Midrange dome drivers banned ?

[Mnyb]

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

 

[jhaider]

What gives you the idea the dispersion is bad?

FWIW, my experience with the bigger Dunlavys (SC-IV I believe) was that they had possibly the smallest sweet spot of any speaker I’ve yet heard. So strange to have coffin sized boxes and have things fall apart if you stretch your neck.

While I haven’t seen measurements, but to me that says focus on things than even off-axis response in the design.

 

[Tim Link]

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!

 

[Penelinfi]

Holes in the dome may affect the structural integrity and increase resonances etc

 

[Tim Link]

Holes in the dome may affect the structural integrity and increase resonances etc

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.

 

[mhardy6647]

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 drivers' domes.
The actual reason why it was done is unclear at this late date. Chatter on the Polk Audio forums and elsewhere has identified a number of possible explanations*, but there's no confirmation of any of them from Polk of which I am aware.

A very early Monitor Series Model 10 (ca. 1975 or '76) with stock Peerless (KO10DT) tweeter, sans hole.



A somewhat later (1971) Monitor Series Model 7A with a sanctified holy wholly holey Peerless tweeter




close-up:

_________________
* 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?!).

 

[Tim Link]

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

_________________
* 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?!).

Well how about that! Thanks for sharing. Maybe I won't ruin a dome if I drill a small hole in it.

 

[mhardy6647]

Well how about that! Thanks for sharing. Maybe I won't ruin a dome if I drill a small hole in it.

Dude!
No warranty, express or implied!

Maybe you won't.... but it ain't on me!
If you bjork bork a dome driver -- Write a sternly worded letter to Matt Polk, not to me!
He's (still) on LinkedIn.

 

[Ktacos]

Sounds like a good way to just ruin a nice dome mid.

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!

Multi entry horn is a totally different beast to what you're talking about.

 

[dualazmak]

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.

 

[mhardy6647]

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.

good call(s).

 

[dualazmak]

Sorry to be a little bit out of the scope of this thread, but just for your possible interest and reference...

Not for dome midranges, and not for dome tweeters, but for narrow-directivity highly-efficient metal-horn super-tweeters (FOSTEX T925A), I did rather intensive experiments on wide-3D reflective dispersion of high-Fq sound using hard-heavy random-cut-surface-crystal-glass surface; as the result, I decided to implement/apply one of such wide-3D reflective dispersion settings in my multichannel multi-amplifier active audio setup.

Spoiler

- A new series of audio experiments on reflective wide-3D dispersion of super-tweeter sound using random-surface hard-heavy material:
Part-1_ Background, experimental settings, initial preliminary listening tests: #912
Part-2_ Comparison of catalogue specifications of metal horn super-tweeter (ST) FOSTEX T925A and YAMAHA Beryllium dome tweeter (TW) JA-0513; start of intensive listening sessions with wide-3D reflective dispersion of ST sound: #921
Part-3_ Listening evaluation of sound stage (sound image) using excellent-recording-quality lute duet tracks: #926
Part-3.1_ Listening evaluation of sound stage (sound image) using excellent-recording-quality jazz trio album: #927
Part-4_Provisional conclusion to use Case-2 reverse reflective dispersion setting in default daily music listening: #929

- The latest system setup of my DSP-based multichannel multi-SP-driver multi-amplifier fully active audio rig, including updated startup/ignition sequences and shutdown sequences: as of June 26, 2024: #931

 

[witwald]

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!

@Tim Link Would you be able to show us a measurement or two? That might help visualize what's going on with the response.

 

[Tim Link]

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 would never drill that either!

 

[Tim Link]

@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 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]

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.

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.

 

[Penelinfi]

Holes in diaphragms have been done; notably in older speakers where woofers had a hole dust cap for venting I assume. Some tweeters have small hole in the middle of the dome; - maybe unknown to many people here, but those little "balanced dome" mylar tweeters often have a small hole. Might be pressure equalisation though.
I don't recall seeing any in a metal dome however. Maybe the edges resonate, or it induces cracking at high volume. I've seen shattered metal dome before and wonder just how they managed that...

 

[jamescarter1982]

has there ever been a ring radiator midrange driver or a larger version of that sb dome tweeter with the dimple in the middle

 

[Doenerkunde]

has there ever been a ring radiator midrange driver

Yes, midranges of coaxial compression drivers:

 

[Penelinfi]

Elac FS 509
Thiel maybe
Technics with their flat ring coaxial
I may have seen another somewhere but forgot the speaker