stevie

Well said, Dood. However, the companies that are doing it right are a lot rarer than you might think. One, maybe two boutique companies, I'd say. The others talk the talk and make extravagant claims, but have exactly the same attitude as Markbass. I think the fact that you can improve a bass cabinet from one of the industry's prestige manufacturers by taking out one of the drivers speaks volumes about the products that we bass players are being served up nowadays. Still, these manufacturers want to stay in business, and why should they spend money on the internals when bass players continue to give their products rave reviews? Cost cutting doesn't seem to have done Markbass any harm.

I'd like to say a big public thank-you to John, aka Chienmortbb, for his invaluable help in getting this project together. Not only did he build and supply the prototype cab for me to work with, but he also supplied the drivers. And he burned the candle at both ends to get a working system together (just) in time for the SW Bass Bash. I hope you DIY builders appreciate the effort he has made on your behalf. I did promise you some measurements on this second system, but what with the last-minute rush to get John's cab ready for the SW Bass Bash, I forgot to save a full set of measurements. I did save a normal frequency response measurement, however, and you can see it below. All the off-axis measurements looked good and the impedance didn't dip below 7.3 ohms - I just didn't save any. The response curve is at a distance of 2 metres. It's impressively flat, thanks to a couple of non-obvious tricks in the crossover and the fact that the horn mates well with the compression driver. [IMG]http://i64.tinypic.com/208zh5h.jpg[/IMG]

[quote name='The Shrek' timestamp='1491409735' post='3272829'] Sorry guys but I am way out of my depth. I will have to opt for the most basic and simple way to get a 12" and a 5" in one cab. I really enjoy the box building part, but the techy stuff makes me want to slash my wrists. [/quote] Michael, just try a 12uF cap (polypropylene is best) in series with the 5" driver. I'm guessing you're going to be using the Faital Pro 5, as I don't know any others. Don't forget to give it its own cabinet of between 1 and and 1.5 litres and fill it with wadding. As it is likely to be louder than the 12, you'll probably need an L-pad attenuator to quieten it down a bit. Get a 100W one, wire it according to the instructions and set the level by ear. Connect the 12" speaker directly to the input. I can't make it any simpler than that. But I still think you'd be better off building one of the designs in this thread.

Well, at the risk of boring people to death, I can tell you what little I know. I have an electrically powered winding machine, quite ancient, but it's a proper winding machine with an electronic counter and cutoff. So it's not really DIY and I've used it in the past to produce thousands of coils for commercial speakers. As far as potting is concerned, I use the same air-drying lacquer you would use to finish your pine chest of drawers. I apply it to the outside of the coil. It only penetrates through a few windings but works well enough to prevent unwinding when you're handling the coil, which is the aim. The bobbin keeps the rest of the coil held tightly together. That's always been good enough for me, although there are better ways of doing it. The most popular is to use enamelled wire coated with a temperature sensitive adhesive. You wind your coil and pass a large electrical current through the coil to heat it up and glue the windings together. You need to do that if you don't use a bobbin. Then there is vacuum dipping, where the coil is suspended in a tank of varnish and a vacuum applied. The coils are then transferred to an oven to bake. None of this is DIY though. I'd certainly advocate using wood varnish for your occasional DIY coils.

[quote name='Passinwind' timestamp='1491324646' post='3272148'] BTW, I'd like to see some more discussion on DIY coil winding, and even more so on properly potting or otherwise binding the finished coils. [/quote] We're a bit nerdy on here, but I don't think we're *that* nerdy.

[quote name='Phil Starr' timestamp='1491337619' post='3272299'] Hi Michael, though it won't be fully optimised for your particular drivers you can always use a bog standard crossover circuit instead of just a capacitor to protect the 5" unit from the bass (and most of the power). The simplest would be a 1st order crossover to gradually remove the higher frequencies from the bass unit but a better way would be a 2nd order design Which has a quicker cut off for both speakers at the crossover point. You can get the basic calculations done here [url="https://www.diyaudioandvideo.com/Calculator/SpeakerCrossover/"]https://www.diyaudio...eakerCrossover/[/url] Go for the Butterworth for 1st order or the Linkwitz-Riley for the 2nd order. It'll only work if your speakers are more or less the same sensitivity. [/quote] With a first order cap you'll be somewhere in the ballpark and it will sort of work. Once you add a coil to the circuit, the results could be disastrous unless you know what you're doing. I really wouldn't. In fact, using a crossover calculator is doomed to failure because they work on the assumption that you have a flat impedance curve on all your drivers, that they have a flat and extended frequency response and are time aligned. None of which is ever the case.

This a fairly flexible design. Builders have the choice of a two-way with an inexpensive tweeter, a two-way with a proper compression driver, or a one-way with the Beyma 12" speaker on its own. However, the cabinet as it stands will work with any 12" driver specified for bass guitar - the Eminence bass 12s, including the Beta, all the current bass guitar speakers from Celestion, the Faital Pro 12PR300 and others that I've not even thought about. However, you can't expect the crossover and HF units to work with these other drivers.

[quote name='Passinwind' timestamp='1491275795' post='3271728'] Personally, I really like the all dark look a lot, and never really liked plastic piping or trim of any kind except for corners, same as on basses for that matter. [/quote] You could well be right about this. It's difficult to judge from a photo.

[quote name='The Shrek' timestamp='1491233409' post='3271426'] Thanks Stevie. Guys I hope I am not being forward in asking this question. I would gladly pay upfront for the service if there are any of you basschat guys who would be prepared to build a proper crossover for my project. Just advise me on what speakers to buy to match the appropriate crossover build. I am in Northern Ireland so I will gladly pay for any excessive post and packing and any other costs. [/quote] Michael, I have so many projects on the go at the moment, I can't find the time to get to them. Designing the kind of crossover you're looking for means having the completed cabinet here and measuring it. Then designing the crossover in CAD, building it up to see if it works, and adjusting it so that it sounds right. Although some crossovers almost build themselves, it can often be a fairly time-consuming process, with three-ways being particularly demanding. The cheap and cheerful way of integrating a 5" driver with a bass unit is just to stick a capacitor in front of it to roll it off at a relatively high frequency, say 1500Hz. I wouldn't be surprised if that's what Mark Bass have done with their latest three-way, although I'd be happy to be proved wrong. It will work, but I'm pretty sure you'd be better off with the two-way design described here.

One of the requirements was reasonably priced.

That's a very good point!

Shrek, yes you should be able to use a round 4" port instead of the slot port. The Beyma we're using should work in your cab, yes. I performs fine down to a cab volume of about 40-litres. It would be worth copying some of the details of our cab and transferring them to your build, in particular the bracing and the wadding. No need to follow slavishly; just follow the principles. Using a midrange unit is a great idea, but you will not be able to do anything worthwhile with an off-the-shelf crossover. It needs to be custom-designed for the specific drive units. You should have enough room in your cab for the P. Audio tweeter - and the x-over isn't that complex. If you're going for the Beyma 12, you could give it a try.

I think carpet is easier to fit and also more forgiving than tolex, BoB. The lesson here is that you really have to finish off your screw holes properly or else they show through the paint. It looks like they managed to do without the inductor.

That's interesting, Shrek, thanks. I have to agree with Bill Fitz on this: manufacturers tend to be more interested in how a cab looks than how it performs. Love the crossover!

I could estimate it: 7kg wood. 4.3kg Beyma 12. 1kg Celestion compression driver and horn. 2-3kg crossover, handle, feet, grille, paint. It should be under 15kg anyway. Going neo would take that down to about 12kg. But let's see what John's scales say. The grille works well but I think it needs some piping to finish it off. Perhaps carpet would be an easier finish than paint for the occasional builder. I wonder.

What a great turnout. I was at the last two SW bashes but had to miss this one because of work. Keep the pictures coming!

That template will prove invaluable. I found it really tricky (i.e. messy) to cut the oval shape out on the prototype and wish I'd had it them. I think it needs to be pinned to post #1 so that all the reference documentation is in one place. [Edit - I just tried to pin it, but it looks like no more than 3 PDFs can be pinned to any one post. We'll consolidate all these files when we're done.]

Paint doesn't have any symbols either; I just drew them as lines or rectangles. It would have been nice to have been able to copy and paste them once I'd drawn them once, or to move them if they weren't quite in the right position. Google Draw does look good, but I found that I can do what I want with the Open Office drawing application. But many thanks for the pointer, 6v6.

Here are the corrected versions.

Oops! I knew there would be something. Thanks for spotting this, tauzero. I'll fix it now.

The drawing progam in Open Office is excellent. Thanks for the tip!

I'll give it a go. I've just tried three other highly recommended drawing programs, but they're not as intuitive to use as Paint. I just need a copy-and-past feature so that I don't have to draw everything from scratch, and the ability to save text as text, so that I can edit rather than erasing and re-writing.

Here's the HF section. Can anyone recommend anything better than Microsoft Paint for this kind of stuff? [IMG]http://i64.tinypic.com/n2g16q.jpg[/IMG]