Roland full range with paper/cardboard gasket on flange - diyAudio
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Old 16th April 2011, 03:57 PM   #1
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Location: Appleton, WI
Default Roland full range with paper/cardboard gasket on flange

I have been experimenting with some Roland 7.5- 8 in. drivers which I got on ebay as remainders from production of one of the Roland pianos. They are bigger from what I normally have built for full range.

I had a question about the paper gasket around the mounting flange which looks similar to the rear mounts in auto speaker installations.

The question is: Should this cardboard gasket be removed for more direct mounting and how, if any, does it effect the resulting sound? No doubt the Roland was mounted down in the works of the electric piano somewhere.

As I consider a rear mount on the baffle, I'm wondering if I should perform surgery on the Roland for dispersion or other factors.


Zene at full range driver forum was kind enough to find the T/s params for these units reposted here in a message from GM:

Zene posted these specs back then, so OB or leaky box are the obvious choices:

Roland 8" is/are: (Used Peak Inst. for test, only broke-in 12 hrs.)

Paper cone
Fs = 78.76 hz
Vas = 24.5 L/0.8652 cu ft
Re = 7.309
Le = .2462 mh
Qms = 5.772
Qes = 1.977
Qts = 1.473
Sd = 21.4 sq cm/3.317 sq in
BL = 0.4477 N/A (calc'd)
Spl 89.65 1w/1m
Pe = 30W

GM

ref:

Some research is needed (Page 1) / FullRangeDriver Forum / Fullrangedriver Forum
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Old 16th April 2011, 04:46 PM   #2
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Greets!

Ages ago I posted about tweaking 'el cheapo' drivers in general which included trimming the gaskets flush with the metal frame, tapering them in towards the diaphragm if fairly easily done with the tools/skills at hand and recessing the drivers as flush as practical by adding a 'skin' to the baffle to keep hole cutting simple. That, or at least installing an open cell foam or felt ring to lap over all this and the surrounding baffle if one didn't want to modify the drivers.

IIRC though, Dave p10 one upped me by saying he got rid of the gaskets altogether and pounded the metal frame flat. Seems like that might misalign a VC even after epoxying the motor to the frame and damping it first due to how flimsy so many frames are, so if I were to do it, I'd use a Dremel or similar tool to cut some notches flatten it as much as practical with a vice before doing any hammer finishing work.

Some form of gasket with the right physical properties is required to mount drivers to damp down its symphathic resonances that will otherwise comb filter with either its or another driver's HF, so the choice is always a trade-off between too much or too little electro-mechanical-acoustical efficiency. 'El cheapos' tend to err on the side of too much since the gaskets are cheaper and power handling usually is quite low, so it's the 'no-brainer' choice for a manufacturer.

For rear of baffle mounting then, the paper gaskets generally don't seal all that well in my experience, so adding a bit of flexible sealer between gasket joints and smearing on its face some wheel bearing grease or similar that won't dissipate out around it or be absorbed by it at worst case room temp is what I've done.

GM
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Old 16th April 2011, 05:38 PM   #3
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Greg,

Your tips are always top shelf. Since I have two of these, on Enabl'ed *and* phase plugged with a plug I fashioned from a wooden Easter egg (sold in craft stores) I would continue modifying the one, while leaving the untreated one with which to compare.

The Enabl job on the Roland is the best one I've ever accomplished with Ed's kit. But the El Cheapo I think needs or can handle more brute force modification. I always blanch at doing any of this surgery.

And I do use your tips even if not right away or on the unit mentioned. ;-) The box for this Roland was salvaged from another build and has that thin layer of hardboard used on the face as a rabbet. If the paper gasket is removed the unit will be tight and nearly flush.

Future home of the Roland may be a Karlson. I have recently built a Karlson for the FE167e because the design is interesting. This took quite a while and is the reason I have not had a lot of posts here. It was tough to do all the angles with small tools and not have it come out looking like a building by Frank Gehry.
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