stevie

[quote name='Sean' timestamp='1399951827' post='2449272'] they're idiots and a disgrace to the other people who post drivel on internet bulletin boards... [/quote] What?

[quote name='Phil Starr' timestamp='1399676684' post='2446708'] I like to put some fairly heavy wadding on the back panel and leave the rest of the cab unfilled. This does make an audible difference and I'd move your wadding to the back panel immediately behind the speakers. [/quote] Although the situation is complicated here by the fact that the ports are on the back - so it may be better to put the damping on all the walls and the right hand back panel (not on the front baffle, of course). I use a staple gun for this, as you don't want the wadding flapping around. As Phil says, keep the wadding away from the ports and make sure that there is a clear path from the driver on the right to ports. i.e. you don't really want a lot of wadding in the middle of the cab. Looking good so far.

Steve, the way to get what you want is to fit a smaller driver - a 12" - which will extend lower at the expense of midrange efficiency. To do that you need a sub-baffle, which you can easily make by cutting a round piece of 1/2" MDF or (proper) ply the same size as your 15". Use the 15 as a template to drill mounting holes in the MDF. Then cut a hole for the 12" driver in the centre of the MDF sub-baffle along with suitable mounting holes. Stick foam tape around the 15" baffle hole in the Flite. Screw the MDF to your Flite baffle, fit the 12" (T-nuts are advisable) and you should be good to go - assuming you've chosen the right 12. The Kappalite 3012LF will probably suit, as well as a number of others. I did something very similar to fit a Kappalite 12LF to an Ashdown Mini 15, which is probably a similar size to your Flite. I used 1" birch because I had enough space behind the grille. If you paint the sub-baffle matt black and fit a standard 12" grille, it should look OK. You are not cutting or gluing your cabinet and the modification is 100% reversible.

[quote name='fleabag' timestamp='1399563683' post='2445388'] Checked your link stevie but just get a Blue Arans homepage and a large blank area - but i assume its somewhere amongst this lot ... [url="http://www.bluearan.co.uk/index.php?search=port+tube&x=9&y=11&stk=Any+Stock+Availability&perp=10"]http://www.bluearan....ability&perp=10[/url] [/quote] Yes. Sorry about that. The Monacor monacor mbr-100. Those drivers look quality.

[quote name='dannybuoy' timestamp='1399540928' post='2445103'] Question for you gurus - does the wadding affect the internal dimensions used in calculations, or is the assumption made that the sound waves travel straight through it so it is ignored? [/quote] For calculating cabinet size it's normally ignored.

I was thinking of this kind of thing: https://www.bluearan.co.uk/index.php?id=EVNL092C_2PK. They are just a lot easier to fit because you don't need a perfectly round hole. The flange covers your bodges with the jigsaw. Unfortunately, those ones are a bit short, although they would do at a pinch. If you keep looking you will find some adjustable ones that would be better, but they might be a bit pricey. Phil's idea of drain pipe will give you greater flexibility at a reasonable cost, but does require a neat hole to look good.

The two drivers you have will comfortably handle around 300 watts of bass in your box. Although one port was sufficient with your previous drivers, you really need to add a second port if you are going to take advantage of your new drivers' higher power. Two ports of 95mm internal diameter need to be 140mm long - which means extending your existing one or taking it out and fitting two plastic ones with flanges. Braces are something that you can always add later. To check whether braces would help, feel how much the panels of your cab are vibrating when you play your bottom E. Just out of interest, this is the kind of frequency response you can expect (bear in mind that the room will compensate to some extent for the fall in the bottom octave): [IMG]http://i58.tinypic.com/9sqtfa.jpg[/IMG]

If you decide in favour of the JB bridge pickup, the matching neck pickup is the Jazz (SH-2). It's a marriage made in heaven.

You seem to have enough wadding but I'm surprised that the brace between the drivers isn't connected to the back of the cab - that's how it's normally done. The two places you've marked for additional bracing are spot on and you probably won't need any more. Edit: I clearly misread the description here......Of course the brace is connected to the back of the cab.

If you were to fit more powerful drivers such as the Beyma, another port of the same diameter would certainly help and is perfectly feasible technically. 18mm birch ply cab, properly built, braced (no need to go mad), internally damped, a pair of good quality Beyma drivers - not many commercial 2 x 10s will keep up with that. And it will cost you £100 plus the damping, bracing and plastic port. There is no other way of getting such a big bang for your buck - especially as you will certainly get a few bob for your cheapo Eminence 10s. I'd also suggest you fit Speakons if you have XLR inputs, as they're an easy swap. If you decide to go ahead, get back to me and I'll work out the length of the ports for you (or you can do it yourself in WinISD). One last thing, not all tens are the same size. Check with the manufacturer's spec sheet to make sure your driver will fit.

I agree with JPJ. The only thing I would mention is that the cabinet seems to be tuned to 40Hz, which is on the low side. You will increase power handling a bit and maybe get a slightly punchier sound if you take the port out. A port length of 18mm should tune the cab to around 50Hz. My modeling program tells me you are exceeding xmax at around 100/150W.

What a great website you have!

Just to add to my previous post, there are a number of ways of minimising the pipe mode resonances produced by ports. The first one is to shorten the port, which increases the frequency and reduces the amplitude of the resonance. If you halve the port length you double the frequency of the pipe mode resonance, which will generally put it out of harm’s way on a bass guitar cab. The downside is that you have to reduce the diameter of the port at the same time, which may reduce the power handling of the port more than you would like. This is just one of the balancing acts you are faced with when designing a speaker cab. The problem is more difficult with smaller cabs. If you don’t want to, or can’t, make the port any smaller, a good solution is to put the port on the back of the cabinet, preferably near the centre of the cab. If you don’t want to do that, you can put a notch filter in the crossover to take out the offending frequency (you need to be a bit anal to do this, but I've seen it done). The final solution would be to use a midrange driver that covers the frequency where the port resonance would be.

Luke, it's the natural resonance of the port. I specified 4 x 70mm ports, as that's what Phil has fitted to the prototype. Unfortunately, that requires a port of around 10/11 inches in length which gives a low resonant frequency. It would be problematic leaving it like that because it would be audible, but there are ways of fixing it (in the mix!).

OK, here is a quartet of neo drivers. The Faital is used in the Bergantino CN series as far as I am aware, and the others are also found in commercial cabs. [IMG]http://i61.tinypic.com/j7usyv.jpg[/IMG] Pink is the Eminence Kappalite 3012LF Red is the Eminence Kappalite 3012HO Yellow is the Faital PR300 Green is the Celestion BN120300X

And here are another two popular 12" drivers in our box. All ceramic magnets so far. Blue is the Fane Sovereign 12-300 White is the Eminence Delta 12LF

Here are the simulations of the first three 12" drivers in our prototype box. I've tuned the cabinet to 50Hz in all cases. I'll post some more later, but I'm restricting this to three at a time for the sake of clarity. [IMG]http://i60.tinypic.com/2r4oow8.jpg[/IMG] Yellow is the Beyma SM212 Green is the Eminence Beta 12 Pink is the Celestion BL 12-200X

You can make quite a good case for the superiority of round ports, but I know Phil is using them in the prototype because they are easier to swap out.

[quote name='redstriper' timestamp='1398349853' post='2433268'] Looking good Phil and well done for keeping the weight down. Do you have an Eminence kappalite 3012LF driver to try in there? I am particularly interested in it's low end capacity for dub reggae. Steve. [/quote] I know weight of gear has been a hot topic with bassists for some time. My personal view is that a cabinet of this size should be made out of 18mm birch because it will be substantially more rigid yet will only to add 3.5kg to the total weight (even less when you consider the extra bracing needed for a 12mm ply cab). Everybody's needs are different though, and light weight remains a 'must' for many. Phil's choice of the Beyma is quite interesting, as it is relatively lightweight for a ceramic driver of this quality. I have a couple of 3012LFs, one of which will no doubt find its way into one of these boxes eventually. I know it probably doesn't bother you too much, Steve, but that chassis really needs a midrange unit to function properly (as Phil suggested). Now that we finally have a box, Phil has asked me to post some simulations of some of the more popular drivers on the market, including some we do actually physically possess, and I'll try to do that before the weekend. I think these might surprise a few of you......

I have a Carvin 1000W power amp (non-lightweight). It's got some intelligent features and build quality is very good. I have my doubts about support though: I sent them a straightforward query by email and it was ignored.

For most people that's true, JTUK, although I'm firmly of the opinion that swapping out an OEM driver for a top quality one is one of the most cost-effective upgrades you can make to your sound. You do need some background knowledge to do it properly though, as some swaps will work and others won't. Also, the cabinet often requires some modification to suit. You could easily improve on the OEM Eminences inside the TC 212 but you'd probably have to forget about having a coaxial driver.

The answer to your question is yes, the power (handling) of your cabinet will increase if you put more powerful speakers in it. As others have suggested, it's not necessarily as simple a job as it might appear.

I had one of these - for about two weeks. It was one of the Chinese-built ones. It was nicely finished and had a useful feature set. Even the piezo tweeter didn't sound that bad and I rather liked the GK 'growl'. The bad news started when I took a look inside. The driver had the smallest magnet I've ever seen on a speaker (well nearly!). It was really cheap and nasty. The cab itself was made from half-inch poplar or some other lightweight ply and constructed using staples and heat glue. The ply had obvious voids in it. The staples had missed the bracing in a couple of places and the brace rattled when you tapped it. It sounded quite good at low volumes but as soon as I turned the volume control up the cabinet vibrated in sympathy and it just sounded annoying. It was light, but that's because it was build like a packing crate - although it's not alone in that respect and there are lots of bassists out there using boxes like this and loving them. I didn't waste any time getting rid of it.