Specs sheets and reality

Hello,

I plan to buil a woofer box to suplement my Alpair 10.3 . I know too little to choose a woofer based on solid grounds.
I like the Morel CAW 938.
My context of use will be 80 to 90 bB, crossed at 200 or 400 or 800 Hz. I will try all 3.

Later on I would like to get an ESS AMT and use it with the Morel crossed at 800 Hz.

What worries me the most is that Morel states the CAW 938 can handle high power. 80 to 90 dB is not so, will it perform very good at those lower levels ?

Thanks for your thaughts,

Walter
 
Power handling in HiFiwoofers is largely irrelevant.

There are tons of woofers used as midBass that will work well as helper woofers.

In a situation like this XO at or below (x 0.707) bafflestep diffraction F3 is a good place. That frequency depends (mostly) on the width of the box).

dave
Hi Dave,

Morel does not show F3 value and their graph stops at 100Hz.

The box will have to be 12 inch wide or more. Based on our discussion last month, I will try those cross over points: 200, 400 and 800.

Thx,

Walter
 
How can i see the performance differences based on specs only.
Walter,

The one performance difference pertinent to choosing a subwoofer easily determined by specs only, when comparing those from one manufacturer is displacement, Sd x Xmax (linear excursion).
Morel uses a more conservative method to determine Xmax than some (many..) other manufacturers.

A quick estimate of usable linear displacement limited output levels for driver(s) in sealed enclosures can be found here:
http://www.baudline.com/erik/bass/xmaxer.html
Excursion.png


You mentioned an 80 to 90 dB SPL level, the Morel 938 could reach near that level in it's linear range at 30Hz, while the smaller Sd 638 with less Xmax would have ~6.8 dB less clean output level.
A 5dB level change at 30Hz sounds about half as loud.
90dB at 30Hz sounds near equal loudness to 40dB at 1kHz.

Crossed at 200Hz at 90 dB, the Alpair 10.3 excursion would be a fraction of a millimeter.

Art
 
Walter,

The one performance difference pertinent to choosing a subwoofer easily determined by specs only, when comparing those from one manufacturer is displacement, Sd x Xmax (linear excursion).
Morel uses a more conservative method to determine Xmax than some (many..) other manufacturers.

A quick estimate of usable linear displacement limited output levels for driver(s) in sealed enclosures can be found here:
http://www.baudline.com/erik/bass/xmaxer.html
View attachment 1309850

You mentioned an 80 to 90 dB SPL level, the Morel 938 could reach near that level in it's linear range at 30Hz, while the smaller Sd 638 with less Xmax would have ~6.8 dB less clean output level.
A 5dB level change at 30Hz sounds about half as loud.
90dB at 30Hz sounds near equal loudness to 40dB at 1kHz.

Crossed at 200Hz at 90 dB, the Alpair 10.3 excursion would be a fraction of a millimeter.

Art
Very informative, thanks a lot.

walter
 
Dave,

A woofer designed for sealed box use can't make low bass without "moving air", and a full range driver will sound distorted if it is forced to move too much.

The 938 spec sheet gives a graphic representation of it's sensitivity, ranging from ~83 at 100Hz to 87 at 800Hz.

938 Sensitivity.png
 
How much air does it need to move to satisfy the OP?
I can only guess at what would satisfy anyone else, why ask me ?

If the OP wants 90dB at 30Hz, it would require ~9.5mm peak to peak excursion from a helper woofer with the Sd the Morel 938 has, as you can see in post #10.
That would be a displacement volume of 2080 cubic cm.
The larger driver produces lower bass and has the displacement to back it up.
Any driver may be equalized to produce bass as low as one desires.
A larger driver with more excursion can produce more lower bass, as previously noted in post #10 .