Baffle Shapes and Frequency Response

[cogitech]

Somewhere in my browsing I saw an analysis of various shapes of baffles or baffle plates with corresponding frequency response graphs, showing which frequencies (if any) are boosted by different baffle shapes.

I've googled and googled and now I can't find it.

Anyone seen this before? Have a link?

[adason]

Diffraction

[cogitech]

Thank you. That is not exactly the one I was looking for, but it basically serves the same purpose. The one I was looking at before included a triangle and a star shape (I think).

But as I said, thanks for the link.

[jimbro]

Hi cogitech - I wanted to answer some of your construction questions you posted on the full range thread over here. I think the glue you described is contact cement. I'd stick with carpenter's or polyurethane (gorilla). As far as silicon vs acrylic caulk I have a heck of a time removing silicon if it gets somewhere I don't want but ymmv I guess. I like it because it's more elastic and lasts longer but really no biggie. If you have a router you can get very accurate results with a straight edge and a flush trimming bit. Just cut all your panels a little big and trim them to size. If your bit is long enough you can trim several panels at once. Hope this helps. Jim

[cogitech]

Originally Posted by jimbro

Hi cogitech - I wanted to answer some of your construction questions you posted on the full range thread over here. I think the glue you described is contact cement. I'd stick with carpenter's or polyurethane (gorilla). As far as silicon vs acrylic caulk I have a heck of a time removing silicon if it gets somewhere I don't want but ymmv I guess. I like it because it's more elastic and lasts longer but really no biggie. If you have a router you can get very accurate results with a straight edge and a flush trimming bit. Just cut all your panels a little big and trim them to size. If your bit is long enough you can trim several panels at once. Hope this helps. Jim

Thanks very much for the advice on the glue. I'm going to Home Depot on the way home from work today to pick up some big clamps and some more glue (I only have a small bottle of LePage carpenter's glue right now) so I will look at what they have for glue and then decide.

I don't think the glue I saw the speaker factory using was contact cement (which is usually a clearish yellowy-brown, and is typically applied to both surfaces, allowed to dry and then bonded). It was opaque greyish-yellow and seemed almost like the stiff consistency the of light wipped icing but super-sticky. The beads they were laying had almost as much body as a bead of Crest. In fact, it really resembled flooring adhesive in colour and body, but it seemed "lighter" as if it was aerated. Anyway, it is neither here nor there because I am going to stick with carpenters or Gorilla

Re; Cutting. I had already completed all the cuts for the main panels and they are pretty good, but not perfect. Yesterday I clamped all the side panels together as square and straight as possible and then took an orbital sander with 60-grit to them. They are really darn close to perfect now. Nothing that glue can't compensate for, I figure.

I will have to re-cut my holey braces though, as they are about 1/16th of an inch too shallow (not sure how I screwed them up). I could McGuyver in a thin layer of something or sandwich in some Mighty Putty, but I want to do this right, and I have enough leftover BB to re-cut new braces, so that's what I'll do.

[pjanda1]

I haven't been paying attention, but keep in mind that baffle shapes will affect a fullrangers response (in the treble) to a much lower degree (due to their controlled dispersion) than they will a tweeter.

Gorilla glue is great, but depending on the size of your cabinet, it can get expensive. I use PL Premium Construction Adhesive in a caulk gun. Cleanup is easier too. Scrap the extra off just as it it gets a little solid and looses its sticky-ness. It will fill decent gaps, so as long as you use enough, caulk is unnecessary. With either PL or Gorilla, be sure to keep it off your hands and any clothing you care about. It does not clean up with water like wood glue!

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[cogitech]

Paul,

Thanks for the recommendation. Is the PL Premium sandable? I can scrape off the excess when semi-dry as you suggested, but will that remove every trace of it? I do not want any residue left (or I want to be able to sand it off) because I plan on staining/finishing the BB.

[cogitech]

I had no idea choosing glue would be so complicated

At least I now know some good options, and I know what my criteria are:

- Good bond strength
- Moderate gap compensation
- Sandability

[planet10]

Originally Posted by cogitech

It was opaque greyish-yellow and seemed almost like the stiff consistency the of light wipped icing but super-sticky. The beads they were laying had almost as much body as a bead of Crest...

Likely the construction adhesive like Paul uses.

I will have to re-cut my holey braces though, as they are about 1/16th of an inch too shallow (not sure how I screwed them up). I could McGuyver in a thin layer of something or sandwich in some Mighty Putty, but I want to do this right, and I have enough leftover BB to re-cut new braces, so that's what I'll do.

Just use a wooden or (pile of) paper shim.

dave

[cogitech]

Originally Posted by planet10

Likely the construction adhesive like Paul uses.

That makes sense. Do you know if this stuff is sandable?

Just use a wooden or (pile of) paper shim.

dave

I thought of that, too (heck, even my wife said "just stick something under there") but I am not sure how to secure the layers of paper in position. Staple gun? But then i would be gluing the brace against layers of stapled paper. That doesn't seem like a good idea at all... I guess I could do alternate layers of paper and glue, but that seems like more work than cutting a new brace. I also think I would have more success cutting a new brace than cutting a 1/16th inch wood shim

One thought I had was to glue the brace to the back panel and then run a strip of good quality weather strip along the top edge. The brace would then not be bonded to the front panel (baffle), but there would at least be the compressed weatherstripping in there to provide support. But then I thought that this would really do nothing to keep the front panel rigid as pressure fluctuates in the cabinet... Perhaps that's not a concern?

As you can tell, I like to over-think things way too much.


I'm going to need to figure out how secure the layers of paper anyway, so I will know how to do it when it comes time to tune the gap between the driver base and the driver brace... Staple gun seems like a good choice for that, no?