Impedence question

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Turbo-T
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Posts: 6
Joined: Thu Jul 31, 2014 6:34 pm

Impedence question

Post by Turbo-T » Wed Mar 24, 2021 7:13 am

Stereo Configuration
Mixer > 2 ch EQ > 2/3 way crossover
118 + SP2 per side

Does the crossover split/isolate the speaker loads into separate 8 ohm at outputs or keep them combined resulting in 4 ohm load as in parallel ?

Thanks in advance,

Bartman
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Posts: 500
Joined: Fri Sep 19, 2008 11:15 am

Re: Impedence question

Post by Bartman » Thu Mar 25, 2021 9:11 am

In your chain of connections, there is no mention of amplifier after the crossover. Assuming you are using the crossover 2-way, stereo, and have 4 amplifier channels (Left Low, Left High, Right Low, Right High) and one channel to one sub or top, then each channel is seeing an 8 ohm load. Do NOT daisy-chain any cables from the sub to top, as this will short out the two amp channels powering them.

If you have your system connected some other way, please clarify.

Turbo-T
New Member
Posts: 6
Joined: Thu Jul 31, 2014 6:34 pm

Re: Impedence question

Post by Turbo-T » Thu Mar 25, 2021 8:39 pm

Thanks Bartman.

Yeah, I guess I left out amplification because my main question is whether the single input (1 ea L/R) is split in the crossover circuitry or is it parallel up to the low/high output but I think I answered my own question before I could get back here and modify the original message.
This would defeat the crossover.

I was trying to repurpose amplifiers from a previous system (4 ohm per channel) where I wouldn't have to buy new equipment, much higher in wattage [email protected]

Maybe I'll dig out 4 old La Scallas for lows.... :D

Thanks for your response,

Bartman
Member
Posts: 500
Joined: Fri Sep 19, 2008 11:15 am

Re: Impedence question

Post by Bartman » Fri Mar 26, 2021 9:14 am

Impedance is irrelevant at the crossover inputs and outputs (obviously except if there's a short or damaged equipment). The impedance of speakers is only "nominally" 8 ohms... that is, if you look at the actual impedance across the frequency spectrum, there will be places where it's much higher and some that are a bit lower. For the sub, impedance rises to extremely high the higher the frequencies go (out of the sub's normal operating frequency range.) The sub will also go far below 8 ohms for frequencies below its rated frequency range. Suppose the low usable limit is 40 Hz, and you send it a 20 Hz signal, it will be like 5 ohms instead of 8. This is why it's important to use a high pass filter (low cut) so you don't sent it frequencies it can't handle. It will draw even more power from the amp, and either burn the voice coil or over extend and jump out of the magnet gap (on a positive swing) or slam into the back of the magnet structure (on a negative swing).

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