Driver Cabinets

[wisper6419]

I am sorry to do this to you, but I believe I went thru all the post and did not find what I'm about to ask. I am very new to the sound thing and would like to know, What is the difference between a bass cab and a sub woofer for the p.a.? Can you use p.a. speakers for your rig? Why (or why not) use an 18', 15's, two or four 12's, four or eight 10's. I can get hold of an 18" but the cab looks like $#!%. Or I can get an new 18 or 2- 18 p.a. cheaper then a bass cab. Are these okay for building a good (great) sounding rig? Or am I just a "guy" thinking bigger is lower? Does it have to do with the way the cabinet is built? The drivers used, The material of the cones? Ported or not? Can I use the rig from "Back to The Future" with the 82" driver?

[M0ses]

A subwoofer is designed to be good at producing tons of low fequencies. A bass cab, on the other hand, needs to be able to produce a huge range of frequencies. So a subwoofer alone would mean really muddy, tone-less bass.

Specific design elements are extremely variable, but very scientific.

[OtterOnBass]

Bass cabinets are full range speakers (though they have heavily "colored" sound and big gaps where basses don't usually play.)

Subwoofers only play the low frequencies.

You can play bass through PA speakers, though it won't have the color bass cabinets does. Dispersion is a key element - large speaker cones have poor dispersion, so the sound will not spread out for a big audience.

[KeithAlanK]

The goal for PA subs is lots of lows, period. Bass guitar is much more than just lows.
The goal for a bass cabinet is full-range sound that can handle lows without crapping-out.

PA Subs need a crossover to protect them from frequencies above that which they are designed to handle, so to hear your instrument correctly you would need the matching mid-high cabinet and another power amp.
Now, you're playing bass through half of a PA system.
Might as well just buy the other half for the band and then a proper bass amp for yourself.

Instead of $300-1200 you've spent $4000 to get halfway there, + a mixer, compressors, snake, mics, efx, etc, and you're shopping for a cheap truck and trailer on Craig'sList.

[wisper6419]

Soooo, It's really just the crossover then? I been looking at just raw speakers and they are pretty much the same. So buy a cheaper p.a. cabinet and take out the crossover. Why does a bass cab cost twice what a p.a. cab cost when the p.a. has more to it? Just because it says Peavy or Fender on it?

[Zooberwerx]

Originally Posted by wisper6419

Soooo, It's really just the crossover then? I been looking at just raw speakers and they are pretty much the same. So buy a cheaper p.a. cabinet and take out the crossover. Why does a bass cab cost twice what a p.a. cab cost when the p.a. has more to it? Just because it says Peavy or Fender on it?

Why tear out the crossover? 2 and 3 way PA & bass enclosures have some type of crossover or else they wouldn't work. A handful of TBer's use the Carvin LS 1503 PA speaker as a bass enclosure...and its a 3 way. You can probably pick one up used for well under $200.

Riis

[mid_life_crisis]

Originally Posted by wisper6419

Soooo, It's really just the crossover then? I been looking at just raw speakers and they are pretty much the same. So buy a cheaper p.a. cabinet and take out the crossover. Why does a bass cab cost twice what a p.a. cab cost when the p.a. has more to it? Just because it says Peavy or Fender on it?

You are mixing up PA speakers with PA subwoofers.
A full range PA system reproduces the entire tonal range.
A PA subwoofer only produces the bottom end.
If there is a crossover in a subwoofer, it is there for one of two purposes.
1) To stop the high frequencies from being reproduced. This is not to protect the subwoofer, higher frequencies are not going to hurt it, they just either can't be reproduced or they sound like cr@p when they are.
2) To prevent extremely low frequencies below those the sub is designed to reproduce from going through because those can damage the speaker.
A proper bass cabinet is about the equivalent of a PA with no tweeters. It produces what are considered to be subwoofer frequencies all the way up into the lower end of the midrange. They just don't need to reproduce high frequencies, so they don't.
A PA system on the other hand might have to produce everything from the lowest bass notes to the brightest, most delicate sounds something like a flute can produce and everything in between.
A PA sub is just one piece of a proper PA system. You would still need full range speakers to cross in for everything above the subwoofer frequencies. It is possible to buy speakers that do not need the reinforcement of a subwoofer, but they aren't cheap.

[Petebass]

Originally Posted by wisper6419

Why does a bass cab cost twice what a p.a. cab cost when the p.a. has more to it? Just because it says Peavy or Fender on it?

That's quite a big generalisation. The thing about PA skeakers, just like bass speakers, is that some are cheap and some are not. High end PA cabinets are actually a lot more expensive than high end bass cabs.

[Stumbo]

Here are a few links to check out:
10s v. 12s v. 15s v. 18s
2
4x10 vs. 2x10/1x15
2
Benefits of vertical speaker cabs

1x10's that do the job
Full range cab (Carvin LS1503)
1x15/6.5 custom cab
Big cabs
Low B reproduction/speakers/cab thread
Rig for low F#

EQ primer (all instruments)

~PA/Lighting
First
1 What size?
2
Configuring
DIY monitors
1 Upgrading
2

1What mixer is your band runnin'?
2
QSC K series PA discussion
Microphones

Low cost lighting

Check out more links in my sig. below.

[TimmyP]

PA subs do not need a crossover (low-pass filter) to protect them from frequencies beyond their intended use.

PA subs do not necessarily reproduce the frequency range of the bass less well than bass cabs - most all of which are exceedingly colored.

PA subs - when used at their power extremes, do need a high-pass filter to protect them from frequencies below the tuning frequency of the cabinet. So do bass cabinets - but few bass amps have a high-pass - which is why I see so many bass cabs with collapsed cones.

[KeithAlanK]

Actually, PA subs DO need to be protected from higher frequencies.
Forcing the heavy cone and voice coil to move faster than it's designed for (or physically able to accomplish) will tear it apart.
One part of the cone is still moving forward under it's own inertia while the coil is pulling it back--enough of this and any weak areas in the cone will deform, then the voice coil deforms, rubs the magnet assembly, and poof!
I've seen it happen to newbs, which is why I keep my crossover point below 90hz, although you're probably safe up to 150hz for the usual 18" subs out there.