melando

[quote name='subdude' timestamp='1331662312' post='1576829'] it is a 10" speaker [/quote] In that case, it looks like a PA type bass/midrange unit designed more for a flat response. It would probably work ok but it is likely to sound a bit dull and maybe a bit slow. Along with the high moving mass the sensitivity is a little low but if you're not after huge output levels that shouldn't be a problem. The suspension is probably a bit more compliant than that of a bass guitar driver so you need to be careful about thumping it too hard with low bass notes. It looks suited to a ported box of of around 30-40Litres per driver with the box tuned to around 65-70Hz (or lower depending on the cone excursion). So, not ideal, but should work ok if you don't go crazy with it. As well as the Eminence site, there are useful driver datasheets on the Celestion website.

What size unit is the data for? The moving mass and Vas are a bit high for a 10". Is it a 15"?

[quote name='xgsjx' timestamp='1331505161' post='1574002'] I wouldn't have thought it would have made as much a difference as that. Part due to the fact that it's getting pushed by 1/2 the power that the 2x10 combo is & although it will make some sort of a difference, would it not depend on the sensitivity & so on of the ext cab? Edited to tidy up grandma [/quote] The extension cabinet will indeed see half the power that the internal 2 x 10" system does as, being 8 ohm instead of 4, it will only draw half the current. The acoustic output you get for that though, is significant, it's around half what you are getting from the 2 x 12", around -6dBspl. Adding them together, 0dB + -6dB = +3.5dBspl. Add a dB more because a 12" unit is generally a little more sensitive than a 10" (as I mentioned above) and you get around +4.5dBspl. The 2 x 10" system will sound louder than the 1 x 12" extension cab so the the bulk of the sound will still appear to be coming from that, but the total will be 4.5 dB louder - which is the increased headroom desired. And the amplifier has the power output to deliver this.

Maybe I should re-phrase that ...

In sound pressure level terms I think you should expect and increase of around 4.5dB. That should be easily noticable, and the effect will be enhanced because you'll have two cabinets working together giving a bigger source size. Definitely worth trying. For those interested, my calculation runs as follows: Internally, you probably have 2 x 8 ohm 10" units in parallel giving a 4 ohm load and an output of, let's say, 0dB. Adding another identical 2 x 10" speaker system will give +6dB (2.0 in linear units) in sound presure level and will halve the impedance to 2 ohms. A single 8 ohm 10" speaker will have a relative output of -6dB SPL (or 0.5 in linear units) compared to the 2 x 10 system. Adding this in parallel with the internal 2 x 10" should increase to output by 3.5dB SPL. (or 1 + 0.5 = 1.5 in linear units) A equivalent 12" driver should have a dB or so of extra output than a 10" so I would expect that adding a 1 x 8ohm 12" system will increase the output by around 4.5dB.

It is worth checking that the drivers available to you are designed for bass guitar use, as distinct from PA, or indeed guitar. It is not always obvious from the spec sheet. Then make sure you're comparing drivers of the right impedance - I assume you'll be using two 8 ohms units in parallel to make a 4 ohm system, although you might want to think about this - if you plan to add extra cabinets later or your amplifier has limitations in terms of the impedance it can drive. Then consider whether you will make a closed box or ported cabinet - drivers suitable for one will generally not be ideal for another. A driver with a qts of less than about 0.45 will generally be optimised for use in a ported cabinet, above 0.45 for a closed cabinet. Drivers for use in a closed cabinet will also generally need a higher xmax due to the increased cone excursion. Check also the the drivers have a high enough power handling for the use they're going to get. Good luck.

Be carfeul, becuase the shaft diameters of different pots are not necessarily the same. I replaced a solid shaft pot on my MIM precision with a seemingly equivalent CTS one and then found the knob wouldn't fit.