stevie

Oh, and another (even more important) reason why an adjustable attenuator is not a good idea is that our crossover rolls the bass unit off fairly steeply at 2kHz. On almost every other bass cab (with very few exceptions), the bass unit is not connected to the crossover; it just carries on happily as high as it can. If there is a tweeter, it is added at a relatively high frequency - usually about 5kHz, which is too high to be much use - and protected by a cap and a coil. So when you attenuate the tweeter, you get the sound of the bass/mid driver on its own.

Yes, that is certainly possible. There will probably be a fixed-value L-pad on the crossover (2 resistors connected to the HF unit). You could replace those with an 8-ohm L-pad attenuator. If you wish, I can provide more precise instructions once the finished crossover is ready. However, I don't like L-pads on speakers. And I'll tell you why. - First, it's one more thing to go wrong - and L-pads aren't nearly as reliable as wirewound resistors. - When you rely on an L-pad for attentuation, you have no idea what is flat. The 12 o'clock setting means absolutely nothing. If the frequency response is not flat, the phase of the crossover will be out. That means dips (and peaks) in the response, especially off-axis. - This particular design measures as flat as a very expensive studio monitor. Why would you want to compromise that when you can roll the top off with the tone controls on your amp or bass? When was the last time you saw an L-pad attenuator on a studio monitor, or a hi-fi speaker? About 50 years ago. - Finally, from what I can gather, most people attenuate the HF unit on their cabs because it doesn't sound very good. I can understand that, but that's certainly not the case with this cab. The HF is not strident, edgy or honky. Your P-Bass with flats will sound like a P-Bass with flats, and if you want a more old-school sound turn the treble down on your amp or use the tone control knob on your bass. You are entitled to disagree with all of this, and if you'd really like to fit an HF attenuator, I'm happy to provide the details. It's not a difficult job.

Err, yes, you're right, although I don't think that would bother most saw operators.

You could try Duchy Timber: <http://www.duchytimber.co.uk/our-products/sustainable-sheet-material/> They're part of the Premier Forest Group: <http://www.premierforest.co.uk/premier_forest_products_products.htm> who definitely sell poplar plywood. So if Duchy haven't got it in stock, they should be able to order you a sheet. Try to get Italian or Spanish rather than Chinese. Your local wood merchant should be able to order you a sheet too. A lot of wood merchants will cut the sheet up for you for a small fee. Not only will that save you a lot of time and effort, it'll make the wood easier to transport home. Just give them the cutting list in the PDF with the drawings.

Thanks for your kind words, rc. The cabinet design is finished - so you can start cutting as soon as you like from the plans in the thread. The crossover is still being tweaked, however. Once I've finished the crossover to my satisfaction, I'll post a list of parts and components you'll need to complete your cab. I'm struggling to find a company that will supply small quantities of badges for the front grille at a reasonable cost - say a fiver or less. Can anyone help?

And your design goals were?

Exactly. I think the bass guitar has suffered for many years from being confused with the electric guitar, where the speaker plays an important role in creating the sound. A bass guitar isn't like that. It's more like an electric piano or a double bass.

No, I'm afraid not.

During the past few years of messing about with bass cabs, I've come to the conclusion that a flat response, low colouration, constant directivity cab is the best solution for bass - certainly for me - and not just for use with modellers.

You might as well run your bass through the earbuds on your phone.

Yes. When they are positioned close to one another, multiple speakers couple at low frequencies (they act as a single driver) and sensitivity increases. This is fine at very low frequencies where wavelengths are long, but at higher frequencies the sound produced by the individual drivers will start to cancel (be out of phase) as a result of the inter-driver spacing. It's the same principle that causes a single driver to roll off off-axis. To avoid this when multiple bass drivers are used, they should be crossed over to a midrange driver before the phase cancellation takes place.

Basically, yes. There's very little actual design input in these cabs. The basic principle is - keep sticking drivers in a box until it's loud enough. With multiple drivers you get lots of midrange cancellation, which results in peaks and dips in the frequency response. The off-axis response is hopeless and there is usually no HF. When a tweeter is fitted, it usually operates too high to make any real difference.

The only bass guitar cab I know that has half a chance of being neutral is the Greenboy F-series. Apart from that, your best bet at the moment is a PA cab. It's impossible for your usual 2 x 10 and 4 x 10 bass cabs to be neutral.

Exactly right, Luke. The idea behind building the prototype cab was to discover what bracing was needed - so it was a bit belt and braces. Surprisingly, the spruce ply in that cab tended to ring more than the poplar ply we're using now. This is an ongoing project for me, which means I may revisit the bracing configuration at some future time, but I think what we have now is a good balance between bracing performance and complexity.

The drawing assumes the use of the original handle I used in my cab, which is a Marshall-type strap handle, but builders can of course choose whatever handle they prefer. The flat packs will have the round handle because it offers a number of advantages that I think owners will appreciate. For those rolling their own who wish to use the round handle – bracing for the top panel is a ring of plywood 35mm wide with a centre hole the same diameter as the hole for the handle. This arrangement not only stiffens the top panel but it also means that the handle bolts are fixed to 30mmm of plywood. The ring can be cut from the circular piece of wood left over from cutting the hole for the main driver.

Oh Canada? 😀 Otherwise, yes, very useful.

Yup. It's the cutout from the port. It doubles the thickness of the cabinet at its weakest point, which is at the centre. I have that arrangement in my own cab and it works really well. It's also very easy to do.

I'm pleased someone has a great eye for detail.

The drawings are now with my CNC flat pack supplier. Fingers crossed.

While that's true, it's not quite so easy for the average pub-type band. They often don't have any bass in the monitors and it can be hard to hear your bass clearly unless the cab's at ear level.

Two G braces in the cutting list?

Here are the drawings and cutting list. A big thank-you to RichardH (and Ghostbass) for doing these. I still have a bit more tweaking to do to the crossover - nothing major - and we'll add the final crossover to the PDF soon. BC112-v3 drawings v 4.pdf

It's likely to be the Faital 12PR300, but there's no getting round opening the cab up to take a look. The driver is readily available from a couple of suppliers in the UK, which is fortunate. That's an unusual fault, as I'd expect the clicking to get worse as the volume increases. It might not be the driver. So make sure you check for loose cables, screws, etc. and see if the problem occurs outside the cab (at a low volume, of course).

For me, the floating thumb is a more natural technique than the moveable anchor - nothing to do with playing faster or anything like that - because you don't have to think about it: the thumb is always there, doing its damping job. It sounds like it might be a personal preference thing.

Yes, that's the floating thumb. (I really hate to disagree with TKenrick, who is a proper bass player, while I am and will remain strictly an amateur).