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Blazer Sub

Discussion in 'Audio' started by MrArmyAnt, Apr 10, 2007.

  1. MrArmyAnt

    MrArmyAnt 1/2 ton status

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    Thinking about either a 12 type r in center console. or 10 or 12 type r on the side. just one though. On the side it doesn't seem like it would feel to even if the sub were out of phase, and with the top constantly coming on and off the phase would keep changing. Would a 12 even fit in the wheel well area before mdf would hit the back seat? I may have to dray pictures. I also thought about running two subs in the rear, like 10s, dont want to buy the extra amp now though, and don't want to subs front firing right into each other.
     
  2. chevyin

    chevyin 1/2 ton status

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    There's alot going on in this post.

    First off, you seem determined to run a Type R (or two). Certainly not a bad choice for its price range (actually very good choice for its price range) assuming you have reasonable expectations for the driver.

    Mark Potts, a national SPL competitor and member of a few boards I also belong to, has done extensive testing with the Type R (what he competes with, and won last year with new record in his class). His conclusion was it was a stunning performer for SPL, especially considering its price. But, he also found its performance was lackluster in sealed boxes. Basically, for R's you want a big ported box, probably tuned fairly high. Output will be very good, but sound quality will not.

    If you want to run a sealed enclosure, especially a small sealed enclosure, and/or you are more interested in SQ than sheer output, you may want to consider a different sub. Stepping up to the Type X would work better, if you want to stay with Alpine.

    Next, phase. Im not sure you are using the term phase correctly. Phase, in the simnplest terms, is this: a speaker receives power and starts moving. But, does the cone start by moving in, or out? This is the most basic function/description for phase. There are two types of phase in audio, relative phase, and absolute phase. Absolute phase has to do with which direction the cone moves first, positive terminal, cone starts by moving out, a positive pressure wave is created to recreate the same positive wave from the original recording.

    [FONT=verdana, arial, helvetica]Absolute Phase[/FONT] A positive pressure to a microphone diaphragm will (in most mics) produce a positive voltage at its output. If the correct polarity (see WFTD archive polarity) of the signal is maintained throughout the signal path this should ultimately produce a positive voltage at the speaker terminal, which will (on most speakers) cause the speaker to move forward creating a positive pressure wave in the listening position. This is known as absolute phase (see also WFTD archive phase): The original polarity of the source sound is thus reproduced in phase by the loudspeaker for listening. http://www.sweetwater.com/expert-center/glossary/t--AbsolutePhaseRelative phase is simpler to describe. It simply means, in a stereo system, are all speakers in phase relative to each other. In other words, do all your speakers in your stereo start by moving the same direction. If they do, they are in phase relative to each other. Relative phase between speakers in your system can be changed by simply reversing the speaker wires (pos to neg and neg to pos). Doing this reverses which direction the cone starts moving, and from that moment on that speaker will be 180 degrees out of phase with every other speaker in the system.

    Ideally, all speakers in your system are in phase with each other. But this is not an ideal world, sometimes better sound quality is actually acheived by purposefully putting one or more speakers out of phase with the rest of the system. Dedicated midbass speakers in doors are a notorious example of a setup that usually requires a phase adjustment. Also, when installing a new sub system, Id recommend trying it with the subs in, and out of phase with the rest of the system, leaving it at which ever sounds best (many times out of phase sounds better). The reason for these needed adjustments is because the shape of a vehicle's interior leads to alot of sound reflections, causing wave interaction (cancellation and reinforcement) and shifting speaker phase is sometimes a simple way to combat a problem in this area. Usually though, its too blunt a tool to use effectively for smaller anomolies, which is where EQ's etc come into play, but thats another story for another day.

    So, with the basics of phase covered, lets address your questions/concerns about it. You say you are concerned about the phase changing as the top is removed/replaced. Removing the top wont really affect speaker phase. It may/will affect wave interaction within the passenger compartment though of course, as its been drastically altered. Likely what will happen here rather than phase issues is, a loss of low-end output. Car audio enclosures are generally designed to include the boost in output a vehicle's small passenger compartment gives, usually in the 40-60hz region. When a top is removed, this changes, drastically, and the delicate balance of tuning of your box versus interaction/boost from the interior changes, and over-all performance suffers.

    For a convertible situation, I usually recommend a down-firing box. This seems to help 'contain' the bass inside the vehicle rather than escaping out of the open roof immediately. It also helps tranfer more of the vibrations to the floor/chasis, which is a good thing. The lowest octaves of bass our subs play are generally inaudible, but they can definitely be felt/perceived. The more efficiently your sub system transfer these low freq vibrations to your chasis/vehicle, the more you feel them and the more perceived low-end output your system will have. Down-firing... something to consider, eventhing I know it doesn't fit your stealth fit in existing spaces idea.

    You also mentioned phased when speaking about mounting the sub off to one side. Subbass is omnidirectional, our ears are not able to perceive where its source is located. This is why you can place the subs behind you and yet they (should) blend in with your front speakers just fine. So, having the sub in the center rear, or off to one side or the other, doesn't really affect anything audibly.

    Lastly, subs firing right into each other. Without getting into too much detail here, I will generally say that firing subs towards each other is most times okay. Will it cause some anomolies? Yes. But unless its an extreme situation (like mounted 2" apart, firing at each other perfectly), its not likely to cause any real harm. No, if you were building a national sound quality competition car, I wouldn't recommend it, Id say keep the subs on the same plane. But, its a convertible 4x4 that you probably just want some 'bump' in, mounting subs on each side of the bed firing towards the center (and each other) would be fine.

    Hope I helped.
     
  3. MrArmyAnt

    MrArmyAnt 1/2 ton status

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    I have enough room for a large box, and by phase I mean how long it takes for one not to bounce of an object to make one full wavelength, my car audio knowledge stems from home theater, in which having a variable phase means you can adjust the phase of say a sub so that the wavelengths are complete by the time they hit the listening position and blending them into phase with the main speakers so the bass is there but without a definite location (you say in a car you shouldn't be able to percieve where the base is coming from, which is true in cars, but in HT when it isn't set up correctly (most of the time) you can pinpoint it)

    I was debating between infinity kappa perfects (125 for me) and type r's (105 for me). I have an alpine 400 watt rms amp. Had to wait for the employee special order to go through for the infinity, and I'm impatient. Also the type r seems to be a little more roubust for offroading. And it's not white. Acording to alpine, the best size including mdf volume at 3/4" is .82cu, I could do more than that. I also have some scanspeak aero vents I think I might install. I did this in another sub box ones when there wasn't enough volume for very low notes, and it helped a lot.

    The downfire thing would work if I replaced the console. That was the idea I was debating. It also needs to be heard outside the vehicle, for our outdoor party things. Of course with doors off and top off, that shouldn't be a problem.

    Thanks for the help. Looks like I'll be doing a center console. I thought about trying to do a ported box there, it requires a lot of math though as it isn't just a rectangular box, and also If water or crap gets in that port my speaker is screwed. Nice thing about sealed is that shouldn't happen. Also, some rap may be played, trance being played more, and country and rock being played the most. Seems sealed boxes perform well there. Does anybody make a passive radiator for car audio?

    You you don't know what I am talking about, look at definitive technology's HT sub the supercube reference. Does a great job at many things.

    Thanks again!
     
  4. chevyin

    chevyin 1/2 ton status

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    Yes there are passive radiators made for car audio. Im abit short on time now, I'll dig up 2 or 3 options for you later.

    Variable phase is a nice feature. Unfortunately its extremely rare in car audio pieces. What is much more common, and what I think would actually work better in this application, is time alignment. In case you aren't familiar with it, its simply a delay feature you can apply to the signal that delays output from speakers, so you can adjust the timing in order to account for the unequal pathlengths in the vehicle. Most people dont go so far as to do time alignment with subs, but its certainly done in high-end SQ vehicles.

    If you are serious about wanting to really fine tune your system, you could look into a digital processor like Alpine's pxa-h701. Its what I own, cant say enough about it. 1/3 octave EQ, 5-band parametric EQ, time alignment, fully selectable xovers including fully adjustable xo point and slope, etc etc... at each output (can adjust all these for each individual speaker). Its an audiophile's dream come true for car audio flexibility. Unfortunately, they aren't cheap ($500-$700), you may not want to spend that kind of cash for a 4x4 car audio system. You could also look into some of the better head units these days, they have many of the same functions (but to lesser degrees) including time alignment.

    Many people chose to build a center console enclosure, very popular these days. Dont expect tons of output from it, as space is simply too limited to build much of a system that will move alot of air, but you should be able to have a competent sub stage using it. Im confused though, are you planning a sealed box, or ported? Or PR I guess. I can try to dig up some box recommendations (from Mark Potts recommendations) if I know what you are trying to do.

    Keep us posted. :)
     
  5. MrArmyAnt

    MrArmyAnt 1/2 ton status

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    Ah, didn't see your reply. I Have the type r now (keep debating on a marine infinity). Got it because It's somewhat lour and rigid, being that ribbed surround and kevlar. I was wanting to go sealed and coat the inside and outside of the mdf with resin, to keep it from rostting and the sinsitve areas of the sub concealed. I have a 77, so you step up into the back seat anyway, so I can build up a tad. I can still do the Idea I had for a box in the bed wall, but space is going to be tvery tight directly behind the sub, and the box would be L shaped, and I know I don't posess the knowldge to figure out standing waves and that jibber jabber.

    Damn I don't know if my components should be marine or what. I'm thinking about doing my own headliner, like the one lmc has, but better. Then maybe a console with two speakers in it (cant put it on the doors since I will be taking the doors off) along with maybe my cb in the custom center console, with amps in the back for it all (a wiring nightmare for a car with no carpet)

    Or just two speakers in the console, none in the head liner (but I liked the idea of the headunit up there, black, behind a black waterproof cover, hiding it from damn thiefs) and some coxials in the back.

    So, we have tome to the options

    marine or normal speakers

    sub in back in L, maybe ported if design allows, with speakers next to end of L or next to rear seat behind driver/passenger, with a similar box in bed wall in shape of L with amps

    sub in console, sealed, downfiring

    speakers in headliner with head unit

    speakers in console with head unit

    and cb in there somewhere

    Maximize sound for top of - minimize rattling

    I'm thinking of putting expanding foam in the back between the inside of the inner bedwall and outter part of the boddy, not only would this get that resonance down some since there large flat pieces of metal, it would also help keep it from bending from trails (when hit hard that crap doesnt like to flex)


    thanks for the help!

    Also, I cant get spray on bed liner to stick to the doors. Would resin stick to them? Then I could sand them then bedline it, might work better, or would it stick to bondo, or do I just need new doors?
     
  6. chevyin

    chevyin 1/2 ton status

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    Standing waves are a non-issue inside a subwoofer enclosure. For the frequencies being played, the wavelengths are simply too long for that to be a concern. Enclosure shape can be *just about* anything you want, with little or no audible effect. For a sealed application, its the internal volume that dictates alignment/response.

    Type R's are notorious for excelling in ported enclosures, and being.... lackluster... in sealed setups. You may want to consider a small ported box, especially since it would be a 1-sub setup (improved output).

    As for bedliner not sticking to your doors... it should. If it doesn't you must have some sort of contaminate that needs to be removed. Degrease it, then wipe it down with isopropyl alcohol (no residue), that should remove the problem with your doors.

    The rest of your questions... Im not sure what exactly you want... looks more like thinking out loud. :) I can say marine grade speakers will improve the lifespan of the component (probably), but generally at a loss of fidelity. You dont find national sound quality competitors using 'marine grade' speakers for example, but they certainly fill the bill for most people's listening needs.

    Sorry, I see I never found you a list of passive radiators, I forgot. If you still need info on them, let me know. :)
     
  7. MrArmyAnt

    MrArmyAnt 1/2 ton status

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    If you think they could help in this application (passive radiators) by al means look. You don't happen to have sub plans for a ported box that is an l shap do you? :)
     
  8. chevyin

    chevyin 1/2 ton status

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    Ported boxes are pretty application specific. Im sure I can help you come up with a design though. :)

    I'll look into the passives and try and post some up tomorrow along with some thoughts on them.

    Cheers.
     
  9. MrArmyAnt

    MrArmyAnt 1/2 ton status

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    Finals go on from now till tomorrow evening, then I'm doing some runs of my crap from norman to okc. at some point I'll put the sub in and see how deep the box is and what the shape of the L would be.
     
  10. chevyin

    chevyin 1/2 ton status

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    http://tcsounds.com/tcvmp.htm - TC Sounds long excursion radiator

    http://www.crutchfield.com/S-QedDcikxmuX/cgi-bin/ProdView.asp?g=520&I=065GTR12 - Boston PR

    That's just a couple after doing a quick search. Many brands make PR's these days, although honestly you rarely see them in car audio. *shrug* Here's a good link explaining the concepts behind using a PR: http://www.diysubwoofers.org/prd/

    Basically a passive radiator is a speaker with no motor assembly. Its mounted into a sealed box with a powered driver. A the powered driver changes air pressure inside the enclosure as it moves, this forces the PR to also move, giving it its own output. Output characterisitics are similar to running a ported enclosure, and the PR can be 'tuned' just like you can tune a port to a specific freq.

    Advantages PR setups have over ported systems would include no possible port noise (due to no port) and the system will ot 'unload' below tuning like a ported system will. Disadvantages include price, size (generally a PR has a bigger footprint than a port on the box) and general misinformation about PR's, how they work and how they are adjusted. Ive never built a PR setup, but Id like to one of these days. I owned a PR setup with home speakers once, seemed to work well.

    For your application, sounds like space will be at a premium, Id probably not go with a PR.

    Back to some of your other questions... marine grade speakers. Ive been thinking about this. Basically most marine grade speakers Ive seen have been made with cone materials and thicknesses not designed for optimum sound reproduction, but more designed to withstand harsh environments while still maintaining some level of performance. My experience with marine speakers is limited however, take that with a grain of salt.

    I will say this however, consider the abuse your speakers will realisitcally take. Do you submerge your truck? lol If so, I doubt even marine grade speakers will hold up, water is not meant to get into the motor/suspension/etc. They are more made to resistance rain/spray/etc. If you do submerge your truck, mount the speakers up high. ;) But more likely, you are just concerned about being able to hose out the truck, have wet dogs in it or something along those lines. In that case, it'll sort of be a judgement call on your part... how careful do you want to have to be with your truck to avoid damaging speakers. Its a priority thing, you need to decide for your self on that one.

    Downfiring center console subwoofer will yield the worst defense against flood waters. The speaer will be at the bottom of the box, firing at the floor, exposed. Up-firing would be the best against flooding waters, but the worst against possible rain getting in (with the top off). Side or front/rear firing in the console would probably be the most protected. Downfiring would yield the best acoustical properties though, probably. Again, a judgement call.

    When you say placing speakers in the front console, do you mean besides a sub? Like the front speakers? Keep in mind, if you mount both your front speakers in your center console, your left-right stereo seperation will go out the window. When sitting in the drivers seat, both speakers will be to your right, when one should be to your left. Passenger... same problem only in reverse, of course. It would yield poor audio results, but if its a bigger priority to place them there than to acheive the best sound, that is a possibility. I honestly usually recommend against it though, for the reason of screwing up stereo imaging. Another judgement call.

    You mentioned early on that you were concerned placing the sub to one side would make it sound uneven. No concern there. The low frequencies a subwoofer produces are too low for the human ear to distinguish the sound source. The sound is 'omnidirectional'. Therefore, placing the sub just about anywhere that still allows the sound waves free travel to your ears should not hurt anything. Now that's not to say moving the sub around wont change its sound characterisitc, it will.

    As you alluded to, sound wave interferance (cancellation AND reinforcement) still plays a role, even with omnidirectional sound waves. Just because the freqs are too low for our ears to distinguish source location does not mean the sound waves cannot/will not have audible wave interferance issues... I mention that distinction here only because many people confuse the two concepts. So in one way no, moving the sub around wont affect it sounding uneven, because your ears wont be able to tell if its to your left, or right (if done correctly). But its also true to say moving the speaker/enclosure around will cause wave interferance issues that will affect the frequency response of the system. Exactly how would only be a guess on my part.

    For example, up-firing tends to yield the flattest response do to more direct sound waves hitting your ears before bouncing off another object and causing sound wave anomolies. But, rear-firing against a tailgate or loading board tends to give the peakiest freq response (worst for 'accuracy', but better for getting loud).

    To minimize rattling, there are various techniques/materials used to deaden a vehicle. We can get into that step by step later, if you want to go that far. Just let me know.

    Expanding foam can be a blessing, or a curse. First, the warnings. Using expanding foam improperly can lead to severe body damage. Also, using the wrong type, or applying it improperly can lead to rust.

    Okay, the first warning, body damage. Expanding foam... well... expands. ;) When filling a large cavity with expanding foam, do it in stages, putting relatively small amounts and giving proper time to cure, then add more. Repeat until the cavity is full. Its easy to just want to stuff the can in a hole and start spraying till the can is empty or stuff starts oozing out everywhere... dont do it. Putting too much foam in at once can leave a pocket in the middle of uncured and unexpanded foam, that on a hot day, may decide to expand. If you;ve already buttoned up that cavity, the pressure could pop a body panel. Next, always leave a place for the foam to escape as its curing. Dont fill a cavity part full, then screw a cover plate bock on (for example). Ive heard of people doing this, miscalculating the expansion of the foam, and... you guessed it, popping a body panel.

    Second warning, rust. Use the proper type of expanding foam: closed cell. There are basically two types of foam, open cell, and closed cell. The difference simply being closed cell foam means each air cell has a complete wall around it. Open cell foams have openings between each cell (think of a sponge). This affects two major things, water absorption and sound absorption/deflection. Closed cell foam, because each cell has a complete wall, will not absorb water. Open cell foam absorbs it, and holds it (again, think of a sponge). Sound waves also find it easier to travel through open cell foam, as it does not have complete cell walls the waves must pass through. Also for preventing rust, when filling a cavity full of foam, be sure to keep any drain holes free to useable (such as the bottoms of doors). CLOSED cell foam: superior for sound deadening AND water resistance. Do not use open cell foams, they do more damage than good.

    Keep those warnings in mind, and yes expanding foam can be one of your best friends. I love using it, it gives a vehicle a much more solid feel, helps alot with road noise, and added weight to the vehicle is minimalized.

    I think that covers everything so far. Let me know if you have any more thoughts or questions to share.

    Cheers.
     
  11. MrArmyAnt

    MrArmyAnt 1/2 ton status

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    My Supercube is PR, I like its sound. I was only going to do the speakers in the console if I had the sub in the back, and only have them on when I was out of the truck. I want to find a DIY moon roof (seen them before) and make a custom headliner for it and put speakers up there., then some in the back. ( guess that's what I've decided) I know about closed and open cell, figured that out the hardway once or twice. Also learned not to use liquid nails in a sub box ( i fell fate to a small explosion)

    so looks like we will try to do ported in the rear on the sub (if you think that migh have more volume (sound wise not space take up wise) over a sealed down firing sub. I'm using my alpine amp on it, I believe its 300watts rms, hopefully that's enough ( i still have to gank it off my directed audio sub in my truck)
     
  12. chevyin

    chevyin 1/2 ton status

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    Depending on the space/shape you want for the box, maybe it could be side firing (toward center of truck) with port downfiring. That would still help 'contain' alot of the sound inside the vehicle with the top off.
     

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