Looking to build my own 2x15 800w bass cab

[stevie]

[quote name='RIM Basses' post='751447' date='Feb 19 2010, 11:02 PM']Cheers for that Steve, Ok so how large is a 50 Litre Cab. Im gonna do the whole cab out of 18mm Marine Birch ply.[/quote]
The formula for volume in litres is Length x Width x Depth in centimetres, divided by 1000. Internal dimensions, of course. So, you could go for 42 height (dictated by the diameter of the speaker) x 47 wide x 28 deep. That gives you 55 litres and allows a bit for bracing and the driver volume. Adjust the sizes to whatever you prefer. Just avoid making any of the dimensions the same or simple multiples of each other (i.e. 30 and 20) to spread internal standing waves. The worst shape for a speaker cab is a cube.

With 18mm ply you probably won't need to brace it, but I'd consider putting two 2-inch deep, side-to-side braces across the longest length of the back panel. The stiffer the back panel, you more 'slam' you get, in my experience.

Edited February 20, 2010 by stevie

[Phil Starr]

Ooh there's nothing like a good tech debate. Is there something special about the relationship between bassists and speakers.

Regarding Xmax. Celestion give the length of the coil and the magnet gap and the difference between the two is how far the coil can move without coming out of the gap. The magnetic field extends beyond the gap a little way getting weaker as it goes so the further the coil and cone move the greater the distortion. It is not clear on the Eminence website how they calculate Xmax but two years ago they used the same method as Celestion.

I decided against Celestions because of the excursion/Xmax issues with my own speakers by the way. Why, if you are stuck on Celestions, dont you go for the BL series which have better excursion. Although they have conventional magnets you aren't going to notice the extra weight with your monster cab. The neo's are designed to have a light fast bass and they have sacrificed overall bass output to achieve a certain sound. You could also look at the Fane Sovereign range in this price bracket. (slightly cheaper actually)

If you cant get on with the software try this [url="http://www.ajdesigner.com/speaker/index.php"]http://www.ajdesigner.com/speaker/index.php[/url] which is dead simple, just type in the figures from the manufacturers spec sheets. Not as versatile as other programs but it will calculate the basic enclosure sizes and port dimensions and give you a frequency plot at 1W and full power.

Cheers

[Dood]

[quote name='dood' post='744302' date='Feb 13 2010, 08:28 PM']Interestingly, the ISP cabs I already use share a lot in common with the design - and indeed Alex's cabs - so I would probably be better off getting a matching extension cabinet for mine - but the 1515/66 would be pretty nice nevertheless.

There was a picture with the grill on somewhere - but I couldn't see it straight away when I posted. {edit - Here is is!}
[url="http://www.talkbass.com/wiki/index.php/Vlad335_1515/66_%22Monster%22"]http://www.talkbass.com/wiki/index.php/Vla...6_%22Monster%22[/url]

[/quote]


Right, that's it!!! We're gonna build one of these. I have a mate who wants to help!

[stevie]

[quote name='Phil Starr' post='753503' date='Feb 22 2010, 09:16 AM']Regarding Xmax.[/quote]
Phil, Eminence explain how they measure xmax somewhere on their website. It's not simple voice coil overhang. It's true they used to use the same method as Celestion but they don't any more.

Have a look at this Beyma speaker here: [url="http://profesional.beyma.com/ingles/pdf/12P80Nd.pdf"]http://profesional.beyma.com/ingles/pdf/12P80Nd.pdf[/url]
It has a voice coil overhang exactly the same as the Celestion, 4mm. Yet the stated xmax is 7.5mm - nearly twice as much. If you are going to compare xmax, you have to compare the same thing.