Ok, I looked though the threads and could not find an answer to my question.
I know this is probably a really stupid n00b question, but I cant seem to find any straight answers on the net about it.
What is the difference between car audio subs and PA subs? The only thing I know is that the car audio subs seem to have a much larger excursion then their PA counterparts.
I used to do tons of car audio installs back in the day but now I'm looking at putting some PA cabs together and really would like to know what advantages the PA style subs have over the much cheaper car audio versions.
Also, if anyone could point me at some decent PA subs. I don't need 10 million watt monsters but I'm looking at something like 500 watts RMS 15"s or 18"s
Thanks in advance for any help!
I know this is probably a really stupid n00b question, but I cant seem to find any straight answers on the net about it.
What is the difference between car audio subs and PA subs? The only thing I know is that the car audio subs seem to have a much larger excursion then their PA counterparts.
I used to do tons of car audio installs back in the day but now I'm looking at putting some PA cabs together and really would like to know what advantages the PA style subs have over the much cheaper car audio versions.
Also, if anyone could point me at some decent PA subs. I don't need 10 million watt monsters but I'm looking at something like 500 watts RMS 15"s or 18"s
Thanks in advance for any help!
For spec'ing PA stuff one usually starts with real numbers for a MaxSPL goal. Bass is always the hardest for PAs (hip-hop, reggae, etc) and are usually spec'd about 10 dB hotter than the 1kHz range of your tops. MaxSPL is your peak with average (C-weighted) about 12dB lower to give yourself headroom on the console.
I like 107dB(SPL) average for a live rock band in the "hot zone" where the dancing is just off the stage. Let's say the hot zone is 5 meters from your subs located under the stage. You're doing a center-only horizontal stack under the stage, right?
goal+distance+headroom is your answer: 107dB + 20*log(5) + 12dB = 134 dB(SPL) @ 1 meter = MaxSPL
Most of the energy down there is not around 30Hz, it's around 80Hz for a kick drum. You really don't need to go below 40Hz for live sound. Efficiency is the key factor, not frequency response as you can adjust that externally. There is no such thing as an efficiency knob on any outboard gear. Folded horn subs are about the best way to go, IMO.
Look over www.billfitzmaurice.com and consider building a pair of T48s to run V-coupled.
Some car subs work pretty well in folded horns, but you'd need to do some design homework to find which ones and for what cabinet it's to go in.
I like 107dB(SPL) average for a live rock band in the "hot zone" where the dancing is just off the stage. Let's say the hot zone is 5 meters from your subs located under the stage. You're doing a center-only horizontal stack under the stage, right?
goal+distance+headroom is your answer: 107dB + 20*log(5) + 12dB = 134 dB(SPL) @ 1 meter = MaxSPL
Most of the energy down there is not around 30Hz, it's around 80Hz for a kick drum. You really don't need to go below 40Hz for live sound. Efficiency is the key factor, not frequency response as you can adjust that externally. There is no such thing as an efficiency knob on any outboard gear. Folded horn subs are about the best way to go, IMO.
Look over www.billfitzmaurice.com and consider building a pair of T48s to run V-coupled.
Some car subs work pretty well in folded horns, but you'd need to do some design homework to find which ones and for what cabinet it's to go in.
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Hey thanks for the quick responses!
Im going to do some more research on folded horns. But in the mean time Im still a little confused as to why a PA sub would be better. From what I gather its because car audio subs are designed to play very low while PA subs are designed to play a bit higher/punchier?
Im going to do some more research on folded horns. But in the mean time Im still a little confused as to why a PA sub would be better. From what I gather its because car audio subs are designed to play very low while PA subs are designed to play a bit higher/punchier?
Actually its for a techno/house DJ setup. But im sure the same formula would still apply correct?
PA subs aren't designed to not play low - they're designed for efficiency, ie, getting the most out of your watts. If you look at car audio subs, they generally have low efficiency, compared to PA stuff, the efficiency of which is usually in the mid to high 90s. The fact that they don't play low is something every manufacturer has to balance against how loud it goes.
For the bass, use something fairly cheap, as you'll be kicking yourself if something expensive was to give off the magic smoke.
Chris
For the bass, use something fairly cheap, as you'll be kicking yourself if something expensive was to give off the magic smoke.
Chris
The numbers will be different. I'd say 103 average for discotheque level and a bit less headroom, maybe 10 over and maybe the people will be a bit closer.
103dB(SPL) hotzone target + 20*log(3 meters) + 10dB headroom = 122.5dB(SPL) @ 1 meter
That's easily doable. A single T48 with 225W of drive should do that @ 50 Hz if I'm reading this chart correct for the single cab.
target 122.5dB(SPL) - 99dB(SPL)@50Hz = 23.5dB
antilog(23.5/10) = 223.87W of power gain
I'm guessing that was measured in 1/2 space (open field), so if you put that in a corner you'd need a whole lot less drive to get there.
I'm not saying you should go with a T48. I'm showing you an example.
Ohh... I almost forgot. Consider using a "real" loudspeaker processor for the active crossover such as a DBX DriveRack PA-II or a Behringer DCX2496 as they allow for some nice advanced stuff like time alignment, limiting to protect your speakers, and especially the nice EQ.
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The difference between car audio subs and home audio subs is that they're engineered with different goals in mind.
In car audio everyone wants a box that's small and can handle a lot of power. Due to Hoffman's Iron Law, to get a lot of SPL out of a small sub, you need an outrageous amount of power. Hi power leads to high excursion, and explains why companies like JL Audio offer $800 subwoofers with over 20mm of xmax.
In pro sound the primary goal is sheer output. And again, due to Hoffman's Iron Law, you can trade box size for efficiency. Because prosound woofers are generally designed for enclosures that are an order of magnitude larger than a car audio driver, the drivers themselves have a set of parameters which is "tuned" to large enclosures.
At this point, you might ask yourself, why not use a car audio woofer with high xmax in a prosound application? The answer is that there's no benefit. Due to lower efficiency, you'd end up requiring two or even four enclosures to match the output of a single prosound cabinet.
Or you might ask, why don't prosound woofers have xmax that's as high as car audio woofers? The answer to that one is that they don't need it; they're typically designed for enclosures where the low end is augmented by a port or a horn.
So at low frequencies the cone isn't moving at all. And below that is a steep high pass filter.
Does that make sense?
Also, like all rules, this one is bent all the time. I use prosound drivers in my car audio projects. (I'm running BMS and B&C.) And there are prosound vendors who've used car audio woofers in prosound applications. (google matterhorn)
Based on a lot of work by some others here, that cabinet will work great with some boundary reinforcement. It really likes corner loading. There are other SPL plots out on the web that show the actual groundplane performance of the T36. If you do not have corners or walls to load against, build two cabinets and couple the mouths or build a different enclosure (http://www.diyaudio.com/forums/subwoofers/127908-jbells-set-four-tapped-horns.html).
those bfm subs have one drawback, they aren't very sensitive down low, if you look at that T48 graphic it only starts to get efficient around 60hz.
that comes with the size of the cab, the T48 & T36 are fairly small cabs to really take full advantage of the horn loading, it would be possible to built a flatter design that puts out around 102db/watt/meter but you'll end up with a cab that's close to 600 liters.
the 3015LF kappalite should be a better speaker, it can take more power before it runs out of xmax.
have a look at jbells tapped horn for the 3015LF tread, i built one and it's a very simple design, easy to built, only drawback is the size here.
that comes with the size of the cab, the T48 & T36 are fairly small cabs to really take full advantage of the horn loading, it would be possible to built a flatter design that puts out around 102db/watt/meter but you'll end up with a cab that's close to 600 liters.
the 3015LF kappalite should be a better speaker, it can take more power before it runs out of xmax.
have a look at jbells tapped horn for the 3015LF tread, i built one and it's a very simple design, easy to built, only drawback is the size here.
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The Titan subs don't go all that low no matter how many you stack - the cutoff frequency is higher than the Tubas. The designer firmly believes that nothing below 40 is even required for the application, but in my experience bass extension is what separates those who sound professional from those who don't. One Tuba 36 isn't all that interesting, but when you stack 8 of them, you'll get solid bass down to about 25 Hz, which for a PA, is the bass-ment. Lab horns which I use are the same way - a full size mouth is a stack of 6. To make any real use of them, you've got to have more than one. Four on the floor is approximately the same as one in a corner. Even with horns there's still no getting around Mr. Hoffman's law - it's got to be big to get efficiency and extension. Corner loading can be considered "cheating", but the horn actually extends into the room, and with it, the required distance to the listener/audience. If you count all that space, the iron law still holds. Not to mention that the latency and delay from cabs in the corner means you'll never sync it up with the direct sound from a stage.
Maybe it's just an optical illusion, but the flare rate on those looks like it's expanding way too rapidly to get down in to the 20's. The outer flare looks a bit like the midbass bins I use which have an *80Hz* cutoff. Four of those on the floor is interesting in its own way... tactile vocals.
Well, this single sub is really only going to need to be used for very small events like 20-50 ppl max so I think the 1 sub should be enough. I just don't know if 80hz is going to be low enough, but on the other hand I don't want a huge sub to lug around 
Is there something that is about the same as the Tuba36 that might be a bit lower?
Is there something that is about the same as the Tuba36 that might be a bit lower?
The Tuba36 is considered an "Okay" DIY project. You get $225 worth of sub from it.
You really want lower? TubaHT.. do it! You know you want to!
YouTube - BFM Tuba HT - 121db @ 22.2hz / 10.8v - With unmeasurable distortion using REW
You really want lower? TubaHT.. do it! You know you want to!
YouTube - BFM Tuba HT - 121db @ 22.2hz / 10.8v - With unmeasurable distortion using REW
excellent question:
car subs:
1 - designed to be ugly
2 - designed to be inefficient
3 - designed to NOT work properly in any enclosure, room or cabin
4 - designed to produce maximum distortion
5 - designed to work with car audio amps ( 1 - 2 ohm impedance )
6 - cheap yet overpriced
7 - usually bought by people who know as much about physics as i do about ballet
PA subs:
1 - neutral looks
2 - extremely efficient
3 - designed for moderately sized vented enclosures
4 - designed to produce a relatively low amount of distortion
5 - designed to work with PA amps ( 8 ohm impedance )
6 - expensive yet worth it
7 - usually bought by people who have years of experience in the field
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As well as the characteristics already enumerated above, I've noticed that many modern design car audio subs have one common design factor: When mounted in the recommended enclosures as determined by box modeller programs, they tend to reach xmax at about max rated power. I don't think this is accidental. It's likely to be a deliberate design point to reduce the number of warranty returns and general driver damage caused by people "who know as much about physics as I do about ballet". I noticed this with several different low-end models of Pioneer and Fusion drivers, and especially with the Jaycar CS2344 drivers I bought on close-out recently. For both sealed and vented enclosures of optimum tuning, they reach xmax at about max rated power. (I used Unibox for this, it conveniently overlays the Xmax-limited SPL line on the SPL graph.)
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