Extention cabinet question

[bigcardinal]

I have a Yorkville XM200 combo that I would like to add an extention cabinet to. It will put out 200w @ 4 ohms when the extention is attatched. One of the cabs I have looked at is rated to 150w @ 8 ohms, which might be cutting it a little close (no headroom, I'm assuming). The other can handle 600w @ 4 ohms, obviously no risk of damaging it here.

My question is, is too much headroom a bad thing? And how close can I cut it? is the 150w cab a bad idea. Let me know what you think cause I am new to all this. Thanks!

 

[cheezewiz]

Its not a bad idea per se. Most cabs can handle more than the rated power, however, practically, a cab rated to handle only 150 watts is probably a piece of crap and you may want to look elsewhere. In the setup you are considering, each speaker (the one in your combo, and the extension) will only get 100 watts. You also need to watch your ohm load. Its very possible your combo may be made to use an 8 ohm extension only. One more point,...headroom usually refers to the power your head puts out, not the power your cab can handle. Having alot of headroom is almost NEVER a bad thing.

 

[bigcardinal]

thanks for your help...and for clearing up the headroom thing. The guys at the store told me that the combo by itself is 200w @ 8 ohms, but that actually it is probably only around 165w by itself, but by adding another cab, then both the internal speakers and the cab will be driven at 200w each @ 4 ohms...does that sound right??

 

[cheezewiz]

thanks for your help...and for clearing up the headroom thing. The guys at the store told me that the combo by itself is 200w @ 8 ohms, but that actually it is probably only around 165w by itself, but by adding another cab, then both the internal speakers and the cab will be driven at 200w each @ 4 ohms...does that sound right??

No, thats not correct. I just looked up the XM200 combo on Yorkville's website. I'm guessing you have the model with two 10 inch speakers since you used the term "internal speakers" Here are the specs:

Combo Bass Amplifier
Cabinet Impedance (Ohms) 4
Power @ min. impedance (Watts) 200
Minimum Impedance (Ohms) 2
Burst Power - 2 cycle 250
Speaker Configuration - LF (Size / Power) 2 x 10 inch
Speaker Configuration - HF (Size / Power) Piezo Tweeter
Hum and Noise (dB) -90 dB Unweighted / -94dB Weighted
Input Channels 1
Channel 1 - inputs 1/4 inch phono jack
Channel 1 - controls Volume, Bass, Lo-mid, Hi-mid, Treble, Contour
Channel 1 - switches Limiter, DI out pre/post EQ
Input Sensitivity (mV) 25
Line Out (type / configuration) XLR pre or post EQ
Line Out Sensitivity (Vrms) 1.0
Effects Loop / Location Yes / Front
LED Indicators Power
Protection Thermal / Short Circuit
Limiter / Switchable Yes
External speaker output / location Yes / Rear
Headphone Jack Yes
Other Features XC115X Single 15 inch Extension cabinet is ideal mate for XC200 / XC200T
Dimensions (DWH, inches) 14 x 22 x 23.5
Dimensions (DWH, cm) 36 x 56 x 60
Weight (lbs / kg) 64.

If this is your amp, the combo itself....that is running alone, with the two 10s, is a 4 ohm amplifier. The store is probably correct in that without an extension, it'll be about 150 watts. However, if you ad a 4 ohm extension cabinet, your load will now be 2 ohms, which is apparently ok according to the specs. At this 2 ohm load, you will be running 200 total watts, between both cabs.

 

[permagrin]

"a cab rated to handle only 150 watts is probably a piece of crap"

Now now, not necessarily true, I had a pair of GK 115s that were rated at 200W and were great cabs, also had a GB 112T rated at 150W that was not bad at all.

The specs say your internal cab is 4 ohm, and that the amp puts 200W into 2 ohm. If you add an 8 ohm extension cab, the total load on the amp will be about 2.67 ohm - you'll probably draw about 180W, with 2/3 of the power going into the internal 210, and 1/3 (about 60W) going into the extension cab. If you add a 4 ohm cab, the total load on the amp will be 2 ohm, you'll draw the full 200W from the head and it will be split evenly between the two cabs (100W to each).

In general you're best matching the power of a head to the power handling capability of the cab. Too little power to a high power cab won't give it a chance to "bloom", and too much power can of course fry it. There's quite a bit of room on either side, and it all depends on how you play and a bunch of factors, but in general I don't like to give a cab less than .75x its rated power or more than 1.5x.

You're only going to be in danger of damaging your gear if you drive it to extremes. Overpowering a cab (say, putting 500W into a cab rated at 250W) can damage it if you use it too loud. Underpowering a cab (say, putting 250W into a cab rated at 500W) can damage it if you use it too loud. So again, best to match specs as close as possible, and have enough power and speaker area (and efficiency, etc.) to suit the application. As a systems engineer we're taught early on that in most cases systems fail 1) at their interfaces and 2) at their performace extremes - the moral for bass players is use good cables and don't push your gear too hard.

The question then is why do you want to add an extension cab? If it's to give just a little more oomph to round out your tone, adding a cab will draw a bit more power and the additional speaker area will give you somewhat more volume and fullness. If it's to add significant volume to your rig, unfortunately you're not going to get there; the head wasn't made for high volume situations.

 

[bigcardinal]

Thanks guys, you've helped out a ton!