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Any Downsides of 18" Subwoofers (glass)

 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 1
Registered: Nov-04
Anybody with some experience would be great. I'm lookin into buyin 1 18" subwoofer to go in the back of my Toyota highlander. I've just heard couple people say the 18's are sloppy. Box size is not an issue. The Sub will be recieving 1000wrms. Also anybody familiar with
Planet Audio FU series subs. Thats the 18 i was lookin into. I've got experience with PA and have nothing bad to say about there subs.
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 3
Registered: Nov-04
I know Somebody can help me in here??????
 

Bronze Member
Username: Blownriv

OH USA

Post Number: 46
Registered: Nov-04
i've never run an 18", but i have nothing against them, although i think it's a bit of an overkill for car audio. but if you can fit one, and you like lots of loud, low bass, i'd go for it.

there's no real evidence that all 18"s are sloppy. some folks say they are "slow" or whatever, but that's just not the case. the only thing different about an 18" is that it can move a lot more air than smaller subs with less effort, and that's a good thing. you will get lower and more powerful bass with less power than you would need with a smaller sub.

i listened to a JL audio 18W6 once - very good sound quality and very low bass in a box that wasn't really that big.
 

Silver Member
Username: Slap_johnson

Arizona

Post Number: 101
Registered: Aug-04
its all in the install, an 18 can sound really clear if you take your time on planing your install, the key is to not rush, listen to different subs see what YOU like and see if you can make an enclosure to the specs of the sub
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 4
Registered: Nov-04
Aight I decided to give it a try. i'm gonna go with a PlanetAudio FU-18. I've had good experience with PA so far so why not give it another shot. It'll be my only woofer in my Highlander so box isnt' going to be a problem. I'll go ported of course. it'll get 1k wrms it can handle 1800wrms but i'll have to get a bigger amp in the future. Check out the site and let me know what u think about it. www.planetaudiousa.com look under subwoofers FU series
 

Help2
Unregistered guest
That thing looks like a stroker rip-off.
Isnt Planet Audio made by the same people
who make Boss?
: |
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5644
Registered: Dec-03
the problem with an 18" sub is you've got a lot of cone mass there. It's harder to get it moving, stop it, and make it go the other way.. quickly and accurately.
that's why an 18" sub isn't going to be as controlled or tight as smaller subs.
With that and power requirements as a downside, you do generally have a very low Fs for a large sub like that and you'll get a lot of resonating, low bass from the subs.
They're best suited to people who want overwhelming bass as opposed to tight, controlled, accurate bass for more detailed musical tastes.
If you're after accuracy and a well balanced system, you'd probably go with 8's or 10's
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5645
Registered: Dec-03
additionally, the spolliness you mentioned is generally from not using the proper LPF for such a large sub, which needs a steep Q, and very low LPF point. Crossing the sub too high causes a lot of cone resonance and distortion due to harmonics created by having so much surface area on those large cones. It's hard to keep them rigid at high excursion.
If you go with a high end sub though such as Eclipse's Ti series, or RE's triple X subs, the drawbacks to large subs are mostly minimal due to superior design.
I don't know that PA's sub will be as forgiving as a higher end sub with the rigidity of a titanium cone though.
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 5
Registered: Nov-04
hmmm. I definitly dont want nothing thats gonna sound like Garbage. I just like the idea of haveing something a little diffrent than everyone else kinda, and bein that this is my first SUV I want something that i'm gonna feel up front. What would yall recommend I have about $300-$400 to spend on a woofer and I have a 1000wrms amp gimme some ideas to get LOUD
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 6
Registered: Nov-04
Help2---Do a little research on some forums for PlanetAudio and you'll see some good things about them. The 2 12" M2 DVC's that I have look like a hell of alot better quilty than antyhing Boss that i've seen
 

Bronze Member
Username: Blownriv

OH USA

Post Number: 48
Registered: Nov-04
quote: "Eclipse's Ti series, or RE's triple X subs, the drawbacks to large subs are mostly minimal due to superior design."

i think you've pretty much nailed it. the reason 18"s get a bad rap is because a lot of them i think aren't built as well as many smaller subs. if you check, a lot of 18"s don't have good xmax specs. i suspect this is partly due to the fact that many have inadequate motor designs. if they had a more powerful motor, driving that heavy cone would be easier.

i don't quite buy the "heavy cone = slow speaker" theory entirely. if the cone is so hard to move, than why is an 18" sub so efficient? SPL/1W/1M can be 96dB+ on an 18". it doesn't take much power to get sound out of them because lots of air gets moved with very little stroke. the disadvantage of a high cone mass is offset by the advantage of having more cone area.

also, if a sub's cone isn't moving quickly enough, it won't sound sloppy, it just won't be able make the higher frequencies. as a rule, the higher the frequenciy a driver plays, the faster its cone must move. if it's too slow, you'll see decreased output in the higher bass frequencies, but it will play the lows just fine, and nothing will sound sloppy. if it does, it's because the driver is of bad design, or it's in the wrong size box, but it's not going to sound bad, slow, or sloppy soley because it's an 18".

if anything, an 18" will sound better at all bass frequencies because it has to use less xmax to get the same output level. the less stress you put on a cone, and the more you keep th coil in the gap, typically the lower your distortion will be.

i do agree that there are limitations as to how high an 18" will play. you'll probably need use an 8" sub or two to match the level of the 18"s lowbass output in the midbass area. if you don't make adequate midbass power to match the lowbass levels, the bass will sound sloppy and slow, but it's not the fault of the 18". it's bad system design resulting in a severely constricted midbass response. i think this is why 18"s often do not sound good - they are used incorrectly.
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 7
Registered: Nov-04
SO if I stick with what I got and add 2 8" Subs for midbass I should be ok, I wont get no extreme 8" subs probably something that will take about 75 watts a piece. Would it be ok if I ran them on the same amp as my Kappa comonents. I think my system is starting to come together finally. is there anything else i could add to my system to get better off so far I got a Sony cdx-M8805X deck (I know I know) Kappa 60.5cs 6.5" components, 1000wrms Amp for sub and will be lookin into a amp for components and for the 8"s I do wanna run the 8" and components off the same amp though. I dont wanna get into 3 amps.
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 8
Registered: Nov-04
2005 Toyota Highlander if anybody was wondering
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 9
Registered: Nov-04
Also is it possible to get a 4 channel amp run the 2 channels for components up front, then bridge the 3rd and 4th channel to the 2 8" to get them more power by running 2ohm load
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5652
Registered: Dec-03
"I don't quite buy the "heavy cone = slow speaker" theory entirely. if the cone is so hard to move, than why is an 18" sub so efficient? SPL/1W/1M can be 96dB+ on an 18". it doesn't take much power to get sound out of them because lots of air gets moved with very little stroke. the disadvantage of a high cone mass is offset by the advantage of having more cone area."

mass * velocity and the more mass you have, the mroe energy it takes to stop that momentum and reverse the direction. remember, objects at rest, prefer to stay that way.
efficiency is a totally different matter. the large sub will have a higher efficiency because it flat out moves more air with the large surface area, so the measure of dB @ 1W@1m is going to be a good number. The difference comes audibly in the detail. an 18" sub is never going to be as fast as an equal quality 10" sub.

"also, if a sub's cone isn't moving quickly enough, it won't sound sloppy, it just won't be able make the higher frequencies. as a rule, the higher the frequenciy a driver plays, the faster its cone must move. if it's too slow, you'll see decreased output in the higher bass frequencies"

actually what you'll see are issues like the loss of stiffness in the cone that causes harmonics, and.. makes the sub sound "sloppy." It's very hard to keep a rigid cone on a speaker. Especially as they get bigger. This is one of the downfalls of the solobarics too, actually.
As I noted already though, this can be compensated for to a great extent, by proper box design, and using a high Q, low XO point LPF. Most people tune an 18" way too high, and cross it over too high and too shallowly so it'l roll off to their tiny 5" midranges in the front doors.
if you use a large sub like this, give serious thought to midbass drivers in the 8" range to bridge that gap.

in general, you still have a lot more surface area, and cone mass to move with an 18" sub though, so that will make up for any gain you get from the shallower excursion needed. It would at least balance out in both overall performance, and power needs in the end. A lot of things are a matter of trade offs though and figuring out what you want, and what you're willing to sacrifice to get it.
If there was one perfect speaker, we'd either all own it, or all be figuring out ways to afford it.. haha
 

New member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 10
Registered: Nov-04
I'll definitly be adding 2 8" for midbass then Is it possible though like i stated earlier to run my components off 2 channels and then bridge the other 2 channels to run the 2 8"s to give them more power than my components. This will be a 4 channel amp of course
 

Bronze Member
Username: Blownriv

OH USA

Post Number: 49
Registered: Nov-04
quote: "mass * velocity and the more mass you have, the mroe energy it takes to stop that momentum and reverse the direction."

this is true, but the velocity of an object increases its energy more so than its mass does.

if you're familiar with the kenetic energy rule (K = 1/2•m•v^2), you know that doubling the mass of an object (such as a speaker cone) will double its energy. however, doubling its speed will quadruple its energy.

there is no doubt that the bigger cone of an 18" is ordinarily harder to control than the lighter cone of say a 10" because it weighs more. BUT, THIS IS ONLY TRUE IF BOTH CONES ARE MOVING AT THE SAME VELOCITY. once the little 10" starts throwing two or three times as far as the 18", the motion of the 10" cone gets much faster, and this means it has more velocity - and thus MUCH MORE energy.

it should be clear that a cone with more kinetic energy, and not one with more mass, will be the harder one to control. while the 10" motor is working hard to make its cone stop and reverse direction at the end of its 20mm stroke, the 18" is happy moving its larger, more efficient piston less than half that distance - and producing cleaner bass at the same or greater output level.

the point is, a "quicker" cone is harder to control than a heavy cone because the kinetic energy of an object is directly proportional to the square of its speed.

this is why a 40 gram projectile can pierce an engine block from a mile if it has enough velocity, while a slow-moving 40 pound object will simply bounce off. velocity, not mass, is the most effective way to build kinetic energy, and more kinetic energy in woofer cones = less control.

quote: "actually what you'll see are issues like the loss of stiffness in the cone that causes harmonics, and.. makes the sub sound "sloppy." It's very hard to keep a rigid cone on a speaker."

yes, but have you noticed that many smaller woofers are using beefed up high-mass cones (solobarics included) in an effort to make them more rigid? also notice how longer coils are used to gain xmax, and how multiple VC layers are employed to take the extra power needed to make everything move. what you end up with is a 10" piston that weighs nearly as much as the 18" version. what does that solve? am i supposed to believe that a heavy 10" cone that tries to move 3 inches peak-to-peak will sound "quicker" than a relatively light 18" cone that doesn't need to move as far?

i guess what i'm trying to say is that you can build up a small sub to resist flex under extreme excursion, or you can just use a larger sub that doesn't need to move as far to begin with. with an 18" you don't have the need for giant excursion, so you'll end up with less stress on the cone.

(anthony, i know this post probably isn't helpful to your situation. my apologies for the highjack.)
 

Bronze Member
Username: Giants25al

Lakeland, Fl U.S

Post Number: 12
Registered: Nov-04
Nah man go ahead i'm learning these things, I have pretty decent knowledge on speakers untill u get to the true physics of them So anything is helpful
 

Bronze Member
Username: Skrilluh

Post Number: 26
Registered: Nov-04
I could listen to this all day , feel like im in school again :-)
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5658
Registered: Dec-03
see now we're factoring in another variable of comparitive excursion though.
if both subs, an 18" and a 10" exhibit the same Xmax, then the velocity (distance traveled at teh same cycles per second) is equal.
when you start talking about a greater throw, yah velocity has to increase to maintain the same number of cycles per second. Same thing happens when ya turn the volume up.
frequency stays the same, but amplitude increases.
I guess we just need to define our parameters and environment more clearly, too haha

anyway this board is being goofy this morning, and I need to head to the dentist.
ttfn
 

Bronze Member
Username: Blownriv

OH USA

Post Number: 52
Registered: Nov-04
quote: "if both subs, an 18" and a 10" exhibit the same Xmax, then the velocity (distance traveled at teh same cycles per second) is equal."

sure, but to generate equal SPL at any given frequency, which needs to excur farther, the 10" or the 18"?

answer: the 10", because it has to make up for having less piston area. so the 10" cone will have more kinetic energy compared to the 18" at any given SPL level (especially at lower frequencies), making it harder for the motor to contol.

you can compare both subs at equal xmax if you like, but i don't see the point in doing so. remember that at equal xmax the 18" will always be generating considerably higher SPL than the 10" at any frequency, and at any excursion level. by comparing the two speakers in this way, the only thing you will prove is that the 18" is much louder for the power used.

point is, the 10" uses greater xmax than the 18" to accomplish the same amount of work. as a result, the 10" cone is harder to control. also, because of the etreme xmax, the 10" cone will exhibit less linear motion than the short stroke of the 18". and as you know, non-linear behavior = distortion.
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 5660
Registered: Dec-03
the point in doing so is real world application.
some companies (MTX for example) like to offer several sizes of sub, but they all exhibit the same Xmax.
the 9xxx line is like that.. so they tout how their ten beats a W7 in specs.. but they never compare a 9512 to a 12W7, and for good reason.
You had mentioned short throw 18" subs and high excursion 10" subs. I was merely pointing out that you're getting into completely different driver design principles when you do that, and this will unerringly change the parameters of the experiment by altering control factors.
It makes a one to one comparison difficult at best.
 

Bronze Member
Username: Blownriv

OH USA

Post Number: 53
Registered: Nov-04
quote: "...you're getting into completely different driver design principles..."

okay. so what? even if 10" and 18" subs operate on different principles, do they not both make bass? i guess i don't care how something works if the end result is the same, you know what i mean?

the point of this discussion was to compare the capabilities of the 18" with smaller subs. i feel the 18" can whip anything smaller, at least in a one-on-one comparison. now, you line up multiple 10"s against one 18" - now i think you've got a competition.

i have seen no evidence that leads me to believe an 18" cannot make accurate bass. plus, an 18" can easily get ridiculously loud with less power than a wall of 10"s would need. about the only thing i have doubts on is the high frequency range, but who crosses over their subs above 100 Hz, ?
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