3-way IMPEDANCE HELP!!!

jmechie1 · 31st May 2011, 09:44 PM

Okay, been building a pair of 3 way floorstanders, and I'm having a time getting my head round the total impedance.

Got an 8" hivi m8n woofer with 8ohm impedance, 6.5" vintage wharfedale mid with 6ohm impedance and an 8ohm tweeter.

What is the total impedance likely to be? I want to make sure I'm not damaging my amp if I run A+B speakers (amp is an old Audiolab 8000A).

Cheers, James

wakibaki · 1st June 2011, 01:19 AM

It's just not possible to say on the basis of the information provided. It depends on how the individual drivers are connected together, i.e. what crossover you employ.

Crossover? Yes, crossover, that thing that directs low frequencies to the woofer, mid frequencies to the midrange and high frequencies to the tweeter.

The whole shebang will be influenced by the comparative efficiencies of the drivers, so we'd want to know that, but the whole arrangement would probably come out at 8 ohms, since it's comparatively simple to waste a bit of power in a 2 ohm resistor to bring the 6 up to eight, now you need a crossover to 3 * 8 ohms. You may also need some attenuation (resistor L-pads) to equalize the efficiencies. Now you have to think about what frequencies you're going to cross the drivers over.

That's the simplest way to think about it.

w

jmechie1 · 1st June 2011, 10:29 AM

Oh, sorry I completely forgot about the crossover. It's crossed at 500Hz and 4kHz.

The bass woofer is rated at 88dB (2.83v/1m), the tweeter is 93dB, and I believe that the mid is 90dB.

I had thought about just wiring a 2 ohm power resistor in series with the mid driver, but I wasn't sure how this would affect the sound.

James

AllenB · 1st June 2011, 10:59 AM

It will probably be OK. I wouldn't go putting series resistors in for no good reason. Just keep the crossover fairly standard.

Cal Weldon · 1st June 2011, 01:51 PM

Your system has a nominal impedance of 8 ohms. To be sure, use a multimeter on your terminals. I should read about 6 ohms DCR.

31st May 2011, 09:44 PM	#1
jmechie1 diyAudio Member Join Date: Apr 2011	3-way IMPEDANCE HELP!!! Okay, been building a pair of 3 way floorstanders, and I'm having a time getting my head round the total impedance. Got an 8" hivi m8n woofer with 8ohm impedance, 6.5" vintage wharfedale mid with 6ohm impedance and an 8ohm tweeter. What is the total impedance likely to be? I want to make sure I'm not damaging my amp if I run A+B speakers (amp is an old Audiolab 8000A). Cheers, James

1st June 2011, 01:51 PM	#5
Cal Weldon Speakerholic diyAudio Moderator Join Date: Jan 2004 Location: British Columbia	Your system has a nominal impedance of 8 ohms. To be sure, use a multimeter on your terminals. I should read about 6 ohms DCR. __________________ Next stop: Margaritaville Some of Cal's stuff \| Cal Weldon Consulting

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1st June 2011, 01:19 AM	#2
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	It's just not possible to say on the basis of the information provided. It depends on how the individual drivers are connected together, i.e. what crossover you employ. Crossover? Yes, crossover, that thing that directs low frequencies to the woofer, mid frequencies to the midrange and high frequencies to the tweeter. The whole shebang will be influenced by the comparative efficiencies of the drivers, so we'd want to know that, but the whole arrangement would probably come out at 8 ohms, since it's comparatively simple to waste a bit of power in a 2 ohm resistor to bring the 6 up to eight, now you need a crossover to 3 * 8 ohms. You may also need some attenuation (resistor L-pads) to equalize the efficiencies. Now you have to think about what frequencies you're going to cross the drivers over. That's the simplest way to think about it. w

1st June 2011, 10:29 AM	#3
jmechie1 diyAudio Member Join Date: Apr 2011	Oh, sorry I completely forgot about the crossover. It's crossed at 500Hz and 4kHz. The bass woofer is rated at 88dB (2.83v/1m), the tweeter is 93dB, and I believe that the mid is 90dB. I had thought about just wiring a 2 ohm power resistor in series with the mid driver, but I wasn't sure how this would affect the sound. James

1st June 2011, 10:59 AM	#4
AllenB diyAudio Member Join Date: Oct 2008	It will probably be OK. I wouldn't go putting series resistors in for no good reason. Just keep the crossover fairly standard.

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