Computers & Electronics

Help with AVR & speaker crossover frequencies

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  • Nov 6th, 2019 8:53 pm
[OP]
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Oct 23, 2008
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Help with AVR & speaker crossover frequencies

I'm confused over the crossovers. I've tried reading through countless websites and I'm still unsure. A few say just to stick the crossover at 80Hz (THX) for all speakers, while another site I read says to try setting it at approximately 10Hz above the lowest frequency for a better roll off.

I'd like to see what the opinion of RFD are:

Front Towers: 55Hz - 30KHz
Centre: 55Hz - 30KHz
Surround bookshelf: 60Hz - 30KHz
Sub: 27Hz - low pass crossover setting at source (LFE input)

So based on this, I can set all the crossovers as low as 70Hz?
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5 replies
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Jan 21, 2018
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There is no clear rule. If you were making detailed measurements in an anechoic measurement chamber, it would depend on which of your speakers has a better response in the 70-80 Hz range, the sub or the others.

But you aren't making detailed measurements, and any actual room in your home is going to be far from ideal. You just want the best sound possible to your ears. So test it. You probably won't hear any difference at all. If you do hear a difference, imaginary or real, set it the way you prefer. It isn't going to make a big difference.
[OP]
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Oct 23, 2008
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GTA, ON
Scote64 wrote: There is no clear rule. If you were making detailed measurements in an anechoic measurement chamber, it would depend on which of your speakers has a better response in the 70-80 Hz range, the sub or the others.

But you aren't making detailed measurements, and any actual room in your home is going to be far from ideal. You just want the best sound possible to your ears. So test it. You probably won't hear any difference at all. If you do hear a difference, imaginary or real, set it the way you prefer. It isn't going to make a big difference.
Thanks. Sorry, I'm trying to educate myself with the setup. I've always found the sound to be weak and only now am I trying to figure it out.

Another question. All my speakers are rated for 8 ohm, whereas the receiver drives either 4 ohm or 6 ohm. In hindsight I guess I should have purchased equipment that were all equal, but here we are. I understand now that because of the difference, the speakers will not run as loud because of this. So my question, does it make a difference if I set the receiver at 4 or 6 ohm? From what I read it says if I set at 6 ohm, the speakers will run at 30% less power, so will it run even less at 4 ohm? Can I counter this by just turning up the volume?
Tis banana is IRIE 😎

10% off is cold, 50% off is warm, 75% off is hot, but FREE IS RFD!
Deal Fanatic
Jan 21, 2018
5935 posts
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Vancouver
Speakers may have 8/6/4 ohm impedance, probably in that order of how common it is. This says little about the volume the speakers produce.

First, how much volume is produced for a given amount of power depends on the speaker's efficiency. It varies widely. A lot of high quality speakers tend to be very inefficient because they fine-tune the sound by trimming away unwanted bits, sort of like trying to make a perfect paper circle with scissors by trimming off imperfect bits. You end up with a much smaller circle than you started with in order to get it as round as possible.

Second, this is just the nominal impedance, because it actually varies widely across the frequency spectrum, and different speaker designs may have very different impedance curves. Normally they specify something close to the lowest value to make sure that you aren't being misled into over-driving your amp, but the average impedance may be much higher. I've seen speakers rated as "8 ohms" or "4 ohms" that had impedance curves that could easily have been rated either way depending on what the manufacturer thought was significant.

In any case, you will normally turn the volume up to a comfortable level, averaging way below the maximum power the amp can produce, regardless of the speaker impedance. All things being equal, an amp can normally produce more power into a lower impedance speaker, but the difference in volume that produces would be hard to even notice because of the non-linear way your ear hears volume vs. power.

Most amps don't have any sort of "ideal" impedance setting. If the power output is within their rated range, there should be no audible effect from driving speakers of different impedance.
[OP]
Deal Guru
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Oct 23, 2008
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@Scote64

Thanks... I'm learning a lot. Your explanations are a lot easier to understand then what is written online.

The speakers efficiency rating isn't bad, 90/90/88 dB respectively
Tis banana is IRIE 😎

10% off is cold, 50% off is warm, 75% off is hot, but FREE IS RFD!
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Mar 6, 2003
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I would start with 70Hz and go up to 80 and see if you can hear that the bass sounds fuller with either setting. If not, stick with 70Hz.

With some receivers you can set the crossover for front/center/rear independently, so you might go with 60Hz for the larger speakers and 80 for the rear.

Set the receiver at the highest ohm setting for starters. Setting it to the lower ohm setting usually kicks in a voltage limiting circuit essentially to prevent the receiver from overloading with speakers that have a lower impedance (ohms). If your speakers aren't low impedance, then this ultimately limits the power output.

You only use the lower setting if you have 4 ohm speakers AND stress the receiver at high volume.
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