Choosing Crossover Slope

[jcisbig]

Hey All,

Is there any sort of logic that should be used in determining when to use 12dB or 24dB for your crossover slope, or is it just whatever sounds best to you?

If it's a "whatever sounds best" type scenario, does anyone have a couple good examples of songs that can be found on Spotify that would help determine what sounds best? And include a short description of what to listen for at what time during the song?

Thanks!

[Chuck Elliot]

You’re going to get answers that are all over the board on this one. Some prefer lower slope crossovers, while others like steep slope crossovers.

As a general rule, it will depend on your drivers to a large degree too. That and the frequency selected.

The major goal is to transition between the two drivers without any bumps or dips when the signal from both drivers acoustically sums.

I don’t think that a selection of music is going to help you much to determine this. A measurement microphone and software will tell you much more easily.

Keep in mind one thing. The slope of both sides of the crossover may not be symmetrical. If the woofer is already rolling off at the crossover frequency due to other factors, then the woofer crossover may need to be set at a lower slope than the sub.

[TKO]

Sept 15, 2013 22:21:17 GMT -5 jcisbig said:

Hey All,

Is there any sort of logic that should be used in determining when to use 12dB or 24dB for your crossover slope, or is it just whatever sounds best to you?

If it's a "whatever sounds best" type scenario, does anyone have a couple good examples of songs that can be found on Spotify that would help determine what sounds best? And include a short description of what to listen for at what time during the song?

Thanks!

Hi,

you can find a good technical understanding of what happens at the crossover in Dr. David Rich's review of the Anthem Room Correction (ARC) System - Including a Subwoofer.

Hope this helps.

Cheers.

[garbulky]

What exactly are you trying to do? The answer differs depending. Subwoofers? DIY speaker crossovers? Room correction?

[KeithL]

I can give you a real easy answer:

When you listen to music, you are NOT supposed to "hear the speakers". The sound should just sort of appear in the room, coming from the correct direction, and sound right. The goal of any speaker, or SET of speakers, is to "disappear". Specifically, when you add a sub, you should NOT be able to "hear the sub" AT ALL! There should be more bass (or, more correctly, the right amount of bass), but you shouldn't hear the sub itself, and you shouldn't be able to hear when the sound "shifts" from the main speakers to the sub. And THAT is your answer: the best sub to go with your speakers, and the best position for that sub, and the best crossover setting for that sub will be the ones where it disappears and all you can hear is the music.

As with everything in life, this involves a tradeoff. The more you overlap the area where both the sub and the main are working (a shallower - lower dB/octave - crossover slope), the more gradual the transition between them, and possibly the smoother the transition. However, the wider the overlap, the more likely it is that they will NOT blend smoothly, or that you will get interference between them in a particular room. A sharper slope, with a faster and narrower transition, will be less likely to have interference between the sub and the mains, but will make it more likely that you will hear the "dividing line" between them. When you choose a sharper slope, it is also more likely that the crossover filter itself will cause more problems (like phase shift), because that's simply the nature of filters - the sharper they get the more they mess with the sound. You get to choose the one that works best in your particular situation. The best choice also involves the nature of the speakers themselves.

The very basic theory suggests that the two filters should be similar in slope (symmetrical), so their outputs "sum to flat"; however, in the real world, this often isn't the best solution. Many large main speakers can go quite low and still produce clean bass; so, for them, a shallow high-pass filter is a good choice. But many subs don't really produce very clean sound at higher frequencies, and it's much easier to hear where sound is coming from above about 100 Hz (and, technically, the sound coming from the sub is NOT in the "right" place); so, for THEM, a sharper low-pass filter is a good idea.  (Many systems end up being configured with a 12 dB/octave filter on the mains and a 24 dB/octave filter on the sub for this reason.)

Sept 16, 2013 8:04:18 GMT -5 garbulky said:

What exactly are you trying to do? The answer differs depending. Subwoofers? DIY speaker crossovers? Room correction?

[jcisbig]

Thanks for the replies guys!

It sounds like some experimenting is in order whenever you are setting up a system, but the end result is to achieve as "flat" of a transision as you can between the mains and sub(s). Measuring this will be the best way to ensure that you have succeeded, but you should be able to confirm proper settings by ear as well, at least to a minimal degree. Setting a successful crossover slope would result in a smooth transition (inaudible) between the mains and subs, and would cause the sub to "disappear" in the room. Have I got all that right?

If so, these might be different options to try?
1) Choose a CO slope of 12 dB
2) Choose a CO slope of 24 dB
3) Try different crossover points between 40hz and 80 or 90 hz, depending on your speakers/sub (keep the CO and slope the same)
4) Try different crossover slopes for the mains and subs
5) Try different crossover points for the mains and subs

Are there other options than those? Are there some above that shouldn't be tried?

As you can see in my signature, I've got Aperion Verus Grands for my mains and an HSU VTF-15H for my subwoofer. To me, they both seem like pretty capable pieces of audio equipment. I've been having difficulty getting my sub to really blend well with my mains, to my ear it's just too easy to tell where the sub is positioned in the room. I'd love to be able to get it to disappear completely! But it's bothered me so much that I've been listening to my music with just the mains and no sub quite a bit, but I'm missing a chunk of low end when I do that. Diana Krall and similar is fine that way, but as soon as I play some music with substantial low end (below about 40hz or so) I really do need the sub in the mix. Any ideas or thoughts on where might be a good place to start with messing with the crossover stuff? I've tried same slope at 80hz, 75, 60, and 40. Some are better than others, but it's no where near perfect yet.

I will hopefully be getting a UMC-200 soon, when that happens I can pick up a UMIK-1 and begin to EQ the sub properly, and that might help quite a bit too!

[TKO]

Sept 16, 2013 10:34:56 GMT -5 jcisbig said:

Thanks for the replies guys!

It sounds like some experimenting is in order whenever you are setting up a system, but the end result is to achieve as "flat" of a transision as you can between the mains and sub(s). Measuring this will be the best way to ensure that you have succeeded, but you should be able to confirm proper settings by ear as well, at least to a minimal degree. Setting a successful crossover slope would result in a smooth transition (inaudible) between the mains and subs, and would cause the sub to "disappear" in the room. Have I got all that right?

If so, these might be different options to try?
1) Choose a CO slope of 12 dB
2) Choose a CO slope of 24 dB
3) Try different crossover points between 40hz and 80 or 90 hz, depending on your speakers/sub (keep the CO and slope the same)
4) Try different crossover slopes for the mains and subs
5) Try different crossover points for the mains and subs

Are there other options than those? Are there some above that shouldn't be tried?

As you can see in my signature, I've got Aperion Verus Grands for my mains and an HSU VTF-15H for my subwoofer. To me, they both seem like pretty capable pieces of audio equipment. I've been having difficulty getting my sub to really blend well with my mains, to my ear it's just too easy to tell where the sub is positioned in the room. I'd love to be able to get it to disappear completely! But it's bothered me so much that I've been listening to my music with just the mains and no sub quite a bit, but I'm missing a chunk of low end when I do that. Diana Krall and similar is fine that way, but as soon as I play some music with substantial low end (below about 40hz or so) I really do need the sub in the mix. Any ideas or thoughts on where might be a good place to start with messing with the crossover stuff? I've tried same slope at 80hz, 75, 60, and 40. Some are better than others, but it's no where near perfect yet.

I will hopefully be getting a UMC-200 soon, when that happens I can pick up a UMIK-1 and begin to EQ the sub properly, and that might help quite a bit too!

I think you will drive yourself insane trying to do this without any measuring tools etc. but if you want to start down that road...

The Spears & Munsil HD Benchmark 3D Disc 2nd Edition is a very useful, and accurate, way to tune your whole system, and has specific audio files to assist with crossover settings, phasing etc.

Hope this helps.   Cheers.

[garym]

If your mains are capable down to 40 Hz, you might try crossing at that point. Frequencies become less locatable the lower you go. That may leave a "hole" in the response from your surround channels, though (if you're using the sub for all channels).

[jcisbig]

Garym,

I've noticed that on my UMC-1 you can set individual crossovers for the mains, center, surrounds, and sub. In such a case, would there be a way to cross over the mains at 40hz whilst still allowing the sub to play the bass for the center and surrounds at a higher crossover point?

Asked another way, I guess I'm asking what's the point of having a separate crossover for the subwoofer? Would there ever be a situation where you would want your sub crossed over at something different than wherever your mains/center/surrounds are crossed over?

[KeithL]

The individual main speaker crossovers determine at what frequency bass for each speaker is instead routed to the sub (any bass not routed to the main speaker for each IS routed to the sub). In addition to bass from the main speakers, your sub is also receiving bass from the LFE (low frequency effects) channel. The sub crossover really sets the high frequency cutoff ONLY for this. The only purpose it serves is to "cut off" any high frequency noise on that LFE channel. Otherwise, simply leave it set at the highest setting and forget about it.

Sept 16, 2013 13:36:36 GMT -5 jcisbig said:

Garym,

I've noticed that on my UMC-1 you can set individual crossovers for the mains, center, surrounds, and sub. In such a case, would there be a way to cross over the mains at 40hz whilst still allowing the sub to play the bass for the center and surrounds at a higher crossover point?

Asked another way, I guess I'm asking what's the point of having a separate crossover for the subwoofer? Would there ever be a situation where you would want your sub crossed over at something different than wherever your mains/center/surrounds are crossed over?

[jcisbig]

Thanks for that info Keith!

[LCSeminole]

Sept 16, 2013 10:34:56 GMT -5 jcisbig said:

I will hopefully be getting a UMC-200 soon, when that happens I can pick up a UMIK-1 and begin to EQ the sub properly, and that might help quite a bit too!

A MiniDSP UMIK-1 and REW will most certainly help in using the P-EQ in a UMC-200 to clean up any muddiness in the subwoofer channel. You'll be amazed at how well it will blend your mains with your subwoofer.

[xki]

As Keith describes, the purpose it to make the transition 'invisible'. Let's take an example and I'll throw in my personal experience to make this as plain as I am able.

My mains are rated down to 53hz. They can go lower but at a much lower level. I would say they produce down to 45 at - 12db from 53hz.

I tried the subs at many different positions. I could still hear where they were. Not good. I tried different crossover points and slopes. Movies were fine.... music was terrible. So, I kept trying.

One day I moved the mains in about 2.5 feet and placed the subs just outside the mains. Mind you, the subs were now in the corners of the room. The sound was very boomey. Obviously, the room itself was causing this. I kept the subs just outside the mains and EQ'd the boom out. Now this was getting better.

The next thing was to set the cross over. This wasn't as easy as I thought. That's because I set the slope to 24db and tried from 80 down to 40hz. 60 was OK. So was 50... so was 40. However, I could still hear the subs when the transition occurred. Yuck! (On board sub cross over set to ~100db - Sub cross over on the UMC set to the same as the mains.)

It dawned on me that the roll off of the mains was probably pretty steep. I verified this at the other forum. What was happening at 24db slope was that the mains were being dropped off quicker than the subs were picking up the lower end sent via the cross over. This left a 'hole' in response between ~47db down to 40db. This with the cross over at 50hz. So....

I set the slope to 12db and the hole was gone. Also, since the subs are right next to the mains, the transition is localized near the mains and I don't hear the subs any longer. Yea!

Of course there are down sides to having 2 subs in a 7.1 setup set next to your mains. 1) Both subs are fed the same source so any stereo low frequencies are now smeared across the entire front instead of L/R. (UMC-1 x.1 sub feed) and 2) the tonal matching of subs to mains is really never quite matched when you have 40 year old mains.

I have been able to compensate for these down sides and get to the point where I can't tell where the speakers are sometimes. All things considered, this was the easy part. It was the dual centers cross over, EQ, and slope that really drove me nuts for a year!

As for songs to try, look to most of Jordan Rudess tracks. His solo stuff has all the low end you will need to test the theories and set your slopes. Planet-X is another good one. I'm sure others have more recommendations that surpass these.

[Chuck Elliot]

Sept 16, 2013 20:42:06 GMT -5 xki said:

....It dawned on me that the roll off of the mains was probably pretty steep. I verified this at the other forum. What was happening at 24db slope was that the mains were being dropped off quicker than the subs were picking up the lower end sent via the cross over. This left a 'hole' in response between ~47db down to 40db. This with the cross over at 50hz. So....

I set the slope to 12db and the hole was gone. Also, since the subs are right next to the mains, the transition is localized near the mains and I don't hear the subs any longer. Yea!
....

This is exactly an example of the need for an asymmetrical crossover in some cases as I explained above. The actual output is a function of what the electrical crossover is doing AND the roll-off characteristics of the driver in its enclosure.

[xki]

Sept 16, 2013 20:52:02 GMT -5 Chuck Elliot said:

Sept 16, 2013 20:42:06 GMT -5 xki said:

....It dawned on me that the roll off of the mains was probably pretty steep. I verified this at the other forum. What was happening at 24db slope was that the mains were being dropped off quicker than the subs were picking up the lower end sent via the cross over. This left a 'hole' in response between ~47db down to 40db. This with the cross over at 50hz. So....

I set the slope to 12db and the hole was gone. Also, since the subs are right next to the mains, the transition is localized near the mains and I don't hear the subs any longer. Yea!
....

This is exactly an example of the need for an asymmetrical crossover in some cases as I explained above. The actual output is a function of what the electrical crossover is doing AND the roll-off characteristics of the driver in its enclosure.

Yup. As you said, "Keep in mind one thing. The slope of both sides of the crossover may not be symmetrical. If the woofer is already rolling off at the crossover frequency due to other factors, then the woofer crossover may need to be set at a lower slope than the sub. "

Agreed and I've lived it!