Homemade bass cab, 4 x 12. Advice / experience please

[police squad]

A few moons ago, I set about with a friend, to build lovely valve guitar amps.

WKZ we were called. Got a few good reviews and sold a few too. Here's a picture with Phil Hilbourne trying it

 

My woodwork was done in the midlands and the 4x12 cabs were basically old laney cabs. Birch ply, a bit smaller than a classic Marshall cab, loaded with vintage 30s. They sounded fab too.

I still have a couple of these cabs lying around and was thinking that maybe, if I changed the drivers to something more bass appropriate, would they make reasonable bass cabs. ( I have the only straight cab made, to make a full stack, all my cabs were angled. I could have a back breaking full stack, like I did when I was young.................stupid..................stronger............wanting to be louder than the guitarist.

When I first started gigging on bass I had a Trace Elliot AH150 Mk V thru a brand new marshall 4x12 bass cab.

Sometimes my mark bass club 1 x15 just doesnt have enough oomph, on stage. It's rare but I know when I can't get it against a wall, it lacks bottom end (fine in the PA though)

Your thoughts please lovely bass chatters

Otherwise I'll probably strip the vintage 30s out and sell them singularly 

[fretmeister]

The old Marshall VBC412 cabs can be bought for dirt cheap these days.

Might be an easier solution if you can cope with the weight.

[police squad]

5 minutes ago, fretmeister said:

The old Marshall VBC412 cabs can be bought for dirt cheap these days.

Might be an easier solution if you can cope with the weight.

I want to re-use my old cabs, I can sell the vintage 30s and put that towards the new speakers.

I'll probably never play guitar using a 4 x12 (My 1 x 12 combo is perfect) and rather than trying to sell them for peanuts, I can re-purpose them, Even if I only use them once in a while

[fretmeister]

V30 always sell well. Pretty good prices on the completed sales on ebay.

[Beer of the Bass]

Guitar 4x12 cabs tend to be rather smaller  in internal volume (per driver) than you'd choose if designing a bass cab from scratch. People have either just lived with that, giving a cab that's very efficient in the mids but lean in the lower bass, or you could make plywood blanking panels for two of the driver openings and treat them as 2x12 cabs.

[Balcro]

Replacing the drivers with bass units can work and I assume the 4x10 is a closed box and the gross internal volume of the cab is about 95 litres. The Celestion Pulse 12-200 fits quite well. The Eminence Beta 12a-2 works a little less well and may be a touch "boomier" in the low-mid bass (see coments above from "Beer of the Bass").

[police squad]

this is all useful stuff, maybe converting to a 2x12 is a plan

 

[Jus Lukin]

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Edited March 8, 2022 by Jus Lukin

[alexclaber]

You'd probably be best off blocking off the driver holes on one side of the baffle and fitting a port tube into each one, and then only having two bass guitar drivers vertically aligned in the other two holes.

[Bill Fitzmaurice]

11 minutes ago, alexclaber said:

You'd probably be best off blocking off the driver holes on one side of the baffle and fitting a port tube into each one, and then only having two bass guitar drivers vertically aligned in the other two holes.

I'm getting a deja vu vibe. 😉

[police squad]

17 hours ago, Jus Lukin said:

Beer of the Bass has the tone down!
If you're after more lows, a sealed 4x12 probably won't give you that, but they do have a great, roaring midrange that sits nicely in the mix, and they are very sensitive. I've downsized from a 4x12 to a 2x12, not to gain greater cab volume per driver, but to drop the overall output. Even with a 100w valve amp it was capable of monstrous volume which meant the amp was staying cleaner than I intended.
I've used Eminence S2012s for mine at the recommendation of Bill Fitzmaurice- and incedantally now have two I'll be selling since the downsize!

before you sell them, please PM me, 

[police squad]

11 hours ago, alexclaber said:

You'd probably be best off blocking off the driver holes on one side of the baffle and fitting a port tube into each one, and then only having two bass guitar drivers vertically aligned in the other two holes.

I take it we can buy off the shelf port tubes then?

[Dan Dare]

1 hour ago, police squad said:

I take it we can buy off the shelf port tubes then?

You can. Have a look on eBay. It could be a bit pot luck as to whether the sizes you want are available, but you should be able to mix/match once you've done the maths.

[police squad]

5 hours ago, Dan Dare said:

You can. Have a look on eBay. It could be a bit pot luck as to whether the sizes you want are available, but you should be able to mix/match once you've done the maths.

I'm sorry, did you say I have to do maths!! Where do I find the character 'Maths'

[grenadillabama]

Or, seal off one hole and use 3 16 ohm speakers in parallel . No ports . 

Edited July 24, 2020 by grenadillabama

[Bill Fitzmaurice]

1 hour ago, grenadillabama said:

Or, seal off one hole and use 3 16 ohm speakers in parallel . 

That's only an option if the cabinet has enough volume to work with three drivers, which may only be confirmed by software modeling of the speaker response with the available box volume net of the ports and drivers, and the driver Theile/Small specs. One must also use modeling to determine the area and length of the ports based on the most effective box frequency tuning and keeping the port air velocity within acceptable limits.

[BassBunny]

10 hours ago, police squad said:

I take it we can buy off the shelf port tubes then?

@Dan Dare beat me to it.

I'm sure if you posted the internal dimensions of the cab, someone will be able to model it and suggest suitable speakers and suitable port sizes. @Phil Starr?

If you can't get a port tube the right size, plastic Soil Pipe is good to make your own.

[Phil Starr]

If you want someone to suggest some speakers and calculate the port length then we need the internal dimensions of the cab and an idea of the budget you have to spend, and maybe an idea of what sort of sound you are aiming at. The idea of a 2x12 is a good one, it'll give you a bit more bass extension and save half the money. Using the old cab is great if you want a cab that size and shape and to save the hassle of finishing off a home brew cab but it can be more expensive than just buying a used bass cab as cabs of this configuration aren't fetching a lot of money nowadays. It's fun making stuff though and it saves a bit of waste. 

There's plenty of people on here who will do the calculations for you but if you need me to do it just message me.

 

[grenadillabama]

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Edited July 24, 2020 by grenadillabama
don't care

[police squad]

On 24/07/2020 at 19:26, Phil Starr said:

If you want someone to suggest some speakers and calculate the port length then we need the internal dimensions of the cab and an idea of the budget you have to spend, and maybe an idea of what sort of sound you are aiming at. The idea of a 2x12 is a good one, it'll give you a bit more bass extension and save half the money. Using the old cab is great if you want a cab that size and shape and to save the hassle of finishing off a home brew cab but it can be more expensive than just buying a used bass cab as cabs of this configuration aren't fetching a lot of money nowadays. It's fun making stuff though and it saves a bit of waste. 

There's plenty of people on here who will do the calculations for you but if you need me to do it just message me.

 

thanks Phil, I'll take the back off one and measure. It's a slanted cab

[fleabag]

On 24/07/2020 at 06:43, police squad said:

I take it we can buy off the shelf port tubes then?

Kerchiiiing  !!

https://cpc.farnell.com/c/electrical-lighting/light-bulbs-tubes/compact-fluorescent-light-bulbs-cfl/circular-cfl-tubes/bass-reflex-tubes

[police squad]

@Phil Starr

time to resurrect this thread

how do I measure the volume of a slanted cab?

TIA

[Woodwind]

44 minutes ago, police squad said:

@Phil Starr

time to resurrect this thread

how do I measure the volume of a slanted cab?

TIA

Treat it as two three-dimensional shapes and add the two volumes together:

A rectangular volume and the slanted triangular volume. 

For the triangular section, multiply the depth by the height then divide by 2 and then multiply by the width of the cab.

I've assumed the whole front face of the cab is slanted. Is this correct?

 

Edited November 17, 2020 by Woodwind

[Phil Starr]

Is it a Marshall guitar cab shape with just the top two speakers on a slant?

In any case just provide the internal measurements and i can work it out. Either give me the depth at the top and bottom if it's a flat baffle (front panel) or the depth and height where it bends if it is a split baffle.

[police squad]

yep ok mate thanks

It's at work and I'm working from home this week, I'll get it apart at the weekend and yes it's sloped at the top