Hi. I'm new on this forum, so hello to everybody. I would like to use a pair of old speakers, additionally to the ones I normally use ( JBL ). My amp allows for 4 speakers connection, but I could not find any impedance information on the old speakers, nor positive / negative wiring marks. Does anyone knows how to find out the speakers impedance ? Could I dammage the speakers or the amp if I connect them ( the amp accepts speakers in the range of 4 to 16 ohms ). Jean-Christophe
"You could also bring it to your local Radio Shack and have them test it for you."
OH, MY GOD!!!!! That's really good, Berny. You must think RS still tests vacuum tubes also. Have you been in a RS lately? They might know how to sell you a battery for your cell phone but they are lost beyond that. Just go in and ask the salesperson for a "dual banana plug" and see what response you get.
JCG - Call JBL for some help. Otherwise you are just going to be guessing no matter how you test the speakers on your own. You'll see the meter go up and down and there won't be much you can tell from what you see. The Red post is normally the + connection point. If you do not have a red post, then let us know and we'll tell you how to verify what is + and what is -.
Yes, you can harm your amplifier, and posssibly speakers if you push the volume levels, by connecting speakers which swing too low in impedance. When you are talking to JBL ask not only the nominal impedance of your speakers but also what is the minimum impedance the speaker reaches. This is what you need to know before you hook an additional pair of speakers to an amplifier. Of course, you will need to know the same information about your current speakers before you can make a decision regarding how your amplifier will fair with both sets of speakers running. You should also ask JBL if the speakers draw much current from the amplifier. Most JBL's do not, but do not just assume that is the answer if you want to play it safe with your system.
Thanks Jan, but I see I did not explain me well in the initial post. I don't have any doubt regarding my JBL speakers, they are clearly identified as 8 Ohm impedance and have red and bleck connectors, and I have been using them ( happily )for years my problem is with another pair of speakers I want to connect additionnaly to the JBL. Those other speakers looks good ( I mean medium size, 3 ways , old robust construction ) but have no brand name, no impedance marks, and no red or black connectors ( a pair of speakers cables is directly coming out of the back of the speakers but the two cables are identical ). I believe those speakers were part of a integrated mini system. You said "If you do not have a red post, then let us know and we'll tell you how to verify what is + and what is -. ". How ?
Well, I'll let you explain to JCG how that's done in a Radio Shack.
As far as telling which side is + and which -; you have two options. The easiest is with a dry cell battery as you would use in a portable radio or flashlight. With the grill covers off the speakers, touch one side of the cable to the + connection of the battery and the other side to the - terminal. If the driver moves outward, you have correct polarity. If it moves inward, you should reverse the polarity. You can also hook the speakers to a system with a FM tuner. Tune to a stereo station with a single mono voice. I prefer NPR for this as it's easy to get an announcer's voice in stereo. Standing in front of the speakers, the announcer's voice should be focused in the center of the two speakers. If so, the speakers are connected "in phase". If the sound is difuse and seems to have no focal point, the speakers are "out of phase" and the connections should be reversed. Check the wires carefully and you'll probably find something as a designator for + and -. Look for a thin white stripe on one side or strip back a bit of insulation and you might find a thin thread running on one side only.
You should understand that a "nominal" 8 Ohm speaker does not remain 8 Ohms at all frequencies. It can rise and fall to levels that make it difficult for an amplifier to drive. So though your JBL's are 8 Ohm, they might dip into the 4 Ohm range at some frequencies. This would make it difficult to pair them with another set of speakers. If you have no idea what the other speakers are, you can hook them up and try them at low volumes. Increase the volume slowly until you feel confident the amplifier can deal with both pair or will shut down.
Gary Forrest
Unregistered guest
Posted on
I have a Panosonic SC HT920 home theater sound system. I want to put in ceiling rear speakers. Does anyone have a suggestion on what to use? The ones that came with system are 4 ohm 70 watt.