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Old 17th November 2009, 05:30 PM   #11
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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.

Last edited by polviggen; 17th November 2009 at 05:33 PM.
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Old 17th November 2009, 06:45 PM   #12
wg_ski is offline wg_ski  United States
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Quote:
Originally Posted by polviggen View Post
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.
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.
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Old 17th November 2009, 07:05 PM   #13
jbell is offline jbell  United States
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...... and sometimes 4 on the floor isn't even all that interesting... even with the covers off to boost 40-60hz..

Although, it was the revelation that covers off was louder, that made me investigate Tapped Horn's... so I guess that was a blessing in disguise.
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Old 17th November 2009, 07:25 PM   #14
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a reference for Hoffman's Iron Law.
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Old 17th November 2009, 11:01 PM   #15
wg_ski is offline wg_ski  United States
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Originally Posted by jbell View Post
...... and sometimes 4 on the floor isn't even all that interesting... even with the covers off to boost 40-60hz..

Although, it was the revelation that covers off was louder, that made me investigate Tapped Horn's... so I guess that was a blessing in disguise.

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.
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Old 17th November 2009, 11:04 PM   #16
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that are some really wide T36's I believe ?
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Old 18th November 2009, 05:44 AM   #17
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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?
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Old 18th November 2009, 06:41 AM   #18
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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
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Old 18th November 2009, 08:09 AM   #19
Borat is offline Borat  United States
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Originally Posted by jason51873 View Post
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!
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

Last edited by Borat; 18th November 2009 at 08:11 AM.
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Old 18th November 2009, 09:36 AM   #20
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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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