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Discussion in 'Amps and Cabs [BG]' started by Barcode, Mar 17, 2010.
That probably wouldn't keep up with the woofer very well.
At the cost of the alphalite 6 cbmr, I would just suck it up and work out a way to put a midrange chamber in there. It should be possible to glue one in if you remove the woofer. The routing of the hole in an attached baffle can be really challenging period though, and I wouldn't recommend doing it unless you really have a good router -- mine couldn't do it (The circle jig didn't have enough clearance).
Alpha 6a = 93.6 dB sensitivty versus
ALPHALITE 6A-CBMR = 99.8 dB
Wouldn't keep up?
Look at the Alphalite's FR chart again. It's got a big valley or two -- its sensitivity is an average of a lot of peaks and valleys (which makes it kinda unsuitable to the general design idea).
Use 5.5" hole saw and rasp it out.
I don't see a big diff between 800 Hz and 2.5 kHz... neither is flat but neither is so off you can't EQ your way out of trouble.
Foz, how does the 800RB sound biamped into a fEarful?
Any noticeable dips or holes at the crossover point?
BTW what do you crossover at?
Its got that classic GK vibe... super punchy, edgy, gritty with pronounced high-mids. Would work for just about any rock band - from pop to punk and could do funk or blues pretty good too I reckon. It can play fairly clean but that aint its forte. Hell of an amp for the money IMO.
Haven't played around enough to have a firm opinion on xover with the 15/6 but I think I ended up between 11:00 and 1:00 - not sure what that equates to as far as frequency - the register marks are merely decorative, not informative as the slope/taper of the pot.
Make a template out of 2 layers of MDF that combined will be slightly greater than 1 1/8th deep. The template should be square and sized to fit in the corner of the cab and locate the hole at the correct spot on the baffle. Use a long, top bearing router bit.
Crossover wiring wise, I would implement the crossover in the head cab and provide a jumper to the sub cab. I used 1/4 in and 4 wire Speakon out on mine to prevent a fubar ...
If you think about it, if the sub is used as an actual sub, it will probably be running off an active crossover...
This is my first post on TB.
A bass player on another forum recently asked about BFM cabs and Davio suggested he also check out GBs fEarful designs. That piqued my interest, so Ive been spending nearly all my free time lurking here. So far Ive read every post from the very beginning of these threads up through Nov. As a result, I am now embarking on a 12+6 build
Ive ordered the crossover components from Erse and the drivers and misc. hardware from Speaker Hardware (Leland answered an email question on Easter morning!).
Im using the Alpha 6 with no HF driver. Ill add the HF section later if I find I need more air. Weight is one of my prime considerations, so Im forgoing the BB ply. I havent been able to find Arauco ply in my area, so Ill be using the 5 ply pine from Home Depot that Ive used for other cabs. My current plan is to paint the exterior of the cab, but I might try my hand at applying vinyl. In either case, Ill do it in green as a tribute to the Green One. I have some ½-grid chicken wire Im thinking about using for the grill (and maybe behind the port shelf). I plan to put a strap handle on the top and one side. For lining I plan to use either fibrous carpet padding or 2 fiberglass batting, both of which I have on hand. (Maybe a layer of each?) Instead of bolts and t-nuts to fasten the drivers, I plan to glue small squares of ply behind the baffle and use the screws that Speaker Hardware sells.
As I wrote above, I havent read the most recent posts, so if anyone thinks Im off-base with any of this, feel free to point it out. In return, Ill post progress pics and a review comparing my finished 12+6 to my Acme B2 and BFM Jack 10s.
fiberglass batting will work better and weigh less [it being porous]
I use polyfill from the craft store myself. It's cheap and super light. I paid around 8 dollars with the 40% of coupon for a roll that was enough to line my cab 4 times over.
Assuming the goal is axial mode suppression and that the longest dimension of the fearful designs is a quarter wave of a mode that falls into the 125 Hz frequency band, you might find that the very low density of typical quilt batting is suboptimal.
I expect the slightly higher density [gives rise to acoustic impedance] of standard fiberglass insulation batting is probably a better choice. You could look at using semi-rigid boards like Owens Corning 703 but that would be a PITA compared to installing batting. Or you could staple down a double layer of quilt batting to effectively increase density but that also seems like it might be a PITA.
You can review the performance per band of various members of this class of materials here:
I use a spray adhesive instead of the stapling. It's a little more permanent but a lot easier. Double layer was no problem.
Welcome to TB, wcriley. Glad you took such an interest in the fE designs! In my mind, every bass player we get touting the pros of this sort of design brings us one step closer to the big companies coming around to invest in R&D to further refine it and make it widely available.
You'll probably finish your fE12/6 before I will. Gotta finish paying for a cruise for the gf and me before I can put money back into this endeavor.
Thanks for the link. Can't say I understood any of it...
If denser is better in this application, then I think I might be on the right track with the carpet padding. It's not the foam type. It's more like what's used in automobiles. (In fact, that might be where it came from.)
The material has to have interstices [little holes] to work as a porous absorber... carpet pad that is closed cell foam will only function as an acoustic absorber through mechanical vibration. if you can breath through it - it might work OK. A sure bet is to use something fluffy - regular batts of pink fiberglass is a pretty good choice. Polyester quilt batting will work too but I reckon you'd need to add a good bit more to get equivalent results.
Fiberglass is nasty to work with, so I'd recommend just using the thick quilt batting or foam mattress topper.
Mattress topper is my preferred (open cell with the egg cratey top) but I didn't have it available at a reasonable price and didn't feel like cutting it to fit over all my bracing in my tiny cabinet.
If laying a few thousand square feet of batting in a cramped attic you'd be wise to wear a disposable paper jump suit, safety glasses, a hat, and a disposable filter mask, but anyone who can be trusted with pointy ended scissors can stuff a couple square feet of fiberglass batting into a box and staple it down without incident. The dangers and difficulties of working with fiberglass batts are vastly exaggerated and it has excellent acoustic properties per unit weight - better than any other material I have seen measurements of.
A randomly chosen open celled foam might work well or it might not - you could end up adding weight to the cab to little or no actual benefit. If you don't have any experience with acoustic absorbing foams you could well make a mess of things by picking something inappropriate.
I know people do it - but I can't see any reason for cutting up a bunch squares of to fit between the ribs - small air gaps behind an absorptive material as it ran over the ribs into the next cell would not diminish its efficacy - quite the opposite in fact.
Haven't built a fEarful yet, but I've been following the threads from the start.
I use the egg crate foam...very porous and the egg crate shape is excellent at trapping midrange frequencies (the purpose of the batting to begin with in a bass cab).
I would avoid fiberglass like the plague. As the name implies it is composed of thin fibers of glass and over time could work their way into the speakers. Fiberglass and voice coils is not a good thing. It's possible nothing would happen, but I wouldn't risk it. If it gets on you just putting it in, some loose fibers are already present in your cab. Same reason I no longer staple batting in my cabs. One loose staple could be an accident waiting to happen.
Food for thought. Carry on.