1x8 DIY practice cab build

[JdoubleH]

I just finished a 1x8 speaker cab to use for low volume practice. I am quite pleased with the results. More details to come, but here are some pics.







Details to follow

[staindbass]

looks very professional !

[Wes Whitmore]

Looks good and clean...Im interested!

[JdoubleH]

A little background on why I built this- Occasionally a couple of my co-workers grab their acoustic guitars and take over a conference room at work during lunch and play a few tunes. I don’t have any sort of acoustic bass at the moment, so on a few occasions I’ve brought my Genz shuttle 6 12t combo. With my bass on my back, it is a one handed load in, but total overkill. The cube shape of the cab also does not lend itself well to the two-football length distance from my car to my desk (never mind the rotary man-trap door or three other badge swipe doors I have to pass to get there, or inquisitive stares and occasional “what the…” ).
So It occurred to me that I need a small, light, quiet cab I could leave at my desk in my cubicle. That way I could just bring my bass with the Shuttle 6 in the front pocket. I decided that I wanted something no larger than my trashcan (about 15” high, 14” deep, 12” wide). So I fired up BassBox Pro and started looking at some potential drivers. I figured that a sealed box with its smoother low end roll-off might be good here. Efficiency and low f3 were not on the criteria list for this one. Also, sealed should be much easier to design, build, and construct.

The driver I finally decided on is the MCM 55-2971
which costs all of $7.67. 8ohm, 70 W, 3.5mm Xmax, a claimed frequency response from 50-6khz, and sensitivity of 89db 1w/1m. It weights only 2.9lbs. In my proposed box of about .9 cubic feet it modeled an F3 of 56hz, with a Qtc of .768 (which is very close to ideal). I knew it would end up a bit higher with bracing, but not matter. On “paper”, this ought to work very well.

I modeled a whole bunch of other drivers, but nothing came close to this one for low and high end response (as per specs). At that price, I could afford to buy several and it wouldn’t matter if the 375w into 8 my amp is claimed to push burned a few up! Actually, that did concern me a bit. I knew I wouldn’t be pushing anywhere close to even the 70w the driver was rated at under normal circumstances given the stated use I intend, but I could probably destroy this driver very quickly if I am not careful. So I opted to put a PTC inline, which is a type of self resetting thermal switch which opens when it gets too hot. I first tried a .75A, which I was able to get to cut very quickly. I then swapped that out for one rated at 1.10A so it wouldn’t cut out quite as readily. The final box measures 15x11x13 and with bracing and the handle recess, is about .812 cubic feet.

[JdoubleH]

I used 15/32 Arauco Ply, butt joints and PL. The handle recess template became a shelf brace front to back just below the driver drilled with a bunch of 1” holes. There is ample bracing on each side for a very solid box. The handle recess was routed from a stack of the same stock. I used a bit of bondo to fill where the panel end wasn’t flush with the adjoining panel. It is finished with a few coats of Zinnser 123, sanded between, then three coats of Valspar satin latex. It isn’t that durable, but I wanted to test out my color, and only cost about $3 for a 7 oz tester (of which I probably have enough left to do at least one more coat). I got the texture by doing the primer with a foam mini roller, and the latex with a ¼” nap velour mini roller (Whizz #91012). The handle is a Penn Elcom leather look strap handle. The corners are from Parts Express, as is the grill. I used gasket tape and Spax screws to mount the speaker.

[JdoubleH]

Yes, I admit I borrowed the handle recess idea (and even the type of handle) from Duke Lejune’s Thunderchild. The recessed handle is necessary since I want to set my Shuttle 6 on top of it, AND I want to carry this in line with the narrowest dimension to avoid the leg scrape-age that I hate about a cube shaped cabinet. The dimensions were chosen specifically for these two things. Narrow enough to carry, wide enough to stack the amp neatly on it.

Edit: I would have gone with a standard strap handle to be more original (also since they're cheap, like me), but it would have required a longer recess - too long for this cabinet. This was the only handle I could find which would fit neatly. I do however REALLY like Duke's handle design (and the rest of it too!)

[christw]

Coooooooool! I used two of those same speakers in a 2x8 cab that I matched to a 4x6 with the 6" version of the same speakers as well. Worked out great. Your cab is much classier though. I dig the design.

[JdoubleH]

But the handle recess gave me another option as well. The shuttle 12t cab has a little pigtail on it with a Speakon NL2 plug on it. I especially like that idea for this cab- firstly and secondly, it is cheaper and easier to implement. Thirdly, it will prevent me from getting to work and realizing I forgot a speaker cable (especially since I don’t use one with the other home of the shuttle, in the saddle on the 12t). I think stowing the pigtail in the recess is pretty slick, if I do say so myself.



The pigtail cable “gland” took a bit of inventionering by me. I couldn’t find any cable glands which would work in an inch or so of plywood- most are made for thin sheet metal panels (auto firewalls, for example). So I made it from some sprinkler parts. The main body is a ½” pipe fitting to ½” barbed flexible pipe connector. I sawed it down a bit and cut perpendicular into the threads to make it compress as the cap is tightened down. The cap was made from a simple sprinkler head. The assembly is totally air tight and is glued into the cab with PL. It comes apart easily to service or replace the pigtail. The terminal strip holds the PTC and is mounted with hot glue to the bottom of the handle recess.





Here's the other end with the PTC

[JdoubleH]

So, how does it sound? After breaking it in with a test tone overnight, FANTASTIC! I have always been a big fan of sealed bookshelf speakers for their bass quality. It is usually much cleaner to my ears. The depth of this thing is amazing at low volumes. It gets surprisingly loud. It is very flat and smooth, which I confirmed with a frequency sweep. It rolls off as predicted just under 60hz and extends nicely up to 5-6k. (I don’t have any other way to measure it currenty, so you’ll just have to trust my ears on this). The extended upper range is very sweet. Practicing through this is a pure joy. I knew it looked good when modeled, but I had no expectation of just how good it was going to sound in the wild.

I don't have any way of recording for you it at the moment, and I'm always skeptical of the value of doing so. There are too many variables. But I do believe that it would actually make an excellent recording cab.

[Wes Whitmore]

Thats the most bracing i have ever seen in a 1x8! Thanks for the detail...

[JdoubleH]

Originally Posted by christw

Coooooooool! I used two of those same speakers in a 2x8 cab that I matched to a 4x6 with the 6" version of the same speakers as well. Worked out great. Your cab is much classier though. I dig the design.

Thanks! I was just going to be a simple weekend project to meet my stated goal of having something to leave at work. I was going to just give it some waterlox or poly for a finish. Funny thing happened... I ended up assembling at least one of the panels with the 'C' side out by accident (doh, should't mess around in the shop after a half dozen beers), and my joints weren't that clean. So some bondo, ample sanding, and paint later, here we are!

[JdoubleH]

Originally Posted by Wes Whitmore

Thats the most bracing i have ever seen in a 1x8! Thanks for the detail...

I know... I was planning on doing NO bracing at one point... I just couldn't resist using the handle recess template as a shelf brace, though then my OCD kicked in.

It actually helped the glue up, as that shelf brace and lower bracing all interlocked as a single unit. It is so stiff that once I assembled the cab, the top sounded completely hollow in comparison, so I added the upper braces.

Total overkill, I admit though.

[jimmy rocket]

Man, this is exactly what I've been looking for. A small grab-n-go cab for my Aguilar TH500. I've got a whole mess of leftover birch ply from a built in that I just finished. I may have to give this a go.

[droo46]

Okay, maybe I'm just a little slow here but how exactly are you plugging the head into the cab?

[jimmy rocket]

Originally Posted by droo46

Okay, maybe I'm just a little slow here but how exactly are you plugging the head into the cab?

speakon cable coming out of the recess

[rickdog]

Very cool! This sort of stuff is why I love TalkBass.

A couple questions: if you wanted to use two of these drivers, you'd just double the box volume, and it would behave about the same, right? And do you know how much power it would take to drive your cab to Xmax?

[monkeyking]

Very, very nice! I'm guessing your friends would describe you as "detail oriented."

Great little cab and very nicely done.

[bgavin]

That is a nice, clean job.

Q: what is the finished weight?

[pylet2000]

Great looking little cab!

[RickenBoogie]

That little 1x8 cab is pure, 100%, awesome. Very nice work, and a great little design.