# Very steep crossover slopes.



## Imagewerx (Nov 30, 2012)

We're talking about 48 db/octave steep here.Is there anything wrong with going this steep? 

It means I can run my horns down to 700 Hz without any problems.My midbass come in at 60 Hz @ 48 db/octave,but without the sub it doesn't sound as if there's any REAL hard hitting midbass there.They're each in about a 6 litre sealed box that needed a LOT of e/q between about 100 and 150 Hz to get them sounding half decent.

Yes I know the best way to find out this sort of stuff is to jump in my car and try it,but it's England and it's cold and it's raining as apparantly it has to do over here.

So hit or miss for brick wall filtering?


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## BEAVER (May 26, 2007)

I don't have any technical data to spew, but I'll just say that I've noticed with my own set-us that steeper slopes have a tendency to not blend as well and often sound dull or lifeless.


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## ccapil (Jun 1, 2013)

Altering the slope affects the phase alignment of the drivers being crossed together. Crossover slopes will also affect off-axis response of tweeters, which will also change the way the whole system sounds. By using a steeper slope, you increase the rate its attenuated. So at 700hz @48db per octave slope HPF, at one octave higher( 1400 hz) the sound will be 48db less as loud, which is a lot! You won't even hear it). I would start with a shallower slope around 18 or 24db / oct. 
I tend to use shallower slopes when applicable.Also, I prefer to use slopes that are "in phase" like 24 and 48db. 6db is 90 degrees out of phase. 12db is 180, 18 is 270 degrees out of phase. 48db slope is like a cliff and you may find imaging or frequencies not rolling off smoothly.


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## 14642 (May 19, 2008)

There's no real practical difference between 24 and 48dB/octave. 

Let's say your amp puts out 100 watts. -24dB would be .3525 watts. -48dB would be .00062 watts. Yes, one is steeper, but for what purpose?


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## Imagewerx (Nov 30, 2012)

Thanks for the answers so far guys,does anyone else have anything to add to the subject please?


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## ATOMICTECH62 (Jan 24, 2009)

Higher slopes cause ripple(ringing).Cant say Ive heard this effect,but when designing crossovers on TI's Filter Pro it is something that is taken into consideration.It also makes a difference what type of slope is being used.Bessel and Butterworth have less ripple then Cheb's do.But I believe this because Cheb's are designed with a faster cut off rate.

I have used slopes up to 36db/oct and never had good results.I have found that staggering slopes work well.Since car speakers are hardly ever on the same time axis and the reflections are massive,experimentation is a must.I usually start with all slopes at 12db/oct then play with them individually.Speaker roll off has a lot to do with it also.I know my 2" domes roll off about 12db naturally above 5khz so if I cross them LP 12db/oct at 5khz I have about a 24db/oct slope on them.Since there is a protection Cap on the tweeters if I cross them HP at 18db/oct I now have something like a 24db/oct slope.Well,not exactly but close.


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## knever3 (Mar 9, 2009)

Sony XES uses to use 72dB/octive, USD was 48dB/octave, nice if you are putting a ton of power into a speaker that doesn't like to play down that low, but only your tweeters will care. The wow factor is pretty much what is to gain. Just a matter of preference, yeah it's cool but I would say if it sounds good go for it because that's all that matters in the end.


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## thehatedguy (May 4, 2007)

USD was 24 dB...just a converted Rane AC23.


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## Imagewerx (Nov 30, 2012)

ATOMICTECH62 said:


> Higher slopes cause ripple(ringing).Cant say Ive heard this effect,but when designing crossovers on TI's Filter Pro it is something that is taken into consideration.It also makes a difference what type of slope is being used.Bessel and Butterworth have less ripple then Cheb's do.But I believe this because Cheb's are designed with a faster cut off rate.
> 
> I have used slopes up to 36db/oct and never had good results.I have found that staggering slopes work well.Since car speakers are hardly ever on the same time axis and the reflections are massive,experimentation is a must.I usually start with all slopes at 12db/oct then play with them individually.Speaker roll off has a lot to do with it also.I know my 2" domes roll off about 12db naturally above 5khz so if I cross them LP 12db/oct at 5khz I have about a 24db/oct slope on them.Since there is a protection Cap on the tweeters if I cross them HP at 18db/oct I now have something like a 24db/oct slope.Well,not exactly but close.


Hopefully with my simple 3 way/5 driver system there's less room for errors caused by over correction,and my low mounted horns should mean reflections won't be a problem for my installation.


knever3 said:


> Sony XES uses to use 72dB/octive, USD was 48dB/octave, nice if you are putting a ton of power into a speaker that doesn't like to play down that low, but only your tweeters will care. The wow factor is pretty much what is to gain. Just a matter of preference, yeah it's cool but I would say if it sounds good go for it because that's all that matters in the end.


I was previously crossing over at 1000Hz @ 18db/octave and they were JUST starting to suffer.Now 300 Hz @ 48 db/octave lower and they play a lot cleaner and the bass localisation has moved forward.That bit is fine now,it's just the sub to midbass I've got to play with,I should easily be able to come down to 50 Hz or maybe even a bit lower I reckon.

So,any one else got anything to add to this please?


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## SPLEclipse (Aug 17, 2012)

It's very easy to push a midbass driver beyond it's mechanical capabilities by using a steep slope at a lower point than the other way around, so be careful. I've also found it easier to blend the stage with a shallower slope, but that's in a no way a scientific statement.


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## Justin Zazzi (May 28, 2012)

It's all about tradeoffs. Steeper slopes cause some artifacts such as ringing (the steeper the slope, the more ringing), but shallow slopes require the speaker to play wider bandwidth. Some particular alignments such as the Linkwitz-Riley 4th order (24db/oct) cause the high-pass and low-pass elements to sum at 360 degrees out of phase, which is essentially in phase. Most other alignments require some other manipulation to arrive at this result.

Keep in mind, all crossover alignments are specific to the acoustic performance of the system. So if you have a sealed enclosure (with a natural 12db/oct rolloff) and you couple it with a 12db/octave electronic or passive crossover, the acoustic response will be 24db/octave (because they add together).

I think the answer to your question about midbass is to boost the midbass frequencies from about 250hz (+0db) all the way down to your subwoofer's frequencies near 30hz (+12db or more). The trick is to make a smooth and gradual increase in bass from the lower midrange all the way through the sub-bass frequencies. Look for information about "house curves" to learn more about this.


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## Hanatsu (Nov 9, 2010)

4th order L-R acoustic responses tend to work best imo. I see very little reason in using slopes below 12dB/oct or above 24dB/oct. I generally use whatever slope, crossover frequency and Q available to the shape the acoustic response to my liking.


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## FG79 (Jun 30, 2008)

You guys kill me with your 24 and 48 dB slopes. That stuff should be reserved for the SPL crowd or perhaps the pro audio scene.

18 is ok, but I much prefer 12 and 6. 

Some people have issue with 6 over supposed phase issues, but I don't see the issue in the real world. Many good home speakers use 6 dB slopes. 

I would much rather raise the crossover point and go 6/12 than go super low with steep slope.

With a good amp you'll never need more than 12 or 18 for a midbass HPF. I like to protect dome midranges with 12 usually. If I do a high crossover blend between dome mid and tweeter, always 6. 

If it weren't for how loud we play car systems, I'd probably go 6 dB all the way. 12 dB is the best all around slope IMO.


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## Hanatsu (Nov 9, 2010)

FG79 said:


> You guys kill me with your 24 and 48 dB slopes. That stuff should be reserved for the SPL crowd or perhaps the pro audio scene.
> 
> 18 is ok, but I much prefer 12 and 6.
> 
> ...


I guess you haven't seen this thread?

http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/155959-essque-vs-danger-6db-slopes.html


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## Hanatsu (Nov 9, 2010)

I fully agree with this statement;



bikinpunk said:


> If for no other reason than avoiding additional combing issues outside the passband and between speakers, I don't believe shallow slopes have a place in car audio.


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## therapture (Jan 31, 2013)

Hanatsu said:


> 4th order L-R acoustic responses tend to work best imo. I see very little reason in using slopes below 12dB/oct or above 24dB/oct. I generally use whatever slope, crossover frequency and Q available to the shape the acoustic response to my liking.


So how in the world did I end up with 48db/L-R?  I wonder if that is the reason I seem to have a hole around the crossover point between my mid and sub...if I went to a 24db slope it seems that that is right where the additional overlap occurs and would "fill in" that gap...

Time to head back to the laptop.


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## T3mpest (Dec 25, 2005)

Hanatsu said:


> I fully agree with this statement;


Third.. Cars are hard enough acoustic environments as is, without having to deal with with each speaker sharing half an octave from different locations. Plus it's a car with road noise, wind noise when the windows are down, etc, I want to know I can safely play any music at any volume and be safe.


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## FG79 (Jun 30, 2008)

Hanatsu said:


> I guess you haven't seen this thread?
> 
> http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/155959-essque-vs-danger-6db-slopes.html


I used to get caught up in the mentality that a PhD's worth of knowledge is important for good sound, but learned quickly that's not the case. More knowledge is often worse, because you become brainwashed by theory instead of what you hear.

All this theory sounds good, but we've yet to properly bridge the gap between science and art as it pertains to sound that is good and pleasing. 

It's ironic that double blind testing is supposed to be the most objective scientific method of comparison, but the only thing the listener can draw is subjective evaluation.

Steep slopes are great for power handling and playing really loud but I haven't heard a 24 dB system sound as natural as a 12. 

The 6 dB thing is nice when doing a top end blend with a mid and a super tweeter. A supertweeter at 10,000 hz being high passed with a 48 dB crossover would be ridiculous. 

Home audio has better execution of 6 dB crossovers than car because their drivers often have better bandwidth, and when you compare efficiency and noise floor you have more headroom to work with. 

In re-reading the OP from the link you sent me, one wouldn't want to high pass a tweeter @ 2-3 khz with a 6 dB slope, but at 5-6 khz it makes a lot more sense. Most car audio woofers in a 2 way setup cannot play flat beyond 3 khz despite what the specs may say (my current 7" midbass has crossover set at 5700 hz from the factory.....sounds better at 3000 hz). So now you have a tweeter that will be playing unnecessarily low, and in a car where you tend to crank up the volume....it's a problem.

My original premise isn't "6 dB in every driveway", but that this obsession with a million dB crossover is very, very misguided. 

Digital is supposed to be better than analog, and solid state better than tubes if you pull up enough theory. But my ears have told me otherwise. 

I'm an Electrical PE (Professional Engineer) by the way in case you think I'm the average layperson trying to be a contrarian for the fun of it.


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## cajunner (Apr 13, 2007)

cue the contrarian layperson here, but I like 6 db slopes.


I like them so much, that I've even thought of crossover designers as having way too much time on their hands, and I like them in commercial products that cost half of their super-duper high end counterparts, and when I read about Thiel and Dunlavy and those guys, Fried and Spica and Dynaudio and using drivers with huge linear passbands and quality through and through, I enjoy the option to be "phase-coherent" and whatever buzzwords sound good, since I remember my audio beginnings as a 6 db guy, and lower cost products.


It does go back to 'sound power' though, and maybe not the way you think I mean it, I mean how much sound power is necessary that you are roasting tweeter coils unless you're doing 12 db/octave, you're up there in the DEE beez.

Anyone can enjoy a sound system cranked halfway up, nowadays and not have to tear into it, and 6 db crossovers are capable of doing their work at those levels. When I go steep, it's not because I find my drivers "blend" better, because they really don't. I'm doing it so I can crank it up, and not worry about stressing the mid-fi driver quality I'm able to afford, I do it because I like to play around with polar responses and adjusting for driver plane/orientation, I do it because there's no cost involved with the DSP selector switch like when designing passives, there's no real penalty.

but at listening levels that my parents like, 6 db is plenty good.


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## Justin Zazzi (May 28, 2012)

FG79 said:


> You guys kill me with your 24 and 48 dB slopes. That stuff should be reserved for the SPL crowd or perhaps the pro audio scene.
> 
> 18 is ok, but I much prefer 12 and 6.


...and...



cajunner said:


> cue the contrarian layperson here, but I like 6 db slopes.


Assuming you are both talking about electronic and passive crossovers (not acoustic response), consider this:

Sealed and infinite baffle enclosures have a natural 2nd order rolloff (12db/octave), and vented boxes have a natural 4th order rolloff (24db/octave). Keeping in mind that electronic and passive crossovers combine with the acoustic response of the speakers, then both of you are saying that you prefer a 3rd or 4th order acoustic response, right? (natural acoustic response of 12db combined with 6db or 12db crossovers)

So, aren't we all trying to say the same thing? It's the acoustic rolloff that counts, not the electric. To get a 6db/octave acoustic rolloff, you would have to build a sealed or IB enclosure and then have the *inverse* of a 6db/octave filter on top of that. Seems hard to do, doesn't it?


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## Imagewerx (Nov 30, 2012)

Thanks for all the answers so far guys.I should have said in my first post that I'm not competing with my car so this is purely for my own listening pleasure when I like it just loud enough to not need to worry about hearing and driver damage.It doesn't have to have perfect imaging (but it is pretty good anyway),I do like good dynamics more than anything else and it has to be able to play loud for long periods with minimal risk.
I don't have the luxury of being able to play with driver placement in the front of the car as a lot of people do.My horns will always be at the bottom of the dash,my midbass will always be in small sealed boxes either side of the back seat and my sub will always be in the boot.Hence the reason for an all singing and all dancing DSP that helps me to get the best from what I'm stuck with.
The midbass to horns 48 db L/R slope was chosen because it sounded better than the others to my ears,but I did have real trouble with the under 200 Hz midbass region which the same slope seemed to be the best at fixing.This is the bit I need to spend time with to get just right using a few of the suggestions I've read on here.I haven't automatically programmed myself not to try the shallower slopes though,so will be giving them a try when I get time.

Edit....One last question on assymetrical slopes which I've never really thought about before.Is there any reason to always use symmetrical high and low pass slopes,or would certain situations need so a high pass of say 12db followed up by a low pass of say 24 db?


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## cajunner (Apr 13, 2007)

Imagewerx said:


> Edit....One last question on assymetrical slopes which I've never really thought about before.Is there any reason to always use symmetrical high and low pass slopes,or would certain situations need so a high pass of say 12db followed up by a low pass of say 24 db?



yes, and yes.

there are so many different variables that it would take a lengthy list to show the permutations, but suffice to say that phase and slope, acoustic roll-off and box type, horn use and the leaky sealed boxes of infinite baffle, all introduce their own varying degrees of success WRT a successful implementation.

reflections in a car environment, diffraction, compartment cancellations and nulls/nodes, all relate in some non-minor fashion, and it's not cut and dry like when you're time-aligned at 60 degrees unilateral triangulation, or home audio simple.


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## Patrick Bateman (Sep 11, 2006)

Imagewerx said:


> We're talking about 48 db/octave steep here.Is there anything wrong with going this steep?
> 
> It means I can run my horns down to 700 Hz without any problems.My midbass come in at 60 Hz @ 48 db/octave,but without the sub it doesn't sound as if there's any REAL hard hitting midbass there.They're each in about a 6 litre sealed box that needed a LOT of e/q between about 100 and 150 Hz to get them sounding half decent.
> 
> ...


What compression driver are you running with your horns?

Most compression drivers have an acoustic rolloff that's about 24dB/octave. Combine that with a 24db/octave xover filter and you have an effective rollof of 48dB octave.









Here's a compression driver on a big QSC Waveguide, note the steep acoustic rolloff


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## Imagewerx (Nov 30, 2012)

cajunner said:


> yes, and yes.
> 
> there are so many different variables that it would take a lengthy list to show the permutations, but suffice to say that phase and slope, acoustic roll-off and box type, horn use and the leaky sealed boxes of infinite baffle, all introduce their own varying degrees of success WRT a successful implementation.
> 
> reflections in a car environment, diffraction, compartment cancellations and nulls/nodes, all relate in some non-minor fashion, and it's not cut and dry like when you're time-aligned at 60 degrees unilateral triangulation, or home audio simple.


Ok thanks.As well as there now being a lot more chances to get it right,there's also even more chances to get it wrong.



Patrick Bateman said:


> What compression driver are you running with your horns?
> 
> Most compression drivers have an acoustic rolloff that's about 24dB/octave. Combine that with a 24db/octave xover filter and you have an effective rollof of 48dB octave.
> 
> ...


Just the standard ones with the ID CD2 comps Patrick,which I think are B&C DE45s.So with that thinking in mind,I'm getting an effective rolloff of 72 db/octave?


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## FG79 (Jun 30, 2008)

Jazzi said:


> ...and...
> 
> 
> 
> ...


Well if this is strictly a subwoofer to midbass blending discussion, then my apologies.....a 6 dB slope is not the most common or ideal type to go in many cases. You might be able to high pass a midbass with a 6, but low passing a sub doesn't work at 6, unless the cut off frequency is very low maybe.

I responded in general to the OP, and may have missed the specific nature of his post. But I will say that it's not uncommon to see 24 and 48 dB slopes used much higher in the midrange and treble region....and that's where my issue lies.

BTW, I've run midbasses in a car with no high pass setting at all at one point because I had no choice in the situation. It worked fine so long as you weren't really blasting the music. For some music, the no crossover was amazing.....the fullness was something you had to experience to believe. 

So I bring that up because I sometimes see a 30-40 hz high pass with a 24/36/48 slope, and I'd say just forego the whole crossover entirely at that point.


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## therapture (Jan 31, 2013)

Being just 14 months into the active/dsp field, I am not afraid to experiment. I learn something almost every time I hook up the laptop haha. I have been following and reading up on xover threads, and after reading this one I just went out to my car and changed my 48db mid slopes to 24db, still L-R at 75hz, and I'll be damned if it didn't bring the bass more up front. I ended up adding 1.9ms to the sub delay and wham! it made the sub disappear into the dash.

And maybe a placebo effect until I test a bit more...but I swear the stage deepened as well. I did knock a click off the bass setting on the head unit...but damn I like.


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## Hanatsu (Nov 9, 2010)

FG79 said:


> Well if this is strictly a subwoofer to midbass blending discussion, then my apologies.....a 6 dB slope is not the most common or ideal type to go in many cases. You might be able to high pass a midbass with a 6, but low passing a sub doesn't work at 6, unless the cut off frequency is very low maybe.
> 
> I responded in general to the OP, and may have missed the specific nature of his post. But I will say that it's not uncommon to see 24 and 48 dB slopes used much higher in the midrange and treble region....and that's where my issue lies.
> 
> ...


It also depends how the drivers are mounted. I have the midrange/tweeter within 2" of eachother. There's no issue whatsoever using 'steep slopes'. If the drivers are mounted further apart a 12/18dB slope tend to work better IME. 

The biggest issue I have with using 6/12dB slopes is that if you're crossing near the borders of the drivers optimal power response then you won't have full offaxis response from both drivers, which will cause blending issues. Also, using a 6/12dB filter will cause combing in the stopband of the midr LP/Tw HP filters. The narrower stopband the better is it. 

Using steep slops in the modal region can be beneficial too. If your intended crossover point ends up close to a modal dip from either sub or the mid's response you can use a steep filter to avoid crossing right into the dip, which also can destroy blending. 

Fyi, I have also heard what you refer to as 'fullness' of using no highpass on the mids. Turned out it was just a tuning issue, same result can be attained by compensating for the group delay the filter introduces. It can be measured with REW for example.

Sent from my Samsung Galaxy 3 via Tapatalk.


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## minbari (Mar 3, 2011)

I have to agree with the shallow slope crowd. In alot of cases I have found that shallow slopes just sound more natural. I have run my HLCD at 24db/oct, 1300hz and I am now running them at 2800hz, 6db/oct. The higher cutoff with a shallower slope sounds much better than the steep slope at a lower freq. with a 6.5" speaker I can run the high end high enough so there is no hole.

Of course if you are limited by a driver so that you cant cross sooner rather than later, then steeper slopes might work.


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## BuickGN (May 29, 2009)

minbari said:


> I have to agree with the shallow slope crowd. In alot of cases I have found that shallow slopes just sound more natural. I have run my HLCD at 24db/oct, 1300hz and I am now running them at 2800hz, 6db/oct. The higher cutoff with a shallower slope sounds much better than the steep slope at a lower freq. with a 6.5" speaker I can run the high end high enough so there is no hole.
> 
> Of course if you are limited by a driver so that you cant cross sooner rather than later, then steeper slopes might work.


I'm lucky enought to have drives with plenty of displacement that will also play very high as well. So I have a lot of choices when it comes to crossovers. 

I tried the 6db thing about a year ago and didn't like it but it was when I first went from the MS8's autotuning to the PS8. It was my first time manually tuning so maybe I should revisit it just to givce it a fair chance. 

When you guys run your 6db slopes, are you underlapping your drivers? I know, I know, it depends on the car and the setup. But in general do most people underlap when using 6db slopes? I don't expect it to work for me, what Erin said about reflections in a car environment makes sense but I want to give it one las shot. 

I switched to 48db about 6 months ago when I was still learning a lot and it sounded the best it had sounded but I think it covered up a lot of my lack of tuning skills. Two days ago I went back to 24db slopes without changing the crossover points and it sounds more alive and less flat and surprisingly it stages better.

I have my tweeters at 2,700/12db though. I don't have the guts to run them that low at 6db even though I have run them at 1,600hz/24db. I've tested the midrange at 180hz/6db and the midbass with no HP so I know where the limits are, no worries about hurting anything.

So, should I start by underlapping? I only ask because I'm not going to hav emuch time to mess with it.


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## minbari (Mar 3, 2011)

BuickGN said:


> I'm lucky enought to have drives with plenty of displacement that will also play very high as well. So I have a lot of choices when it comes to crossovers.
> 
> I tried the 6db thing about a year ago and didn't like it but it was when I first went from the MS8's autotuning to the PS8. It was my first time manually tuning so maybe I should revisit it just to givce it a fair chance.
> 
> ...


I dont know about everybody, but I am underlapping. 2800hz for the horn and 1900hz for the 6.5". you also have to take in the horn's response too. it has a peak in response around 2500hz, with some EQ, it is pretty flat on the RTA and sounds better than it did before.

I think the thing to keep in mind with a shallow slope is you are going to be crossing higher with tweeter to account for the fact that you are not losing much output as freq goes down.

to use your example of 2700hz 12db/oct. at 1350hz you are 12db down. to get a similar response with a 6db filter you would need to double the cutoff to 5400hz. The difference is that at 2700hz you will be 6db down instead of 0db down like you are with the 12db.

I would add that I am not running 6db filters everywhere. The HPF for the 6.5" and LPF subs are 18db.


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## Imagewerx (Nov 30, 2012)

therapture said:


> Being just 14 months into the active/dsp field, I am not afraid to experiment. I learn something almost every time I hook up the laptop haha. I have been following and reading up on xover threads, and after reading this one I just went out to my car and changed my 48db mid slopes to 24db, still L-R at 75hz, and I'll be damned if it didn't bring the bass more up front. I ended up adding 1.9ms to the sub delay and wham! it made the sub disappear into the dash.
> 
> And maybe a placebo effect until I test a bit more...but I swear the stage deepened as well. I did knock a click off the bass setting on the head unit...but damn I like.


I haven't got as far as playing with time alignment yet,this'll be the very last thing I do once I've got the rest of it how I want it.



Hanatsu said:


> It also depends how the drivers are mounted. I have the midrange/tweeter within 2" of eachother. There's no issue whatsoever using 'steep slopes'. If the drivers are mounted further apart a 12/18dB slope tend to work better IME.
> 
> The biggest issue I have with using 6/12dB slopes is that if you're crossing near the borders of the drivers optimal power response then you won't have full offaxis response from both drivers, which will cause blending issues. Also, using a 6/12dB filter will cause combing in the stopband of the midr LP/Tw HP filters. The narrower stopband the better is it.
> 
> ...


I don't have the luxury of any of my drivers being very intimate neighbours with each other.I have the horns in the front (obviously!) and my midbass are behind me,at a guess about a metre from the HF/mid drivers in the front.
I had a system in a car many many years ago where I found the midbass drivers rolled off naturally at about 3KHz,and paired up with some 12db/octave actively highpassed tweeters,it definitely sounded nicer with just an 80Hz HPF on the midbass and no low pass.I tried this with subsequent midbass drivers but could never repeat the results I got with that set,and all the rest sounded better bandpassed in the "normal" way.


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## thehatedguy (May 4, 2007)

You guys need to specifiy electrical or acoustical slopes.

I once simed the Ultra mini horns, and with a 6.3k 6 dB filter, it flattend out the FR and was something like a 24 dB acoustic slope down low. Then with it was either a 12 or 18 dB electrical filter up high to get really good phase summation...either the horn or midbass had to have the polarity reversed too. But that information is elsewhere in another thread.


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## Hanatsu (Nov 9, 2010)

I'm ALWAYS talking about acoustical slopes. Electrical doesn't matter at all, just a mean to shape the response.

I have used a 6dB/oct highpass at 1100Hz. The acoustic crossover was 200Hz / 24dB ^^


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## Hanatsu (Nov 9, 2010)

Imagewerx said:


> I don't have the luxury of any of my drivers being very intimate neighbours with each other.I have the horns in the front (obviously!) and my midbass are behind me,at a guess about a metre from the HF/mid drivers in the front. I had a system in a car many many years ago where I found the midbass drivers rolled off naturally at about 3KHz,and paired up with some 12db/octave actively highpassed tweeters,it definitely sounded nicer with just an 80Hz HPF on the midbass and no low pass.I tried this with subsequent midbass drivers but could never repeat the results I got with that set,and all the rest sounded better bandpassed in the "normal" way.


Well. It's hard to tell over a forum what settings is optimal... never tuned a system like yours either. As long as you not aware of the acoustic slope, there's no way of telling which electrical settings you should use. If you got access to a measurement mic and a computer you can do a few FR sweeps and post them here. Then we have lots more to go on...


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## cajunner (Apr 13, 2007)

I'm talking electrical, because that's what the elements in the crossover consist of, the measured response in-situ, is the target.

when I say I like 6 db slopes, I mean I like using less parasitics in the passives.

If you've got felt cones and you've got soft domes, and you've got low power AND low sensitivity, it doesn't make a lot of sense to power-soak a speaker complement that is smooth in low treble roll-off and low-playing in the tweeter.

Getting phase to work well is another thing altogether, and seems to go by installation particulars.

dash tweeters and low-door mounted midranges, might need something different than high-mounted midranges and sail tweeters, or a-pillar tweeters and kick-panel midrange.


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## Hanatsu (Nov 9, 2010)

What I think is going on in lots of the cases here is that people that use 6dB slopes tune the frequency response over a wide range and therefore changing how the system sounds. Everyone is so quick to bring up the "Phejjjsss izzuuesz".


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## Hanatsu (Nov 9, 2010)

cajunner said:


> dash tweeters and low-door mounted midranges


... very rarely sounds good. Actually, I've never heard a system that had great focus with such setup. The center is always "blurred". My center was really really narrow with sail mounted midranges.


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## Earzbleed (Feb 10, 2013)

Thanks ccapil. Just explained what's going on with my home sub. All makes sense now.


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## Patrick Bateman (Sep 11, 2006)

minbari said:


> I have to agree with the shallow slope crowd. In alot of cases I have found that shallow slopes just sound more natural. I have run my HLCD at 24db/oct, 1300hz and I am now running them at 2800hz, 6db/oct. The higher cutoff with a shallower slope sounds much better than the steep slope at a lower freq. with a 6.5" speaker I can run the high end high enough so there is no hole.
> 
> Of course if you are limited by a driver so that you cant cross sooner rather than later, then steeper slopes might work.


In my 'Monster Massive' project I'm hoping to create real 6dB/octave slopes, just to see how it sounds. Although I've used first order electrical crossovers in a lot of my projects, once you factor in the drivers response, it's more like twelve or even eighteen decibels per octave.

Now that I'm using miniDSP I'm a total convert to active crossovers. I won't deny that it's wasteful to buy four or six amp channels, but the ability to 'dial in' nearly any response curve or rolloff is a lot of fun.


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## Patrick Bateman (Sep 11, 2006)

Imagewerx said:


> Just the standard ones with the ID CD2 comps Patrick,which I think are B&C DE45s.So with that thinking in mind,I'm getting an effective rolloff of 72 db/octave?


That's correct. And note that output is generally limited by excursion. So if the driver has an inherent rolloff of 24dB/octave, you can run it with relatively shallow slopes. (Because the driver itself is rolling off most of the output.)


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## TheDavel (Sep 8, 2006)

Andy Wehmeyer said:


> There's no real practical difference between 24 and 48dB/octave.
> 
> Let's say your amp puts out 100 watts. -24dB would be .3525 watts. -48dB would be .00062 watts. Yes, one is steeper, but for what purpose?


Its info like this that is invaluable in audio.


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## BuickGN (May 29, 2009)

Hanatsu said:


> ... very rarely sounds good. Actually, I've never heard a system that had great focus with such setup. The center is always "blurred". My center was really really narrow with sail mounted midranges.


Would this apply to kick mounted midranges and dash tweeters as well?


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## Hanatsu (Nov 9, 2010)

BuickGN said:


> Would this apply to kick mounted midranges and dash tweeters as well?


Yes. The distance between the drivers and the reflections of the center console mess with focus. I have tuned many of those setups and they never get as focused as with the 'midrange up high close to tweeter' setups. The drawback is a more "headphone"-like sounding system, it's more in your face. The midrange low-systems tend to sound like there's more depth but (much) less focus.


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## Imagewerx (Nov 30, 2012)

Hanatsu said:


> Well. It's hard to tell over a forum what settings is optimal... never tuned a system like yours either. As long as you not aware of the acoustic slope, there's no way of telling which electrical settings you should use. If you got access to a measurement mic and a computer you can do a few FR sweeps and post them here. Then we have lots more to go on...


I wasn't actually asking for help to set my system up,really just the general reasons for or against steep crossover slopes,but as you're offering.I do have my old Coustic RTA33 which I'm pretty certain can store and output the curve in a PC compatible format,so will see what I can do.


Patrick Bateman said:


> That's correct. And note that output is generally limited by excursion. So if the driver has an inherent rolloff of 24dB/octave, you can run it with relatively shallow slopes. (Because the driver itself is rolling off most of the output.)


I used to run a pair of USD rotomount horns with piezo electric compression drivers.Painfully bright at about 8 Khz but a purely capacitive load that made it a natural high pass filter,they actually sounded better running full range with no high pass than they did through an active crossover.
But with the moving coil compression drivers I'm using now,I was surprised at how low they play despite their on-paper roll off below about 1 KHz.Playing them full range at low volume,I was hearing output down to maybe 400 Hz or so,but they wouldn't take any real volume used like that.I still THINK they've got more power handling now crossed at 700 Hz @ 48db/octave than before when they were at 1000Hz @ 18db/octave.But the almost infinte possibilities the miniDSP give me could account for a lot of that though.


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## sqnut (Dec 24, 2009)

Hanatsu said:


> Everyone is so quick to bring up the "Phejjjsss izzuuesz".


True. Esoteric and technical discussions on phase shift, phase coherence etc are as meaningless as the debate on merits of 6db slopes, just cause its used in home audio. For one, the room is totally different.

In a car, to think of phase as anything other than arrival times and polarity of drivers, is a total waste of time. If phase shifts are audible, you're going to hear them in the response domain. Remember, you can only correct in the response and time domain. 

Focus on how it sounds, use the tuning tools together to shape the sound. In a car the overall system response and how you get there is what really counts. 6db slopes _all round_ wont get you there, no matter what you do and esoteric phase discussions will confuse the hell out of you. In both cases your car is not going to sound anything like your home setup.

Sometimes we make this hobby sound like it's rocket science. Maybe we want to showcase our theoretical knowledge. That's a disservice to someone who's just starting out and wants to learn and would confuse the hell out of them. 

So what really counts? The two things you do need are one the ability to analyse what you're hearing and two accurately connect/correct that with your tuning tools. Measurements help upto a point, but beyond that learn to use your ears.


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