For Sale: NHT Loudspeaker drivers and amps-Discussion Thread

[valveitude]

Hi Jack,

First, I forgot to thank you for offering your "table scraps" to us hacks before tossing them in the bin . Thanx also for posting the prints so quickly. As soon as my replacement credit card arrives (about a week) I will be ordering some of those 250W modules to play with.

I don't suppose you know the rail voltages? Trying to do a little prelim reverse engineering. I'm assuming something on the order of +/- 80V ?

FYI for others considering this amp:

These amps appear to be pretty long in the tooth, as such, almost all of the semi's are obsolete numbers. The good news however, is that http://www.electronix.com still carries everything except the BF422/423 semis in the protection circuit (the only ones that aren't obsolete), and the output pairs 2SA1302/2SC3281 have a direct replacement in the 2SA1943/2SC5200.

Casey

[DAVE CC]

Hi guys,

The NPT-11-075-2 and the VT-3 amp is exactly what I am looking for to build my first twin box sub system, but I have no idea how to build a EQ by using a rectifier in a filter cap, can anyone help me here ?

My inner volume of each of the box is about 1.68 cubic ft, should I make these a sealed or vented system ?

Thanks.

Dave Chang

[Jack Hidley]

Mr. Chang

With 1.68 cu ft per driver, you definitely need to keep the enclosure sealed.

You need to build a 2nd order HP filter (12dB/octave) with a corner frequency of 23Hz and a Q of 2.3. This filter can be placed inside the VT3 amplifier or in some other signal processor upstream.

The 075 driver in a 42l enclosure, with the filter from above will give you a -3dB frequency of 23Hz.

[DAVE CC]

Hi, Jack

Thank you for your fast responce and info, all sounded great what you sugested, eventhgough i have no idea how to build that filter. I figure some body out there may have something already buit, or will build it for me.

Please also let me know, how can order a pair of the drivers and the VT-3 from you, is it easier for you if i send you a check ?
If you can point me to the direction as how to build this filter,( such as components that I need, and where to get them, or if you can build this filter into the VT-3 and charge me for it.)

I am glad that SY recommented me to this forum and look into your drivers and amps. Thanks SY.

Can't wait to bild these subs...

Dave Chang

PS. If anyone can share any info how to build the filter Jack mentioned, It would be greatly appreciated, maybe I can return the favor by building a custom box in exchange, I work in a high end cabinet mfg, and have unlited free cut-off MDF and other materials.

Thanks guys.

[BWRX]

Originally posted by DAVE CC
Please also let me know, how can order a pair of the drivers and the VT-3 from you, is it easier for you if i send you a check ?

Hi Dave. Scroll to the bottom of Jack's sale page: http://home.comcast.net/~jhidley/ for terms and ordering information.

[Jack Hidley]

I updated the quantites of parts available.

[al2002]

Originally posted by Jack Hidley
I updated the quantites of parts available.

Thanks Jack.

What is the 11-080? I don't see it on your home page, only in the XLS file.

[Jack Hidley]

The 080 was used in the VT3, VR3 and VC3 as a midrange. The 081 was used in the VS2.4 and VT2.4 as a woofer/midrange. I'm 99% sure that they are the exact same driver. We probably gave the 080 a different part number, because we QCed it to a tighter standard. I'm trying to confirm the difference now, but this is from two owners ago.

[al2002]

Originally posted by Jack Hidley
The 080 was used in the VT3, VR3 and VC3 as a midrange. The 081 was used in the VS2.4 and VT2.4 as a woofer/midrange. I'm 99% sure that they are the exact same driver. We probably gave the 080 a different part number, because we QCed it to a tighter standard. I'm trying to confirm the difference now, but this is from two owners ago.

Thanks. Please let us know what you find.

[Jack Hidley]

The 081 has a voice coil that is 14.9mm long. The 080 has a voice coil that is 12.7mm long. Except for that, the drivers appear identical. I'll try to post some specs for the 080 driver on Monday.