Can I Upgrade My NHT Sub Drivers? and Newbie Advice (1 Viewer)

[Richard Burzynski]

Background: I have a few (4) NHT SW3S subs. These subs are sealed design, 19"x19"x19", containing single NHT1259 driver. I plan on using them as stereo pairs in front corners of the room. My room measures 3000 cubic feet.



All my speakers are NHT, and I like the NHT gloss black look, but from what I have read these subs are flat to only 30hz. So I was thinking about upgrading the drivers, I would like to get flat response to 20hz (or as close as possible).



From what I have read on this forum, I realize that [size and type of enclosure + particular driver brand/size + power of sub amp] will yield different performance results, but I want to recycle these sub cabinets, as they are in great shape and I have basically zero building "skills".



The sub amp is 4 channels of a Citation 5.1 amp.





Questions:

* How hard would it be for me to swap out drivers myself?

* Is there a 12" driver that would work in this particular sealed 19"^3 cabinet to give me response close to 20hz?

* Is my amp sufficient (I think I read that sealed designs require high-powered amps)?

* I read a review that said my particular sub is a 3ft^3 box. How? On my HP calc, 19"^3 = 3.97'^3

* Would it be cheaper for me to just sell the NHT subs (as is) and get "new" ones?



Thanks for reading.



Rich B.

 

[JonWB]

Actually 19"^3 equals 0.011'^3. If you are measuring 19" per side on the inside of the cabinet you would be at 19*19*19=6859cu.in. which would be 3.97cu.ft. If you are measuring the outside of you cabinet at 19" per side then you probably are looking at a ~3cu.ft. cabinet. Remember the space the back end of the speaker takes up should also be accounted for.

Thats about all the help I'm worth.:b

 

[Dave Poehlman]

* Would it be cheaper for me to just sell the NHT subs (as is) and get "new" ones?

THat depends what you can get for them . Really, from what I can tell you have some nice subs there. It would be difficult to replace the drivers and achieve the same quality. (provided the Madisound specs are correct).

 

[Brian Bunge]

Richard,
Your enclosure is 19" cubed externally, but internally (assuming 3/4" material) it's 17.5" cubed. That's about 3.1ft^3 of internal volume.
If I were you, I'd buy 4 of the Dayton DVC 12" drivers from Parts Express. In a 3ft^3 enclosure with 2-3 lbs. of polyfill you'd have a quite musical Qtc of .59! You'd have much better power handling and excursion as well.
Also, you'll want to wire the voice coils in parallel so make sure your current amps can handle a 4 ohm load. IIRC, the 1259's are rated as 4 ohm drivers so this shouldn't be a problem.
Brian

 

[jeff lam]

Isn't the Rava an 18" cube externaly? I would think a shiva would work wonders in those cabinets. So would the 12" DVC which requires even less space in a sealed enclosure. Either one of those drivers should provide excellent results. One thing to consider is that the new drivers may not be exactly the same size cutout diameter as the NHT's so research/measure that first. If the hole is too small you can enlarge it but if it's too big, there's not much you can do.

 

[Brent_S]

With room gain, the SW3s should be good down to 20 hz in room. The predicted f3 anechoic of the 1259 is/was about 30-32 hz back when the driver was originally made available to the DIY community and at the same time the SW3 was a retail product.

Richard, are you dissatisfied with the NHTs or just thinking the grass is greener based on all of the rave reviews of the Shiva/DVC 12/ etc? I find myself falling into that camp from time to time. A few test tones and an SPL meter should allow you to quickly confirm the in room response of your subs. Unless your bottoming your subs, the increased power handling and Xmax of the newer drivers won't be gaining you anything since you're not using all of your current potential. Likewise, unless your experiencing some weird room acoustics, you should be within a few hz of any of the potential drop in replacements on the bottom end.

If you need more output and to prevent any destructive interference, you might want to try stacking all four of those subs into the same corner, if possible. SVS-Ron told a story on the speaker forum the other day about placing a sub in two corners of the room and actually creating complete silence at the listening position even though the subs were going full bore.

I can't find it with the search engine now, but about a year ago, there was a thread on here where we posted our various subs and their SPL output at specified frequencies. With a pair of sealed ~3ft^3 1259s powered by a NAD 2400THX, I hit 101db@20hz, 107@25, [email protected] and 110@40 measured 11ft away in a 21x14x8 living room with several large spaces leading off of it. I don't think that was their absolute limit before bottoming, that's just where I gave up on risking damaging them or the room. In actual use, I've never really found them lacking, but I don't try to listen at the levels that some on the board do.

Do some empirical testing to see if you'd really gain anything from spending $400+ to do a drop in driver replacement with the likes of Shiva/DVC12/Stryke/etc.

Whew, sorry, that was supposed to be a quick reply.

wbs

 

[Richard Burzynski]

Thanks for the replies!
Jon:
I didn't think about the space for the backend of the speaker.
Dave:
"and an amazingly low Fs=16.5 Hz."
I don't know what an Fs (maybe tuning frequency?) is, but I like the fact that you you call the NHT1259 amazing.
"So, a maximally flat sealed enclosure will not be as loud as a maximally flat ported enclosure as the lower frequencies rolloff."
Loud is what I'm after.
"Are the measurements you gave external?"
Yes they are external.
"Really, from what I can tell you have some nice subs there. It would be difficult to replace the drivers and achieve the same quality."
Thanks for the compliment - one vote for leaving the NHT drivers alone.
Brian:
"If I were you, I'd buy 4 of the Dayton DVC 12" drivers from Parts Express. In a 3ft^3 enclosure with 2-3 lbs. of polyfill you'd have a quite musical Qtc of .59! You'd have much better power handling and excursion as well."
One vote for swapping the drivers.
* QTC?
* Better power handling. Meaning that the Daytons are more sensitive?
* Eexcursion. Meaning they'll "move more air"?
Jeff:
"So would the 12" DVC which requires even less space in a sealed enclosure. Either one of those drivers should provide excellent results. One thing to consider is that the new drivers may not be exactly the same size cutout diameter as the NHT's so research/measure that first."
Another vote for swapping and for the Dayton. Driver size maybe different, that stinks. I assumed all 12" drivers measured 12".
Brent:
"With room gain, the SW3s should be good down to 20 hz in room."
That's good, but minus how many db, or do you mean flat?
"The predicted f3 anechoic of the 1259 is/was about 30-32 hz back . . ."
f3?
"Richard, are you dissatisfied with the NHTs or just thinking the grass is greener based on all of the rave reviews of the Shiva/DVC 12/ etc?"
The HT isn't even set up yet, room still under construction, but gear has been collected. I'm very familiar with how this NHT sub sounds and have always liked its sound, but from the constant comments on this board of how these new drivers are better than sliced bread, I figured I was missing out.
"Unless your bottoming your subs, the increased power handling and Xmax of the newer drivers won't be gaining you anything since you're not using all of your current potential."
Please explain as I don't understand this comment. Do you mean the newer drivers would require more amp than I'm planning on using?
"With a pair of sealed ~3ft^3 1259s powered by a NAD 2400THX, I hit 101db@20hz,"
That makes me feel good! Were they stacked?
Sorry for all the basic questions, I'm sure you guy are sick of answering them. Interesting, 2 of you say do the swap, the other two say my NHT1259 drivers are nothing to sneeze at. I'm feeling a little better and maybe the grass ain't THAT green?
Any more thoughts?
Rich B.

 

[Rudy H]

The 12inch Dayton DVC would probably work very well, but if you want something with a bit more excursion, go for the 12inch Titanic MK2. It has almost 38mm of linear excursion
They'd have a Q of around 0.68, without stuffing, which would help out super-low end bass a fair bit.

 

[Brent_S]

"That's good, but minus how many db, or do you mean flat? "

The 1259 models to be -10 db @ 18hz. The numbers I usually see thrown about predict +8 to +10 db of room gain at 20 hz so theoretically, the 1259 would be around -3db @ 20 hz. This is how I believe the SW3 was originally spec'd. Flat and -3db down are usually synonomous for specification purposes even though obviously not 100% technically correct.

f3 = the -3db point relative to some 0db reference point.

Fs is the resonant frequency of the driver. It's a good indication of the low end potential of the driver as it's really hard to get any output out of a driver below resonance. I don't know the complete techno-babble to explain it, but that's the general concept. FWIW, the 1259 was originally spec'd as having an Fs of 19hz. Either way, it's slightly lower than the Fs of the DVC12 or Titanic2.

I'll let someone else try to explain Qtc, but suffice is to say that the .7 Qtc of the 1259 shouldn't ever be confused with one note bass.

""Unless your bottoming your subs, the increased power handling and Xmax of the newer drivers won't be gaining you anything since you're not using all of your current potential."

--Please explain as I don't understand this comment. Do you mean the newer drivers would require more amp than I'm planning on using? "

The potential replacement drivers have larger Xmax (cone movement) as well as more power handling so will play louder than the 1259 assuming they have the same efficiency and if you have more power to feed them than the 1259 can handle. But, what I wast trying to say is this increased SPL capability from a driver replacement is a moot point if you're not hitting the limits with your present SW3s. Your interpretation is probably valid, but without knowing the ratings of your Citation amp, I can't say for sure...keep reading.

Ok, just for fun I just ran a simulation of the 1259, PE DVC12, and PE Titanic Mk 2 in WinISD using a 3ft^3 sealed box with 150 watt input measured at 2 meters. The 1259 is actually even with the DVC12 @ 20hz and +1db @ 30hz. From 80hz up, the DVC12 takes a 1db lead, but we're out of sub territory by then. That same 150 watts into the T2 is 3db behind the 1259 @ 20hz, 30hz, actually across the board. According to the specs I have for the 1259 from several years ago, which should match your SW3s, it's only rated for 150 watts RMS. The newer drivers under consideration have 300-600 watt ratings. Doubling the power in gets you +3 db out. So, to refine my point above, your Citation would have to be able to put out 300 watts continuous for you to get a 3db advantage over the 1259 @ 20hz assuming the 1259 bottoms with more than 150watts. I doubt your Citation can deliver 300 watts continously into 4 ohms, possibly not even the 150 watts of my simulation so for the DVC12 to show any significant advantage over the 1259s, you'll also need to upgrade your amp to get the extra power. Obviously, the T2 is even worse.

Now, if you want to go and build a ported box for the DVC12, it's a whole different ball game. That same 150 watts @ 2 meters gets you +3db @ 20hz and about +4db @ 30hz relative to the 1259. But, by being ported, the response below the port tuning frequeny rolls off in a hurry. My test cd has a 12hz tone on it. The 1259 still has enough output at 12hz to make doors vibrate in my room, but looking at my simulation, I would *guess* the DVC12 probably wouldn't.

Capsule - According to the simulation you'll probably either need a bigger amp to notice an improvement by replacing the 1259s with DVC12s or you'll need to build ported boxes for the DVC12s to get an advantage over the 1259s with the existing amp. WinISD isn't the end-all be-all of simulators, but it should be accurate enough to trust that if your goal is to use the SW3 cabinets and Citation amp then the driver replacement isn't an upgrade.

"Were they stacked?"

Essentially, side by side in the most solid corner of the room.

"Sorry for all the basic questions, I'm sure you guy are sick of answering them."

As they say, the only bad questions is the one not asked.

Now, I think it's bed time...

wbs

 

[Peter Jessee]

If you decide to do a driver swap, the Adire Rava and Parts Express 12" Titanic MkII would be the best choices for the cabinet size you have. I've read several posts from experimentors saying the 12" DVC works best in cabinets no larger than 1.6 cu.ft.

"With room gain, the SW3s should be good down to 20 hz in room."

That's good, but minus how many db, or do you mean flat?

That would be flat, i.e. +/- 0 dBA. Room walls typically reinforce bass frequencies, compensating somewhat for the rolloff in response as frequencies drop. This effect varies with room size, wall construction and other variables. A sealed box has a more gradual rolloff than a vented box, and the room gain effect can prop up the rolloff to give a flat in-room bass response down to impressivly low frequencies.

Some definitions for terms you questioned:

Fs = Free Air resonance frequency, basically the frequency that the bass begins to roll off when the driver is mounted on an infinite baffle. This value is used in calculating enclosure size.

F3 = Frequency at which the bass response has dropped 3 dBA below the average output level of the driver.

What is the power rating for the Citation amp you have? It could well be that buying a high-Xmax, super-power-handling driver won't lead to more output if the 1259's you have can already handle the full output of the amp.

I own a Shiva, a 12" DVC and a 15" DVC (still in the box for now), so I certainly appreciate the new-style drivers. But there is something to said for the classics. If I were you, I would experiment with what you have. Four 12" subwoofers, carefully placed in your room, should be able to pump out impressive amounts of bass.

Peter

 

[Robert_Gaither]

If I remember correctly the Citation 5.1 is the same amp as my friends Legacy 4/3/2 (140 wpc/8 ohms + 225 wpc/4 ohms and can be bridged to 450 watts so it should have plenty of power). Also if I remember correctly the Nht 1259 was also a 6 ohm driver so replacing with a lot of the current drivers means that most likely your amp will see less impedence (lot of these drivers are 4 ohm or the DVC will be driven into a 4 ohm load by wiring in parallel).

What might be a good cheap experiment is to pick up some of the older SVS woofers from people doing upgrades since some claim it might be identical to the Blueprintdrivers 1201 which has the same size diameter cutout but might have a different mounting hole pattern. This way you will be out a lot less money for the initial experiment and if this shows improvement then you might want to take the plunge to a more exotic and expensive driver.

Of course you might can buy some of the more exotic high excursion drivers (BPD 1203) and eq them for your response instead or add a passive radiator to your cabinets as other alternatives.

 

[Jack Gilvey]

I don't think I'd bother with a driver change in those sealed cabs solely to get better extension. Getting much lower than the 1259 sealed would require some eq with any driver.

If you wanted to try something new in those cabs, a reflex with PR's would make the most sense. The Dayton 12" DVC would be cool, but an Adire Brahma 12' with two PR-15's would likely be astounding...and expensive.

 

[Alexis]

buy a radio shack spl meter to find out the actual in room response for your subs. This will help you decide if you need to upgrade.

As for drivers, take a look at the Brahma from Adire.

 

[Richard Burzynski]

.

 

[Richard Burzynski]

I really appreciate all the above explanations of the basics (Fs, F3, and such). I intend to keep reading and learning on this board.
Thanks for all the advice guys. Looks like swapping the 1259's for current 12"er's may or may not give me "improvement." Not worth the trouble then.
*NEW* bright idea. I couldn't help but notice the 9-page thread regarding Dan's new uber 15" driver. I read every post - and I think I understood the majority of them.
Here's what I like:
* Designed for home use.
* More XMax than any other driver.
* Optimized for sealed enclosure.
* Optimized for ~3 cubic foot enclosure.
* Very linear response (little or no EQ required).
* Supposed to be a "Velo Killer".
I already have the 3 cubic ft enclosures! Is it naive of me to think that I can just get a local woodworker to enlarge the holes in my NHT cabinets, pop in these new drivers, add $400-500 amps and have mucho fun?
I am thinking 2 to start, maybe all 4.
That sounds like fun to me. . . Yeah.
Rich B.

 

[CarlDais]

It might not appeal to you esthetically however, you might consider compound loaded arangement as Thomas W has done with his Rava-II.

Otherwise leave them alone. Since you are not up to dong a PR design as Mr Gilvey has done.

Many have already made the point but taking 30 minutes or so and measuring your present FR in your room and possbily rearranging the enclosures will yield you some improvements. It will provide you the necessary baseline data form which your quest might logically proceed from.

YOur Citation AMPS are simlilar to the Lexicon Amps and the Leagacy amps. They are capable amps.