what amp for NHT1259 woofer?

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i built a woofer with a single NHT 1259 driver.
it's in a closed box, about 90 liter volume, cross over point at 200Hz and driven currently with one channel of an audiolab 8000a amp, said to have 60watt.
the speaker sounds very "wooly". far from "precise and dry" which is the word about this driver.
i checked sealing, it's good. i suspect amplification is not enough. the recommended power for the NHT 3.3 speaker , which has the same driver, is 30 to 300 watt, but madisound use at least 200w for the same.
any suggestions for the power needed for this woofer?

here goes

the box is as in the drawing attached, meassures are in centimeters, stuffed loosely with synthetic fibers, something called acrylan over here. the wire inside is simple copper 2.5mm section multicore wire.
the back is currently just screwed not glued, for adjustments
the crossover is a low level passive XM46 marchand unit . the two low frequency signal channels in the XO are bridged with two 10K resistors for a mono output.
i just don't have room for two woofers. since bass is weaker the the high signal, i put a 50K potentiometer at the high output for tonal balance.

as for mid and highs, it's two BG RD50 ribbons, set as monopoles, driven by a WAD kat6550 amp.

the source is marantz cd5000 as transport and 'deltec enlightment' DAC connected straight to the XO


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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.
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?


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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.