Audio Systems: Speaker box, speaker impedence, output impedence

Question
Thanks for the previous answer
i have another questions.How can i measure the required output impedence of the stereo?i have a multimeter, would that help?
and what would happen if i plug the speakers without an amp?

-------------------------
Followup To
Question -
Hi,
I have 2 questions.

i have 2 JDLX 8" 300w/4ohms Subwoofers Speakers , and i was wondering if i can make a good speaker box, or at least a decent one,out of a PVC pipe. My idea was to put the 2 speakers at the the two ends of the pipe,facing out.or use one pipe for each speakers.The pipe would be filled out with foam.

my car stereo is a pionner 35x4, and its written on the 2way Crossovers(cause this subwoofers came with 2 tweeters too) that i need an amplifier.I want to know if its really necesary to use an amp to plug the 2 subwoofers to my radio?.and what would happen if i plugin the 2 speakers without an amp?
Answer -
Hello Alejandro,
Make sure that the speaker impedence is the same as the required output impedence of the stereo. As for the speakers being rated at 300 watts and the output power of the stereo is 35 watts max, you will need an amplifier to properly drive the speakers. You could use the PVC pipe for a speaker enclosure as long as you mount the speaker with rubber caulk and use a good fitting foam to prevent any vibration. You may also want to shop around on the WWW for speaker enclosures that may suit your needs.

TOM,
T&D ELECTRONICS

Answer
Hello again Alejandro,
First, the stereo should say on the sticker what the output impedence is or you will find this in the owners book under specifications. Second, you can connect your speakers directly to your stereo output as long as the impedence of the two match up. However in order to drive the speakers efficiently, the minimum output power of any stereo or amp should be at least 50 percent of the power rating of the speakers. In this case the output power of your stereo should be about 150 watts. With the output power of your stereo only being 35 watts it will drive the speakers, but not strong enought to make them work and sound the way they should.

TOM,
T&D ELECTRONICS
tdeser@zoominternet.net