Jargon

[Amadeus1756]

Could someone explain some of the technical jargon that is used when discussing speakers please? For example, the recent review of the Q Acoustics Q7000 speakers has the following in the tech specs section: Front speaker sensitivity (db/w/m) 85 Front speaker impedance (ohms) 6 I don't know if 85 is better or worse than 84 and as for impedance, well, 6 - never a number I've been entirely happy with, but again, is that good or bad? Thanks (and can we get a little emoticon for "sheepish"?)

 

[Anonymous]

Good question, looking forward to expert answers.

Just one thing as I think sensitivy has to do with how easy it is to drive the speakers. What Hi Fi did a review of the ATC SCM100's a short while back and just curious why you detailed the sensitivity as the speakers are active with built in amps so seemed a somewhat spurious bit of data to me?

Anyway minor point, main point is they are simply fabulous speakers (bruv has a pair and also a reinforced concrete floor to accomodate them!, need a ruddy fork truck to shift them about but never heard bass like it, clean, deep the lot)

 

[John Duncan]

Quick response to those two.

Sensitivity = number of decibels produced by the speakers fed by 1w at 1m. So a higher number = a speaker that is easier to drive and will go louder with fewer watts. Generalising, a higher figure is 'better' because it makes it easier to drive by more amplifiers.

Generalising, impedance is a notional figure, and describes a speaker's resistance to load. Most speakers nowadays are 8 ohms, though some are 6 and others 4. I say this is a notional figure because generally it's quoted at one frequency because speakers impedance changes depending on frequency of signal fed to it. None of 8ohm, 6ohm or 4ohm is 'better' but, generalising again, you need an amplifier twice as powerful to feed a 4ohm speaker than an 8ohm speaker without clipping.

 

[fayeanddavid]

Quick response to those two.

Sensitivity = number of decibels produced by the speakers fed by 1w at 1m. So a higher number = a speaker that is easier to drive and will go louder with fewer watts. Generalising, a higher figure is 'better' because it makes it easier to drive by more amplifiers.

Generalising, impedance is a notional figure, and describes a speaker's resistance to load. Most speakers nowadays are 8 ohms, though some are 6 and others 4. I say this is a notional figure because generally it's quoted at one frequency because speakers impedance changes depending on frequency of signal fed to it. None of 8ohm, 6ohm or 4ohm is 'better' but, generalising again, you need an amplifier twice as powerful to feed a 4ohm speaker than an 8ohm speaker without clipping.

Nicely put Mr D

 

[Amadeus1756]

Thanks. I think I need to read and re-read those statements, but I think they make sense!

 

[CnoEvil]

Just to give a practical example of what JD is talking about, and show how you need both figures to get a true picture: -
My speakers are fairly sensitive at 90db.......but , despite being listed as having an eight 8 Ohm Impedance, they can drop to 3.2 Ohms. This means that unless your amp has lots of current available (preferably doubling it as the impedance halves), it won't drive the speakers properly.

This ability of an amp to have ample current available if called for, is as important as having lots of Watts......especially with hard to drive speakers (insensitive or low impedance).

 

[Amadeus1756]

Thanks CNo - just seen this.

How would one know whether the speakers could drop impedance (by what seems a significant amount to me)?

thanks

 

[CnoEvil]

Thanks CNo - just seen this.

How would one know whether the speakers could drop impedance (by what seems a significant amount to me)?

thanks

In the case of my speakers, it's given in Kef's specs. If it is not given, it may require contact with the manufacturer.
Knowledgeable dealers can usually advise, or technical reviews can often cover it.

Amps that can double their current as impedence halves, normally draw attention to the fact, whereas less well performing ones may not. It's always worth checking if they give the number of Watts into 4 Ohms as well as 8 Ohms. eg. Musical Fidelity amps perform well in this area.

 

[Amadeus1756]

Thanks for that Cno.

It does make me realise that I have a lot to learn and there is always something else to learn when one has mastered one topic!