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Discussion Starter #1
Hello all, I have what is probably a very basic question, but one that I don't know the answer to. I have an Infinity Kappa Perfect 12 DVQ sub. Unfortunately I only have the BASH 300 (parts express) powering it. With the DVQ I am only running 150 watts RMS to the woofer. It actually sounds great with music but clearly needs more power for HT. So here is my question.

Does more watts RMS mean-

More excursion

More volume

Or both, and are they neccessarily independant or dependant on another?

Thanks for the help. (Long time lurker)
 

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My understanding is that with higher RMS means the cone can take more power before distortion/breakup.
Then coupled with more Xmax will give you higher SPLs.

So the higher the Sensitivity,
greater the RMS,
and the geater the Xmax,
more power
should = higher SPLs
 

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The sensitivity (SPL rating) of a particular driver is a measure of its efficiency. The higher the number, the less power will be required to drive it to a particular volume level. This is not directly related to power handling or xmax. All of the parameters of the driver come into play. A driver rated at 85 dB 1W/1m means that it will produce a measured volume level of 85dB with 1 watt of power input at 1 meter distance. The measured volume level will increase with power input and decrease with distance from the driver.

From my experience, Xmax is the limiting factor for playing any driver at low frequencies. At the low end of the frequency range, most drivers will be Xmax limited, not power limited. A well designed ported sub can mitigate that problem quite a bit.

Power input is directly related to volume level. Double the power, double the volume for a given speaker. Each doubling of power creates a 3 dB raise in volume (measured SPL, not the driver rating). However, a driver that can handle more power can only provide higher volume levels if it doesn't have a low SPL rating or limited Xmax.

Here' how it all ties together. All things being equal, a driver with a 3dB higher SPL rating will play twice as loud for a given input power. Again, all things being equal, would you rather pay for 1000W amp and an 85dB1W/m driver or a 500W amp and an 88dB1W/1m driver. Furthermore, that 85dB1W/1m driver will have to handle higher excursions to produce that same volume level and therefore reaching its Xmax limit at low frequencies before the 88dB1W/1m driver. So, a low SPL rating means you need a higher Xmax and more powerful amps to produce peak volume levels.

None of these ratings are more important that the others, you just need to understand how they all interact to choose an adequate driver for your purpose.
 

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My understanding is that with higher RMS means the cone can take more power before distortion/breakup.
Then coupled with more Xmax will give you higher SPLs.

So the higher the Sensitivity,
greater the RMS,
and the geater the Xmax,
more power
should = higher SPLs
no, high RMS means that the voice coil can handle more watts without overheating/burning. Mechanical limit(xmech) depends on the enclosure, source played and the driver itself.

sens:
With my experience, low sensivity subs needs more power but sounds better IMO, you tend to have more headroom, volume play, but thats just a feeling you get I guess about low sens subs... high sensivity subs are a lot easier to run powerwise, but reaches their xmax and xmech quicker(not saying it doesnt sound good at all) ...
high xmax and xmech:
Also, a high xmax sub sounds better , you get lot more headroom, subs with lot of excursion has more playground to play with, thus the sound tend to be more confortable to the ear IMO, more "round" and cleaner....
 

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Furthermore, that 85dB1W/1m driver will have to handle higher excursions to produce that same volume level and therefore reaching its Xmax limit at low frequencies before the 88dB1W/1m driver. So, a low SPL rating means you need a higher Xmax and more powerful amps to produce peak volume levels.
This is not a true statement. A 94db rated driver and an 87db rated driver with the same SD in the same sealed box both at 10mm excursion will produce the same SPL. The power required to make each driver produce that excursion will be different.
 

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no, high RMS means that the voice coil can handle more watts without overheating/burning. Mechanical limit(xmech) depends on the enclosure, source played and the driver itself.

sens:
With my experience, low sensivity subs needs more power but sounds better IMO, you tend to have more headroom, volume play, but thats just a feeling you get I guess about low sens subs... high sensivity subs are a lot easier to run powerwise, but reaches their xmax and xmech quicker(not saying it doesnt sound good at all) ...
high xmax and xmech:
Also, a high xmax sub sounds better , you get lot more headroom, subs with lot of excursion has more playground to play with, thus the sound tend to be more confortable to the ear IMO, more "round" and cleaner....
RMS= root mean square

but your right I shouldn't have suggested the cone but maybe the driver.


But high xmax sub would have little head room without an abundance of power,again its not soley just xmax.

Oh also not to forget cone area,it also makes a huge difference.
 

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This is not a true statement. A 94db rated driver and an 87db rated driver with the same SD in the same sealed box both at 10mm excursion will produce the same SPL. The power required to make each driver produce that excursion will be different.
I did some modelling of different drivers, but entered the same Sd and he's right. I retract the statement and get skoold.
 

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Discussion Starter #9
Thanks all, so to clarify, and to possibly raise some eyebrows here... My Infinity sub has an RMS of 400 and a peak of 1400. In WinISD it reaches Xmax at roughly 400 watts. Why would I want to use a Behringer 2500 to power this sub if a far lesser amp will reach the woofers Xmax? (Am I making any sense here?)
 

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Thanks all, so to clarify, and to possibly raise some eyebrows here... My Infinity sub has an RMS of 400 and a peak of 1400. In WinISD it reaches Xmax at roughly 400 watts. Why would I want to use a Behringer 2500 to power this sub if a far lesser amp will reach the woofers Xmax? (Am I making any sense here?)
You wouldn't need an EP2500 for that driver. It could be used if your are careful not to overdrive the sub. The amount of power needed to reach xmax and the freq's it is reached at varies greatly depending upon the enclosure design. 400w rms is supposed to be the long term thermal rating of the driver and doesn't really relate to the xmax. Also those specs are notoriously sketchy. You can usually use an amp with 150% of the RMS rating on a driver, or more, without much concern, as long as you don't exceed xmax, or do it on a really long extended basis.
 
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