Crossover Frequency Recomendation

[rpizzo]

I am one of these people who has a home theater, but doesn't understand much about it. I would appreciate suggestions on the appropriate crossover frequency setting on my Denon 2805. I have Niles HD8 left/right wall speakers, a Niles HD center wall speaker, Niles HD8 ceiling surround speakers, and a Velodyne SPL 800 sub. The low end on all of the Niles speakers is 50hz (except for the center, which is 45hz). The sub starts at 28hz. I set the crossover at 80hz but, like I said, I really don't understand this stuff.

Also, can anyone tell me the relationship between the crossover frequency and the AV receiver speaker settings (i.e., large/small)? I don't understand why the speaker setting should make any difference if you set the crossover frequency. I also don't understand what the other (high) sub crossover does.

 

[MDS]

Speaking in terms of general rules of thumb, the recommendation is to set the crossover frequency to 1/2 to 1 octave above the F3 point of the least capable speaker. The rule breaks down if the speakers are not too bass capable, however. You wouldn't want to use 150 Hz if the speakers go down to 75Hz, for example, because that is just too high and the bass will be easily localizable.

If the F3 point of the Niles is 50Hz, then anywhere from 75Hz (1/2 octave above) to 100 Hz (1 octave above) should work well. THX specifies 80Hz for pretty much everything and for most systems, it is appropriate.

Here is a good article from Secrets on the topic: http://www.hometheaterhifi.com/volume_9_3/feature-article-multiple-crossovers-9-2002.html

 

[warpdrive]

The speaker size does the following:

Large: All bass that is encoded for that channel is sent to the speaker. Let's say Godzilla is on the right side of your screen and there is a 60Hz thump sound. The receiver will not redirect that signal. So the thump sound is sent to the right speaker.

Small. Any signals that are below the crossover region is rediverted to your sub instead of each channel. If you have the crossover set to 80Hz, the same 60Hz sound is sent to your sub instead of your right speaker as it is lower than the crossover setting. This is actually ok, since 60Hz sounds are hard to localize.

The LFE channel signal also abides by the bass management settings. The LFE channel in DD provides sounds less than 120Hz, but if you set up with your system without a sub, it will redivert the sounds above the crossover to your other speakers. If you have a sub, it will only send the sounds less than crossover point to the sub, and sent the rest to your other speakers.

So in summary, if your speakers are set to small, all bass destined for that speaker and LFE signal are sent to the subwoofer below the crossover point. If the speaker is large, then all bass destined for that speaker plus some of the LFE signal is sent to that speaker. http://www.dolby.com/assets/pdf/tech_library/38_LFE.pdf

For the most part, if you're speakers are capable of adequate bass output (flat response 50-60Hz) without distorting and your receiver is capable of outputting a 50-60Hz signal to all five speakers at your given listening level, then you may actually want to try lowering the crossover to 60Hz. You'll have to listen and see which setting is better. I have mine set to 60Hz, and I find I get less localization of bass for my system. Also, how well your sub "blends" in with your speakers. Some larger subs are really designed to augment the lower frequencies, and it's better to let your main speakers handle sounds in the mid bass (say 80Hz). 80Hz is a safe setting for most people, and Dolby chosen it to the best compromise for most home systems. I would guess that 80Hz is pretty much optimal for your system and the safest choice.

 

[rpizzo]

Thanks for the information. It was a big help.

 

[gene]

You'll have to listen and see which setting is better. I have mine set to 60Hz, and I find I get less localization of bass for my system.

Actually 80Hz is not localizable. What you are likely hearing is excessive bass energy b/c of the subwoofer and main speakers are combining bass energies (up to 6dB) at the frequencies they are both reproducing.

Also, regarding the article you pointed out is not entirely accurate. Most well designed processors will NOT truncate lfe info regardless of what you set the xover frequency for. We will be writing an article about this in the future.

Best advice is to start with all speakers on small and xover at 80Hz. Unless you have your main speakers at the same path differences from center channel to listener as the sub, you will likely do more harm than good keeping them set to large. Properly integrating multiple subs in a system with all speakers set small is usually the best way to go.