4x10 Bass Cabinet Dimensions/Drivers

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This seems like the right place to post this thread so here goes:

A friend and I have recently started producing guitar cabs, but have come across a few hurdles when challenged to build a bass cab...

Now I understand a lot of factors when building cabinets or speakers of any kind really do come down to personal preference, but there's a few things I need some general guidance on.

Drivers:
So I figure these will have the biggest effect on the dimensions of the cab, so I'll start here. We are planning on using 5 drivers in total, 4x10" drivers arranged in a square with a horn/compression driver in the center. As far as the 4x10" drivers go though, I've been thinking that it could be a good idea using 2 different types of speaker, for instance the bottom 2 speakers would be low end bass guitar speakers, the top 2 would then be mid range, and then the center speaker handling all of the highs to give the cab a more full range effect. At the moment I don't see any problem with this configuration, but if there are any flaws in this type of layout please point them out. Then comes the question of what types of speakers to use for mids and highs? for highs we are pretty much definitely going to use a compression driver (because of personal preference), but for mids, should we be looking at speakers specifically designed for mid range? or should we be buying bass guitar speakers with a good frequency range, then using a crossover to cut out the lows? So far I've just been looking at standard mid range drivers, but if there is anything specific I should be looking at, again, please point it out!

Dimensions:
So the dimensions of the cab will obviously be affected by the Vas required for the drivers to run smoothly if i understand correctly? My question though, is say I had 2x10" bass guitar speakers which require 1.4 cubic feet of Vas each, do you just simply add these together to equate to 2.8 cubic feet of Vas and then build the cab accordingly? or is there some sort of algorithmic way of figuring this out?

For instance, right now the speakers I am looking at are 2x10" bass guitar speakers, requiring 3.2 cubic feet of Vas each, along with 2x10" mid range speakers requiring 1.02 cubic feet of Vas each, so if I was to figure out the total inside volume of the cab would I simply add all 4? (2 x 3.2) + (2 x 1.02) = 8.44 cubic feet of Vas? I know there is WinISD to do this for me, but I find it better to learn to do it manually first so that I can understand what the program is actually doing.

Vents:
So, I don't understand much about the use of a vent in a bass guitar cabinet. In what situations should/could they be used? How are they best used? How do they effect the inside volume of the cab? slotted vents? or tubular? How many are necessary if at all?

Crossover:
I'm fairly sure I understand the crossover well enough, but I will clarify it anyway. The way I understand this is that the crossover allocates different drivers to take car of certain frequency ranges in the spectrum of sound. So for our cab design, we'd be looking at a 3 way crossover. Actually I've already had a look, so I'll list the crossover, drivers and their frequencies here:

Crossover: Dayton XO3W-700/5.6K 3-Way Crossover 700/5,600 Hz
Low Freq Driver: Eminence Legend BP102: 40-2,000Hz
Mid Range Driver: Selenium 10PW3-SLF 10" Driver: 60-6,000 Hz
High Freq Driver: Eminence ASD1001S 1" HF Titanium Horn Driver: 2,500-19,000 Hz

So again, this post is mainly to clarify certain grey areas in my logic and understanding, so please do point out any errors in planning here so that I can plan this cab out a bit more!

Thanks for reading,
Hobojangles.
 
Hey Hobo,first off Vas is the driver equivalent air compliance
and shouldn't be used as the driver box volume #. Is is used in
conjunction with fs, Qts etc in the T/S formula to determine the
optimum box volume for each specific driver. If you have the formulas
say from the loudspeaker cookbook, then it is easy to figure out.
Otherwise it is just as good using a program:). Secondly if this
Is your first (or one of) cabs,try all 4 10" ers in one pass band
and a larger size diaphragm (2"-2 1/2") comp driver (that will play lower)
to handle the
highs in a two way configuration. Three ways are much harder to
design if you don't have test equipment.
Vents help in several ways but they do introduce a sharper low
end cut-off where the cone becomes unloaded. And programs can also
help determine X-max limits. Hope this helps!
 
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If you want tips/opinions/etc. concerning bass cabinets, their design, construction and use, head over to the Talkbass forum.
TalkBass Forums: The Bass Guitar and Double Bass Online Community

Go to the section labeled "Amps". Before posting, use the "Search" feature a lot, as this will be the first knee-jerk response from some, and there is a wealth of good information from designers, builders and players. If you have well-formed questions, there are plenty of helpful people who will jump in. I would recommend that you take some time to find out who and what makes a good 4x10, and what you can do to differentiate your product from all the others.
 
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