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Curt Campbell's Halcyon build thread
Curt Campbell's Halcyon build thread
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Old 6th February 2020, 11:22 PM   #1
alanhuth is offline alanhuth  United States
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Default Curt Campbell's Halcyon build thread

This thread will follow my build of the Halcyon speakers, designed by Curt Campbell. I'm not sure if this is technically a F.A.S.T design, but I think it is. There is a single Alpair 10p and two SB Acoustics SB17 midwoofers. Curt described the design: "The Alpair is housed in a semi open back cylindrical enclosure, while the SB17's perform in individual transmission lines that are merged at the port in a mass loaded configuration"

Curt shared that one of his friends, a professional opera singer, preferred the Halcyon's to any of his other higher-end designs. This raises my already high expectations that this is going to be a fine speaker indeed. Strangely, other than Curt and Jim Holtz, I don't know of anybody who has heard them and I don't know how many pairs have been built. Madisound says they have sold several kits, but I haven't been able to find a build thread or any pictures of completed Halcyons other than the original test mules.

Bob Berner (bob@bigwoodstudio.net) made a terrific flat pack for the Halcyons. Everything fits perfectly and the BB plywood is very high quality. Bob is very helpful and prompt. From idea to delivery for a brand new design with no CAD drawings, Bob completed the whole process in just a few weeks. He is great to work with (he also built a FruglHorn XL kit for me) and I encourage anybody interested in a flat pack to contact him. He has good prices, great service, and a very supportive approach.

Here is Curt's website section on the Halcyons:

Speaker Design Works

This is the the only finished Halcyon I have seen images of:

Halcyon Curt Finished.jpeg

Last edited by alanhuth; 6th February 2020 at 11:40 PM.
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Old 6th February 2020, 11:37 PM   #2
alanhuth is offline alanhuth  United States
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Here is the initial tape-up, just checking for fit and finish. Everything fit perfectly first try.

Halcyon AHH tape up.jpg
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Old 6th February 2020, 11:38 PM   #3
wesayso is offline wesayso  Netherlands
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Is the baffle upside down? I expect the smaller hole to be the port in this mock up...
Use Science to design your speakers and they will sound like a piece of Art...
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Old 6th February 2020, 11:43 PM   #4
alanhuth is offline alanhuth  United States
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How embarrassing. Yes, you're right. Still fit perfectly. Good thing I didn't glue it. I guess I got a little excited.
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Old 20th February 2020, 11:52 PM   #5
alanhuth is offline alanhuth  United States
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Real glue this time:

Halcyon glued.jpg
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Old 2nd March 2020, 02:17 AM   #6
alanhuth is offline alanhuth  United States
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Default Major league rookie mistake - advice needed!

Well, I finally got away from work and back to the fun of building speakers, and first thing i do, I glue the inner baffle on backwards. Itís glued in pretty tight, attached to no less than 6 other boards. And itís backwards. I went to some trouble to make sure to get the baffle beveled properly and then I glued it in with the bevels on the outside. Jeez. Luckily, I guess, this is the inner baffle and there is an outer baffle to which the speakers will be attached.

Advice needed. What is best remedy? I can think of 3 options:

1. Ignore it and just proceed finishing the speakers.
2. Get a router bit and chamfer the remaining wood the other direction, then fill in the gap with Bondo and try to re-create the proper bevel.
3. Cut the baffle out and get another one.

Any other options and recommendations?
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Old 2nd March 2020, 03:41 AM   #7
AllenB is offline AllenB  Australia
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Curt Campbell's Halcyon build thread
It shouldn't be a problem, I would consider opening it out to a plain cutout. The original purpose of the chamfer isn't so much about reflections, even though it looks that way. It's more about giving the strength of a thick baffle without crowding the rear of the cone.
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Old 2nd March 2020, 08:31 AM   #8
TMM is offline TMM  Australia
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If it were me: cut it out and make another one. I would probably remove the bulk of the material with a jigsaw, then use a router with some guides/jigs to clean up the glued parts.

I can think of a few other ways of solving the problem but they are all more work than that.
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Old 2nd March 2020, 11:49 AM   #9
bobberner is offline bobberner  United States
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It doesn't really matter. According to Curt Campbell the inner baffle is probably not needed due to the stiffness of the 18mm BB ply. I can certainly make you a new baffle if you want to replace it. If looking at it thru the speaker cutouts bothers you, you could simply remove the bevel on the holes with a jigsaw. The bevels are there to give the drivers breathing room. Removing them would preserve this.

No one will ever see this mistake once you finish the speakers. And of course we will never say a word of this to anyone.

To reiterate. It won't matter. Personally, I would just trim the bevels off with a jigsaw, and install the other baffle correctly.

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Old 2nd March 2020, 03:27 PM   #10
system7 is offline system7  United Kingdom
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Ew, a bit of a goof! TBH, I have had enough disasters of this like...

Click the image to open in full size.

Now you COULD fit the drivers to the inside of the inverted baffle. And I don't suppose it would sound much different. But access then becomes a severe problem. Maybe a screw -on side panel would give you some leeway here. Once you glue it, there is no access at all.

So it's unmaintainable. Bob Berner sounds like a top-notch guy with his routing skills. What do you think, Bob, about making a couple of extra front baffles?

Speaker Design Works

It's either that or a new cabinet, IMO. Gonna cost you, either way. In engineering terms it's a bit like building a Spitfire Fighter, and glueing the wings on upside down. Sorry.
Best Regards from Steve in Portsmouth, UK.
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