stevie

[quote name='Deep Thought' post='532664' date='Jul 4 2009, 10:06 PM']I have a pair of ABM Minis with Celestion Neo 12's in them-same size cabinet. I'm delighted with them-I bought them from Nick Carey, who told me they were customised by somebody who does such things, whose name I forget. Drop him a PM and I'm sure he'll fill you in.[/quote] I didn't realize the cab was quite so small when I bought it, but my plan now is to fit a 12" driver into it. I would imagine it's really nice with the Celestion neo 12 in there. Great size and weight, too.

[quote name='bumnote' post='532651' date='Jul 4 2009, 09:40 PM']I understand that a company might fit the cheapest speaker it can get away with, but why not port it properly, surely that costs nothing[/quote] You'd certainly think so, wouldn't you? Actually, the porting wasn't a million miles out. I measured one bass guitar cab (quite an old one) that was tuned to 70Hz. In the Mini 15, Ashdown used a standard, moulded port from one of the usual trade suppliers: I've seen it before. It really needed to be one or two inches longer but I imagine they thought it was close enough and nobody would notice any difference. Which is the same reason why they couldn't be arsed putting 50 pence worth of BAF wadding in the cab. I'm afraid this is the kind of thing that goes on all the time.

[quote name='hubrad' post='531535' date='Jul 3 2009, 11:40 AM']We follow that same policy at the shop unless you really want to get it on Monday, but we do tell people! [/quote] Is that because stuff is more likely to get nicked or damaged if it spends a Saturday at a depot?

[quote name='alexclaber' post='531227' date='Jul 2 2009, 11:12 PM']You're not wrong about that driver! That's exactly the sort that gives 15"s their undeserved reputation for boominess.[/quote] Yes, funny that, Alex. The more I find out about equipment for bass players the more I realize that much of it is gloss not substance. I think perhaps a more critical specialist press could help stop manufacturers getting away with the things they do. I notice in Tom Bowlus' online review of 15s, including the small Ashdown, he didn't mention the fact that the Mini 15 has a 6dB peak just over 100Hz - which is a serious design fault. If he noticed, he certainly didn't mention it. Makes you wonder. Given how much bassists spend on their gear, the cost of a decent driver for their speaker cab is relatively insignificant and would probably make a bigger difference than any other investment they could make.

I've measured the Thiel Small parameters of the speaker in the ABM Mini 15 cabinet. Do you want the good news or the bad news, John? Well, the bad news is that Ashdown have clearly fitted the cheapest driver they could find that will handle 250 watts, stuck it in the box and hoped for the best. The good news is that the driver is so cheap, it won't cost very much to buy something similar. For anyone else visiting this thread with the same problem, the basic parameters are: FS 35Hz Re 6.7 ohms Qe .67 Qm 8.7 Qt .62 VAS 287 litres That should allow anyone to model it should they so desire. The driver is a Sica Z008190 - says so on the magnet. It is not one of Sica's standard models. However, its specs are similar to the Eminence Beta and Delta 15s. If you want a direct, cheapo replacement you should be able to pick up a second hand one of those for very little money that will sound fairly close to what was in there before. I would warn you, however, that those cheap Eminence drivers have only one thing going for them - they are bombproof. Don't buy new ones though: you should definitely spend a little bit more and get something half decent. It's such a nice, birch ply cabinet that it would certainly be worth putting something better in it. The Celestion BL15-300X looks quite good. Even better would be a Celestion neo, the TN1530. The two Celestions would both perform better in a bigger cabinet but they will work in the Mini box and sound better than the original speaker. You need to extend the ports to eight inches either by fitting new ports or by adding some cardboard tube to the existing ones. Also, you should staple some BAF wadding to the walls, which will improve the quality of the midrange. That's it. Good luck.

[quote name='Musky' post='530717' date='Jul 2 2009, 03:25 PM']I'm not sure an imperfect analogy needs taking to a logical conclusion. [/quote] You're probably right .... I just couldn't resist. I'll try to exert more self control in future.

[quote name='alexclaber' post='530613' date='Jul 2 2009, 01:45 PM']Or to look at an analogy, the performance of a car is not determined by the number of doors it has. Yes, there are lots of fast 2-door cars but there are plenty of 4-door cars with far better performance than many 2-doors. What matters much more is the weight of the car, the stiffness of the suspension, the centre of gravity and the power of the engine ...[/quote] If I want a car with four doors, I want a car with four doors. I don't care how fast it goes as long as I don't have to swing the front seats up to let the kids in every time I take them to school. A car with four doors meets my needs better than a car with two doors - to take your analogy to its logical conclusion.

Finally, here is a frequency response curve of the ABM Mini 15 from 200Hz up. It measures quite smoothly and is relatively extended for a 15. Notice in particular the lack of sharp peaks. The waterfall plot isn't quite so nice, although the lack of damping inside the cab doesn't help. Ignore the curve in the top window.

It can be fixed though, with a bit of jiggery pokery. Ignore the green curve - that's a halfway house. Not bad, eh?

The frequency response is exactly what you would expect from fitting a speaker in too small a cabinet. The Trace 1153 is similar, although not quite so bad. The measured frequency response starts at 40Hz here and finishes at 250Hz. It's not a pretty sight. The word is boomy.

I measured the impedance of the cab, and it is tuned to 50Hz. Too high. We can sort that out by lengthening the ports. I've used Pringles tubes before and they may work again here.

Snap! I also have an ABM Mini (purchased yesterday from a very nice Basschatter) with a faulty drive unit - just like yours. Mine is only starting to go, as there is no coil rub yet - but it's certainly on its way out. I'm fairly sure that incorrect cabinet tuning is the cause of the failure. My back-of-a-fag packet calculations show the cab is tuned to about 55Hz, which means the speaker will only handle about 10 watts of low E. So, driver failure has been built in and is just a matter of time unless you're using it in your bedroom. I'll measure the cabinet tuning some time soon, and when I've managed to persuade the driver to come out (I thought it had been glued in!!), get the Thiel Small parameters, which will show us the type of driver they've used. This cab is roughly 45 litres in volume (much smaller than I was expecting), which is much too small for just about every 15 I know - but a good volume for a 12. In other words, there is no benefit in fitting a 15 in here, because a 12 will produce just as much bottom end. Given the excessive profit margins manufacturers make on spares, I would hesitate to replace the driver with another of the same. A budget, lightweight option would be the Celestion TN neo 12" available for about £50, but you will need to fit a panel of 1/2" birch ply over the front baffle first. The 15" Celestion TN neo costs £25 more but will not actually provide any more bottom end (because of the small cabinet size). Plenty of quality 12" drivers will work in here though. Bear in mind that the cabinet should definitely be re-tuned lower - or else the same thing will happen again. As long as you're not in a rush, I can post my results from time to time for your guidance. Incidentally, I sent an email to Ashdown yesterday late afternoon (about getting the speaker out) and they responded this morning. Very impressive!

Phil can't help living in Birmingham. Maybe he was born there - or maybe he has to live there because of his job. *Don't* hold it against him: he is a standup bloke. Sold me an excellent Ashdown ABM cab. Haggled in a very civilized way, packed it up really well, called me up to advise of progress, and was a pleasure to do business with. Thanks, Phil.

Don't even think of it - it would be money down the drain! Plastic handle, plastic corners, piezo tweeter. It's a cheap and cheerful home-made confection that should be on Freecycle. The single 3-inch port will fart when you play low-E. And it's filthy, which speaks volumes about its owner. I'll bet you the cabinet is made of chipboard and there's an old, cheap, pressed steel Eminence of Chinese driver inside. Avoid it like the plague and wait for something half-decent to come along.

[quote name='Bill Fitzmaurice' post='526719' date='Jun 28 2009, 02:15 PM']No higher than 1.5kHz. The axial response of the 15 may well go to 4kHz, though if it does go that high I'd be concerned about its low end, that's very much in the realm of a guitar driver. But irrespective of how high the axial response is any fifteen's response drops like a stone off-axis above 1.5kHz at best.[/quote] If you try to cross a tweeter over at 1.5kHz you'll blow it up within a few minutes. Most of them are designed to be crossed over between 4 and 6 kHz. A very few will go down to 3 with a steep crossover, but 1.5k is the domain of the 1-inch compression driver - and high-end compression driver at that. The crossover point for a tweeter is a function of its resonant frequency and the steepness of the crossover being used. Your Fane starts rolling off at 3KHz - so you should try for a crossover point of 4 or 5kHz, certainly no lower if you're just using a high pass.

[quote name='Protium' post='526297' date='Jun 27 2009, 09:39 PM']How do If I want to wire up an 8ohm tweeter with an 8ohm woofer do I need a full crossover or can I get away with just using a high pass filter @ 4kHz on the tweeter?[/quote] Unless you have measuring equipment, you don’t really have any option and it will be a bit hit and miss. Still, it can be done. What type of crossover were you thinking of using? Do you have specific drive units in mind? I’ll try to point you in the right direction if I can. Here's an example of somebody who's done it: [url="http://www.humblehomemadehifi.com/Bass-Rig.html"]http://www.humblehomemadehifi.com/Bass-Rig.html[/url].