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DIY simple 1x10 bass cab project

T

tonebrulee

Sep 15, 2007
416
19
Northampton, MA
#1
Hey folks,

I'm a newbie bass player as well as a newbie cab builder, so this thread may only appeal to others at the beginning of their low-end journey! In any event - I've just been noodlin' around on bass for 6 months now and have been looking for an economical rig with a little more soul to it than the cheapie 30w practice amp I've been using.

Searching around a bit here, I found the Bill Fitzmaurice site and ordered Bill's plans for the [Invalid or Expired Link Removed] cab - really nice instructions. I also spent the extra coupla bucks for the excellent Panel Jig plans. I'm planning to build the Omni10.5 version which is about half the size of the full Omni10 and uses just 1 driver instead of two: I picked up an Eminence Legend BP102 online for $75. For the amp, I found a Invalid Link Removed in good condition used for $190.

The Omni10 project is a little involved for a newbie like me, so I thought I would build a simple, small ported box for the BP102 as a practice project for the Omni10.5. Reading the forum here, I found some good info including a link to the WinISD tool for calculating cabinet box volumes and port dimensions. I also found some good info on the Eminence website for cabinet specs for specific Eminence drivers, including [Invalid or Expired Link Removed].

This thread will follow my progress in building a cab based on the specs for Eminence Legend BP102 Larger Vented 1x10 Bass Guitar Cabinet found on page 5 of the PDF doc. Really looking forward to building this cab and hearing from others who might be considering a similar project as well as folks with insights on any questions raised.

G'night for now!
 
#4
After further reading about the Eminence BP102 and working through scenarios in WinISD, I am going to build the cab with a 2.7 litre volume. The [Invalid or Expired Link Removed] design for a 2.0 litre cabinet had too much roll-off below 60Hz for my taste. The driver really seems to want 4.0 litres for a full-range flat response for 4-string bass. Given that this cab is a dry run for building the [Invalid or Expired Link Removed], I'm OK with sacrificing some low-end performance to have a smaller cab I can use as an alternative to the Omni when desired. From the GAIN graph, you can see that at 40Hz, the 2.7 litre volume gets you to -2db relative to the flat response for the 4.0 litre box, a full 2db gain from the mark provided by the 2.0 litre box.

Here's the key to the five cabinet volumes I plugged into WinISD.

WHITE - 2.0 litre
ORANGE - 2.7 litre
PINK - 3.0 litre
BLUE - 3.2 litre
GREEN - 4.0 litre

GAIN graph
[Invalid or Expired Link Removed]

SPL graph
[Invalid or Expired Link Removed]
 
#6
Hello tonebrulee,

Nice project, I am in the process of building an Omni 10.5 pair right now - check out the thread :

http://www.talkbass.com/forum/showthread.php?t=366001

Also, glad to see another Western Mass TB'er - I am from Wendell originally and just relocated from the Happy Valley to Maryland. good luck with your build. Also, glad to see you are making the effort to understand the design part of building a speaker enclosure.
 
#8
tonebrulee said:
This thread will follow my progress in building a cab based on the specs for Eminence Legend BP102 Larger Vented 1x10 Bass Guitar Cabinet found on page 5 of the PDF doc. Really looking forward to building this cab and hearing from others who might be considering a similar project as well as folks with insights on any questions raised.
Click to expand...

tonebrulee said:
After further reading about the Eminence BP102 and working through scenarios in WinISD, I am going to build the cab with a 2.7 litre volume. The [Invalid or Expired Link Removed] design for a 2.0 litre cabinet had too much roll-off below 60Hz for my taste. The driver really seems to want 4.0 litres for a full-range flat response for 4-string bass. Given that this cab is a dry run for building the [Invalid or Expired Link Removed], I'm OK with sacrificing some low-end performance to have a smaller cab I can use as an alternative to the Omni when desired. From the GAIN graph, you can see that at 40Hz, the 2.7 litre volume gets you to -2db relative to the flat response for the 4.0 litre box, a full 2db gain from the mark provided by the 2.0 litre box.

Here's the key to the five cabinet volumes I plugged into WinISD.

WHITE - 2.0 litre
ORANGE - 2.7 litre
PINK - 3.0 litre
BLUE - 3.2 litre
GREEN - 4.0 litre

GAIN graph
[Invalid or Expired Link Removed]

SPL graph
[Invalid or Expired Link Removed]
Click to expand...
The cab design on P5 of the Eminience BP102 is for a 2 cubic foot cab, not 2 litres. 2 cu ft is about 56 litres.

There is no way in a pink fit you're going to get any sort of sensible response from a driver with a Vas of 91 litres and a Qes of 0.47 in a 2 litre box.
 
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#9
From the graphs, it looks like he is working in ft^3.

Given how these curves all agree within 0.5 dB in the pass band, the only variable is how much low end the OP wants. If at all possible, I suggest measuring some commercial cabs that are close to the tone quality you are seeking.

But in addition, a message to every DIY'er should be: Check your units carefully! Unit-of-measure errors have been responsible for some high-profile engineering failures.
 
#10
fdeck said:
From the graphs, it looks like he is working in ft^3.

But in addition, a message to every DIY'er should be: Check your units carefully! Unit-of-measure errors have been responsible for some high-profile engineering failures.
Click to expand...
D'oh. Missed that.

Your second point is very true.
 
#11
fdeck said:
From the graphs, it looks like he is working in ft^3.

Given how these curves all agree within 0.5 dB in the pass band, the only variable is how much low end the OP wants. If at all possible, I suggest measuring some commercial cabs that are close to the tone quality you are seeking.

But in addition, a message to every DIY'er should be: Check your units carefully! Unit-of-measure errors have been responsible for some high-profile engineering failures.
Click to expand...

Yep, like crashing expensive probes into Mars or this near miss:

http://en.wikipedia.org/wiki/Gimli_Glider

Not to say that building a bass cab box wrong is going to cost hundreds of millions of dollars or put hundreds of peoples' lives in danger. ;)
 
#12
Geoff St. Germaine said:
Yep, like crashing expensive probes into Mars or this near miss:

http://en.wikipedia.org/wiki/Gimli_Glider

Not to say that building a bass cab box wrong is going to cost hundreds of millions of dollars or put hundreds of peoples' lives in danger. ;)
Click to expand...

Yup. IIRC one of the Mariner missions was also lost due to a similar error.

It's true that a bad bass cab won't kill anybody, but you don't have to make a lot of mistakes before your project costs you more than an Avatar cab. For this reason, it is probably good advice to use drivers and parts that are known to be happy in a variety of different design types, so you only have to build a new box if you don't like your tone.
 
#13
The new style BP102 with Polyimide former needs a box between 2.7 and 4.0 cubic feet. F3 is 36 to 32 Hz, respectively. SPL in the mid-bass is around 92 according to the Eminence PDF sheets.

The BP102 has no high end, and will lack sparkle and clarity by itself. It needs an additional driver to provide this. The Eminence Alpha 6a is a perfect match. You will have to build a crossover, as nobody makes one for 200 Hz that I am aware of. An easier solution is the Alpha 8MR, because it does not require a sub chamber. I prefer the Alpha 6 response, plus it is a closer match to the BP102.

This combination will give you essentially an Acme B-1 cab. It isn't particularly loud, but will get all the way down for low B support. Think of it as a very HiFi type cabinet.

A better solution is the Deltalite-II 2512 driver. It does not need the Alpha 6, because it is good up to 2500 Hz. The 2512 is a LOT louder, about +5dB in the same range. You can add piezo tweeters if you want, because they mate well at 2500 Hz, where the 2512 rolls off. 2512 requires 3.4 to 4.6 cubic feet for optimal tuning. Since you already have the BP102, this isn't an issue.
 
#14
alexclaber: From WinISD, the tuning frequency that provided the best combination of flat response and volume near 40Hz was 34Hz and you can see that in the posted screenshot. Given that the graph drops off steeply by 34Hz, I'm not sure I understand how the target value relates to performance in absolute terms - i.e. volume/sensitivity at 34Hz. Anyone care to offer an explanation?

a9x: right - I'm working in ft^3, not litres. Sorry for the confusion.

Crockettnj: definitely, it'll be interesting to take the same driver and put it into the [Invalid or Expired Link Removed] with the same volume and compare.

pjwalsh: Cool! Your thread looks great.. I'll definitely be reviewing it when I move onto building the [Invalid or Expired Link Removed]. Sorry to lose a low-end amigo from the Valley!

----------------------

I worked out the panel cutting plan tonight and found that I can get all 6 panels for the cab from a half sheet of plywood if I bump the total internal volume down a notch to 2.6 ft^3, so that's what I'll be doing.

The panel cutting dimensions are as follows (height x width):

front baffle & rear panel: 15.5" x 22.75"
top/bottom panels (2): 16.75" x 23.75"
side panels (2): 15.5" x 16.75"

I'll be building the cab from 1/2" birch ply (good enough for Bill Fitzmaurice, it's good enough for me) and it will be horizontally oriented with the back panel flush and the front baffle recessed 3/4" from the front. The width along the top will be 23.75" which will match the Invalid Link Removed head perfectly.

Interior cab dimensions: 15.5" h x 22.75" w x 15" d (2.6 ft^3)
Exterior cab dimenions: 16.5" h x 23.75" w x 16.75" d
 
#19
acmebass said:
Or not.

I don't mind you guys running your mouths, but please keep me out of it.

Thanks,
Andy
Click to expand...

You using one of those search robot things that let's you know whenever anybody says "Acme" on the internet?

Discarding roadrunner cartoons of course. :)

The bp-102 gets compared to the woofers in your cabs because it's one of a very damn few 10's that can reach that deep at all.

Obviously, it still can't reach that deep without a much larger box, so it.'s still not an Acme. :)
 

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