Crossover Frequency Setup with new speakers

[Vancouver]

Usually I am pretty good a setting up my home theater equipment, but I am having a little trouble setting the crossover frequency and choosing between the "Large" and "Small' Setting. Your guidance would be appreciated.

Here is what I have, and their specs.

Centre:
B&W FPM 4
Crossover frequency: 180Hz/3.7Khz
Frquency Range: -6dB at 65Hz and 42kHz

Front Mains:
B&W FPM 6
Crossover frequency: 180Hz/4.8Khz
Frquency Range: -6dB at 55Hz and 42kHz

I have the Denon AV-1803 which gives me these options:

Crossover Frequency: 80Hz/100Hz/120Hz
Speaker Sizes: Large/Small

right now I have my mains set to Large, Centre and surounds set to Smal and Crossover Frequency set to 120Hz.


Would anyone know what I should change and why?

 

[Vancouver]

I have to Laugh that I have a tittle like "Audio Alchemist" when most of my posts have been questions!

 

[MDS]

The xover frequency that you list is the frequency at which the speaker itself hands off the signal from one driver to the other - it is not the frequency to be concerned with when determining your receiver xover setting.

The frequency you want to look at is the -3 dB (F3) point of the speaker and then set your receiver xover at roughly 1/2 to 1 octave above that point (and listen and experiment to see which you prefer). Given that the specs you list give the point at which the speaker is -6 dB, the F3 point is slightly higher. 120 Hz is probably a reasonable starting point, although 100 Hz may be better.

In general, you want all speakers Small, Sub=yes, and a suitable xover setting that is based on the capabilities of the speakers. If any of the speakers are truly full-range or at least close (20-30 Hz - 20 kHz), and very few are, you want to avoid the Large setting. Let the sub do what it is designed to do - reproduce all the low frequencies.

 

[j_garcia]

What MDS said, except with a -3dB of 65Hz and 55Hz, I'd start with the 80Hz x-over, then compare to the 100Hz x-over; my guess is also that 100Hz will be the best compromise. The 1/2 to 1 octave above the -3dB is a very good rule of thumb, but your room is also a factor in the final response you actually get. You may find that you can get away with 80hz and it works well enough. My mains are -3dB at 55Hz and I use an 80Hz x-over and it works very well.

 

[Vancouver]

What MDS said, except with a -3dB of 65Hz and 55Hz, I'd start with the 80Hz x-over, then compare to the 100Hz x-over; my guess is also that 100Hz will be the best compromise. The 1/2 to 1 octave above the -3dB is a very good rule of thumb, but your room is also a factor in the final response you actually get. You may find that you can get away with 80hz and it works well enough. My mains are -3dB at 55Hz and I use an 80Hz x-over and it works very well.

perhaps I gave the wrong specs. I gavew the frequency range when I should have given the frequency response.

Here is the frequency response:

the FPM 6 is:65Hz – 22kHz ±3dB on reference axis
the FPM 4 is:72Hz – 22kHz ±3dB on reference axis

So setting setting the cross over to 80 would be the best?

 

[j_garcia]

Sorry, I missed that those specs were -6dB on the low end. If you can't set separate x-overs for various speakers (Front, surround, etc...) then based on that, I would go with a 100Hz x-over, then compare it to 120. With 120Hz, you will start to lose some midrange in the main speakers and the sub may start to be easier to localize due to the fact that it will be playing in a higher range.

 

[Vancouver]

Sorry, I missed that those specs were -6dB on the low end. If you can't set separate x-overs for various speakers (Front, surround, etc...) then based on that, I would go with a 100Hz x-over, then compare it to 120. With 120Hz, you will start to lose some midrange in the main speakers and the sub may start to be easier to localize due to the fact that it will be playing in a higher range.

Thanks. I am looking forward to getting my Rotel reciever as I understand you can set specific cross overs for each channel.