So in a nut shell you are saying get the best biggest speakers that I can find correct?
No, not exactly. They will almost certainly be big, but you are not getting them because they are big. You want something that is very efficient, and can play loud. Little speakers typically are not terribly efficient, but being big does not automatically make the speaker efficient or capable of playing loud.
Usually (though not always), you will be better off with horn tweeters for high volume with a low price, and with large woofers (think at least 12", but probably 15"). But you are not wanting them because they have horns and large woofers; you are wanting something that is efficient and can produce a lot of bass. So the best choice might not be the biggest you can afford, but it will almost certainly be big.
I recommend looking for efficiency of at least 95 dB @ 1 meter @ 1 watt. A higher efficiency, such as 100 dB @ 1 meter @ 1 watt would be better, if all else is equal. And there are speakers that are even more efficient than that.
The reason for the interest in efficiency is that to get the same volume level from two speakers, if one is 90 dB @ 1 meter @ 1 watt, and the other is 100 dB @ 1 meter @ 1 watt, it will take 10 times the power to get the same volume from the less efficient speaker (90 dB @ 1 M @ 1 W) as you would get from the more efficient speaker (100 dB @ 1 M @ 1 W). It takes 10 times the power to raise the volume 10 dB. So with a speaker that is 90 dB @ 1M @ 1W, it will be 100 dB @ 1M @
10W, and 110 dB @ 1M @
100W, and 120 dB @ 1M @
1000W [assuming that the speaker can handle the power, which most cannot handle anywhere near that kind of power; also, there tends to be some "compression" of the sound as one pushes a speaker to its limits, so one will typically not get quite as much volume as the idealized theoretical amount].
As for bass, you will not need the speaker to have the deepest bass; you are looking for loud bass. Very often, professional speakers designed for auditorium use do not go as deep as full range home high fidelity speakers, but they do tend to be able to play the bass that they can reproduce quite loudly. It will probably be best to judge this by hearing the speakers, rather than by going by some number for bass response, but remember this: If you are listening in a room that is much smaller than the one you are going to be using them in, they will typically need to play much louder in the little room than the volume you are wanting in the larger room. So if you go to someone's home to listen to their speakers that they are selling, if their room is an ordinary size, you will probably want the speakers to be able to play so loud that it is painful, while still being clear and undistorted. (Don't listen to them long like that, as you can damage your hearing that way.)
Now as far as a receiver are we talking like a 5.1 surround sound system or just a stereo receiver?
For your application, you probably want just a stereo receiver.
now we have a shelf system that is pushing the speakers that came with them and they are mounted about 7 foot above the floor and wire runs to all four corners of the room. Is there any special way to hook up the four speakers? I am in Central Texas if I am aloud to say that. Thanks again for all the help.
Most stereo receivers have connections for two sets of speakers, an "A" pair and a "B" pair. Just hook up the four speakers to the terminals on the receiver, and select both "A" and "B" to play all four speakers. You will be getting the same sound from both the A and B speakers, though the right and left will still be different with a stereo source, as they should be.
If you are buying two pairs of speakers to use, you probably want to make sure that they are 8 ohms nominally, and that the receiver can handle 4 ohm loads, because two sets of 8 ohm speakers wired in parallel, which is the most common way, and the best way, will present a 4 ohm load to the receiver.
Also, if you are going to use two pairs of speakers, if you want them to be the same loudness as each other, you will want them to be the same efficiency. Most likely, you will want two pairs of identical speakers, but since you are buying used, that might be difficult to obtain. A slight difference in efficiency might be okay, if you do not mind one pair being slightly louder than the other pair. Keep that in mind when deciding which speakers go where. You might want to try them out on the floor before you mount them, just in case someone made an error in their efficiency claims.
Also, if the speakers you buy are efficient enough, you might be able to simply continue using your shelf system. How efficient is efficient enough is something that is impossible for me to say, as I do not know the exact acoustics of your room, and I do not know exactly how loud you want the sound to be.
