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Old 19th June 2004, 03:00 AM   #1
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Default The Locust I

I've made another tower (ML TL) using the Fostex FE107E. This one sounds even better than the other one.

The first version ("Locust 0.5") had an ID height of 15 1/4". Playing around with Martin's MathCad worksheet, I determined that I could get the F6 down to 60 Hz by stretching it to 19 1/2". The mid bass was just a tad lower (1 or 2 decibels), but I reckoned that the BSC circuit could pull that up a little. For the intended purpose, I do not need much efficiency.

Your mileage may vary, because I had already varnished the speaker cones. That pulled the treble down. I was able to correct that by putting a 4.7 uF cap across the 4 ohm resistor in the BSC circuit. (See attached picture.) SpeakerWorkshop now shows that I've got pretty darned flat response all the way up, but with a wrinkle in the 10K-20K range. I've got the sub crossed over at about 63 Hz. On many recordings, it is not missed at all when I mute it.

The whole thing is made from 3/4" MDF. The port is simply a 1" hole in the front panel, about an inch from the bottom (ID). Because of that, the front panel has to be 3/4" stock to make the port the right length. Construction could hardly be any simpler. All the side pieces are identical except for the holes. Six pieces are required per speaker:

4 pieces 5 1/2" X 21"
2 pieces 5 1/2" X 4"

The top 2/3 or so is stuffed very lightly with poly fiber. I used a Madisound input cup on the back, GB-CUP ($2.05 each). The inductor is Shoe-Gooed to the bottom. I glued the resistors and the cap to the input cup, to make it easy to change them if I decide to. The top half of the box is lined on three sides and top with 1/4" felt.

Total cost is about $50 US per speaker.
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Old 19th June 2004, 03:05 AM   #2
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Picture attached.

Speak to me! I'm excited about this.
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Old 19th June 2004, 07:30 AM   #3
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black varnish?

And that is MDF? Here we'd call that particle board... you should try a set in 1/2" ply.

I'll be interested on your take on what the phase plugs do...

dave
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Old 19th June 2004, 07:38 AM   #4
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Quote:
Originally posted by planet10
black varnish?

And that is MDF? Here we'd call that particle board... you should try a set in 1/2" ply.

Dammar varnish, with a final coat of ivory black artists' paint and dammar varnish. Seemed like a good idea at the time. MDF stands for medium density fiber board, which is particle board. Half inch ply wood? Why? I will seal and paint these when I get a round tuit. The port is supposed to be 3/4" long, and in this design it's just a hole in the front panel.


Quote:
I'll be interested on your take on what the phase plugs do...

dave
I'll be interested to see if they ever get here. :-)
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Old 19th June 2004, 08:14 AM   #5
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Quote:
Originally posted by Dave Jones
MDF stands for medium density fiber board, which is particle board
Doesn't look like any MDF i've seen, LDF maybe.


Quote:
Half inch ply wood? Why?
I'm pretty sure they will sound better

Quote:
I'll be interested to see if they ever get here.
The post hasn't lost anything on me in the last 2 years (sample size >5000)

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Old 19th June 2004, 09:24 AM   #6
sreten is offline sreten  United Kingdom
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The cabinets are made from chipboard which is not MDF.

Its made from wood chips, not wood pulp fibre like MDF.

Chipboard comes in various densities, and has variable density
itself, the surface layer being finer chips than the larger core.

Flooring grade chipboard is heavy, dense and strong, its also
pretty hard on tool edges that cut or shape it, due to the
random alignment of some very hard wood chips, whats
left from the knots in the chipped wood I presume.

sreten.
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Old 19th June 2004, 06:02 PM   #7
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Most of the speakers boxes in the 70 and 80s were made from chip board right? very few ply and MDF whats that?LOL
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Old 19th June 2004, 06:53 PM   #8
sreten is offline sreten  United Kingdom
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Quote:
Originally posted by Paradise_Ice
Most of the speakers boxes in the 70 and 80s were made from chip board right? very few ply and MDF whats that?LOL
Its still true for nearly every folded vinyl wrap speaker.

sreten.
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Old 19th June 2004, 08:39 PM   #9
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Well, I'm not going to throw them away.
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Old 19th June 2004, 08:54 PM   #10
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Quote:
Originally posted by Dave Jones
Well, I'm not going to throw them away.
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
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