Pros/Cons of Shallow/Steep Crossover Slopes

[solacedagony]

Just wanted to get some opinions on where and when to use steep or shallow crossover slopes. Do they have specific applications or is it more play around and see what you get? I noticed that my sub seem to sound better w/ a 24db slope @ 80hz.

[JeremyC]

I normally try to use a 24 with subs. IMO its better to cut them off, and let the mids take over.

I set the mids HPF with as low a slope (as long as its over 12) (more info on that in a min), and x-over point as low as I can without going below the speakers capability, or causing to may rattles in the door panel.

The rest of the system I use 12 db unless I need to boost an area to achieve a flat response curve. That’s the main point of a x-over (other than keeping your speakers from playing more than they can handle), to balance the system, and keep from getting a huge spike where the speakers blend together.

Here is the rest of the info on the 12db slope. Speakers tend to roll of at 12dbs anyways, and anything 12dbs or higher cuts the output enough that the speaker will never pass the excursion set at the x-over point.

[basicxj]

For example, let's say your front component speakers play nicely down to 60 hz with most music you listen to, and you are using a 12dB/octave slope on the crossover point of 60hz. Let's say you have your sub crossed over at 80hz, and are using a crossover slope of 6dB/octave as well.

Now with those settings, you notice the higher frequency bass output of your sub is a little muddy, so you cross it over at 60 hz as well. You now notice that some musical information you were getting before is lost with the new crossover setting on the sub, and just to make things interesting...you notice now that your components are bottoming out a touch, distorting at the same 60hz crossover setting at higher volume levels.

One way to limit the lower frequency output of your components (yet not toss out too much midbass your sub can't provide) is to use a steeper crossover slope, say 18 or 24 dB/octave. Your components will still play the lower fundamental tones and blend nicely with your sub, but won't see as many fundamentals/harmonics of the lowest frequencies seep through at the steeper slope. This is good, because you're not tossing out some musical information like using an 80hz crossover point would do, but you are keeping a little more of the lower bass frequencies out of the components that was causing them to bottom out and distort at higher volume.

The same slope adjustments can also be applied to your subwoofer crossover. If bass response becomes muddy near the upper limit of your crossover frequency, a steeper slope might clean it up sufficiently so you can have the sub play a little higher than you normally would. This is good if you are running smaller size speakers for your front stage, and by virtue of their limited midbass response want to reproduce what they are lacking with your sub.

I usually try to have my front stage play as low as physically possible (without anything distorting at the volume levels I typically listen), and cross my sub over as low as possible while still reproducing most of the frequencies. This keeps midbass up front in the sound stage and prevents localizing the source of the subwoofer (and pulling part of the stage rearward). Playing with your crossover slopes gives you added flexibility with your crossover points to accomplish this.

[solacedagony]

So it'd prob be good for me to borrow someone's laptop and measure my FR once I set everything up active and see (for my crossover slopes and EQ) where my peaks and valleys are.
Thanks for your replies guys!

[JeremyC]

The only other thing I would like to touch on (after what basic said) is the need for some gap between x-over points. This area is just as important as slope. You need to alow for a gab between where the sub starts to roll off, and where the mid starts to roll off.

IE sub set to 60 herts, and the mids set to 80 or 100 herts.

This gap will allow all 3 or 4 speakers to play the same section of freqs without creating a huge peak in the responce curve. If you don't have a gap, or cross your sub over at a higher point that your mids, you will end up with a huge peak.

[GlassWolf]

entirely depends on the speakers, placement, and application

[solacedagony]

entirely depends on the speakers, placement, and application

That's what I assumed, but I wanted some kind of answer as to if there was generalities or that is one of those install-specific things.

[basicxj]

That's what I assumed, but I wanted some kind of answer as to if there was generalities or that is one of those install-specific things.

Definitely install specific.

Your xover slopes depend on the frequency response of the drivers in your system, your type of enclosure (components in an infinite baffle mount in doors/kicks or sealed in pods, sub in a ported or sealed enclosure etc.) as well as program material you play through them to a degree.

Without something like an RTA (or a head unit with an auto-EQ and mic), your ears will tell you where your peaks and valleys in frequency response are. Some installs absorb a big chunk of the frequency spectrum and some installs have peaks in certain frequencies due to interior materials/surfaces and speaker placement. A good EQ and electronic crossover with variable slopes can tame a lot of these anomolies and give you pretty good SQ in less than optimal circumstances (like typical installs in most cars).

[basicxj]

The only other thing I would like to touch on (after what basic said) is the need for some gap between x-over points. This area is just as important as slope. You need to alow for a gab between where the sub starts to roll off, and where the mid starts to roll off.
IE sub set to 60 herts, and the mids set to 80 or 100 herts.
This gap will allow all 3 or 4 speakers to play the same section of freqs without creating a huge peak in the responce curve. If you don't have a gap, or cross your sub over at a higher point that your mids, you will end up with a huge peak.

The crossover settings in that example were purely theoretical.

If you're tuning for a perfectly flat system frequency response, it's a safe bet to leave a gap between your HP and LP crossover settings.

If you are running a 6 1/2" midbass (or larger) in your front stage, you'd very likely want a gap between your HP and LP crossover settings, to cut down on cancellation in the frequencies shared between midbass and sub drivers. For those using 5 1/4" or smaller drivers up front, they'd likely notice a valley in frequency response unless there were some overlap in frequencies between mids and subs.

If you're tuning to suit your particular ears and music preferences, you may well end up with some overlap between frequencies produced by your midbass and those produced by your sub- regardless of speaker size. It really depends on what sounds best to you. Some people prefer a system with boosted response in the highs/lows for everyday listening, but would never dream of competing with those same settings.

[GlassWolf]

generalizing?
subs I tend to cross over more steeply, and use midbass or mids to roll off to the subs.
with mids and tweeters, the shallower the slopes, typically the smoother the transitions and better the SQ turns out, but the downside is that the speakers get hellishly more picky about beaming and directionality, their power handling drops significantly, and there are a few other issues. A steeper 12-18dB slope for mids/tweeters tends to make the install a lot easier, lets you throw more power at the speakers, and really works out nearly as well.
My Dyns use a 6dB slope, and it makes things difficult at times with installs.