View Full Version : Tweets/Impedance. . .

03-07-2009, 09:02 PM
So I am looking at tweets on Madisound.com

Some of those that interest me have an 8 ohm impedance. I get impedance to some degree. I know that speakers that are rated 100 watts at 2ohms would do 50 @ 4ohms and 25 @ 8 ohms, etc. At least I think that's right. That's all if the speaker can handle that ohm-load.

Now. . .

If I bought a pair of 8ohm tweets and had an amp that does 100 x 2 @ 4ohms, what would happen? Would I be doing 50 @ 8 ohms or would the speakers be getting a 4ohm load and getting 200 watts RMS? Which piece determines the impedance, the speaker or the amp? Can the speakers/amp handle that? I don't have comps, but have a high-end Eclipse HU (7100) which is very detailed as far as setting frequencies goes. The tweets will have an entire amp dedicated to them. Basically the same for the mids. Both amps have crossovers on them.

So what do people suggest? Should I be looking at 4ohms tweets only or would it work with 8ohm tweets. What tweets would you get if you had $200-$300 to spend on a pair? I was looking at brands like Fostex, Morel, Dynaudio, SEAS, Focal, DLS, and Murata (sp?). Should I be looking at something else?

Thanks for your thoughts. . .


03-07-2009, 09:12 PM
50 watts (approx). the speaker determines the impedance.
but gernally tweeters are much more sensative than mids.. and will require less power.. also depends on where they are positioned. but if oyu use prebuilt passive crossovers.. the crossover point will change.

unless im taking it wrong and you mean it differrently.. and you say both amps have crossovers.. your amp has a 2khz (approx) highpass crossover on it? cause if you're running the tweets active (off their own amp with no passive crossover) its going to be need to be crossed alot higher than what most amps have (200-400hz about) and you're gonna end up blowing something up.

03-07-2009, 09:15 PM
Most amps divide the RMS by 2 as impedance doubles.
I.E 100 RMS @ 4 will most of the time be around 50 RMS @ 8.
Some amplifiers are designed to run more efficiently at a certain impedance. Like, some JBL amps produce more power @ 4 ohm than at 2-ohm. I'm not sure if they produce a formidable amount @ 8-ohm.