How much power for driving the woofer in an OB?

[ra7]

This is my first attempt at an OB. I'm trying to drive the eminence alpha 15 with the original t-amp and getting very little sound. Even with the t-amp at full volume, the woofers are not making any big sound.

The baffle is 2W x 4T. I have a way to pad down the output of the full range driver, but even with it all the way down, the output of the woofer is too little.

How much power is actually needed? Is the 5-10W of the t-amp really not enough?

I'll have some measurements up and running shortly, so that I know exactly what spl levels are being generated. Nothing on that front yet though.

I was just wondering what experience other people have had, since this is a fairly popular driver.

[TheSeekerr]

What frequency are you trying to drive the woofer at? Are you driving it full range, or low passed?

Have you read http://www.quarter-wave.com/OBs/OB_Design.pdf ? It explains (on pages 6, 7 and 8) how to take advantage of the high Q of the Eminence woofer with a second order lowpass in order to produce flat-ish response from 45-200 Hz. It indicates that levels of 90dB at 1W/1m should be achievable.

While his conclusions should apply to your project directly, since he uses the same woofer, the response can be adjusted for similar woofers by adjusting the size of the baffle and the cutoff frequency of the low pass filter.

Oh, and a spot of quick simulation suggests that open baffle, the Eminence will reach maximum excursion at around 10W.

[twest820]

Something's amiss. I was running a few hundred milliwatts into my nude 90dB efficient 6.5" drivers and getting comfortable levels for listening at a couple meters. Bass extension below 80Hz or so, no, but even nude 15s are IIRC 30+dB more efficient in that regard.

[ra7]

I thought something was amiss too. I'm cutting off the woofers at 150 Hz using a single pole low pass filter. I will check out Martin's design. I have looked at his website and articles several times, guess its time to dig deeper. Thanks guys, I'll report my findings.

[ra7]

I was using the crossover incorrectly... there is enough output now.

A new problem has propped up though. One of the eminence woofers is hardly moving. In fact, its cone is as stiff as a brick. Even when pressed by hand it does not move. It produces less output than the other woofer and is still while the other one moves during music. I noticed that if I press it hard enough by hand, there is a click back and click front... Does this mean it has to be broken in still? Is there something wrong? The cone is really really stiff...

I did buy these used tho... hmmm.