The Burning Amp Festival- an Audio Happening

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and a picture of the Krell KSA 50 clones and a pair of ZD5's

Thanks for a great event
 

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DSP_Geek said:


That one's mine. A friend of a friend had a scheduled showing of his pictures of whales, including life-sized projections of blue whales onto a wall, and he wanted to play blue whale songs to accompany the visuals. Now, blue whale songs aren't the usual eeeeooOOOOOooeeee you hear from humpbacks, but much lower - the fundamentals range between 10 Hz and 40 Hz.

I happened to have a couple of spare TC Sounds woofers on hand, and a session with WinISD (wonderful tool, highly recommended) showed 10 Hz was not possible with any sanity, but 16 Hz was definitely doable. Since that's the limit of human hearing, losing the bottom 2/3 octave wasn't a big deal. We just applied a 14 Hz high pass function to the stored whale songs so the really low frequencies wouldn't launch the cones across the room.

Ray (the original friend - he's the quiet guy with the really long hair you may have seen) and I planned the whole thing around 2' x 4' (61 cm x 122 cm) MDF panels from Orchard Supply, but we got a nasty surprise when we found they were as much as 1/8" (3 mm) off square. Just a heads-up, folks.

The cabinet was built with double-thick walls on all sides, laminated with Titebond glue. The laminations were held together by 3/8" (9 mm) nuts & bolts, with ductape-covered washers to distribute the compression and keep the bolt heads and nuts from sticking to the panels. At the same time the box was being held together with 21 furniture clamps, with extra screws holding the center partition and front-to-back and side-to-side bracing in place. We went through about a gallon of glue.

The ducts are 4" (10 cm) ABS sewer pipe, glued to the MDF with the same glue used to glue the 90 degree bend to the pipe. It works rather well, which is no surprise since MDF is half glue anyway. The ductwork and the inside front panel were preassembled with the rest of the cut panels before gluing up the whole box, to ensure that final construction would be well aligned. The ducts are about 32" (80 cm) long, tuned to around 18 Hz in a 5.5 ft^3 (155 liter) box.

F3 is between 16 and 17 Hz. 120 watts per driver moves the drivers well short of Xmax above Fb, but at 16 Hz the cones are working hard. It turns out the whale guy wanted to play other whale songs through this thing, including humpbacks which can range up to 1 or 2 kHz. Le (voice coil inductance) was our friend in this case, rolling off the highs so we didn't deafen the museum patrons.

If there's any interest, perhaps Ye Moderators might want to shift this thing to its own thread.

These are the guys I told you about, 1 1/4" MDF in 4' x 16' panels (not your normal Lowes item).

http://www.boulterplywood.com/composites_4.htm
 
DSP_Geek said:

........The cabinet was built with double-thick walls on all sides, laminated with Titebond glue. The laminations were held together by 3/8" (9 mm) nuts & bolts, with ductape-covered washers to distribute the compression and keep the bolt heads and nuts from sticking to the panels..........

I meant to say that the carpentry on both your cabs was beautiful. Looove that 1.5" round router bit you used on the edges - makes it look so much more.....substantial.

...and yes, I too as a 16yr Californian thought we were having a wee tremor. You should download some of the seismic data from USGS (like for the '89 loma preita) and play that back as a wave file (I tried using earthquake data as kick drum samples a while back with rather too good an effect) Then again, maybe you shouldn't
:D
 
Iain McNeill said:


...and yes, I too as a 16yr Californian thought we were having a wee tremor. You should download some of the seismic data from USGS (like for the '89 loma preita) and play that back as a wave file (I tried using earthquake data as kick drum samples a while back with rather too good an effect) Then again, maybe you shouldn't
:D

Or this one: http://wavebourn.com/rain_helicopter.mp3 -- I use it to test myPA gear so neighbours won't complain about music playing...
 
scott wurcer said:


These are the guys I told you about, 1 1/4" MDF in 4' x 16' panels (not your normal Lowes item).

http://www.boulterplywood.com/composites_4.htm

Indeed not. I dread to think of the shipping costs, however, especially since their 4' x 8' 3/4" MDF seems about 25% heavier than anyone else's. In other news, Ray and I went to the Maker Faire (recommended for DIYers, it'll blow your mind), where we saw this:
http://www.shopbottools.com/prSalpha.htm

And these guys have one:
http://techshop.ws/index.html

Tweeter waveguides, anyone?


Iain McNeill said:


I meant to say that the carpentry on both your cabs was beautiful. Looove that 1.5" round router bit you used on the edges - makes it look so much more.....substantial.

The router bit was actually left over from the 3-ways to sort out the edges so I could avoid diffraction effects. That's rather not a problem when the wavelength is measured in meters instead of centimeters, but it keeps the edges from looking too shabby with use, as unhardened MDF tends to do.

Besides, (don't tell anyone) a big roundover covers any number of sins in assembly.


Wavebourn said:


Or this one: http://wavebourn.com/rain_helicopter.mp3 -- I use it to test myPA gear so neighbours won't complain about music playing...

Ah, thank you. The lowest frequency there seems to be about 25 Hz, so the taller boxes should deal with it handily. WinISD says they should roll off about a half-octave higher than the whale woofers, or about 22 Hz.
 
diyAudio Editor
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Oh yeah,
I ran into Ray Kimber at the Rocky Mountain , and he gave me a bunch of his CD's to pass out at the BAF. They are recorded with his isoMike approach and the quality was very impressive!

We got into a conversation when I mentioned that Nelson Pass must like them because they had about 8 Pass amps in their (large) room . He said "And we like Nelson" then gave me the dozen disks for our show!
 
frugal-phile™
Joined 2001
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FastEddy said:
Did anyone ever locate the plans for these cute and great sounding pine box towers?

Try the BIB thread. Or just use the BIB calculator off of Godzilla's BIB pages. Do use a PP amp with fairly low output impedance, these drivers don't like SE amps of any flavour.

And keep in mind that they are ideally corner loaded.

For a BIB this short it is well worth building an inverted version since you can get floor loading where you can't get ceiling loading.

dave
 
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