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Old 19th June 2004, 09:30 PM   #11
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Quote:
Originally posted by planet10


We don't expect you to do that... we expect you to enjoy them. But with Locust 0.5 & 1.0, how far away can Locust 2.0 be?

dave
That is in the hands of United Parsel Service.
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Old 19th June 2004, 10:24 PM   #12
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Quote:
Originally posted by Dave Jones
Well, I'm not going to throw them away.

Quote:
Originally posted by planet10


We don't expect you to do that... we expect you to enjoy them. But with Locust 0.5 & 1.0, how far away can Locust 2.0 be?

dave
I would never throw anything away am a horder!
Chip board is a good material but when i lived in Ghana i notice that Chip board boxes can sound different in humid climates?

I hear people say they paint the inside of there plywood or varnish it, i think that is a better idea for chip board, i have never pressure tested a box, only intercoolers, I know David likes his Ply boxes, ask him for a treatment if you want to do something to make them last forever.
But i like the design it looks solid.


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Old 19th June 2004, 10:48 PM   #13
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Quote:
Originally posted by Paradise_Ice
Chip board is a good material
I never did mention that there are some claiming chipboard is actually better sounding than MDF... the big advantages of MDF are that it is relatively cheap (in my case it is usually free) and holds a machined corner.

dave
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Old 19th June 2004, 11:00 PM   #14
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Quote:
Originally posted by planet10


I never did mention that there are some claiming chipboard is actually better sounding than MDF... the big advantages of MDF are that it is relatively cheap (in my case it is usually free) and holds a machined corner.

dave
Yes your right, but you want to talk edges?
look at this
http://www.hiddenspeakers.com/product/149

This is just amazing, i have not heard this design but its so dame clever, i wish i had though of it

I know Steve Margolis would be interested in this design.

Has anybody in this forum used Glass for an enclosure?
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Old 20th June 2004, 02:57 AM   #15
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Ok, since efficiency isn't an issue, here's my suggestion for Locust 2.0.

Using 1/2" no-void plywood:

L = 34.3125"

SO/SL = 32.752 in^2

vent = 1.625" dia. = ~45Hz F6

driver down 12.125"

~5 ohms series R

GM
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Old 20th June 2004, 04:10 AM   #16
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Update: Just when I think it can't get any better, it gets better.

For a while I thought I had damaged the drivers by applying dammar varnish and paint. I A/B'd them vs. an original set. Although the varnished ones sounded very smooth, they were noticeably less bright than the pristine drivers. (It may be significant that the new drivers had not been broken in.) I decided to add a cap to the BSC circuit, turning it into a baffle-step and treble correction circuit (BSATC?). I tried a 2.2 uF. There was a dip in the upper midrange. I could see it plainly in the output of SpeakerWorkshop. I changed the cap to 4.7 uF. I thought that did the trick. But last night, I got a case of listener fatigue. There was now a narrow peak in lower treble.

So today I tried 3 uF caps. WOOHOO! The "air" is still there, but the nasty edge is 100% gone. Now I've really got the bug. I'm dreaming of Lowthers. I mean, how good can it get?

So the recipe is, 3 very light coats of of artists' dammar varnish, followed by one light coat of artists' ivory black paint with dammar varnish. Actually, if I did it again, I think I would mix up some banana-paper color paint. The response correction circuit is below.
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File Type: jpg bsc.jpg (41.5 KB, 687 views)
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Old 20th June 2004, 04:12 AM   #17
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Quote:
Originally posted by GM
Ok, since efficiency isn't an issue, here's my suggestion for Locust 2.0.

Using 1/2" no-void plywood:

L = 34.3125"

SO/SL = 32.752 in^2

vent = 1.625" dia. = ~45Hz F6

driver down 12.125"

~5 ohms series R

GM

Thanks again GM. (GM essentially designed Locust 0.5.) How long is the port?
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Old 20th June 2004, 04:59 AM   #18
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You're welcome!

1/2", hence the 1/2" material thickness requirement. I normally spec 3/4" min., but between the vent getting so big and this driver's modest output I figured if it wasn't stiff enough you could glue in a dowel or two.

Like Dave p10 though, I believe once you use a good grade of plywood such as Baltic Birch, you won't go back to the various flavors of chip/particle board, at least for wide BW drivers, pipes, horns, etc..

BTW, why didn't you parallel the bypass cap around all the resistance?

You've got a nice little system, but it gets soooo much better......

GM
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Old 20th June 2004, 05:01 AM   #19
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Quote:
Originally posted by Dave Jones



Thanks again GM. (GM essentially designed Locust 0.5.) How long is the port?
Of course, I could not wait for the answer to start fooling around with it. I put the numbers into Martin's software, and messed with the port length until I had a tuning around 40-45 Hz. (Does 1.75" sound about right.)

While the F6 is technically around where you said, the response starts falling off at about 400 Hz, which is roughly where the BSC kicks in. I think if I upped the resistance in that circuit, I could get the response danged near flat all the way down to 30Hz. Wouldn't that be impressive to get that kind of bass out of 4" drivers? And with all that added resistance, I could probably turn the amp (Rotel RA-02) up to about half way. That would make it easier to adjust the volume. Here's a picture of the frequency response. What do you think? Would the poor little drivers hop out of their moorings?
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Old 20th June 2004, 03:29 PM   #20
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I always calc the 'new' Qes and input it and the increased Re to see the theoretical half space FR, so assuming published specs, change Re/Qes to 12.6 ohms/0.746, rp = 0.812", Lp = 0.5" to see what I simmed.

If using measured specs, then calc your own Qes' and adjust Re, vent as required:

Qes' = Qes*(1+Rs/Rvc), where Rs is the series
resistance and Rvc is the driver's DC resistance, so:

Rs = (Qes'/Qes-1)*Rvc. Remember to include the series
resistances of your amplifier/cable/inductors in Rs,
so the actual resistor you buy may be somewhat
smaller than calculated value.

Qts' = Qes'*Qms/(Qes'+Qms)

Vas is unchanged

n0 = 9.6352*10^-10*Fs^3*Vas(liters)/Qes'

SPL = 112.018+10*Log(n0)

WRT to tuning below 0.707*Fs, I've found this a performance point of rapidly diminishing returns, so don't recommend it, but may be acceptable in your app, so nothing ventured, nothing gained.

GM
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