Yawn, just a rendering of the new RT-12d subwoofer:

[Jay481985]

In the case of the RSW-15 versus the

KW-120; they both have nearly the same frequency response, but a single

KW can go 3dB louder than a single RSW. The KW also digs quite a bit

lower too. AND the KW is in a smaller cabinet (about 3/4 the size of

the RSW).

wouldn't you say DrWho that to meet the THX requirements that the kw

were a diffrent beast, meaning from the get go the kw120 was designed

to dig deeper hence really an apple to oranges debate. Since the RSW

was designed differently from the get go, saying that the KW digs quite

a bit lower would not conversely lead that the 12 inch motor is better

to dig lower than a 15. Just that the 12 inch was choosen for its

aspect of it being able to dig lower and louder in a smaller enclosure.

I mean if you tuned the kw120 ports to 50 hertz, it would not compare

to the RSW15. If the RSW 15 had dual 18 inch passive radiators as

opposed to a similiar sized pr, the RSW might outclass the kw 120.

There just two different flavors. I know that people will always

compare and such, hey if you like the wood trim of the rsw and have the

room go for it. If you want to meet THX ultra II specs go for a dual

kw120. I mean its like in grammar school where kids would

go cherry is better than grape. Whose to say?[]

BTW mine's bigger than yours!!! []

[ancientdude]

A lot of it comes down to cabinet size:

I think that a 15" is really the golden number for a sub size, especially within an IB.

Even if a 12" possesses more perfection within its simple idea.

[CECAA850]

A lot of it comes down to cabinet size:

I think that a 15" is really the golden number for a sub size, especially within an IB.

Even if a 12" possesses more perfection within its simple idea.

Some 18's work extremely well in an IB. It all depends on the driver.

[DrWho]

Just that the 12 inch was choosen for its aspect of it being able to dig lower and louder in a smaller enclosure.

Isn't lower and louder that which defines a better sub? (and the fact that it's a smaller enclosure is an extra plus). I'm pretty sure the distortion ratings are definetly about the same (if anything, a listening test shows that the KW has a less colored sound).

This really isn't an apples to oranges debate because we're talking about using the same motor. Sure, the KW tacked on a few small improvements from the RSW, but it's the best comparison I can think of.

My entire point was just to show that there are some physics supporting going to smaller drivers and that I highly highly doubt klipsch is "selling out." They've been doing a ton of research on subs and passive radiators...I'm not privy to this information (due to the nature of the market nobody is really sharing research), but I do know they've made huge strides. And that's not to say there aren't compromises in the designs they release...compromises are the nature of the industry and are required to have a sellable product. The point here is that if klipsch wanted to design a sub that played flat down to 10Hz @ 130dB that they would have no problem doing so - it would however be insanely expensive and totally unmarketable because it'd be way too huge.

[formica]

Just that the 12 inch was

choosen for its aspect of it being able to dig lower and louder in a

smaller enclosure.

Isn't lower and louder that which defines a better sub? (and the fact that it's a smaller enclosure is an extra plus) .

I think Jay got it partially right as it'll play "lower" in the SAME

smaller box if it actually uses the same motor... but why use the same box... or motor? The smaller box isn't an extra, but rather THE deciding factor.

By keeping the same motor; BL, Xmax, Pe, etc remain about** the same...

Sd and Vas drop and probably Mms drops (unless they use a much heavier

/ in2 cone) while Fs goes up. So you end up with a smaller box

with a smaller driver with the same max excursion and power handling

(so it won't play as loud nor as deep). Might as well design a

motor and box specifically for the product at hand.

KW120 does not use the same motor as the RSW15 (as per Deon's posts in the past)...

It's all a question of what the marketing department felt they could

sell the most of... a premium compact sub versus a performance

oriented larger one. Scale up the RT12 to a RT15 and it'll dig

deeper and play louder... but it'll take up more room.

I guess big doesn't sell, but is sure is fun to brag about...

ROb

[Tom Adams]

Just that the 12 inch was choosen for its aspect of it being able to dig lower and louder in a smaller enclosure.

Isn't lower and louder that which defines a better sub? (and the fact that it's a smaller enclosure is an extra plus) .

I think Jay got it partially right as it'll play "lower" in the SAME smaller box if it actually uses the same motor... but why use the same box... or motor? The smaller box isn't an extra, but rather THE deciding factor.

By keeping the same motor; BL, Xmax, Pe, etc remain about** the same... Sd and Vas drop and probably Mms drops (unless they use a much heavier / in2 cone) while Fs goes up. So you end up with a smaller box with a smaller driver with the same max excursion and power handling (so it won't play as loud nor as deep). Might as well design a motor and box specifically for the product at hand.

KW120 does not use the same motor as the RSW15 (as per Deon's posts in the past)...

It's all a question of what the marketing department felt they could sell the most of... a premium compact sub versus a performance oriented larger one. Scale up the RT12 to a RT15 and it'll dig deeper and play louder... but it'll take up more room.

I guess big doesn't sell, but is sure is fun to brag about...

ROb

Rob - From my "Ring...ring" thread, Trey Cannon said: "The THX sub is very fast. As it is a 12 inch cone on the RSW 15 motor in a ported cabinet."

Tom

[DrWho]

I know Deon doesn't like me throwing his name around but he did in fact tell me that it's the same RSW-15 motor. Totally identical except for one thing (and I think I have an idea as to what it is considering a concept that's being bragged about lately by others in the industry - though they all call it something different).

Anyways, my point is that you can take this motor and then maximize the performance out of the rest of the available specs for each the 15" and 12" driver. Believe it or not, there is a point where the cabinet becomes too big and you loose SPL because of it. And there are EQ's and processing that are being done that even further enhance performance - while also requiring the cabinet to get smaller again (think of how the subwoofer is barely moving at the tuning frequency). With any kind of bass-reflex design, you have two areas where the cone excursion is at its max - about half an octave above and below the tuning frequency. Reducing the cabinet size reduces the cone excursion both above and below the tuning point - so even though it's a smaller driver, the smaller cabinet allows more SPL from the same excursion (because of how you align the tuning point). It's hard to explain and I'd really have to sit down and run through the modelling programs to show it.

And I am by no means a subwoofer expert - That would be guys like Deon and Tom Nousaine. I've talked about the few tricks I've picked up along the way that I've never seen in the DIY world and Deon told me that I'm only scratching the surface. There is a lot that goes on between the speaker and the amplifier that can be tweaked to improve on the sound quality as well. I'm doing my best to learn these tricks, but I can see why these smart dudes don't wanna share all their secrets []

Btw, one way of thinking about the situation is that the surface area of three 12" drivers = two 15" drivers. You will also note that the cabinet volume of three KW's = two RSW's. But you get more output with the KW's because you have three motors instead of two (the system is more efficient). Without the slight modification to the motor I bet you would get the exact same results actually.

[thxsubwoofers]

I wouldn't mind a picture of the motor behind the subwoofer cone. [] I must say, in my opinion that only the rubber surround, sorta looks like the MTX9500. I could be wrong from just pictures..... The new Klipsch RT-12d looks mean.... Its one of my favorite home theater subwoofer pictures.[]

[Jay481985]

look at page two where remotia is holding it. BTW the rubber surround

that has a triangular look is for high excursion cones. Meaning that

triangular look has more excursion capability than normal.

[Jay481985]

I know Deon doesn't like me throwing his name

around but he did in fact tell me that it's the same RSW-15 motor.

Totally identical except for one thing (and I think I have an idea as

to what it is considering a concept that's being bragged about lately

by others in the industry - though they all call it something

different).

let me take a stab, "bottomless" or XBL technology?

[formica]

Anyways, my point is that you can take this motor

and then maximize the performance out of the rest of the available

specs for each the 15" and 12" driver. Believe it or not, there is a

point where the cabinet becomes too big and you loose SPL because of

it.

Yes, and gain bass extension in exchange

so even though it's a smaller driver, the smaller

cabinet allows more SPL from the same excursion (because of how you

align the tuning point). .

More SPL at a higher frequency... but if you EQ it flat again, you'll become excursion limited.

Your SPL / extension will always be dependant on the air you can

displace... so the 15" will always have the advantage if it's

properly provided for.

- Let's assume available power is unlimited.

- If the 12" and 15" share the same motor and excursion (same

motor = same excursion), and both placed in ideal enclosures...

the 15" will displace more air, therefore it can play lower and

louder.

- Now you place both these drivers in the same enclosure with no EQ

(linkwitz or other)... your 12" will be closer to it's ideal than the

15" so it could play lower. But this isn't really fair for the

15" as it had to run the race with one leg tied behind it's back.

- Now you now apply a transform (EQ) to them both so they can attain

the xmax (assume neither driver is thermally limited). The 12"

gets a little boost, while the 15" get more... so now the 15" has

become less efficient than the 12" but it will once again play lower /

louder.

When you are surrounded by trees, sometimes you have to stand back an look at the forest. []

ROb

PS:

Rob - From my "Ring...ring" thread, Trey

Cannon said: "The THX sub is very fast. As it is a 12 inch cone on the

RSW 15 motor in a ported cabinet."

I realise Trey mentioned they have the same motor... but unless they

offer the same Xmax (excursion) they will have a different voice

coil. The number of T/S parameters you can vary in modifying the

voice coil, makes it (for me), a different motor.

[DrWho]

I'm not talking about the performance of each driver in the same cabinet. I'm trying to point out that for the same motor, you can get more performance from a 12" driver per cabinet volume. Think of cabinet volume as costing $1000 for every cubic inch. It will be cheaper to achieve a target performance with more smaller drivers than it will with less larger drivers - simply because cabinet volume "costs" so much. The key here is that you're using the exact same motor and you're trying to minimize cabinet volume. I'm not trying to say that you can't get better performance out of a 15" driver with the same motor in a larger cabinet - but if you can get the same target with the 12" that you can the larger 15", then why not?

Since you've got winISD, play around with the addition of a peaking 2nd order high pass - something like 6dB of boost just above the tuning point. And then notice how you need to reduce the cabinet size to maintain a flat response, which then reduces the cone excursion above the tuning point and allows you to pump more power into the system. Between a single 12" and 15" driver, you're looking at a decrease of 3dB maxSPL with the 12" driver. But if you were to use 1.5 12" drivers, you would then exceed the performance of the 15" driver and be using up the same cabinet volume as the 15". Since you can't use 1.5 in the real world, I was using the analogy of 3 12" drivers and 2 15" drivers. You end up with the same amount of driver surface area, and thus the same amount of displacement, but with the smaller drivers you have three motors instead of two - thus if nothing else, you reduce distortion (or even better, you can extend the LF response lower).

[formica]

I'm trying to point out that for the same motor,

you can get more performance from a 12" driver per cabinet volume.

Only if the driver is thermally limited or if the power available is

limited. If it's excursion limited (the common situation)... the

15" will offer better performance

Think of cabinet volume as costing $1000 for every cubic inch.

So now we are back to where the enclosure size is the deciding factor

and the others are compromised in consequence. You are correct in

placing a high "value" to size as this is what the marketing staff

decided was the best compromise.

Hoffman's law applies, regardless of driver size or if the sub is

EQ'ed... The engineers just tried to do the best within the

limitations placed on them by the marketing dept.

ROb

PS: I somehow think we lost a lot of the original posters... as

we are beginning to sound as technical as ALK, BEC, and John Warren in

a x-over discussion.[:$][]

[DrWho]

lol, i like cheese too []

Btw, you can also model the Dayton Titanic 12" versus the 15" - you'll find you can get better performance out of two 12" drivers with the same cabinet volume [] (5 cubic feet or so).