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Thinking about doing Infinite Baffle with 8 X15in subs or buy another jbl 8400p

post #1 of 3
Thread Starter 
My room is 12x20X8 and can be closed off. This is a family/media room. If I buy another Jbl 8400p I will have them placed in the far left and far right of the screen wall. So, that would be the easiest option.

Or will the subs I have to choose from work with an IB setup. I understand the concept but do not fully understand specs that will make a good IB setup. I know of the Fi 18, but I am only able to choose from only the following subs.

8 X JBL GT5-15
8 X JBL GTO1514
? X JBL W15GTi MKII (Will this be better than the two above in an IB setup. From my understanding IB set uses less power and this would be over kill?)

I plan on putting the 8 subs in the Attic, with two sets of 4 in each manifold.
Will it be worth it to try an IB setup with the subs I have listed? Or any other JBL sub in an IB setup.


Thanks,
post #2 of 3
Quote:
Originally Posted by moody2876 View Post

My room is 12x20X8 and can be closed off. This is a family/media room. If I buy another Jbl 8400p I will have them placed in the far left and far right of the screen wall. So, that would be the easiest option.
Or will the subs I have to choose from work with an IB setup. I understand the concept but do not fully understand specs that will make a good IB setup. I know of the Fi 18, but I am only able to choose from only the following subs.
8 X JBL GT5-15
8 X JBL GTO1514
? X JBL W15GTi MKII (Will this be better than the two above in an IB setup. From my understanding IB set uses less power and this would be over kill?)

I plan on putting the 8 subs in the Attic, with two sets of 4 in each manifold.
Will it be worth it to try an IB setup with the subs I have listed? Or any other JBL sub in an IB setup.
Thanks,

For questions about the IB you'll likely get more responses in the DIY section: http://www.avsforum.com/f/155/diy-speakers-and-subs

Why are you restricted to JBL subs? One quick (and probably oversimplified) way to determine if a driver will work well in an IB is to look at the Qts parameter. In an IB the system Q will be about equal to the driver Qts. Look for a driver with a Qts around .707 (higher Q will be "boomier" lower Q will be "drier"). The other big thing to look for is displacement - look for a driver with large Xmax. Power handling isn't important as you'll run into suspension limits before thermal limits.

I've been running an IB with 4 AE IB15's for a couple years now and I still (surprisingly) have very little desire to upgrade...
post #3 of 3
Thread Starter 
Thanks for the input, the reason for JBL is I am able to purchase them at a good price. Looking at the specs seems GT5-15 would be better. I can get 8 of the GT5-15 for little more than 1 FI 18.

This is the GT5-15 Parameters,

DIAMETER: 15" (381MM)
SENSITIVITY (2.83V @ 1M): 92dB
POWER HANDLING: 300WRMS 1200WPEAK
FREQUENCY RESPONSE: 25Hz – 400Hz
NOMINAL IMPEDANCE: 4 OHMS
VOICE-COIL DIAMETER: 2" (51MM)
DIMENSIONS:
THIELE-SMALL PARAMETERS
VOICE-COIL DC RESISTANCE: REVC (OHMS) . . . . . . 3.63
VOICE-COIL INDUCTANCE @ 1KHZ: LEVC (MH) . . . . . . . 2.42
DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 132.5
SD (M2) . . . . . . . 855.00
MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 16.53
COMPLIANCE VOLUME: VAS (FT3). . . . . . . . . 3.76
VAS (LITERS) . . . . . 106.5
SUSPENSION COMPLIANCE: CMS (μM/N) . . . . 102.00
MOVING MASS, AIR LOAD: MMS (GRAMS). . . . 332.00
MOVING MASS, DIAPHRAGM: MMD (GRAMS) . . . 317.00
FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 27.30
MECHANICAL Q: QMS . . . . . . . . . . . 5.70
ELECTRICAL Q: QES . . . . . . . . . . . 0.76
TOTAL Q: QTS . . . . . . . . . . . . 0.67
MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . . 0.31
HAG (MM) . . . . . . . . 8.00
VOICE-COIL HEIGHT: HVC (IN) . . . . . . . . . 1.45
HVC (MM). . . . . . . . . . 37
MAXIMUM EXCURSION: XMAX (IN) . . . . . . . . 0.57
XMAX (MM) . . . . . . 14.50

GT0 1514 driver is available, and it seems to have a better spec, but I cannot load these either without the same error?

DIAMETER: 15" (381MM)
SENSITIVITY (2.83V @ 1M): 93dB
POWER HANDLING: 350WRMS (1400WPEAK)
FREQUENCY RESPONSE: 23HZ ~ 400HZ
NOMINAL IMPEDANCE: 4 OHMS
VOICE COIL DIAMETER: 2.0" (51.0MM)
DIMENSIONS: mounting depth 6-13/16" (172mm) cutout diameter 13-15/16" (354mm) outer diameter 15-5/16" (389mm)

THIELE-SMALL PARAMETERS
VOICE COIL DC RESISTANCE: REVC (OHMS) . . . . . . 3.80
VOICE COIL INDUCTANCE@ 1KHZ: LEVC (MH) . . . . . . . 3.05
DRIVER RADIATING AREA: SD (IN2) . . . . . . . . 128.7
SD (M2) . . . . . . . 830.00
MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 17.13
COMPLIANCE VOLUME: VAS (FT3). . . . . . . . . 5.42
VAS (LITERS). . . . . 153.50
SUSPENSION COMPLIANCE: CMS (μM/N) . . . . 156.00
MOVING MASS, AIR LOAD: MMS
MD
(GRAMS) . . . 257.00
MOVING MASS, DIAPHRAGM: M (GRAMS) . . . 243.00
FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 25.10
MECHANICAL Q: QMS . . . . . . . . . . . 7.08
ELECTRICAL Q: QES . . . . . . . . . . . 0.52
TOTAL Q: QTS . . . . . . . . . . . 0.49
MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . . 0.31
HAG (MM) . . . . . . . . 8.00
VOICE COIL HEIGHT: HVC (IN) . . . . . . . . . 1.45
HVC (MM). . . . . . . . . . 37
MAXIMUM EXCURSION: XMAX (IN). . . . . . . . .0.57
XMAX (MM) . . . . . . 14.50
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