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I would like to build a large AV subwoofer, but need some advice!

24K views 70 replies 11 participants last post by  katialylla2006 
#1 ·
Hello all,

My first post, and I am UK based, so first a big hello to all.

So.... I would like to build a large subwoofer, this is to be used in a large poor acoustic/room around 80ft by 60ft with a suspended ceiling and some reflective surfaces, it is a large workshop within a large warehouse where my and a coleague have decided (and been allowed to) to put some kit together for movies. (Since having kids there were sacrifices for us both at our homes :))

The speakers in this system are Cerwin Vega Mk1 V-152's with a sensitivity of 103db, and I feel they cut off around 40-50hz, we have tried a couple of small domestic AV subs and I feel such cannot match the main speakers. Amp is an ageing Yamaha A1 or such (huge with front flap)

This is on a budget, so I am thinking of a big driver and a subwoofer plate amp (or a bridged budget PA amp and passive crossover/filter), money is tight so good bang for buck, with the possibility of future upgrading may be beneficial.

I have been advised a Precision Devices PD-186 18" 97db sensitivity 4ohm 600w bass driver may be a good choice, and was thinking of adding a 500w (4ohm) subwoofer plate amp from Wilmslow Audio.

If the above driver and amp are good starting points, I guess the next step is what sort and size of enclosure? Any advice on these choices and my options?

I have plenty of cabinet materials, 1" chipboard, 18mm MDF, 2"+2" batton, screws and dampening, it will be fitted to castors and size is not really an issue in a large warehouse with double doors to the listening area. I guess a simple to construct large not too complex cabinet with cross bracing and no time spent on aesthetics may be in order.

What I would like is clean and even powerfull bass with decent LF extension around the 20Hz area, sensitive enough to provide a reasonable match to the 103db sensitivity Cerwin Vega's, and teh parts have to be easily to purchase within the UK.

I would also like to get this done before the end of the month as the current sub (a small Kef item) will probably die soon if my collegue has his way.

Any opinions or ideas on which direction a newbie should take?

On a side note, a couple of guys have offered me car audio sub woofers, one of them a 12" Fusion item in a large carpeted box with green trim, and some have said adding a plate amp to such may suffice?

Thanks,
Steve
 
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#27 ·
The basic parameters are in your other thread, there are enough specs to model the sub.
Car audio recommendations have nothing to do with HT subs, they are different animals.
A rumble filter can be added by an outboard unit like the Reckhorn B1.
You can figure out cabinet dimensions from the calculator here:

http://www.hometheatershack.com/forums/enclosure-volume-calculator/

Green is ported, yellow is sealed. Ported is 7 cu.ft. for one sub, tuned to 25 hz. Double the volume for 2 subs.

Text Line Slope Technology Parallel
 
#28 ·
Not quite sure if its me being a numpty, but I have no idea what I am doing with the Parameters and WinISD?

Where do I put sensitivity and power handling etc, I seem to have mine set up for litres not cubic ft too LOL...

Earlier I had played with the GTX 15 figures and noticed the graph looking good with a 600 litre cab with a 23.43 tuning? (the original cab was 491.53)

Need to work out this WinISD stuff, though I think its got an issue with Windows 7
 
#29 ·
#30 · (Edited)
Ok,

I have decided to spend up to or around £400 for this first project, now just looking for a bit of opinion on what I am better buying?

Am I better getting a Behringer EP4000 amplifier, as it looks reasonable for the money and is used by some in here, which seems like good credentials, or the BK 500w into 4ohm subwoofer amp mentioned above?. I will have to leave the rumble filter until later/next month (no idea whats available in the UK).

These are my current options of low cost subwoofer drivers, all car audio,

JBL GT5-15, 15" 1500w subwoofer driver £49.95
JBL GTO1502D 15" 1200W subwoofer driver £54.99
JBL GT4-15 15" 1000w Subwoofer driver £54.72

Well they are the cheapest prices for 15" drivers I could find.
The Eminence, PD and Fane models are all between £130 to £200, I can get two 18" Kilomaxes for £350, and a Vibe Black Death subwoofer (the off the shelf ported box item) for £400.

I am unsure if I am better off with two seperate 15" subs or a single sub with two 15" drivers?

Tonight the amp and drivers, tommorow working out the cabinet! (I guess :daydream:)
 
#33 ·
:no: Well I cannot seem to get WinISD to save the parameters of the JBL GT5-15 driver, even though I have loaded the stated TS parameters I get a "Parameter Error list" for Qts, Qms, Qes and the help button does not work.

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

For £70 the JBL GT)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

I am still looking around to see what drivers are available, UK seems pretty poor for choice. Still can't decide on a couple of cheaper car 15" drivers such as the above, or a pro 18" driver?
 
#35 · (Edited)
Got it working, had to let WinISD do automatic correction for Qts.

The JBL GTO1514 initially looks pretty even in a 300L box with a tuning freq of 20.3Hz, port length is 4.86" and 4.02 diameter with 1st resonance at 1392.06 Hz?

Having some trouble with the GT5-15 parameters still.... Edit, seems to be working, shows a slightly deviated response with more extension?

Most of the 18" pro audio drivers seem to have the max spl, but the JBL's seem to have more SPL at the lower octaves? This would seem to indicate EQ'ing a large 18" PA driver would be of not much benefit?

It looks like a single 15" JBL 320 litre cab will give me 113db at 20hz and 114db at 40hz, two 15" JBL 640 litre cab will give me 119db and 120db at the same frequencies? Does that sound right?
 
#36 ·
The JBL GTO1514 initially looks pretty even in a 300L box with a tuning freq of 20.3Hz, port length is 4.86" and 4.02 diameter with 1st resonance at 1392.06 Hz?
Model the input power to reach Xmax with the appropriate high pass filter. Then check the port air speed, increase the diameter of the port until the air speed is in the 26 -28 m/s range.
 
#38 · (Edited)
Quote; Model the input power to reach Xmax with the appropriate high pass filter. Then check the port air speed, increase the diameter of the port until the air speed is in the 26 -28 m/s range.


Any tips on what sort of filter settings I should be playing with?

What box alignment should I be looking at?

I guess I should input power at the signal box? If so doing so shows a massive increase in cone excursion at 28.41hz of 0.557 and then it drops off to 0.251 at around 20hz then shoots up way over the red line.

I guess it has to stay under that line, but so far when playing with port velocity and width to get the speed correct it seems I lose the LF?

Edit you put some details in as I posted, so I should model the high pass filter around the area where cone excursion reaches it's limits? When modeling with two drivers I am doubling cabinet volume and doubling power input?, but port velocity and lengths seem pretty big?
 
#42 · (Edited)
I must be doing something wrong ! four 5" by 40" ports seems wrong for a single 15?

What port requirement are you getting with the single GT5-15 in the 10 Cu-ft enclosure?

And this may be a bit of a newbie thing to ask, will two single 10 cu-ft enclosures achieve the same spl and LF results as the two 15" drivers in a 20cu-ft enclosure?

(And I thought it would be as simple as getting a nice 18" pro driver and building a copy of a JBL 4645C cinema subwoofer)

May I also ask, is using something like a Behringer DEQ 2496 worthwhile (or any of their active crossovers)?

What 18" pro drivers would be a close match to the JBL drivers used in their Cinema subs if I wanted to build a DIY copy?

JBL Cinema 18" subwoofer parameters,

Nominal Diameter: 460 mm (18”)
Rated Impedance: 8 ohms
Power Capacity1: 800 watts
Sensitivity 2 99 dB, lW, 1 m (3.3 ft)
Frequency Range3 25 Hz - 1.6 kHz
Power Compression4
d -10 dB power (80 W): 0.6 dB
@ -3 dB power (400W): 2 dB
@ rated power (800 W): 3.3 dB
Distortion5
2nd harmonic: <1.0%
3rd harmonic: <1.0%
Highest Recommended Crossover: 1 kHz
Recommended Enclosure volume: 140 - 340 1 (5 - 12 ft3)
Effective Piston diameter: 397 mm (15.6 in)
Maximum Excursion
Before Damage (peak to peak): 50 mm (2 in)
Minimum Impedance: 6.6 ohms
Voice Coil Diameter: 100 mm (4 in)
Voice Coil Material: Edgewound Aluminum Ribbon
Voice Coil Winding Depth: 25 mm (1 in)
Magnetic Gap Depth: 12.7 mm (0.5 in)
Magnetic Assembly Weight: 10.4 kg (23 lb)
Bl factor: 23.7 newton/ampere
Effective Moving Mass: 158 g
Polarity: EIA (Positive voltage to RED
terminal gives forward cone
motion)
THIELE-SMALL PARAMETERS6:
fs: 35 Hz
Re 4.7 ohms
Qts: 0.28
Qms: 5
Qes: 0.29
Vas: 283 1 (10 ft3)
SD: 0.124 m2 (192 in2)
Xmax: 9 mm (0.35 in)
VD: 1114 cm3 (GS in3)
Le: 1.25 mH
710 (half-space): 4%
Pe (Max)1: 800 W, continuous pink noise
MOUNTING INFORMATION:
Overall Diameter: 464 mm (18.27 in)
Bolt Circle Diameter: 441 mm (17.38)
Baffle Cutout Diameter
Front Mount: 427 mm (16.81 in)
Rear Mount: 428 mm (16.85 in)
Denth7: 203 mm (8 in)
Volume Displaced by Driver: 9 1 (0.32 ft3)
 
#44 ·
Steve,

Can you afford 4 of the JBL GT5 15"s and the EP2500 or EP4000 amplifier? This would be a potent and fairly sensitive system.

If you are only going to get 2 15's just get the plate amp as you will not be close to needing the power of the EP amps. Actually 2 of the pro audio 18's would be better than 2 of the cheap car audio 15's. I would take 4 of the car 15's over 2 of the pro 18's though. After you decide what to purchase we can help you out with the details of the enclosure.
 
#45 ·
Well I still have no idea what I really want to do.


The Car audio JBL's I keep having niggling doubts about, I think that's why I again looked at the JBL Cinema sub, though it looks like it may need EQ with the likes of some Behringer kit.

Of course this brings me back to Pro audio type 18"ers, which would probably need EQ. I have found a UK company which sells many drivers, the P Audio drivers look good value (one looks like it may be a suitable alternative to a JBL 2242 bass driver?) http://www.proaudioparts.co.uk/products.asp

The JBL cinema single 18" subwoofer box design looks like the sort of box I had in mind, maybe a single to start, and adding a second later?

I still like the plate amp, but I can get an EP4000 for £300 which makes a 500w 4ohm single channel of amplification for £230 seem a bit of a side step/waste?

Is there an active Behringer crossover or DEQ unit you guys recommend that would take care of low and high filters and maybe even some EQ?

Sorry about all this to'ing and fro'ing :daydream:

Steve
 
#46 ·
My TS parameters for the GT5-15 must be wrong or I am doing something wrong with WinISD? , with a 10 cu-ft cab tuned to 18hz with a HP at 16hz, two 4" by 18" ports, I am getting rear port air velocity of 79.995 ft/s peak at 16.24hz :scratch:

JBL GTO 1502D's have appeared on ebay second hand, but these seem to produce poorer results (TS parameters seem to be within WinISD).

Those P Audio drivers look reasonable....

Decissions decissions............
 
#47 ·
Decisions decisions...
That's easy, go with the GT5.

I am getting rear port air velocity of 79.995 ft/s peak at 16.24hz
That's about right. Right click on anywhere on the graph, select options. At the bottom is the "Air velocity". Click on "ft/s" until it changes to "m/s". Click on "OK".
 
#49 ·
Basically, the alignments are different box sizes and tunings. How the sub will perform is different in each. The goal for a HT application is to find the best box size and tuning that will give you the best low end extension for a given sub. The bigger the box and lower the tuning gives more low end extension at the expense of overall SPL. The smaller the box and higher the tuning gives greater SPL at the expense of low end output. You want the best balance of low end output and SPL.

Rear port gain is how much output the port is contributing.
 
#50 · (Edited)
OK update time,

I bought three JBL GTO 1502D 15" bass drivers, for a total of £70 . I am awaiting another one from an ebay seller (but this deal looks like it may be going sour, I was the only bidder, 99p with £10 delivery, but he is not responding :waiting:)

Anyway I guess this is it, do I build one per cab or a cab with two and build another later when I get another driver?

Will two single cabs side by side go as low and as loud as a dual 15?

I am still having PC problems, and WinISD seems to be showing a wild dip in SPL before 20hz or so? So what options are recommended?

Cheers,
Steve

The only TS Parameters I could find for this driver. (Can anyone confirm these or show their results with WinISD :sad:)

DIAMETER: 15" (381MM)
SENSITIVITY (2.83 V @ 1 M): 93 dB
POWER HANDLING: 300 WRMS 1200 W PEAK
FREQUENCY RESPONSE: 23 ~ 400 HZ
NOMINAL IMPEDANCE: 1 or 4 OHMS
VOICE-COIL DIAMETER: 2.0" (51.0 MM)

DIMENSIONS: mounting depth 5-5/8" (143 mm), cutout diameter 13-7/16" (341mm), outer diameter 15-1/16" (383mm)

VOICE COIL DC RESISTANCE: REVC (OHMS) . . . . . . 0.96
VOICE COIL INDUCTANCE @ 1 KHZ: LEVC (MH) . . . . . . . 0.50
DRIVER RADIATING AREA: SD (IN2) . . . . . . . 132.53
SD (M2) . . . . . . . 855.00
MOTOR FORCE FACTOR: BL (TM) . . . . . . . . 8.20
COMPLIANCE VOLUME: VAS (FT3) . . . . . . . . 6.04
VAS (LITERS) . . . . 171.00
SUSPENSION COMPLIANCE: CMS (μM/N) . . . . 164.70
MOVING MASS, AIR LOAD: MMS (GRAMS). . . . 246.90
MOVING MASS, DIAPHRAGM: MMD (GRAMS) . . . 232.50
FREE-AIR RESONANCE: FS (HZ) . . . . . . . . 25.00
MECHANICAL Q: QMS . . . . . . . . . . . 6.08
ELECTRICAL Q: QES . . . . . . . . . . . 0.55
TOTAL Q: QTS . . . . . . . . . . . . 0.51
MAGNETIC-GAP HEIGHT: HAG (IN) . . . . . . . . 3/8
HAG (MM) . . . . . . . . 9.00
VOICE-COIL HEIGHT: HVC (IN) . . . . . . . . . 1.00
HVC (MM) . . . . . . . . . . 26
MAXIMUM EXCURSION: XMAX (IN) . . . . . . . 5/16
XMAX (MM) . . . . . . . 8.50

Edit, I have to say I am getting rather poor results with the above parameters, even when following JBL's enclosure design for this driver in a twin ported 96litre box it's conflicting?
 
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