Box Frequency , Subsonic Filter , and Low Pass Filter

[_S7V7N_]

When tuning your subs if your box is Tuned to 40 Hz Should the subsonic filter on the amp be set to about 37Hz ? and The Low pass should be about where ? These are just hypothetical Numbers, but am trying to understand how they relate to each other.



Ty

[3cyltrbo]

Originally Posted by _S7V7N_

When tuning your subs if your box is Tuned to 40 Hz Should the subsonic filter on the amp be set to about 37Hz ? and The Low pass should be about where ? These are just hypothetical Numbers, but am trying to understand how they relate to each other.

Ty

Ideally you would set the subsonic filter just below your tuning frequency. Most ported enclosures will start to get real messy below the tuning frequency but it always depends on the driver being used and the enclosure tuning (overall Q / F3 etc...) . One good thing is that actual impedance rises exponentially as you approach the tuning frequency of the box / resonant frequency of the particular driver, this means that if your impedance increases by a factor of 10 right around the tuning frequency, the driver is only seeing a fraction of the power it would at up around 100hz (for example) and because of this natural loss of power to the driver near the tuning frequency any aberations caused shouldn't be too bad.

Low pass frequency is entirely dependant on.........: the rest of the system / the music you listen to / any cabin gain based on your install / pwr to each channel etc....

When I was competing I often played around with low-pass cutoffs as low as 50hz (but I had a sealed enclosure that could play cleanly well below 20hz), I usually kept them below 80hz. Remember that the cut-off frequency isn't a brick wall unless you've got a slope steeper than 36db/oct. Anything around 6db/oct or 12db/oct and you're still going to be hearing frequencies much higher than the cutoff.

This also factors into what you've got for the front end.

W

[Alien Mantis]

The type of music you listen to makes a big difference.

If you optimize your bass for rap beats, it won't be optimized for rock, and vise versa.

A box tuned to 40hz is pretty low.
For me, bass below 40hz is something I "feel" more than I "hear".

I like bass optimized around 60-80hz.
I set my bass amp crossover at 100hz.
Subsonic filter would be 35hz, if I had one.
I listen to rock and metal.

My main 6 1/2" speakers are set with a high-pass filter at 125hz.
So they play nothing below that frequency.
My system is missing frequencies between 100 and 125hz.
I don't even notice.

I tried setting my bass amp filter at 80hz, but I lose a little mid-bass.
( The bass guitars )
So 100hz is best for my system.

My ported box "sounds" to me like it is tuned for around 65hz, although I am sure the actual tuning freq is probably a little lower.

The typical rule-of-thumb is: rap music = big ported box. rock = sealed box.
The type of sub and amp (power) is also important.

I'm no expert, but I do mess around with this stuff from time to time.
Just my $.02

YMMV

[talnlnky]

Originally Posted by _S7V7N_

When tuning your subs if your box is Tuned to 40 Hz Should the subsonic filter on the amp be set to about 37Hz ? and The Low pass should be about where ? These are just hypothetical Numbers, but am trying to understand how they relate to each other.



Ty

i'll post a picture later tonight (when I get home) from box design software that'll show you a graph of why you need(read: SHOULD HAVE) a subsonic filter if you run ported designs that are tuned above 30hz in cars.

you are correct, below tuning in ported & bandpass designs the box has very little control over the cone movement, which can easily lead to mechanical failures if you have enough power. And 10hz below tuning you don't need much power.

You could probably get away with setting the SS filter a bit lower... but really you won't hear a difference, and it'll just be a little more stress on the sub. so yeah.... 37hz on a 40hz tune is perfect.

[talnlnky]

Originally Posted by Alien Mantis

If you optimize your bass for rap beats, it won't be optimized for rock, and vise versa.

I think you need to look up the word optimized... if you set you sub to play the music exactly how the music was designed to be heard,.... you sub will play it perfectly... Do you really think your sub or amp knows the difference between classical, rap, rock, or someone farting on toilet?

Originally Posted by Alien Mantis

A box tuned to 40hz is pretty low.

maybe for desktop speakers, 40hz is a HIGH TUNE for a sub, Quality home theater subs are usually tuned in the 15-20hz range... Quality car subs usually in the 27-35hz range. Anything above 35, and you got yourself a street beater special which a giant 10dB peak in the response curve.

Originally Posted by Alien Mantis

For me, bass below 40hz is something I "feel" more than I "hear".

Yeah... thats the way it is supposed to be, listen to a nice multi-sub IB install and play some 10hz tones, and you'll feel crazy pressure on your ears, but not hear it... Something that probably only about .05% of car installs can do well.

Originally Posted by Alien Mantis

I like bass optimized around 60-80hz.

that's barely even bass... You're more of a midbass person than a bass person... and if you're a rocker... thats probably why. If I were you, i'd sell your subs, and buy some quality midbass drivers with a lot of x-max, and pay somebody to put them in nice pods in your doors. Maybe even buy an eq... you'd get more of what you want that way, and your bass would be coming from the front and blend well.


Don't take offense... tho my avatar has 2 8's in it.... my install plan has no subs in it... just 8" midbass, 4" mid, tweeter, some crossovers, maybe dual 30band eq's, 500watts worth in amps, and a kickass denon deck. If you get quality midbass drivers, and install them properly... its like have a small sub installed in the car, won't make you go deaf, but it'll sound damn good. I have all the equipment, just no money to install it... and no garage, and all my tools are 500miles away.

[Alien Mantis]

I always thought mid-bass was around 100-200hz, Sub Bass was below 50hz, and plain old BASS was around 60-80hz.

Yeah, you are right, I listen to rock, and I do prefer tighter bass.
( what you are calling mid-bass )

I thought about running an 8", or maybe two of them, but they seem to cost more than a 10" because they are not as common, and my biggest problem has always been trying to get enough SPL on the low end.

So, without spending hundreds of dollars, how can I get a big bass hit, and still keep it TIGHT?
My little shallow 10" in the .5cf sealed box has good SQ, but not enough SPL.
My new Type R 10" in the ported box has way more SPL, but it's not as tight sounding.
It's ALWAYS a trade-off, unless you spend the big bucks.

So.... I gotta find a happy medium.
The only other thing I can try is: put that Type R in a 1cf sealed box.
That might give me the best compromise.
I can get a sealed box for $20, so it's worth it to try it.

I can spend a few bucks... but I am not spending a few "hundred" bucks.

I looked at some 8" subs, but they were all around $80 to over $100 for a decent one. Times TWO that is $200.

I ran a pair of Earthquake 8" subs back in the early nineties, and they did not put out nearly enough SPL.

So I was skeptical about wasting money on 8" mid-bass subs.

My new Type R is the best sub I have tried so far.... so I am happy with it.

[sqcomp]

Earthquake subs...

Had fun with those. I seem to remember 3 magma 15"s and 3 SLAPS passives in the back of a Toyota 2wd truck off an Earthquake D2 amplifier.

That thing was a lot of fun! That enclosure hit it's hardest at 36Hz. Oh man that was a feeling.

[talnlnky]

Originally Posted by Alien Mantis

I always thought mid-bass was around 100-200hz, Sub Bass was below 50hz, and plain old BASS was around 60-80hz.

Yeah, you are right, I listen to rock, and I do prefer tighter bass.
( what you are calling mid-bass )

I thought about running an 8", or maybe two of them, but they seem to cost more than a 10" because they are not as common, and my biggest problem has always been trying to get enough SPL on the low end.

So, without spending hundreds of dollars, how can I get a big bass hit, and still keep it TIGHT?
My little shallow 10" in the .5cf sealed box has good SQ, but not enough SPL.
My new Type R 10" in the ported box has way more SPL, but it's not as tight sounding.
It's ALWAYS a trade-off, unless you spend the big bucks.

So.... I gotta find a happy medium.
The only other thing I can try is: put that Type R in a 1cf sealed box.
That might give me the best compromise.
I can get a sealed box for $20, so it's worth it to try it.

I can spend a few bucks... but I am not spending a few "hundred" bucks.

I looked at some 8" subs, but they were all around $80 to over $100 for a decent one. Times TWO that is $200.

I ran a pair of Earthquake 8" subs back in the early nineties, and they did not put out nearly enough SPL.

So I was skeptical about wasting money on 8" mid-bass subs.

My new Type R is the best sub I have tried so far.... so I am happy with it.

gotcha... didn't realize you were breaking it down into more than just bass/midrange/highs...

ok... sorry for coming off as such a dick then.

[Alien Mantis]

Originally Posted by talnlnky

gotcha... didn't realize you were breaking it down into more than just bass/midrange/highs...

ok... sorry for coming off as such a dick then.

No problem.

I enjoy reading your posts, and I respect your opinion.

It's all good.

[Alien Mantis]

Originally Posted by sqcomp

Earthquake subs...

Had fun with those. I seem to remember 3 magma 15"s and 3 SLAPS passives in the back of a Toyota 2wd truck off an Earthquake D2 amplifier.

That thing was a lot of fun! That enclosure hit it's hardest at 36Hz. Oh man that was a feeling.

Earthquake made great stuff back in the 90's.
I remember when Lanzar amps were top-of-the-line way back before they sold out.
There sure has been alot of "trends" over the years.


Here's a BLAST from the PAST for ya!
Remember these amps? ( They suck, but this one still works! )

[talnlnky]

ok.. here's a graph of some random Alpine Type S sub... I just picked it from the driver database at random... for demonstrating the SS filter concept it really doesn't matter which sub I use.

So, the top graph shows the frequency response of the sub in a decently designed ported box. the box is tuned at 34hz, and you see after 34hz the volume really drops quickly. remember every 3dB is a doubling in volume, so if you go from 0dB to -3dB (or -2dB to -5dB), you've just reduced your volume by 1/2. once your frequency response has dropped by 10dB you really aren't going to notice those tones. For subs... basically forget everything higher than 100hz tho... so use -9dB as your refrence point... so the tones that are below the -19dB point you really won't hear/feel/notice at all. This is actually a really flat frequency response graph for a sub box. Once you put it in a car you'd see a slight boost in the 40hz and lower tones due to cabin gain... so you'd have usable range down to about 25hz. This is a fairly good install, for this sub... a 1.6cuft box 34hz tuning, and its a 12" sub (that's a fairly small ported box for a 12")

The bottom graph shows the movement of the cone of the sub... this sub it looks like has a fairly wimpy 4mm (one way) x-max. Once the sub starts moving past the x-max you will see a big increase in distortion, and will generally start getting close to the sub's mechanical limits... this is for a 12" sub... usually... a 12" sub would have a one way x-max of no less 10mm, some are as high as 40mm, most subs in the $200-$500 rang will have an x-max in the range of 12-25mm one way.

anyways, given 500watts of power, the sub will have the shown cone movement. The dark red line shows when it is playing in the safe range... once you get to 30hz (4hz below tuning) you see the line lighten up... which means you are exceeding the x-max. If you notice that below tuning the cone starts moving like crazy, but if you take the knowledge from the other graph, you know that the volume is actually getting very quite. This is why people keep turning up the volume, but don't hear the low bass get much louder... and then after a few minutes of turning the volume up... and up.. and POOF!.... you just tore the spider, or bottomed out on the backplate which caused the coil to short out and then fry.


SQcomp is all about the grunt work of installs... he's got all that know how and such.... Box design is my specialty.

EDIT: just added a 3rd and 4th graph (2nd picture)... this graph is just like the first, except it has a orange line too. The orange line represents the same sub, except installed in a .5cuft sealed box. Its always nice to show how ported and sealed act differently.

[talnlnky]

Mantis... for your install... to get tight bass, but loud... either go with a small sealed box (qtc of like 1.0 or higher) and a lot of power, and cone area... or go with a low tuned ported box... 25-30hz (for cars, anything below 30hz is really low for tuning). when you drop the tuning on a ported box you really reduce the group delay (transient response time) which is one of the biggest factors in giving you that nice tight sound.... it also helps give you a nice frequency roll off, sometimes very similar to that of a sealed box... which ALSO helps give that nice tight sound. Big peaks in frequency response give the illusion of sloppy muddy bass.

[Alien Mantis]

Good information.

I have been studying graphs like these. If you understand specs and graphs, you can predict how a certain setup will perform.

I was looking at Xmax when choosing a sub. That is one reason I went with the Type R. It has an 18mm Xmax, which is pretty good for a sub that costs around $100, and can handle 500watts RMS +.

I understand that cone diameter + Xmax = SPL.
The more air you can move, the louder the sound.
The faster you can move it, the more controlled it will be.
A 12" sub that has an Xmax of 10mm, is roughly equal to a 10" sub with 16mm Xmax.
Then you factor in the box type and volume, and the power you are putting to it, and you have your setup.

I understand what you mean about the SS filter. If your setup has a SS filter, you can cut all the freq's below that setting, and you don't run the risk of over-excursion on your cone due to it trying to play those super low freq's, even though they drop off sharply anyway on their own.
( This is what "roll-off" refers to. Or sometimes they call it "drop-off". )

Sealed boxes control roll-off much better than ported boxes.
It's always best to just cut those freq's, then the signal never even gets to the subwoofer, but my amp does not have an SS filter on it.
I wish it did, but if you don't try to overdrive your sub, roll-off should keep you safe.
The other benefit of the SS filter is: since the amp isn't even trying to push those freq's, more of the amps power can go towards driving the signals it is supposed to be pushing.

I totally love SS filters.
But my amp doesn't have one.
I also love subs with long linear excursion numbers, because I know I can drive them harder and they will take it and ask for seconds.
A sub with a small Xmax number is easy to bottom out.
They are tight, fast, and responsive, but they don't move as much air, and can bottom out easier.
Less air = less SPL.

It's always a trade-off.

The setup I am running now seems to be good. It's a nice compromise between SPL and SQ. I was thinking about trying the sealed box, but I think I will just stick with this setup. The more I listen to it, the more I like it. So it's all good.

[sqcomp]

...that Urban Audio...

That brings back some memories! I had a four channel one like that in 1996...

[talnlnky]

Originally Posted by Alien Mantis

Good information.

I have been studying graphs like these. If you understand specs and graphs, you can predict how a certain setup will perform.

I was looking at Xmax when choosing a sub. That is one reason I went with the Type R. It has an 18mm Xmax, which is pretty good for a sub that costs around $100, and can handle 500watts RMS +.

I understand that cone diameter + Xmax = SPL.
The more air you can move, the louder the sound.
The faster you can move it, the more controlled it will be.
A 12" sub that has an Xmax of 10mm, is roughly equal to a 10" sub with 16mm Xmax.
Then you factor in the box type and volume, and the power you are putting to it, and you have your setup.

I understand what you mean about the SS filter. If your setup has a SS filter, you can cut all the freq's below that setting, and you don't run the risk of over-excursion on your cone due to it trying to play those super low freq's, even though they drop off sharply anyway on their own.
( This is what "roll-off" refers to. Or sometimes they call it "drop-off". )

Sealed boxes control roll-off much better than ported boxes.
It's always best to just cut those freq's, then the signal never even gets to the subwoofer, but my amp does not have an SS filter on it.
I wish it did, but if you don't try to overdrive your sub, roll-off should keep you safe.
The other benefit of the SS filter is: since the amp isn't even trying to push those freq's, more of the amps power can go towards driving the signals it is supposed to be pushing.

I totally love SS filters.
But my amp doesn't have one.
I also love subs with long linear excursion numbers, because I know I can drive them harder and they will take it and ask for seconds.
A sub with a small Xmax number is easy to bottom out.
They are tight, fast, and responsive, but they don't move as much air, and can bottom out easier.
Less air = less SPL.

It's always a trade-off.

The setup I am running now seems to be good. It's a nice compromise between SPL and SQ. I was thinking about trying the sealed box, but I think I will just stick with this setup. The more I listen to it, the more I like it. So it's all good.

there is more to SPL than total cone displacement... get two 12" subs, put one in a 1cuft sealed box, the other in a 2cuft @ 35hz box, and then play 35hz tones... the Ported box will be a lot louder, but it'll move about 1/4 as much.

The Original Cerwin Vega Stroker subs had a very small x-max... and they were always present at dB Drags World Finals (spl competitions).

If you can cause there to be a lot of resistence on the cone, and still move the cone... you'll have more spl... ported & bandpass boxes do this.

I've only once ran a subsonic filter, I know my installs inside and out, i know what I can get away with, and what I can't. I know that with a given ported setup I can give two, three, or even four times the rms value as long as I keep it limited to a few tones, and only for short burst of time. I've setup installs for people before, told them exactly what they could and couldn't do... and then watch them go to a competition, and try to push the limits.. and BAM... blew the subs because they "thought it could take more".

Best thing anybody can ever do to increase their knowledge of stereo, is to download WinISD, begine designed ported boxes with it, and then make some of those boxes and test them with test tones... you learn a lot fairly quickly.

[Alien Mantis]

I was actually looking at a Cerwin Vega before I bought the Type R.

I had my choices narrowed down to 3 subs:

The Type R, a Cerwin Vega, and an Infinity Kappa.

The Infinity looked nice, had an Xmax of 17mm, could switch between 2 and 4 ohms, but only handled 350watts RMS max.
I'm sure it could handle a 400 watt amp on it, if I was careful to set the gain correctly on the amp, which I always do.

The Cerwin V was nice too, but it only had like a 14mm Xmax.

The Cerwin and the Infinity were both $10 to $20 more.

So in the end... the Type R won.
The Type R had the Xmax, the power handling, the reputation, and it was the cheapest.

I'm sure ANY one of those subs would have worked just fine, and I probably wouldn't even be able to tell much difference between them, if any.

Like you pro's say: the magic happens in the "mid-range".

[_S7V7N_]

Nice info guys, I'm enjoying reading all the Knowledge.

[sqcomp]

There's a reason the magic happens in the midrange...

That's where human's hearing is the most sensitive or attuned.



Hey Taln, can you run a graph for the IDQ 12v3 D4? I'd really like to know what a pair of those in 1 cube each sealed with 750 Watts a piece would do...