stevie

I think we have an echo in here. Follow this link for a JBL cab that is just a bit bigger than yours: www.jblpro.com/pub/obsolete/4646a.pdf. It's 34 litres compared with your 28 litres - a difference, but not a deal-breaking one. It contains a JBL 2206 driver which models very closely to yours in the same-size box. You'll notice there are two 70mm ports at the front. JBL built thousands of these and it is a well-proven, compact sound reinforcement bass cabinet, specifically designed to accept bass boost. JBL fitted this particular 12" driver to smaller cabs (the Soundpower 1725 was only about 20 litres if I remember correctly) as well as to bigger ones. I happen to have one of these cabs at home - it's a nice size for tucking under the piano. I have the original JBL speaker but have also fitted a number of other 12" drivers, including a Celestion neo, which is in there at the moment and which sounds great. You are, of course, free to build another cabinet to put your Beyma into as Bill seems to be insisting ad nauseam that you do. But if, as you say, you're happy with the sound of your present cabinet, adding a second port will allow it to go louder before the onset of nasties.

I did a similar conversion with a 2 x 10 Laney cab not so long ago. I swapped the drivers for better ones and put a 4" rear port in the back where the crappy input panel had been. I then fitted a Speakon input socket on the back. It completely transformed the cab, as its new owner will testify. And it looks professional.

You're thinking along the right lines. What I suggest you do is this. Close up the hole at the front of the cab using a piece of plywood (or put the tweeter back in). Then fit two of these ports to the back of the speaker: [url="http://www.falconacoustics.co.uk/cabinet-parts-accessories/bass-reflex-port-tubes-loudspeaker-grille-mounts-dowels-calculation-sheet/bass-reflex-port-tube-standard-reflex-66mm.html"]http://www.falconacoustics.co.uk/cabinet-p...eflex-66mm.html[/url] The theory says that you should leave a gap equivalent to the diameter of the port between the end of the port tube and the back panel of the box. I'm not sure quite how rigidly you need to stick to that, but the ports are adjustable in length anyway - so if you want to experiment you can. Moving the port close to the back panel will drop the tuning slightly but will also cause turbulence. The ports I've suggested are just under 3 inches in diameter and will therefore give you a usable tuning at around 170mm long while still maintaining a reasonable vent air velocity. The benefit of doing it this way is that the cabinet will still look good when you've finished. One port at the front and one at the back would be a bit of a bodge.

[quote name='Bill Fitzmaurice' post='1032706' date='Nov 22 2010, 03:00 PM']There's nothing the least bit magical about sealed cabs. Most cabs in the 60s were sealed not because they sounded better but because most of the drivers available didn't work any better in vented alignments. Designers/manufacturers who still create sealed cabs don't do so because they're better, they do so because they sell, mainly to customers who think there's something inherently better about the tone of a sealed cab.[/quote] I'm not sure what cabs in the 60s has got to do with anything, but here's one of those customers who thinks there's something inherently better about the tone of a sealed cab. "[i]What are your thoughts on closed box vs ported for mastering in a properly treated room, especially with bass heavy music?[/i] This is a real sore point with me. As far as I'm concerned, every ported speaker I've ever heard, even the ones purportedly optimized for perfect Thiel/Small performance, has "looser bass" and usually some kind of hidden or obvious resonance and often compromised dynamics. …… And since mastering should employ an absolute reference speaker, then ported has to be out, unless someone out there can name an exception to the rule that I have not yet auditioned. People come from miles around to listen to and marvel at my system, which has been quoted as having the "tightest, flattest bass around". My Reference 3As are ported, (which I used before I moved to the Lipinski plus JL sub), and demonstrate to me time and again that the 3As definitely were an interim mastering solution. They now sit in the alternate listening room to prove to one and all that you can easily manufacture artificial bass with a port! Bob Katz

[quote name='4 Strings' post='1032011' date='Nov 21 2010, 10:35 PM']I read here: [url="http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=42234&highlight=jdruley"]http://db.audioasylum.com/cgi/m.mpl?forum=...ghlight=jdruley[/url] that someone had worked out a 4" dia tube around 3" long.[/quote] That cab size is 46 litres and he's tuning it to 62Hz. Your cab is only 28 litres - and you really want to tune it lower than 62Hz for bass guitar. As you reduce cabinet size, you have to make the port longer if you want to keep the port diameter and tuning frequency the same. Lowering the port tuning frequency also means lengthening the port. That's why my suggestion is longer than the one you've quoted: it's because your cab's smaller. A 100 x 200mm port will tune your cab to about 55Hz (and reduce the vent air speed considerably).

[quote name='4 Strings' post='1032011' date='Nov 21 2010, 10:35 PM']I have no idea about ports, would I need one a foot long?[/quote] 3in will tune much too high in your cab. You could get away with one that is 200mm long, but any longer is a bonus.

I've checked out the Beyma. It's a nice driver. A bit old but good quality. You're not really going to get anything better from Celestion of Fane. However, unless it's faulty, the driver is not your problem. It models OK in your cab - up to its power rating it is comparable with the JBL 2026, which is known to work well in a small box. There is not a lot of low bass, but power handling is good and you can always eq. It is likely to give you lots of slam. From the information you have supplied, my guess is that your port is causing the problem. IMO, what you are describing as breakup is actually your port overloading because it is not big enough. You can check for this by putting your ear up to the port and playing a bottom E at high power. You will hear 'chuffing' / wind noise coming from the port. A 3-inch port is not much use in a cab this size because port overload will happen quite early on. The alternative is to increase the size of your port. If you can increase it to 4in diameter (or add a second 3in port), it should help with the problem. Unfortunately, doing this increases the port length to 300mm, which is quite substantial. It will probably need a bend, and will rob you of some of your cab volume. This is a constant problem with small, high power cabs.

[quote name='LawrenceH' post='1030994' date='Nov 20 2010, 11:18 PM']It's 1 louder[/quote]

[quote name='LawrenceH' post='1030495' date='Nov 20 2010, 03:10 PM']It really depends what the original driver is, whether it's worth replacing or not. Is it possible to find out?[/quote] 4 Strings says it's not the original - so he is likely to know. I'm also wondering if it's a 4-ohm driver.

[quote name='neilb' post='1029584' date='Nov 19 2010, 04:43 PM']You cant say that correctly!!!! LOL Its [i]la[/i] bouche ....(feminine)[/quote] But he also used the past participle instead of the second person imperative. Surely you noticed that!

If you're going to fit self-tapping woodscrews, I think it's good practice to drill pilot holes first. On pro gear, casters are normally fitted using t-nuts (on the inside of the cab) and bolts (around M6). You pays yer money. You may not need bolts and t-nuts but it's worth considering. Screwfix is usually a good source for this kind of hardware.

Interesting. They could have a winner on their hands. The styling looks good too, at least in the photos.

[quote name='Delberthot' post='1027773' date='Nov 18 2010, 11:34 AM']They've been getting some good reviews on Talkbs but they ain't for the hifi mob apparently. Meant to sound really rocky and aggressive which suits me down to the ground.[/quote] If you like the sound, that's an amazing price for a proper ply cab with a neo driver. Are they made in China?

Bought a cab from me. Prompt payment and no hassles. Great bloke.

[quote name='Bill Fitzmaurice' post='1025453' date='Nov 16 2010, 03:51 AM']But to say that if one's using four tens that the only way it should be done is to put them into a typical 4x arrangement is to ignore an alternative that most players who have actually tried prefer.[/quote] A bit of a strawman argument you're putting forward there, Bill, I’m afraid. Nobody is saying, or has said, that a 4x10 configuration is the only way it should be done. I’ve nothing against stacking speakers myself. It gets the top one closer to ear height as Thom mentioned a while ago, and this is the main benefit of the configuration. However, as Protium also pointed out, the seven foot tall 8 x 10 highlights the shortcomings of insisting on a vertical layout no matter what. What counts is what works.

[quote name='warwickhunt' post='1025225' date='Nov 15 2010, 09:23 PM']I'll take the driver out and see if I can find visible evidence and/or see if I can trial a replacement tweeter to trial/test it.[/quote] Post a photo if you can. Somebody might recognize it.

[quote name='Delberthot' post='1025219' date='Nov 15 2010, 09:19 PM']I've been thinking about something like this[/quote] There is a JBL Soundpower 12+horn in the Miscellaneous For Sale section for under £100 that will blow that out of the water. I can tell you that from personal experience because I've used them for a number of year. It doesn't have loads of bottom end, but it has slam in abundance and you can eq in as much low bass as you want to. Birch ply cab - 600W JBL driver with 4" coil and great xmax, 1" titanium tweeter. Compact. Very low distortion. I am not related to the seller. I'm just saying it's a great buy and it might suit you.

Sensible advice from icastle here. If there is a problem with the crossover, you should be able to see it. Crossover components don't normally fail without showing some visible signs of failure. It could also be a loose or frayed wire, or a poor solder joint - so check for those while you are at it. I'd be tempted to leverage the 10-year warranty. Otherwise, you will need to find out who makes the part and obtain a replacement or a replacement diaphragm. It will be a lot less expensive than buying from Aguilar if you can find out who made it. No first hand experience, unfortunately.

[quote name='Vibrating G String' post='1022192' date='Nov 13 2010, 09:27 AM'][url="http://richardwiseman.wordpress.com/2009/06/23/possibly-the-best-optical-ilusion-i-have-seen-all-year/"]http://richardwiseman.wordpress.com/2009/0...-seen-all-year/[/url][/quote] Whaaaaaaah..... that is indubitably the best optical illusion I have seen - ever. I'm still debating whether to believe it.

[quote name='MoonBassAlpha' post='1024588' date='Nov 15 2010, 01:29 PM']He's a German, and an audiophile. The chances of it being a joke are miniscule! [/quote] I hasten to add that the emphasis here is on audiophile and not on German. After all, we are all Europeans here, nicht wahr?

[quote name='ShergoldSnickers' post='1021863' date='Nov 12 2010, 08:47 PM']I don't think it's a question of 4x10s being wrong, so much as other alternatives being potentially better, if applied correctly. The crucial practical question is: How much better, and in which areas? Enough to matter? Matter to whom?[/quote] +1 Shergold. A very sensible post and a good summing up of how things are in the real world. I think the Bass Bash idea is an excellent one. Interestingly (or not, as the case may be), there is an almost identical thread running at the moment on Talkbass, with BF trying with mixed success to blunder everyone into submission by the frequency of his posts. KJung in particular has some interesting things to say. Gluttons for punishment should go here (but don't say I didn't warn you): [url="http://www.talkbass.com/forum/showthread.php?t=710206"]http://www.talkbass.com/forum/showthread.php?t=710206[/url]

[quote name='LawrenceH' post='1019568' date='Nov 11 2010, 12:40 AM']Not sure about fancy-pants Class D and H designs, which I'd imagine to be quite expensive to make well, but a lot of sound guys with semi-serious set-ups push out the low end watts with things like the EP1500 - they have quite a solid reputation, and reputedly their 2ohm claim is a bit more realistic than most cheap/mid-priced stuff.[/quote] I've not had much luck with Behringer gear myself, but I have to agree with Lawrence that their power amps, whilst certainly not the ultimate, have a good reputation with pro and semi-pro sound companies where budgets are tight.

[quote name='Bill Fitzmaurice' post='1015533' date='Nov 7 2010, 06:47 PM']One can run drivers horizontal so long as their center to center distance is less than one wavelength within the pass band. This basic law of acoustical engineering is almost universally ignored by the electric bass cab industry. (I doubt most manufacturers are even aware of it.)[/quote] That’s a bit different from “drivers should always be vertically arrayed” then. As to positioning drivers less than one wavelength apart, a one wavelength rule is hardly a basic law of acoustical engineering because interdriver positioning depends very much on what you’re trying to achieve. Bass cab companies seem happy with two wavelengths spacing (as in a 4 x 10). And since most bass players seem to agree with them, perhaps they’re not so ignorant after all.

I would personally take anything this chap says with a very big pinch of salt.