NHD Xd monitors

[dwk]

I've routinely kicked myself for missing out on the $100 closeout that Jack Hidley was running last year on the Xd monitors, but much to my surprise I discovered recently that NHT is still blowing these out on their site.

http://www.nhthifi.com/Clearance

I picked up a pair of the 'Special Dark' finish units. $250 per speaker is a bit of an increase, but that includes the stand AND free shipping, so it actually comes out nuch closer to a wash (well, aside from the fact that I don't really need the stands....). Very nice units - way beyond anything I could hope to DIY, and the dark finish is IMHO very attractive.

I know there was a bit of discussion on these here, but did anyone actually do anything with them? Even better, did anyone do anything other than just use Zaph or Jack's xover?

I've been interested in DSP active xovers for quite a while - I was experimenting with BruteFIR almost a decade ago - and so am planning to finally try to realize a full 'production quality' system this way. It'll be PC based rather than standalone with the DEQX. Prototype will be with my Saffire Pro 24 (spdif out to a Buffalo Dac for the mids), but if it goes well I'll probably replace that with something a step or two up the ladder - either a Steinberg MR816 or if I'm feeling really rich a Lynx Aurora although that's probably a stretch; the LIO8 is way out of the budget, unfortunately. Volume control via the MSB MVC I have (nice!). My current plan is a pair of RSS210's for the bottom end, crossing at 150-200 to the monitors. Since this is a desktop/nearfield setup I think the RSS210's should be more than enough as long as I have adequate power.

I won't start this in earnest until some time in Jan, but I'm hoping I can get a prototype running fairly quickly since there is a fair amount of info out there - including the measurements from Jack as well as transfer functions of the original DEQX version from one of the reviews. All I need is the time, which of course is always the sticking point.....

[ThomasW]

Jonmarsh has a pair and did some XO design for them. He talked with Jack about the strengths and weaknesses of the drivers. (Jack lives not from from Jon's place)

Jon's been traveling on business for last 60+ days so won't have seen your post. You might want to send him an email about this

[TacoD]

Interesting project!

[BretH]

"Jon's been traveling on business for last 60+ days so won't have seen your post."

Ouch. Safe travels, Jon!

[benchtester]

Edit: Oops, OP already knows of Zaph's crossover; but for others here's the link.

http://www.zaphaudio.com/XDS.html

[dwk]

Picking this back up later than intended - I figured I'd have better net access over the holidays but it didn't quite pan out that way.

Jon's been traveling on business for last 60+ days so won't have seen your post. You might want to send him an email about this

Zoiks. Even on the scale of Jon's past travel schedule that truly sucks. Hopefully things start to relax soon.
I'm not sure this is important enough to bother him with if he's that busy, but I suppose it may offer a bit of distraction.....

Jonmarsh has a pair and did some XO design for them. He talked with Jack about the strengths and weaknesses of the drivers. (Jack lives not from from Jon's place)

This makes perfect sense once I thought about it. One of Jon's C-E topology xovers would be perfect for this - both drivers would be optimized by a steep xover in the 2-2.3k region.

I'm still waffling on whether to even pursue a passive xover at all - originally it seemed a quicker route to getting something working, but since I'd still need to go active to the bass drivers that may not play out in practice. In theory I have everything I need to do an IIR topology active xover on the PC immediately, so that is probably the easiest route to explore. The FIR version can come later.

[JonMarsh]

Not what you might expect

I did a "Modula" style crossover study for this; not built yet, though I think I got the parts in (buried in the mists of 2008?) It does use cauer like traps on the woofer, as the original design with the RS180 did.

Was looking for a fairly low count crossover that would do something similar to the modula MT designs, nice phase transition between drivers, good on voice and classical music.



Not built yet, untested, but developed with my own measurements, not NHT measurements.



The interaction of the baffle hole and Seas driver causes an on axis lift in the presence region.



But the power response tapers off as you move off axis by 20 degrees, so the room power balance should be pretty good; I'd try this first before tuning it further. May have an application now to build this for...

Total predicted impedance curve is not especially flat, but is benign; easy to drive.



This is NOT tested, just a WIP.