Quick Question on Ohms and compatibility.

[Camaican]

Hi all, speaker resistance and power raitings of amps have always been something i am never rock solid on, i should really know more!

I have 2 big JBL JRX125's. they run the following spex.
Nominal Impedance : 4 ohms
Recommended Amplifier Power : 500 W to 1000 W into 4 ohms

I currently run these with a QSC GX5 amplifier and have never had an issue. they were sold as a package, so i assumed they were paired appropriately.
QSC settings...
8 ohms/1 kHz (both channels driven) 500 W
4 ohms/1 kHz (both channels driven) 700 W <-- i believe this is the setting the system is operation at.

My question is, will these speakers be a good pair if used with a
Behringer EUROPOWER PMP4000? This is a mixer that also has an amp built in.EUROPOWER PMP4000 Output Power
RMS @ 1% THD, both channels driven:
8? per channel: 300W
4? per channel: 600W
RMS @ 1% THD, bridged mode: 8? 1200W
Peak Power, both channels driven:
8? per channel: 400W
4? per channel: 800W
Peak Power, bridged mode: 8? 1600W

Please let me know your advice, and how you concluded it.
THANK YOU IN ADVANCE! cheers.hyeah:

 

[afj]

youre amplifier must match the ohm specifications of your speakers. your speakers are 4 ohms. some amps are compatible with different levels of ohms, as is both the ones you have listed above. from the specifications listed, they both will be compatible with the speakers. which is of better SQ only you will be able to tell

 

[jagdish_p]

The GX5 is rated at 700 w for both channels driven for 4ohm speakers with a distortion levels of less then 0.05 %.

The behringer's main function seems to be mixing and equalising in an orchestra and not as an amplifier. The rating of 600 w is at at total harmonic distortion of 1% THD which is very high distortion. I am not sure but a comparable wattage figure for 0.05% distortion will be much lower then 600w.

My recommendation the Behringer europower pmp4000 is not a match for GX5 for the amplification function.

 

[Hari Iyer]

Technically speaking, impedance is a function of frequency and it varies along with the frequency. When you look at the frequency domain curves of the speaker system you will notice the impedance varying vis-a-vis frequency. As music signals are complex and contain a range of frequency the nomial impedance at 1KHz could some time be mis-leading. You would probably need to know the minimum impedance of the speaker and at what frequency the impedance is minimum. Also depending upon the box loading the impedance at resonance could be as high as 20 ohm to 30 ohm for a sealed enclosure. For a vented enclosure there are dual peaks of 20 ohms to 30 ohms one for the woofer resonance and other for the box tuning freq resonance. Only in a speaker box with TL loading the impedance at resonance will be only 40% of that in a vented enclosure at the line tuning frequency.
Designers usually do a upward taper of the frequencies from 200 Hz to around 5KHz and then try and retain a flat impedance after 5KHz to preserve the energy response at high frequencies. The taper from 200Hz is required for increasing the mid-bass response which other wise will be lacking in practical listening rooms due to diffraction and other parameters of the room.