i threw all my curve balls into this one. now its sort of rattle-y. no but, for real, i did all the maths i could do, all the cross bracing’s, stuffings, spacings, glueings, and what not that an amateur speaker builder could do for these guys. even got me a router so i could round the front edges. i mean really! two 8″ 12 ohm Peerless India woofers wired in series, with a 3/4″ large range Dayton Neodymium tweeter wired in parallel; bass output – per that kick ass tweeter- is lacking. takes an eq with bass on full to even out that sucker.
havent made the second one yet, tho. got all the parts. just was underwhelmed by the outcome, so… maybe ill try to get it done over xmas oh-10 break? yeah…. look for a walk through. might try a three subs in series… should lower impedance to… 4 ohm? i think thats right…
now these are some nice speakers. tang band 3″ bamboo cone, with aluminum “phase plug” that looks like a bullet nose. enclosure made of CnC milled MDF, in six layers and of 3 shapes (similar to the 4×4′s, face, middle and back). currently they are painted blood red, and fuel my tunes in my office. im a super poor documenter (i could like never do an instructable) only i cause i would only ever be able to remember to photo at the end, or like at one random point. below is post enclosure design (with 4.5 inch square foot, maybe .125cuft enclosure), and testing, and now these are the final to-be-glued-at-some-point pieces, but of course i don’t have any images of the glueing, sanding, primering, painting or installation process.
these are a set of parallel / series wired 4-by of some dinky little alu-cone full ranger specials from parts express (i think each driver was under 3 dollars). they are probly one of my most aesthetically pleasing designs, and they work for what they do (ie, it would be physically impossible to get earth shaking bass out of them, so this was a minimal enclosure). they do sound surprisingly good, when mated to a sub (as in 2.1), and would work well for an office or other compact area, lower decibel area.
the eclosure is made from red oak veneered furniture grade plywood, CnC routed into four pieces, in three shapes (two hollows in the middle, the face, and the rear), and then glued up with the diy’ers favorite vice: BOOKS! add four canisters of elbow grease, and 5 different grades of sand paper, and youve got yourself one smooth feelin’ speaker baby, oh yeah.
this is the first real post-google-blogger-migration-to-wordpress post. for now, the site is going to look like this. its not very exciting, but the idea is to move the site back, and its content forward. how am i going to dovetail all the old content into the new one?
i have no idea.
its just going to take time, so for now, this section will only really have everything ive done since moving from london, uk, to baltimore, maryland.
bass death is a project im working on that consists of the theory behind a bass cannon, but scaled down, and with all found parts. (bass cannon = bass of death = bass death.) essentially its an experiment to see if bass cannon theory is scalable.
the theory is that off either side of any driver come equal but opposite polarity signals (in wave form) that we recognize as “tom waits” or “john coltrane doing is strangled goose noise thing”, but what we may not realize is that half of that speakers signal had to be killed so that we can hear the other half – otherwise these two opposite polarity signals neutralize each other, and this is exactly what “active noise cancellation” is all about. essentially, this is what a speaker “enclosure” aka speaker boxx is for – to deaden one half of any given speakers signal.
so Dr. Amar Gopal Bose – of Bose, and a resident lecturer and all around “cool guy” at MIT – goes, ‘ok, how can we capitalize on both signals – what needs to happen so that we can use both?’
and that answer lies in matching polarity!
and the way to match polarity? send one signal out a tube of distance X, and the other signal out a tube of distance 2X. now, the (extremely limited and thin) theory ive read on this is that higher than subsonics, and it doesnt work – but is should work for anything below, say, 150 hz. only in my minds eye, it should only work for one very specific frequency. never the less, those who have executed Dr. Bose’s strange and wonderous beast (and to scale), have reported success and have implemented it for various warehouse party situations – but im not about to invest in a 15″ sub, 1000 watt mono amp, or the concrete column forms.
having found many discarded, but working subs from 2.1 computer systems, i decided to use a 4″ yamaha driver, in combination with a few smaller but sturdy mailing tubes that house the rolls of banner we use at my shop. measuring 6 wide x 56 tall, these are about the best things going outside of actually purchasing the recommended solution, and the only thing left to procure was the mounts that would bring the whole thing together.
after a few beers, twice as many measurements (“measure twice, cut once”) and an evening of laying out in illustrator, i was ready to send my creations to the router. using scraps of 1/2 inch black pvc from some other job, i was able to bust out one test plate to check the measurements of the seat that the tube sits in – out by 1/10 of an inch! re-adjust measurements, and send the whole thing to cook!
next up was the glueing of the struts to the tube and plate that mostly hold it together. i used a silicon compound of some sort that seemed the most appropriate – really, what i had at hand wasnt all that good, so it was the best of the worst so to speak, but its held together fine.
here im testing the tightness of the tube-to-flange-groove mate – strong enough to lift it up no problem!
not knowing how to size the struts, i decide to create some rythym and use an alternating 5/7 inch pattern – but the real question will come when i mount the two halves – matched? or offset?
after that dried, i then went at ‘er with a drill and screws, to really make sure she holds tight – 8 x 2″ drywall screws for each side, from flange to strut, and in tight enough to draw under so their heads dont interfere with the final mating, and 8 x 3/4″ screws / side from strut to tube, just to really make sure everyhing holds. once completed i then placed, marked, drilled and then mounted the sub to the tube with the slightly smaller plate (smaller so it can receive screws, while the other plate is big enough to clear the sub during mounting). initial tests of just the one tube with driver were positive, but the (fully working regular) speaker that i powered off the other channel of the same amp, with the same power and signal still outperformed it.
you can just make out the alternating “drywall screw, hole for bolt, drywall screw…” pattern visible on the top surface. the foam thing is a some sort of vibration isolator for the cable. i think.
that part was last night.
FINALLY today im going to drill the last hole, feed the supply wiring through, mount the two halves, and power that baby up. although i might put in a (im guessing) better driver pulled from an altec lansing 2.1 system of similar proportions, but hopefully higher power handling.
“Amar Bose believes that imperfect knowledge of psychoacoustics limits the ability to adequately characterize quantitatively any two arbitrary sounds that are perceived differently, and to adequately characterize and quantify all aspects of perceived quality. He believes, for example, that distortion is much over-rated as a factor in perceived quality in the complex sounds that comprise music, noting that a sine wave and a square wave (a hugely distorted sine wave) are audibly indistinguishable above 7 kHz. Similarly, he does not find measurable relevance to perceived quality in other easily measured parameters of loudspeakers and electronics, and therefore does not publish those specifications for Bose products. The ultimate test, Bose insists, is the listener’s perception of audible quality (or lack of it) and his or her own preferences.[22] Unlike other major speaker manufacturers, Bose does not publish specifications relating to the measured electrical and objective acoustic performance of its products.[23] [24]. This reluctance to publish information is due to Bose’s rejection of these measurements in favour of “more meaningful measurement and evaluation procedures”…” – aka, the listeners ears.
