Which Driver for Sub?

[the hand of boredom]

To those technically inclined, which driver would perform better based on the specs below, and given the same enclosure (2 cu ft) and amplifier (370W A/B)

12" Driver One
Fs = 21.3 hertz
Qms = 4.308
Vas = 4.849 cu.ft or 137.3 liters
Cms = 0.071 in/Ib
Mms = 4.903 oz or 139 grams
Rms = 9.495 Ibs/sec
Xmax = 16 mm
Sd = 76 sq.in or Dia = 9.83 in or 250 mm
Qes = 0.298
Re = 3 ohms
Z = 4.0 ohms
BL = 13.7
Qts = 0.279
Sens = 88.4 dB

12" Driver 2
fs 26 Hz
BL 11.24
VAS 88 L
Qms 7.42
Qts 0.472
Sd 530 cm2
Re 2.80 ohms
Le 1.0 mH

THOB

[Kevio]

Best results will be with a driver carefully matched to the enclosure. There are formulas for doing so. I don't have the expertise to give you advice on this. Building and tuning speakers is a hobby in itself. I know there are plans, tutorial and expertise available on the internet.

[audio amateur]

My question is, are the boxes sealed or vented? If vented, what is the tuning frequency?
I get awkward results plugging in the numbers. The low Qts on the first driver suggests good compatibilty with a vented box, which it models fairly well with, however not so with one that is 2cf. It needs to be larger. Neither of the two drivers model well with a 2cf sealed box, with a cut-off of -6dB at around 40Hz. Not too good IMO.
Could you be more specific where these drivers come from as well as the amp?

[the hand of boredom]

http://www.rythmikaudio.com/F12SE_specs.html

http://www.rythmikaudio.com/GR_drivers.html

I'm looking at the F12SE, possibly two; or the F12 with the GR drivers.

Thanks for the input.

[Kevio]

My question is, are the boxes sealed or vented? If vented, what is the tuning frequency?

We need to know more about the enclosure, not more about the drivers.

[audio amateur]

Ok, I see what you mean. I doubt you can go wrong with either choices. It's too subjective as the Servo base of the package alters the real response very much, which is why my above post means nothing in this case. I'm trying to access the link which presumably mentions the differences between the two, but it's not working at the moment. As far as I can tell, the first and very apparent difference is the material of the cone. One is paper (the GR) and the other is aluminium. I'd go with the aluminium possibly, and if you can scrap the extra 100$, go with the gloss black 'signature' finish. Looks amazing. Unless you have a big room in which case I'd suggest the 15" version. Either are a very good choice IMO and I am very much jealous. . I might add that you can always make your own box to save a little $$.
Good look and keep us posted if you will. I'd love to hear some feedback.

[Feanor]

To those technically inclined, which driver would perform better based on the specs below, and given the same enclosure (2 cu ft) and amplifier (370W A/B)

12" Driver One
Fs = 21.3 hertz
Qms = 4.308
Vas = 4.849 cu.ft or 137.3 liters
Cms = 0.071 in/Ib
Mms = 4.903 oz or 139 grams
Rms = 9.495 Ibs/sec
Xmax = 16 mm
Sd = 76 sq.in or Dia = 9.83 in or 250 mm
Qes = 0.298
Re = 3 ohms
Z = 4.0 ohms
BL = 13.7
Qts = 0.279
Sens = 88.4 dB

12" Driver 2
fs 26 Hz
BL 11.24
VAS 88 L
Qms 7.42
Qts 0.472
Sd 530 cm2
Re 2.80 ohms
Le 1.0 mH

THOB

THOB,

I ran the specifications through my Bass Box Pro program and got the following results.

For the first driver, BBPro:

• Don't use a closed box;
• Use a vented box of about 1.4 ft^3 using light damping and a 2" x 7" vent to get response down 3 dB (F3) at 39 Hz.

For the second driver:

• Use closed box of 1.25 ft^3 with light damping for F3 = 47 Hz
• Use a box of 4.5 ft^3 (pretty big) with light damping and a 3" x 7.4" vent for F3 = 22Hz.
• Or for slightly suboptimal results, use your 2 ft^3 closed box for F3 = 50 Hz.

Given the 2 cu.ft. box, I'd recommend the second driver in a closed box.

If it's feasible, you might reduce the internal volume of the box using, say, rigid styrofoam getting you closer to the first driver, vented. But I'm not sure I'd bother: the closed box might have a higher F3 but the response roll-off below that is more gradual.

[Feanor]

THOB,

I ran the specifications through my Bass Box Pro program and got the following results.

For the first driver, BBPro:

• Don't use a closed box;
• Use a vented box of about 1.4 ft^3 using light damping and a 2" x 7" vent to get response down 3 dB (F3) at 39 Hz.

For the second driver:

• Use closed box of 1.25 ft^3 with light damping for F3 = 47 Hz
• Use a box of 4.5 ft^3 (pretty big) with light damping and a 3" x 7.4" vent for F3 = 22Hz.
• Or for slightly suboptimal results, use your 2 ft^3 closed box for F3 = 50 Hz.

Given the 2 cu.ft. box, I'd recommend the second driver in a closed box.

If it's feasible, you might reduce the internal volume of the box using, say, rigid styrofoam getting you closer to the first driver, vented. But I'm not sure I'd bother: the closed box might have a higher F3 but the response roll-off below that is more gradual.

What I suggested above is not necessarily invalid, however Rythmik drivers are mean to be servo controlled using Rythmic amplifiers; Rythmik provides cabinet plans for their speakers: it would be advisable to follow these plans as closely as possible. However what I suggested above is not necessarily invalid.

[the hand of boredom]

this is info from the website:

"GR SW-12-04 (driver 1)
Designed for a sealed box with 1.5 cu ft volume. The GR drivers use a lower mass paper cone, which has a slightly better transient response. The result is slightly better dynamics. At higher output, due to less cone stiffness, the performance suffers more due to the pressure placed on the cone."

So I'm thinking that the better transient response would yield a better attack and decay of the sub-bass. With two subs, output can be reduced to half thus reducing any performance issues.

Having said that, I really do like the look of the silver driver on piano black. Pure class. Cost won't be an issue. I want to purchase what will perform better in producing true and quickly.

The room is 12 x 10.5 x 21.

[the hand of boredom]

Hey Bill, it's crazy your program recommends using the GR driver (#1) vented. The GR website claims it works best sealed. Perhaps this is a sham

The enclosures are heavily braced internally, this may be the source of volume reduction to 1.5 cuft.

I've just emailed Brian at RA for that info

When you comin' over for a listen?

THOB

[Feanor]

Hey Bill, it's crazy your program recommends using the GR driver (#1) vented. The GR website claims it works best sealed. Perhaps this is a sham

The enclosures are heavily braced internally, this may be the source of volume reduction to 1.5 cuft.

I've just emailed Brian at RA for that info

When you comin' over for a listen?

THOB

Hand,

The Rythimiks are a great looking product to me. I'd love to hear them.

I'd go with whatever they recommend for a cabinet; the fact that they are servo controlled and probably equalized means that standard calculations aren't very meaningful.

[the hand of boredom]

The net internal volume is 1.7 cuft.

My debate is whether to do the aluminum or paper driver. The paper driver is lighter and as a result likely to be accelerated and decelerated better. From what I've read, this can yield better transients - better attack and decay right?

But if two subs are used, output is halved thus reducing excursion and distortion.

Hell, I'm gonna get the aluminum driver with the piano black finish.

Thanks, all.

[the hand of boredom]

http://www.hometheatershack.com/foru...ealed-56l.html

Here's a link to some tests done by a third party...

[audio amateur]

Nice one HOB, I hope you enjoy it! Let us know what you think!

[flippo]

A good inexpensive driver is the Infinity Kappa perfect 12VQ. Very low distortion and can be used in several different ways due to the choice of inserts (lowq or midq)

[This Guy]

A good inexpensive driver is the Infinity Kappa perfect 12VQ. Very low distortion and can be used in several different ways due to the choice of inserts (lowq or midq)

That driver is made specifically for cars. They don't list any technical specifications (its t/s parameters) so we cannot judge whether it would work well in a much bigger cabin (a house). Just because it works good for you in a car does not mean it will work in a house. Perhaps it could work well, but you wouldn't know until it was bought and tried in a house because they don't list its parameters. And either way, the Rhythmik sub with its servo circuit will sound much better due to its extremely low distortion.

[flippo]

This driver does an excellent job in the home as it is very low distortion and linear. It was reccomended to me on another website by a very experienced speaker builder (if you see the equipment he has built you would listen also!). here is the t/s .

Name: Kappa Perfect 12 VQ No insert
Type: Standard one-way driver
Company: Infinity Systems Inc.
No. of Drivers = 1
Fs = 22.9 Hz
Qms = 10.29
Vas = 96.43 liters
Cms = 0.323 mm/N
Mms = 176.4 g
Rms = 2.398 kg/s
Xmax = 16.75 mm
Xmech = 25.13 mm
P-Dia = 250 mm
Sd = 491 sq.cm
P-Vd = 0.822 liters
Qes = 0.79
Re = 4.42 ohms
Le = 1.14 mH
Z = 4 ohms
BL = 11.92 Tm
Pe = 400 watts
Qts = 0.74
no = 0.141 %
1-W SPL = 83.65 dB
2.83-V SPL = 89 dB
-----------------------------------------
Box Properties
Name:
Type: Closed Box
Shape: Prism, square (optimum)
Vb = 4.814 cu.ft
Qtc = 0.74
QL = 12.58
F3 = 27.75 Hz
Fill = heavy


Infinity's alignment.

Name: Kappa Perfect 12 VQ No insert.
Type: Standard one-way driver
Company: Infinity Systems Inc.
No. of Drivers = 1
Fs = 22.9 Hz
Qms = 10.29
Vas = 96.43 liters
Cms = 0.323 mm/N
Mms = 176.4 g
Rms = 2.398 kg/s
Xmax = 16.75 mm
Xmech = 25.13 mm
P-Dia = 250 mm
Sd = 491 sq.cm
P-Vd = 0.822 liters
Qes = 0.79
Re = 4.42 ohms
Le = 1.14 mH
Z = 4 ohms
BL = 11.92 Tm
Pe = 400 watts
Qts = 0.74
no = 0.141 %
1-W SPL = 83.65 dB
2.83-V SPL = 89 dB
-----------------------------------------
Box Properties
Name:
Type: Closed Box
Shape: Prism, square
Vb = 1.25 cu.ft
Qtc = 1.003
QL = 20
F3 = 32.27 Hz
Fill = heavy

Now you might at first sight not see much advantage in the larger box. However there is. Both produce 109 db to just above the F3. However the larger box has a Qtc of 0.74, which is the perfect balance between a box that is over tight and one that is over resonant. The smaller box will just tend to the boomey. I would say the larger box would be a good sounding sub.

Now the vented box. In my view only the low insert is really suitable for vented alignment. I don't care for the sound of high q drivers in vented boxes.


Name: Kappa Perfect 12 VQ low insertt
Type: Standard one-way driver
Company: Infinity Systems Inc.
No. of Drivers = 1
Fs = 22.9 Hz
Qms = 10.29
Vas = 96.43 liters
Cms = 0.323 mm/N
Mms = 176.4 g
Rms = 2.398 kg/s
Xmax = 16.75 mm
Xmech = 25.13 mm
P-Dia = 250 mm
Sd = 491 sq.cm
P-Vd = 0.822 liters
Qes = 0.36
Re = 4.42 ohms
Le = 1.14 mH
Z = 4 ohms
BL = 11.92 Tm
Pe = 400 watts
Qts = 0.34
no = 0.141 %
1-W SPL = 83.65 dB
2.83-V SPL = 89 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box
Shape: Prism, square (optimum)
Vb = 3.024 cu.ft
Fb = 21.38 Hz
QL = 6.563
F3 = 21.58 Hz
Fill = minimal
No. of Vents = 1
Vent shape = round
Vent ends = two flared
Dv = 4 in
Lv = 22.49 in

[hydroman]

Me? 370w amp is low for a 12" sub. Pick the vented enclosure and the more efficient driver.

[This Guy]

This driver does an excellent job in the home as it is very low distortion and linear. It was reccomended to me on another website by a very experienced speaker builder (if you see the equipment he has built you would listen also!). here is the t/s .

Name: Kappa Perfect 12 VQ No insert
Type: Standard one-way driver
Company: Infinity Systems Inc.
No. of Drivers = 1
Fs = 22.9 Hz
Qms = 10.29
Vas = 96.43 liters
Cms = 0.323 mm/N
Mms = 176.4 g
Rms = 2.398 kg/s
Xmax = 16.75 mm
Xmech = 25.13 mm
P-Dia = 250 mm
Sd = 491 sq.cm
P-Vd = 0.822 liters
Qes = 0.79
Re = 4.42 ohms
Le = 1.14 mH
Z = 4 ohms
BL = 11.92 Tm
Pe = 400 watts
Qts = 0.74
no = 0.141 %
1-W SPL = 83.65 dB
2.83-V SPL = 89 dB
-----------------------------------------
Box Properties
Name:
Type: Closed Box
Shape: Prism, square (optimum)
Vb = 4.814 cu.ft
Qtc = 0.74
QL = 12.58
F3 = 27.75 Hz
Fill = heavy


Infinity's alignment.

Name: Kappa Perfect 12 VQ No insert.
Type: Standard one-way driver
Company: Infinity Systems Inc.
No. of Drivers = 1
Fs = 22.9 Hz
Qms = 10.29
Vas = 96.43 liters
Cms = 0.323 mm/N
Mms = 176.4 g
Rms = 2.398 kg/s
Xmax = 16.75 mm
Xmech = 25.13 mm
P-Dia = 250 mm
Sd = 491 sq.cm
P-Vd = 0.822 liters
Qes = 0.79
Re = 4.42 ohms
Le = 1.14 mH
Z = 4 ohms
BL = 11.92 Tm
Pe = 400 watts
Qts = 0.74
no = 0.141 %
1-W SPL = 83.65 dB
2.83-V SPL = 89 dB
-----------------------------------------
Box Properties
Name:
Type: Closed Box
Shape: Prism, square
Vb = 1.25 cu.ft
Qtc = 1.003
QL = 20
F3 = 32.27 Hz
Fill = heavy

Now you might at first sight not see much advantage in the larger box. However there is. Both produce 109 db to just above the F3. However the larger box has a Qtc of 0.74, which is the perfect balance between a box that is over tight and one that is over resonant. The smaller box will just tend to the boomey. I would say the larger box would be a good sounding sub.

Now the vented box. In my view only the low insert is really suitable for vented alignment. I don't care for the sound of high q drivers in vented boxes.


Name: Kappa Perfect 12 VQ low insertt
Type: Standard one-way driver
Company: Infinity Systems Inc.
No. of Drivers = 1
Fs = 22.9 Hz
Qms = 10.29
Vas = 96.43 liters
Cms = 0.323 mm/N
Mms = 176.4 g
Rms = 2.398 kg/s
Xmax = 16.75 mm
Xmech = 25.13 mm
P-Dia = 250 mm
Sd = 491 sq.cm
P-Vd = 0.822 liters
Qes = 0.36
Re = 4.42 ohms
Le = 1.14 mH
Z = 4 ohms
BL = 11.92 Tm
Pe = 400 watts
Qts = 0.34
no = 0.141 %
1-W SPL = 83.65 dB
2.83-V SPL = 89 dB
-----------------------------------------
Box Properties
Name:
Type: Vented Box
Shape: Prism, square (optimum)
Vb = 3.024 cu.ft
Fb = 21.38 Hz
QL = 6.563
F3 = 21.58 Hz
Fill = minimal
No. of Vents = 1
Vent shape = round
Vent ends = two flared
Dv = 4 in
Lv = 22.49 in

Alright, you're right. I couldn't find the T/S paramters for it, so I was naturally skeptical. It looks like a great driver, just a bit inefficient. It looks good if you have a lot of power on tap.