Hi everyone.
I'm having some confusion regarding determining a Vehicles resonant frequency and how it plays A Part with the design of subwoofer enclosures. I'm considering building some new vented subwoofer enclosures and from everything that I have read regarding designing the ideal vented enclosure, I really need to take into consideration the vehicle's resonant frequency and if I understand correctly do I build the enclosure and have it tuned to match the resonance frequency of the interior of the vehicle? So hypothetically, if the interior resonant frequency is 60 hertz then I should build my vented enclosure to match that same 60 hertz accordingly? I feel as if I'm completely wrong in the way I'm understanding this. It seems counterproductive to build your enclosure based on that theory as opposed to building it to the specification that Rockford Fosgate outlines regarding vented enclosures for my particular subwoofers. Any information and help to get this cleared up for me is definitely greatly appreciated. This has been bugging me for a while and I would just like to make sense of it all so I can go back to sleeping at night lol.
I'm having some confusion regarding determining a Vehicles resonant frequency and how it plays A Part with the design of subwoofer enclosures. I'm considering building some new vented subwoofer enclosures and from everything that I have read regarding designing the ideal vented enclosure, I really need to take into consideration the vehicle's resonant frequency and if I understand correctly do I build the enclosure and have it tuned to match the resonance frequency of the interior of the vehicle? So hypothetically, if the interior resonant frequency is 60 hertz then I should build my vented enclosure to match that same 60 hertz accordingly? I feel as if I'm completely wrong in the way I'm understanding this. It seems counterproductive to build your enclosure based on that theory as opposed to building it to the specification that Rockford Fosgate outlines regarding vented enclosures for my particular subwoofers. Any information and help to get this cleared up for me is definitely greatly appreciated. This has been bugging me for a while and I would just like to make sense of it all so I can go back to sleeping at night lol.
We spend considerable efforts to avoid resonances developing in our listening environment, and your car is one of these, then why on earth would you ever want to intentionally emphasize/generate a resonant frequency inside a vehicle, or anywhere else for that matter.
If you are intending to listen to low bass music, you will need to reduce/filter out the frequency of the vehicles hypothetical resonance or control/dampen this resonance - not an easy job to do.
When they have those vehicle 'loudness competitions', then they use the vehicle's resonant frequency to gain extra volume but it's not music, just incredibly loud noise.
If you are intending to listen to low bass music, you will need to reduce/filter out the frequency of the vehicles hypothetical resonance or control/dampen this resonance - not an easy job to do.
When they have those vehicle 'loudness competitions', then they use the vehicle's resonant frequency to gain extra volume but it's not music, just incredibly loud noise.
Unless your aim is annoying everyone around your vehicle, and rendering your own driving somewhat incoherent, I would have thought that avoiding the vehicle internal resonance is the thing to do.
So if I understand what you're saying, the vehicle's resonant frequency is not that important unless you were looking for ignorantly low Bass to upset everyone within earshot of your vehicle. As far as my initial question goes, do you build your subwoofer enclosure to match the vehicles resonant frequency even for just a sound quality application? And I understand that every rattle, tick, and vibration that the vehicle has to offer will do its best to disrupt sound quality by offering up their own resonant frequencies and that's why we do what we can to dampen those forces especially Within the vehicle. And thank you for responding.
There is a car audio forum where you will get relevant help. But in answer to your question I'm almost certain the answer is no.
Hey!!! you are killing all the fun in Car Audio. 😱
or did you even for a second think the idea was *actually* listening to Music? 🙄
😀
If your goal is SQ build and tune the box to complement resonant frequency of the vehicle it's going in. If you have 12db of cabin gain at 60hz and the output of the box is -12db at 60hz, you should at least in theory have a flat response in the car. A good parametric eq and crossover settings can do quite a bit to flatten peaks in a vehicle.
Best practice is always do what you can to make it sound good to you first without any eq adjustments. In db competitions where max spl is the goal they do the opposite.
I've transferred the same system from one vehicle to another numerous times over the years and there can be a substantial difference in the frequency range and level of peaks and general SQ as well from one vehicle to another. Some are just easy to make sound good and others require a lot of money and effort and still don't sound just right,
Totally disagree with your ignorantly low bass comment. Pink Floyd dark side of the moon sounds awesome with ignorantly low bass as long as the rest of the system is on par with the bass
Best practice is always do what you can to make it sound good to you first without any eq adjustments. In db competitions where max spl is the goal they do the opposite.
I've transferred the same system from one vehicle to another numerous times over the years and there can be a substantial difference in the frequency range and level of peaks and general SQ as well from one vehicle to another. Some are just easy to make sound good and others require a lot of money and effort and still don't sound just right,
Totally disagree with your ignorantly low bass comment. Pink Floyd dark side of the moon sounds awesome with ignorantly low bass as long as the rest of the system is on par with the bass
Lol. My wife gets all the credit for coining the term " ignorantly low Bass ". It is pretty wild sometimes the difference in performance and sound quality transferring the same system throughout different vehicles. So if the resonant frequency of the inside of my truck Peaks at 60 Hz i should tune my subwoofer enclosure to 60 Hz correct? This is the part where I get a little confused, because based on the specs that Rockford Fosgate recommends for my particular subwoofers installed Within a vented enclosure , the enclosure should be tuned to 40 Hz. I'll stick with the numbers you used in your example : the 12 db of cabin gain would come from playing some test tones starting lets say at 40 Hz slowly working our way up to 60 Hz. and if we are 12 db louder at 60Hz compared to where we started at 40 Hz that would be the cabin gain in our example correct?
Also, in your example you have the box output at -12 db at 60 hz, where does the negative portion of the 12db derive from? If you could help me understand a couple of these things I would sincerely appreciate it and I thank you very much for responding to my posting.
Also, in your example you have the box output at -12 db at 60 hz, where does the negative portion of the 12db derive from? If you could help me understand a couple of these things I would sincerely appreciate it and I thank you very much for responding to my posting.
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I would go with RF's box recommendations only tune it to 5-10hz lower for a vented box. If using tube ports you can always shorten them later if you prefer the 40hz. Fosgate's box recommendations are based on what sounds good in most vehicles, the size of enclosure most people are willing to give up space for and what sizes and tuning frequency will limit power handling-safe excursion. No, don't tune your box to 60hz or you will limit power handling below that. Large sealed and any size vented box with a high box tuning, say 60-70 will limit power handling below that point. A vented box will have increasing cone travel below the box tuning frequency (Fb). The lower you go below Fb the farther the cone will move to the point where given enough power the voice coil will bottom out and require a re-cone if the driver is worth it. If you listen to classic rock or something that doesn't have a lot of low bass say 40hz and up, a 40hz Fb is fine. Listen to music with substantial sub bass with a lot of power and a 40Hz Fb without a low cut or subsonic filter set at just below Fb is begging for disaster.
You are correct on how to figure cabin gain with a test tone cd. 0db is just a reference point where the driver frequency would be at roughly the same level or, flat if you will, regardless of the drivers spl at 1 watt. -12db @60 hz would mean at 60hz the spl is _12db below the 0db level that the woofer / box combination yields at higher frequencies.
I would set your sub amp or stereo's low pass x-over at 60hz as a starting point and adjust from there to personal taste. Also many head units have the bass centered at or close to 60hz and the more advanced ones have multiple center frequencies to pick from. You likely will have better results with a low pass frequency of 70-80hz and a -12db cut with your tone controls or eq. The power your amp is saving at 60hz because the cabin gain makes up for it you can use below and above 60hz.
A flat response doesn't always sound just right in a moving vehicle just as what sounds flat to a microphone may require a little tuning to sound right to your ears.
I've been into all kinds of audio including car audio since I was a kid, I'm 50 now and still love it. Can't bear to have a factory system in my personal vehicle. Current system is 2 type r 1242d alpines 4.4 ft3 @25hz driven with a Memphis 1000w rms monoblock 70hz-down. Subsonic filter on sub amp is at about 23Hz/ Sony xm-754hx 75w rms x4 at 70hz-up to polk 2-way separates front and jbl 6x9 2 ways rear. Moral of the story is I have a lot of bass but the mid-bass up will keep up with the subs/ Tame by some peoples standards but it gets me by and I have had a couple people get out because it was too loud with certain types of bass heavy music.
I have several speaker design books and even learned some algebra (what am I ever going to use this for? LOL) to be able to calculate box volume and vent tuning. I learned a whole lot more from the free winISD box programs I found online. They have a great tutorial and all you need to do basic box calculations are you drivers Vas Qts and Fs numbers. There are many other driver perimeters too and the more you have to enter the better the results. It will design an ideal box for you or you can make it any volume and tuning you want and it will show you curves for frequency response, power handling at different frequencies, cone excursion, group delay, impedance (ohms) curves. You can just enter your driver numbers on the winISD site or down load the programs, there are several to choose from. This gave me so much insight of the trade offs between different box types and vent tuning that it would take multiple pages to relay all of it.
You are correct on how to figure cabin gain with a test tone cd. 0db is just a reference point where the driver frequency would be at roughly the same level or, flat if you will, regardless of the drivers spl at 1 watt. -12db @60 hz would mean at 60hz the spl is _12db below the 0db level that the woofer / box combination yields at higher frequencies.
I would set your sub amp or stereo's low pass x-over at 60hz as a starting point and adjust from there to personal taste. Also many head units have the bass centered at or close to 60hz and the more advanced ones have multiple center frequencies to pick from. You likely will have better results with a low pass frequency of 70-80hz and a -12db cut with your tone controls or eq. The power your amp is saving at 60hz because the cabin gain makes up for it you can use below and above 60hz.
A flat response doesn't always sound just right in a moving vehicle just as what sounds flat to a microphone may require a little tuning to sound right to your ears.
I've been into all kinds of audio including car audio since I was a kid, I'm 50 now and still love it. Can't bear to have a factory system in my personal vehicle. Current system is 2 type r 1242d alpines 4.4 ft3 @25hz driven with a Memphis 1000w rms monoblock 70hz-down. Subsonic filter on sub amp is at about 23Hz/ Sony xm-754hx 75w rms x4 at 70hz-up to polk 2-way separates front and jbl 6x9 2 ways rear. Moral of the story is I have a lot of bass but the mid-bass up will keep up with the subs/ Tame by some peoples standards but it gets me by and I have had a couple people get out because it was too loud with certain types of bass heavy music.
I have several speaker design books and even learned some algebra (what am I ever going to use this for? LOL) to be able to calculate box volume and vent tuning. I learned a whole lot more from the free winISD box programs I found online. They have a great tutorial and all you need to do basic box calculations are you drivers Vas Qts and Fs numbers. There are many other driver perimeters too and the more you have to enter the better the results. It will design an ideal box for you or you can make it any volume and tuning you want and it will show you curves for frequency response, power handling at different frequencies, cone excursion, group delay, impedance (ohms) curves. You can just enter your driver numbers on the winISD site or down load the programs, there are several to choose from. This gave me so much insight of the trade offs between different box types and vent tuning that it would take multiple pages to relay all of it.
Thank you very much for your patience and your time to help clear some of these things up for me. I'm 45 years old myself and after all these years of just hashing systems together on the Fly I've decided that the science behind everything that goes into car audio systems the right way just completely turns me on and I can't get away from it now lol. I do heating and air conditioning for a living and it's kind of the same thing as far as I love what I do everyday because the science behind it always keeps you thinking and on your toes. I have 2 Rockford Fosgate 12 inch P3 subwoofers each in its own 1.9 cu ft vented enclosure (I built) connected to a Rockford Prime 1200-1 mono amp wired to 1 ohm and a pioneer 600-2 that drives the front section of Rockford Fosgate punch pro super tweeters, Rockford 6 inch 2 ways and Rockford 3 inch 2 ways and the rear section Rockford 5 inch 2 ways. Building the enclosures myself to the Rockford "basic" specs have made an unbelievable difference in performance especially on the low end. I can definitely turn heads if I play super deep bass tracks if I want to and also play rock music loud and clear just the same. With your enclosure based around 25 Hz , as you go higher up with frequencies at what point does it start to not sound so good ?
The box they are in is real close to what winISD gives as the ideal vented box for 2 of them in a common airspace. They sound good up to the upper limit of the amp, I think 200hz is as high as the crossover will go. I have them crossed over at 80hz because that's where they blend good with the rest of the speakers.
When setting the gains and crossovers I do the front and rears first with the sub off letting me hear where the lower limit off my fronts and rears are without being masked by the subs. Then turn on the subs and dial in the those to match the fronts and rears. This is a good starting point and eliminates the risk of damaging a smaller driver under distress that's being masked by the subs. I set gains so that I'm hearing just a little bit of distortion with the head unit at max volume and the tone controls flat, If you have a good head unit you really shouldn't get any noticeable distortion from the pre-outs. If someone maxes out the volume its less likely to damage something. If you have older cd's many are recorded at a lower level that they are now and you should still have enough power with the amps you have to make it loud enough. This is best done with the type of music you prefer.
My van seems to have a 40-60hz peak with a dip below that so I need more output where it is with Fb at 25hz. If you haven't done this already watch your subs while playing a test cd and see how far they move at different frequencies. At Fb the cones hardly move compared to frequencies above and especially below that. At 10hz with the subsonic filter turned off or all the way down I'm guessing your subs move almost as much as if they were in free air.
Sounds like you have a pretty good set-up, good to hear you have a separate amp for the fronts and rears. Always kills me these kids with a descent sub setup and then using the stock stereo for the rest of it. I guess if all you care about is bass that would be ok. As a kid I cared more about loud than SQ but still had separate amps for everything. Even a cheap amp is better than running fronts and rears off the head unit. Now if I have to choose I would pick SQ. Both is awesome if you can have it with the funds available.
When setting the gains and crossovers I do the front and rears first with the sub off letting me hear where the lower limit off my fronts and rears are without being masked by the subs. Then turn on the subs and dial in the those to match the fronts and rears. This is a good starting point and eliminates the risk of damaging a smaller driver under distress that's being masked by the subs. I set gains so that I'm hearing just a little bit of distortion with the head unit at max volume and the tone controls flat, If you have a good head unit you really shouldn't get any noticeable distortion from the pre-outs. If someone maxes out the volume its less likely to damage something. If you have older cd's many are recorded at a lower level that they are now and you should still have enough power with the amps you have to make it loud enough. This is best done with the type of music you prefer.
My van seems to have a 40-60hz peak with a dip below that so I need more output where it is with Fb at 25hz. If you haven't done this already watch your subs while playing a test cd and see how far they move at different frequencies. At Fb the cones hardly move compared to frequencies above and especially below that. At 10hz with the subsonic filter turned off or all the way down I'm guessing your subs move almost as much as if they were in free air.
Sounds like you have a pretty good set-up, good to hear you have a separate amp for the fronts and rears. Always kills me these kids with a descent sub setup and then using the stock stereo for the rest of it. I guess if all you care about is bass that would be ok. As a kid I cared more about loud than SQ but still had separate amps for everything. Even a cheap amp is better than running fronts and rears off the head unit. Now if I have to choose I would pick SQ. Both is awesome if you can have it with the funds available.
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