Easy 12" cab build

[Phil Starr]

5 hours ago, Johnny Wishbone said:

Update: the wood for my pair of cabs has finally been sourced, cut to size and is being delivered tomorrow!

@Phil Starr I recall you saying that the 50l cabs are still a one hand lift - is a decent quality strap handle all that’s required?

Mine are built with 12mm Baltic birch ply and weigh about 14kg. All I have is a reasonable strap handle and I usually carry one in each hand. I'm a not particularly big 66 year old so a long way from being a superman. The only problem is that they bang against your legs a bit 

 

[Johnny Wishbone]

On 11/07/2018 at 21:36, Gottastopbuyinggear said:

If that’s a success then I’ll have a couple of Beymas going spare

@Gottastopbuyinggear If you do decide to move those on I'd take them off your hands. Just about to start building this week!

[RichardH]

I used a strap handle on my 25kg 1x12 I made ages ago (18mm baltic birch, using the EV TL806 plans). I used teenuts for the strap bolts though - not just a screw into the cab timber. It was absolutely fine. 

 

[Johnny Wishbone]

1 hour ago, RichardH said:

I used teenuts for the strap bolts though - not just a screw into the cab timber. It was absolutely fine. 

Yup, tee-nuts are on the way.  I definitely won't be using just woodscrews!

[Phil Starr]

Ha ha, because I rarely get past the 'prototype' stage mine still haven't had the woodscrews replaced with proper T-nuts.

[Gottastopbuyinggear]

12 hours ago, Johnny Wishbone said:

@Gottastopbuyinggear If you do decide to move those on I'd take them off your hands. Just about to start building this week!

I think I’ll be hanging onto them to be honest - Plus they’re still in the cabs at the moment, and the Beta 12s are still in their boxes!

I bought the strap handles I used, along with the bulk of the rest of the hardware, from Blue Aran.  They have a metal strip inside the rubber outer so they’ll take plenty of weight.  After you’ve used them they won’t go back completely flat, but that’s probably not an issue.  T-nuts definitely though.  Here’s one of mine before I put the grilles on...

 

[Phil Starr]

I get real pleasure at seeing that, and in knowing it is used and loved. Thanks

just a quick one Lidl's have a special offer on table saws. 10" 2000W saw for £99. That's a bargain. I've used one of these aluminium topped little table saws for years before upgrading to something more professional. If you are cutting a lot of panels or just slicing up offcuts for bracing a cab then they are way better than a circular saw. Set up carefully they can be very accurate but they are fiddly (I built windows and doors including all the tenons with my old one) and less repeatable than a pro bench saw. Lidl's are also doing corner clamps for £5.99 useful if you are about to build.

 

[RichardH]

You've got me excited about table saws now, Phil. However, I REALLY shouldn't be buying tools when we are expecting to move house in the near future. I checked Screwfix, and they actually have one for £109 - 1500W rather than 2000W, but it's comforting to know that it's possible to get something for not much more £££ than the LIdi special, so I really shouldn't rush in

Edited August 10, 2018 by RichardH

[Johnny Wishbone]

3 minutes ago, RichardH said:

You've got me excited about table saws now, Phil. However, I REALLY shouldn't be buying tools when we are expecting to move house in the near future. I checked Screwfix, and they actually have one for £109 - 1500W rather than 2000W, but it's comforting to know that it's possible to get something for not much more £££ than the LIdi special, so I really shouldn't rush in

That’s the one I have. Certainly got my money’s worth out of it!

[Johnny Wishbone]

Redundancy has its advantages - had some time between job searching to knock these together. Just need the drivers and then to construct and fit the front grilles.

Got the “black cab with coloured baffle” idea from a pair of Vanderkley cabs I was fortunate enough to borrow on a shared backline gig recently.

If I’m honest, these havent turned out as well as I’d have liked due to slightly inaccurate cutting (not by me). It’s not been a breeze to put them together as everything was slightly out of whack. Made the best of it with silicone sealant/caulk so hopefully they’ll work well enough to at least give me an impression of the sound/volume they’re capable of.

If I’m as impressed as I expect to be, it’s likely I’ll get my brother-in-law (a joiner) to knock me up a new pair that are actually 100% square and true. He has the advantage of proper tooling and a full workshop at his disposal, plus he obviously gets quality timber at trade prices.

At a glance they look pretty good - just don’t look too closely at the little details!

[JohnDaBass]

They look great Johnny, well done.

You'll be really happy with those fitted with Beymas.

Enjoy 

[Phil Starr]

Looking good, don't worry if everything is air tight they should work perfectly. I hope you like the way they sound.

[stewblack]

Just ordered my plywood to be cut up for me. I'm making two of these little babies but with an initial Stewblack Bodge ™.

Let me explain. Funds are tight, and I already have two 10" speakers. Sat in a shed. Not going to get to Dorset any time soon where @stevie kindly offered to measure the " T-S parameters " of my drivers for me so we could work out a cab designed for them. Therefore I'm going to make these cabs but with a 10" hole not 12" in the baffle. I know, I know these are scientifically designed to house 12" drivers but this is only a temporary measure. Once funds permit I propose buying the recommended speakers and making my hole bigger(!)

Then I can get my T-S perambulators measured up and make some 1 X 10 cabs too. Meantime my lust for building is slaked and my 10" drivers cease languishing. In a shed.

[Chienmortbb]

On 02/09/2018 at 22:30, stewblack said:

Just ordered my plywood to be cut up for me. I'm making two of these little babies but with an initial Stewblack Bodge ™.

Let me explain. Funds are tight, and I already have two 10" speakers. Sat in a shed. Not going to get to Dorset any time soon where @stevie kindly offered to measure the " T-S parameters " of my drivers for me so we could work out a cab designed for them. Therefore I'm going to make these cabs but with a 10" hole not 12" in the baffle. I know, I know these are scientifically designed to house 12" drivers but this is only a temporary measure. Once funds permit I propose buying the recommended speakers and making my hole bigger(!)

Then I can get my T-S perambulators measured up and make some 1 X 10 cabs too. Meantime my lust for building is slaked and my 10" drivers cease languishing. In a shed.

Sounds like a plan but go easy  on them drivers as they may well exceed their Xmax at medium to low volumes. litsen  for farting nopise and if there is no nasty smell it may be you driver exceeding its mechanical limits.

[stewblack]

3 hours ago, Chienmortbb said:

Sounds like a plan but go easy  on them drivers as they may well exceed their Xmax at medium to low volumes. litsen  for farting nopise and if there is no nasty smell it may be you driver exceeding its mechanical limits.

Ah - thank you for this, exactly the kind of advice I was hoping I'd receive. Would you say the idea was inherently flawed then? Is there a temporary solution? Reduce the volume of air in the box with a rolled up sweater or something?

[Phil Starr]

It depends upon the speakers entirely. I'm not sure if you are building the big 50l box or the smaller 30l one which is more likely to suit a random 10" speaker. Are they bass speakers or just some generic 10's?

The thing is that they will work, in that they will make a noise, you may even quite like the noise. Without getting too technical if the cab is too big to match the speaker you have you might get some nice deep bass but with a gradual roll off and reduced power handling, it's not uncommon to see power handling reduced to 25% of the rating at certain frequencies. If it is too small then you may not get a lot of deep bass but a boom boom upper bass with not a lot of definition. If you just want to have some fun then if you just play at home levels then power handling should be fine and you'll be able to play. I probably wouldn't want to gig with them in a rock band without knowing more about the speakers. Where in between those extremes they'll operate, well that's a gamble.

To be fair if it is a bass speaker or a PA speaker they tend to have broadly similar enough characteristics that a moderately sized cab tuned to 50Hz will kinda work, with the reservations on power handling.

A rolled up sweater wouldn't work anyway, you'd need something solid like a brick.

[stewblack]

11 hours ago, Phil Starr said:

It depends upon the speakers entirely. I'm not sure if you are building the big 50l box or the smaller 30l one which is more likely to suit a random 10" speaker. Are they bass speakers or just some generic 10's?

The thing is that they will work, in that they will make a noise, you may even quite like the noise. Without getting too technical if the cab is too big to match the speaker you have you might get some nice deep bass but with a gradual roll off and reduced power handling, it's not uncommon to see power handling reduced to 25% of the rating at certain frequencies. If it is too small then you may not get a lot of deep bass but a boom boom upper bass with not a lot of definition. If you just want to have some fun then if you just play at home levels then power handling should be fine and you'll be able to play. I probably wouldn't want to gig with them in a rock band without knowing more about the speakers. Where in between those extremes they'll operate, well that's a gamble.

To be fair if it is a bass speaker or a PA speaker they tend to have broadly similar enough characteristics that a moderately sized cab tuned to 50Hz will kinda work, with the reservations on power handling.

A rolled up sweater wouldn't work anyway, you'd need something solid like a brick.

Thanks Phil. I was planning on building the cab demonstrated at the SW Bash. The speakers are from a bass cab which was too darned awkward and heavy to lift comfortably so I thought I'd take it to bits it and use the parts. 

Maybe not such a great idea. Would the dimensions of the original cab tell me anything useful regarding what size two small cabs ought to be?

[Phil Starr]

Is that an old Peavey? Yeah if you measure the internal volume of the cab then  divide by the number of speakers that should give you the volume you are aiming at. If the original designers knew their stuff. If it's an old 4x10 you can even afford to blow a speaker, and cut up the grille for your new cabs

 

Remember this was a deliberately undersized (for the Beymas) cab to trim the bass response for difficult rooms, it may well be a decent match for your 10's and the 50Hz tuning may be OK too.

[Balcro]

Hi stewblack,

Phil Starr or Stevie can probably verify if this idea is acoustically practicable, but I think there may be an alternative to putting bricks inside the cabinet to reduce the volume. You could get hold of or scavenge some rigid polystyrene blocks ( packing pieces) such as these.

https://www.amazon.co.uk/Small-White-Polystyrene-Sheets-Boards/dp/B0164QUZN0/ref=sr_1_6/258-6901820-1773340?ie=UTF8&qid=1536417827&sr=8-6&keywords=polystyrene+blocks

If my maths are correct, each sheet takes up 6 litres. The average brick occupies about 1.75 litres so there's plenty of
scope to save weight.

Balcro.

Edited September 8, 2018 by Balcro
formatting

[stewblack]

56 minutes ago, Balcro said:

Hi stewblack,

Phil Starr or Stevie can probably verify if this idea is acoustically practicable, but I think there may be an alternative to putting bricks inside the cabinet to reduce the volume. You could get hold of or scavenge some rigid polystyrene blocks ( packing pieces) such as these.

https://www.amazon.co.uk/Small-White-Polystyrene-Sheets-Boards/dp/B0164QUZN0/ref=sr_1_6/258-6901820-1773340?ie=UTF8&qid=1536417827&sr=8-6&keywords=polystyrene+blocks

If my maths are correct, each sheet takes up 6 litres. The average brick occupies about 1.75 litres so there's plenty of
scope to save weight.

Balcro.

That is a great idea, thank you.

[Phil Starr]

Honestly I couldn't tell you how much difference that would make, polystyrene foam is air trapped in a plastic matrix much more air than plastic as you'll discover if you burn it (don't, the fumes are poisonous) It's a closed cell foam and relatively rigid but it will still transmit sound. More to the point is that you may not have a problem. have you measured the original cab yet?

[stewblack]

On 07/09/2018 at 13:27, Phil Starr said:

Is that an old Peavey? Yeah if you measure the internal volume of the cab then  divide by the number of speakers that should give you the volume you are aiming at. If the original designers knew their stuff. If it's an old 4x10 you can even afford to blow a speaker, and cut up the grille for your new cabs

 

Remember this was a deliberately undersized (for the Beymas) cab to trim the bass response for difficult rooms, it may well be a decent match for your 10's and the 50Hz tuning may be OK too.

Thanks Phil. The 2 10s came from an Epifani cab which I still have. I'll get the tape measure to it shortly, and let you know the results. 

[stewblack]

@Phil Starr

If my maths work the interior of the cab the two 10s came from is just shy of 64 litres.

[Phil Starr]

Then you are putting them into two cabs that will be spot on. My cabs are slightly over 30litres to allow for the volume of the speakers and the ports.

Are these from one of the dual impedance Epifani cabs?

Crack on and tell us what they sound like

[stewblack]

Not dual impedance, but I shall take the ply order off hold! Thanks for all your help Phil, I'll keep you posted.