stevie

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].

[quote name='Mr.T' post='524612' date='Jun 26 2009, 09:34 AM']Is it even a fair shoot-out?[/quote] It's only a fair shoot-out if you realize that the two types of cab offer different benefits. *All things being equal* (and I'm not referring to any brand here), a 15" will be louder and go lower. It's maximum output will also be greater. A 12" will be more compact and thus easier to transport. It will also have cleaner mids, a more extended high frequency response and a slightly better off axis response. Which is better will often depend on what you're looking for.

[quote name='alexclaber' post='524841' date='Jun 26 2009, 01:52 PM']I don't think anyone who's bought one has directly replaced a GS112 with a Compact. An Epifani UL112 owner who recently got a Barefaced Compact said this: "Having had the Compact a few days now and used it for two rehearsals yesterday I can confirm that it is superb smile.gif Just has so much more depth that my Epifani 1x12, much fuller across the whole range, punchier, lighter and a lot louder (I know it's not a fair comparison but even so). I've used the mid and treble eq on my Overwater in a way I never had before - the amp is set flat as usual but I can dial in mids and top end without it sounding all edgy and harsh. My new passive Fender Jazz sounds great through it too - so all in all extremely happy" Alex[/quote] The question wasn't about the Epifani UL112 but that's another nice plug for your product. Alex, how would you like it if other speaker manufacturers came on here and trashed your stuff?

That is such a brilliant album (apart from that awful Windmills track) with some very tasty bass playing.

[quote name='JTUK' post='511592' date='Jun 11 2009, 08:42 PM']Yes, nothing to put them in.....and I did indeed think about getting some 1x15 cabs made....never got round to it and I have that base ( no pun int' ) covered now... I'll dig them out and see what they sound like... and then put them on here for offers[/quote] That's a good idea. You haven't got any 2206s that you would like to dispose of (very cheaply) have you?