A few questions regarding ohm/watt.

[jst]

My amp is Cambridge Audio Azur 640A, it has A (left+right) and B (left+right) speakers and the spec related to my question is :
- Power output: 65 watts per channel into 8Ω (stereo)
- Speaker load impedance: 4Ω to 8Ω

My speaker is Wharfedale Diamond 9.2 with 6 ohm/100 watt. It can be bi-wired.

If I use bi wire with B speakers for HF (High Frequency) and A speakers for LF (Low Frequency), my questions are :
1. what is the impedance being used, 4 or 8 ?
2. how many watts are coming out to each of the speakers ?
3. should I bi-wire or should I use just A speakers output and put back the jumpers on the speakers and NOT bi-wire it ?

Thx.

 

[RayDunzl]

My speakers measure 4ohm (with an ohmmeter) if jumpered.

And measure 8 ohms each for woofer and "tweeter" if not jumpered.

Single or bi-wire should present 4 ohms to the amplifier, in my case..

 

[RayDunzl]

If I use bi wire with B speakers for HF (High Frequency) and A speakers for LF (Low Frequency), my questions are :

1. what is the impedance being used, 4 or 8 ?

Probably the same as whatever they are quoted to be.

2. how many watts are coming out to each of the speakers ?

Watts occur as dissipation inside the speaker cabinet.

What "comes to the speaker" is voltage and current.

3. should I bi-wire or should I use just A speakers output and put back the jumpers on the speakers and NOT bi-wire it ?

That should likely be classified as a personal choice. I don't know of a study that shows any real diference.

 

[VintageFlanker]

what is the impedance being used, 4 or 8

Neither. Impedance being variable relative to frequency.

2. how many watts are coming out to each of the speakers ?

None. Watts don't measure acoustic pressure.

Regarding the amplifier tho, it will output the same power bi-wired.

should I bi-wire or should I use just A speakers output and put back the jumpers on the speakers and NOT bi-wire it ?

Bi-wiring is a waste of time and bring absolutely no audible performance whatsoever. Just use A outputs with jumpers.

 

[jst]

Ok thx for the answers. Not as easier to imagine as I would expect though. I read that 50watt 8 ohm amp would work harder if using 4 ohm speaker trying to provide 100watt which I thought since I use 6 ohm speaker would also try to draw 1.5x power. If everything is the same and doesn't matter then a speaker is just a speaker , left or right.

My speakers measure 4ohm (with an ohmmeter) if jumpered.

And measure 8 ohms each for woofer and "tweeter" if not jumpered.

Single or bi-wire should present 4 ohms to the amplifier, in my case..

Yea that's the thing, I watched a youtube video there's series and parallel connection which is kinda confusing since a box of a speaker can consist of more than one speaker which we don't know which one is used inside.

But in the end I now use jumpers and let the speakers stay 6 ohm as written on the spec and the amp 8 ohms as the spec says and skip the confusion hahah.

Oh and I'm getting a Canare 4s11 speaker cables, it says 14 AWG if using 4 cables, but 11 AWG if using all 4 combined into 1, so it's around 12/13 AWG then if I use 2 and 2 ? or cmiiw.

 

[DVDdoug]

The only "advantage" I see to any of this is that you can play-around with the A/B switch and listen to the woofer, or tweeter, or both. Usually the A/B switch simply connects both speakers (or outputs) in parallel in the A+B position so there's really no difference (you're not bi-amping).

If only the woofer is connected the amplifier should "see" a (nominal) 6-Ohm load at low frequencies and higher impedance above the crossover frequency.

If only the tweeter is connected the amplifier should "see" a (nominal) 6-Ohm load at high frequencies and higher impedance below the crossover frequency.


In reality, the impedance isn't perfectly-constant over the frequency range so without an impedance vs. frequency curve it's hard to know...

1. what is the impedance being used, 4 or 8 ?

With normal program material most of the energy goes to the woofer. With test tones a "10W" 100Hz tone would send 10W to the woofer and a "10W" 5kHz tone would send 10W to the tweeter* (no matter how they are wired). That's making the assumption that the impedance is the same at 100Hz and 5kHz.

As Ray says, the amplifier actually puts-out a voltage. The current (and power) depends on the impedance/resistance, and the voltage - Ohm's Law says Amps = Volts/Resistance.

If there is no speaker connected, the voltage is still there but there is no current and no wattage. It's the same with the power outlets in your house... If you live in the U.S., we have 120VAC at the power-outlet. The voltage is always there (if there's not a switch) but no current flows and no power is consumed until you plug something in and turn it on. A 100W lamp "pulls" a little less than 1 Amp. A hair drier or toaster takes about 12 Amps. If you plug-in (and turn-on) a toaster and hair drier at the same time you get excess current, a circuit breaker blows, and voltage drops to zero.

Power (Watts) is calculated as Current x Voltage.

With both formulas you can derive: Power = Voltage squared/Resistance (often handy) or Current squared x Resistance.


* You have to be careful with test tones. A "100W" speaker is designed to handle 100W on the peaks with regular program material and that might be 10 or 20W Average. You can probably fry it with a constant 100W tone. And the tweeter can handle even less power than the woofer.

 

[DVDdoug]

which I thought since I use 6 ohm speaker would also try to draw 1.5x power.

That's if you don't touch the volume control... 100W into 4-Ohms is the same as 100W into 8-Ohms and the same loudness assuming equal speaker efficiency.

But actually the "work" (the heat generated/lost inside an amplifier) is complicated and I think it requires some calculus... If I remember correctly a Class A/B amplifier generates the most internal heat (maximum "stress" on the transistors/MOSFETs) at 1/3rd the maximum power (based on available voltage) I clearly remember that maximum power is not worst case. An "ideal" Class-D amplifier is 100% efficient and doesn't generate any internal heat.

 

[jst]

2) Biwiring is snake oil, and bi-amping takes a certain amount of knowledge. Because you are here and asking questions, I think the best advice is to avoid both and go with the manufacturer's default arrangements. If you like to experiment (I do) you can experiment to your heart's delight, but you can also blow stuff up (I did) and that can get expensive.

Yes exactly what I'm doing now ! hahah. And with any changes made, it is always playing mind tricks saying it's "better" until realizing it's probably not and just the same