subs facing?, does it matter? Options

[lake1069]

i have 2 12" 700watt subs in my hatch, i've been messing with the levels to get it to sound just like i like them, but i'm wondering if it makes any differece which way the subs face, like toward the driver or opposite?

[Cutrara]

You should have them facing the back glass, so it reflects off it.

[Abraxis64]

people say that it will be louder if you face it towards the rear for several reasons.

the main argument is the "compound loading" effect. essentially, this means that the soundwave will reflect off the back panel, bounce back and add constructive interference with a new, original wave emanating from the speaker--this effect, the theory goes, makes the sub sound louder. what frequency the gain is experienced at depends on how far away from the rear you place the sub. people often make "loading panels" and attatch them to the front of their sealed enclosures to replicate this effect.

basically, it's like putting your home theater subwoofer in the corner (aka 'corner loading') so that it gives the driver more surfaces to have soundwaves bounce off of (hopefully in the direction of the listener) and sound louder.

in reality, however, the automotive environment is so imperfect that it's really a matter of application. to put it simply: it depends. try it out facign the front. then turn it around and see if you notice a difference. if so, go with whatever sounds better. if not, place it in whatever way it'll be most convenient.

peace

...and from the way that you describe your drivers "2 700watt subs", it probably won't make a huge difference, anyway. but, just out of curiosity, what are you running?

This post has been edited by Abraxis64: Sep 6, 2005 - 7:46 PM

[lake1069]

well i'm running a 800 watt kenwood amp with the 2 12" 700 watts. but if feels like the subs are really not being pushed, i'm really thinking of putting another amp in there to get full potential out of these subs. i would putt up pics but i can't get it to work

[Abraxis64]

lake,

i don't mean to sound like a jerk or anything but i have two suppositions about your gear.

firstly, i know for a fact that your "800 watt" kenwood amp is not putting out 800 watts. not because kenwood is a bad company, and not even because they're lying, but because that's the "max" rating--a rating of practically zero consequence. what you want to look for is the "rms" or "continuous" rating.

secondly, your "700 watt" subs cannot handle 700 watts of continuous power for the above reason. what brand/model number are your subs and amp?

are you concerned with having your subs sound louder? if they're in a sealed enclosure now, an option may be to throw them in a ported enclosure (this saves you some cash since you won't be buying a new amp or speakers) and at least you can try it out. if it doesnt work out then, big deal, you "wasted" about 15-20 dollars in materials. if it does, great, because you saved a couple of hundred.

i'd hate to see you spend more money on a bigger amp and realize that it's your subs or enclosure that's the culprit. likewise, it'd be pretty junk if you went out and got new subs only to figure out that your amp wasn't giving your old subs enough juice.

peace

[lake1069]

here it is, its a KAC-7201 amp with KFC-W3005 subs with rms at 350. here at the stats for the amp, if i'm not mistaken when i had it installed they told me they bridged it. so i guess its 460 watt rms but since i have 2 subs would it be 230 w. to each? in the pic i had to move stuff around to make room for food for the new orleans ppl.

» 150 watts RMS x 2 at 4 ohms
» 230 watts x 2 at 2 ohms
» 460 watts RMS x 1 bridged output at 4 ohms

[Abraxis64]

first off, cool that you're doing your part to help the katrina victims. now, on to the audio

for starters, i don't really know how your shop would have that amp wired. your subs are 4ohm subs and if they bridged your amp, they would've only had two options--wire your subs down to 2 ohms (which your amp isn't rated to handle in bridged mode) or wire them in 8ohms, which would give you half of that 460watt rating, so only 230 for BOTH of your subs, not each.

what i suspect they did is simply run the amp in stereo operation. can you tell by looking at it? there should be two sets of + and - terminals on your amp. are both the - and both the + terminals in use? or just one of each. if it's the former then it's in bridged mode. if it's the latter, it's in stereo mode. either way, you're either getting 115w to each (if it's bridged) or 150w to each (if it's in stereo).

tough call here, buddy. do you like how your setup souds and just want it to be louder? or do you simply want it to be loud and you're willing to sacrifice some of the musicality? if you're willing to sacrifice some musicality, you may want to consider a ported enclosure for those speakers, though i'm not certain that i remember what type of enclosure those drivers were designed for. also keep in mind that ported enclosures are substantially larger than sealed ones. you could just throw more power at it, but you wouldn't be able to do anything with your current amp. and, even then, it's no guarantee that you'll like how your speakers sound with the extra power.

i guess it all depends on what you want out of your system but, as it is right now, your hands are kind of tied with your equipment...i guess it's up to you

peace

[Silvan]

It shouldn't really matter what side they are facing. That part has to do with the human ear; the human ear isn't capable to detect where sounds below 80Hz (I believe) are coming from. Think of the subwoofer of the surround-set. You can virtually place it anywhere.

As for the part of subwoofers not doing there job; This all depents on the construction of the enclosure; is it designed to meet the specs of the sub? What about crossovers; maybe set to a too high frequency or a too high db-cut off ?

[afroman]

are your subs dual 4s or single 4s if they are dual 4s then they probably wired each to 8ohms then wired them together for a 4ohm bridged load.what size box do you have.if the sealed box is much over 1.25 cubes per sub its an sq box and you will lose output but gain in clearity. if you want it loud then do what everyone else says and go vented.just make sure to get specs from kenwood they will recommend a size for the box4 an port length.
-Aaron-

This post has been edited by afroman: Sep 8, 2005 - 11:19 AM

[afroman]

sorry double post

This post has been edited by afroman: Sep 8, 2005 - 11:18 AM

[Abraxis64]

It shouldn't really matter what side they are facing. That part has to do with the human ear; the human ear isn't capable to detect where sounds below 80Hz (I believe) are coming from. Think of the subwoofer of the surround-set. You can virtually place it anywhere.

while you are correct in your assertion that sounds below a certain frequency are omnidirectional (you can't tell which direction they're coming from), that doesn't mean that the sound waves don't exist--in fact these sound waves function like any other wave and they tend to bounce off of stuff. sometimes, when they bounce off stuff, their strength is amplified.

take your home theater example--sure, if you wanted you could stick your sub in the middle of the living room...but if you stick it against a wall, it appears to sound louder...stick it in a corner, and it's louder still. you won't be able to localize the sound (if your sub is playing nothing but sub-bass, anyway), but you will be able to discern a noticeable volume difference.


afroman, as far as his subs, i don't recall the w3005 ever being produced in a dual-coil configuration. it is possible, however, that they are single 8-ohm each? hopefully the shop told him
peace

[snadman]

subs are single coil 4 ohm drivers almost positive. Properly running these would be to run them in stereo, as bridging them makes no sense in this case as you are losing power.

Just for instance say these subs would be dual 4 ohm drivers. the proper way to run them would be to "bridge" each sub's voice coils to the other, which in turn makes them a quazi-2 ohm driver (1/Rt = 1/Ra + 1/Rb --> 1/4 + 1/4 = 1/2 --> total resistance 2 ohms) then you would run these in stereo or in series bridged to the amp, either way giving them 230W RMS a piece. When you run drivers in parallel the resistances add in the manner I showed above, 2 drivers of 4 ohm run in parallel makes the amp see a 2 ohm load. 3 drivers of 4 ohm in parallel lets the amp see 1.33 ohm load and so on. Running drivers in series you simply add the resistances of the drivers. I honestly, think Abraxis and I should make up some tutorials or information pages on wiring up subs so people can just look there first and post here if they have more extensive questions.

This post has been edited by snadman: Sep 7, 2005 - 10:06 PM

[lake1069]

i recall the guys at discount performance sayin the they were single 8-ohm each but don't quote me on that cause that guy that sold me these things looked like he visited lala land everytime i asked him a question, as fas as how they did the wiring i'm not sure i'll do some reasearch and try to figure it out. thanx guys

[DmVinny]

here it is, its a KAC-7201 amp with KFC-W3005 subs with rms at 350. here at the stats for the amp, if i'm not mistaken when i had it installed they told me they bridged it. so i guess its 460 watt rms but since i have 2 subs would it be 230 w. to each? in the pic i had to move stuff around to make room for food for the new orleans ppl.

»  150 watts RMS x 2 at 4 ohms
»  230 watts x 2 at 2 ohms
»  460 watts RMS x 1 bridged output at 4 ohms 

[right][snapback]331594[/snapback][/right]

HAHAHAHAHAHAHA!!!!!!!!!!!!!!!!!!!!!!!!!

GOT RICE?!?!?!

[Silvan]

It shouldn't really matter what side they are facing. That part has to do with the human ear; the human ear isn't capable to detect where sounds below 80Hz (I believe) are coming from. Think of the subwoofer of the surround-set. You can virtually place it anywhere.

while you are correct in your assertion that sounds below a certain frequency are omnidirectional (you can't tell which direction they're coming from), that doesn't mean that the sound waves don't exist--in fact these sound waves function like any other wave and they tend to bounce off of stuff. sometimes, when they bounce off stuff, their strength is amplified.

take your home theater example--sure, if you wanted you could stick your sub in the middle of the living room...but if you stick it against a wall, it appears to sound louder...stick it in a corner, and it's louder still. you won't be able to localize the sound (if your sub is playing nothing but sub-bass, anyway), but you will be able to discern a noticeable volume difference.

[right][snapback]331709[/snapback][/right]

All that you are saying is true, but then again also not entirely. (dont feel offended )
Subwoofers are really a tricky thing. Because subs play in the lowest regions of soundfrequency, what you really measure is the response of the environment it is in.
The reason that you have for example 90db@20Hz. has more to do with the fact that you find yourself in a spot where you have maximum bassreponse at that specific frequency. (anti-node)

As an experiment try this: place your sub in a room and let it play a constant tone of 40Hz. Walk around with a db-meter and mark all the spots where you have good reponse, walls for example (anti-nodes). Mark also places where you have nearly zero response (nodes). Now try the same with a 50Hz tone. You will notice that all the spots you've marked before are all mixed up. This is because all tones travel with exact the same speed. But the wavelength is different which causes that a full low frequency sinus does not "fit" in the room. Also if letting sound reflect from a surface isn't a clean solution. The reflected sound travels delayed. If you make this visible with a spectrum analyzer you should see several sinus curves, crossing eachother. This will result in amplification at some points(spike, anti-node) but also at some points they will cancel eachother (node).
Also, the reflected sound will travel to your ear with delay, causing a rumbly and distorted bass.
This proves that placing a woofer doesn't work by the priciple that if it reflects its sound, there is more sound pressure level at every frequency, thus making it very difficult finding a sub that meets your needs for a specific room without tuning it.

If the woofers are suited for it you could go ported. While there are some benefits there, like 3-4 db more pressure, be carefull not to make design flaws, you could easily blow your subs.
A rule of thumb that can be used is; EBP produkt (Efficiency Bandwith Product):EBP = Fs / Qes
If EBP > 60, and QTS = 0,5 : Free air
If EBP = below 100 and QTS equals 0: Closed enclosure.
If EBP = between 50-100 and QTS equals 0: Ported.

[Abraxis64]

silvan,

very good points however, i believe i touched on this very briefly (perhaps too briefly) with my assertion that, depending on just how many inches away you place the woofer from the loading panel, you'll get different results. in any case, it is my standpoint that the average listener has a certain frequency range which they'd like to amplify and they would take this into account when planning/setting up their system. my home theater environment, for example, is not optimal, which means i do have deadspots (nodes, by your terminology) in a coupleof places within a certain frequency range. i simply adjusted it such that i had the freqs that i wanted in the places that i want. in an automobile, response will be totally screwed up since it is, essentially, one of the worst environments for hi-fidelity reproduction of sound

very few listeners will have as discerning an ear (nor will they have the testing equipment) as you do...and they'll probably keep listening in happy ignorance or something like it. i know i do

as far as the EBP, i like how you made sure to include qts in your "categorization" since ebp is, by itself, a flawed system--one that aims to compare BL and Mms but actaully only compares their product of mms and cms. nice work there

peace

oh, and lake--if you do in fact have two 8 ohm drivers wired in parallel for a 4ohm final bridged load...that's pretty much as good as you can get. only option here is switching equipment (sealed for ported; amp for another amp; subs for another sub; etc)

[Silvan]

Thanks for explaining yourself and the discussion: I see your points and it's true, car are the worst environment to create decent sound. You have good point saying people probably keep listening in happy ignorance or something like it. I cannot deny it; it counts for me as well.

This post has been edited by Silvan: Sep 9, 2005 - 2:04 AM

[Digndoug]

Ok, well i didnt want to post until i tested my subs. I have tested almost every position of subs in my rear hatch. This last design sounds the best. Its not done and prolly onwt be for a bit, but here are some pics.

[droptopGT]

nice

[Abraxis64]

...hope you have a plan to hide those, or else you just have a big "steal me" sign in your rear window...

i like the design, though. looks like you'll have some cancellation issues, but it does look pretty

peace