CSI_MuNkY Posted December 21, 2006 Report Share Posted December 21, 2006 As I have mentioned before, for the spring I want build myself a custom box built for my car. My main reasoning is because I think I can use the space in the trunk more efficiently and make it look better at the same time. I've noticed in some pics that some ppl have the subs facing both directions, so some subs look as though they are pointing in to the box. What is the reasoning for this? Also, I know that subs have a deign volume speced out for them, how does this sort of arrangement effect the volume required by the subs? If it makes any difference, the 2 subs I will be using are 10" Rockford Fosgate P2 punches Jamie Quote Link to comment Share on other sites More sharing options...
intern8tion9l Posted December 21, 2006 Report Share Posted December 21, 2006 i always thought inverting the subs was for looks. i think they perform the same, but you have to wire pos to neg and neg to pos. correct me on this, audio guys Quote Link to comment Share on other sites More sharing options...
slick Posted December 21, 2006 Report Share Posted December 21, 2006 For the price you will be paying for the p2's, you can get much better subs. That is, unless you have bought them already. Quote Link to comment Share on other sites More sharing options...
CSI_MuNkY Posted December 21, 2006 Author Report Share Posted December 21, 2006 bought them already, used, paid $200 for both subs and the box they came in, and right now the subs are on at future shop for $149 each... so right there thats a savings of $100 and a free box. Now, my brother said that facing my box backwards or placing the box as far back in the trunk as possible (so the sound reflects off the back sooner) is the way to go. So I didn't knwo if inverting them was a good way to do this... Jamie Quote Link to comment Share on other sites More sharing options...
gtphill Posted December 21, 2006 Report Share Posted December 21, 2006 Two reasons for having the subs face the other way. 1. Heat dissipation. Only between 1-3% of the electrical energy pumped into your subs comes out as sound, the rest is dissipated heat! Pretty lousy.... Having the magnet face out improves cooling of the voicecoil, lowers what is called power compression. This is an old school trick that professional audio companies have been doing for years. 2. Some distortion reduction. Most speakers do not have completely symmetric magnetic fields, and therefore move slightly different on the out than on the in. There are some design tricks to minimize this, but it is often there a small extent. Having two of the same driver moving the opposite ways of each other tends to help cancel these effects. There ya go! Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted December 21, 2006 Report Share Posted December 21, 2006 1. Heat dissipation. Only between 1-3% of the electrical energy pumped into your subs comes out as sound, the rest is dissipated heat! Pretty lousy.... Having the magnet face out improves cooling of the voicecoil, lowers what is called power compression. This is an old school trick that professional audio companies have been doing for years. Its called a ported box You can face the subs either way, but having them fire into the box, your phase is 180* out of phase. Where as having the subs fire out of the box, they are 0* in phase. Basically they are opposite. Ive never heard a sub that fires into the box, so I have no idea how it sounds. And unless your subs basket, coil, etc looks good and you plan on doing somthing to do, dont have them fire out of the box... Just put them in the box, firing out of the box, and have them flush with the box. I wish I would have done that. Quote Link to comment Share on other sites More sharing options...
gtphill Posted December 22, 2006 Report Share Posted December 22, 2006 1. Heat dissipation. Only between 1-3% of the electrical energy pumped into your subs comes out as sound, the rest is dissipated heat! Pretty lousy.... Having the magnet face out improves cooling of the voicecoil, lowers what is called power compression. This is an old school trick that professional audio companies have been doing for years. Its called a ported box The actual net flux of air into and out of a ported box is quite low, so that doesn't work as well you would think... You can face the subs either way, but having them fire into the box, your phase is 180* out of phase. Where as having the subs fire out of the box, they are 0* in phase. Basically they are opposite. They are actually reverse polarity, not out of phase. The two are different, and the concept is widely misunderstood. Simply reversing the polarity of the driver leads will take care of this. Quote Link to comment Share on other sites More sharing options...
Puggsley456 Posted December 22, 2006 Report Share Posted December 22, 2006 From my expierience the only benifit to inverting subs is for the slight increase in box volume because of the driver being mounted inverted. Personally I dont like this....I would much rather see the cone move than the motor/spider assembly......unless it has a crazy amount of travel...then I reserve the right to change my mind..lol Ported is the way to go......hands down! Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted December 22, 2006 Report Share Posted December 22, 2006 fosgate= port it. Quote Link to comment Share on other sites More sharing options...
CSI_MuNkY Posted December 22, 2006 Author Report Share Posted December 22, 2006 ok, so ported is suggested, and I know that different lengths of tubes give you a different frequency... how do you knwo what frequency is right for your subs/music? If it makes any difference, I'm a metal head, example, I currently have Tool blasting in my car... Jamie Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted December 22, 2006 Report Share Posted December 22, 2006 If you listen to rock, and absolutly no rap, get a sealed box. Ported just doesnt have the low end that sealed does. BTW, for a DD sub box, about a 30Hz tune is a great for a ported box. Quote Link to comment Share on other sites More sharing options...
Puggsley456 Posted December 22, 2006 Report Share Posted December 22, 2006 If you listen to rock, and absolutly no rap, get a sealed box. Ported just doesnt have the low end that sealed does. BTW, for a DD sub box, about a 30Hz tune is a great for a ported box. I would disagree with that. Any driver that is of decent quality will preform admirably in a 28-30hz box under all forms of music assuming it is of the propper volume. 35hz + is where things get dicey. Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted December 22, 2006 Report Share Posted December 22, 2006 rock sounds so much better on my system now. the only sounds that dont come in crystal clear is the big kick drum. which will not be reproduced in a ported box because they only magnify higher tones and an 18" sub is the only speaker that can accurately reproduce that sound. I know because I had an 18 in a sealed enclosure and listening to Pantera and double kick drum was devastating. With a ported speaker any size its going to magnify bass guitar and smaller drums normally reproduced by a crossed over and sealed midrange. Do you really want a 15" midbass????? am I really way off here?I dont know... .... sorry I know why. spl perposes, way cool. In fact I have been meaning to ask you Puggsley456, since you are one of the guys here that can calculate stuff like this, can you give an educated guess as to the port size and length for a 5.25" woofer . I would like to build some ports to tune my pods. I have no experience with this but I know it would work. the box will be around 2 maybe 2.5 liters if i'm lucky. I can give you a more accurate measurement probably tomorrow. It would be greatly appreciated. I really would love to have the option to give my system the edge if I decide to get more serious and meter it. Then I can keep my super lows dedicated to the dub 7. Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted December 23, 2006 Report Share Posted December 23, 2006 If you listen to rock, and absolutly no rap, get a sealed box. Ported just doesnt have the low end that sealed does. BTW, for a DD sub box, about a 30Hz tune is a great for a ported box. I would disagree with that. Any driver that is of decent quality will preform admirably in a 28-30hz box under all forms of music assuming it is of the propper volume. 35hz + is where things get dicey. well around 10Hz above the tuning is where ported shines, but has far as hitting hard and such, I just thing sealed does a better job. Maybe because its tighter and whatnot so it may seem like it. But my subs in my ported, I have no complaints about, but then again like you said it is considering the subs are in the req'd box and that they are actually quality subs. But not many people are going to go buy $200+ subs and build their own box to those specs. *most people just buy subs and a box without going into that detail. I think this is kinda where we got mixed up on that topic. Quote Link to comment Share on other sites More sharing options...
gtphill Posted December 23, 2006 Report Share Posted December 23, 2006 ok, so ported is suggested, and I know that different lengths of tubes give you a different frequency... how do you knwo what frequency is right for your subs/music? If it makes any difference, I'm a metal head, example, I currently have Tool blasting in my car... Jamie Hey again Jamie, There is a lot of voodoo out there about the different types of boxes, and it gets even more complicated for cars, because the car itself dramatically effects the sound. In the 1970s an australian electrical engineer named A.N. Theile used some modeling from electrical engineering to successfully predict the response of sealed and ported boxes, so that need not be a limiting factor. Ported boxes do have the advantage of increased output above their tuning frequency (i will spare you the gory details of why). They have a big disadvantage that the air in the port moves opposite the cone below the tuning frequency, effectively unloading the driver! That is why all professional audio ported boxes use something called a high pass filter to "roll off" the frequencies below the tuning frequency. Sealed boxes, on the other hand, rely on the very linear air "spring" in the box to help control the movement of the speaker at all frequencies. Sealed boxes have less output, but typically have a smoother response in cars. There is a peculiarity in acoustics of small spaces that makes the rolloff of a sealed box mate very nicely with a small room to give even response. I personally like sealed boxes in cars. There are plenty of super beefy drivers if you MUST have more output. The final trick here for making the subwoofers exciting for your car is balancing them to the rest of the system. Typically you want the low lows <80hz to be raised in volume relative to the rest of the audio spectrum. If you are not careful about how you do this, the octave above (80-160hz) ends up being unbalanced. This makes things like bass guitar, low electric chords, floor toms, synths, etc. too "wooly" or "bloated" at car that is smooth in this range, but with more oomph below will sound very powerful and smooth. If you have ever been to a big live sound show where everything is smooth and not muddy, but the kick just nails you in the chest like crazy, there is probably someone like me who has tuned the system in a good way, so that the very low content is strong and powerful, and the upper bass content is not overhyped and muddy. hope that helps! Quote Link to comment Share on other sites More sharing options...
Puggsley456 Posted December 23, 2006 Report Share Posted December 23, 2006 Garrett...... Sure I'll help where I can. Do you have any of the T/S specs of the drivers and volumes of the pods? Send me a PM and I'll give it a go. Quote Link to comment Share on other sites More sharing options...
gtphill Posted December 23, 2006 Report Share Posted December 23, 2006 Garrett...... Sure I'll help where I can. Do you have any of the T/S specs of the drivers and volumes of the pods? Send me a PM and I'll give it a go. I found the T/S parameters on the RF website. The qm is moderate, but the qe is high, which does not make this driver suitable for use in a ported box. They should give good extension in a sealed box. The PDF is attached [attachment deleted by admin] Removed to free up storage space. Quote Link to comment Share on other sites More sharing options...
slick Posted December 23, 2006 Report Share Posted December 23, 2006 I always have better luck with the Rockford's in sealed rather than ported boxes at work whenever I'm doing an install. Quote Link to comment Share on other sites More sharing options...
Puggsley456 Posted December 23, 2006 Report Share Posted December 23, 2006 Garrett...... Sure I'll help where I can. Do you have any of the T/S specs of the drivers and volumes of the pods? Send me a PM and I'll give it a go. I found the T/S parameters on the RF website. The qm is moderate, but the qe is high, which does not make this driver suitable for use in a ported box. They should give good extension in a sealed box. The PDF is attached That was in relation to Garrett's 5.25" pods. Quote Link to comment Share on other sites More sharing options...
gtphill Posted December 23, 2006 Report Share Posted December 23, 2006 ok, so ported is suggested, and I know that different lengths of tubes give you a different frequency... how do you knwo what frequency is right for your subs/music? If it makes any difference, I'm a metal head, example, I currently have Tool blasting in my car... Jamie Hey Jamie, I ran the Punch P2s you have through LSPCad and check the recommended boxes from RF. Their 19L sealed box, stuffed with about a pound of polyfill will be about right for each driver. Sometimes the factory suggested box sizes are waayyy off, but this one looks real solid. That is a small box (about 1.4 ft^3 built), and should give nice clean low end all the way down to 20hz in a typical car. The box FS also falls right at point where kick drum needs the most impact, so the drivers will be well damped for the type of music you like. You won't be winning the most annoying car on the block award, but something tells me that is not your intent. Quote Link to comment Share on other sites More sharing options...
CSI_MuNkY Posted December 24, 2006 Author Report Share Posted December 24, 2006 LoL definately not my intent to be annoying and stand out like a sore thumb, I'm shooting more for quality than anything. So your saying 1.4 cubic feet per sub? filled with poly fill? is there any sort of fills that are better than another? And the 1.4 is the box volume empty right? or do I take the size of the driver into account? I just finished up a report on acoustics within buildings, I have a feeling that RockWool Batt would be something to avoid (high STC ratings) Jamie Quote Link to comment Share on other sites More sharing options...
gtphill Posted December 24, 2006 Report Share Posted December 24, 2006 LoL definately not my intent to be annoying and stand out like a sore thumb, I'm shooting more for quality than anything. So your saying 1.4 cubic feet per sub? filled with poly fill? is there any sort of fills that are better than another? And the 1.4 is the box volume empty right? or do I take the size of the driver into account? I just finished up a report on acoustics within buildings, I have a feeling that RockWool Batt would be something to avoid (high STC ratings) Jamie No, I am saying .7 ft^3/sub, 1.4 total, and that is built out volume, accounting for wood, but not accounting for the driver volume, as I don't know what that is. The wool is to modify the compliance of the air in the enclosure, effectively making it larger. Polyfill works well, and is cheap. It also won't work its way in between the voice coil and magnet structure. Fiberglass is a no-no here, as tiny bits can work their way into the driver. As for STC, higher numbers are better, a good wall STC would be above 50. STC, however, does not measure low frequency adsorption, only mids and highs, and therefore is not a good measure of the low frequency absorbing behavior of something. I would recommend looking at the white papers on rpg's website http://www.rpginc.com if you want to learn more on this. "The master handbook of acoustics, by Alton Everest, is also a good quick reference. I have a copy of the fourth edition, not sure which one they are on now. Quote Link to comment Share on other sites More sharing options...
CSI_MuNkY Posted December 24, 2006 Author Report Share Posted December 24, 2006 No, I am saying .7 ft^3/sub, 1.4 total, and that is built out volume, accounting for wood, but not accounting for the driver volume, as I don't know what that is. So if I had a way to figure out the volume of the sub driver and all that I could add that to the volume of the box? if so thats not a big deal for me to do with CAD... The reason I brought up the wool, was wondering how it would do inside the enclosure, its not like your glass fiber, rock wool is actually made up of molten rock. So what IS poly fill then? I was assuming it was just normal pink insulation... Sorry for all the noob questions! Jamie Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted December 25, 2006 Report Share Posted December 25, 2006 you buy it in the walmart fabric section. or any fabric store. Quote Link to comment Share on other sites More sharing options...
Psych0matt Posted December 30, 2006 Report Share Posted December 30, 2006 you buy it in the walmart fabric section. or any fabric store. basically just pillow stuffing Quote Link to comment Share on other sites More sharing options...
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