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Crossover Frequesncy Setting

hoover
03-25-2005, 05:00 PM
We just bought a new receiver and speaker system, and I need to set the crossover frequency on the receiver. I am using Polk RM-101 satellites for the right and left channels and an RM-202 center channel. They have a response range of 95-24kHz. My sub is a Polk PSW 303 with a range of 35-160 Hz.

My receiver has a default setting of 80 Hz, and the manual recommends this setting, except "when using small speakers, setting the crossover frequency to a high frequency may improve frequency response for frequencies near the crossover frequency." (YES, that's a quote, too.)

Should I set the C. F. at the low end of the small speakers, or the upper end of the sub? Mayabe I'm way off base and should do something else. Help is appreciated. Thanks.

tdeluce
03-25-2005, 05:11 PM
THX Receivers in THX mode all use 80 Hz as the cross-over
frequency for the subwoofer ( I believe this is the THX
reference setting ). You should be o.k. with this
setting and those speakers. Your preference is of course
subjective - you can lower or raise the cross over frequncy
to see if you like the sound better.

hoover
03-25-2005, 05:17 PM
Will this cause the smaller speakers to "attempt" to play frequencies lower than the stated 95 Hz limit (cause distortion)?

Obviously, I'm pretty new to this, so bear with me if this is pure ingnorance.

tdeluce
03-25-2005, 05:19 PM
sorry, I just re-read the frequency response of your speakers -
if you choose 80 Hz, then you would have a dead space
of 15 Hz - I would select 100 Hz as your cross over frequnecy...

hoover
03-25-2005, 05:22 PM
Also, what would be the advantage/disadvantage of using/not using the speaker level input and output on the back of the sub?

Man, I've missed out on a lot since my last stereo equipment purchase. What happened to plug-n-play?!?

tdeluce
03-25-2005, 05:27 PM
With a C.F. of 100Hz and your speakers set to small, all
frequencies below 100 Hz will be send to your sub-woofer
( which can easily drive this ) and all frequencies above
100 Hz will be sent to your speakers. Should sound
good!

hoover
03-25-2005, 05:30 PM
sorry, I just re-read the frequency response of your speakers -
if you choose 80 Hz, then you would have a dead space
of 15 Hz - I would select 100 Hz as your cross over frequnecy...

OK, good - thats the way I understood it. I was starting to think I was completely off base in my approach to this.

hoover
03-25-2005, 05:32 PM
What about using the input/output on the back of the sub?

tdeluce
03-25-2005, 05:33 PM
I am not familiar with the specifics of your subwoofer - so
read the manual - you want to make you use a line-level
input on the subwoofer than bypasses the cross-over circuitry
of the subwoofer.

The reason being is that if you use both the cross circuitry
of your receiver and your sub-woofer you wil get unknown
results.


Plug it in - then play with it for days ( the Microsoft Way :-)

hoover
03-25-2005, 05:35 PM
So I should probably either use the CF in the receiver, or the in/out on the sub - but not both, right?

tdeluce
03-25-2005, 05:38 PM
yes, correct - one or the other but not both...

hoover
03-25-2005, 06:34 PM
The sub's manual says the "recommended" connection method for use with small satellites is to:

1 - set front speakers to "large" on the receiver (even though they aren't)
2 - Connect the L & R front channels to speaker level inputs on the sub using speaker wire.
3 - Connect the 2 front speakers to the sub's speaker level outputs.
4 - Connect center channel directly to receiver
5 - Set Subwoofer to "off" on receiver.

They say that this will create in essence a continuous range that where the small speakers cutoff, the sub will pick up. I guess it makes sense in theory.

Akira
03-25-2005, 10:16 PM
The only test is setting the x-over frequency to what sounds good to you...that also goes for setting the spkr inputs to the sub.
As your manual says this configuration sets a continuous sound spectrum, and this may be the best when using limited range small speakers. When using full range fronts it is always better to use an electronic X-over (in this case your receiver) as a discrete separation is more favourable. This is why all pro touring systems are set up this way. Also there is considerable spillage at the X-over point even though the best electronic X-overs are 24db/octave while most internal systems (passive ie: your sub) are 12db/octave. This is caused by a natural over lapping "bump" where ever that point is set. This spillage can be a disireable thing in a smaller limited band system, or a nightmare in large full range systems--thus the difference between passive and active networks.
Also be aware that certain frequencies are more desireable as a natural X-over point. 160Hz is a known bad point. For this reason I prefer 60Hz in pro rigs as opposed to 80Hz (fundamental harmonic of 160Hz) even though this is a THX "home" standard. For your system I would choose 100Hz.
Akira, Sound Chaser Pro Audio

hoover
03-26-2005, 04:32 PM
.....As your manual says this configuration sets a continuous sound spectrum, and this may be the best when using limited range small speakers. When using full range fronts it is always better to use an electronic X-over (in this case your receiver) as a discrete separation is more favourable. This is why all pro touring systems are set up this way. Also there is considerable spillage at the X-over point even though the best electronic X-overs are 24db/octave while most internal systems (passive ie: your sub) are 12db/octave. This is caused by a natural over lapping "bump" where ever that point is set. This spillage can be a disireable thing in a smaller limited band system, or a nightmare in large full range systems--thus the difference between passive and active networks.
Also be aware that certain frequencies are more desireable as a natural X-over point. 160Hz is a known bad point. For this reason I prefer 60Hz in pro rigs as opposed to 80Hz (fundamental harmonic of 160Hz) even though this is a THX "home" standard. For your system I would choose 100Hz.
Akira, Sound Chaser Pro Audio

:confused:
Alright, I got the jist of most of your reply (thanks, too). I spoke to the guy who sold us the setup and he said that routing it through the subwoofer's level input and output, and NOT using the LFE input, that when watching something with digital audio, the dedicated LFE signal that is supposed to come out of the Sub, won't.

He actually said to do both. Keep them wired the way I have them now, AND add an RCA connection for the unfiltered LFE signal directly from the receiver. Would this work? He reasoning is that my receiver automatically detects a digital signal, thus activating the LFE when needed, otherwise, non-digital audio sources will play via the speaker wire setup through to subwoofer's IN/OUT.

On top of all this, my wife called and said that they delivered the new TV (Sony KDF 42" RP-LCD), but no audio is coming from the TV speakers (she was able to find it in the menu and they were turned on). I told her don't mess with anything and I'll go through the setup when I get home.

My brain is melting........

tdeluce
03-26-2005, 06:19 PM
I would skip the sound from your Sony TV and use your
polks...

The two key things to remember is to:

1) place the cut-off frequency above the low end of the frequency
spectrum your speakers are capable of ( and of course, below
the high end of the frequency your sub-woofer is capble of ).
2) use either your receiver or your sub-woofer's filters - not
both.

The rest is preference...

hoover
03-27-2005, 03:53 PM
......
2) use either your receiver or your sub-woofer's filters - not
both....

That's what I thought, but he SWORE to me that I should do it this way. To be honest, it sounds good that way, but I am comparing it to my old system that was from before digital audio was around.

Thanks.

rbinck
03-27-2005, 07:15 PM
If it sounds good to you, I'd say you got it.