# Preferred subwoofer crossover slope ?



## Robb (Dec 5, 2008)

Hey, just a question.
I have my crossover slope on my sub set at 12db on both ends.
I have my LPF set to 80hz and HPF set to 25hz.

(Btw,the spec sheet says my 8" kicker sub plays down to 29hz)
Will I damage the sub with the HPF set to 25hz ?

What do you guys recommend ? 18db for the sub ?


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## sqnut (Dec 24, 2009)

You don't really need a hpf on the sub, let it roll off and no you would not be hurting it. For the lpf I would use the steepest slope. I lpf my sub at 50hz on a 36db/oct slope. If you're crossing the sub and mids at 80hz, put the sub on the steepest slope that yoour hu gives and chances are you'll find your midbass much clearer. 12/18 db slopes at 80hz means your sub is playing well into the 200hz+ zone.


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## Robb (Dec 5, 2008)

I'm running active using my headunit DRZ9255 which only has a slope od 18db max. 
So why is there a HPF filter for my sub on the headunit ??


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## FartinInTheTub (May 25, 2010)

Robb said:


> I'm running active using my headunit DRZ9255 which only has a slope od 18db max.
> So why is there a HPF filter for my sub on the headunit ??


I've run the DRZ and 18db is all your gonna get. Use either 63 or 80hz. I see you're running Studio 100 amps so there is no onboard crossover. If you were running an amp with built in crossovers I would have suggested to see if it had a steeper slope.


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## kyheng (Jan 31, 2007)

sqnut said:


> You don't really need a hpf on the sub, let it roll off and no you would not be hurting it. For the lpf I would use the steepest slope. I lpf my sub at 50hz on a 36db/oct slope. If you're crossing the sub and mids at 80hz, put the sub on the steepest slope that yoour hu gives and chances are you'll find your midbass much clearer. 12/18 db slopes at 80hz means your sub is playing well into the 200hz+ zone.


You are not that right on this, is best to have HPF on your sub...... To safeguard your amp and sub... What you can't hear does not means it does not exist... The sub will still moving if you see it properly....


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## ZAKOH (Nov 26, 2010)

Robb said:


> Hey, just a question.
> I have my crossover slope on my sub set at 12db on both ends.
> I have my LPF set to 80hz and HPF set to 25hz.
> 
> ...


The spec sheet probably reports the +/-3dB or +/-4.5dB frequency response. This means that below 29Hz the output will be dropping. You can play deeper bass content but be careful about not exceeding driver's excursion limits.

For high-pass (subsonic filter). I would recommend the steepest slope you can select with with cut frequency at around 20Hz unless the subwoofer just can't do it. Stuff in 20-25Hz can be barely heard. However, it can be felt.

For subwoofer low pass slope, I prefer the same as for the mids, 18dB. Definitely aim at making the sub inaudible above 100Hz. Most mids should have no problems playing down to 100Hz well.


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## bLG (May 1, 2009)

Absolutely use a HPF (12 dB/oct) to protect the sub from infrasonics. 
For the LPF, that will take some tweaking, slope between 12-24 dB/oct.
It really depends on the natural roll-off of the driver. Generally, I prefer 18 dB or 24 dB.


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## sqnut (Dec 24, 2009)

kyheng said:


> You are not that right on this, is best to have HPF on your sub...... To safeguard your amp and sub... What you can't hear does not means it does not exist... The sub will still moving if you see it properly....


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## sqnut (Dec 24, 2009)

bLG said:


> Absolutely use a HPF (12 dB/oct) to protect the sub from infrasonics.
> For the LPF, that will take some tweaking, slope between 12-24 dB/oct.
> It really depends on the natural roll-off of the driver. Generally, I prefer 18 dB or 24 dB.


Really


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## ZAKOH (Nov 26, 2010)

The way I see it, there is no evidence that having speakers reproduce the frequencies below 20Hz will add anything to audible music. So I personally would go ahead and set HPF at 20Hz. Actually my amplifier has a subsonic filter than can't be defeated.. At the same time, it is probably not terribly wrong not to have subsonic filter. After all, many amplifiers do not have it, specially with sealed box subs.

When I was breaking in my sub I let it run for a while playing a 20Hz 0dB tone. There was something like 1 inch excursion peak to peak. No one could hear it.


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## jcollin76 (Oct 26, 2010)

sqnut said:


> Really


Care to explain?


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## pionkej (Feb 29, 2008)

jcollin76 said:


> Care to explain?


X2

A HPF is definitely needed on a ported sub (and I didn't see the OP specify his alignment) to protect the sub from unloading below tuning. 

Sealed boxes are super inefficient and it takes TONS of power to reproduce content below around 30hz in a sealed box. Why ask your amp to "strain" to reproduce content an 8" sub can't really output anyway?

It makes sense to run a HPF no matter what IMHO.


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## jcollin76 (Oct 26, 2010)

Setting up my new sub stage this week, two diyma's in a 1.5 sealed arrangement. I guarantee I'll be using a hp....


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## kyheng (Jan 31, 2007)

ZAKOH said:


> The way I see it, there is no evidence that having speakers reproduce the frequencies below 20Hz will add anything to audible music. So I personally would go ahead and set HPF at 20Hz. Actually my amplifier has a subsonic filter than can't be defeated.. At the same time, it is probably not terribly wrong not to have subsonic filter. After all, many amplifiers do not have it, specially with sealed box subs.
> 
> When I was breaking in my sub I let it run for a while playing a 20Hz 0dB tone. There was something like 1 inch excursion peak to peak. No one could hear it.


Well, some people that self claim that they are audiophile claims that they are able to hear it, be it 20Hz or the "life" after 20kHz.... Which are completely dumb.... 
Setting the HPF at 20Hz are good, but I would go higher, depending on the sub's paper specs.... But then, I won't do so as I may lost something later on, so subsonic filter(better if the value adjustable) will be the best bet....


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## jcollin76 (Oct 26, 2010)

But what 'music' has content that low? All I can think of would be pipe organ, some bass specific stuff, and test tones. Is't that about it?
I'm not going to listen to test tones, bass tracks, and prob not pipe organ... So in the interest of protecting my subs, I think having a hp filter is warranted. No?


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## pionkej (Feb 29, 2008)

kyheng said:


> Well, some people that self claim that they are audiophile claims that they are able to hear it, be it 20Hz or the "life" after 20kHz.... Which are completely dumb....
> Setting the HPF at 20Hz are good, but I would go higher, depending on the sub's paper specs.... But then, I won't do so as I may lost something later on, so subsonic filter(better if the value adjustable) will be the best bet....


I have no idea what you mean after "...but,then..." Are you telling the OP to do it but you don't?

Also, you CAN most definitely feel sub-20hz content. The problem is music doesn't contain much info that low (I believe a pipe organ or synthesizer are the only things that can). I promise there is a huge difference in having a sub tuned to 10hz vs 30hz in a home theater though (or setting the 10hz subs HPF set at 30hz). I know we're talking car audio here, but I just wanted to point out sounds that low do exist and can be heard/felt since it seemed to be implied they can't. 

**Good luck getting to a 10hz tune in car though. My 15's are in 10cu/ft boxes w/ 6" ports 30" long and still only get 13hz. That is why a HPF is good, relieve strain on the amps from trying to power content the subs can't produce.


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## pionkej (Feb 29, 2008)

jcollin76 said:


> But what 'music' has content that low? All I can think of would be pipe organ, some bass specific stuff, and test tones. Is't that about it?
> I'm not going to listen to test tones, bass tracks, and prob not pipe organ... So in the interest of protecting my subs, I think having a hp filter is warranted. No?


Beat me to it.


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## jcollin76 (Oct 26, 2010)

Lol not a bad thing having different people say the same thing, in different ways, helps others to understand better.... Maybe. Lol


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## sqnut (Dec 24, 2009)

Does your sub need a hpf? No

Will not having an hpf on your sub hurt your amp? No as long as you're not clipping the amp

Can you hear a 20hz note? Yes but you can feel it more than you hear it.

Do you need a grasp over basic English to communicate on this forum?


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## dragonrage (Feb 14, 2007)

jcollin76 said:


> But what 'music' has content that low? All I can think of would be pipe organ, some bass specific stuff, and test tones. Is't that about it?
> I'm not going to listen to test tones, bass tracks, and prob not pipe organ... So in the interest of protecting my subs, I think having a hp filter is warranted. No?


I can hear up to about 25kHz (actually measured using a signal generator on a speaker) but not well enough for it to really affect how I hear _music_. I have no idea if I can hear below 20Hz (the speaker we tested with was not capable of that) but it can be felt.

Anyway, guys, this is an 8" sub. Of course it needs a HPF, even if in a sealed box. 8"s are only capable of so much. I'd recommend one even for a sealed 12" or 15", but it's an absolute requirement for an 8". And I recommend it be at around 30Hz - the lower it is set at, the less overall output it will be able to have when it's being fed a signal that has that low frequency content because the lower the frequency, the more power and excursion used, thus trading overall output for low frequency capability.


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## kyheng (Jan 31, 2007)

pionkej said:


> I have no idea what you mean after "...but,then..." Are you telling the OP to do it but you don't?
> 
> Also, you CAN most definitely feel sub-20hz content. The problem is music doesn't contain much info that low (I believe a pipe organ or synthesizer are the only things that can). I promise there is a huge difference in having a sub tuned to 10hz vs 30hz in a home theater though (or setting the 10hz subs HPF set at 30hz). I know we're talking car audio here, but I just wanted to point out sounds that low do exist and can be heard/felt since it seemed to be implied they can't.
> 
> **Good luck getting to a 10hz tune in car though. My 15's are in 10cu/ft boxes w/ 6" ports 30" long and still only get 13hz. That is why a HPF is good, relieve strain on the amps from trying to power content the subs can't produce.


If the below conditions are met, then what you said are right, else, there's no right or wrong :
1. every sub from different brands have the same spec
2. this world only have 1 type of car with the same internal volume
3. all the enclosure are made in same size
4. all people listen to test tones only
5. all people listen to digital music only

Anyway, if I'm a dumb or a robot, then I would surely say it loud that I can feel or listen 20Hz.....


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## jcollin76 (Oct 26, 2010)

dragonrage said:


> I can hear up to about 25kHz (actually measured using a signal generator on a speaker) but not well enough for it to really affect how I hear _music_. I have no idea if I can hear below 20Hz (the speaker we tested with was not capable of that) but it can be felt.
> 
> Anyway, guys, this is an 8" sub. Of course it needs a HPF, even if in a sealed box. 8"s are only capable of so much. I'd recommend one even for a sealed 12" or 15", but it's an absolute requirement for an 8". And I recommend it be at around 30Hz - the lower it is set at, the less overall output it will be able to have when it's being fed a signal that has that low frequency content because the lower the frequency, the more power and excursion used, thus trading overall output for low frequency capability.


I agree. Speaking in general, there are many things that factor in... As you all have mentioned. As far as the op, yes he's using an 8, so a hp should prob be used to offer it some protection.
But back to overall, you can't just say yes, or no. Driver specs, enclosure size and type, listening level, content played, output desired, all factor in to how it's set up.


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## Robb (Dec 5, 2008)

Guys, yes I have an 8" ported sub (see pic) that can play down to 29hz max, as per spec sheet ! I have set the HPF to 25hz @ 18db and call it a day 

http://carphotos.cardomain.com/ride_images/3/2046/3009/30114004125_large.jpg
http://carphotos.cardomain.com/ride_images/3/2046/3009/30114004123_large.jpg

To me, technically it makes sense to have a HPF on your sub to keep your amp from stressing to play low frequencies.

thanks for your input guys


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