Axiom Home Page Forums General Discussion Stereo Crossover setting for a Sub

I recently purchased a REL sub Q150E to go with my 2 channel Rotel/Axiom system (see below my system). I use High-pass level connection in my sub, but I don't seem to set the crossover in the sub right. I initially thought it sounded right around 40 MHZ but then I moved it up to around 60 and sounded kind of better. What do you guys do with your Axiom floorstanders. Any suggestions??

Rule of thumb is set crossover at 80. Some go to 60. Try both and see what sounds and works best. I have 60s with a SVS PB12 sub and I have my mains at small and crossed at 80.

I use 80 with all speakers set to small.

The ear test is best but for rules of thumbs there are two main ones.

1. Set the crossover between 1/2 octave to a full octave above the minimum frequency response of the mains. So a speaker with a 40hz FR would be crossed at 60hz to 80 hz.

2. Set the crossover to 2 times the FR. ( Same as one octave up). 40hz speaker gets crossed at 80hz.

The instruction manual of my ICMB recommends to add 10Hz to the +/- 3 DB point of the speaker. If you go by that try 50 Hz on the subs crossover. I have my 80s set to 60 Hz, there is no 50Hz setting on the ICMB or that would have been what I would have chosen.

Thank you guys for the advice! It is great to hear what the other Axiom owners do with their Axiom floorstanders. I never owned a sub before - if you don't count here the sub that came with my HTIB or PC sub.

I now realize that I was wrong in the first place when I set it up at 40, thinking that the sub will cover the lower frequencies not covered by the floorstanders. I am gonna try setting it at 60 and 80 this evening when I get back from work.
I have placed it close to the corner of the room, behind the right spekaer, with the woofer facing out and towards listening position. Is that the usual pattern? I tried it in different places, even by the left speaker.

As for setting the mains at "small" or "large", I cannot do that since I do not have a multichannel receiver/processor with such setting. I have a 2 channel processor/power amp combo (please see below).

Placement depends on your room, and where it sounds best to you. Many have recommended the crawl test: place the subwoofer in your primary listening position, and play a CD with tons of bass, and then crawl around the room. The area where the bass sounds the best, is where you should place your subwoofer.

How do you have your subwoofer hooked up right now?

I use the high-pass connection on my sub, which is a bit different than the usual high level connection: they have a special cable that gets connected to the main amp, right where the speakers gets connected, in order to receive full signal from the amplifier.

Jinhan, do you mean I should place the sub close to the sofa where I sit (sweet spot) and move around the room until I find the best sounding place?

I finally got an email from REL distributor in USA to reply to my inquiry (see below). Do they suggest I cross it over at around 25 HZ, or I read it wrong??!!!

In reply to:

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Hello,

Thank you for your interest in REL. The best thing to do is to follow the four-step setup procedure outlined on our website, listed below, under REL / Owner's Manuals / REL Setup guide. This will get you to the right position and at the right settings. There is no "right answer" since room acoustics will affect the position of the controls. However, a good guess, based on a lot of experience, is that the crossover will be somewhere in the mid to high 20 Hz range, as the REL will play above the crossover point as well as below.

Sincerely,

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Basically, the website instruction, as well as REL manual let you set it up with ear and NO recommendations on numbers are made at all.

Yes, Skerdi, that's what they're suggesting. I hesitated in replying here because I've read the REL literature and simply didn't accept their rationale. They urge using the sub to just reinforce the very bottom of the bass range, but my thought is to disregard their advice and use the line level connection(rather than their special high level connection)and set a crossover somewhere in the 60-80Hz area in the receiver, setting the REL crossover to bypass.

Thanks John for the advice. I still have to experiment with the strange REL suggestion. Who knwos, it will probably work...

As for the receiver, I don't have one, my system is a two channel system with a preamp that does not have bass management whatsoever.

I got another email from REL distributor in USA, now he starts to make more sense:

In reply to:

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The REL is connected at High-level, which means you use the crossover in the REL, not the bass management features in the preamp. The REL is connected to your power amp. The REL connector attaches to the same binding posts to which your speaker cables connect (they share the binding post). The REL crossover plays above the crossover point. If you cross over at 25 Hz, it will play above 25 Hz, just as your speakers will play below 37 Hz (though possibly not at an audible level). The idea is to match the rolloff of the REL with the rolloff of your main speakers. This is done by ear; there is no need to concern yourself too much with the crossover point; I am simply stating that, in my experience, the REL is crossed-over around 25 Hz the overwhelming majority of the time when used with floorstanding speakers. If you follow the setup procedure outlined in our REL Setup guide, you will arrive at the proper crossover point.

Best,

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Comments???

I have heard about some good bass management units such as This one, or, a unit mentioned in this forum as well, Outlaw ICBM. I wonder if they are worth it. Besides, shouldn't I be able to get a satisfying level of bass by the subwoofer alone?

Have you been able to get the sub dialed in to what you think is acceptable? From what I have read on this subject it seems to me Rel flies in the face of conventional thought. If it were me I would try the low level input and crossover the M60s in the 60Hz range. If the 60s are +/-3dB (Hz): 37 - 22 kHz and +3dB- 9dB (Hz): 27 - 22 kHz why would you want to have the crossover at 25Hz. To me it would seem there would be a hole in the lower part of frequencies where the M60s leave off and the Rel (set to 25Hz) picks up. If you can try to do some frequency sweeps and see what you come up with

I hate to play devil's advocate here, but I think Rel is advising the right thing for a pure music system. No matter how much I tweak the crossover freqs and sub levels, I still prefer the sound when I have few crossovers as possible between me and the music. Parking the subwoofer down at where the main speakers roll off does the least "messing around with the sound" and would probably be my preference for music.

Trouble is that for some reason I also much prefer movie playback with a traditional HT setup -- 80 or 100 Hz crossover, speakers set to small, bass management via the receiver, yadda yadda.

Don't write off what Rel is saying, but as everyone else on the board is saying remember it isn't the only way to operate; try 'em both and see which you prefer.

In reply to:

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Parking the subwoofer down at where the main speakers roll off does the least "messing around with the sound" and would probably be my preference for music.

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My question would be, what good does it do to set the crossover so low (25Hz) when the M60s are only rated down to 37. Would it not be better to set the crossover to a setting that would be before the 60s starts to roll off.

It looks like the Rel instructions advise to set the LPF to a very low value (22 or 25 Hz) and work your way up from there. Just guessing.. .agree that 25 Hz is probably way too low for most mains including M60s.

If you want to read something else and still be confused, I offer this detailed, encouraging but still confusing review :

http://stereophile.com/subwoofers/1004rel/index1.html

I read the Stereophile article and there was nothing there to expain the "why" such a low setting. It was not a very informative piece.

Agreed. I was surprised how such a seemingly well written article could be no help at all.

Starting from a very low crossover setting, around 25 Hz and moving up until finding a desirable level makes a lot of sense. In fact that is exactely what REL manual suggests. However, REL distributor clearly states that:

In reply to:

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in my experience, the REL is crossed-over around 25 Hz the overwhelming majority of the time when used with floorstanding speakers.

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That is the part that I don't understand. I tried it yesterday at around 25: you could hear the sub when increasing the high-level volume knob all the way up. However it sounded a little weird, and kind of out of phase. I'll give a few more hours (days) at that setting.

I was reading the owners manual and it states the in room response for the 150 as -6db @ 19 Hz. On the Rel site it says the frequency response for the 150 is 30 to 100 Hz. It looks to me that the 150 will not have very much info when set to 25 Hz. So if these are the correct specs why in the world would they tell you to set the crossover @ 25?


BTW what type of music are you listening to?

I think the Rel instructions are only thinking of stereo systems with full-range floorstanding speakers, not AV systems with smaller center and surround speakers.

It's possible that the crossover setting on the Rel subwoofer isn't actually the 3dB point but more like "the lowest frequency the mains can handle" then the actual -3dB point is somewhat higher than the number the dial is pointing to, eg. if you set to 25 Hz the -3dB point might actually be 40-50 Hz. Just a guess though.

Isn't REL's suggestion the way subwoofers used to be used way back before home theater? I am a big believer in higher crossovers, but I do see where they are coming from.

I bought an M&K subwoofer long before home theater was popular.I recall them saying to set the crossover to the - 3 db point of the mains. They also said if a person did not know what this spec was to set the sub to 85Hz.

The real beauty of our bass management systems that we put so much faith in, is the fact that we just KNOW that all the sonic information recorded on our CDs or DVDs or whatever, is going right to our subs along with the LFE stuff, no matter what.

That all that center channel data below 80hz or so is going right to our subs if 80hz is our crossover setting. That our surround sound data below 80 is doing the same all the time.

We just know that not one cycle of info is being lost.

We know, cuz it's set up that way! Right??




It's also a blessing that our subs all sound just as good as our mains.

I mean; we sure wouldn't want to be giving so much responsibility to an inferior sounding transducer.

Rick, I listen to several genres of Metal mostly, but other music as well sometimes (easy listening). Bass, especially tight, fast and accurate bass, is an important feature at my music as well.

With the type of music you listen to do you really get that much info from metal that goes to 20 to 25 Hz. It would seem that a higher setting would serve you well.