Small Syns

nc535,

Thanks, that is a good tip, hadn't thought of that! It would be a bit more confidence inspiring than the plumber's putty for the long-term. I'm not really worried about it falling out (it is in there quite firmly, but I don't like wondering whether the liquid in it might leach out over time into the cones)

Bill
 
I'm not sure if bondo is a good idea. I've built a few Synergy horns using the Pyle and QSC waveguides, and I frequently had the following issues:

1) Over time, about half of my midranges died. The reason they died was that I didn't leave enough room for the the woofer's excursion, and the surrounds ripped.

2) The mounting plates for my midranges frequently fell off. This is because the mounting plates would delaminate from the waveguide. This was a problem with the QSC in particular, there's something about the plastic they use, it's very difficult to get anything to bond to it. Eventually I gave up on trying to find a good adhesive, and I simply ran bolts all the way through the mounting plate for the midranges right through the horn walls. But that's ugly and probably causes diffraction.

3) Any type of shrinkage in the adhesives tended to cause issues. This is why I'd stay away from Bondo - it shrinks when curing. IIRC, epoxy doesn't suffer from this as much.

Hope that helps. 3D printed waveguides and wooden waveguides mostly avoid these pitfalls.
 
I would never ever ever use Bondo brand body filler...or anything. Horrid stuff.

If you are using body filler, something like Rage Gold Extreme sands like butter. But it won't stick very well to plastic even if you use an adhesion promotor. Though a putty would sand even easier...but not meant to be real thick.

Use some SEM (or similar) Problem Plastic Repair. Can get it or similar at an auto body supply shop. It is made to bond dissimilar plastics of unknown compositions.
 
EVA shaped with heat gun, then glued to the horn and a wood plate for the speaker ?

EVA foam from yoga carpets is cheap and can be found in several density easily ?!

There are also a lot of foam tubes for isolation in many several diameters ?!

Good enough for a band path shape for the mids ?
 
On the SEOS15, at least, just scratching up the horn's outside surface with a rough file or rasp gave it good adhesion to the epoxy putty. On earlier ones I did, I also drilled shallow holes into the plastic before adding the epoxy (the walls on the SEOS15 are about 0.35" -- 0.9cm -- thick). I haven't tried prying off the epoxy, but accidentally dropping one of the horns on the floor didn't break the connection between mounting plate and horn. Probably if I were making speakers commercially or for mobile PA work I'd look into something more secure, but for home use I have no fear at all about the bond coming loose.
 
I tried fiberglass.
It works for 6.5 woofers, but for 4" perhaps, its too risky.
The cone is too tiny, not gonna to survive the processes.
 

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Possible, but everything would be different (different design) though. On the sides, ports at the same distance from the tweeter would be further out the horn from the center, because of different wall angles. Mounting would be a lot tougher to do, too, as there is less surface area to work with.

And locating mids on the side would mess up the placement of the woofers (which are using volume behind the sides of horn), and so I couldn't do the extension of directivity to lower frequencies, which is the main reason for having the midranges in the first place (in this design). A midrange isn't needed to use the full 'natural' directivity of the SEOS15 (down to about 800Hz), there are a number of tweeter drivers that can drive it that low. But a midrange is needed to blend down into the low 100's of Hz for horizontal directivity management with the woofers, and also to allow crossover to woofers at a low enough frequency to keep the vertical directivity in a single lobe.
 
Of course there's always paper mache.
Or a product called "sKratch".

https://skratchworks.com/

I heard about the stuff just before moving from Madrid New Mexico, where the inventor of sKratch lives. No mixing required.

As far as Bondo, the Evercoat Tiger Hair or Bondo-hair products are the way to go for large fill, the chopped fiberglass in the mixture makes it super strong. It won't crack or break out under virtually any level of abuse, including hitting it with a hammer. The chopped fiberglass does make for a little roughness in the finish, an application of regular Bondo over it can sanded to a mirror smooth surface is desired.

Art
 
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Well, I got a chance to fire up the new (but very old) table saw and cut up some plywood for the new ported version build. I took a picture of all the pieces from the 'first cuts' on these for eventual step-by-step build plans for that build as well as the sealed versions I'm listening to now. Gonna wait till I get these new ones going first, so I can get better pictures and debug all the errors before 'publishing'.

I'm now running a Linkwitz Transform, plus some room peak taming parametric notches on the sealed SmallSyns, and I do have to wonder whether the ported versions are really worth doing. I'm rather amazed by the bass these little pairs of 6"ers can do with an LT. Being designed and tuned for use up against a wall does give maybe a 6dB advantage right out of the starting gate, so I guess I shouldn't be too surprised. I'm actually wondering whether the ported box will do as well, as these are giving output down to the 30s and the ported box won't be able to be pushed as low. With porting, though, that version should have the woofers in a more comfortable zone for where most of the bass usually is. But I'm still surprised by how well the combo of against-wall mounting and the LT works. Last time I used LT, I wasn't all that impressed, but different speakers and not pro types then, either.

The appearance of the new ones should suit my tastes, though. When the grilles are off, the ports on the box will look a little like half an Onken.
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Going well so far (till I discover what inevitable screwups I may have made on dimensions!), but now the temp is up to 100F again. So I'll have to wait till things cool down again here before any more outdoor wood work.
 

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Durham's "Rock Hard Water Putty" (Durham's Rock Hard DU-1 1 lb. Water Putty-1#CAN - The Home Depot) is only a few bucks and I think would do fine, too.

Well, I got a chance to fire up the new (but very old) table saw and cut up some plywood for the new ported version build. I took a picture of all the pieces from the 'first cuts' on these for eventual step-by-step build plans for that build as well as the sealed versions I'm listening to now. Gonna wait till I get these new ones going first, so I can get better pictures and debug all the errors before 'publishing'.

Going well so far (till I discover what inevitable screwups I may have made on dimensions!), but now the temp is up to 100F again. So I'll have to wait till things cool down again here before any more outdoor wood work.
Bill,

Everything looks great with your new project so far!

I found my big can of Durham's just after purchasing another. One good thing about moving is the shop is now set up and ergonomically organized, instead of 19 years of adding stuff here and there.

After purchasing a new (used) Craftsman table saw, I realize now that the Delta table saw I'd been using for the last two decades was a piece of junk.

With a movie screen reflecting 95% of the sun, and four fans focused on where I am working, 100 degrees won't keep me out of the shop, though getting used to high humidity again after two decades in the high desert took a while. Helps that there is about twice the oxygen here in DeLand as in Madrid.

Unlocking, locking, and putting a tarp over the workbench and table saw is a pain, I don't like to start working unless I have some time to do it.

Of course, when one is not gainfully employed, finding time is not too hard ;^).

Art
 

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Thanks Art.

Weather was great yesterday, so I spent much of it "tuning up" my new (but ancient) contractor's table saw. I had noticed the longer boards pulling left a little when I cut the pieces the other day, so read up about it on the net. Tuns out the blade was a little out of parallel with the miter slots on the table, and I found the adjustment "procedure" online for it (an old Rockwell Model 10 with a 40" table extension). The adjustment was a simple matter of slightly loosening 4 nearly-inaccessible bolts and banging the crap out of one side of the mechanism with a hammer and block of wood until everything came parallel again, then retightening.

Of course I did all this AFTER having cut all my boards, but now if I make yet another badly-needed set of speakers :confused: I'll be all set! It cuts like a dream, now, noticeably smoother.

Maybe today after the ton of chores I promised my wife I'd do, I'll get out and start jig sawing the baffle pieces.
 
aaand.... as I'm waiting for glue to dry on the new cabinets, I browse over to the TechTalk site and find that the tweeter I'm using is apparently being discontinued! The vendor has it on Clearance (Peerless by Tymphany DFM-2535R00-08 1" Compression Horn Driver 2/4-Bolt 8 Ohm).

Way to kill a design, there, Tymphany. Guess I won't need to do a full build guide on this after all.

:(:(:(:(:(:(:(:(
 
Where (link)? I couldn't find it, just a "DLM-2525R00", which is much different.

edit: oh, I found it. It wasn't there an hour ago, I swear! They even have a 60W version of the DFM. So, maybe it's only PE that is going to stop carrying it?

edit again: it depends on how you search, apparently. If you search with http://www.tymphany.com/pro/ and ask for 'all compression drivers', or search under 'DFM', it isn't there.
 
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