Straight 8 - the original 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

[AudioFred]

I have been thinking about building the newbielink:http://fredt300b.smugmug.com/gallery/2046580/1/105115855#106644141_6xpLK-A-LB [nonactive] 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:
newbielink:http://techtalk.parts-express.com/showthread.php?t=209376 [nonactive]

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. newbielink:http://audioroundtable.com/forum/index.php?t=msg&th=12188&start=0& [nonactive]

[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

[robertod]

tried link to straight 8, page not found.  would like to update my straight 8's.  Is page available?

[morris_fl]

i have scans of the original plans that i made of my Straight 8s if anyone at Bottlehead
would like them for the forum.  (Still have my pair and they still sound great)

[2wo]

I have used 3/8 hardware cloth (chicken wire) mounted with some adhesive backed Velcro dots so it doesn't buzz. I sprayed it black to match the speakers I used it on. I have cats, for some reason they never bother my 8's, just like to sit on top...John

[Ken]

I have the complete set of 16 mid-drivers, 10" sub drivers and tweeters, all new in the box if anyone is interested.  Ordered, received and never built, for reasons that involve a long, sad story.

Located Vancouver Island, Canada.

[Paul Birkeland]

I would purchase those parts from you if you ever find yourself across the border!  I ran into my pair some years ago, and someone had hacked up the cabinets pretty badly to add some variety of ribbon tweeter or another. 

[Ken]

I would purchase those parts from you if you ever find yourself across the border!  I ran into my pair some years ago, and someone had hacked up the cabinets pretty badly to add some variety of ribbon tweeter or another.

I"m never going to use these and build the speakers.  Let me know your town and zip so I can figure out the shipping cost.  If it's not too high, I will "sell" the components to you for the cost of shipping.

[Doc B.]

The Straight 8 didn't use 10" sub drivers. Presumably those were intended for separate enclosures. The Superwhamodynes that preceded the S8s by a couple years used some inexpensive 10" drivers in bandpass subwoofer enclosures. Very, very different design. Regarding the substitution of ribbons for the original metal dome tweeters in the S8, I wouldn't necessarily have considered that a bad thing if the tweeters were good ones and the cabinets hadn't been hacked. One of my pairs of S8s had ribbon tweeters. Maybe Aurum Cantus G2si? Recall that I modded my cabs to fit them with a little careful router work. Another pair (my last, IIRC) had the selenium ST324, which may have been the best blend of all with those MCM 5 inchers.

You guys asking for links to 20+ year old projects do make me chuckle a bit. I can't even remember what I had for dinner last night, let alone where some of those ancient files might be. Some of that stuff may have gone by the wayside when we switched servers and rebuilt the site about 10 years ago. What's left can be found below - possibly with many dead links. At some point someone sent me copies of the original printed S8 cabinet plans, but I'm afraid I haven't a clue where they ended up. Kind of a moot point - pretty sure none of the drivers for these old designs are made anymore.

https://archives.bottlehead.com/community/index.html

[Paul Birkeland]

I"m never going to use these and build the speakers.  Let me know your town and zip so I can figure out the shipping cost.  If it's not too high, I will "sell" the components to you for the cost of shipping.

I definitely wouldn't ship those, especially if you have the aluminum MCM woofers that Doc sprayed.  If one gets damaged in shipping, a replacement can't be recoated.  Feel free to drop me an e-mail at pb(at)bottlehead(dot)com and possibly we can figure out a time and place to meet closer to you.

[Ken]

Ah ha!  Superwhamodynes, of course.  Far back in the "good old days".  I stand corrected.

I seldom travel to the mainland these days but if/when I'm planning a trip, I will let you know and perhaps we can arrange a meeting somewhere near Bellingham or Blaine.

[Doc B.]

the aluminum MCM woofers that Doc sprayed

At some point Lord Adhesives stopped promoting that BL-100 stuff as a speaker cone and surround coating and started marketing it as a liquid (bodily fluid) resistant coating for bedsheets and gowns in hospitals. I can't even fathom how that sticky rubber stuff would feel sprayed on your hospital gown. Gross. Looks like they still make it. PJ talked them out of a pint or quart that I used for a couple years before it finally got too thick to use. I recall a gallon was very expensive and the shelf life was only 6 months.

https://www.lord.com/products-and-solutions/specialty-chemicals/aqualast-bl-100-butyl-elastomer-emulsion

https://www.adhesivesmag.com/articles/86502-butyl-emulsions-offer-new-options-adhesives-formulators

RE Superwhamodynes vs. Straight 8s - same tweeter, different 5" drivers. The Superwhamo drivers were very high Q and I put 4 of them them in a box with a big triangular "vent" hole. More or less an open baffle. They only went down to around 110Hz IIRC. They were not coated. The 10" woofers used in the Superwhamos were inexpensive and worked pretty well in a band pass box that went from 110 down to maybe 45Hz? Can't recall exactly. Should say in the archived article.

Not too long after I made those one of the new product guys at MCM and I had a talk and a while later they came out with a 5" driver with a different aluminum cone and a much bigger magnet that had a lower Q and a resonance around 55Hz IIRC. That is the 55-1870. That is what was used in the Straight 8s, in a vented box with real tubular vents and 8 of the drivers per side. Those S8 5" drivers and the tweeters were all coated on the front with thinned BL100 using an airbrush. The woofer frames were coated with a silica loaded latex paint for a while (very messy) and later they were damped with some super trick rubber backed aluminum tape that PJ suggested. I recall having to buy a $$$ case of that tape as the minimum order.