Wattage Compatibility

[sandcharlton]

I am considering building a small subwoofer with the MTX Rt10-44 woofer rated at 200/400 watts and the 120w amp (#300-792). Do I have a problem with wattage? Is there a rule of thumb I should follow?, and does my receiver wattage, which will be powered seperately, need to have a minimum? (Denon DRA 275 at about 50/channel)

thanks

[j_dunavin]

i used a 300 rms woofer with the 240w plate amp. You'll in no way do any damage by placing a higher rated woofer on a lower rated amp.
Now your receiver should have a preamp out to the sub amp which is a very low level.

[nathan]

A good rule of thumb is that you can over power a woofer by 50%. So if your woofer is rated at 200W Rms, then you could power it with a 300W amp.

But be careful of underpowering your sub. You shouldn't have to run an amp wide open to get respectable volume. This can very quickly lead to a blow driver!

[surroundu]

Since this appears to be for home use, you might consider the use of other subwoofer drivers. (Unless you already have the MTX) Assuming you haven't bought it yet, you should consider the 8" or 10" (or 12", but it will be larger) Dayton Shielded DVC. They are well under the cost of your MTX. And, 120 watts can drive them all.

> I am considering building a small subwoofer
> with the MTX Rt10-44 woofer rated at 200/400
> watts and the 120w amp (#300-792). Do I have
> a problem with wattage? Is there a rule of
> thumb I should follow?, and does my receiver
> wattage, which will be powered seperately,
> need to have a minimum? (Denon DRA 275 at
> about 50/channel)

> thanks

[Paul O]

> But be careful of underpowering your sub.
> You shouldn't have to run an amp wide open
> to get respectable volume. This can very
> quickly lead to a blown driver!

I don't mean to jump on you Nathan, but I feel I must point out this common mis-application of an otherwise valid statement.
Driving an amp that is rated less than a speaker's power rating to clipping levels, can lead to driver failure, but it's rarely a low frequency driver that dies. Usually the more fragile mid and hi frequency drivers fail in this situation.
A heavily clipped amp may produce twice the power it is rated for, and a lot of that extra energy will be at higher frequencies. It's this extra hi-frequency energy that over heats the relatively small mid and hi voice coils in a full range system, they may see 2-3 times what they normally would, and this quickly leads to over heating and failure. The low frequency drivers are protected by the crossover to some extent, may only see a moderate power increase, and have much heavier voice coil windings, so they should have an easier time dealing with mild over powering from a clipped amp, if in fact they are over powered at all.
That said, a sub always sounds better with a bigger amp, up to twice it's power rating. A bigger amp will have full control of the driver at half throttle, and thus sounds better than a smaller amp at it's limit.

[Dirk]

> I am considering building a small subwoofer
> with the MTX Rt10-44 woofer rated at 200/400
> watts and the 120w amp (#300-792). Do I have
> a problem with wattage? Is there a rule of
> thumb I should follow?, and does my receiver
> wattage, which will be powered seperately,
> need to have a minimum? (Denon DRA 275 at
> about 50/channel)

Simple answer: Don't give the woofer more power than it can MECHANICALLY handle.

RMS numbers are useless as teats on a boar. I will make a blanket statement that, except in rare cases, a woofer will beat itself to death LONG before the voice coil itself melts down. I've seen subs capable of 250W RMS destroyed in seconds by a quick low-frequency sweep from a 120W amp (Monsters Inc, in the "laughing boo" scene).

Woofers (especially subs) make noise by moving. A lot. As power goes up, so does the woofer's need to move. If you put the woofer in too large of a box, it will flap around and could possibly be damaged by as little as 50W, possibly less. To make sure this doesn't happen, you really need to get some decent box design software and the FULL T/S parameters of the driver. Check out WinISD Pro Alpha from <A HREF="http://www.linearteam.dk">www.linearteam.dk</A> and see if you can find the full T/S values from the MTX website. You'll need Qes, Qms, Vas, Fs, Sd, Re, and Mms to be able to calculate excursion at given powers. If you get the T/S params and don't know what to do from there, come on back and we'll see what we can do from there.

The other option is to just build the damn thing as you plan and be careful with the volume knob until you learn what it can and can't do. A sub will sound UGLY as it nears it's limits. :-)

[duanebrown]

> I am considering building a small subwoofer
> with the MTX Rt10-44 woofer rated at 200/400
> watts and the 120w amp (#300-792). Do I have
> a problem with wattage? Is there a rule of
> thumb I should follow?, and does my receiver
> wattage, which will be powered seperately,
> need to have a minimum? (Denon DRA 275 at
> about 50/channel)

> thanks
Hi, please don't get mad at me, but I don't think this is a good idea.
I have a infinity 1010w sub setting behind me that sounds, um, worse than no sub at all. fs and xmax specs are very close to your mtx. (Please note it sounds very good in my car.)
This is because of cabin gain.
FWIW: that amp has a Bass boost of 6 dB @ 30 Hz
IF I modeled it correctly this will make your sub reach xmax at about 25 Watts if it is in a 2cf box. in a .8cf box the sub should be able to handle all 110 watts but with a f3 of 46HZ.

it's late so this might not make any sense.