Crossover Freq?

[brazosdog02]

Setting up my speakers with my Denon X4000. I have CM340SE Mains and center and dual Rythmik LVR12s. What should the crossover frequency be set at for the mains and center?

[FirstReflect]

I'd love to give you a super easy, one-size-fits-all answer, but the truth is that the ideal crossover frequencies for your speakers depend on your particular room, and the placement of the speakers and your seats within that room.

As an example, I have customized Sierra Horizon RAAL Front Main and Centre speakers. If I were to play those speakers out in a wide open field, or in an anechoic chamber, they produce nice, linear bass right down to about 40Hz or so. So, based on that, you might think that the best crossover frequency might be 40Hz, or maybe 50Hz to be conservative.

But, in my actual theatre room, if I play a bass sweep through just my Centre speaker while I'm sitting in any of the 3 seating positions across my futon, there's a big dip between about 65Hz and 80Hz, and at 70Hz, the output is basically silent. Now, that's not the fault of the speaker. It is still playing flat and accurate all the way down to about 40Hz. But due to room acoustics, and the particular placement of the Centre speaker and my seats within my room, I get that big bass suck out at 70Hz.

My Front Main speakers, being placed closer to the front corners of my room, actually have a bit of a bass boost -- a "hump" if you will -- at around 50Hz. And if I move from seat to seat on my futon, the bass response is not even and uniform across all three seats. It's "lumpy" or "hilly" below 60Hz.

So in MY particular setup, I have set my Centre speaker to an 80Hz crossover, and I have set my Front Main speakers to a 60Hz crossover. It's not based on the pure output of the speakers themselves. It's based on the real world results that include my room's acoustics. With those crossover frequencies, combined with my dual subwoofers that are placed at the mid-point of each side wall, I have VERY even, linear, and uniform bass that extends below 20Hz. And the transition from any individual speakers to the subwoofers is seamless and completely smooth. It would not be if I had used a 40Hz crossover. And just so you know, when I ran my Onkyo AV Receiver's Audyssey MultEQ XT32 auto-setup program, it set the crossovers to 40Hz. The auto-setup program is not stupid. If you play a bass sweep through any of my Front 3 speakers, they do have strong output down to 40Hz. But using that setting would have left that bass suck out at 70Hz in my Centre speaker, and it would have left the non-uniform bass across my three seats in the Front Main speakers. So, we can be smarter than the auto-setup, is all I'm saying

Bottom line is that the very best approach is to use some bass sweeps and find out exactly what is going to work best for your particular setup and room. Your CMT-340SE speakers, all on their own, should be producing strong, linear bass down to about 45Hz. But your room's acoustics, and the placement of the speakers and your seats within the room will change that, big time.

I recommend going here to make yourself some free bass sweep test tones: http://www.audiocheck.net/audiofrequ...ator_sweep.php

Personally, I use a 10 second long, marked, non-logarithmic sweep from 100Hz down to 30Hz. By check marking the "mark" box, you will get an audible beat every 10Hz during the sweep. So that makes it easy to just count the audible beats to know what frequency you are hearing.

You can burn that sweep to a CD, or just put it on your smartphone or iPod. Naturally, it is only a 2-channel stereo signal. So the best method I've found is to do the following:

Physically disconnect all of your speakers except one. Let's just say, for example, that the only speaker left physically connected by speaker wire to your AV Receiver is the Front Left speaker for now. Go into your AV Receiver's speaker settings menu and set all of your speakers to "Large" or "Full Range" for the moment, and set your subwoofers to "Off" or "None", just for the time being. Now, put your AV Receiver into the "Full Mono" listening mode. That will send the exact same sound to every single speaker channel. If you don't have a "Full Mono" mode, look for a "Party Mode" or an "All Channels Stereo" Mode. All you want is a mode that will take the 2-channel bass sweep that you made and play it through all the speaker channels at once.

Now you can listen to the bass sweep through just that one speaker. You'll easily hear if the bass has a big dip or a big hump anywhere in the sweep. And the audible beats will allow you to figure out the exact frequency to the nearest 10Hz. Remember to listen to the sweep in all of your seats that you care about. There can be big differences from seat to seat!

After figuring out how low you can go before the bass starts to sound uneven in any seat for that one speaker, set the crossover for that speaker above the frequency in the sweep where you started to get dips or peaks. If you hear a hump in one or more of your seats at 50Hz, set the crossover to 60Hz. If you hear a dip at 70Hz, set the crossover to 80Hz. Just go above where you start to have any problems in any seat.

Now, disconnect that one speaker, and connect a different speaker. In our example, disconnect the Front Left speaker, and connect the speaker wire for the Centre speaker. Again, only one speaker physically connected at a time, and play the sweep and have a listen in all of your seats that you care about. You can do this for every speaker in your system!

Once you're done, connect your subwoofers back up and turn them back on in your AV Receiver's speaker settings menu. Double check that all of your crossovers for your speakers are now set to where you want them to be -- above the point in the sweep where the bass became uneven in any of your seats. Now you can play the sweep through one speaker at a time again -- physically disconnecting all but one speaker and your subwoofers. Have a listen to the sweep in all of your seats now. It should be even and linear and smooth in every single seat every time!

Sorry for the long answer and process. But that's the best way. There's no one-size-fits-all because every room and setup is different.

Hope that helps!

[brazosdog02]

That helps tremendously! Ill give it a go! Thank you for the thoughtful and useful response!

[FirstReflect]

Yay!

You're most welcome. The process I described can be a bit tedious, but it's very ear-opening, and totally worth it. It's often amazing how different the bass response can sound from seat to seat, and from speaker position to speaker position. The great thing about playing the bass sweep through one speaker at a time is that there is nothing subtle about it when you hear it. It's like, "holy cow, the frequency response sounds like a roller coaster in this seat, but it sounds almost perfectly flat in this other seat!

It's one thing to just talk about room acoustics and how much it affects the bass response from seat to seat, but it's another to really hear it for yourself. Once you do, it's super easy to appreciate and understand. So I'm really glad you're willing to try out the process I described above. I think you'll find it enlightening and surprising

[brazosdog02]

Meh...didn't work. When I turned off my subs and unplugged all the speakers except the one I wanted to test, the receiver shut down on the low frequency. It would not run unless everything was hooked up and subs were turned on. I just adjusted it with everything on, but can't really tell any difference that way. No idea why the receiver shuts down, but it sure doesn't like it. No stray wires...all banana plugs, so I guess the receiver just isn't designed to be run like that. 8 ohm speakers.

[FirstReflect]

Shut down as in went into protection mode? That would strongly indicate that perhaps one or more pairs of your banana plugs were touching after you had unplugged them, creating a short circuit. It's the same thing as having bare wires crossing. So make sure that none of your unplugged banana plugs are touching each other. I guarantee you that this method works. If your Receiver actually shut down when you tried to play the bass sweep, that's due to a short circuit. It's certainly easy enough for a pair of banana plugs to accidentally come in contact with each other when they're unplugged.