Impedance, High or low? |
GMC Forum > Discussion Boards > VINTAGE GMC > Community Activities and Tutorials > Ask an Instructor > Andrew Cockburn
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Jul 24 2008, 08:26 PM
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Hi There
 QUOTE (kjutte @ Jul 24 2008, 08:59 AM)  Ok, I know that with a higher impedance, you get a lesser current, and thus lower effect (wattage). High imp=high load speaker, yes? A higher impedance is harder for the amp to drive, and for a given maximum voltage swing you will on average get less current, which reduces the wattage or power output. Impedance is not the same as resistance though, although the concepts are very similar, and you need to understand that the effect will be seen averaged out over time as the waveform rises and falls. speakers also have reactance which makes this a more complex subject, but essentially what I said above is correct. However, most tube amps have different settings for different speakers that change the turns ratio of the output transformer to compensate for the reduced current by increasing the output voltage, thus driving the power back up. QUOTE (kjutte @ Jul 24 2008, 08:59 AM) Is this good or bad? I mean, what defines a good speaker? Can you please help me understand how good speakers are made, and how the impedance stuff works? Appreciate it Andrew! Higher or lower impedance is neither good nor bad, it just reflects the way the speaker is designed. A bit like saying that a 4 cylinder engine is not better or worse than a 6 cylinder engine - they both do the same job. What is more important though is the sensitivity of the speaker - again a product of its design. A more sensitive speaker will sound louder for a given power input and that is usually regarded as being a good thing QUOTE (kjutte @ Jul 24 2008, 08:59 AM) Edit: I also wonder about the watt stuff. Everyone's saying "50 watt speakers" etc, but that's just the voltage and current, and has seemingly nothing to do about the element itself (which is the load). I'm just really confused on this subject. Looking forward to your feedback 50W for a speaker rating just tells you the maximum power the speaker can handle before it is damaged. You don;t have to put 50W through it. In contrast, 50W fort an amp is the maximum output you will get if you turn it fully up. Obviously you don;t want the maximum output of the amp to exceed the rating of the speaker but there is nothing wrong with running say a 15W amp into a 50W rated speaker - the speaker wil be fine, and the amp just won't come close to damaging it. QUOTE (kjutte @ Jul 24 2008, 08:59 AM) Edit again: ALthough I know that the current also is derived from the impendace... Again, I am messing around. lol...  The maths gets a little complicated, but the easiest way is to compare it to ohms law, meaning that the current is inversely proportonal to the impedance. -------------------- Check out my Instructor profile
Live long and prosper ... My Stuff: Electric Guitars : Ibanez Jem7v, Line6 Variax 700, Fender Plus Strat with 57/62 Pickups, Line6 Variax 705 Bass Acoustic Guitars : Taylor 816ce, Martin D-15, Line6 Variax Acoustic 300 Nylon Effects : Line6 Helix, Keeley Modded Boss DS1, Keeley Modded Boss BD2, Keeley 4 knob compressor, Keeley OxBlood Amps : Epiphone Valve Jnr & Head, Cockburn A.C.1, Cockburn A.C.2, Blackstar Club 50 Head & 4x12 Cab |
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Jul 24 2008, 08:45 PM
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QUOTE (kjutte @ Jul 24 2008, 03:41 PM) I know all the trigonometry mate, hand me the complex stuff. I know that resistance+reactans=impedance. There's a great Wikipedia page on it: http://en.wikipedia.org/wiki/Electrical_impedance -------------------- Check out my Instructor profile
Live long and prosper ... My Stuff: Electric Guitars : Ibanez Jem7v, Line6 Variax 700, Fender Plus Strat with 57/62 Pickups, Line6 Variax 705 Bass Acoustic Guitars : Taylor 816ce, Martin D-15, Line6 Variax Acoustic 300 Nylon Effects : Line6 Helix, Keeley Modded Boss DS1, Keeley Modded Boss BD2, Keeley 4 knob compressor, Keeley OxBlood Amps : Epiphone Valve Jnr & Head, Cockburn A.C.1, Cockburn A.C.2, Blackstar Club 50 Head & 4x12 Cab |
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