what amp for NHT1259 woofer?

[Bill Fitzpatrick]

Well, I see several areas worthy of investigation.

1. You don't really have a closed box. You have a closed end line with insufficient stuffing. That's going to cause response irregularities in the frequency range where "wooly" might be applicable. And, with the back just screwed on, it looks like it might be very leaky.

2. You are crossing to close to the natural roll-off of the ribbon. That's destroying the LR slopes you thought you had.

3. I'd want to look at the effect of summing the LP outputs of the crossover as you are doing. Marchand does say 10K minimum load but I'd bet a boatload of bananas the curve isn't ideal.

4. The box size you are using is to small. That woofer calls for a larger box for a more reasonable Q.

I'd start with a 160L box and if you need those dimension ratios, I'd mount the woofer in the center.

[dan _s]

the box is "supposed" to be sealed. in the drawing is how the back is attached to the side. i added an extra frame around the rear side in the inside of the side walls after i took the above photo.
the roll off of the ribbons and woofer box volume are within the recommended, and the responses of the XO are nice LR slopes

but then again, if it does not sound good, all those things are worth rechecking

other things to be concidered are leakage from around the driver, the LP frequency. a bad driver unit?

[dan _s]

i got different suggestions for several people (who were kind enough to help) so i asked Bill Bush, who designed the driver. he suggested this:
lower box volume to 70-80 liters
lower XO closer to 100Hz or add another driver
amplification to the woofer should be at least 100w. 200w is recommended. double that if i use two drivers