He's quite the character. That's part of the charm of this project for me. That, and he's not a home theater guy. This is reported to be a very musical sub. I pondered swapping out the Peerless driver for a Tang Band W8-704P which has "better" specs. But he insisted "do so at your own risk". "It works the way I designed it." I felt scolded and ordered the Peerless.Originally Posted by Alien_Shore
Alan,
do you think this plate amp will work for one bucket?
Dayton SA100
If only running the one bucket, it'll be 8 ohm, so I'll only get 75w out of the amp, and figured that may not be enough oomph, especially that the sensitivity on the peerless is only 80-something...
- Mike
It should. Bruce is using this one Bash 300W Digital Subwoofer Amplifier 300-750 for not much more $$$. I'm a fan of you can't have too much sub power.
Got 'em done.
It was quite a saga. I first tried painting them, but nothing sticks to this plastic. These had Walmart logos on them and that didn't even stick. So I guess I'll live with WM blue until I find some black ones.
The second issue was the Crown amp. I guess this is a pro level amp and not designed for home audio. My 12dB Grounded Grid preamp would not drive it. Even though Crown support says it has a 1.4V input sensitivity and my main amp is 2.2V and it drives that one just fine. Hum...
Every one else that has used this amp uses high level inputs paralleled off the main amp speaker outs with an inline resistor to knock the voltage down rather then the low level RCAs. I started with a 2.2K Ohm and ended up at only 220 Ohm to get the gain right. Here's a pic of the experimental cable I used while switching out resistors:
So now that I had output, I set off to trim it out. I've settled on 53Hz. The volume is about 8.5 of 10. At that level I can't 'hear' the subs when they're on, but the bottom drops out when they're off. That's the way I want it. Like adding salt to my soup. I want to bring out the flavor, but I don't want to taste the salt.
The blend is uncanny. My old KLH gave up some sub sonics, but it sounded dry and monotone. More of a vibration than a musical note. These sound sweet and smooth and very musical. I really can't tell where my Altecs end and these begin...until I turn off the Crown. Then..."oh, where'd all that nice deep bass go?" When I turn it back on, I can't really hear the bass come back...until I turn it off again. Nice.
Awesome job, Alan.
My first bucket is nearly complete - waiting for the concrete to hydrate.
While I am waiting for that, I played around with some box calcs for this Peerless 8" sub:
This plot shows that sub in my sealed box (0.5 CF is about what's inside the bucket), and in a 3 CF vented box. What a difference!
What I don't know is what WinISD is doing regarding box shape and how it would differ if it could model a cylinder.
Perhaps the next experiment is to take a 40 gallon brute trashcan and try out a 12" LoL!
- Mike
I was thinking the same thing! Then I thought of the amount of concrete required...
There's a funky component going on with the bucket too. It certainly is not rigid. The whole thing vibrates. Ed strongly urges to resist stuffing with fill or damping it in any way. The bucket itself becomes a passive radiator of sorts. So sound waves certainly shoot out the top, but they must also radiate 360* around as well.
What was also not expected is that they can take a punch. I was cranking out some old Madonna and the whole floor was shaking. And they're sitting on 3 rubber feet!
Most programs just define the cab's air mass as having a uniform particle density in an infinitely rigid cab, i.e. has no resonant modes, so shape is irrelevant and the vent's output is in the same location as the driver. MJK's more recent MathCad software is a bit better as it adds another dimension in length to include its 1/4 WL resonances and an adjustable driver and vent location along it, but still no 3D [width x depth] modes. AFAIK, of the programs available to the DIYer only AkAbak does 3D.
In short, as long as the cab's LxWxD are all near the same and the driver , vent on the same vertical side, then the programs are pretty accurate if measured outdoors on a large flat area.
The 'breathing' bucket lowers the speaker's effective Qtc [Qtb if vented], so can really 'tighten up' its transient response, so no need for any internal damping.
A 40 gal. trashcan has enough of a high aspect ratio to require using MJK's or similar software to more accurately sim it, though none can sim the 'breathing' cab's variable Q damping.
Even though the driver is upward firing, its BW is so large acoustically [80 Hz is a ~54" diameter 'sphere'] that it will still mirror image as a vertical 2pi [half] space radiator, though through the XO BW it may sound more 'airy' if it doesn't have a steep slope order.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
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