linear impedance....

[admin_exported]

well thats what my new speakers , dynaudio dm 2/7 (getting them thursday) are described as having..

they are 4 ohm so afaiui they will take more from the amp, but are said to be an easy load because of their linear impedence.. can anyone explain this?

ta..

 

[Anonymous]

Impedance as rated on a loudspeaker is only a nominal value. Speaker impedance actually varies slightly with the frequency it's fed. Let's assume the speaker has a tweeter that is 16 ohms and a mid/bass driver that is 8ohms (exaggerated example). If a sound that's fed to the speaker only needs the tweeter to produce it fully the speaker is effectively 16ohms. And if the bass driver is producing he whole sound it's an 8 ohm speaker. Obviously most music uses both tweeter and woofers alike. But it gives a speaker a constantly varying impedance. Speaker impedance is also affected by the drivers inertia at any given point and that in tern by cabinet resonance and even temperature. Sometimes more than you,d think. Manufacturers often use this to make a speaker "tuned" to respond to certain frequencies. Obviously this could cause a sudden pull of current on an unsuspecting amplifier and trigger it's protection circuitry or even for it to fail.

Linear impedance speakers are designed to minimise the varying impedance to a minimum. The idea is that impedance is the same regardless of frequency. In fairness there's never perfect linear performance but it's often a big difference to the conventional design. This achieved in both driver choice and crossover design. Amplifiers have a more stable load to drive Witch requires less current on the whole across the frequency range with fewer sudden changes.

Your 4ohm speakers are quite current hungry but are safer to drive from an amplifier than a conventional speaker design. A conventional speakers impedance could from as low as 2ohms and cause an amp to fail.

 

[Anonymous]

Some speakers are tuned in such a way that the impedance at certainly frequencies is very different to other frequencies. For example, a bass reflex's port frequency will often impact the impedance at said frequency. I'm no expert but I've also read that some speakers are tuned to have bass humps that effectively draw greater current from the amp due to a spike-drop in impedance. In other words, the boost in bass isn't 'free' when it comes to driving it. Where a speaker's impedance is linear then you don't have any nasties that will make specific demands on the amp's current driving ability.

 

[Anonymous]

thanks guys, thats made things a bit clearer, cant say i fully understand though..

on another note, ive often read on here that the power rating of an amp, ie 85 watts in the case of my as-500, is not an indication of the power of its current, is there a way too find that out on a stereo amp? how powerful the current is?

 

[Anonymous]

The problem is, max, that it all depends under which conditions you measure an amp's power and current output. I wouldn't lose any sleep over it...

 

[Anonymous]

cheers iggle, i was just curious really.. rick of musicraft has been running the dynaudio dm 2/7-as-500 combo for a while and he's very impressed by the pairing..

i just have to wait till thursday now (speaker delivery date) and ill hear it for myself

 

[Anonymous]

I'm sure someone more knowledgeable could answer the q for you.

I hope you enjoy the speakers, max, Dynaudio are very good at producing them!

 

[Anonymous]

igglebert:I'm sure someone more knowledgeable could answer the q for you.

I hope you enjoy the speakers, max, Dynaudio are very good at producing them!