Curt Campbell's Halcyon build thread


2018-04-30 5:08 am
Revisiting my Halcyons to see what more I can squeeze out of them. Re-read everything here and decided the easiest was revisiting the stuffing as I didn't spend much time teasing it. Here's the after/before picture. 12 oz. in each pile but the left is the post-teasing and the right is the pre-teasing. I've got one speaker done and planning to finish the other speaker tomorrow.


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2018-04-30 5:08 am
the fumble ending their 2nd possession coupled with walking into halftime with no points after the interception really changed the tone of the game. I thought the Packers would go all the way this year but that's why they play playoff games.

Hoping tomorrow to see if I can actually hear a difference in the bass. Attempting to make this more of a journey than an end, learn a few things more along the way.


2018-04-30 5:08 am
possibly. I decided to revisit the stuffing in an attempt to experiment and find improvement. Re-reading the thread, dave pointed out that acoustuff needs some work to behave like polyfil (the fill utilized by Mr. Campbell). As cheap as polyfil is, I didn't feel like wasting what I had on hand so I pulled it and teased it.

I added another 6 oz. to the main chamber on the left speaker and still need to mirror on the right speaker. I've got a weird resonance on double bass in one recording that I'm attempting to determine if it is the tuning or a problem with the recording.

But, yes, after teasing, I've removed a couple of pounds and have found the bass to still have goodness.
Good day, everyone ... new to this thread, so I hope you all don't mind me jumping in. After reading all I could find about this design, I've decided to build a pair. I am planning to build the cabinets myself, and not use a flat pack. I have built 4 sets of speakers so far, all from scratch. The first build were Frugelhorns, the second was a pair of Super Pensils (see attachment), the third was a pair of Decware ZOBs (didn't like them at all) and the fourth (and my current speakers) are a pair of big *** folded open baffles, with 15" drivers and SEOS horns with Radian drivers (101dB and they are awesome). Pic below (the horn cabs were built after the bottom cabinets ... they started out as a coaxial design):


Anyway, I'll probably build the cabinets out of Baltic birch (maybe MDF since I plan to paint them) and the baffles out of Oak, Maple or some other hardwood. I couldn't find a cut list anywhere, so I made my own based on the plans on Curt's site. What I came up with is:

(2) 22.5" x 34.25" (sides)
(2) 9" x 34.25" (front/back)
(2) 4" x 21" (base)
(2) 4" x 8.5" (base)
(1) 7" x 8" (brace behind the port)
(2) 8" x 16" (braces in the transmission line above/below the port
(1) 8" x 21" (brace under the Sonotube)

Can anyone confirm that looks correct, or if I'm missing anything? Also, I have a couple questions. I assume 3/4" stock is appropriate? And is there any reason to have a double thickness baffle (like Curt's original set had)? I'm actually considering making the baffles out of 1" or 1 1/2" maple butcher block anyway, but was curious if the baffle thickness makes a difference at all. Do the driver cutouts need to be rounded (front and/or back)? I see that the drivers should fit flush to the face of the baffle ... that's not an issue. Should the opening behind the Sonotube be rounded?

I see that the Mark Audio 10p drivers are backordered until April, so I thought I'd at least get started on the cabinets and get those all done in advance. My plan is to paint the cabinets blue and clear coat the base and baffle. I want to emulate the look of the speakers below.

Screenshot 2022-02-17 113427.jpg

I look forward to the build, and hope I can get support from this group as questions come up. Thanks!



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I never heard of the Travelers until today. They look nice. I'd love to see a comparison between them and the Philharmonic BMR.
Meniscus has the parts and Leland has flat packs. Cost is a little higher for the BMR, but having flat pack available would be the clincher for me, unless our buddy Bob Berner at could be talked into making some.


2018-04-30 5:08 am
I seemed to have settled on 12 oz of acouta-stuff. in each of the lines behind the woofers and 6 oz. in the main chamber. I haven't tried stuffing more in the main chamber but seems to have cured the odd bass resonance on a couple recordings and the bass seems to be "just right", still defined, deep and satisfying.
Cross over look good davebtw.

How's the front baffle coming along?

Since my last post my woodworker friend came down with a very bad case of COVID, ended up in the hospital with lung blood clots, and been on oxygen since coming home. I just visited him and today he is gluing the front baffles on the boxes today. Then we will fill behind with wood epoxy and taper as possible from there. He was very sick and I am just glad he recovered and is healthy again.

So, I really appreciate the comments from you all, and especially 6sX7 for his insight into the stuffing. I will be teasing a lot more than I originally did and start with his amounts once things are finished. I still expect it will be several weeks more before I can mount drivers, but at least we are underway again.

I am still in Quarantine due to my kidney transplant, but still there is some light at the end of the tunnel.

-david BTW
Thanks zman01! I have successfully quarantined and avoided picking up COVID for just a week short of 2 years. One of my anti-rejection drugs actually cancels out the vaccines. I have had 2 Pfizer and a booster, and my hospital measured what should be antibodies and my results were "undetectable' in the last test. So I am super vulnerable. But i am working full -time and doing OK, and most anxious to get these Halcyons in my home.

I just got text from my neighbor. He has the fronts on and has put in the expoy fill and we are now awaiting the cure. We then will be rounding off the front baffle edges and preparing for a finish on the devices, so that is good news.

Again, thanks for the help and concern.

-david BTW