stevie

Standing waves certainly exist in loudspeaker cabs and most good designers spend time trying to minimise them. Some go to extreme lengths trying to try to get rid of them. They are particularly problematic in tall, hi-fi cabs, where standing waves occur at frequencies around 200 to 300Hz. There are a number of different ways that a designer can measure them. Dealing with them is more tricky. A typical bass cab isn't exactly small, and they tend to suffer from standing waves between 170 and 300Hz. These are critical frequencies for bass guitar and will colour the sound unless some steps are taken to keep them under control. I've found that felt is quite good at taming standing waves and flutter echos inside cabinets. It's also fairly cheap. Place more damping material at the end of the longest dimension of the cabinet because that's where the biggest problem is.

I thought it was great. Very professional but relaxed and informal. The teacher's personality came across well. He wasn't annoying (important!) and can clearly play a bit. Looking forward to your bass efforts. Well done!

Sorry, Stew, I should have been clearer. It's bitumen damping material used for sound deadening. Dynamat is a well-known brand. I happened to have some bitumen roof flashing in my garage and used that. It's not a critical component but the more fastidious amongst us will want to damp the thin plastic of the handle. By the way, the cab I now have is as dead as a doornail when you knuckle-rap it - a noticeable improvement on the previous one. The only difference between the two is that the braces are now inset into the panels whereas previously they just used butt joints. I've tuned the port and finished the crossover. I won't bore anyone with more frequency response curves - but draw a line with a ruler and that's what we've got. Off axis response is also exemplary.

That's a shame. It's such a great body of work. A pity it's not complete, but there's still plenty to be getting on with.

You're right, Ricky. I've just checked my hard disk and I don't have them. I'll check my laptop later today, but I think they might be lost for all time - unless someone else has saved them. The Major hasn't posted on here for years. I often wonder what happened to him. Retired maybe?

I've added a parts list to the very first post in this thread - and have taken the opportunity to delete the old drawings, which are now out of date. I'll post drawings of the latest version shortly.

This is a great way to get a great sound at minimum cost. This is going to sound fantastic! I'm intrigued to find out how you solve the port problem.

The cab is now connected up to my measurement system and I'll finalise the crossover at the weekend. The preliminary design I did last week is pretty close - so that shouldn't take too long at all. I'm also contacting CNC companies to see who can produce these kits for us at a reasonable cost. I'll report back when I have some news.

And this is how it's wired up. All the terminals are pre-fitted - you just need to push them on to the appropriate tags.

Here is the crossover with the cables connected. There is a terminal block on the crossover board with a label that shows exactly where each wire goes (it's a bit difficult to see from the photo, but trust me). Just insert the fork terminals into the appropriate connector on the terminal block and tighten the screws, as I've done here.

The final thing you need to do is to even out imperfections at the joints. I discovered a really useful, water-based wood filler from Everbuild that I used for this. It's not as tough as a two-part filler - so don't use it to fill chips in corners - but it's ideal for this kind of job. It dries in half an hour and sands really easily. Then hardens over time. Now you can paint the cab. I haven't shown the batten used for fixing the grille because I haven't got any at the moment. But it's not rocket science, and I will probably mention it when I get the grilles sorted out. I'm leaving my cab unpainted for the moment because I have to tune the port and tweak the crossover. But your next job when the paint has dried is to wire the drive units up. Ooooooh!

You now need to round off the corners. To prevent sawdust getting into the cabinet, it would be best to do this before painting the baffle and installing the wadding. But we wanted to keep the top of the cab open - so we're going to have to do it now. It would be a good idea to cut a piece of cardboard to place over the baffle. Because poplar plywood is relatively soft, you don't need a router for this job. An orbital sander is fine, finishing off by hand. You could even do it all by hand if you don't have a sander. The trick is to get the round edge of the cabinet to match your metal corners. It doesn't need to be perfect - it will look fine when it's painted, honestly. Remember to sand off each corner so that your metal corners fit.

This is where we are now. It didn't take long, did it?

You can give the front baffle a coat of blackboard paint now. You could, of course use Tuffcab paint, but I prefer to have a baffle that's matt black. You don't need to paint right to the edge, as you will be fitting some batten all round the outside of the baffle later. While the paint's drying, fit the top handle. It will have to come off later for painting, but it'll make it easier to carry the cab around for the time being. I stuck some bitumen damping material on the back of mine. If you have something suitable, you could do the same. This isn't the kind of touch you see in commercial cabs, but that's one of the reasons why we're building our own (isn't it?). By the way, the handle will need foam strip. You don't need to do it now but don't forget to do it later. I'm using woodscrews on mine, because six woodscrews into 30mm of plywood are not going anywhere - especially given the weight of the cab. You can, if you prefer, use t-nuts and machine screws. Up to you.

Cut a piece of felt to fit in a U shape on the bottom up to the lower braces on each side. Spray one side of the felt, leave for 30 seconds and glue in. Then glue a second layer on the bottom panel (but not up the walls). Carry on with the rest of the cabinet until you reach the top. Do not glue any material on the back panel above the top brace, except on the side panel as shown. There mustn't be any damping material near the port. It's much more convenient to do all of this before glueing the top on. You could connect the wires to the crossover now if you like, but it's no real problem to do it later. Now you can glue the top panel on and admire your work.🙂

Next up is damping. I suggest you use needled felt for this.A square metre - available for a fiver on Ebay is the best damping material I've found. The photo shows what you'll need. The contact adhesive is available from Screwfix but you could also use Evostick from a can if you prefer, although the spray is much more convenient.

Your cab should now be looking something like this:

As promised, here are some details on fitting the cab out. We've already gone through the assembly process, but just before you glue the top panel in, don't forget to paint behind the port with some matt black paint. Then drill the holes for the crossover. It's much easier to do with the top off. You could also screw the crossover in now, but it fits through the horn opening - so you could do that later if you like.

This is a wind-up, isn't it?🙂

I remember asking a well-respected pro player about the one-finger-per-fret thing a long time ago, and he said that's what you should do. So even the experts disagree. It might have been all right for him, but I've been a lot happier since I reverted to using 1-2-4 in the lower positions. If you've got small hands, you should definitely give it a go.

Composing pm now......

It's fine, guys. I didn't want to post anything until I had something worth posting about. There has been a bit of a deadly silence over the past weeks, I admit. Unfortunately, a lot of the stuff that remains to be done depends on having a finished box, and the delays and pink torpedo-ups made by my CNC supplier has made that impossible until now. Still, I'm hoping to pull all the threads together next week. Watch this space. I do appreciate everyone's patience.

As far as progress is concerned, it's been a case of two steps forward and one step back. The good news is that I've assembled a CNC cabinet and taken photos showing how to fit it out. It's relatively straightforward and I'll list all the parts you'll need. I'm working all of today and tomorrow, but will post the photos in a few days' time. Next week, I'll also finalise the port tuning, fine tune the crossover (the PCB is already laid out) and send the final changes to Richard so that he can produce a final technical drawing. The step back (and the reason why it's taking so long) is that my CNC person has proved to be less than reliable on a number of fronts. Which is a shame, because he was within a short driving distance. Without going into too much gory detail, I'm going to have to find another CNC company. That's another job for next week. On the positive side, we do have a CNC file that (hopefully) just needs a bit of tweaking to get us back in business again. I'm sorry it's not progressing as quickly as we'd all like - but we will get there in the end. The last thing I want is for everyone to receive a cabinet kit that cannot be assembled because the CNC company was sloppy - or because the design wasn't checked properly before putting it into production.

There isn't really anything you need to buy in advance, as all the components are available at short notice. So just start shopping when you know your kit is imminent. The only exception would be if you want to get the corners I am using (take a look at the finished cab). I like them because they are discreet and made of metal. They are also a bit cheaper than other metal corners, but you'll have to order them from China via Ebay. <https://www.ebay.co.uk/itm/8Pcs-90-Hard-Steel-Guitar-Amp-Amplifier-Audio-Speaker-Cabinet-Corners-Protector/263655998126?hash=item3d631f42ae:g:RLQAAOSwCyVcd1Mh>. They come with black screws, which is handy. However, there is also a huge choice of corners available from UK suppliers.

Those Proper Job clamps look quite good. You'll need four 600mm (24in) clamps. A couple of small ones are handy too. The Proper Job web page is here: <https://www.properjob.biz/shop/Rapid-Bar-Clamp-24in-M3235>. The ones I'm using were from Ebay and they're good quality. Here: <https://www.ebay.co.uk/itm/2-4Pcs-F-Clamps-Woodworking-Bar-Clips-Quick-Slide-Tools-50-150-50-300-80-600mm/113763919222?hash=item1a7cdba576:m:mVN-XAqagSxIuUF_70LeMZA>. There are some cheaper ones on Ebay that look all right: <https://www.ebay.co.uk/itm/4-PACK-HEAVY-DUTY-600MM-X-80MM-F-CLAMPS-SOFT-GRIP-HANDLE-QUICK-SLIDE/392097460082?epid=1866877692>