I respect that you're knowledgeable about audio, but I think that's a bit of a daft thing to say. Sound manufacturers have been calling speakers that cross over at 100hz or thereabouts "subwoofers" for decades, even if they start rolling off at 60hz. Very few pro sound offerings are designed to be high passed above 30. I don't see a point in campaigning to change that distinction.
OP wants high spl (high sensitivity), in open air (no room gain), on a boat deck (barely 2pi loading). Getting appreciable quantities of low bass in that kind of situation is nearly futile.
Reading his post misplaced in the other thread, I think it's even more clear that sub 40hz isn't what he's after. If your aim is to impress people and/or get them dancing, a high spl 60 hz chest pound is probably a better goal than a barely audible 25hz rumble.
In any case I'd just build the TH18 if I were him and be done with it. It's got great extension and would be monstrously loud for a boat that size. No doubt the loudest boat on whatever lake he occupies.
misposted here: http://www.diyaudio.com/forums/subwoofers/271139-what-do-big-finished-boxes.html#post4255295
Guys - first, thanks for all the thoughts and keep 'em coming!
Second, let me clarify the goals a bit since that seems to be a question: We want bass that can keep up with the 4 pa cabs on dance music - not really house or trance type stuff but top 40, rap, rock, etc. We're also trying to get some projection... My experience is that the bass won't project off of the boat unless you 1) have a ton of hp (many woofers, lots of power) or 2) you can get some sort of boundary gain - guys with go fast boats just put 4 10's in freeair under their back seat and the gain they get from firing them towards that big helm wall in front seems to make a huge difference.
Third, a bit about the location... This is going on a pontoon boat that has an upper deck (see pics below). I've tried several locations on the boat and this one seems to be the best in terms of having the least amount of null spots on the boat and projection. I've tried all sorts of combinations before on our other boat (which does not have an upper deck) - 4 10's sealed, i built a BFM T-39 but had to fire it skyward so it could live in a hatch, 2 12's ported inside of a hatch, etc.). What has worked best is the 2 12's ported and the BFM.
Again, really appreciate the help and I'm ready to make some sawdust!
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OK, I _was_ teasing a bit but HSU has called their subwoofers True Subwoofers because they had extension well below 40 Hz. I'm fully aware that the PA world is different but it is a compromise in my opinion - sure you can get a lot more SPL if you don't try to go lower than 50-60 Hz but it doesn't sound very good if you ask me - I have to have strong output to 40 Hz and lower is better. The OP asked for a solution and I offered my opinion.
Not going to argue any further, he says he has tried many solutions that didn't work, he can try it if he wants and could even try different tunings but I wouldn't go much over 38 Hz.
If you want 40 Hz, then you want a TH18. If you're worried about it being too tall and tipped over into the water, lay it on its side 
If you're running 1000+ watts of audio power on a boat, make sure you have enough battery. Perhaps a backup. Running 800 watts of subbage in my truck results in headlights dimming at highway speed. I doubt there is going to be more alternator available on the boat than in a truck, and swimming it back to shore is no fun.
If you're running 1000+ watts of audio power on a boat, make sure you have enough battery. Perhaps a backup. Running 800 watts of subbage in my truck results in headlights dimming at highway speed. I doubt there is going to be more alternator available on the boat than in a truck, and swimming it back to shore is no fun.
OK, I would do the 28 Hz tuning if it were my system but since there is so much emphasis on smaller and 40 Hz bass here is 7 cu ft tuned to 35. It will easily take 3000W from a displacement standpoint and should easily take 3-6 dB of boost anywhere from 32 to 40 Hz to really pump up the bass that you feel. Normally room gain would help at these frequencies but obviously there is no room so tilting the low end up a bit should help. I'd go with a 6 dB peaked high pass at 35 Hz, but certainly try 40 Hz to see if you like that better, reduce the peaking to something like 3dB if you run into displacement issues - I doubt that you will. And add another 24 dB/oct high pass with say Q=1 Fc = 32 for sharper LF rejection if you plan to push it to the max. I assume that you'll have DSP bass EQ?
3000W takes the SPL off the top of the chart so I only showed 2000W.
I'd use a slot port say along the short side (22") by 4" and try to keep it under 2 ft long, this would add less than 1.5 cu ft to the box. As I said before passive radiators would be better.
He is already running one XLS 1500, I'd probably drive the subs with an XLS 2000 or 2500 and wire the box with two 2 ohm inputs to get the most out of the amp.
You realize that the threshold of pain is about 125 dB and this system will cause severe hearing loss?
http://www.hearnet.com/at_risk/risk_trivia.shtml
It is not as if you are out at a stadium 50 ft away from the box.
3000W takes the SPL off the top of the chart so I only showed 2000W.
I'd use a slot port say along the short side (22") by 4" and try to keep it under 2 ft long, this would add less than 1.5 cu ft to the box. As I said before passive radiators would be better.
He is already running one XLS 1500, I'd probably drive the subs with an XLS 2000 or 2500 and wire the box with two 2 ohm inputs to get the most out of the amp.
You realize that the threshold of pain is about 125 dB and this system will cause severe hearing loss?
http://www.hearnet.com/at_risk/risk_trivia.shtml
It is not as if you are out at a stadium 50 ft away from the box.
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Thanks for this, appreciate it. Here's a question / concern: I have quite a bit of battery and inverter but this is a ton a power requirement... Would it be better to scale up power supply (which is about 70lbs for every battery I add) or go with something like the SS15 that may have an efficiency edge - granted at the price of < 45hz extension?
J
Does the boat have any source of power generation? How much power you're realistically willing to feed the sub and for how long is something you'll want to figure out. If you are pressed to conserve power, efficiency will be pretty important. Every 3db sensitivity will cut your power consumption by half for the same spl.
Depending on the driver, the TH18 is around 99-100db sensitive. SS15 averages somewhere around 102 1w/1m. The ported boxes in this thread will be lower. Theoretically.
If you're running off deep cycle batteries, unless your outings are fairly short I don't think it's feasible to try to draw over a kW for extended periods of time, so sensitivity will be something to focus on, not so much max output at power handling limits.
Exactly... I have three pretty large deep cycle batteries and I have been able to run 12v amps (I know, I know, but these are big name amps that come with a certification of RMS power output) totaling ~2200 W RMS for the better part of a day (say 4 hrs) at full clip before voltage dropped below 12v.
I plan to run about this same wattage +/- 500 watts but now am using the inverter so there's a bit of additional conversion loss - I can live with that and I can add another battery if needed.
So, it sounds like the right compromise might be the SS15 or TH18? If so, i'll dive back into those threads and make a final selection.
Thanks again gang.
That's a value judgement only you can make. I will admit diyaudio has kindof a hard-on for tapped horns as the solution for everything, but I think in this circumstance the sensitivity will be a really big deal both because of your limited power and nearly nonexistent boundary loading.
So at the risk of restating my opinion too many times, I would personally choose between SS15 and TH18. The SS15 being cheap and loud. The TH18 is the more premium option as it's bigger, heavier, more expensive, and not as sensitive but it will go deep and you can really crank it LOUD if you ever wanted to.
Also if you can keep using a 12v class D amp instead of an inverter and then a normal pro amp I think that would be something to aim for. Just make sure you can put a high pass in your signal chain (pretty important) in addition to the low pass. That's probably a feature not a lot of car audio amps have for the subs.
So at the risk of restating my opinion too many times, I would personally choose between SS15 and TH18. The SS15 being cheap and loud. The TH18 is the more premium option as it's bigger, heavier, more expensive, and not as sensitive but it will go deep and you can really crank it LOUD if you ever wanted to.
Also if you can keep using a 12v class D amp instead of an inverter and then a normal pro amp I think that would be something to aim for. Just make sure you can put a high pass in your signal chain (pretty important) in addition to the low pass. That's probably a feature not a lot of car audio amps have for the subs.
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Why not just run the "big name" 12V amps and eliminate another inverter for 120V? At least for the power amps. I really think 2200W RMS will be enough and you say you already have them? Also, you're not going to run sine waves so if you run say 2000W amps I seriously doubt your average power with music will be over 500W.
Also I'd build it as 2 boxes half the size with 2 woofers in each to make them easier to move around.
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I'd love to but the biggest thing you can find in the 12v world, that is not internally crossed over low pass, is a 500 w rms bridged at 4 ohm. I've got such an animal (PUNCH Amplifiers - P500-2 - Rockford Fosgate®) but it runs hot and shuts off after about an hour of running two of my 8 ohm cabs bridged. I also have 4 cabinets I want to run in addition to the sub so the PA amplification world seems to be the only solution.
Oh, if only you could make a water-tight cavity under the floor between the barrels .
Edit: 4 single fold t-tqwt, mouths facing up, exits through the floor.
+1 on using a 12v amplifier(s) too, imo inverting is inefficient, and 12v amplifiers will most likely be smaller, easier to mount / hide, and most importantly, designed with being in a high humidity environment in mind.
.Edit: 4 single fold t-tqwt, mouths facing up, exits through the floor.
+1 on using a 12v amplifier(s) too, imo inverting is inefficient, and 12v amplifiers will most likely be smaller, easier to mount / hide, and most importantly, designed with being in a high humidity environment in mind.
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JL Audio makes some really nice mono amplifiers that offer full range. Edit: Well, up to 8 khz anyway.
Like meow: http://www.jlaudio.com/hd1200-1-car-audio-hd-amplifiers-98250
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Oh, I see, well you could just do the subs on 12V and have one amp per woofer at 4 ohms. I don't really know the auto sound world but I'd think that you could find something and I'd try it with 1 KW total then add another amp if that is not enough.
You are going to have to write in complete and clear sentences if you want a reasonable response. WTH are you talking about?
The OP stated that he has a lot of 12V power so I don't know what you think you are offering here.
Probably trying to steer the OP towards 'marine' electronics - which, unfortunately, are costly for waht you get. Not to mention, most 'marine' amplifiers are absolute junk compare to top-tier auto sound amps. I challenge anyone to find a 'marine' sub amp that actually puts out a kW of real RMS power. And how much would it cost if you can get it - three grand, perhaps?
M1000/5v2 - Marine Audio - Amplifiers - M-Series - JL Audio
600 RMS x1 for sub, 100 x4 everything else.
That's uh...yep, a kW.
Kinda just barely a KW, with an 80 amp fuse it would have to be close to 100 percent efficient to produce 1 kw for anything more than a quick burst even at 14.4V.
It's expensive and you're really just paying for the name.
I don't see anything that qualifies this to be specifically for marine use, it looks like a regular car amp to me.
These following two amps are just a bit over $100 each, they both have 120 amp fuses (40 amp x 3 fuses) and would be perfectly fine on a boat. You really can't get any amp wet so I wouldn't spend the money on something marketed for marine use. If you don't mind going for a "lesser" brand name you can get a ton of 12V power for pocket change these days. The cheaper one has both low and high pass adjustable filters, the other only mentions low pass, but the market is so saturated with this stuff you can find whatever you need cheap. These are both mono sub amps but at this price you can buy 6 of them in case one fails, and still have enough money left over for a few multichannel amps for the higher frequency speakers. I'm pretty sure either of these would put out a lot more measured power than the extremely expensive JL.
Boss AR4000D Monoblock Armor Series Class D Car Amplifier
Planet Audio TRQ1.3000D (trq13000d) 3000W Monoblock Torque Series
These two amps are actually pretty small by today's standards. For a couple hundred more you can get into some real power, but I was just looking for something to compare to the JL.
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