Subwoofer Displacement Volume...

[Mister.Lull]

Hey All,

I'm building a new subwoofer enclosure and can't, for the life of me,
find the displacement volume of the sub on the Thiele-Small
Parameters! It's a JBL GTO 1004D. Any ideas?

I'm going to paste the Thiele-Small Parameters and specifications
below, in the hopes that someone will be able to point something out
in the way of perhaps calculating a volume (or something like that)...

SPECIFICATIONS

DIAMETER: 10" (254MM)
SENSITIVITY (2.83 V @ 1 M): 91 dB
POWER HANDLING: 250 W 1000 WPEAK RMS
FREQUENCY RESPONSE: 25 ~ 400 HZ
NOMINAL IMPEDANCE: 2 or 8 OHMS
VOICE-COIL DIAMETER: 2.0" (51.0 MM)

mounting depth: 4-9/16" (116 mm)
cutout diameter: 9-1/8" (232mm)
outer diameter: 10-3/8" (264mm)

THIELE-SMALL PARAMETERS

VOICE COIL DC RESISTANCE: REVC (OHMS) . . . . . . 1.90
VOICE COIL INDUCTANCE @ 1 KHZ: LEVC (MH) . . . . . . . 1.10
DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 55.03
SD (M2) . . . . . . . 355.00
MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 9.90
COMPLIANCE VOLUME: VAS (FT3) . . . . . . . . 1.51
VAS (LITERS) . . . . . 42.66
SUSPENSION COMPLIANCE: CMS (µM/N) . . . . 237.00
MOVING MASS, AIR LOAD: MMS (GRAMS). . . . 139.40
MOVING MASS, DIAPHRAGM: MMD (GRAMS) . . . 135.50
FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 27.70
MECHANICAL Q: QMS . . . . . . . . . . . 6.89
ELECTRICAL Q: QES . . . . . . . . . . . 0.47
TOTAL Q: QTS . . . . . . . . . . . . 0.44
MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . 3/8
HAG (MM) . . . . . . . . 9.00
VOICE-COIL HEIGHT: HVC (IN) . . . . . . 1-5/16
HVC (MM) . . . . . . . . . . 34
MAXIMUM EXCURSION: XMAX (IN) . . . . . . . . 1/2
XMAX (MM) . . . . . . 12.50

~Mister.Lull

[KU40[_30_]]

I'd use .08-.1 cubic feet. it'll be close enough.


--
KU40

[Matt Ion]

KU40 wrote:
> I'd use .08-.1 cubic feet. it'll be close enough.

You sure about the location of that decimal? With a 12"x12" mounting
plate, that box would be barely an inch deep...

Based on a few 10" subs I've built boxes for that DID include
recommended box sizes, I'd say about 1.0 to 1.2 cu. ft. for a sealed box...

[Matt Ion]

Mister.Lull wrote:
> Hey All,
>
> I'm building a new subwoofer enclosure and can't, for the life of me,
> find the displacement volume of the sub on the Thiele-Small
> Parameters! It's a JBL GTO 1004D. Any ideas?
>
> I'm going to paste the Thiele-Small Parameters and specifications
> below, in the hopes that someone will be able to point something out
> in the way of perhaps calculating a volume (or something like that)...
>
> SPECIFICATIONS
>
> DIAMETER: 10" (254MM)
> SENSITIVITY (2.83 V @ 1 M): 91 dB
> POWER HANDLING: 250 W 1000 WPEAK RMS
> FREQUENCY RESPONSE: 25 ~ 400 HZ
> NOMINAL IMPEDANCE: 2 or 8 OHMS
> VOICE-COIL DIAMETER: 2.0" (51.0 MM)
>
> mounting depth: 4-9/16" (116 mm)
> cutout diameter: 9-1/8" (232mm)
> outer diameter: 10-3/8" (264mm)
>
> THIELE-SMALL PARAMETERS
>
> VOICE COIL DC RESISTANCE: REVC (OHMS) . . . . . . 1.90
> VOICE COIL INDUCTANCE @ 1 KHZ: LEVC (MH) . . . . . . . 1.10
> DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 55.03
> SD (M2) . . . . . . . 355.00
> MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 9.90
> COMPLIANCE VOLUME: VAS (FT3) . . . . . . . . 1.51
> VAS (LITERS) . . . . . 42.66
> SUSPENSION COMPLIANCE: CMS (µM/N) . . . . 237.00
> MOVING MASS, AIR LOAD: MMS (GRAMS). . . . 139.40
> MOVING MASS, DIAPHRAGM: MMD (GRAMS) . . . 135.50
> FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 27.70
> MECHANICAL Q: QMS . . . . . . . . . . . 6.89
> ELECTRICAL Q: QES . . . . . . . . . . . 0.47
> TOTAL Q: QTS . . . . . . . . . . . . 0.44
> MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . 3/8
> HAG (MM) . . . . . . . . 9.00
> VOICE-COIL HEIGHT: HVC (IN) . . . . . . 1-5/16
> HVC (MM) . . . . . . . . . . 34
> MAXIMUM EXCURSION: XMAX (IN) . . . . . . . . 1/2
> XMAX (MM) . . . . . . 12.50
>
> ~Mister.Lull

Using the calculator here: http://www.audiogrid.com/audio/

I get a box size of 0.9840026990553303 cu. ft. Or essentially 1.0.

[Mister.Lull]

Hey Matt,

I'm actually asking about just the displacement volume of the sub
itself.

I've already put together a box design - but to complete the
calculations for tuning the whole enclosure, I need to know what
volume to subtract (along with the port volume) from the box...

~Mister.Lull

On Jun 14, 11:30 am, Matt Ion > wrote:
> Mister.Lull wrote:
> > Hey All,
>
> > I'm building a new subwoofer enclosure and can't, for the life of me,
> > find the displacement volume of the sub on the Thiele-Small
> > Parameters! It's a JBL GTO 1004D. Any ideas?
>
> > I'm going to paste the Thiele-Small Parameters and specifications
> > below, in the hopes that someone will be able to point something out
> > in the way of perhaps calculating a volume (or something like that)...
>
> > SPECIFICATIONS
>
> > DIAMETER: 10" (254MM)
> > SENSITIVITY (2.83 V @ 1 M): 91 dB
> > POWER HANDLING: 250 W 1000 WPEAK RMS
> > FREQUENCY RESPONSE: 25 ~ 400 HZ
> > NOMINAL IMPEDANCE: 2 or 8 OHMS
> > VOICE-COIL DIAMETER: 2.0" (51.0 MM)
>
> > mounting depth: 4-9/16" (116 mm)
> > cutout diameter: 9-1/8" (232mm)
> > outer diameter: 10-3/8" (264mm)
>
> > THIELE-SMALL PARAMETERS
>
> > VOICE COIL DC RESISTANCE: REVC (OHMS) . . . . . . 1.90
> > VOICE COIL INDUCTANCE @ 1 KHZ: LEVC (MH) . . . . . . . 1.10
> > DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 55.03
> > SD (M2) . . . . . . . 355.00
> > MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 9.90
> > COMPLIANCE VOLUME: VAS (FT3) . . . . . . . . 1.51
> > VAS (LITERS) . . . . . 42.66
> > SUSPENSION COMPLIANCE: CMS (µM/N) . . . . 237.00
> > MOVING MASS, AIR LOAD: MMS (GRAMS). . . . 139.40
> > MOVING MASS, DIAPHRAGM: MMD (GRAMS) . . . 135.50
> > FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 27.70
> > MECHANICAL Q: QMS . . . . . . . . . . . 6.89
> > ELECTRICAL Q: QES . . . . . . . . . . . 0.47
> > TOTAL Q: QTS . . . . . . . . . . . . 0.44
> > MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . 3/8
> > HAG (MM) . . . . . . . . 9.00
> > VOICE-COIL HEIGHT: HVC (IN) . . . . . . 1-5/16
> > HVC (MM) . . . . . . . . . . 34
> > MAXIMUM EXCURSION: XMAX (IN) . . . . . . . . 1/2
> > XMAX (MM) . . . . . . 12.50
>
> > ~Mister.Lull
>
> Using the calculator here:http://www.audiogrid.com/audio/
>
> I get a box size of 0.9840026990553303 cu. ft. Or essentially 1.0.- Hide quoted text -
>
> - Show quoted text -

[Matt Ion]

Mister.Lull wrote:
> Hey Matt,
>
> I'm actually asking about just the displacement volume of the sub
> itself.
>
> I've already put together a box design - but to complete the
> calculations for tuning the whole enclosure, I need to know what
> volume to subtract (along with the port volume) from the box...

Ooooooohhhh...

Well that's not one of the Theile/Small parameters anyway, which is
probably why it's not listed there :)

Best thing to do is just calculate it on the area of a cone given the
sub's radius and depth, using the standard (pi*r^2*h)/3. It won't be
exact, but it'll be close enough.

Here's a handy calculator that will also let you factor in the magnet
somewhat: http://grapevine.abe.msstate.edu/~fto/tools/vol/cone.html

Just keep in mind that even that won't be EXACT unless you want to
calculate the speaker cone and the magnet separately... and don't forget
to factor in the volume of the basket materials themselves... the magnet
eats up more room, but the cone being taped eats less than the straight
calculation... well you get the idea. You could go nuts trying to
measure it down to the cubic micron...

At the end of the day, calculating for a simple cone will get you "close
enough". If you figure 4.5" depth and 5" radius, you end up with about
118 cu. in, or 0.068 cu. ft. If you figure a 1.5 cu. ft. enclosure
(just pulling that number out as an example), that's only a 4.5% change
in airspace. Any differences you get in calculating higher tolerances
than that will be insignificant. Heck, 0.068 cu. ft. itself is almost
insignificant, and the bigger the box design, the more insignificant it
becomes. :-)

[Matt Ion]

Matt Ion wrote:
> ...but the cone being taped ...

uh... that's TAPERED.

Duh.