larger surface can generate better bass.  (None of this applies to hi-fi speaker cabs).  Lots of info on the internet or post here.


This is a learning experience with no necessary right answers.  I suggest you should see if you like the sound of the project as-is, before changing it.  Once built you can the amp into another speaker enclosure to compare tone.

[Hebert]

Doesn't take too much pressure to warp a small speaker frame enough that the voice coil rubs. You could probably twist that small speaker frame with your bare hands, enough to make the speaker useless. Speaker and baffle will have to fight it out to see which is stronger. I would be tempted to mount the speaker on a 1/2" plywood baffle and mount the baffle inside the cab. Plywood is much more stable than solid wood. Maybe I'm being over cautious?

A

very good point, think I will build a baffle that fits inside the cab

[jjasilli]

I don't think building a baffle inside the amp is worthwhile.  Another possible option is to cut-out the existing front panel, leaving maybe +/- 1" all around, as a "mounting bracket".  Then mount a proper baffle to that.  If necessary, maybe you can rabbet the "mounting bracket" all around to recess a baffle board into it. 

[1blueheron]

All is not lost.  Although Sluckey is correct about solid sawn pine moving and cupping, this can likely be averted by glueing and screwing a couple 3/4"X 3/4" battens perpendicular to the grain on either side of the speaker inside the cabinet on the back of the baffle. Predrill and countersink screws about every 2-3 inches and make sure you have an even coat of glue so there are no voids that can vibrate or rattle.   This is basically the same thing done on a smaller scale inside a guitar to prevent the spruce top from warping.  Solid sawn pine has nice acoustic properties for a lively speaker cabinet and although not as stable as plywood, it will have none of the voids which would be common with big box store plywood.    Another possibility is to glue a peice of 1/2" baltic birch plywood to the back of your baffle so as to create a piece of plywood with a very thick pine "veneer" LOL.  The plywood will give it stability and prevent cupping.  Use a good quality waterproof wood glue like Titebond 3 with an even coat and plenty of screws until glue is set up.  48hrs or so.  then you can remove screws if desired.  Either of these methods should stabilize enough to prevent your basket from getting warped.  A lot of baskets get warped just form folks over tightening the screws or misaligned holes etc.

[Hebert]

thanks that is very good information.