The dome midrange thread

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#101
Okay thanks for info ... anyone who's interested can buy here this stuff for elonged UV-exposed testing on your window board :

https://lautsprecher-technik.com/La...102mm-Lautsprecher-Reparatur-Gummi-Sicke.html

Translated :

https://lautsprecher--technik-com.t..._sl=de&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=wapp

Maybe EPDM is better than the (black) foamed stuff we know as computer mouse pads! (deteriorates after a few years of mechanical stress)

Btw - I am still asking myself what happens to foamed products if transported in near- vacuum condition? (send by air plane in very elevated heights)

Thinking of Zellaton speakers (foamed cones) :

https://www.zellaton.de/en/making-a-statement.html
 
#104
tktran303 said:
So what kind of back cup or enclosure does the D7608-9200 need for operation from ~400Hz?

Woofer sensitivity is usually the limiting factor; most of the time midranges or tweeters need padding down
Click to expand...
A 1 litre chamber with light wool stuffing and more flow restriction right behind the magnet will extend it down to 500 hz with a Qts of around 0.8 or so. You could get it down to around 450 hz with a larger chamber and less dampened rolloff, but the low 1mm P-P xmax means decreased SPL potential, plus THD will be unacceptably higher IMO. Many people like to use HP filter peaking to get more output sensitivity after the xover is applied. This isn't a good idea IMO, as it will raise odd order HD and worsen transient response considerably.

A good solution is to add a second dome in MMT config running staggered LP filters so you could get away with a 500 hz HP 3rd order and have decent max output capability. The felt SS added on back of the D7608 magnet vents isn't nearly enough to lower Qts sufficiently in a larger chamber. This is what hurts the dome's potential when used in off the shelf configuration. It raises HD too much and completely ruins transient response.

In general, Qts on the D7608 should be lower then 0.9 to have better control of the diaphragm at resonance, otherwise odd order HD is too high. You can lower Qts to 0.75 with enough flow restriction, but you won't have enough output at rolloff to get to an acceptable balance between SPL potential and lower HD.
 
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#105
Red before modification and blue after modifications. The absolute SPL is not calibrated and the measurements are very influenced by the room.
1704196941731.png
 
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#108
motokok said:
Does anyone have experience with the Visaton G50FFL or DSM 50FFL domes?

Or indeed the nifty AK 10.13 cup for the D7608, perhaps?
Click to expand...
For anyone interested in the magnet OD of the D7608, its 3.591" (91.2mm). A chamber can be attached to the magnet OD but can't be wider in OD than the baffle cutout (kind of obvious).

The exact baffle cutout size for mounting the driver is 4.300" (109.2mm). You can use a back chamber with a min opening of the baffle cutout diameter, but you'll need to make a small notch cutout in both to make room for the terminals, measuring 1.050" x .200" (26.7mm x 5.1mm).

I recommend a baffle rear mounted chamber of at least 4.500" (114.3mm). You can use rockwool, fiberglass or denim cotton as dampening material. Do not over stuff the chamber as this will go backwards, actually raising Fs, reducing chamber volume and sucking out all the lower mids. The places needing dampening are right up against behind the magnet and walls of the chamber. You may need to experiment a little to get the flattest low end possible.
 
#115
Lojzek said:
D76af has a defined Qts (factory sealed system) as manufacturer saw fit, so any response changes you might be able to
introduce are the ones coming from filter network. I have a D52af, and it is one happy chap of a driver, robust for sure.
Click to expand...
thankyou . I was thinking of atc style hornloading . also wondered about high pass frequencies etc
daanve said:
To do what?
Datasheet says Qts is 0.9, so not much to gain.
Click to expand...
same as above
 
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#117
 
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