Can't find a subsonic subwoofer Driver!

[gregz]

Hello, I just woke up from a Rip Van Winkle nap.

Five years ago, I started a great project for home speakers; the Zolasoid IIs:

http://forums.audioholics.com/forums/showthread.php?t=7436&highlight=nht

Well, I got one built, and it sounded divine next to my old JL sub. Life was grand, and I was going to get around to building the second one. But the setup sounded good, so there was no rush... Now, five years later, I'm almost finished with the second enclosure, and I find that NHT discontinued the sub series. Thought I had the other one in the house, but it looks like I never purchased it. DOH!

And it gets worse. I just looked through about 60 different subs available on the market, and they ALL have low qts and free air resonance above 20Hz, most of them over 25Hz. I can't find a single one that will give me a sealed box f3 anywhere near 25Hz like my NHT setup. Most end up at 40Hz or higher. Where did all the good subs go?

Can anyone help? My only viable option right now is to plop the ole JL 12W1 into the other enclosure for an f3 of 35Hz.

 

[JerryLove]

I don't know what you just said (reads Greek to me), but I found an Fs of 20.75 (http://www.soundsplinter.com/rlp18_subwoofer_information.html)

 

[GranteedEV]

What box size and qtc are we talkin about?

because the Exodus Maelstrom-X 21" in an 18 cu ft sealed box should do the trick and give you plenty of output with around 1000 w of power handling at ultra-low frequencies without excursion issues (which is likely louder than you'll ever listen). the qts is just supposed to be below the qtc right?

As should a maelstrom-X 18" in 350l box although for this one we're getting into critical damping. Again, keep it under 900 watts and you'll never have excursion problems. Since it's critically damped it won't get as loud as the 21 though, which is a given.

of course, keep in mind that stuffing a box will increase the enclosure volume the driver is seeing in the box. So for the qtc = .533 18" maelstrom box, you probably actually want to build a box with ~300l enclosure volume instead and then line its walls well to get that 25hz point, and roughly 420 L for the 21"

I'm guessing a TC Sounds Ultra 5400 18" most probably will as well... i'm just too lazy to model it

 

[gregz]

Holy Moley; 12 cubic feet! That Soundsplinter comes in at 9 cubic feet, Jerry. Yeah, I guess I should have given a bit more info.

My boxes are 3.5 cubic feet each, and I'm using these up to about 100 Hz as low frequency woofers, which is one of the reasons I can't fall back on ported designs. As long as QTC is below .82 I'm fine. The better damped the better, I say. The Shiva 12" would fit in the existing hole, and it has a 26mm travel. I guess that's a possibility, though in my enclosure the f3 is still 46Hz at a QTC of .55. How steep is the rolloff at that Q?

I appreciate the responses.

 

[GranteedEV]

sorry, i didn't realize you had the box size already set and needed a high qts value.

 

[gregz]

sorry, i didn't realize you had the box size already set and needed a high qts value.

I hadn't mentioned the box size when I asked the question. I have 450W available into 4 ohms, so the need for high qts is debatable if I consider slightly overdamped enclosures.

Your suggested brands in their 12" versions are distinct possibilities with qtc's in the neighborhood of .55 or so and the same awesome cone excursion.

 

[TLS Guy]

Holy Moley; 12 cubic feet! That Soundsplinter comes in at 9 cubic feet, Jerry. Yeah, I guess I should have given a bit more info.

My boxes are 3.5 cubic feet each, and I'm using these up to about 100 Hz as low frequency woofers, which is one of the reasons I can't fall back on ported designs. As long as QTC is below .82 I'm fine. The better damped the better, I say. The Shiva 12" would fit in the existing hole, and it has a 26mm travel. I guess that's a possibility, though in my enclosure the f3 is still 46Hz at a QTC of .55. How steep is the rolloff at that Q?

I appreciate the responses.

Roll off will be 12db per octave. But you can add eq,x-max permitting.

 

[GranteedEV]

You may as well also try modeling the Peerless 830845

 

[gregz]

You may as well also try modeling the Peerless 830845

Hey, that's a really good match for my enclosure volume, and not a bad f3 of about 34Hz. That's the closest match to my NHT yet.

Thanks!

 

[gregz]

Roll off will be 12db per octave. But you can add eq,x-max permitting.

I thought a sealed box with a low q had a much slower rolloff than 12db.

I don't have a graphic eq, so not looking to add to the stack 'o power unless I absolutely need to.

 

[annunaki]

One must look at the overall "q" of the enclosure, with woofer, to help determine the overall sound. One may be able to drop to a low q of say .5 to lessen the effects of the roll off by lowering the f3, however it comes at a price. An effective .5 qtc typically sounds very "dry" meaning that the bass sounds a bit thin. The driver also tends to lose power handling capabilities as the enclosure size increases to lower the effective "q". All of this can be done but it will still not lessen the normal roll off of 12 db/oct.

To effectively lessen the roll off, an eq must be used. However most drivers do not take well to eq below the f3 as they simply run out of xmax and power compression will begin to set in.

For instance, I use a JL Audio 12W7, which is one of the few drivers available that will allow for the additional eq below f3. This is in a sealed enclosure of 2.17ft^3 net (.708 Qtc net). In room I have +/-3db response from 16hz-88hz.

If you are after a woofer that has a natural f3 of 25hz it may take you a LONG time to find one in a 12", or you will need to allow for a larger enclosure than what you currently have with a larger driver.

 

[gregz]

One must look at the overall "q" of the enclosure, with woofer, to help determine the overall sound. One may be able to drop to a low q of say .5 to lessen the effects of the roll off by lowering the f3, however it comes at a price. An effective .5 qtc typically sounds very "dry" meaning that the bass sounds a bit thin. The driver also tends to lose power handling capabilities as the enclosure size increases to lower the effective "q". All of this can be done but it will still not lessen the normal roll off of 12 db/oct.

To effectively lessen the roll off, an eq must be used. However most drivers do not take well to eq below the f3 as they simply run out of xmax and power compression will begin to set in.

For instance, I use a JL Audio 12W7, which is one of the few drivers available that will allow for the additional eq below f3. This is in a sealed enclosure of 2.17ft^3 net (.708 Qtc net). In room I have +/-3db response from 16hz-88hz.

If you are after a woofer that has a natural f3 of 25hz it may take you a LONG time to find one in a 12", or you will need to allow for a larger enclosure than what you currently have with a larger driver.

Thanks, Annunaki. Those NHT's were rare birds to reach such a low f3 in relatively small sealed enclosures. I really screwed up by not buying that second one, but in the long run, I'll need to have a go-forward plan for driver replacement anyway so this junction was invevitable. It seems the majority of the industry has tweaked their designs to fit in the smallest boxes possible; I suppose a concession to the largest customer base of car audio. Even the Peerless 830845 is now gone, replaced by the 835017 that again gives up f3 to fit in a smaller enclosure.

That 12W7 has the same amount of excursion as the Exodus brand sub I found through GranteedEV's suggestions, providing a few options if I go the eq'd route and partially fill or cut down my enclosures for less volume. Speaking of eq'd systems, was the "stroke" specification on Bob Carver's Sunfire subwoofer simply 2 x Xmax?

 

[annunaki]

Thanks, Annunaki. Those NHT's were rare birds to reach such a low f3 in relatively small sealed enclosures. I really screwed up by not buying that second one, but in the long run, I'll need to have a go-forward plan for driver replacement anyway so this junction was invevitable. It seems the majority of the industry has tweaked their designs to fit in the smallest boxes possible; I suppose a concession to the largest customer base of car audio. Even the Peerless 830845 is now gone, replaced by the 835017 that again gives up f3 to fit in a smaller enclosure.

That 12W7 has the same amount of excursion as the Exodus brand sub I found through GranteedEV's suggestions, providing a few options if I go the eq'd route and partially fill or cut down my enclosures for less volume. Speaking of eq'd systems, was the "stroke" specification on Bob Carver's Sunfire subwoofer simply 2 x Xmax?

Stroke is not a true measured specification. Many companies refer to stroke as peak to peak excursion. Which for most companies means that you will be well past audible distortion limits. The great thing about many modern woofers in the vast increases in motor linearity which lowers distortion through the entire usable "stroke" if you will.

The JL Audio 12W7 and other woofers such as those from TC sounds and Exodus Audio have been 3rd party verified to have full motor force and maintain linearity through their published xmax specs. The JL 12w7 in specific has actually been 3rd party tested to 32mm one way linear excursion exceeding published specs by 4mm. Sadly with many companies this actually works in the reverse.

So knowing the 12W7 is good to 32mm one way linear, one could think of usable stroke to 64mm peak to peak or just over 2.5"

 

[TLS Guy]

I have been giving your problem a lot of thought and quite frankly as you envision it I have to give up!

Things have become geared differently.

1 is auto sound. As you state they want a lot of power in a small box.

For home audio the problem is HT.

Natural instruments, have little power below 60 HZ. Yes I know there are pipe organ recordings that have 32 ft stops. However these are usually used in a gentle subtle manner.

Now comes along HT and people want insane output to 20 Hz and below, because of Hollywood's obsession with LFE.

I think you are trying to make an integrated system. I'm on your wave length, but it is an uphill battle. I have done it, see my signature. But it is a steep climb.

Now in times past your NHT driver was fine, as it would make an integrated speaker for most music fine. Not now. When I model it, I find the driver is xmax limited below just above 40 Hz and can only handle 12 watts of power at 20 Hz. That would not please the HT crowd.

Now I assume that you want to crossover at 100 Hz and also use the driver for diffraction loss compensation to 600 Hz. That excludes most subs.

Now I used this driver, two per side.

With two of them it is quite sensitive and has a good xmax, and xmax can be exceeded.

I used a TL design and the system shakes up the room plenty. So it worked.

Now for sealed F3 is in the low forties. However it would tolerate some Eq. Because of cone break up the circuit for the diffraction compensation was not straightforward, but not that bad either. You could get what you want out of a Behringer unit.

I'm not sure why you want to dismiss a ported solution out of hand.

I have heard this unit ported driven up to the 350 Hz range in a three way.

If you used two of those in a ported enclosure you would end up with an enclosure about the size you want.

Name: Epic 10 inch
Type: Standard one-way driver
Company: TC sounds
No. of Drivers = 2
Mounting = Standard
Wiring = Parallel
Fs = 24 Hz
Qms = 7.5
Vas = 50 liters
Cms = 324 mm/N
Mms = 133 g
Rms = 0.00273 kg/s
Xmax = 18.1 mm
Xmech = 32.7 mm
P-Dia = 36.43 mm
Sd = 205 sq.cm
P-Vd = 0.0189 liters
Qes = 0.33
Re = 3.72 ohms
Le = 3.3 mH
Z = 4.1 ohms
BL = 15.2 Tm
Qts = 0.31
no = 0.202 %
1-W SPL = 85.2 dB
2.83-V SPL = 88.52 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box
Shape: Prism, square (optimum)
Vb = 1.199 cu.ft
Fb = 28.48 Hz
QL = 6.961
F3 = 27.01 Hz
Fill = minimal
No. of Vents = 1
Vent shape = rectangle
Vent ends = two flush
Hv = 6 in
Wv = 2.5 in
Lv = 39.12 in

Then you would have to go active for the first crossover point. I would send the LFE signal low pass fourth order at 60 Hz to both drivers via a dual channel buffer amp from the LFE output to the amps driving the 10 inch drivers. Then feed the diffraction signal to the upper drivers blended in to amps driving the upper 10" drivers.

Of course you will need four amps all together to drive your four 10" drivers.

This is the only way I can think of doing what you want on todays music and HT environment. I can assure you it works. If you do it right you would have an awesome system

If you use a big heavy sub driver in a sealed enclosure I don't think you will get decent integration with your other drivers.

You really need to revise your game plan in today's HT environment.

 

[annunaki]

Dr. Mark,

Quality/superb integration is possible using a sealed driver. A good eq such as the DCX2496 from Behringer really helps out of course.

I am currently running an active two-way stereo bookshelf pair along with my sealed 12W7. I have better integration now with my sub than I have yet experienced in my system.

Both the bookshelf speakers and the sub are run through the DCX. In all honesty I can only tell the sub is running when LFE is actually present (below 70hz or so) they blend so seamlessly.

I agree with you that the crossover will be extremely important considering his setup. An active solution such as the Behringer DCX2496 would be of benefit in this situation, though not necessary.

 

[riverwolf]

Gregz, it might help if you mention which NHT model you're looking for. Your cabinet volume suggests a 1259, but they weren't available to the DIY market 5 years ago, although the Madisound clone may still have been at that point.

In any case, I have a pair of original NHT 1259s that I would be willing to sell if it would help you out. The original 1259s are somewhat different than the Madi clones, if that's what you have, but they should be close enough that room effects will swamp the difference between the software models. I'm also in NC, like yourself, so we could possibly avoid shipping hassles depending on where you are. Tried to PM this, but need more posts. :-(

-Brent

 

[TLS Guy]

Dr. Mark,

Quality/superb integration is possible using a sealed driver. A good eq such as the DCX2496 from Behringer really helps out of course.

I am currently running an active two-way stereo bookshelf pair along with my sealed 12W7. I have better integration now with my sub than I have yet experienced in my system.

Both the bookshelf speakers and the sub are run through the DCX. In all honesty I can only tell the sub is running when LFE is actually present (below 70hz or so) they blend so seamlessly.

I agree with you that the crossover will be extremely important considering his setup. An active solution such as the Behringer DCX2496 would be of benefit in this situation, though not necessary.

Yes, I know that can work. But if you want to make the crossover to the mid higher and or use the bass driver for diffraction loss then you have limited choice. Most heavy sub drivers ideal for sealed enclosures do not fit the bill.

There is huge benefit from relieving small drivers of diffraction compensation for obvious reasons.

So he has the option of building what I would regard as a truly fully integrated speaker system versus what would basically be a bookshelf system with sub. The OP will need to make these choices, which is why I advised him to reconsider these plans. I'm not saying which way he should go, just laying out the options. I get the impression he wanted a full range integrated speaker, but may be I read too much into his question.

I agree a unit like the Behringer would make his task easier.

I do believe there is validity to my approach though. I had a college prof. here two weeks ago who is a friend of my sons. He teaches electronic music and composition at a college in the Twin Cities. He is well versed in audio systems and speakers, and he is never happy! Who is?

We played a wide variety of music here including his own compositions.

However when I played him the Laplander drumming from the first movement of the Aho 12th symphony, he was truly astonished. There are a large number of big drums hit very hard. He said he had never before heard that distinctive sound of a drum being hit very hard reproduced perfectly by a speaker before. I really doubt I could get that effect without a true full range speaker system in every sense of the word.

 

[TLS Guy]

Gregz, it might help if you mention which NHT model you're looking for. Your cabinet volume suggests a 1259, but they weren't available to the DIY market 5 years ago, although the Madisound clone may still have been at that point.

In any case, I have a pair of original NHT 1259s that I would be willing to sell if it would help you out. The original 1259s are somewhat different than the Madi clones, if that's what you have, but they should be close enough that room effects will swamp the difference between the software models. I'm also in NC, like yourself, so we could possibly avoid shipping hassles depending on where you are. Tried to PM this, but need more posts. :-(

-Brent

That would be his best option, if he wants to stick to his original plan. It was the 1259 I modeled from the data base in Box Pro.

 

[riverwolf]

That would be his best option, if he wants to stick to his original plan. It was the 1259 I modeled from the data base in Box Pro.

Something sounds off with your model. Using the original NHT 1259 specs, WinISD shows Xmax power at 105 watts @ 20Hz in 3.5 ft^3 and 133 watts in the 2.8 ft^3 as used in the NHT 3.3 loudspeaker. Regardless, since output is a function of displacement, the 1259 will have the same output as any other 12" driver at 13mm of excursion, it just needs less power to get there due to a "floppy" suspension, which is also why Ken strongly discouraged its use for ported alignments.

In real world use living with the pair of 1259s as dedicated subs for HT duty for probably 10 years, output for me was never really a problem. At least in terms of running into the 1259s' physical limits. I replaced them with various ported designs for deeper response, but within their useful frequency range they never complained despite being driven by a NAD 2400THX that's supposedly capable of 400 wpc bursts. Listening level tastes will vary...I typically listen at -15 to Reference, putting measured peaks with all channels on (not just the subs) in the mid-high 90db range. Going above 100dB starts to get into my discomfort threshold, although there are times it's called for...I recently found myself listening to Rush's "Snakes & Arrows" blu-ray at -8.

-Brent

 

[TLS Guy]

Something sounds off with your model. Using the original NHT 1259 specs, WinISD shows Xmax power at 105 watts @ 20Hz in 3.5 ft^3 and 133 watts in the 2.8 ft^3 as used in the NHT 3.3 loudspeaker. Regardless, since output is a function of displacement, the 1259 will have the same output as any other 12" driver at 13mm of excursion, it just needs less power to get there due to a "floppy" suspension, which is also why Ken strongly discouraged its use for ported alignments.

In real world use living with the pair of 1259s as dedicated subs for HT duty for probably 10 years, output for me was never really a problem. At least in terms of running into the 1259s' physical limits. I replaced them with various ported designs for deeper response, but within their useful frequency range they never complained despite being driven by a NAD 2400THX that's supposedly capable of 400 wpc bursts. Listening level tastes will vary...I typically listen at -15 to Reference, putting measured peaks with all channels on (not just the subs) in the mid-high 90db range. Going above 100dB starts to get into my discomfort threshold, although there are times it's called for...I recently found myself listening to Rush's "Snakes & Arrows" blu-ray at -8.

-Brent

I have the greater confidence in Box Pro. The model from the numbers imported from the data base clearly show xmax limitations starting just below 45 Hz. The maximum electronic power curve clearly shows this driver maxed by 12 watts at 20 Hz. And frankly that is what you would expect of a highly compliant suspension in a relatively large box. The graphs looked like I expected from the T/S parameters.