# Difference heard between 12 dB/octave and 24 dB/octave



## presscot (Aug 7, 2015)

If I have 2 electronic crossovers that are the same model and have the same high-pass filter at 170Hz. But one is shaped by 12 dB/octave, while the other is shaped by 24 dB/octave. Also, they are set to have another parameter identical; Gain level.

What is the different sound will I hear between the two?


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## Jscoyne2 (Oct 29, 2014)

presscot said:


> If I have 2 electronic crossovers that are the same model and have the same high-pass filter at 170Hz. But one is shaped by 12 dB/octave, while the other is shaped by 24 dB/octave. Also, they are set to have another parameter identical; Gain level.
> 
> What is the different sound will I hear between the two?


Same sound. One just has everything before 170hz far quieter than the other. 

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## capea4 (Sep 2, 2010)

there is a phase difference as well


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## presscot (Aug 7, 2015)

Jscoyne2 said:


> Same sound. One just has everything before 170hz far quieter than the other.
> 
> Sent from my SGH-M919 using Tapatalk


Is the 24dB/oct a quieter?


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## presscot (Aug 7, 2015)

capea4 said:


> there is a phase difference as well


And what am I going to hear?


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## JVD240 (Sep 7, 2009)

The 12db/oct crossover will have more audible low frequency content.

Someone correct me if I am wrong, but the phase is irrelevant without another drive/x-over point being mentioned.


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## nstaln (Feb 11, 2009)

If the crossovers are actually electronic...which is to say active, then phase shouldn't be an issue.

If going between a 12db and 24db PASSIVE crossover then yes phase shift will be different.


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## GEM592 (Jun 19, 2015)

What you will hear depends on lots of things, but more power below 170 Hz will be delivered to your speakers with the 12 setting than the 24 setting.

Whether or not there is a phase shift depends on the crossover. Some are designed to correct phase shift in baseline designs, some are not.

I tend to use steep slopes in low frequency ranges, and gentle slopes in high ranges. But your results may vary.


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## Alrojoca (Oct 5, 2012)

Whatever sounds better to us, I hear more boomy bass with shallow slopes.
Steeper slopes offer more protection specially for tweeters.


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## I800C0LLECT (Jan 26, 2009)

Biggest difference is that 12 decibel slope means the signal drops off 12 decibels per octave. If it's 24... Then drops off at 24 decibels per octave.

Andy W. believes 24 decibels slopes are best in car audio.

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## Hoye0017 (Mar 23, 2010)

nstaln said:


> If the crossovers are actually electronic...which is to say active, then phase shouldn't be an issue.
> 
> If going between a 12db and 24db PASSIVE crossover then yes phase shift will be different.




Im pretty sure active crossovers also create phase shift. Here's an article that states it explicitly:
https://passlabs.com/press/phase-coherent-crossover-networks


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## quickaudi07 (May 19, 2010)

Google search does wonders sometimes !! 

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## capea4 (Sep 2, 2010)

presscot said:


> And what am I going to hear?


there could be a dip in response between these drivers and whatever playing the lower band. mostly i find it affects where the bass seems to come from. after T/A playing with the slope can help you get a better front bass presence.


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## Alextaastrup (Apr 12, 2014)

Ttied both with sub and monoamp JL500.Higher orders sound owfull. Therfore have chosen not higher then second order. Not easy afterworfs to align to the front. But it wortj doing so
Maybe it was problem of Alpine 137BTI. 


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## sqnut (Dec 24, 2009)

When one is listening to music in a tiny and highly reverberant environment, like a car, or a shower stall, 90% of what one is hearing are early reflections. In this scenario the more isolated a pair of drivers is from the ones before and after it, the easier it is to dial in clean and dynamic sound. Sharper imaging, better tonality and greater timbrel accuracy. In a car, a pair of drivers playing the same pass band is bad enough, but to have 4 drivers sharing 2-4 octaves between them, is just mayhem. Steeper slopes = cleaner sound, ymmv.


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## capea4 (Sep 2, 2010)

Agree&#55357;&#56390;&#55356;&#57339;
I was doing this the other day with a dsp that only has 180*phase adjustment, so playing with slope gave me more options. Cooler dsp's have better adjustability.


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## Alrojoca (Oct 5, 2012)

All points well taken and considered when using a DSP.

Now 
When dealing with passive component sets, not needing to bandpass them, and only high pass them, exceeding a steeper than -12 db slope may not deliver the best results due to the passive crossover slope being used already.


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## sqnut (Dec 24, 2009)

Alrojoca said:


> All points well taken and considered when using a DSP.
> 
> Now
> When dealing with passive component sets, not needing to bandpass them, and only high pass them, exceeding a steeper than -12 db slope may not deliver the best results due to the passive crossover slope being used already.


Not sure I understand what you're saying


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## Alrojoca (Oct 5, 2012)

sqnut said:


> Not sure I understand what you're saying



Components using a passive, probably have a -12db slope, if they are high passed at -24db with HU for example, then we may end up with a -12db plus a -24db slope for the tweeters for example.
Not sure if that is the case or it makes sense.


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## sqnut (Dec 24, 2009)

Alrojoca said:


> Components using a passive, probably have a -12db slope, if they are high passed at -24db with HU for example, then we may end up with a -12db plus a -24db slope for the tweeters for example.
> Not sure if that is the case or it makes sense.


Ok I get it now, you're talking about cascaded cross overs. So, cascading electronic xovers is perfectly fine, because you can select the same HP/LP on both xovers. For instance in my setup, the bit10 gives a max slope of 24db on each driver, but for me that is too shallow a slope for the sub. So I use 24db on the hu and 24 on the bit10, both at 50hz and now I have, 50 hz at 48db/oct. You can take this one step further and on the eq for the sub channel, I roll off another 12 db from 50-100 and now I have a 10th order on the sub, much better. I'm just a bit OCD about keeping audible output from the sub under 70hz, helps with minimizing resonances also.

Cascading an electronic xover with a passive one is a different ballgame, primarily because the chances of landing up with asymmetric points is much higher. That will give a phase shift between the LP/HP.


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## Alextaastrup (Apr 12, 2014)

In this case you have to play midbasses quite low. Does this give some problems at high volumes? 

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## sqnut (Dec 24, 2009)

Alextaastrup said:


> In this case you have to play midbasses quite low. Does this give some problems at high volumes?
> 
> Sendt fra min GT-I9505 med Tapatalk


Hi Alex, 

Yes my sub and midbass are crossed at 50hz and loud for me is ~90-95 db peak, yes things start breaking up past about 105db and that's my signal that I turned it up too high.

The two main reasons I run a low Xover are first, typically most recordings are stereo 80hz and up, while below 80 the bass is mostly recorded mono. So I don't want the sub (mono) playing audibly in a range that is recorded stereo. Secondly, a low xover helps minimize rattles and resonances between the sub behind me and my ears. At a purely subjective level the mid bass is 'cleaner' this way.


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## Alextaastrup (Apr 12, 2014)

Agree with this. I use now 40/80 both second order filters. It helps to move bass forward and allow me listen music in a full range even without sub when children in the car. 
Why second order? I tried to listen solely sub from the bagage room behind at different filter settings and was not satisfied with high orders. In order to fit both sub and midbasses I use now huge delay - more than 40 ms

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## sqnut (Dec 24, 2009)

If have a basic minimum eq power, e.g. p80, 800/880 level and above, I try to stay away from underlap / overlap / asymmetric L&R xover points, as these cause me to constantly tinker with the eq and timing, trying to get it to sound right and it never worked for me. I also stay away from using my xovers as an eq. For whatever short term benefits these provided, over the long run I always found myself coming back to matching points and then moving both drivers together or playing with the slopes etc. There is just more cohesion to the sound this way, that's the best way I can describe it. Maybe it's a phase cohesion thing by keeping matching LP/HP points.


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## Alextaastrup (Apr 12, 2014)

Right. Timing is rather important. I have mm managed

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## Alextaastrup (Apr 12, 2014)

To press it down under 3 msec in the whole range of 3way front+sub. 

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## sqnut (Dec 24, 2009)

Alextaastrup said:


> Right. Timing is rather important. I have mm managed
> 
> Sendt fra min GT-I9505 med Tapatalk


I agree, timing is critical to get good dynamics and timbral accuracy. Each note has fundamental frequencies and harmonics, where each successive harmonic is delayed by a certain time period from the fundamental, this time map (so to say), is on the recording. 

Now, if these fundamental and harmonics are spread over two drivers and the drivers are not timed right, the time difference between the fundamental and harmonics that we hear, will be different from what's on the recording. This will kill a lot of the recorded dynamics and mess up the timbral accuracy of the instrument, no amt of eq will fix this.


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## Alrojoca (Oct 5, 2012)

Sqnut

Maybe that is why I could not hear enough bass with steeper slopes.

How do I fix it? Boost EQ? Or boost sub volume 2 or 3 dbs.

Maybe that is why 15"s and 18"s from other systems did not Impress me, probably tuned for SQ with very steep slopes. Maybe shaking bass that can't be heard, less distortion and resonances as you mentioned.


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## Alextaastrup (Apr 12, 2014)

If sub is domimating it is nothing to do with SQ

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## sqnut (Dec 24, 2009)

Alrojoca said:


> Sqnut
> 
> Maybe that is why I could not hear enough bass with steeper slopes.
> 
> ...


The car is a bass engine even on steep (24-48db) slopes, thanks to cabin gain. A 10" on 200 watts, paired to 6.5", 2 way / 3 way will give you gobs of low end and you won't lack for anything. Raise 1-2db on the sub level and your rear view will dance, so if a 15 left you cold, it's probably less to do with steep slopes and more to do with hot mid range masking out the low end and / or timing issues between sub and woofer.


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## sqnut (Dec 24, 2009)

The number of folks who qualify SQ sound with adjectives like thin, meh, flat etc is just amazing, while the fact is that if you heard a SQ car that sounded like that, then you didn't _really_ hear an SQ car, just someones concept of what SQ is.

Imho, the best way to experience SQ is with proper speakers, book shelves or floor standers + sub (LP ~60), unless you're rocking out to Cervin Vegas with 12" mid bass. What you hear with these setups is SQ, SQ is the natural balance and flow of sound across the 10 octaves, it is how real and 'live' the vocals and instruments sound. It is the dynamics in the recording, the sense of high and lows. SQ is what is on the recording and this is what you want to hear in the car. 

How much oomph do I want? However much is on the recording. Everything else is not SQ and just a personal preference or notion, of what SQ is.


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## sqnut (Dec 24, 2009)

Alextaastrup said:


> If sub is domimating it is nothing to do with SQ
> 
> Sendt fra min GT-I9505 med Tapatalk


Agree 100%.


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## I800C0LLECT (Jan 26, 2009)

sqnut said:


> The car is a bass engine even on steep (24-48db) slopes, thanks to cabin gain. A 10" on 200 watts, paired to 6.5", 2 way / 3 way will give you gobs of low end and you won't lack for anything. Raise 1-2db on the sub level and your rear view will dance, so if a 15 left you cold, it's probably less to do with steep slopes and more to do with hot mid range masking out the low end and / or timing issues between sub and woofer.


I can attest to that! Friends and family who listen to my car are astounded to see just a ten in my spare tire well. Mid bass are under the seats too.

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## I800C0LLECT (Jan 26, 2009)

Double post


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## Alrojoca (Oct 5, 2012)

sqnut said:


> The car is a bass engine even on steep (24-48db) slopes, thanks to cabin gain. A 10" on 200 watts, paired to 6.5", 2 way / 3 way will give you gobs of low end and you won't lack for anything. Raise 1-2db on the sub level and your rear view will dance, so if a 15 left you cold, it's probably less to do with steep slopes and more to do with hot mid range masking out the low end and / or timing issues between sub and woofer.



Maybe I'll have to TA the sub again, or check my settings although increasing the sub vol helped.

I don't push the bass or like to hear a lot of bass. Maybe cleaner bass may be identified as less bass, it just seems to me that shallow slopes seem to give punchier bass, and maybe it proves what I have been told and read, steeper slopes need more power, although some will disagree with that, in any case after I tried it yesterday the overall sound was cleaner and smoother and I tend to turn the volume higher to hear more. And even it does not provide instant gratification when I do, I get some fatigue that has to be related to it.


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## sqnut (Dec 24, 2009)

Alrojoca said:


> Maybe I'll have to TA the sub again, or check my settings although increasing the sub vol helped.
> 
> I don't push the bass or like to hear a lot of bass. Maybe cleaner bass may be identified as less bass, it just seems to me that shallow slopes seem to give punchier bass, and maybe it proves what I have been told and read, steeper slopes need more power, although some will disagree with that, in any case after I tried it yesterday the overall sound was cleaner and smoother and I tend to turn the volume higher to hear more. And even it does not provide instant gratification when I do, I get some fatigue that has to be related to it.


Listening fatigue is mostly a response issue. Check the 1-5 KHz range, easing back a bit here should help and it should bring out a bit more of the low end.


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## geshat00 (Jun 1, 2016)

Also in my experience people seem to correlate vibration/rattling impact with bass. A good sub with lesser distortion will sound softer...

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## Alrojoca (Oct 5, 2012)

I had to get rid of the subs TA,, it's one of those things, when the sub is as far as the passenger's midbass or half inch less further, it becomes complicated and a few things have to be tried to make it work, that was why I heard less bass with steeper slopes, and after EQuing, everything came to life including boosting 1db the 12.5 kHz band, and cutting levels aggressively in some of the mb bands.


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