Straight 8 - the only Bottlehead speaker kit

[Doc B.]

Thanks to Glynn W for sending me scans of the old plans for the Bottlehead Straight 8. This design is owned by Bottlehead Corp., and we are granting you permission to build one copy for your own use. Anyone caught trying to sell speakers built from these plans for commercial gain should first be measured by a tailor to see what size lawsuit they wear.

http://www.bottlehead.com/straight%208/Straight8.pdf

mid woofers are MCM 55-1870
tweeters were MCM 53-325 which are no longer available.

A search through the archives will show some alternatives. One good choice is a Selenium ST324 slot loaded horn tweeter. It requires a 4.25" mounting hole. PJ has designed a crossover for that tweeter in the Climax design (use the woofer part of the version 3.0 Straight 8 crossover for the woofers). With this tweeter I dubbed the version the P8, because it works well for PA. It will handle a ton of power, we have run them with 150W amps. Though I didn't do it in my prototype, use PJ's recommended acoustical treatment from the Climax article around the tweeter.

Glynn W has some notes about his implementation of the ST324:

Unless the laws of physics change, this should be my last post about searching for a suitable crossover to exchange a Selenium ST-324 tweeter for the stock tweeter and crossover. The woofers are still using version 3.0 of the Straight 8 crossover. Initially I installed the crossover as outlined for the Climax speaker in the community section, adding an adjustable L-pad to cut the tweeter volume a bit. After deciding I liked the sound of a .56 uF capacitor (I could not find a .62 uF as called for in the Climax crossover) I removed the adjustable L-pad and found the sound clearer, but the tweeter was still too loud for my tastes. Using the formula for driver attenuation found here - http://www.diyaudioandvideo.com/Calculator/LPad/ - I purchased a slew of Mills 12W resistors and began listening. It should go without saying that I don’t claim my crossover to be “correct” – it is what I find pleasing in my system (hats off to Grainger for his motto). Also I was limited by the values of resistors available – I found the selection at Sonic Craft, an Asylum sponsor, to be the best I could find, but I didn’t try everything in .1 db steps – my changes averaged about .4 db. My final values for resistors R1 at 2.5 ohms and R2 at 18 ohms should give me a 3.2 db cut in tweeter volume. If any of you try this, please post your results.

[AudioFred]

I have been thinking about building the ART Array as a Winter Project. I was surprised to see how similar the Straight 8 and the ART seems to be. I am wondering if the Climax crossover might work in the ART?

The Climax crossover won't work. This thread is about the Bottlehead Straight 8, and I don't want to hijack it, so here's the link to a thread about the Art Array with an updated crossover designed by Pete Schumacher:
http://techtalk.parts-express.com/showthread.php?t=209376

And here's the link to a recent thread with a parts list. The parts "kit" is available from PE for about $285, which means you can build a pair for about $400 total. http://audioroundtable.com/forum/index.php?t=msg&th=12188&start=0&

[Mudhiker]

If I use my Straight 8's on my desk, should I flip them upside down so that the tweeters are still sorta at ear-level?  Otherwise they'd be up by the ceiling which would be bad I'm guessing.

[Grainger49]

No, absolutely not!  Turn them sideways with the tweeters in the center.

(What? Still no tongue-in-cheek smiley face)

[Mudhiker]

I want to bring my Straight 8's out of storage but I have a little dog now, and sometimes he scratches things.  Has anyone used the speaker grills from Parts Express?  I'm specifically looking a the 5.25" 2-piece one.  They aren't cheap, so I'd probably just do the lower 4 on each speaker at first, if they fit.  Or if someone has a solution from another source...

Thanks

Isaac Gorton
Richland, WA