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Fact or Crap? There is no replacement for displacement.

Do larger format drivers produce a superior bass quality, regardless of EQ and power level?

  • Yes. You can’t change physics.

    Votes: 52 85.2%
  • No. Excellent design levels the playing field.

    Votes: 9 14.8%

  • Total voters
    61

Tom C

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The topic comes up from time to time in discussions of speaker reviews. Rather than contribute to derailing of a review thread, thought I’d post here.
Can a 5-in mid/bass driver, properly implemented in a well designed system, eq’d and level matched, produce output that is audibly indistinguishable from the output of a system using, say, a 10” or 12” driver? Based on personal experience (a limited resource for sure), I would say no. The output of a larger driver will produce a superior sound quality in the mid and upper bass, and it will be easy to hear the difference compared to a smaller driver.
 

Digital_Thor

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I touched upon the subject here:

Because I find it difficult to wrap my head around an 6" playing bass like a 8" or 10" - simply by having more linear P-P.
 

Josq

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Let's take some very well designed speakers. For example Genelec The Ones. Is the large 8631 better than the small 8331? I never heard them, but obviously the 8361 can go deeper and louder than the 8331.

But suppose we listen to both of them at a very moderate listening volume to music without low bass content (so that deep bass extension, max SPL and distortion is not remotely a concern), would they perform different? I doubt that.
 

antennaguru

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You can use multiple smaller drivers to sound more like a single larger driver. Sometimes they are all visible on the front panel, like with a Short Line Array. Other times like with the Linn Sara they are set up using Isobaric loading so that only one is visible on the front panel and a second one is behind the visible one, helping. Then there are the M&K push-pull subwoofers.

I built a pair of Short Line Arrays with four 3 inch drivers each, and their mid bass was as good as a larger driver. They were augmented by a subwoofer for the lower bass, and no tweeter was needed.
 

Digital_Thor

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@Josq: True, but then everything also points directly towards max SPL and extension - namely Hofmann's iron law. As I understand Lars Risbo from Purifi Audio, he says that more linear and low distortion, but high excursion, equals a larger driver with less linear excursion. And when searching for a woofer to fill in the spot in 2-ways, it might be fine - even though we end up with lower total sensitivity.
 

DVDdoug

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Can a 5-in mid/bass driver, properly implemented in a well designed system, eq’d and level matched, produce output that is audibly indistinguishable from the output of a system using, say, a 10” or 12” driver?
Not if the one with the larger driver is also "well designed".

And, you'll rarely run-across two different speaker deigns that are indistinguishable from each other. ;)
 
OP
Tom C

Tom C

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I have towers with 7” woofer x 2. It’s definitely better than, say, the multiple bookshelf types I have with 5” or 6” woofer. But nothing like the slam of the 2-way with 10” woofer that’s in my home gymn.
 
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Tom C

Tom C

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One thing you have to deal with when using multiple smaller drivers is the drop in load impedance as more are added. Don’t you need to use a driver with relatively high impedance, so the array of them all together is a manageable load for the amplifier?
 

Spkrdctr

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Nothing like 2 18 inch subs to give you some slam. You really have to pressurize the room to get serious absolute in your chest slam. The room size becomes a big factor. Trying to get any slam in a large room is very costly. A small or smallish medium size room is much easier to do. But, I can't afford to play in that game anymore. But I do know how to get there!
 

DVDdoug

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Don’t you need to use a driver with relatively high impedance, so the array of them all together is a manageable load for the amplifier?
That's a different issue. Two 8-Ohm speakers is 4-Ohms which is twice the current and twice the power (assuming the amplifier's voltage doesn't drop) and in series it's 16-Ohms for half the power.

4 or 16 speakers can be wired in a series-parallel combination with no change in in impedance but of course you get 4 or 16 times the power handling with each speaker getting an equal share of the power. Or you can use different speaker quantities in different series or parallel combinations.

BTW - I have two 15-inch subs in my living room along with 12-inch woofers in the left & right main speakers. The speakers I'm using for my rear channels (which somebody gave me) have 15-inch woofers.
 

Josq

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So, if you want high SPL in a large room then I think it is certainly true: there is no replacement for displacement.
But in a small room or for near field listening, even very small speakers can get very loud.

The other factor is low frequency extension. If you have a sub crossing over at 80Hz, I don't think it matters a bit if the main speakers have extension to 50 Hz or 30 Hz.

In my specific situation, I'm using a sub and I'm listening in nearfield. I don't see any added value in large speakers in this case.
 

Spkrdctr

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So, if you want high SPL in a large room then I think it is certainly true: there is no replacement for displacement.
But in a small room or for near field listening, even very small speakers can get very loud.

The other factor is low frequency extension. If you have a sub crossing over at 80Hz, I don't think it matters a bit if the main speakers have extension to 50 Hz or 30 Hz.

In my specific situation, I'm using a sub and I'm listening in nearfield. I don't see any added value in large speakers in this case.

Yes, for bass you need serious displacement. If you are talking sub bass then displacement and cabinet size is king. Think like a huge JTR sub. Big driver and big cabinet. Near field is so easy to do it is really almost buying any decent set of speakers.

I should bring up a point of safety here. Do not ask me how I know this :) OK, young and dumb. Do NOT ever think that subwoofer bass can't hurt your ears. It will and can hurt your ears at high levels. Protect you hearing at all times and don't put your head inside commercial sound giant bass bins and crank it up. You will regret it later in life. So, with safety out of the way, the old adage is buy as much and as many subs as you can until you hit the "just plain crazy" level.

My own personal test back in the day was the old incandescent lights bulbs, if you are breaking the filaments with your subwoofer set up, you have great bass!!! Or, maybe a bit too much? Either way, I liked it.
 

AnalogSteph

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Look up driver data and do the math.
Purifi PTT6.5X04-NFA-01, a 6.5" long-stroke midwoofer: Sd = 133 cm², Xlin = +/- 10 mm, sens = 85.7 dB / W / m, Pmax = 250 W. Z = 1.5 * Zmin @ ~2 kHz, Z = 2 * Zmin @ ~4 kHz.
Visaton W 250 S, a traditional mid-priced 10" standard stroke woofer: Sd = 346 cm², Xlin = +/- 5 mm, sens = 90 dB / W / m, Pmax = 100 W. Z = 1.5 * Zmin @ ~600 Hz, Z = 2 * Zmin @ ~1.4 kHz.

The Purifi can get about 3/4 the displacement (= Sd * Xlin) of the much bigger Visaton, which is not shabby at all. Power-limited midrange SPL is only about 0.3 dB behind as well. On top of that, the Visaton is pretty much a woofer only and should ideally be crossed not much higher than 600 Hz, or maybe 1 kHz if you must, otherwise electrical nonlinearity in the midrange is likely to get out of hand as indicated by rising impedance. Best used in a 3-way, while the Purifi has a chance of being used in a 2-way with an appropriately waveguided tweeter.

So no, you cannot cheat physics, but you can very much put up a good fight by using every trick in the book to push the envelope.

I don't see a 5" overtaking a 10-12" any time soon though, the disparity in Sd is just too large and power dissipation requirements would get even more extreme. Even in order to keep up with a lowly W 250 sans S (360 cm², +/- 3 mm), a 5" / 130 mm class model (Sd ~80 cm²) would need an Xlin of +/-13.5 mm. Relative to driver size, that would be even more extreme than the +/-8.5 mm in the 4" Purifi. To keep up with the W 250 S, you'd even need +/-21.6 mm, which is just insane... not to mention Doppler distortion galore.
 

ebslo

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I touched upon the subject here:

Because I find it difficult to wrap my head around an 6" playing bass like a 8" or 10" - simply by having more linear P-P.
That post includes the following assertion, which I have seen repeated elsewhere but never justified (emphasis mine):
Such Kms(x) disortion mostly causes harmonic disortion down towards fs and below (where it is not much audible)
Can anyone provide a reference or make a convincing argument for why distortion from a low-frequency fundamental would be less audible?
The following counter argument is presented on the audiocheck.net distortion test page:
At 1kHz, the standard THD test tolerates relatively high levels of distortion. By decreasing this frequency, we will shift the fundamental towards a frequency range where our hearing is not as sensitive anymore, and allow the harmonics produced by the distortion, to fall back into the frequency area where our sensitivity is maximal. Lower sine tone frequencies make distortion easier to hear.


In addition, the number of audible harmonics increases drastically as the frequency decreases. For example, if you perform the test at 100Hz, distortion will spread over 65 harmonics (300Hz, 500, 700, 900, ... 19500Hz) - to be compared with the 9 harmonics of the classic THD test (see above).
I don't mean to derail the thread with this, but it does seem pertinent as distortion of low-frequency content would likely be considerably different between hi and low displacement drivers.
 

mhardy6647

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Seems like a good time to quote Col. Paul Wilbur Klipsch. He made some awful sounding loudspeakers but he made 'em the way he wanted to... and he had a way with words. :)

They make miniature tubes and miniature loudspeakers, but they have yet to come up with a miniature 32-foot wavelength.
source: http://www.klipsch.com/quotes-anecdotes
I'm certainly on the bus, as it were. :cool:

DSC_0938 (3) by Mark Hardy, on Flickr
 

Kvalsvoll

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The topic comes up from time to time in discussions of speaker reviews. Rather than contribute to derailing of a review thread, thought I’d post here.
Can a 5-in mid/bass driver, properly implemented in a well designed system, eq’d and level matched, produce output that is audibly indistinguishable from the output of a system using, say, a 10” or 12” driver? Based on personal experience (a limited resource for sure), I would say no. The output of a larger driver will produce a superior sound quality in the mid and upper bass, and it will be easy to hear the difference compared to a smaller driver.
Yes, it can. If the room/listening distance is not too large, bass is reproduced by a decent bass-system, and the driver/speaker has high output capacity - it needs to handle both high current and quite long excursion.
 

pierre

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Let's take some very well designed speakers. For example Genelec The Ones. Is the large 8631 better than the small 8331? I never heard them, but obviously the 8361 can go deeper and louder than the 8331.

But suppose we listen to both of them at a very moderate listening volume to music without low bass content (so that deep bass extension, max SPL and distortion is not remotely a concern), would they perform different? I doubt that.

I can confirm there is little differences between them (8361 / 8341 / 8330) at low volume and without bass content. I fooled myself many times.
Of course on
you definitively need the big ones (and a sub will help).
 
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