Floorstanding with umpteen medium woofers or one giant woofer? - AVS Forum
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post #1 of 19 Old 08-20-2013, 07:15 PM - Thread Starter
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Can someone explain the pros and cons of something like the Paradigm Signature S8 - it has 4 x 7" woofers doing the same thing (is that right?) ... surely that can't be good even though it's vertically aligned? I'm struggling to think why they'd want to do that instead of one 7 inch woofer?

I know that visiting the shops to audition will give me the feel of the difference but I am unable to do that and i'd like to know what the theorists think.

Thanks

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post #2 of 19 Old 08-20-2013, 07:45 PM
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Well this will be a bit of a reach but perhaps it's about how much air four 7” drivers can move. Using the equation pi*r^2, four 7” drivers have a surface area of about 152 square inches. Roughly equivalent to one 14” driver, with a surface area of about 154 square inches. Individual 7” drivers will perhaps be less prone to cone breakup and distortion than a single large 14” driver. This might provide you with a more accurate frequency response.

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post #3 of 19 Old 08-25-2013, 05:36 PM - Thread Starter
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I guess no one knows huh ... so it can't be bad?

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post #4 of 19 Old 08-25-2013, 06:06 PM
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Quote:
Originally Posted by joker97 View Post

Can someone explain the pros and cons of something like the Paradigm Signature S8 - it has 4 x 7" woofers doing the same thing (is that right?) ... surely that can't be good even though it's vertically aligned? I'm struggling to think why they'd want to do that instead of one 7 inch woofer?

I know that visiting the shops to audition will give me the feel of the difference but I am unable to do that and i'd like to know what the theorists think.

Thanks

Woofers are usually lower in sensitivity, compared to tweeters, so adding additional woofers, raises the sensitivity. This allows the speaker to achieve higher SPL and lower distortion.

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post #5 of 19 Old 08-25-2013, 06:12 PM
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Originally Posted by joker97 View Post

Can someone explain the pros and cons of something like the Paradigm Signature S8 - it has 4 x 7" woofers doing the same thing
Smaller drivers have wider dispersion than larger drivers. The down side is they have less displacement, so to get the combination of wide dispersion plus high displacement you use more of them. In this case, with a 230Hz crossover to the mid driver, there's no need to go to seven inch woofers for dispersion, as even an eighteen has very adequate dispersion to at least 500Hz, so the choice of four sevens would be mainly cosmetic, allowing for a very thin cabinet.

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post #6 of 19 Old 08-25-2013, 10:25 PM
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You get much more output out of 4 drivers vs 1. Also since the sound frequency is split up amongst the four, you get better separation as well. The tricky part is you need a good crossover design in order for something like this to sound seamless.

The drivers aren't doing the same thing. Each one takes a portion of the sound frequency. They're not all playing the same thing at once...

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post #7 of 19 Old 08-26-2013, 05:17 AM
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Originally Posted by Menasor View Post

since the sound frequency is split up amongst the four, you get better separation as well. The tricky part is you need a good crossover design in order for something like this to sound seamless.The drivers aren't doing the same thing. Each one takes a portion of the sound frequency. They're not all playing the same thing at once...
-1. In this case the four sevens are all covering the same bandwidth. There is no crossover between them.

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post #8 of 19 Old 08-26-2013, 05:46 AM
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Quote:
Originally Posted by joker97 View Post

Can someone explain the pros and cons of something like the Paradigm Signature S8 - it has 4 x 7" woofers doing the same thing (is that right?) ... surely that can't be good even though it's vertically aligned? I'm struggling to think why they'd want to do that instead of one 7 inch woofer?

I know that visiting the shops to audition will give me the feel of the difference but I am unable to do that and i'd like to know what the theorists think.

Going down this road of trying to deduce woofer bass extension and dynamic range from things like cone sizes (which has some pitfalls and shortcomings)

The ultimate measure of a subwoofer is the amount of air it can move with reasonable linearity.

This in turn can be found from diaphragm area and Xmax or linear travel, usually given in millimeters (mm).

The unsolvable problem related to small drivers is that Xmax tends to decrease with cone diameter when cone diameter is less than about 13". This is because the linear travel of the suspensions of woofer cones are based on bending angles of the surround and spider and the same limits on bending angles exist regardless of speaker size. Once the bending angle is limited to a certain number, the Xmax is based on the diameter of the speaker driver.

For example there are 13 inch drivers with 36 mm or more Xamx, but there are no 8 inch drivers with much but a fraction of that. I think the most xmax I've seen out of an 8" driver is 12 mm.

So, even though two 8 inch drivers have approximately the diaphragm area of one 12" driver, the 12 inch driver might have twice or more the Xmax. Therefore it might take 4 or more 8 inch drivers to give the air handling power of a single 12 inch driver.


Getting into your example of four 7" woofers, the air displacement is about the same or even far less of that of one 12" woofer, presuming the 7 inch woofers and the 12 inch woofer were configured to the max possible for their diameter.

More details here: http://barefacedbass.com/technical-information/speaker-size-frequency-response.htm
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post #9 of 19 Old 08-26-2013, 08:05 AM
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Originally Posted by Trendy View Post

Well this will be a bit of a reach but perhaps it's about how much air four 7” drivers can move. Using the equation pi*r^2, four 7” drivers have a surface area of about 152 square inches.

As a rough approximation using nominal diameter which is based on frame size is OK, but the actual diaphragm size of a speaker is significantly less than the size of the frame because of the area lost to the surround. Only the inner edge of the surround moves with the cone, and the outer edge does not move at all.

For example I have here a Stereo Integrity 15", but the actual diaphragm is more like 12". A good estimate would be that the travel of the cone is uniformly distributed across the 3" surround, so about 1 1/2" of the surround is effectively moving with the cone. The diaphragm diameter is thus effectively 13 1/2 inches. We lost about 10% of the diameter or nearly 20% of the cone area.
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Roughly equivalent to one 14” driver, with a surface area of about 154 square inches.

I'll take that at face value.

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Individual 7” drivers will perhaps be less prone to cone breakup and distortion than a single large 14” driver.

Reference: http://www.paradigm.com/products/series=signature/model=signature-s8/page=specs

The low pass crossover for the woofers is said to be 230 Hz, so cone breakup just isn't an issue. Breakup of 8" cones can be counted on to be higher than 1 KHz, and usually several times that.

As far as distortion goes, for woofers that depends mostly on the voice coil and magnet. In another post I just made I explain why smaller drivers are prone to lower linear limits in this important performance area.
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This might provide you with a more accurate frequency response.

It looks to me like they are trying to use a column of 4 smaller drivers to allow building a more stylish, narrow enclosure. 4 drivers are more than enough to create a column array, which limits vertical dispersion while maintaining a certain amount of horizontal dispersion. Controlling vertical dispersion helps limit the mid-bass notch due to the "floor bounce". The low crossover helps avoid lobing due to multiple drivers as does the edge-to-edge placement.
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post #10 of 19 Old 08-26-2013, 10:24 AM
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Originally Posted by Bill Fitzmaurice View Post

-1. In this case the four sevens are all covering the same bandwidth. There is no crossover between them.

Doh. I stand corrected

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post #11 of 19 Old 08-26-2013, 12:16 PM
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Arnold, thank you for the additional insight.

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post #12 of 19 Old 08-26-2013, 01:53 PM - Thread Starter
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so i can conclude that the additional 3 woofers in the signature s8 is purely cosmetic to charge more money, doesn't do much, and doesn't degrade the sound much. correct?

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post #13 of 19 Old 08-26-2013, 02:36 PM
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Originally Posted by joker97 View Post

so i can conclude that the additional 3 woofers in the signature s8 is purely cosmetic to charge more money, doesn't do much, and doesn't degrade the sound much. correct?
Only if you did not read anything that was posted. confused.gif

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post #14 of 19 Old 08-26-2013, 03:22 PM - Thread Starter
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ah yes lower distortion higher sensitivity!

that is so weird that the sensitivity goes up when there are more drivers to drive!

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post #15 of 19 Old 08-26-2013, 03:31 PM
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Think of the fans in a pc. Even if you use all the same fans when you hav 8 running it is much louder than if you only had 1 running. The sound waves all come together and construct a more intense sound wave which can be 2-4 times as loud as if only one were running. This applies to speakers as well. There are a lot of variables and a lot of generalizations were made however the essence is there.
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post #16 of 19 Old 08-27-2013, 01:43 AM - Thread Starter
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I see ... thanks ...

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post #17 of 19 Old 08-27-2013, 03:20 AM
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The sensitivity depends on how the woofer are wired, and that depends on the woofer sensitivity. In most cases are wired parelled thus the increase sensitivity.
As far as with the S8, with its overall height at 48 inches, i thing they are more meant to fill large room longer listening distance. If they are used in closer listening distance, the height of the listening spot may need to be higher to level with the tweeter for best results.
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post #18 of 19 Old 08-27-2013, 04:32 PM - Thread Starter
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Hey it makes good sense ... the ones with umpteen woofers are for larger rooms and vice versa! Hmm I might have a target overt simplistic world view ...

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post #19 of 19 Old 08-27-2013, 06:22 PM
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Well you can definetly use the S8 in a smaller room. My point is that the tweeter height is so high, they are meant for longer listening distance where off vertical axis is lesser over a short listening distance. Not because of the 4 woofers.
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