Phil Starr

That's looking really nice, if you fancied sending me a couple I'd love to get to see if it makes a measurable difference, I'd reluctantly return them to you afterwards. I'm sure @stevie would like to see them. He and I have slightly different positions on port noises where he is the perfectionist. Don't let him know but I think he's probably right. A couple of these would help advance an interesting debate. I'd just use the measurement from the outside edges as your length and the inside of the pipe as diameter. The computer software has a set of assumptions for making end corrections for port calculations but it makes a number of other assumptions too for things like leakage from the box. Consequently the calculated tuning is approximate at best (and varies with temperature and air pressure too) so we usually start off with the calculated length and then measure and re-tune. I doubt the manufacturers given parameters for the Scorpions are accurate for a 20 odd year old speaker too. The advantage of your end pieces is that you can cut the tube at will and always have a neat finish. Out of interest what is the approximate cost of making these this way. I have no idea what 3D printing costs.

Hi Adrian I don't know if Chard is too far deep into Somerset for you but we have been wondering if our 110T might be useful to upright players, and I might have other solutions for you too. I've been looking for someone to try our cabs with DB so if you fancied driving across you'd be welcome to try the BC cab, I could probably get one of our BC 12's up here too. You'd be helping me too, amplifying DB poses a number of technical and musical challenges so talking through things with a proper bassist would be a great way to spend an hour or two

The difference won't be in volume it will be in bass response, the bigger cab will give you more deep bass but from 150hz upwards the response and sound will be the same. The smaller cab compensates a little by having an audible response hump around 100Hz which gives a decent bass thump but is perhaps a little less honest. Gigging two of these is extraordinary, as part of the development of the 50l cab I gigged a pair for about 20 gigs. I had a grumpy drummer at the time and he asked me to crank up the bass as he 'couldn't hear it' (it was well balanced out in the audience area/FOH) for one gig I did crank it and at the end of the first half he had a different complaint 'I couldn't hear my effing snare drum'. Well he never complained again As to adding a tweeter, well that has two advantages, ours is designed to flatten out the response so what you get is the sound of the bass and any fx/tone shaping you choose to apply. The second advantage is in the radiation pattern, big speakers 'beam' the midrange and upper frequencies so that what you hear and what the audience hear are different and with a single 12 you'll be missing out on a lot of the mids and tops unless you angle the cab to point at your ears. of course if you stack two then the top cab will be nearer ear level so this is less of a problem. In contrast the single speaker gives a character of it's own. The 12CMV2 has a rising upper mid peak like most 12" speakers and with the bass peak at 100Hz it has an inbuilt 'smiley face response' which is pretty much what a lot of us dial in or get naturally in a lot of commercial cab designs. One solution of course is to build one with a horn one without. You then have three options; a full range cab flat response cab, an old school sounding 1x12 and a stack with both honesty and a really authoritative sound. Another option is to start with a simple 12 but leave space to add the horn later and do that as a separate project. I designed the 30l cab for smaller venues. You do lose some bottom end and frankly in small pubs that's really useful, in big/ open air venues not so much, in the end I used it for nearly everything though. Why carry something big when a small cab will do everything you want? Every one of these speakers is going to be loud enough to keep up with a drummer with a 300W into 8ohm amp and because the drivers have been chosen for good excursion they will handle that power comfortably. Two of the 50l cabs will overwhelm the rest of the band if you want, but why would you do that? Hope this helps

Curious about the Stagepas so I've just had a look, it's a bit of an outlier with 1.5" drivers in the column compared with most others which are using 3" or even 4" drivers. The problem is a lack of output 119db is claimed compared with 124db and 129db for the Stagepas 400 and 600. Your Mackies probably have a similar output to the 600's depending upon which ones you use so the Stagepas 1k is a lot quieter than your current PA. I don't think this is a potential band PA if you are going out with a drummer. There are loads of other systems out there which are more capable volume wise, no criticism of Yamaha. I'm a long time user and these probably sound fab but not as a band PA. I have to say I'm a big fan of the column systems though, I've heard the RCF Evox sounding great and had a chance to have a good listen to the MarkAudio Ergo at the South/west bass bash a couple of years ago and that sounded great too. I've played in a band with the LD Maui 28 and that was good too. The Bose though isn't really loud enough to be usable for a band IME

Hope the gig goes well tonight, (though given the time difference I should say I hope it went well. You are probably just finishing ) Looking forward to hearing how the cab sounded. It looks great.

I love the way you've made this cab your own, and if I had that amp then that is the way I would have gone. It's a shame other bass amps don't offer bi-amping in this way. That's a lot of punch in a lightweight very portable cab. I hope it gives you years of pleasure.

John @Chienmortbband I have been looking at drill batteries too. You can get higher voltages than a car battery and they are a lot lighter. I was looking for a 18-0-18 supply for a Chinese amp module and I have a couple of De Walt 18V, I never got round to trying them though. The car amps looked a simpler route.

Sorry the 'edumacation' only extended to telling you what an inverter is. Most of the commercial ones are three stage 'near sine wave' and whether they will work with your amp depends upon both the inverter and the amp. The good news is that if your amp has a switch mode power supply then you have a reasonable chance of finding something that works. If you have a Cass D lightweight amp and a friend with a caravan/camper it might be worth seeing if the amp works OK with their 'near sine wave' power supply The other battery solution is to look for a 12V amplifier. The 'bog standard' in car entertainment amps produce about 20w into 4ohms so if you can get an old car stereo with a mini jack input you could have 40W into a couple of 4ohm speakers and there are also cheap and cheerful Chinese stand alone 2x20W 12V amps around. Beyond this there are more powerful in-car amps that produce pretty much any power you want which have switch mode power supplies built in to the amp. I see @Mottlefeeder has pointed you in that direction already. It's not a bad solution if you want something cheap and only need to do this occasionally. It means you can use your usual speakers too. Worth looking at his thread on building a combo. The general problem with running off a battery is how long the charge lasts, It's not a bad idea to look to the most efficient speakers you can find. 3db of extra sensitivity is going to halve your battery use at the same sound levels.

The inverter plugs into a car battery (leisure battery is a spare battery to run a caravan) and turns the battery voltage to mains This one is £31

OK this is effectively our Mk2 cab then, don't tell @steviebut I really liked the SM212/1445 best of all yes you have fairly extensive bracing already, simple cross braces add a lot of stiffness for very little increased mass. Even a simgle batten linking the opposite panels will make a big difference. If you have any offcuts of your batten it would be a matter of moments to cut a batten as a tight fit and test it. Plave it slightly off centre if you can . A single brace will effectively divide the panel in two if you place it centrally and you can simply move the resonance up an octave. If you've ever damped a string over the 12h fret you know what that means.

Well done, I have to say that at this stage I usually spend far too much time playing with a half finished cab just for the joy of making a noise. I've looked at your pics and i like the bracing around the port/horn area which is a particular problem for the 110 we built too. that should be stiffening the back too so long as the front to back brace is firmly fixed. I'm a little suspicious of the frequencies you found resonances at 120Hz is so close to half of 230Hz it's possible energy is being transmitted between the side and rear panels. The easiest solution would be two braces across from side to side. bracing here might well help damp down the rear panel resonance as well. Which compression driver are you using with the horn?

there are a number of advantages of running two cabs at 8ohms The increase in radiating area increases the efficiency so you'll get an extra 3db of sound, this is greater than the roughly 2db you'll lose because your amp will produce less power into 8ohms. You'll double the power handling. The excursion of each speaker will be reduced this is usually the ultimate determinant of how loud the system will go and instead of the peaks taking the speaker into distortion using two will bring them back into their designed operating area. The halving of the power to each speaker will reduce the temperature and resistance of the voice coils at high levels reducing thermal power loss. stacking one speaker on the top of the other will bring the speaker nearer to ear level so you will hear the crucial mids and highs and be hearing more of what the audience will hear It looks cool

It's looking good, time to show the world.😉

Its looking promising, good proportions. As you suspect you'll have to brace. They are big panels for 12mm ply. One place we've had problems with is the baffle particularly between the speaker and port. Plan to have some sort of bracing there and leave plenty of meat to fix to.

G4M listing one in stock https://www.gear4music.com/PA-DJ-and-Lighting/Celestion-CDX1-1070-1-Compression-Driver-8-Ohm/2NRH

If you can take some pictures during the build please. I didn't take many as I never thought it would gather a lot of interest. If you build it I've also used it as a 'bright box' which it does quite well and is fun.

Hi John, the 50mm dimensions are the ones I used in the original combo, because I was using an existing cab I only had space to fit in a tiny port. When i redrew the cab for @RichardH I recalculated the port for the permanent design. It is tuned to the same frequency. The 68mm is the outside dia, inside dia is actually 64mm but it is standard UK downpipe. The bigger dia pipe is better because wind noise in the port is less likely so use that nless there is a good reason not to. I missed this yesterday because I was at rehearsal. I took my 6" cab and Warwick Gnome along to set up as a bit of fun. I've recently built a lightweight cab for our guitarist and I was teasing him about his 'huge' stack. Since it was there anyway I used the House Jam Cab for the first song. Our drummer is pretty loud so I had my usual cab but hidden out of sight (I know, I'm really childish) but didn't need it for the first song or the whole rehearsal. The studio isn't huge maybe 6mx6m but this is mad , I used a bit of compression and some trimming of the bass with my Zoom B1 but backed up against the wall the sound was really just there, sitting in the pocket and plenty loud enough for rehearsal/on stage monitoring. I'm starting to wonder about a 2x6.....

Thanks for that. I'm always ridiculously pleased when a build makes it's first sounds, even more so when it is someone else's. That Faital is a nice driver but recommending something when other people's tastes and needs vary so much is always a bit of a risk. Really looking forward to seeing the pics,

@anrque how is your build going?

There's loads of resources out there but as a practical, working source of advice The Loudspeaker Design Cookbook by Vance Dickason is as good as it gets, TBH nowadays it's my bible, I read a lot of the more technical stuff years ago but don't go into that level of detail in building and designing speakers. It's my go to when I want to check advice I give here is correct as far as it goes.

That looks a lot better, you'd need to think about how the pipe butts up against the flare as that joint would need to be as smooth as possible. Think as if you were designing the aerodynamics of a car, Any sharp joins are going to cause wind noise and drag. Maybe a collar running outside the flare and the pipe? You'd also want to slim down the front flange unless you intend recessing it into the baffle. This is now looking like a really interesting project.

Hmm it's 50 years since I did any fluid mechanics but there's not enough of a radius on that design to make any difference to the air flow inside that port so the only advantage IMO is that the length is continuously variable. though the lip covering any problems in cutting a hole in the baffle will improve the finish. To be honest it's a lot quicker to cut lengths of pipe

I think you've answered your own question here. I don't consider myself much of a musician but there are people out there with apparently no idea. I was a late starter to music, still suffer from imposter syndrome and I'm still pathetically grateful to anyone who will have me in their band but there have been a few occasions where I've felt we've been letting the audience down and I'm never going there again. I've a really lovely friend who plays keys and he's partnered with a woman with a truly great rock voice but he can't keep time and has an inability to listen to the rest of the band. I haven't the heart to tell either of them but I think every musician in the area knows the problem and we are all letting them hang on to their dreams whilst making our excuses. Excuses you will have to make. If you are going to stand up in front of other people I think you owe it to them to take it seriously whatever level you are playing at.

You should add maybe 8 litres for the speaker and port. if you can flare the port at both ends it reduces the sudden pressure changes and ultimately the turbulence you get which causes port noises at high levels. However it will also mean that if the tuning is out you can't easily change the length of the port to re-tune. I suppose one answer will be to make the flares so that they are designed to push fit into the end of a standard soil pipe. That would be quite neat and there might even be a small market for them However I've never had a problem with port noises in a band setting, even with smaller ports than these which should be better than the original Peavey ports anyway, if it's important to you and you have expertise then give it a go but it's a luxury touch not essential IMO. Adding a tweeter will change the sound of the speaker. That's complex because of the way we hear sound and because the changes will depend upon the exact characteristics of both the speaker and the compression driver/horn that you choose. If you like the sound of what you have then do you want to change the sound. Crossover design is complex and still requires a lot of trial and error and ideally proper measuring equipment. You can buy a generic crossover but it will only be very approximate. I can talk you through some of the design problems but I'm not really an expert. To be fair a lot of commercial cabs with horns don't have well designed crossovers so you can get something that 'works' from a generic crossover and you might like the sound. It doesn't have to be 'honest' to sound good. There are pluses though in having a horn. A 15 is very directional in the mids and tops so what you here and what the audience hear wont be the same. The upper range is all coming with the cone under break-up conditions when the cone is no longer a pure piston and as such is distorted and often slightly louder on axis than the bass. It's part of what gives 15's their lovely old school sound. Get the horn and crossover right and you'll get a much more modern flat response. More like a bass played through headphones. It's up to you really but you could just build the cab but leave space on the baffle (front board) to retro fit a horn if you later decide it's a must have.

I'm not familiar with the Scorpion itself, all my Peavey experience is with the Black Widow speaker which looks to be similar. The dust cap which you get on every speaker (just about) is usually just a fabric or paper dome stuck down onto the middle of the cone , primarily to stop dust and crud getting into the magnet/coil. The foam is/was found inside the back of the magnet if I remember. I haven't had that problem. Like the BW you can remove the magnet off the back of the scorpion and see inside and clean out any debris. If your speaker sounds good and doesn't make any 'off' sounds then you probably don't have a problem to solve. So I'm recommending a 55litre cab with a 4" soil pipe forming a port, you only need 7.3cm length though. Are you confident enough to work out the panel sizes yourself? This might be useful it has instructions for taking the magnet off. Be gentle with the voice coil though, it's easy to damage with a big heavy magnet.