Basschat easy-build lockdown cab project

[Stub Mandrel]

 

On 04/08/2021 at 12:33, Phil Starr said:

We are really happy to go off topic, lots of people read the answers and learn stuff and it keeps us on our toes for the next design.

 

As the design in this thread seems to have been 'finalised', is it too far off-topic if I ask a question?

 

I have two sets of elderly but still very usable 12" speakers (nominally 80W IIRC) that I haven't been able to get Theile Small parameters for. I used to use them as part of my rig in 2x12 cabs (one sealed, one with experimentally added and tuned ports).

 

Is there a way of estimating the most important theile-small parameters? Enough to make a pair of workable 1x12 monitors, including a reasonable stab at a sensible crossover frequency and tweeter.

 

I assume you can measure resonant frequency, Fs, just by tapping it gently while connected to an oscilloscope.

 

[nekomatic]

I’ve never tried doing it myself, but Rod Elliott has a guide

 

[Stub Mandrel]

6 minutes ago, nekomatic said:

I’ve never tried doing it myself, but Rod Elliott has a guide

 

 

That looks excellent. Once I have my workshop gear back I have everything needed to do that!

[FirstBass]

😁

[Stub Mandrel]

I don't see the cab dimensions anywhere, just that it is the same s th2 12" Easy build, but I went tro taht thread and there no easily found link to the dimensions of that either.

 

I do wish people would edit the first post to include a download of the dimensions 🙂

[Stub Mandrel]

Wait! - are these the dimensions for the easy build 10"?

 

They were in black on dark grey and hard to read* so first time I just assumed they were more text...

 

What are the port dimensions for the 10" version?

 

the panels for the cab are 2x 374mmx290mm, 2 450mmx 290mm and 2 450mmx350mm (all 12mm ply) the front baffle is set back 30mm to allow for the grille so internally the cab is 350mmx450mmx236mm. the ports are made of drainpipe/downpipe which is 64mm internal diameter 160mm long

 

 

 

*Yellow on blue is the most legible colour combination, if not the most pleasant.

Edited August 8, 2021 by Stub Mandrel

[Phil Starr]

 

The cab is essentially the same for both projects, there's a difference in the porting because I prefer the build simplicity of using downpipe which is so easy to get hold of. Stevie who designed the lockdown 10T prefers a bigger diameter (ooh err)

to reduce port noise. The dimensions are deliberately small to restrict the bass out put for the 12 but Stevie always said the cab would suit a 10. The tuning of the 12 is also slightly higher.

 

As to writing it all up properly, I agree but I already spend too long on bass chat and not enough time playing bass  I'll get on to it but it might take a while. 

[Phil Starr]

On 20/03/2021 at 08:26, Phil Starr said:

And now the drawings, big thanks to @RichardH who did all the hard work, nb the port is 170mm and 100mm internal diameter. We hadn't settled on this when these drawings were made

BC 110 T.pdf 631.1 kB · 34 downloads

 

here's the drawings of the 10.

[Stub Mandrel]

Thanks, Phil!

[Stub Mandrel]

Would it make a significant difference if I dowelled the boards together so I could leave out the battens to save weight?

[Chienmortbb]

On 08/08/2021 at 21:07, Stub Mandrel said:

Would it make a significant difference if I dowelled the boards together so I could leave out the battens to save weight?

None at all. Phil's philosophy is to use battens so that is is a simple build for those with basic tools. Using dowels should be OK but be careful that you use enough adhesive to make an airtight seal.

[JohnDaBass]

30 minutes ago, Chienmortbb said:

None at all. Phil's philosophy is to use battens so that is is a simple build for those with basic tools. Using dowels should be OK but be careful that you use enough adhesive to make an airtight seal.

+1

And ensure that you have 90 degree joints. The benefit of the battens is two fold, good 90 degree strong joints and additional strength for fixing feet screws into thin wall cabs.

I'm confident that Phil has built quite a number of cabs so we avoid going through the same "learning curve" that Phil has experienced.  

[Phil Starr]

On 08/08/2021 at 21:07, Stub Mandrel said:

Would it make a significant difference if I dowelled the boards together so I could leave out the battens to save weight?

The big advantage of building your own is that it opens up choices, a difference yes, a significant difference? Well probably not.

 

John's right, the reason I've used this method is that it is the easiest by a distance and probably the strongest. It's also really quick. The only tool you need to build the basic box is a screwdriver, any other method needs extensive clamping whilst the glue sets. Technically the joint is a reinforced butt joint and the main aim is to increase the glued area, all the screws do is hold the battens in place whist the glue dries. There is also a sonic advantage; the butts transfer energy across adjacent panels and help a little with panel damping. If you remove the battens you should probably look at other methods of transferring energy between panels but internal braces should do that and almost always using less material.

 

If you are a competent woodworker though there are loads of other methods you can use. Dovetail and finger joints will also double the glued area and hold panels in place with minimal clamping needed, dowels certainly help with lining everything up and a well made simple butt jointed cab is still a fairly strong structure. My method is for those without a lot of woodworking tools and less confident of their skills. the important thing is that you are comfortable with whatever you choose.

[RichardH]

....and given the size of the cab, I can't see the battens adding much more than a few ounces....

[Stub Mandrel]

I really like using dowelled construction and have the jigs/experience of using them. Inclined to think it would definitely be best to use ply rather than mdf if going that way.

 

A three bar internal cross brace would use a quarter as much timber and would greatly increase the stiffness of each panel.

Edited August 12, 2021 by Stub Mandrel

[Phil Starr]

That all sounds perfectly sensible. The only minor issue is that you will be changing the internal volume slightly and that could throw the tuning out a tiny bit, but that is all fixable if it proves to be a problem.

[FirstBass]

Quick update

 

Played through both my scrap ply cabs at the weekend

 

Loud glam rock band (heavy drummer) 

 

Social Club environment - room probably 25m x 25m ish. Quite a low ceiling.  

 

Coped admirably with my TC BH550. A little bit of compression and very little twiddling of the volume control

 

Again, droppped lows and low/mids a little on the EQ

 

Still can't believe the bass output from 10" drivers in 30l cabs

 

Top cab with tweeter on, bottom with tweeter off

 

Had been a bit peeved about the lack of brightness, but thought it was just me...

 

Changed my strings yesterday (owned the bass 10+ years and never changed them 😲) 

 

BINGO!

 

Clear as a bell

 

Still wondering what to do grille wise. I like the silver fabric grille, but i don't think it affords the protection the drivers need. 

 

If you're still umming and aaahing about having a go... DO IT!

 

Once again thanks to all contributors 👍

 

 

[Phil Starr]

I've recently fitted this to a guitar cab Amp grill cloth - Marshall style - Bluesbreaker Re-issue - 33" wide (p – Allparts UK it's very substantial, Actually quite difficult to stretch over the frame but affords great protection. There's a Chinese supplier that is a lot cheaper and I found mine from another UK supplier a bit cheaper but they have sold out.

 

I've also recently tried some of the 'American Style' grille cloths which are great, they shrink when heated which makes them so much easier to fit.

 

Alternatively try Speaker Grills for metal grills

[Chienmortbb]

9 hours ago, Phil Starr said:

I've recently fitted this to a guitar cab Amp grill cloth - Marshall style - Bluesbreaker Re-issue - 33" wide (p – Allparts UK it's very substantial, Actually quite difficult to stretch over the frame but affords great protection. There's a Chinese supplier that is a lot cheaper and I found mine from another UK supplier a bit cheaper but they have sold out.

 

I've also recently tried some of the 'American Style' grille cloths which are great, they shrink when heated which makes them so much easier to fit.

 

Alternatively try Speaker Grills for metal grills

When you say "American Style", is that as in Fender Style or Ampeg Style from Allparts?

[Phil Starr]

Without trying all the cloths from all the suppliers I can't be certain John. I found out by accident when I warmed a piece of cloth to soften and stretch it and it contracted instead! I now have a piece just too small to fit  since then I've seen a couple of YouTube video's confirming this all on fender style cloths. The Chinese suppliers list the cloths as 'American Style' and the patterns match the Allparts patterns exactly so I assume they are manufactured in China. My guitarist wanted a cab with the Marshall Salt and Pepper cloth and that is a much stiffer fabric which chars but doesn't contract when heated. Fortunately I tested an off-cut before fitting that time.

 

The Marshall fabric is listed separately by the Chinese as 'British Style' so i'm assuming it's a different weave until I know otherwise. I'm considering ordering a roll of fabric from them as a trial once I've had a go with a few samples. It's really sad that none of the UK mills seem to be supplying any good quality fabric. In the years when I built speakers for a living back in the 70's I had a wide choice of suppliers. I can only find a wide choice in the US and China now or pay the high prices that Allparts charge

[RichardH]

Yes, the Fender style cloths shrink when heated (be careful to not get too excited with a heat gun though, as they will melt!). Key is to fit it as tightly as you can then heat gently and evenly so the weave stays aligned nicely.

 

[Dan Dare]

On 08/08/2021 at 21:07, Stub Mandrel said:

Would it make a significant difference if I dowelled the boards together so I could leave out the battens to save weight?

 

I like to screw/glue boards together and, when the glue is dry, remove the screws, drill out the holes and dowel them. It saves destroying router bits and tools when you radius the edges. It also means you can sand the surface really flat and smooth for paint or tolex.

[Dan Dare]

5 minutes ago, Dan Dare said:

 

I like to screw/glue boards together and, when the glue is dry, remove the screws, drill out the holes and dowel them. It saves destroying router bits and tools when you radius the edges. It saves clamping and also means you can sand the surface really flat and smooth for paint or tolex.

Don't know why this posted twice...

Edited August 17, 2021 by Dan Dare

[stevie]

Gluing and screwing is a great technique that can do away with the need to use (buy) clamps. If you get the right size of screws, you can remove them and just tap a bit of matchstick in the hole with a dab of PVA. It's more work than clamps (as you still need to fill and sand over the holes) but it can work very well.

[Finbar]

I am very tempted to give this a go. Having a (relatively cheap) neat little project with something to show at the end of it sounds good to me. I'm looking at getting into a semi-permanent practice room with my band now that we're getting into a post-covid world, and I would really like to have a cab to leave there!

 

For me, the main obstacle is that I'm a total cack-handed beginner to all of this stuff. And I mean a total beginner. I'm also not interested in frequency response graphs, tuning my ports etc. Just be nice to have something that works. I've read through the thread and I'm still feeling like there are things I don't understand - I've never read or implemented a wiring diagram in my life, for instance, even if it is the simplest solder free diagram! Even understanding exactly the right components I need is a little hard for me. While I get the gist of it, I think it'll take some trial and error on my part

 

I think it's likely that there are more people in the same situation as me, so if I do end up going for this, I'll probably try and put together an "Explain it like I'm 5" style shopping list with links and everything as part of the diary. Would that be helpful?

Edited August 18, 2021 by Finbar