NHT "orphans" need X-overs and loving homes

[NEO Dan]

Jack Hidley is clearing out perfectly good NHT MT monitors - the x-overs

https://web.archive.org/web/20071008070214/http://home.comcast.net/~jhidley/

So I come to the mountain to ask if the Artisans of the Guide ;x( could have a look at the NHT offerings to see if they would be worth doing passive crossovers for. And of course to give you all a heads up on what looks to be a smoking deal, potentially :B

[dawg1161]

I also seen the ones in the middle that have the optional stands........if they only had a crossover i would've purchased these so come on guru's its magic time....

[Amphiprion]

There are some great deals there. Bummer though for Seas and Peerless; I wonder how much of their business NHT was.

[Dennis H]

Somebody at AVS bought some drivers from him. He emailed and Jack scrounged up some factory crossovers for him. Short of that, I'll bet he'd email you a schematic if you asked nicely.

[NEO Dan]

That would be Erich H, he also built an array sub of NHT drivers.

FYI Jack has provided some passive xover designs already. I was just looking for the Guru x-over mojo

IDEA:
for $100 the xds looks like it would make an excelent TM module for a modular three-way design.

[cobblepots]

I'm going to help my buddy with the Xds and I have a few questions about the cross overs.

I questions about the following:

1. Where can I source the 1.7 mH 0.25 ohm laminate core inductor. I can't find that low of an inductance with that high of a resistance
2. Will using a 6.8 uF capacitor for the 7 uF in the crossover or would 7.5 be appropriate.
3. Can a 0.3 mH air inductor be used in place of a 0.33 mH in the design?

I'm pretty sure I'll be OK on these...

I plan on using Dayton Metallic Poly's and resistors with some air cores from Madisound.

Are these assumptions valid?

[Undefinition]

Hey, if anyone wants to send any of those NHT 2-ways to me, I'll be glad to design a crossover, for free, then ship them back to you. I have faith I could make them sound very good; but I honestly don't have the room for them once they're finished.

[Dean100]

Hey, if anyone wants to send any of those NHT 2-ways to me, I'll be glad to design a crossover, for free, then ship them back to you. I have faith I could make them sound very good; but I honestly don't have the room for them once they're finished.

Paul,

I am going to send you a PM. I am considering picking up a pair of these, not sure which ones yet.

[---k---]

I'm going to help my buddy with the Xds and I have a few questions about the cross overs.

I questions about the following:

1. Where can I source the 1.7 mH 0.25 ohm laminate core inductor. I can't find that low of an inductance with that high of a resistance
2. Will using a 6.8 uF capacitor for the 7 uF in the crossover or would 7.5 be appropriate.
3. Can a 0.3 mH air inductor be used in place of a 0.33 mH in the design?

I'm pretty sure I'll be OK on these...

I plan on using Dayton Metallic Poly's and resistors with some air cores from Madisound.

Are these assumptions valid?

It depends on how picky you are. I've seen Thomas frown upon very minor changes in materials for the NeoCC design, while I've heard other often repeat that values within 5% are close enough. Considering that most of the parts we use a +- 5%, we may have this without knowing it (of course if you use a part with a value 5% less, you could either end up perfect or 10% off). Using values within 5-10% will likely be subtle differences.

You're probably not going to be able to find one exact matches. I've read that Madisound will make custom inductors for not much extra. You might want to call them.

For the cap, 6.8 is within 3%, so probably close enough. You could always build a 7uf cap using a 3uf and a 4uf cap.

It might be worth it to take Paul up on his offer.

[Bear]

I thought the original Xds were all active XOs. Did Jack or somebody produce a design for these or is this the original schematic with only the part between the sub and the monitor being active? (Or am I missing something obvious here?)

EDIT: Got it. The XO posted above was in the "measurements" ZIP file. The FR posted in the zip package for the "with crossover" seems to show that it needs some BSC, at a minimum. I'd be curious as well what folks could do with it.

[cobblepots]

I thought the original Xds were all active XOs. Did Jack or somebody produce a design for these or is this the original schematic with only the part between the sub and the monitor being active? (Or am I missing something obvious here?)

EDIT: Got it. The XO posted above was in the "measurements" ZIP file. The FR posted in the zip package for the "with crossover" seems to show that it needs some BSC, at a minimum. I'd be curious as well what folks could do with it.

As you know, building cross overs and designing them are completely different procedures... I do not have any knowledge for determining if that cross over is designed properly. If I build that as is, will I get a good sounding speaker. Keep in mind my viewpoint of good sounding are my Statements which are the best I've heard thus far. I realize it's an apples to oranges comparison but what sort of quality would I expect from these as is? (Bass output aside)

[benchtester]

I thought the original Xds were all active XOs. Did Jack or somebody produce a design for these or is this the original schematic with only the part between the sub and the monitor being active? (Or am I missing something obvious here?)

EDIT: Got it. The XO posted above was in the "measurements" ZIP file. The FR posted in the zip package for the "with crossover" seems to show that it needs some BSC, at a minimum. I'd be curious as well what folks could do with it.

Thanks for pointing it out the location of the files. The FR shows a step, this might be an artifact of the MLS gate setting(?).

Alternately, the crossover transfer function show a steady decline from 200 hz. to 1 khz. This appears to me, that the inductor and cap on the woofer achieve a traditional BSC. I like the look of the front baffle, but I wonder if its Baffle Step is shifted up in frequency (compared to a flat baffle) and this is reflected in the step in the FR.

[Erich H]

Hey, if anyone wants to send any of those NHT 2-ways to me, I'll be glad to design a crossover, for free, then ship them back to you. I have faith I could make them sound very good; but I honestly don't have the room for them once they're finished.

Paul, if no one else sends you a pair, let me know, I could ship them up to you. I haven't purchased any yet, so I could order 2 and then just have them sent to your address first.

Let me know. :T

[NEO Dan]

I wonder if the H1212 is a drop in replacement in the M-60 and M-20, not exactly a cost effective proposition though.

[NEO Dan]

Jack Hidley confirmed that the NHT tweet is indeed a standard size faceplate with opposing terminals so the H1212 and many other Seas tweeters are a drop in affair.

[Undefinition]

Paul, if no one else sends you a pair, let me know, I could ship them up to you. I haven't purchased any yet, so I could order 2 and then just have them sent to your address first.

Let me know. :T

I did have one offer, but the choice of speaker was still up for grabs. Did you have one in mind you wanted?

[Dean100]

I did have one offer, but the choice of speaker was still up for grabs. Did you have one in mind you wanted?

Paul,

I sent you one more PM.

[---k---]

Jack Hidley confirmed that the NHT tweet is indeed a standard size faceplate with opposing terminals so the H1212 and many other Seas tweeters are a drop in affair.

When I hear people talk about drop in replacements, I interpret that to means no crossover changes required in addition to the box. Just for clarification, changing the tweeter will very likely require crossover changes for optimum performance.

[Undefinition]

Jack Hidley confirmed that the NHT tweet is indeed a standard size faceplate with opposing terminals so the H1212 and many other Seas tweeters are a drop in affair.

For what it's worth, I don't really know why you'd want to "drop in" an H1212. The Seas tweeter that comes with those NHT is likely quite nice. From a glance, they appear to be 25TAF; which--as far as I know--is no slouch of a tweeter.

[NEO Dan]

I was refering to form factor, as I fear the NHT tweet may rely on the 300dB slopes of DSP, where as the H1212 is perfectly content on a passive network.

[cobblepots]

I was kinda hoping for a reply to my last question from someone who knows more than me... Will the Xds speaker, as design with the crossover be "good enough" or will my friend not be happy with them? I don't want to have him invest into some speakers that are inadequete SQ wise. Sending the speakers out isn't really an option as he's looking for a set now instead of waiting. He wouldn't listen to me :W Thanks!

[benchtester]

I was kinda hoping for a reply to my last question from someone who knows more than me... Will the Xds speaker, as design with the crossover be "good enough" or will my friend not be happy with them? I don't want to have him invest into some speakers that are inadequete SQ wise. Sending the speakers out isn't really an option as he's looking for a set now instead of waiting. He wouldn't listen to me :W Thanks!

I have not worked with these particular drivers, but it looks like a great deal to me. I have been working on similar size speakers with low order slopes and tweeter waveguides. Given these drivers and the baffle as shown, I think they will be best with LR4 acoustic and some tweeking to insure good phase alignment.

If he is in a big rush, the crossover above is probably "good enough". I am concerned that there will be slight smearing between the tweeter and the woofer (an 8-10 degree slant might help) and there might be the cone break up node may be audible.

[MuaDibb]

In box measurements have been provided on the site. One could put these into PCD or other software and sim the suggested crossover or come up with a completely new one.......couldn't they?

[dwk]

In box measurements have been provided on the site. One could put these into PCD or other software and sim the suggested crossover or come up with a completely new one.......couldn't they?

I haven't looked at the measurement package, but that is certainly the idea behind providing them.

Geez. $280 plus shipping for a pair of the Xd and stands. If I weren't already overloaded with projects.......

[Johnloudb]

I'd think the crossover design provided for the XDS satellite would be a good one, wouldn't it? I guess one could only assume that it was designed by NHT. Would that be a bad assumption?

I may just get a pair.

[Jack Hidley]

There's a lot of stuff to address here. A little background first. I'm the person who was responsible for the design of all three NHT products that are discussed in this thread, the M-20, M-60 and XdS speakers. The M-60 and XdS speakers were only ever used with digital active filters. The M-20 was only ever used with a passive filter. Another exNHT employee and I designed these crossovers to help out people that were purchasing the systems. They are not designed to be the end-all-be-all crossover designs. They have been tested, won't blow up the drivers and have good measured polar response.

Regarding the crossover components:

For capacitors just parallel them to get the correct value. The same goes for resistors.

For the 1.75mH 0.25 ohm inductor, just use a Madisound Sledgehammer 2.0 mH 0.15 ohm inductor and unwind it down to a 1.75mH value. If you don't have an LCR meter, I'm sure Madisound will do it for a few bucks. If you have a function generator and an amplifier, you can also determine the inductance by forming a simple RC filter with a known resistance and measuring the electrical frequency response of the filter. Keep unwinding the inductor until the -3dB point of the filter is correct for the desired inductance. When you are done, just add a 0.1 ohm series resistor to get the DCR correct.

You could also spend $25 on a Solen air core inductor and unwind it, but I think that is a total waste of money.

If you have an aircore inductor that isn't quite the correct value, you can also just calaculate what its value is supposed to be and use the info to interpolate how many turns to remove. If you do use air cores, make absolutely sure to mount them at 90 degrees to any other inductor and don't put them near any steel or their value will be different.

I would stay away from any ferrite or powdered iron core inductors. In my experience they are all very high distortion.

The measurements in the data package are complete enough for anyone to use to design a crossover. I can't understand why someone would ship the speakers to someone for measurements.

Regarding BSC:

The XdS passive crossover already has BSC designed in, in the professional manner. The DCR of the L in the LC network is used against the iductance of the driver to get a 1/2 order slope from Fcb up to the corner frequency of the crossover. As someone already pointed out there is over 6dB of BSC already in the crossover. The woofer naturally has a slightly shelved up area around 1kHz. This isn't easy to remove with a passive crossover without using a lot of parts. Look at the nearfield measurement of the XdS woofer. There is a little bit of HP shelving going on in the measurements due to the short MLS window, but not much.

Regarding the M-20 tweeter interchange:

<extreme sarcasm mode on>
Of course you can drop in any tweeter you want, the more expensive the better. In fact if you spend more than $200 on each driver, it is guaranteed to sound 10x better even if you leave off the crossover!
<extreme sarcasm mode off>

Unfortunately, NHT is out of the Seas tweeters that fits into the M-20 cabinet. They do have plenty of the same driver in 98mm faceplate with an NHT logo. However, this looks pretty awful in the 104mm recess and the screw holes are on a slightly smaller diameter making it very hard to install the screws without having the heads at a 30 degree angle.

I'll probably update the website later to indicate this and adjust the price. I think it is still a very good deal for a finished cabinet with a very nice woofer.

None of the tweeters NHT uses rely on a super steep slope. We don't use super low frequency crossovers.

I strongly urge anyone considering these products to look at all of the pdf files in each data package. You can learn a lot about what the driver and cabinets are doing from all of the data supplied.

[NEO Dan]

I'm feeling a bit misunderstood :cry:

I am sort of surprised that when a commercial speaker is offered without the physical crossover, that the first thing on the list is to NOT measure it and look at crossover design.

At first post I hadn't even looked in the data files. All I knew was that the speakers need a crossover.

The H1212 we can chalk up to a matter of personal interest based on my view of it's reputation.

[NEO Dan]

Hi Jack,
you posted whilst I was composing my post.

[cobblepots]

Jack, thank you very much for the information you've provided. One more question for you, I can't locate the Sledgehammer inductor on the madisound website, any other alternatives you would suggest? Thanks

[ThomasW]

http://www.madisound.com/catalog/product_info.php?manufacturers_id=139&products_id=861

[Undefinition]

Jack,
I am sorry if I insulted you in any way. I don't mean to step on any toes, and I appreciate what you do for the community.

Your measurements looked very good to me. I was only going to re-measure the drivers, becuase I design from a listening axis, and I use the "time of flight" information in the acoustic phase to design my crossovers. (In other words, I measure both drivers from the same position)

Your crossovers are probably good--especially since you said you worked with an NHT employee to do them. My assumption (and I may have been wrong on this) was that you had measured the drivers, then simmed the XO in a design package but never actually listened to it. Not that there's anything wrong with that; I've done it for several members of the community... but I much prefer to actually listen to my modeled designs and voice them in-person. That's basically what I was offering in terms of the NHT 2-ways. But if you've already done that step then it seems sort of redundant for me to do it, too.

I'm not here to 1-up you. Like I said, I appreciate what you've been doing for the community. So I hope I didn't offend.

[Bear]

By the way, Jack has also put up the XdW and S-80 subwoofers for sale. I have dibs on a pair of S-80s (e-mail/deposit has been sent).

[Jack Hidley]

Paul,

No offense taken. I was just confused by your offer given what I had supplied in terms of measurements and such.

Your assumptions about the measurements are correct. The cabinet had both drivers in it. The mic was located at 1M on tweeter axis. MLS based measurements were done on both drivers with an AP 2700, so the phase data is accurate. The mic was never moved so there is no need to enter any correction data into your sim package.

Gordon cranked through some part values until he got a flat response and had the main lobe pointing straight ahead. Given that we had already designed the active filters for this system, we basically knew exactly what the crossover transfer function should look like. Gordon soldered the parts together, we took a couple measurements to make sure the simulation was correct and then we listened to it with music for oh, maybe 90 seconds and went "Yup its a speaker!". Like I said above, I'm sure the crossover isn't perfect, but I think 95% of the people would be perfectly happy for $100

[benchtester]

... but I think 95% of the people would be perfectly happy for $100

:T

I think they should be more than happy. Madisound's current price for the woofer alone is $162.40! :B

[cobblepots]

http://www.madisound.com/catalog/pro...roducts_id=861

Thanks Thomas, those were the ones I found but they weren't named "sledgehammer" so I was just checking. Given the price of these drivers, my buddy will definitely be picking a set up! Thanks for all the help everyone.

[benchtester]

Thanks Thomas, those were the ones I found but they weren't named "sledgehammer" so I was just checking. Given the price of these drivers, my buddy will definitely be picking a set up! Thanks for all the help everyone.

A small hint: don't steel screws to mount this inductor, they can increase the inductance.

[cobblepots]

A small hint: don't steel screws to mount this inductor, they can increase the inductance.

Thanks, I used hot glue and zip ties on my statements so I'll probably repeat that procedure but now I'll make sure to remember that for future reference.

[Jack Hidley]

Madisound called them Sledgehammers on this page:

http://www.madisound.com/about/inductors.php

Although, now that I look now, this seems to be the only place they call them this!

[JoshJK]

My first post here. I am very interested in these deals. Jack, if you can answer, is the internal construction of these midwoofers used in M-60 and XdS really the same as that of the corresponding Seas Excel models? For example, most importantly, are their motors identical, including copper Faraday rings below and above the pole piece?

BTW, FYI Meniscus audio sells the same quality iron core coils and unwinds them to any custom value with no extra charge.

[Bear]

My first post here. I am very interested in these deals. Jack, if you can answer, is the internal construction of these midwoofers used in M-60 and XdS really the same as that of the corresponding Seas Excel models? For example, most importantly, are their motors identical, including copper Faraday rings below and above the pole piece?

BTW, FYI Meniscus audio sells the same quality iron core coils and unwinds them to any custom value with no extra charge.

He's basically answered this question on the site about the M60. It uses a W18E with a dust cap, rather than the phase plug. The XdS looks like it uses the W15CY, but with a different phase plug. I'd be curious why the substitution in the case of the XdS, if this is the case. If it is just a dust cap, then I expect the same reasons apply (better seal, better low-end extension).

Bill

[Jack Hidley]

XdS/W15CY:

We added a shielding can with bucking magnet.
The phase plug is made from aluminum instead of copper. We thought the black anodized aluminum looks much better and it's much cheaper than the copper. Barely any difference in flux modulation or inductance symmetry. Other than those two changes, it is identical to the stock Excel driver.

M-60/W18E:

We added a shielding can with a bucking magnet.
We lost the phase plug and added the aluminum dust cap. I'm 90% sure there is still a shortened phase plug/shorting ring on top of the pole piece. This was a couple years ago and I can't remember. Other than those two changes, it is identical to the stock Excel driver. Go here for some photos of the driver:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MESELX:IT&item=270354538002

The Excel woofers don't have shorting rings per se above the gap. The phase plug is the shorting ring above the gap.

Having the phase plug allows the coil to cool better. When the woofer moves under large excursions, the air is forced through the magnetic gap and cools the coil. In the XdS with the low sensitivity of the woofer due to the small cone area, the high power of the amplifier (150RMS over 300W short term) and the small coil diameter, we needed this cooling. The downside is that as the woofer ungoes large excursions its rest position moves. This is because the airflow through the magnetic gap is not symmetric. It moves more easily one way than the other. Essentially this air leak rectifies the low frequency output from the speaker and causes the coil to move off center, increasing distortion. The smaller the box you put this driver in, the worse the problem. We put it in a very small box.

A couple years ago, we took some W16 Excel drivers and put them in an XdS cabinet. With the increased cone area and increased excursion available, this thing could play really loud! However, the air noise was awful.

On the M-60 we had the same amplifier power available, but a larger voice coil. We also expected the speaker to be used without a subwoofer. The air noises and voice coil offset from using the phase plug version would be unacceptable in this application. So we put a dust cap on it. The driver is really quiet now.

Seas figures that most users will put these drivers in much larger vented enclosures where the internal pressure is much lower. This makes the air noises inaudible.