I read that speaker power ratings are dependent on the type of box you are using (bandpass, ported, sealed)?

I am about to run a 12" Infinity Kappa perfect which according to the infinity website is rated at 350W RMS...however I have heard this is rated in a bandpass box and that you can run more power depending on what style of box u are using...

any truth in this?

 

Read this:
http://manuals.harman.com/INF/CAR/Bo...re%20Sheet.pdf

 

this is right up my alley, yes putting a sub in a bandpass in particular puts a lot more stress on the sub. mostly thermally. bandpass boxes limit the cone travel of the sub by a lot and as a result the coils will over heat.
this is exactly the reson when i designed the power mouse i had to build a sub that has high power capability. i used a 3" diameter voice coil to make the sub handle the heat.

also if your considering a bandpass ill be the first to tell you that unless you know exactly what your doing and have designed the box to work with that particular sub dont bother.
bandpass boxes are very very difficult to get right. they need a special sub and a computer modeled design to make them sound good.
if you have access to this information and know how to build one correctly the results are noithing short of spectacular!
my dual 8's hit as hard as a single 12 or pair of 10's we got 136.5db from 2 8's running 1/2 power.
i would go ported if i were you. they are a little easier to make sound good. but if you want some help building a bandpass box let me know i would be happy to help you dsign one.

 

Thanks. I already built a custom sealed box, mainly due to space concerns. I wanted to keep as much of my trunk as possible, so I built a box that looks like a false wall and backs up as far as possible to the seats.

I was just curious if I should run a more powerful amp (> 350W) since the box is sealed (and assuming that these ratings are conservative and based on a particular box type). I read that people run these at greater than 350W...around 500 or so... I just want to get as much as I can out of what I have.

 

bandpass boxes are very very difficult to get right. they need a special sub and a computer modeled design to make them sound good.

While it's not technically accurate that you "need" a computer-modeled design, it's a hell of a lot easier than a lot of trial and error.

It's also true that some speakers which are fine in some applications, sound terrible in a bandpass box. Unfortunately this has happened in the past with some designs that modeled just great on the software... this part is a bit trial and error anyway.

The analogy that I use on bandpass boxes most of the time is that they are a technique to make a speaker sound bigger than it is. (Don't take my word for it, look at Bose's patent on dual-bandpass commercial designs. That's why no one can sell the dual-BP design but Dr. Amar.)

If you use a bandpass design with a speaker that is smaller (8") it can sound like a 12". If you use it with a 12", the question can become, what's your point? You can make it way loud, but if your ports are too small relative to the amount of air that now has to fit through those ports, you will experience compression above a certain SPL - the bass won't get louder, but the higher-frequency port noise will.

Keep in mind that bandpass boxes play midbass for squat, you will always need a very low xover point (sometimes people think that with an 8", they can play it higher. Not so. Even though it is an 8", it doesn't SOUND like an 8".)

I have built BP enclosures for 8", 10", 12", and even 4 Sony 6.5" woofers! (R & D.) You can get some very interesting results. But with how small sealed-box speakers can be nowadays, BP have become less used, since you can get a 12" in a good sealed enclosure for less space than you can get an 8" in a good BP enclosure.

 

Ok, I read that before...but I'm still unclear on if the quoted power rating is different depending on what type of box is used. The white paper doesn't say anything about this, it just shows frequency response based on a specified power rating (unless I am completely missing something here). Also, I'm not worried about bandpass boxes cause I'm not using one...I'm using a sealed box. I just want to know if I could/should put more power to this sub?

 

actually if you have the right sub you can get the bass of a 10-12" with an 8" sub in a bandpass using the same airspace if you know what your doing.
you can also get a lot more bass with far less power in a BP enclosure.

for another example we did 150db at the dash using a pair of 10's in a BP that only took up 2.5 cubic feet. you would have a hard time finding a pair of 10's to play in a ported box that size and you would need a pair of at least 12-15 inch subs taking 2 x that airspace sealed to get the same SPL.
so i dont agree.
fact is if you design the right BP enclosure with the right subs you can in fact get more bass in less space than any sealed box.

it would more correct to say that you cannot fit a 12" sub in a BP enclosure that uses the same space as a 12 in a sealed box. but if you do it right a 8 or 10 will give similar SPL and if designed correctly will play a far wider frequency responce with far less distortion than a sealed will. also in the same space as that sealed 12 would need.

 

put it this way, when i first began building BP boxes using regular subs rated for say 280 watts RMS they would fry in a BP with 1/2 their rated power.
they may not fry right away but eventually it will take a toll on the subs either mechanically or thermally.

so as a rule if you plan to run a subb in a BP setup you need to know 2 things. 1 dont plan to run more than the manufacturers specs and for good measure run less.
also gain adjustment is crutial if you clip the amp you wont be able to hear it in a BP box. a BP box hides distortion. you would be stressing the sub very easily and not even know it. that is why most subs dont last in BP boxes very long.
small airspace, cant hear distortion and running too much power = fried sub.

 

er..huh?

I'm assuming you don't mean with the same speaker, (in most cases)....

 

actually it depends, yes you could get more from the same speaker but its not to say it would sound right.

it may turn out that the speaker is not well suited for a BP design. but take my sub for example. it is designed for the BP application. it turns out its a very good ported sub. not too good for sealed however. yet in a sealed application SPL wise it wouldnt be anywhere near the SPL of the BP design.

 

Based on the fact that they show the ported enclosure at 650W and the sealed at 350, I'd say that the maker rates sealed at 350. They say clearly elsewhere that max power handling is on reached with a ported box with a subsonic filter.

Somethng to understand about making drivers: These guys spec a voice coil. They spec a cone and a spider and a magnet - maybe they use off-the-shelf parts, maybe they make them from scratch. No matter what, they have their estimated power handling, and they can only verify that their model is correct by making lots of boxes and blowing up lots of woofers before selecting the power rating.

They probably don't do that. Their estimate is just that - an estimate. You'd like the maker to give you clear direction on this... but they probably don't know any more now than they did when they created the estimate.

The advantage of a ported box with power handling is that near the porting frequency the speaker actually doesn't travel very much. The speaker would not start to travel far until it was playing notes 1/2 octave below the porting frequency (with a 40 Hz port, 1 octave below is 20, and 1/2 octave below is 30 Hz.) If you have a "subsonic" filter to take out any notes here (you probably wouldn't hear them anyway), you would not have to worry about over-traveling the cone (see the graph). You would then only ahve to worry about over-powering the voice coil wire itself. Based on the fact that they provide such a higher power rating for ported, I'd say that the 350 W rating is based on excursion, NOT on voice coil thermal properties (melt point).

Until you actually hook up the speaker and listen to it, all the discussion is theoretical wanking. Hook it up and listen to it and see if you have a problem to solve... if everything's fine, off you go.

 

Ahh, I see now. I was kind of confused with 'group delay'....wasn't quite sure what that was. But now I see what you are saying about cone travel. The 350W rating is for the sealed bandpass box....for a sealed enclosure like i am using, they are running it at 500w...

I think you are right by saying that the power ratings they are estimating are based on excursion and not thermal properties. I have heard before that people are running these subs at 600w and up...so I guess the lesson learned here is that, yes box types can have an effect on power ratings.

Also, do you have any idea what group delay is?

 

where did you see the word Group delay? thats a concept not many people talk about.
but to answer your question it is simply the delay in milliseconds of the audio signal from the input signal.
its a little like phasing.
as long as your group delay is not too sudden to change you will be fine. BP boxes have an inherently worse group delay than sealed or ported designs. but as long as the amount of delay is relitivly consistant across the bandwidth it wont have many ill effects.

let me also make a comment about power ratings considering i have build some subs in the past.

my 10" sub normally would have got a rating of 450 watts RMS because that is how many watts is takes playing a 60 hz signal for 4 hours continusly before the motor gets so hot it fails.
however in a music application i rate the sub for 750 watts when in a Power Mouse or Band Pass application because that is what it takes to get full cone excursion in such a small enclosure. (the sealed side of the PM is about .5 cuft for a single 10.) in a sealed application the subs play in .75 cu ft for sealed and it would only take about 500 watts to reach Xmax. ported would probly take about 600 watts.

i am not too worried about heat in this application like many subs including your infinity Kappa example. most subs like that dont use much bigger than a 2.5" diameter coil and they also dont have the cone excursion as mine do. that means there is less surface area of the coil to dissapate heat.
my subs have such a high temp rating on the coils i would expect them to fail mechanically before thermally.

however in small enclosures regular name brand subs seem to have their weak spot in the coil and its ability to stay cool.

Infinity obviously feels that loading their sub in a more restrictive enclosure will cause overheating of the coil so they reccommend running a lower wattage.
not many manufacturers reccommend band pass applications with their subs because the subs by nature would require a much larger enclosure or will produce poor results when used in this application.

also so little is understood about this type of box and most retail installers lack the knowledge to build one correctly.

 

Right.

I'm looking it at it from an average consumer point of view. The average joe schmoo is going to buy a typical off the shelf sub and in general he'll probably get better overall sound sticking it in a smaller sealed enclosure rather then a larger(or smaller) bandpass. I'm not saying ALL the time, but more so then not. And yes past that more time, more money people can make great sounding BPs...

That's all I meant in my previous message but it didn't sound right from being distracted halfway through me writing it...

 

The Group Delay came from the charts posted on the spec sheet for my Kappa perfect...

Read this:
http://manuals.harman.com/INF/CAR/Bo...re%20Sheet.pdf[/QUOTE]

 

HOLY COW! back the truck up!!!
thoes are leap simulations not power handeling specs. now i know what your looking at.

first of all the power handelling on this sub is rated at 350 watts RMS forget about anything that says PEAK. that simply marketing HYPE

first of all let me begin by saying that sub has a 2" voice coil. in a real world application the best that sub could handle would be 350 watts ON A GOOD DAY! certainly no 2" coil could handel 350 watts contuniously. that is a wish upon a star rating. especially with only 14.15mm xmax.
being realistic that sub would probly take about 250 watts RMS without failure on a regular basis. you could run 350 watts but that would be pushing it. and i only say this because i know what is capable given that size coil.
if you want my honest opinion i wouldnt run more than about 200 watts into that sub in a BP configuration.
about the group delay it doesnt look too bad for a BP enclosure
as for the watts it appears that it would take 500 watts to get the sub to full xmax in the BP design they have listed here. you can tell because the transducer excursion limit is hitting the xmax of the sub with that wattage. however you would need somthing close to a miracle to keep that 2" coil from meltdown in that application.
it is the same with the other applications they have used a wattage that would be needed to get the sub to full Xmax.
it never ceases to amaze me how manufacturers will just blatently LIE about wattage ratings. there is no way on gods green earth that sub would last with thoes power levels in thoes applications.
the leap simulation only shows what the driver would do if in that particular example. it cannot determin when exactly the sub's coil will reach failure temperatures.
it has everything to do with the frequency in which it is played and for how long that will determin the demise of the coil.
for example look at that graph for the BP enclosure. all BP enclosures have a minimum cone displacement point where the resonant frequency of the enclosure is and usually it also happens to be the same or close to the frequency that the impeadance of the sub is at it's lowest. do you see that dip at 60 hz in their example?
at this particular point in a BP enclosure the driver is at it's lowest impeadance (almost 4 ohms) that means it has maximum current flow and maximum power delevered to the sub. unfortunatly in a BP this is also the point at wich the cone is moving the least. this will raise the temperature to its max thermal capacity.
this is why it is CRITICAL to have a driver wth excessive power handeling capacity. this driver wouldnt last long in a BP application unless the watts were kept to a minimum.

 

it actually says 350w on the bandpass chart....500 for the sealed....so that wattage is the wattage it would take to get the sub to its full xmax? is that what im hearing?

 

What BM is saying if I understand him correctly is that LEAP software, used to create those charts, is a software model of excursion travel, not a measurement of what actually happens in real life. In his statements he says that he does not believe that the speaker voice coil would handle that much power and that electrical failure would set in before excursion-related failure, thus saying that the softwre is not reflecting reality.

I'm not cosigning that, but that's my understanding of what he said.

Now, you can't confuse electrical Power Handling with excursion PH. If you accept the model, and the model says that the speaker would be within the excursion limits with a particular box, then the only thing you are worried about at that moment is electrical PH. Will the VC melt or not? The rule used to be, you can use a bigger amp, because the amp won't near its max power often, like it would with a test tone.

Unfortunately, rap music today is a continuous test tone from a bass point of view. The amp will be at higher outputs most of the time if rap and hip-hop are played loudly. Since it's an electical failure rather than an excursion failure, you won't even hear a distorting woofer to warn you if your amp is big enough - it will just go. But you would probably need a pretty big amp in order to have this problem... how big are you talking? How much more are you talking about giving the speaker?


For what it's worth all the BP boxes I ever built for Kappa woofers sounded like crap, even though the SW said they would be good. I would build sealed and see what you think of the sound, you might be just fine. If you want more then look at porting and adding a subsonic filter to your system (unless your amp has one already - a few do...)

 

I already built a 1.0ft^3 sealed box, not bandpass. The amp I ended up picking up was a Polk MOMO C300.2 which gives off 450w x 1 bridged @ 14.4. The amp also has a subsonic filter built in. I did some searching around and it seems a lot of people are running these subs in a sealed box anywhere from the recommended 350w - 600w with no problems. I already ordered the amp anyways cause I got a great deal. I'm inclined to give it a shot.

 

i know it says 350 watts that is my whole point. the problem is with a 2" coil the best you could get is about 250 maybe 300 watts if your carefull not to run it like that for long periods of time.
sure some people may be running 600 watts but im sure its for less than a few seconds. if you put that kind of RMS power to that sub for any extended period of time it woulld melt the coil.

let me finish by saying that manufacturers for the most part with maybe the exception of JL all buy their subs from China at some very very cheap prices. that kappa sub probly cost them 20 bucks to make. they buy huge quantities at a time.
it really doesnt matter to them if the sub fails because most offer a warranty and free replacement. not all will honer warranty on a burnt coil . if they do warranty it the ratio of people that actually retun the sub for exchange is so small that they still make a considerable profit even if they have to replace a few.
so the bottom line is they really dont care if their power handeling ratings are a little high. it all comes down to your competition. if they actually put the power ratings where they should be they would loose sales to their competitors. people will buy the sub that offers the most for the least amount of money.
the power handeling capacity of a sub is a large selling factor to the general public.
if the sub makes it out of the warranty period then the manufacturer is home free.
but all im saying is dont belive everything you read and only about 1/2 of what you see.