1x12 DIY Cab build

[6v6]

Hi all - starting this build thread as a follow-up to the discussions prompted by my Which Ceramic 12 inch driver thread (link : [url="http://basschat.co.uk/topic/199000-which-ceramic-12-driver"]http://basschat.co.u...ramic-12-driver)[/url]

Suffice to say I got a lot of really great information from that thread, not just a driver recommendation, and I've started getting to grips with modelling driver+enclosure using WinISD Pro (link: [url="http://www.linearteam.dk/default.aspx?pageid=winisdpro"]http://www.lineartea...ageid=winisdpro[/url])

I've now ordered a Beyma SM212 12" driver, which should arrive in the next few days, by which time I hope to have figured out cabinet dimensions & port tuning such that I can get some ply and build up a box! (link: [url="http://profesional.beyma.com/pdf/SM-212E.pdf"]http://profesional.b...pdf/SM-212E.pdf[/url])

I'll post the process of designing the box in WinISD, with graphs and details, in the hope that some of the experts contributing their knowledge to the original thread will point out all my mistakes, and hopefully this may also prove useful to other novice bass-cab-builders like me

So far my experiments with WinISD lead me to think a box of about 70L volume, with a shelf port tuned for about 50Hz should work OK, I'll post some charts for this configuration later & perhaps the experts can advise if I'm way off base

[nugget]

This will be intereseting. Been thinking about making a couple of BFM Jack 12's but the overall cost is putting me off right now.

[Phil Starr]

It's great to see this going ahead. I hope you are pleased with the result.

[6v6]

[quote name='Phil Starr' timestamp='1361291322' post='1984032']
It's great to see this going ahead. I hope you are pleased with the result.
[/quote]

Thanks again for all your assistance in the original thread!

So here's my first attempt at producing some specs for the box via WinISD, I loaded the driver T/S specs and created a QB3 ported enclosure, which resulted in a plot for a box of ~111L tuned to 42Hz.

I'm looking for a smaller box than 111L ideally, so I experimented with box size and tuning, eventually settling on a compromise of 70L tuned to 50Hz - this appears to be a reasonable tradeoff between losing low-end extension and introducing a big peak from the port (which I assume will make the cab boomy?)

Anyway, here's the plot - I'm currently thinking the yellow plot looks pretty good - not hi-fi flat but looks (based on some limited mixing experience eqing stuff) like it should give me a modest boost in the low end, but still produce a fairly even an eq-able response?

[6v6]

Next thing I checked was the power handling, since Mr. Foxen pointed out these charts are informative in the driver reccomendation thread, and it's clear that the xmax limted power handling is directly related to the box size and tuning:

Again, the 70L/50Hz yellow plot seems to be a pretty good compromise to me, and should handle the amps I expect to use with the cab (something like a LM3 or PF500 which produces about 300w into 8ohms):

[Phil Starr]

Hi, the easiest responses to eq are the ones without a hump and a long slow tail off so the pink (I'm colour blind) plot might be better to eq. Having said that there are no problems with any of these.

Looking at excursion limited power you can see the advantage in a smaller cab. Remember you are dealing with Xmax, which is kind of worse case. If you used method for calculating Xmax used by Eminence then this speaker would come in with an Xmax of about 10mm and the power handling would look even better. Beyma quote a maximum Xdamage of 27mm peak to peak or Xlimit 13.5mm. Have a look at the cone excursion charts on your models. You should find you only exceed these limits at very low frequencies. Almost all ported designs operate better with a LF filter on the amp. Eminence specify them on most of the designs on their web site. I always use a 40Hz filter on the mixing desk even on the bass bins.

I quite like shelf ports, they help stiffen the cab, take up minimum space and are easy to construct, the advantage of a circular port like a drainpipe is that you can vary the tuning simply by sliding in a different length port so you could try both the 50 and 42Hz tunings to see if you can hear a difference and if it is important to you. Not much would be my guess.

Anyway nothing to stop you finalising a design and getting the saw out. Looking good.

[6v6]

[quote name='Phil Starr' timestamp='1361348380' post='1984763']
Hi, the easiest responses to eq are the ones without a hump and a long slow tail off so the pink (I'm colour blind) plot might be better to eq. Having said that there are no problems with any of these.

Looking at excursion limited power you can see the advantage in a smaller cab. Remember you are dealing with Xmax, which is kind of worse case. If you used method for calculating Xmax used by Eminence then this speaker would come in with an Xmax of about 10mm and the power handling would look even better. Beyma quote a maximum Xdamage of 27mm peak to peak or Xlimit 13.5mm. Have a look at the cone excursion charts on your models. You should find you only exceed these limits at very low frequencies. Almost all ported designs operate better with a LF filter on the amp. Eminence specify them on most of the designs on their web site. I always use a 40Hz filter on the mixing desk even on the bass bins.
[/quote]

Thanks, I'm assuming most amps will have this built in rather than being something I need to build in to the speaker as a high-pass filter network? (I was, at least initially, planning to not fit a tweeter so I can concentrate on getting the box+woofer right and not worry about crossover design, thinking I can always add a tweeter+crossover later if needed)

[quote name='Phil Starr' timestamp='1361348380' post='1984763']
I quite like shelf ports, they help stiffen the cab, take up minimum space and are easy to construct, the advantage of a circular port like a drainpipe is that you can vary the tuning simply by sliding in a different length port so you could try both the 50 and 42Hz tunings to see if you can hear a difference and if it is important to you. Not much would be my guess.

Anyway nothing to stop you finalising a design and getting the saw out. Looking good.
[/quote]

Cool, thanks for the feedback!

I've done some more plots focussing on the 70L box size, experimenting with some different tuning frequencies to see what effect it has on the port length. Using an example port dimension of 35x6cm (which seems about right for my planned box dimensions), it seems like the port length is not super-critical - even changing it by as much as 5cm only makes a few Hz difference to the port tuning frequency.

I plotted them all together, tunings of 44, 46 and 49Hz result in a port length of approximately 25, 30 and 34cm respectively, so it seems like I could build say a fixed 26cm port into the box, then potentially have a couple of removable sections of say 4 and 8cm, then experiment with them, see if I can hear the difference then glue the one I prefer in when decided?

[Phil Starr]

sounds like a plan though as you can see from the plots it isn't likely to be something you can hear very well, if at all. The only practical way to filter out sound below 30Hz (say) is to do it electronically in the amplifier. It'd be nic e if this were built in explicitly and switchable but this is rare in bass amps though all my PA amps have switchable subsonic filters as does my mixing desk. I'd not thought of this before but given most bassists use ported cabs it really ought to be standard.

[Phil Starr]

Any news of your Beyma yet?

[6v6]

[quote name='Phil Starr' timestamp='1363165254' post='2009341']
Any news of your Beyma yet?
[/quote]

Sorry, been away for a few days so not got around to updating this thread yet!

I now have the driver (great service from LMC audio, next-day delivery from stock!), and I think I've finalized the cab design (will post plots and my dimensions spreadsheet later)

Found a local supplier of birch plywood, planning to get some in the next few days so I can build the cab.

Currently trying to decide:

- 15mm or 18mm ply? (I'm thinking 15mm should be fine for a 1x12 box?)
- Biscuit joints or proper finger/dovetail (biscuit joints should be fine I think, and will be much much quicker to make)

[Phil Starr]

If you are going to brace then 15 should be fine. FWIW i use reinforced butt joints. 1" batten along all the joints. This means you can use screws and glue it stiffens the cab a little and you can keep one panel removable. Don't forget to recess the baffle so you can get a grill over the front of the speaker. the cab needs to be airtight so it isn't a bad idea to go round with a mastic gun after the cab is built. The easiest and lightest bracing is broomhandle dowel across opposite panels avoiding the dead centre, which shifts the resonance up an octave without spreading it.

Good luck

[6v6]

Plot and proposed final dimensions, any comments before I get the saw out?

[Phil Starr]

this all looks fine to me. Hope it sounds good to you, I can't wait to hear what you think of the result.

[mrtcat]

Use an expanding polyurethane adhesive on joints like [url="http://www.thegluepeople.co.uk/index.php?main_page=product_info&cPath=6_10&products_id=32&zenid=eb476bfa4277441aac98b88311df3aa5"]http://www.thegluepeople.co.uk/index.php?main_page=product_info&cPath=6_10&products_id=32&zenid=eb476bfa4277441aac98b88311df3aa5[/url]
It will fill any gaps so not only will it allow for slight imperfections in cutting it will also leave the cab airtight. You'll find its stronger than the ply when it's set too. I've built 100s of cabs this way. As long as you don't use inferior ply with a thin veneer layer even butt joints will be really strong. If it helps you can use screws to hold parts in place while adhesive sets. Once set remove the screws and use more adhesive to fill holes leaving them airtight.
Good luck with the build. I look forward to seeing the end result.

[shaneybaby]

fair play for being able to use WIN ISD. the most confusing program ever concieved

[6v6]

[quote name='Phil Starr' timestamp='1364151740' post='2022587']
this all looks fine to me. Hope it sounds good to you, I can't wait to hear what you think of the result.
[/quote]

I can't wait to hear the end result!

Thanks for all the assistance getting to this point, hopefully have it put together in the next week or so!

[6v6]

[quote name='shaneybaby' timestamp='1364159117' post='2022748']
fair play for being able to use WIN ISD. the most confusing program ever concieved
[/quote]

Really? I'd never used it before, and (apart from entering the driver parameters, which definitely was confusing due to all the auto-calculated fields) I've found it pretty easy - just enter the box volume, tuning frequency and vent dimensions, play with the numbers until you're happy with the plot.

Admittedly I still only have a fairly vague idea what constitutes a "good" plot, and I've only really considered frequency response and power handling graphs, but overall I've encountered much more confusing programs (LTSpice springs immediately to mind..)

[paul_5]

shame there's nothing like that for mac.

[6v6]

[quote name='mrtcat' timestamp='1364154525' post='2022648']
Use an expanding polyurethane adhesive on joints like [url="http://www.thegluepeople.co.uk/index.php?main_page=product_info&cPath=6_10&products_id=32&zenid=eb476bfa4277441aac98b88311df3aa5"]http://www.thegluepe...c98b88311df3aa5[/url]
It will fill any gaps so not only will it allow for slight imperfections in cutting it will also leave the cab airtight. You'll find its stronger than the ply when it's set too. I've built 100s of cabs this way. As long as you don't use inferior ply with a thin veneer layer even butt joints will be really strong. If it helps you can use screws to hold parts in place while adhesive sets. Once set remove the screws and use more adhesive to fill holes leaving them airtight.
Good luck with the build. I look forward to seeing the end result.
[/quote]

Thanks for this - I was planning to use some good quality PVA, but this looks like a good alternative.

Planning to use butt joints reinforced with hardwood biscuits (I already have a biscuit joint attachment for my router), clamped and/or screwed tight, hopefully should end up pretty strong and much quicker to build than proper finger/dovetail joints (I have a dovetail jig but it's too small for this cab size)

[6v6]

[quote name='paul_5' timestamp='1364204780' post='2023014']
shame there's nothing like that for mac.
[/quote]

You can run it on a Mac using either Windows/Linux dual-boot, a windows (or Linux) Virtual Machine, or using a windows emulator such as Wine (I run win ISD pro alpha under wine on Fedora, a Linux distribution, it works fine)

http://www.winehq.org/
http://www.codeweavers.com/
http://winebottler.kronenberg.org/
http://wiki.winehq.org/MacOSX (appears to be down atm)
http://www.davidbaumgold.com/tutorials/wine-mac/
http://fedoraproject.org/

[Phil Starr]

PVA should be perfectly adequate for your cab. I've been using it since 1970 with no problems. It is probably used in 99% of commecial cabs. Polyurethane glues are great if you want a waterproof glue but even with handsaw cut butt joints PVA is perfectly good unless you really are ham fisted. Any wood glue is going to be stronger than the wood if properly applied.

[mrtcat]

[quote name='Phil Starr' timestamp='1364206770' post='2023061']
Polyurethane glues are great if you want a waterproof glue but even with handsaw cut butt joints PVA is perfectly good unless you really are ham fisted.
[/quote]

Agree to a point bit the advantage of polyurethane isn't really about being waterproof or stronger . It will give an airtight seal without the need for additional sealant. PVA glue rarely gives a true airtight seal even with cnc cut ply as it actually contracts a little as it cures. Even with ported cabs, the smallest air leaks can affect performance. There's nothing wrong with PVA at all but it will need a sealant bead as well.

Edited March 29, 2013 by mrtcat

[discreet]

[quote name='mrtcat' timestamp='1364562600' post='2028195']
There's nothing wrong with PVA at all but it will need a sealant bead as well.
[/quote]

This. PU adhesive increases massively in volume as it cures, thus providing an impermeable seal.
I wouldn't build a cab with anything else.

Edited March 29, 2013 by discreet

[Phil Starr]

[quote name='mrtcat' timestamp='1364562600' post='2028195']
Agree to a point bit the advantage of polyurethane isn't really about being waterproof or stronger . It will give an airtight seal without the need for additional sealant. PVA glue rarely gives a true airtight seal even with cnc cut ply as it actually contracts a little as it cures. Even with ported cabs, the smallest air leaks can affect performance. There's nothing wrong with PVA at all but it will need a sealant bead as well.
[/quote]

I don't suppose 6V6 want's a big debate about glue but I've designed and built cabs, including professionally for years and I'm also a joiner. Make the joint good and put in enough glue to ooze out when you clamp it and it will form a seal. You won't see polyurethane glue in any commercial cabs, some of the American manufacturers may use Aliphatic glues but everyone else uses PVA. Polyurethane fills gaps because it foams, This means it is no more likely to seal air gaps than PVA as the foamed bits will leak so you should still run a sealant bead. My experience is that the foam is weak and will break easily when stressed, though the glue is perfectly strong when compressed in a well made joint. I really strongly doubt that the choice of glue will adversely affect the eventual build but PVA will do a marginally better job, is cheaper and a lot less messy to work with.

[Kiwi]

Foam is structurally pretty strong given the surface area. I've had expanding poly glue recommended to me by joiners as top flight stuff. PVA does contract when it dries and it also swells the wood because its water based. PVA is cheap so it wouldn't surprise me that its being used a lot by US cab manufacturers! If it was me, I'd be running a bead with both glues.