need help choosign subs

Further more, even if you feed the Brahma the maximum RMS power (1600w right?), it would still "only" play at 114.1 Db. That just plain sucks. If I feed my Cerwin Vega the maximum RMS power (500w), it will play at 127Db. Also, from what I've found out on the Brahma, it has a 29mm one way excursion, that means that it has a peak-to-peak excursion of 58mm? I don't like the idea of have the cone moving back and forth that far. By upgrading to a 15in, you could reduce the excursion ~25% and still get the same acoustical output.

It's not all about sensitivity. But the higher the sensitivity, the less power you have to put into the driver to get the same output level. And the less power you put into a driver, the less chance there is for distortion to occur. I like to drive my speakers at %25 of there RMS power rating. This allows that to play extremely clear. Now, I am not saying that when I put the full RMS power into them that they distort, it is a known fact that under-powering a driver will allow it to play more clearly.

Poormanq45 wrote: The efficiency/sensitivity on those subs is a little too low for my liking. I don't recommend getting any Speakers/Drivers/Woofers/Subs that have a efficiency/sensitivity lower than 92Db 1w/1m. I would recommend anything from Cerwin Vega. I recommend looking at these sites: http://www.adelcom.net/CerwinVegaSSSubs.htm http://www.adelcom.net/CerwinVegaVSSubs.htm http://www.adelcom.net/CerwinVegaStealthBX.htm http://www.cerwinvega.com/products/mobileaudio/index.html

You don't want to base your decision strictly on efficiency.  For one thing, there are many different ways to measure efficiency.  Some companies actually measure efficiency at 2.83 volts (4 ohm coils so not a 1 watt measurement) at half a meter and in vehicle.  It makes their subs look really efficient, but it is kind of cheating.  I'm not sure how CV rates their efficiency. 

Also, to gain a high efficiency, there had to be some compromising elsewhere.  The sub either requires a much larger enclosure for a given alignment, or gives up low frequency extention. 

Sure our Brahma's aren't very efficient.  But power is cheap, and we figured a smaller enclosure would be a better design goal.  And as stevdart pointed out, a lot of other companies went this direction as well.  

Steven Kephart

Adire Audio

Poormanq45 wrote: Further more, even if you feed the Brahma the maximum RMS power (1600w right?), it would still "only" play at 114.1 Db. That just plain sucks.

How do you figure that?  I will guarantee you that you can get a whole lot louder than 114 dB with 1600 watts to the Brahma.  Heck, I've metered my Brahma 10 in a .36 cubic foot sealed enclosure at 143.7 dB.  And that was with only about 1200 watts.

Poormanq45 wrote: Also, from what I've found out on the Brahma, it has a 29mm one way excursion, that means that it has a peak-to-peak excursion of 58mm? I don't like the idea of have the cone moving back and forth that far. By upgrading to a 15in, you could reduce the excursion ~25% and still get the same acoustical output.

  

Why not get a 15" Brahma then?

Steven Kephart

Adire Audio

Ya, I understand that companies use different ratings. I have a decible(can't remember real name) and power meter that I use when testing electrical equipment. I hooked up the power meter between the amp and the sub. And I placed the decibel meter ~3ft infront of the sub. (*Note: this was all done outside of the car.) The decibel always showed within 2Db of the rated efficiency at every power input level. So, I think the rating is pretty accurate. Cerwin Vega has been around for a while. There Sound quality is tried and true. "Also, to gain a high efficiency, there had to be some compromising elsewhere. The sub either requires a much larger enclosure for a given alignment, or gives up low frequency extention. " A higher efficiency can also be gained by: using a lighter weight cone, using a larger(greater magnetic flux) magnet, and/or using a tighter woven.larger voice coil. Hear is an exerpt from a thesis I wrote a while back: "One of the major disadvantages of the low efficiency that often is not readily detected by the novice is the limitation it places on any chance to use a bass-boost control on the amplifier (often desirable because of a poor listening room and/or recording)." Consider a system that is 1-percent efficient. To produce 100-db spl at eight feet would require forty electrical watts from the amplifier (100-db spl at eight feet requires 0.4 acoustical watt from the speaker). Suppose still further that a 60-watt amplifier is being used-real continuous watts, not music power, peak, or other short-term values. In quality amplifiers, a 12-db bass-boost capability is usually considered conservative. A mere 6-db boost in bass response requires 160 electrical watts (40 watts times four), 100 watts more than the 60-watt amplifier can provide; 12-db boost would require 640 electrical watts. This means that the bass-boost controls are not really usable with the speaker selected.

"How do you figure that? I will guarantee you that you can get a whole lot louder than 114 dB with 1600 watts to the Brahma. Heck, I've metered my Brahma 10 in a .36 cubic foot sealed enclosure at 143.7 dB. And that was with only about 1200 watts." I didn't actually go into an indepth calculation of the Db. I only used the standard 3Db increase requires a doubling of power.

Poormanq45 wrote: It's not all about sensitivity. But the higher the sensitivity, the less power you have to put into the driver to get the same output level. And the less power you put into a driver, the less chance there is for distortion to occur. I like to drive my speakers at %25 of there RMS power rating. This allows that to play extremely clear. Now, I am not saying that when I put the full RMS power into them that they distort, it is a known fact that under-powering a driver will allow it to play more clearly.

You are forgetting something though.  Efficiency and power handling are dictated more by the enclosure used than the sub itself.  You can get the Brahma to full excursion with only 600 watts in the right size enclosure.  Also, the Brahma uses our XBL^2 motor which means it will naturally have less distortion.  It isn't like a standard subwoofer where distortion increases as you turn it up.  The Brahma stays clean up until it's moving 50 mm peak to peak.  Take a listen to one and you will see what I mean.

Steven Kephart

Adire Audio

Steven Kephart: wow, I just realized that you work for Adire.

Poormanq45 wrote: Cerwin Vega has been around for a while. There Sound quality is tried and true.

Yeah, but they mainly do pro sound where efficiency is important, and enclosure size isn't really an issue.  There is a reason why most car audio companies don't have high efficiency as their main goal.

Poormanq45 wrote: A higher efficiency can also be gained by: using a lighter weight cone,

Which also raises Fs, thereby decreasing your low frequency extention.

 

Poormanq45 wrote: using a larger(greater magnetic flux) magnet,

Sure, which decreases your Qts and increases your Fs, again decreasing your low frequency extention. 

Poormanq45 wrote: and/or using a tighter woven.larger voice coil.

Actually that would add more weight which would decrease your efficiency.  You just can't beat Hoffman's Iron Law.  If you want high efficiency, you must sacrifice either extention or enclosure size.  There is no way around it.

Steven Kephart

Adire Audio