A flip side of the design is that there is displacement dual bass and dual mids , a thing missing in many speakers today with the drive towards smaller speakers that look nice but are rather gutless
What gives you the idea the dispersion is bad?
I suspect those could be serious problems. I guess if I want to know for sure, I'll just have to sacrifice a nice driver and see what happens. Or, maybe I should look for some old used domes to try this on.Holes in the dome may affect the structural integrity and increase resonances etc
Well how about that! Thanks for sharing. Maybe I won't ruin a dome if I drill a small hole in it.Re: domes and holes...
one is reminded of Matthew Polk, Sandy Grossman, and company deciding that the (fine) Peerless silk dome tweeters (not midranges, sorry -- work with me, here!) that they chose fairly early on to use in their "Monitor Series" loudspeakers needed to have a small central hole added to the doped silk dome. This was done, it is said, by deft application of a soldering iron tip to the OEM
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* Some that still pop to mind as I type this: controlling dome resonances, break up, or for pressure equalization (possibly to improve robustness to shipping?!).![]()
Dude!Well how about that! Thanks for sharing. Maybe I won't ruin a dome if I drill a small hole in it.
While nobody so far seems to be drilling holes in their domes, there are some who are drilling holes in the sides of their waveguides so they can sneak more drivers in from the sides. The goal is the same - to create a broader band of frequencies that can disperse evenly form a single point. Drilling for dispersion!
good call(s).BTW, I will definitely never-never drill on my treasure vapor-deposited Beryllium 8.8 cm dome midrange YAMAHA JA-0801 and vapor-deposited Beryllium 3 cm dome tweeter YAMAHA JA-0513 (ref. here for my latest setup). Beryllium dome is very hard and extremely fragile, and it is very much toxic when destroyed into powder.![]()
@Tim Link Would you be able to show us a measurement or two? That might help visualize what's going on with the response.I just bought a couple of Dayton 2" aluminum dome midranges and have been thinking about using them in 90 degree conical waveguides. My initial experiments are showing problems with high frequencies bouncing around, I'm assuming because the center of the dome is more efficient at creating sound than the edges. That quote from Dunlavy in an earlier post suggested that the edges create more sound than the center, but I think that only applies to a softer dome material. With the aluminum dome, I think it all moves together until about 12 kHz, where it has its first resonance peak.
A dome shape, in theory at least, could produce a spherical wave front over a wide range of frequencies, including frequencies with wavelength shorter than its diameter. Unfortunately, this would require that the dome be able to expand and contract equally across its radiating surface. Nobody knows how to make a stretchy, well behaved membrane to do that. For now we have domes that only move up and down.
So, if the dome is moving all together as a piston, it makes sense to me that the center of the dome, which is most perpendicular to the pistonic motion, is going to produce sound more efficiently than the edges. My dome appears to be sloped at about 45 degrees at its edges. How much less efficient is the displacement of a membrane at 45 degrees angle to motor motion, and what does that convert to in terms of decibels? My intuition is that the displacement is about 0.7, and the sound power is about 0.5, or minus 3 dB. Someone please feel free to correct me.
If that's basically true, even if the math is off, it would seem to me that an aluminum dome midrange could be made to create more spherical waves at higher frequencies than usual by reducing the efficiency at the center of the dome. One way to do that might be to make the membrane a little leaky towards the center, and less so at the edges. This could be done by drilling tiny holes in the aluminum at proper spacing and placement. The cost would be reduced efficiency in exchange for better dispersion. There also may be other undesirable results, which wouldn't surprise me because nobody is drilling holes in their domes as far as I know. Could air passing through those little holes make noise, distortion, and create resonances?
Thoughts? Should I drill some holes in my dome? Is there a reasonable possibility that this technique could be made to work well?
While nobody so far seems to be drilling holes in their domes, there are some who are drilling holes in the sides of their waveguides so they can sneak more drivers in from the sides. The goal is the same - to create a broader band of frequencies that can disperse evenly form a single point. Drilling for dispersion!
I would never drill that either!BTW, I will definitely never-never drill on my treasure vapor-deposited Beryllium 8.8 cm dome midrange YAMAHA JA-0801 and vapor-deposited Beryllium 3 cm dome tweeter YAMAHA JA-0513 (ref. here for my latest setup). Beryllium dome is very hard and extremely fragile, and it is very much toxic when destroyed into powder.![]()
I didn't save the measurements. What was happening was a dip in response, which seems to be a throat reflection at about 6 kHz. I should be able to recreate it. My testing just involved a sort of 2D horn with 45 degree flat beveled boards right up next to the driver. I'm figuring that if the center of the dome is a hot spot, then I've got a reflection that's late by about 1 inch or so. I can change the notch frequency by changing the angles, but I can't make it go away. I think though that if the sound power were more even across the dome then it would load evenly and the notch would go away. The reflection at 45 degrees would just be a continuation of the dome shape as a complete circle. Or simply, there'd be a circular wavefront coming out that remained perpendicular to the sides of the horn, so no reflections.@Tim Link Would you be able to show us a measurement or two? That might help visualize what's going on with the response.
I agree, it would be a pity to sacrifice such a nice driver. It's unlikely that I'd strike a great result on the first attempt, if success is even possible. Maybe I can find something used to experiment with. Or maybe there's a way to do a simulation. I suspect that if I make a single hole that's very small it won't do much at all, assuming I don't damage the driver while trying to drill it. I should start off practicing on pop cans. It'll take a tiny, sharp bit, high speed I think, and very little pressue. There's also a concern of metal dust falling inside.Sounds like a good way to just ruin a nice dome mid.
Multi entry horn is a totally different beast to what you're talking about.
has there ever been a ring radiator midrange driver