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New budget sub. Single 21" or dual 15?

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Tim Weaver:
I need a pair of subs for a small bar/tent rig. I will be building them due to the need for trailer pack and height needed for the tops. I am looking at a pair of eighteen sound 21LW1400's that are cheap right now. Using 1 per enclosure. The other choice would be a dual 15 probably using Kappalite 3015LF's two per enclosure.

My other consideration is that I want these to be efficient because it won't get a ton of power. Probably a CE4000 for right now. This rig will be limited to available power on site. No tie ins.

Has anybody used the 21 in a standard vented cab? Thoughts? Which would you choose and why?


Tim Weaver:
Just thought I would add that the goal for this is to have something to set the tops on that a rookie soundguy might not destroy within ten minutes. I want to add some low end to the rig, but ultimately I don't really care how low these things go, just how loud can I get the full system on a 15 amp circuit.

My original thought was to use some dual EVM18b cabinets in a double sized TL505 cab. Doesn't handle a lot of power, but they get loud enough on 400 watts, and actually don't sound bad doing it. I abandoned this idea however when I thought of some intern running this rig and killing those poor old 18's. Recones would cost me a fortune!

Tim Weaver:
I have rolled the dice it seems. I won an auction for a pair of eighteen sound 21" woofs for 500 dollars. If everything goes to plan I should have a very decent and bullet proof set of subs for short money.

The best part is my buddy just bought a CNC router and wants a project to learn with!  8)

Loren Jones:
Hi Tim,

You may remember an extensive discussion about this topic when I was building some subs for my church.  I was looking at a pair of dual 15's and ended up building a pair of single 21's using RCF drivers.  Phillip Graham provided the enclosure design very graciously.  I have to say I am extremely pleased with them.  Incidentally I have powered them to date with a Crown CE 4000.  A single one of these 21" vented cabs easily handles everything that bridged CE 4000 will give into 8 ohms. 

I have compared them to quality commercial double 15" cabs (EAW SB600 and SB625).  The 21's have much better extension (30 to 35 hz vs 45 to 50hz) that is easily very noticeable.  The overall output of the pair of 21's I would say is pretty similar to the three EAW double 15's, but that is just based on subjective measurements.

Here is a link to  my post about my build.  The second link is to the thread discussing dual 15's vs single 21's.  Phillip is of the opinion that a good 21" driver (such as the RCF I used or I assume the 18 Sound you are using is similar) in a well designed vented cab should be pretty close in overall output to a good quality commercial double 18".  I hope to do some more comparing of these to some SRX728's.  Here is the link.

If you are anywhere close by you would be welcome to come check them out.  Good luck with your build and keep us posted.

Loren Jones

Tim Talbot:
Have you looked at the b&c 21" drivers ? They also give plans out on there site :)


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