# Subsonic filter question



## jdubu420 (May 21, 2015)

Hello,

I am attempting to get my system tuned perfectly. I am running one x12 d4 in a box built to factory specs. 

It is supposed to be tuned to 32hz. However my amp does not have a subsonic filter and the LP filter only goes down to 40hz.

My understanding is that when the LPF is set to 40hz it will only play bass below 40hz? Correct?

Secondly it is my understanding that if I use the o-scope to tune to 32hz, any track that plays below that frequency *WILL* clip. I have spent over 3k so far on my entire audio system and do not want to damage any components. So therefor a subsonic filter becomes crucial correct?

And thirdly if my two previous questions are indeed correct, can anyone recommend a good yet cheap subsonic filter?


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## SkizeR (Apr 19, 2011)

1) what amp is it?
2) yes, low pass frequency filter cuts out higher frequencies and lets low frequencies pass
3) are you trying to say that your box is tuned to 32 hz, and if it plays anything lower than that itll be clipped? if thats what your asking, then thats false. a subsonic filter is important for ported boxes because below tuning frequency the sub will pretty much just go crazy and can damage the sub. 
4) you cant really buy a subsonic filter. its either built into your amp, is a feature on a head unit, is done with a dsp, or an active crossover. if you must have one, just look for a 2 channel active crossover that has a HPF that is able to go that low


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## Weigel21 (Sep 8, 2014)

Wow, you seem a little confused. 

You need a SSF to protect the sub from unloading below the tuning frequency of the enclosure, though truth be told, damage doesn't occur from say a 31Hz frequency when tuned at 32Hz. It would be frequencies of say 28hz and lower that would be of more concern in terms of potential damage to the sub. 

It is often said/recommended to set a SSf filter within 5Hz below the tuning of the enclosure, though I've heard it said a SSF must be set within 1/2 an octave below the tuning, so I am ASSUMING the within 5Hz below tuning is the extra precaution way to go. 

The LPF has a roll off slope, may well be 12dB/Oct, but without knowing the amp, I can't be certian. My point, the frequencies above 40Hz (if set to such) will still play, but they will be attenuated XXdBs/octave. 

Tuning to 32Hz using an O-scope? Are you meaning setting your gains using a scope? 

You set your gain using test tones but it's the recording level you are needing to worry about. If you use a 0dB recorded tone, clipping shouldn't happen unless in the recording itself. Using a test tone of 0dB however will result in lack luster performance. Thus, one used attenuated test tones, as music is dynamic and recorded at varying levels of attenuation. -10dB would be the most I'd use, but some go as far as -15dB. Now the use of attenuated tone will result in audio played that is recorded at stronger levels to potentially clip. 

As for a SSF, Harrison Labs makes FMOD filters you can get.


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## Weigel21 (Sep 8, 2014)

Better than nothing.

Harrison Labs FMOD Inline Crossover Pair 30 Hz High Pass RCA


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## jdubu420 (May 21, 2015)

Accidental double post...


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## jdubu420 (May 21, 2015)

Thank you guys for so much info so fast. 

My amp is a JL Audio G-MAX.

I have read the bcae websites guide to setting the gains using an o-scope and understand the tones / Concepts.

However in the guide it states that if you set the gains with a 32 hz sine wave recorded at -0db, if a 31hz 0db tone is played it will clip... Therefor a SSF should be used to cut of all frequencies below 32hz if that is used to set the gains correct?

Otherwise you'd have to inspect all music to make sure it does not contain anything below 32hz to play music at max volume safely and have the most bass, for sure safely.

I'm for mmax safety first and foremost. Then SPL. I'll play or modify tracks either way, but I still want to be able to listen to new music without worry.

I'm also the set it and leave it type. So I want to get the equipment I need to have it be maintenance free.

I saw some bass drivers on sonic electronics. For 60 bucks there are some nice soundstream and other units that seem to be pretty awesome. From what I understand some can take a range of upper frequencies and lower frequencies and convert them into a lower, effective frequency for your woofer.

I love this idea as I know my EDM music could hit a lot harder. The only music I've found that hits good is newer rap set below 40hz. I don't think the x12 and this box picks up much of anything above that. At least it puts out weakish bash. Sounds good loud or quiet, so why ever have it quiet. I want consistent hard bass. I enjoy the massage and the bbass produced by the x12 does not hurt the ears.


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## emilime75 (Jan 27, 2011)

OK, it's pretty clear you're not very experienced or knowledgeable about car audio or audio systems in general. Nothing wrong with that, we all start somewhere.

It's great that you're getting into the hobby and that you're reading and asking questions. However, you have to understand what it is you're reading and that'll come with more reading, more questions and actual experience.

How about you start with a full rundown of the car and system installed. Everything, year, make and model of the car, head unit, amps, subs, speakers, processors...everything you've got. We can, most likely, make better suggestions as far setup goes once all that has been laid out.

As far as your original question about the HPF(High Pass Filter) for your sub, you really only need that if you plan on driving it hard and loud. Do you? HPFs come in various types, as some already started to point out. They can be devices that only do that, limit the higher frequencies getting through or, they can be part of a device that does other features. The cheapest and least effective are the passive devices like the F-Mods. They're fixed in frequency and their cut off slopes are very shallow and really offer little, if any benefit in your situation. The best, and most usually most expensive, would be a DSP. Most of these have select-able frequencies and cut off slopes, many of which go up to 48dB per octave. DSPs also offer a ton of other very useful features but, we'll forget about those considering the situation.

Something you have to consider, no HPF, regardless if it's a passive or a super high end active device will cut all frequencies below your selection and will actually start attenuating above your selected frequency. In other words, let's say you have a HPF that operates at 12dB per octave and set it to 30Hz. If you looked at a graph, typically, it would be 3 dB down at 30Hz and keep dropping the lower it goes. Also, the cutoff will get steeper and steeper the lower it goes. This is why people usually set their active LPFs a little bit below their target frequency. If you want no attenuation at 30Hz, you set it to roughly 25, just keep in mind that frequencies below 25 will still be heard, just not as loud.

That, believe it or not, is the simple version.


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## Weigel21 (Sep 8, 2014)

Using a 0dB recorded tone "should" result in no clipping despite what frequency is being played (within the amps playable range). Now I know some frequencies are "easier" for an amplifier to produce power on than others, but again, I'm just not understanding the "it will clip if you play a 31Hz tone". So what if you play a 33Hz tone, or GOD forbid, music, which has all sorts of frequencies? Besides, what's the likelihood of playing any music with frequencies below 32hz recorded at 0dB. I'd say slim. Not a lot of music has frequencies recorded at 0dB and even less of it is going to be frequencies of 31Hz and lower. 

Honestly, I think you're in for a bit of a let down using a 0dB tone, as you'll probably never get the full rated power from your amp using such. I mean a lot of music is recorded attenuated -5dB or more.


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## jode1967 (Nov 7, 2012)

I would recommend playing some test tones at known frequencies to see where the sub starts attempts to unload. That is the point at which you need to have ssf protection


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## emilime75 (Jan 27, 2011)

As far as a cheap, but good, HPF... I would suggest the MiniDSP 2x4 in a box. Straight from MiniDSP, it will cost you $135 for the DSP, shipping and the right plugin. Download the plugin to either a mac or PC, open the GUI, connect USB to DSP, make your settings, unplug USB and you're done. You can always go back and make changes later if you want.


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## jdubu420 (May 21, 2015)

emilime75 said:


> OK, it's pretty clear you're not very experienced or knowledgeable about car audio or audio systems in general. Nothing wrong with that, we all start somewhere.
> 
> It's great that you're getting into the hobby and that you're reading and asking questions. However, you have to understand what it is you're reading and that'll come with more reading, more questions and actual experience.
> 
> ...


I only have experience with computers and electrical systems.
So yes you are quite right that I do not even close to fully understand tuning in general.

My current setup is:
1992 Honda civic vx 1.5l d15z1
180amp singer alt
exide edge 51r agm battery
Big 4 + more

1200 rms mono JL Audio G-Max
Focal 165v Component kit
Focal 200w solid 2 channel amp
6 x 9s and tweets with cross over
1250w Sundown X12 D4
DEH-80prs head unit

I will check back in when I get off work in another 4 hours.

Thank you again for all your help everyone. I am stuck in a little town where no one appreciates car audio. Unfortunately the only shop here isn't much help. He doesn't even use an o-scooe to tune the equipment he installs. I prefer to do things right...


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## Weigel21 (Sep 8, 2014)

An O-Scope is FAR from needed to properly setup and tune a system. Most could set their gains just as accurately by merely playing test tones and listening for the tone to change from a hum to a buzz upon 1%THD. And many amplifiers even make a higher pitched tone when they venture into clipping. On top of this, there are people out there with a knack for setting gains and tuning with just their ears (not insinuating your local installer is one, but...). 

just a few links as food for thought. 

What Is Distortion?

Using test tones to set amplifier gain

https://www.youtube.com/watch?v=WhrDqke8BKo


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## 1996blackmax (Aug 29, 2007)

Weigel21 said:


> Better than nothing.
> 
> Harrison Labs FMOD Inline Crossover Pair 30 Hz High Pass RCA



Yup.

That's actually what I ended up using for my daughter's car. The older ARC DXi amp I used didn't have a subsonic filter. I installed a ported Boston sub, so I got the fmods. Worked out well for her system.


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## jdubu420 (May 21, 2015)

So I forgot to mention that I do to like to play as loud as I can, without pause, while being positive my equipment is safe for the next 5-10 years at least.

Going to buy the minidsp that was mentioned. Good price. I have been told by many people here that a DSP is crucial.

I'm going to use JL Audio's recommended gain setting method that uses a DMM and a 50hz -5db SW.
Once I get a new set of probes for my pocket o-scop... it only came with one probe.

If anyone has any links to good tutorials, or other related info (BOOKS?) that would be wonderful


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## jdubu420 (May 21, 2015)

Soundstream MPQ-5XO 4-Band Parametric EQ w/ Crossover
2 way active cross over by soundstream?

The features sound right to me. Does anyone know if this would be a good option?

It looks like the minidsp 2x4 is designed for home audio? Seems a little complex... and I read a review stating that it rounds off the frequency you set it to, so it's not quite as accurate as some.

I just want good quality sound, safety, and the max steady SPL I can get out of my setup without an insane hassle at this point...

I just want my bass back  been without for a few months since my amp failed and had to be repaired. I'm almost certain it was clipping due to the HP/LpF being set wrong, and gain slightly too high.


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## T3mpest (Dec 25, 2005)

At 32hz you can get away with no SSF and not have any issues. That sundown X12 has A LOT of mechanical excursion, they are going to be impossible to bottom on a 1200 watt amp. What kind of music are you playing through it, unless it's bass enhanced and slowed a bunch, I'm 100% confident, it'll never be an issue. Even if you are a slowed music fan, I'd still be 99.999% sure you fine.

For reference, my sundown nsv3 has A LOT a more motor force and on a 3800 watt amp wired at 1ohm, I ended up with thermal failure over time, but never even had a HINT of bottoming out, playing chopped and screwed music and other stuff that went REALLY low. Mechanically it laughed at that amp, even going full tilt!

Now the X isn't a NSV3, but it's the same basket, same spider (mine had X spider) a shorter coil and less motor height. I'd be super suprised if the xmech was that drastically different. 1200 watt rated amp on that sub is basically tickling it, sundown drivers generally takes 1.5-2x rated if your being careful, as the RMS is designed as an idiot proof number.

The X line also is a bit lacking in the motor department, that's where the price difference is compared to the zv4 and nsv3 series, the motor. The coils are all 3 inch, although it does get longer as you go up in series.. Still, the X's value is in the fact it has a bit less motor force than the other models, while it does use the same baskets and other high excursion platform parts.

Anyways on an X series, I'd set the lpf to approx 60hz. It doesn't have a super great top end, you can play with a higher or lower crossover using your ear to help it blend with your mids, but generally that's going to a good ballpark for where the driver is going to be dropping off.


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## cubdenno (Nov 10, 2007)

T3mpest said:


> At 32hz you can get away with no SSF and not have any issues. That sundown X12 has A LOT of mechanical excursion, they are going to be impossible to bottom on a 1200 watt amp. What kind of music are you playing through it, unless it's bass enhanced and slowed a bunch, I'm 100% confident, it'll never be an issue. Even if you are a slowed music fan, I'd still be 99.999% sure you fine.
> 
> For reference, my sundown nsv3 has A LOT a more motor force and on a 3800 watt amp wired at 1ohm, I ended up with thermal failure over time, but never even had a HINT of bottoming out, playing chopped and screwed music and other stuff that went REALLY low. Mechanically it laughed at that amp, even going full tilt!
> 
> ...


Great advice!! 

Also, odds are the sub will at most see 2/3s of the "rated" power of that amp. Nothing wrong with the amp, just the natural things that occur loading a sub into an enclosure and playing music. The natural impedance that the amp "sees" is never the unloaded speaker DCR (direct coil resistance. In your sub's case, 2 ohms). Chances are the impedance rise not taking compression into effect (which for your sub with good cooling designed in and a 3" coil AND the power on tap, should be minimal) the amp should se ea minimal 4-6 ohm at the lowest.


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## gstokes (Apr 20, 2014)

Bass processors such as some of the units from Soundstream and other similar units have a built-in subsonic filter..


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## jdubu420 (May 21, 2015)

cubdenno said:


> Great advice!!
> 
> Also, odds are the sub will at most see 2/3s of the "rated" power of that amp. Nothing wrong with the amp, just the natural things that occur loading a sub into an enclosure and playing music. The natural impedance that the amp "sees" is never the unloaded speaker DCR (direct coil resistance. In your sub's case, 2 ohms). Chances are the impedance rise not taking compression into effect (which for your sub with good cooling designed in and a 3" coil AND the power on tap, should be minimal) the amp should se ea minimal 4-6 ohm at the lowest.


Sounds like I need to add another amp into the equation or upgrade my amp... damn....


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## jdubu420 (May 21, 2015)

gstokes said:


> Bass processors such as some of the units from Soundstream and other similar units have a built-in subsonic filter..


That was my main motivation for buying one. But is soundstream a good brand for that sort of thing?


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## gstokes (Apr 20, 2014)

jdubu420 said:


> That was my main motivation for buying one. But is soundstream a good brand for that sort of thing?


Absolutely and Audio Control makes the Epicenter but I'm not sure of its specifications, you may want to contact them beforehand..


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## cubdenno (Nov 10, 2007)

jdubu420 said:


> Sounds like I need to add another amp into the equation or upgrade my amp... damn....


Naw.

Unless you just feel the current system is just not providing... 

Doubling power gains a lousy 3 decibels. That's it. In the mean time, trying to power a 2400 watt amp from the electrical system means in most cases for listening habits, an upgrade as well. 

With your equipment, you are fine. You can always play with the enclosure design to help maximize output. Just give the current system a listen.


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## cubdenno (Nov 10, 2007)

Problem with bass processors are that they hit the brick wall of the available power of the amp faster. Similar to bass boost. I get that the epicenter is a "bass restorer" but with a twist of the knob it will boost.


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## jdubu420 (May 21, 2015)

cubdenno said:


> Naw.
> 
> Unless you just feel the current system is just not providing...
> 
> ...


I 

I was very happy with the output I was getting for 3 months before I burned the amp up. Luckily it's on the way back from JL Audio after getting repaired.

I have been playing around with the settings on my Focal Solid-2channel 200w amp for the mids/tweets. I've discovered something very interesting over the past 6 months of experimentation with the kit.

I started out with setting the head unit at 50 and setting the gain to about 1/5 to 1/4 of max volume to match the head-unit volume. I also enabled the HPF and set it to roughly 80-100HZ. I should mention that I was using the HPF on the amp in conjunction with two inline cross overs that came with the focal component kit. NOT ONLY THAT but I also tried out a lot of the built-in equalizers and that just made things worse. Flat is indeed the only way to go it seems?

It sounded like ****, not that loud... and you would hear loud pops if it was playing as loud as I thought they should be able... The highs were too high, and the low/mid bass not hard enough with hardly any kick.

I then read another guide that mentioned it was terrible to use a cross over and a HPF at the same time... Now that I understand how they work, it makes a lot more sense why.

I have read that many people with deh-80prs can turn it up to 59/62 without clipping either highs or lows. So I turned my gain all the way down, Set the HU at 59, Turned my HP filter off to feed the cross overs a full signal, and boom. No need to turn the gain up AT ALL. When I tried to turn the gain up, just out of curiosity, it started to sound slightly distorted right away. So I'm leaving it completely off.

Amazing. They are so much more clear. Bass hits harder (and actually sounds good), everything responds faster, highs are crisp are clear, not ear piercing and annoying. Sounds like it should... finally. It's sad that my local car audio guy didn't give me any advice or explanation of how to set the filters. I lost one 6X9 in the process and my amp. 

In conclusion, it was an expensive mistake... but well worth what I learned from it. 

Has anyone read any good books on car audio?


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## jdubu420 (May 21, 2015)

cubdenno said:


> Problem with bass processors are that they hit the brick wall of the available power of the amp faster. Similar to bass boost. I get that the epicenter is a "bass restorer" but with a twist of the knob it will boost.


This confuses me somewhat. Are you saying that they are NOT a good idea because you will get less output with a bass processor? Or are you saying if you use the wrong features, or if they are built in, they could be problematic?


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## jdubu420 (May 21, 2015)

cubdenno said:


> Great advice!!
> 
> Also, odds are the sub will at most see 2/3s of the "rated" power of that amp. Nothing wrong with the amp, just the natural things that occur loading a sub into an enclosure and playing music. The natural impedance that the amp "sees" is never the unloaded speaker DCR (direct coil resistance. In your sub's case, 2 ohms). Chances are the impedance rise not taking compression into effect (which for your sub with good cooling designed in and a 3" coil AND the power on tap, should be minimal) the amp should se ea minimal 4-6 ohm at the lowest.


I checked the impedance with a DMM at the end of the doubled up 12 gauge speaker wire, It read 1.9 to 2.0 Ohms. Closer to 2.0...

If there isn't much difference between 1200w and 2400w of power, why bother?

I've read that there is however a big increase in output the closer you get to the subs rated power... so... trying to make use of what you said, shouldn't I need a 1600w or greater amp? 2/3 of that would be close to the subs recommended 1250w.

I built my box with the Sketchup designs on Sundown Audio's website. Ported, 32hz. I've done a lot of construction and framing so building it was an easy task and nothing is more than 1mm off. I'm sure they tested the box, and it worked well, so  I just need to get everything dialed in perfectly...


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## iamstubb (Sep 6, 2013)

jdubu420 said:


> Soundstream MPQ-5XO 4-Band Parametric EQ w/ Crossover
> 2 way active cross over by soundstream?
> 
> The features sound right to me. Does anyone know if this would be a good option?
> ...


I would highly recommend the miniDSP. The Balanced 2x4 is made to work with car audio with the added miniDC power supply and it produces great results. It really isn't that hard to use and there is lots of advice on the forum. The components are good, the price is right and the options for crossover and EQ are nearly infinite. You can really get the sub just right and maximize sound with a steep crossover. They also just released a unit specifically for car audio that is called a 6x8 but is really a 4x8 for analog or 2x8 for digital input.


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## jdubu420 (May 21, 2015)

iamstubb said:


> I would highly recommend the miniDSP. The Balanced 2x4 is made to work with car audio with the added miniDC power supply and it produces great results. It really isn't that hard to use and there is lots of advice on the forum. The components are good, the price is right and the options for crossover and EQ are nearly infinite. You can really get the sub just right and maximize sound with a steep crossover. They also just released a unit specifically for car audio that is called a 6x8 but is really a 4x8 for analog or 2x8 for digital input.


OK I'm set on getting the MiniDSP. You've convinced me.

My only confusion now is whether I really *need* the 6X8 model for my equipment, or if the 2X4 would be just as good SQ/SPL-wise. 

And secondly... Since I only have a 2 channel amp, I need the installed cross-overs that came with my focal kit. To use the DSP properly with the 6X9's and Tweeters wouldn't I need to remove the inline cross-overs that came in the kit and use a 4-channel amp? 

...Oh... and... Since my amp's low-pass only goes down to 40hz, isn't that going to limit my results with the DSP? 

Sorry for three questions in one post... I'm just full of questions...

I'm very grateful for all the knowledge you all have shared with me...
Thanks as well for not treating me like an idiot. I may have a hard time grasping certain concepts in this industry, but I swear that I flourish in others... (like wiring)


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## iamstubb (Sep 6, 2013)

jdubu420 said:


> OK I'm set on getting the MiniDSP. You've convinced me.
> 
> My only confusion now is whether I really *need* the 6X8 model for my equipment, or if the 2X4 would be just as good SQ/SPL-wise.
> 
> ...


You can use the DSP with both your sub and component setup keeping the passive crossovers. The idea is to use the miniDSP to band pass the sub say 30Hz-70 Hz, and to let the 6x9/tweet combination play from 70Hz on up (just guessing). You won't need any of the filters on your amp. Even though the components are running together as a unit, you can use the EQ functions of the DSP as well as the timing functions to get the best out of them. You can run all active with more amp channels but work with what you have now and see how it goes. You can always upgrade and go with all active speakers later.


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