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The BK amp does look nice if a bit expensive.

You should probably go with a ported box. You have a large space, a limited budget, sensitive large mains, and a limited amount of power (500w). Sealed subs can be great but they are not efficient, sometimes require EQ and require very large amounts of power and driver excursion to do the low bass right. A ported cab will give you higher efficiency and make better use out of xmax limited drivers and moderate power with the tradeoff of a much bigger enclosure and the need for HPF's.

I noticed a pair of Eminence Kilomax 18's for 350 shipped on UK Ebay. Is this out of your range? There were also some Infinity Reference 12" drivers for about 55 ea and some JBL GT5-12's for about the same. You could get 4 of either of those and wire all of them to 4ohms. A pair of the RE SE15's or the Tempest 15's would be good as well. After you pick some drivers we can help you with the enclosure for them.
 

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Discussion Starter #22
I am going to leave the amp for now, I am now considering a Behringer EP4000 after I build the bass cabs with whatever drivers I end up with, seems popular. And I am now under the impression it will give me more driver choices and such.

I think the AV sub out into a power amp driving a 12" Fusion car sub was promising it seemed to go well, well at least indicate such an implementation may work. I could at least build one or two cabs, use an old amp, and upgrade the amp, then later when I am more experienced evaluate my sub requirement better?

I have found JBL GT4 15" drivers at reasonable cost, two for the same price of a single Eminence Sigma Pro 18"! (though stock is not varified)

Considering this was intended to be "bang for buck" I am wondering how well this driver would do for the basis of my first project? Considering the price I could do a single cab, or get two drivers and build two subs, or build a twin, or four?

Would two wired in parallel in the same cab be preferable to two seperate cabs? Does this increase sensitivity? As they are 4ohm I guess two twin 15 cabs running from the left and right outputs of an EP4000 would be optimum? And that four 15"'s in the same cab would be a waste?

The Yamaha has parallel (IE two) sub outs, one of our other amps (Pioneer) has the ability to run a front and rear sub.

I wonder if a big sealed box would work? Would I need a rumble filter or have to worry about cone excursion with a sealed? JBL seem to recommend sealed as the best option?
 

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How far will the seating be from the subwoofer and where in the room is this movie setup located? I hate to keep sounding like a party pooper, but in a typical home theater we have room gain, boundary gain, and tend not to sit more than 12' from a subwoofer. You won't have any room gain in the range this subwoofer will cover, you may not have any boundary gain depending on where your setup is located in the room, and the further away your seat is from the sub, the more lossy the output. Typical sized home theaters make up for that distance loss with room reflections, but your room is too big for that.

If you go with dual ported subs, can you place them right at the sides, or right behind your seating area?
 

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I second the near placement option steve is talking about. I have a hard to drive room and have found that placing my sub behind my sofa keeps good dynamics and extension. The tactile experience doesn't hurt either.

Other than difficulty in the build, why not just go for one of the tuba subwoofers? The drivers they use are not that expensive and the 36 or 48 looks like it would do that room nicely and not cost that much.
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Discussion Starter #26
Hi guys,

The room layout is a bit of an issue, its a solid concrete floor, but a suspended tile ceiling, walls are of the alloy stud partition with plasterboard and some of that is plywood skimmed. Within the center of that room on the left and right of the listening position, equaly distance at the points the room divides by three, are two large workstation/benches. Kit is brought in and not permanent in it's installation. Me and a collegue put the system together as a cinema away from home, we both have young children and had to make compromises at home. We were able to utilise a large workshop (within a large warehouse) at work under certain conditions.
We have an HD projector with a Sony Blueray player and the big Yamaha, I had picked the Cerwin Vega's due to their sensitivity and the room size, and they work quite well, apart from I feel they roll off around 50-40hz, plus the room is a little reflective and the amp is a little underpowerd.

The speaker placement is equidistant in a full circle around the listening area, with the 30deg and 110deg angles, seen in some diagrams. That seemed to offer the best set of performance and compromise in the room.

I would prefer the sub to be in line with the center/mains for now, the corners are quite a bit farther away than the mains, so it would probably have some sort of compromise.

My reasons for thinking of this 15" JBL is cost (around £70 per driver), I have plenty of 1" chipboard and 2"+2" batton, so now just need to work out an enclosure to stick two of these 15" JBL's in.

It will probably be rather ugly and rough, with plenty of screws and glue, I do not have a table saw so will make do with the basics. I can dress it up later (PA style to match the Cerwins and functionality), and will want to add some sort of metal grill to protect the drivers. If it works out cheap easy and functional, I may build an identical sub with another two 15" JBL's later, running of the left and right outputs of the EP4000. And probably have the pair flanking the centre.

I have also heard the 12" version of this, and it sounded far better than the Fusion 12" high excursion car sub I tried.

I am probably going to get a Behringer EP4000 for the subs, so how would I add a rumble filter to this amp? And would running the subs in series not affect the amplifier dampening capabilities? I am not sure if the JBL manual for the GT4-15 states parallel wireing and sealed cabs as better due to use in cars?

I will still contemplate a more elaborate design later, but think budget first, and build up from there, it should be a good learning experience :bigsmile:

So does anyone have the TS parameters for the JBL GT4-15 sunwoofer? Or suitable cabinet drawings for a cab to house two of these?

And any graphs showing its sealed performance versus ported?

Thankyou,
Steve
 

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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.

JBL.JPG
 

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Discussion Starter #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
 

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Discussion Starter #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:)
 

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Discussion Starter #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 [email protected] 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?
 

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Just enter QES, QMS, FS, RE, VAS, MMS, and XMAX and it should work fine. It likes to auto calculate specs and if it doesn't match with winisd's calculations it won't let it go through.
 

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Discussion Starter #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?
 

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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.
 

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Discussion Starter #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?
 

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Discussion Starter #40
Is the port length show supposed to be divided by the amounts of ports? As if I have two 5" odd ports, 40" length seems a lot?
 
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