A guy on the Polk forum was asking if he should go ported or sealed for a car sub. I said the following and it got replied to with the following. Who is right, and why?
Originally Posted by Mazeroth
nesticle, go sealed. The cabin gain will make up for the sealed sub's response drop and give you a pretty flat response. A ported sub's tuning frequency will get overcompensated with the cabin gain and sound like poo poo.
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common misconception in car audio
-Cody
I thought I was right but I could be wrong.
Thanks!
Originally Posted by Mazeroth
nesticle, go sealed. The cabin gain will make up for the sealed sub's response drop and give you a pretty flat response. A ported sub's tuning frequency will get overcompensated with the cabin gain and sound like poo poo.
-----------------------------------------------------
common misconception in car audio
-Cody
I thought I was right but I could be wrong.
Thanks!
well cabin gina in a car doesnt work out to 12db an oct perfectly cause there ARE losses, so id estimate 6dboct maybe 8. and with that if you tuned a ported sub low, it woudl be fine.
BUT IMO hes wrong, since if you model the average proted setup in a car you already end up with a peaky box(ive seen +5db at 35hz number times) in fact most car audio guys just tinker with box sizes, if you wanna go lwoer, go a bit bigger and abit lower tune.
so when it comes down to it most car applications are peaky anywy since alot of the drivers are high QTS and high FS.
BUT if i wanted a car setup, id prolly go big ported and peaky, blow your brains out with bass, thats all they reaally want, and as long as theyre not getting that much distortion, and reaches deep enough for most rap music(30hz maybe a bit lower) strongly, its sq.
THIS IS NOT TO OFFEND TRUE AUTOMOBILE SQ ENTHUSIASTS!!! i know youre out there, i know you exist and i know that your systems are impeccibly designed and probably sound fantastic, im just describing the average car audio guys idea of SQ. no offence.
BUT IMO hes wrong, since if you model the average proted setup in a car you already end up with a peaky box(ive seen +5db at 35hz number times) in fact most car audio guys just tinker with box sizes, if you wanna go lwoer, go a bit bigger and abit lower tune.
so when it comes down to it most car applications are peaky anywy since alot of the drivers are high QTS and high FS.
BUT if i wanted a car setup, id prolly go big ported and peaky, blow your brains out with bass, thats all they reaally want, and as long as theyre not getting that much distortion, and reaches deep enough for most rap music(30hz maybe a bit lower) strongly, its sq.
THIS IS NOT TO OFFEND TRUE AUTOMOBILE SQ ENTHUSIASTS!!! i know youre out there, i know you exist and i know that your systems are impeccibly designed and probably sound fantastic, im just describing the average car audio guys idea of SQ. no offence.
Vented subs inside a car are only OK if some care is taken to equalise the otherwise peaky resulting response. Examples:
- Low (below 35Hz) tuning inside big lossy cabins, like vans with a lot of seats and weak wall and ceiling frames.
- Low tuning with high efficiency, low Qts and high Fs drivers (from PA, rarely seen on car-audio) mounted in undersized boxes, resulting in a smooth in-car frequency response.
- Active equalisation involving a little (-6dB or so) notch tuned slightly above the tuning frequency, usually at 45Hz.
-6th bandpass enclosures designed in such a way that the front chamber provides more boost at high bass frequencies that the rear chamber provides in the low end (inside the car).
-Vented boxes undersized and intentionally tuned to have a low Q (around 3). That's usually achieved just by placing a vent in a corner with relatively small cross-sectional area. Such a vent provides very little gain (1dB or so) and thus sealed-like frequency response, but it improves power handling dramatically as cone excursion is usually reduced by more than 50% across a quite wide frequency range (around port tuning).
Of course, the usual "brute-force" bass reflex tuning practices are not suitable for in-car use because they result in a sort of peaky bass quite frustrating.
- Low (below 35Hz) tuning inside big lossy cabins, like vans with a lot of seats and weak wall and ceiling frames.
- Low tuning with high efficiency, low Qts and high Fs drivers (from PA, rarely seen on car-audio) mounted in undersized boxes, resulting in a smooth in-car frequency response.
- Active equalisation involving a little (-6dB or so) notch tuned slightly above the tuning frequency, usually at 45Hz.
-6th bandpass enclosures designed in such a way that the front chamber provides more boost at high bass frequencies that the rear chamber provides in the low end (inside the car).
-Vented boxes undersized and intentionally tuned to have a low Q (around 3). That's usually achieved just by placing a vent in a corner with relatively small cross-sectional area. Such a vent provides very little gain (1dB or so) and thus sealed-like frequency response, but it improves power handling dramatically as cone excursion is usually reduced by more than 50% across a quite wide frequency range (around port tuning).
Of course, the usual "brute-force" bass reflex tuning practices are not suitable for in-car use because they result in a sort of peaky bass quite frustrating.
Eva said:
I do a similar thing with 4th order bandpass (rising response instead of a flat pass band), but not all drivers are suitable for this.
I have also had good success with short, heavily packed transmission lines.
I've found cabin gain to usually be about 8-9dB/Oct starting around 60-90Hz depending on car, big cars start lower. because of this I find sealed boxes tend to work better generally but ported can work well if designed with this response in mind.
Sealed is easier, but you can't really generalise. For SQ you should match the cabin gain to the rolloff, and you can do this with either sealed or vented.
You can find measured examples of cabin gain at www.diysubwoofers.org
It's quite easy to get a vented subwoofer with a car sub driver to match cabin gain. There is the risk of unloading below tuning to consider where you have rare examples of music with VERY low high amplitude bass.
You would think that typical cabin gain of 12db/octave below 60-80 Hz to mean a sealed box. If your particular design involves a situation where output is xmax limited, you could have a peaky response and then eq out the peak to get flat again, then reduce excursion demands on the driver, or reduce distortion.
You can find measured examples of cabin gain at www.diysubwoofers.org
It's quite easy to get a vented subwoofer with a car sub driver to match cabin gain. There is the risk of unloading below tuning to consider where you have rare examples of music with VERY low high amplitude bass.
You would think that typical cabin gain of 12db/octave below 60-80 Hz to mean a sealed box. If your particular design involves a situation where output is xmax limited, you could have a peaky response and then eq out the peak to get flat again, then reduce excursion demands on the driver, or reduce distortion.
I'm getting a dead link for the cabin gain examples on diysubwoofers site, anyone got another link or can point me in the right direction.
Ahhh, you're right, it's gone now. You could contact John and DB at AE speakers to see if it is located somewhere, or if they still have the info
That top post is wrong! Ported enclosures in cars is fine if you know what you want from the response and design it with that in mind.
I measured in sealed enclosure car response with a mic and then designed a ported pox provide an almost completly flat resoponse in car, with tuning low like 26hz i was able you pull most of the group delay around fb to area where it is less noticable.
I managed to get a almost flat response between 22hz and 62hz.
It sounded very good, better than some top sealed installs I have heard.
I measured in sealed enclosure car response with a mic and then designed a ported pox provide an almost completly flat resoponse in car, with tuning low like 26hz i was able you pull most of the group delay around fb to area where it is less noticable.
I managed to get a almost flat response between 22hz and 62hz.
It sounded very good, better than some top sealed installs I have heard.
Re: sub boxe help
We can't tell you that without knowing the cabin gain of your car and seeing at least a simulation of your sub. If you try simulating, then a guess is at least possible.
mandd said:
We can't tell you that without knowing the cabin gain of your car and seeing at least a simulation of your sub. If you try simulating, then a guess is at least possible.
xstephanx said:
Even with distortion, it is often satisfactory & acceptable to the user!
I've found over the years that the majority of subwoofer users are in it for the sound effects rather than the sound quality. I am certainly guilty of that practice in my past vehicles too. The next time around, it will likely consist of a pair of sealed 8" or 10" subwoofers operating well below their maximum output capability with plenty of power to stay out of clipping. I am getting to old to take enjoyment from my license plate flapping.
I'll tell you something that is true about ported subs in cars....
Every comercially made sub box built for car audio use that I've EVER seen has tuning at or above 30hz(typically 35hz and above).
This generates a big peak around 40-50hz and falls off rapidly below fb.
I've built many car subs for friends and what I've found is that tuning between 25-30hz is what works best with most subs. Below 25hz the cabin gain seems to start losing effect and you get what sounds nearly identicaly to a sealed box. Above 30hz and you start to get into the peaky response. I usually size the enclosure volume based on the amplifier power present(to prevent xmax because most of the people I've built boxes for wouldnt know to turn it down when their driver starts farting) and size constrants placed by the customer.
Every comercially made sub box built for car audio use that I've EVER seen has tuning at or above 30hz(typically 35hz and above).
This generates a big peak around 40-50hz and falls off rapidly below fb.
I've built many car subs for friends and what I've found is that tuning between 25-30hz is what works best with most subs. Below 25hz the cabin gain seems to start losing effect and you get what sounds nearly identicaly to a sealed box. Above 30hz and you start to get into the peaky response. I usually size the enclosure volume based on the amplifier power present(to prevent xmax because most of the people I've built boxes for wouldnt know to turn it down when their driver starts farting) and size constrants placed by the customer.
xstephanx said:
Ahhhhhhh, it's so true. We try so hard yet all they want is to be deaf at the age of thirty. Lucky for me, my friend is quite aware of high quality whether or not he knows it. I am currently working on his system for his Jeep, pending cash flow of course. Four channel amplifier and speakers coming up!
xstephanx said:
Yes we are out there. I'm reworking my old truck system, 97 Chevy extended cab. The subs I chose were some old Audax 8" that modeled peferct in a small enclosure which fits under the rear seat. Out of sight and out of mind. Plus the placement allows the speakers to face out. I'm still working on the mid and tweeter relocations, but already the bass is nice and smooth.
I'm using SoundEasy on a laptop to help me along and getting some very good results on the theoretical placements and how the speakers sound temped up.
I'm drawing a lot of attention from the older crowd, folks my age 48ish, that want good clean sound without the kid booms. Looks like this could boom (no pun intended) into a very good side business. I've got a friend that just spent over $2500 on a system and is not happy. I have less than $500 in parts and my little system sounds far better.
Dryseals,
It's a fun, challenging side business that's for sure. I have some strict stipulations for my customers but every single person that has heard one of my systems understands and is willing to wait.
Another thing to note, is a website dedicated to our work. Or, a forum where only information pertaining to our design, component and install decisions are outlined. It would be a great way to share information and experiences with certain cars to others.
PS, I love the Audax stuff, very high quality and smooth beyond belief.
It's a fun, challenging side business that's for sure. I have some strict stipulations for my customers but every single person that has heard one of my systems understands and is willing to wait.
Another thing to note, is a website dedicated to our work. Or, a forum where only information pertaining to our design, component and install decisions are outlined. It would be a great way to share information and experiences with certain cars to others.
PS, I love the Audax stuff, very high quality and smooth beyond belief.
Bose(o),
Web site coming soon, I'll be creating my own. I used to do sound systems for clubs and shows many years ago. The late nights and dirt pay led me away. I stayed out of the audio scene for almost 20 years and then fell back into it when the wife wanted a new surround set in the house.
I was at the stores looking at the speaker setups and came to the conclusion that they were selling a name and not sound quality. So I set out to build my own. I drug out some old gear, audio generator and began purchasing some replacement gear, scope, freq counter, etc etc. Then stumbled on SpeakerWorkshop. Played with it for a few months but could not get stable results in the manner I wanted them.
I then bought SoundEasy and have been very pleased with the readings.
I've been building street rods and furniture for the last twenty years and I have a nice shop 30' X 60' brick with two small offices. One office was transformed from engine building to speaker testing.
I built my first couple of sets of speakers and they still remain in the shop. People have commented on how good they sound compared to the store bought, enough so that folks have brought their friends over to listen and then the requests for me to build them some started rolling in.
So now I have two things going, for the home and for the car. My shop is still a wreck, I've been working tons of overtime since hurricane Rita plowed through us, just now getting back to a normal schedule.
Hopefully by the end of the summer, I'll have some things to throw up on my web site. I too have certian desgn goals that I will not compromise, the quality of the sound must come first. It's hard to explain to some folks that just because you spend $600 on a woofer does not mean it will work as you want it to. But by running SE on their speaker and then showing the plots, they begin to understand.
One thing I have learned since messing with the speakers and the chat boards, it's a lot like cars and motors. The average Joe lives by advertizing. I can't begin to tell you how many budget motors I've built that would clean house on the high dollar rigs. It's all a system, matching the components correctly can make or break a system.
Web site coming soon, I'll be creating my own. I used to do sound systems for clubs and shows many years ago. The late nights and dirt pay led me away. I stayed out of the audio scene for almost 20 years and then fell back into it when the wife wanted a new surround set in the house.
I was at the stores looking at the speaker setups and came to the conclusion that they were selling a name and not sound quality. So I set out to build my own. I drug out some old gear, audio generator and began purchasing some replacement gear, scope, freq counter, etc etc. Then stumbled on SpeakerWorkshop. Played with it for a few months but could not get stable results in the manner I wanted them.
I then bought SoundEasy and have been very pleased with the readings.
I've been building street rods and furniture for the last twenty years and I have a nice shop 30' X 60' brick with two small offices. One office was transformed from engine building to speaker testing.
I built my first couple of sets of speakers and they still remain in the shop. People have commented on how good they sound compared to the store bought, enough so that folks have brought their friends over to listen and then the requests for me to build them some started rolling in.
So now I have two things going, for the home and for the car. My shop is still a wreck, I've been working tons of overtime since hurricane Rita plowed through us, just now getting back to a normal schedule.
Hopefully by the end of the summer, I'll have some things to throw up on my web site. I too have certian desgn goals that I will not compromise, the quality of the sound must come first. It's hard to explain to some folks that just because you spend $600 on a woofer does not mean it will work as you want it to. But by running SE on their speaker and then showing the plots, they begin to understand.
One thing I have learned since messing with the speakers and the chat boards, it's a lot like cars and motors. The average Joe lives by advertizing. I can't begin to tell you how many budget motors I've built that would clean house on the high dollar rigs. It's all a system, matching the components correctly can make or break a system.
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