Another micro cab

[tauzero]

This one is using @Phil Starr's original plans. I have very little faith in my own ability to use power saws accurately (see later) so I found a place that would supply cut panels and got the panels from there. After getting panels, battens, speaker, connector plate, and speakons, the first thing to do was mark up all the panels for drilling. I wanted to screw and glue everything, so marked up lines to screw into the centre line of the battens and the centre line of the side panels and drilled 3mm holes. That was a few days ago. Then I got the screws and the glue arrived, so today was the next stage.

 

Both sides battened up.

 

 

Then the top (part battened in this photo):

 

 

And with the bottom also done, I glued and screwed the sides to the bottom (seen inverter here):

 

 

The mitre clamps aren't exactly up to professional standards, but they were four for a fiver or so off Ebay (rather than four or five quid each) and they did the job.

 

I also cut the hole for the connector plate and for the port, and the hole for the speaker (which was a little wobbly but OK). Last job today was gluing the port in place. 

 

 

I was going to use grill cloth but after seeing @Pea Turgh's build, I've decided that the circular speaker grills look OK and it'll be simpler to work with, so one of those is about to be ordered.

 

Given the absence of a router at Zero Towers, plus my complete lack of experience at handling said beast, I think rounding over is going to be by means of a sander. Front and rear panels will be getting blackchalkboard paint and I shall probably be wrapping the main body - I have an idea but I shan't reveal it yet. Current plan of action is to finish box assembly tomorrow and do the painting and covering in the week.

[Pea Turgh]

Hows this going, @tauzero?

Edited June 21, 2022 by Pea Turgh

[tauzero]

The box is built, I'm getting some Dremel bits and a routery thing to try and do the rounding over. Some wood filler and sandpaper also lies in its future. Three of the battens for the rear panel are correctly aligned, the fourth is about 3mm further in so I've got to raise it a bit as the rear panel isn't going to be permanently fixed in place.

[tauzero]

Everything got rather put on one side for a while but I've removed the screws, filled the holes, and I've just been sanding everything down and rounding the corners over somewhat. I have just bought a palm router (for anyone who's looking for one, the highly recommended Makita is available from Alan Wadkins for £60 plus postage - https://www.alanwadkinstoolstore.co.uk/power-tools-c17/routers-c22/makita-rt0700cx4-router-trimmer-110v-or-240v-p24171) but I want to practice with it before destroying any painstakingly constructed object so the rest of the rounding will also be by hand. A bit of sanding of filler required round the battens on the back too.

 

 

[Phil Starr]

looking good, can't wait until you give your verdict on the sound.

[tauzero]

Covering first. Ages ago, I got a sheet of carbon fibre look stick-on stuff which I was going to use for some purpose on a bike - the purpose is long-forgotten but the fabric was just the right size to wrap the cab, so that is now in progress. It's not very sticky so I'm using Gorilla glue to stick it on.

 

I started by making cuts in the fabric to let me fold it into the top back and glued it into place, giving me an anchor point.

 

The next stage - the top:

 

 

The second of the two sides:

 

 

Wrapped round and doing the bottom - I decided just to overlap it, it's quite thin and the joint won't show:

 

 

The tricky bit - wrapping the edges round at the back:

 

 

I still have two front edges and all four rear edges to do, then I need to trim the rear panel very slightly to fit (sanding it down to size should do) and paint it. Front panel has already been painted black.

 

Incidentally, the slightly misplaced batten was cater for by getting some iron-on edging, narrowing it down a little, and ironing it onto the batten. It's all going to get some 3mm thick rubber foam round the edge anyway which should seal it up nicely.

 

I must say, retirement has been a great help. I've made more progress in six days than I did in the previous six months.

[Baloney Balderdash]

I didn't seem to be able to spot you mentioning the size of the speaker unit in this, so what is it?

[tauzero]

It's the Fane Sovereign 6-100 6" driver. The cab is @Phil Starr's design: 

 

[tauzero]

The Gorilla Glue is really cráp for this purpose - it expands quite a bit so even after smoothing out the wrap, it ends up somewhat lumpy. Not the glue's fault at all, I just used the wrong glue for the application. If I was to do this again (and wild horses wouldn't make me I think it's unlikely), I'd use something that squishes out better. The last few edges I'm doing with Bostik general purpose PVA glue - I'll see how that goes. It looks OK from a distance, I shall either never take it out of the house or put a cordon 5m from it to prevent close inspection. The PVA will take 24 hours to cure so there's about 17 hours to go to find out how successful that is.

[Phil Starr]

I don't use vinyl very often but I've been building cabs for over 50 years so I've tried all sorts of glue. I started with 'hide' glue: animal protein bought in pearls and melted in a heated pot, PVA and aliphatic glues and latex based glues. in the end I've settled on impact adhesives as the best solution, though PVA is fine for the body or the cab I always use impact adhesive for the edges as  maintaining pressure on the edges which are always trying to unfold is a complete pain. If you do use Pva then one tip is to use a hair dryer on the vinyl as it goes floppy when warm. Too hot and it melts though, nobody at all will wonder how I found that out

 

Not long now, well done so far.

[tauzero]

Very near the end now. Put in some acoustic wadding (left over from the BC112 mk3 which is still awaiting completion) and mounted the speaker and grill. The front panel doesn't bear close, or even medium, scrutiny, but it's all valuable lessons isn't it?

 

 

 

I haven't put any wadding on the rear panel - I may be putting a mini power amp in there so I didn't want to put wadding on until I knew how much space there would be.

 

Waiting for some screws to arrive to fit the rear panel on, and then it'll be all systems go.

[tauzero]

Well, that's it all buttoned up (remembering to solder up the connections to the speaker first, of course). Now for the first test.

[tauzero]

I have encountered an issue. The grill is held on with clamps which have a quite large offset, so the grill will only be held on by them if the speaker is on the front of the panel rather than the rear. I'm getting a bit of a buzzy noise which I suspect is air going through the speaker screw holes. So should I put the speaker in its proper place at the rear of the baffle, and find some way of shimming the clamps, or should I just fill the holes? I realise that having the speaker on the front of the baffle has changed the volume, but will this have had a significant effect on the cab? Other than the buzz, it's sounding fine, powered by a Tecamp Puma 900. I would have used a Hotone 5W amp but it's been so long since I used any amps that I've lost track of my jack-Speakon lead.

[Phil Starr]

It looks like your speaker cutout is a bit wonky and I guess you didn't use the holes drilled for the speaker. It's not unknown for a speaker to be bolted on and then the grille clamped on afterwards which would at least make sure the speaker was held firmly and the holes were filled. Or you could just use filler.  I don't think there is a gasket on the back of the fane speaker. I usually use some of the black draughtproofing strip which you seem to have on your back panel/battens. to form a gasket. Also check nothing else is loose inside and the speaker cable isn't rattling against anything.

[tauzero]

I filled the holes, touched the front panel back up, and put more strip on the connector plate to seal that too. All is now well.

 

 

All sounding good. Better than it looks, anyway.

[tauzero]

One question for @Phil Starr (or any other cab experts) - I'm thinking of making this a combo with a tiny 30W amp module. Would a jack socket with a hole in it like they all have be a significant problem?

[Phil Starr]

Hi, well done for getting there with your cab. I'd love to see a review when you've had a chance to play with it a bit.

 

The design started out as a micro combo (a lockdown project for me in the days when you could meet in groups of six)  and my prototype for your build was actually made as an add on to the micro combo. @Pea Turgh built one too. My intention was to make a combo and I have some cheap Chinese modules sitting neglected in a cupboard ready to make mine into an active cab/combo. The reason it didn't get completed was because I tried the cab out with my proper bass amp and it sounded so good with all the extra power that I went out and bought a Warwick Gnome to pair it with and took it gigging. 

 

The short answer is yes you can! 

 

I wouldn't worry about the jack, my micro cab has two on the back plate and cabs have been made with jacks for decades. Theoretically it changes the leakage of the cab and could also be a source of noise but in practice I doubt it would be an issue.

 

Beware the Chinese amp modules, a lot of the power claims are what the chip will give at maximum supply voltage and lowest speaker impedance. Heat sinking can be an issue too. @Chienmortbb has more experience with these than I do.

[Chienmortbb]

2 hours ago, Phil Starr said:

Hi, well done for getting there with your cab. I'd love to see a review when you've had a chance to play with it a bit.

 

The design started out as a micro combo (a lockdown project for me in the days when you could meet in groups of six)  and my prototype for your build was actually made as an add on to the micro combo. @Pea Turgh built one too. My intention was to make a combo and I have some cheap Chinese modules sitting neglected in a cupboard ready to make mine into an active cab/combo. The reason it didn't get completed was because I tried the cab out with my proper bass amp and it sounded so good with all the extra power that I went out and bought a Warwick Gnome to pair it with and took it gigging. 

 

The short answer is yes you can! 

 

I wouldn't worry about the jack, my micro cab has two on the back plate and cabs have been made with jacks for decades. Theoretically it changes the leakage of the cab and could also be a source of noise but in practice I doubt it would be an issue.

 

Beware the Chinese amp modules, a lot of the power claims are what the chip will give at maximum supply voltage and lowest speaker impedance. Heat sinking can be an issue too. @Chienmortbb has more experience with these than I do.

Well, I did have a speaker that had a jack socket that whistled. I heard the noise, tried everything and the solution was to use put a jack plug in the socket. I did some investigation and sealed sockets are very rare. I found that the Cliff range https://www.cliffuk.co.uk/products/jacksockets/s1k.htm these are available as part of the RS Pro range. Incidently, I have a few of these if anyone is interested.

 

Amplifier modules are a can of worms unless you buy a "name". Even then, you need to know how to read the specs and how to get the best from them. So I will put the question back and ask some questions.

 

1. Do you have a preamp?
2. How much power, would you want to drive an extension speaker?
3. Will it go inside the cabinet?
4. How will you power it?

If we go with your 30W power, I would go for a higher powered module and run it at a low power rail(s).

 

 

 

 

 

[tauzero]

1 hour ago, Chienmortbb said:

Well, I did have a speaker that had a jack socket that whistled. I heard the noise, tried everything and the solution was to use put a jack plug in the socket. I did some investigation and sealed sockets are very rare. I found that the Cliff range https://www.cliffuk.co.uk/products/jacksockets/s1k.htm these are available as part of the RS Pro range. Incidently, I have a few of these if anyone is interested.

 

Amplifier modules are a can of worms unless you buy a "name". Even then, you need to know how to read the specs and how to get the best from them. So I will put the question back and ask some questions.

 

1. Do you have a preamp?
2. How much power, would you want to drive an extension speaker?
3. Will it go inside the cabinet?
4. How will you power it?

If we go with your 30W power, I would go for a higher powered module and run it at a low power rail(s).

 

This is just experimental for now, to keep me off the streets.

1. Zoom B3n, HX Stomp, MOD Dwarf - several preamps but they are more pre than amp, so the signal level would probably be too low just using those. A simple amplifier with a gain of 10 or so should do the job if necessary.
2. Not a lot, I would think. When I've dug a J-J speaker lead out, I'll see what a Hotone 5W amp sounds like through it.
3. That's the idea. Everything is subject to change.
4. USB-C, either from a power pack or a mains adaptor, preferably variable voltage.

[Phil Starr]

I have wondered about building a second with an amp in, though I'd go for something more powerful and possibly 12V like a car amplifier. I'd fit a switch (probably a switched jack) so it could be used as either an active or passive cab. It's so good with the Warwick Gnome however that it's not a priority project.

 

I've also used this cab with an active crossover and a BC Mk1 112 as a bright box and that sounded wonderful. In fact it sounded pretty good with no crossover but you'd be limited to 100W that way.

[Chienmortbb]

17 hours ago, tauzero said:

 

This is just experimental for now, to keep me off the streets.

1. Zoom B3n, HX Stomp, MOD Dwarf - several preamps but they are more pre than amp, so the signal level would probably be too low just using those. A simple amplifier with a gain of 10 or so should do the job if necessary.
2. Not a lot, I would think. When I've dug a J-J speaker lead out, I'll see what a Hotone 5W amp sounds like through it.
3. That's the idea. Everything is subject to change.
4. USB-C, either from a power pack or a mains adaptor, preferably variable voltage.

The PAM series amps from DIODES Inc may be worth a look. Power is somewhat limited at 5V, as with any amp. I have never tried them as a bass amp but could try one with my Zoom B1Four and my 8" with a Fane lets you know. To be honest, 2–3 watts, is more than enough for home practice, although I think the sensitivity of the amp may be a problem.

[tauzero]

15 hours ago, Chienmortbb said:

The PAM series amps from DIODES Inc may be worth a look. Power is somewhat limited at 5V, as with any amp. I have never tried them as a bass amp but could try one with my Zoom B1Four and my 8" with a Fane lets you know. To be honest, 2–3 watts, is more than enough for home practice, although I think the sensitivity of the amp may be a problem.

 

The thing about USB-C is that it can go up to 20V using a little controller - https://www.ebay.co.uk/itm/193527265113

 

 

[Richard R]

On 05/03/2023 at 02:19, tauzero said:

 

 

 

Now that is an excellent video. Thanks for posting. 👍

[tauzero]

Just to follow this up, I have been testing the concept of a USB-C powered 30Wish amp. Here's the test rig:

 

 

The smaller board is the ZY12PDN USB-C controller board (https://www.ebay.co.uk/itm/193527265113?var=493739920515), the larger one is a 30W amp module from Ebay (https://www.ebay.co.uk/itm/144946097523). I tested this with a couple of power supplies. A bass (Ibanez EHB1265 in active mode) was able to give more than enough signal to push the amp module to distortion running at 12V. I've got another power supply coming which hopefully will deliver 20V. I have a cunning plan to avoid sticking a signal up the backend of the amp module if using the cab as a cab - the amp input and output and a USB-C connector will all go to a second recessed plate, and the amp will then be connected to the speaker when I want to use it with a J-J lead, the same way as many combo amps (especially guitar) are done.

[JSbass]

And how did the controller board and amp module perform with the Fane Sovereign?

 

Is the sound quality before distortion acceptable, and is the volume level enough, say, for accompanying acoustic instruments in a small gig setting?

 

If so, this certainly would appeal as a low cost, compact and lightweight battery powered rig.