size of the driver

My drivers only five feet, I don't no how he sees over the steering wheel.

"I really can't think of anything much worse than a large system poorly designed/executed "

Have heard such and gotta agree. Glad I only heard and did not pay!

"By the way, if you listen to rock concert music, nothing beats big boxes with high efficiency 15 or 18 inch drivers, for the simple reason that these are exactly what you hear at the concert. Horn mids and tweeters also. IMHO, horrible, but accurate."

Often horrible, yes, but I have heard it done well both in smaller clubs and large stadiums in recent years. I had seats right in the "sweet spot" at the last Paul McCartney concert at FedEx Field in DC and the sound was the best I have ever heard at a large stadium event by far, quite good actually even by audiophile standards I would say. I hadn't been to a similar large stadium event in years because I had sworn them off years ago, bad sound quality being just one of the reasons. Those seats were not cheap though!

Speakers used were large and efficient no doubt in that venue. The sound "columns" on either side of the stage were I would guess 40-50' high and each consisted of many units/drivers functioning in an array.

I would guestimate that if the venue from where I sat, about two sections back dead center, were scaled down to fit into a decent sized home listening room, the speakers would stand ~ 6-7' tall and 2-3' wide and likely each be quite heavy still as well.

I also know of at least one local venue where name acts of all genres including Rock can be heard in an intimate club setting for very reasonable cost and sound quality is also top notch (still best in teh "sweet spot") having heard it from that sweet spot on multiple occasions.

BTw, can anyone guess what the good sounding seats in both large stadium and intimate club had in common other than being in the sweet spot?

Answer:

˙uoıʇɐʇs/sʎnƃ punos ǝɥʇ oʇ ǝsolɔ pǝʇɐɔol ǝɹǝʍ ʎǝɥʇ

By the way, if you listen to rock concert music, nothing beats big boxes with high efficiency 15 or 18 inch drivers, for the simple reason that these are exactly what you hear at the concert. Horn mids and tweeters also. IMHO, horible, but accurate.

"However, for those whose first-priority is realism, seeking to combine the fore-mentioned attributes with truly realistic tone, the choice seems to be limited to relatively scarce systems with large mid-woofers (dynamism is another benefit that, more often than not, comes with most of the existing large-coned examples)."

In larger rooms, larger drivers or multiple drivers would seem to be the options.

"So I guess the choice between the large and the small driver all comes down to; which attributes are more important to the individual. It's a matter of 'picking your poison', in other words, I suppose."

No doubt about the picking your poison (or pleasure, however one might term it ) part. Personally, I like sound best when it has what I often refer to as "meat on the bones" along with all the rest. Larger or multiple drivers usually accompanied by larger and heavier enclosures are two ways to potentially accomplish that .

I run multiple speakers in multiple rooms ranging in size from 12X12 to 20X34. My smaller speakers work well in teh smaller rooms and the larger ones can as well but only the larger ones can cut it in the larger rooms.

ITs no mystery why in virtually every line of speakers, the larger better built ones tend to cost the most. True even of exclusive high end lines like Magico, I believe. But not everyone needs or can even afford those.

Most people would love to have a Lamborghini but practically settle for Toyotas.

Waj4all:
After all, the headphone (just as the small speaker) measures flat thru-out its frequency-range, as is apparent in close proximity (i.e. clamped to the ears). But then, any distance between the 'phone and listener causes it to sound more like a tweeter. All frequencies are being reproduced, but the small surface-area of the 'phone's drivers is incapable of coupling enough air to transmit the lower frequencies (i.e. below treble) to the listener.

Yes. it comes down to coupling the bass output to the room size. Even a pair of Wilson Alexandria XLF's would sound bass-shy outdoors. Perhaps preferred woofer sizes are related to customary listening room sizes.

05-01-12: Waj4all
>I wonder as to whether the experts in this thread would have a theory as to why the double-stacking of small speakers causes a subjective increase in the robustness of lower-midrange tones? This has been my experience, and I've seen where others have spoken of this phenomenon.

Wave lengths are longer at lower frequencies so the path length differences in the direct sound and reflections result in a lesser phase shift compared to the higher frequencies so the lower frequencies sum closer to +6dB compared a single speaker while the higher frequencies have lesser gains and even some comb filtering.

>And similarly, is it a fact that large mid-woofers are intrinsically more robust or warm at lower-mids than small-coned designs, perhaps, because of the same surface-area effect?

No.

Low frequency extension depends on SPL. If toy woofers (sorry: 6 inch woofers) are tested at low spl they go deep. A 12 or 15 inch woofer goes deep at reasonable spl. Consider headphones. They go very deep, but their spl is very low, and satisfactory only because they are right on your ears.

I tend to look at it from the perspective of basi physics.

Size matters in order to pressurize air more effectively.

Larger rooms and lower frequencies at higher volumes require more air be pressurized to maintain a smooth frequency response. Larger drivers have the advantage.

The dilemma is that larger drivers will tend to have more mass. More mass means more inertia. Inertia is the enemy of transient response. Transients are an important part of real music. Therefore larger drivers are at a disadvantage when it comes to transient response.

A lot of what works best comes down to a matter of scale ie how much speaker is needed to deliver the desired scale of performance in the target roo m.

All you have to do is go to Parts Express or Madisound websites and look up the specs on various drivers of different sizes and types, including "pro". Some have detailed frequency response and impedance graphs. You can go further by plugging some of those T/S numbers into a speaker box calculator.

For example, plain and simple...
http://www.bcae1.com/spboxad2.htm

Some of you might be in for a shock. The evidence speaks for itself but interpretation varies.

I tend to look at it from the perspective of basi physics.

Size matters in order to pressurize air more effectively.

Larger rooms and lower frequencies at higher volumes require more air be pressurized to maintain a smooth frequency response. Larger drivers have the advantage.

The dilemma is that larger drivers will tend to have more mass. More mass means more inertia. Inertia is the enemy of transient response. Transients are an important part of real music. Therefore larger drivers are at a disadvantage when it comes to transient response.

A lot of what works best comes down to a matter of scale ie how much speaker is needed to deliver the desired scale of performance in the target roo m.

05-01-12: Drew_eckhardt
04-29-12: Johnnyb53
>04-29-12: Tamule1
>real bass comes from moving a large surface area gently -not a small surface violently . 6.5" is not a woofer size IMO

"Violent" isn't a problem until you reach the linear or physical limits which geometry dictates you do when using such small drivers.

>And you base this opinion on what?

I draw upon personal experience with speakers including transmission lines built with similarly small drivers...

Drew, it's pretty obvious I was responding to Tamule1 and not saying anything concerning your previous statements. I question his setting a size definition on woofers that essentially excludes 90% of them. A driver doesn't have to function well as a subwoofer in order to be a competent woofer.

Your enthusiasm for larger drivers is already well known. You play down the disadvantages of the flex and weight of a larger diaphragm, the cost and bulk of a larger magnet structure, the dispersion enhancement of a waveguide (I've yet to see a waveguide on a 12" driver to turn it into a midrange) while pointing out the disadvantages of longer excursion, small radiating area, etc. of smaller diameter bass drivers. It's really a matter of picking your poison.

If cost, size, and weight are not important factors, fine. Knock yourself out and put in 12" and 15" drivers. If WAF, floorspace, and bass speed at affordable prices is important (and it's intuitive that this package is an easier sell to both sexes), then the narrow column anchored by multiple 6.5" woofers rules. And that's why they dominate the sweet spot (not the highest end) in high performance loudspeakers.

Probably a topic for a different thread, but I would be really interested in better understanding how the better known Walsh style driver/designs differ from the more conventional approach in terms of these common parameters that help determine speaker performance.

How does a downward oriented, open-back Walsh driver manage to deliver seemingly flat and extended frequency response at very high SPLs horizontally in a largely omnidirectional manner compared to a say a single similar sized conventional driver generally firing more directly at the listener?

The answer seems to lie somewhere in the domain of "wave bending" in the Walsh theory, as opposed to pistonic motion which I believe accounts for most of the output associated with traditional dynamic designs?

I kind of understand the theory based on wave propogation through materials of different density "bending" or diffracting the wave, but would have no clue how to relate it in technical terms comparable to what Drew and others here have so eloquently related, nor how to apply it effectively in practice, other than via trail and error perhaps.

Here's what Wikipedia has to say about it FWIW:

"Bending wave loudspeakers
Unbalanced scales.svg
The neutrality of this section is disputed. Please see the discussion on the talk page. Please do not remove this message until the dispute is resolved. (October 2010)

Bending wave transducers use a diaphragm that is intentionally flexible. The rigidity of the material increases from the center to the outside. Short wavelengths radiate primarily from the inner area, while longer waves reach the edge of the speaker. To prevent reflections from the outside back into the center, long waves are absorbed by a surrounding damper. Such transducers can cover a wide frequency range (80 Hz to 35,000 Hz) and have been promoted as being close to an ideal point sound source.[49] This uncommon approach is being taken by only a very few manufacturers, in very different arrangements.

The Ohm Walsh loudspeakers use a unique driver designed by Lincoln Walsh, who had been a radar development engineer in WWII. He became interested in audio equipment design and his last project was a unique, one-way speaker using a single driver. The cone faced down into a sealed, airtight enclosure. Rather than move back-and-forth as conventional speakers do, the cone rippled and created sound in a manner known in RF electronics as a "transmission line". The new speaker created a cylindrical sound field. Lincoln Walsh died before his speaker was released to the public. The Ohm Acoustics firm has produced several loudspeaker models using the Walsh driver design since then.

The German firm, Manger, has designed and produced a bending wave driver that at first glance appears conventional. In fact, the round panel attached to the voice coil bends in a carefully controlled way to produce full range sound.[50] Josef W. Manger was awarded with the "Diesel Medal" for extraordinary developments and inventions by the German institute of inventions."

I currently own - and will continue to into the forseeable future - a pair of Polish built speakers with a 12" woofer/midrange and 12" waveguide(Geddes-based) "fed" by a compression driver. The 12" units supposedly extend to ~1.5kHz, but I can honestly and wholeheartedly say that I've never heard more (or even as much) cohesive sounding speakers as these(save perhaps the Quad's..), nor are the central mids marred by any signs of "beaming" now that we've entered and passed the above mentioned critical 1100Hz. Moreover, there's just something completely beguiling about the way a 12"(or 15"+) woofer produces bass that's simply not equalled by smaller units, be they one their own(per channel) or multiples. The history of these sonic impressions of mine - i.e. the evidence of my stance, if you will - are based on and generalized by a long list of "representatives" on both sides(speakers with either smaller or larger bass/mid units).

That is to say: many of the con's against larger cones (as well as the pro's directed at smaller units) seems to be founded predominantly in theory, no doubt led on in some instances by marketing efforts, and this goes both with regard to the larger cones qualities into bass reproduction as well as their abilities as midrange units. Whenever these discussions break out it's noteworthy how little is said of actually perceived differences that would in some way, or not, confirm the variety of theories on this - a matter I believe of utmost importance; what I find interesting about the theorizing, or least its attempts on this issue, are trying to come about reasons for the reporting on perceived advantages (or disadvantages, for that matter) of larger units, at least with regard to bass reproduction, instead of seeing the theoretical advantages of smaller units not called into (perceived) question.

Based on what I've actually heard, my foremost area of attention, I can only say that larger bass/mid drivers(12-15"), as well as 18"+ sub-only bass drivers, not only merely "does the job," but in many combinations does so with a clear advantage compared to speakers based on smaller bass/mid drivers. It would require a much longer message to come about the different aspects in which I see these advantages - perhaps another time.

My PMC Fb1i Signature speakers have a 6.5" driver and go down to 28 hz. I wouldn't have believed it before got them, but they have a transmission line design and really do go that low. IMHO, it's all about the design.

04-29-12: Johnnyb53
>04-29-12: Tamule1
>real bass comes from moving a large surface area gently -not a small surface violently . 6.5" is not a woofer size IMO

"Violent" isn't a problem until you reach the linear or physical limits which geometry dictates you do when using such small drivers.

>And you base this opinion on what?

I draw upon personal experience with speakers including transmission lines built with similarly small drivers (I've heard various examples and owned Definitive BP8s when I was young, naive, and less proficient with power tools ) and identify the underlying physics which cause such issues. They get strained at moderate listening levels when the source material contains bass, where that's low bass you get doubling where you hear tones at twice the fundamental frequency due to distortion which although inaccurate isn't too bad, and the IM distortion happening to midrange frequencies is offensive.

These are some of the same reasons "audiophile" speaker demos are done with female vocalists and not orchestral music.

>What then shall we call all those 5.25" and 6.5" drivers that provide real bass extension down to 25-30 Hz?

Having more measurable bass extension at low to moderate listening levels than stand mounted monitors with similar drivers, good marketing, or fiction depending on your perspective.

>You also left out the part about how the back wave is managed, which accounts for why the Atlantic Technology AT-1 extends usable bass to 29 Hz from a pair of 5-1/4" woofers.

Assuming the 88cm^2 Sd and 3.5mm xmax of the 5.25" drivers I used in my example with driver output attenuated per the Stereophile measurements they'd reach their linear limits with program material calling for 94dB 1 meter from the speaker at 60Hz (one driver will net 83dB, two 89db, and the Stereophile nearfield measurement has the drivers -5dB down with the remainder coming from the port/transmission line hybriddrivers and 89dB (one will net 71dB, two 77, and they're 12dB down) at 30Hz.

As stated I like my jazz at a moderate less-than-live 85dBC SPL average which can yield peaks 105-107dB 3 feet from a speaker.

Pulling _Take Five_ from _Time Out_ off the CD and feeding the two channels through second order IIR Butterworth low-pass filters at 60Hz using GNU Octave I find right channel peaks at -10dB below the full-range peaks; or 95-97dB SPL.

The arithmetic explains why such speakers don't work well - up to 9dB shy is off by a factor of 8.

This is also an optimistic simplification. Distortion product SPL is more a function of total driver displacement although the fundamental output is dropping for a given excursion at lower frequencies so you might find only half the total linear excursion is clean.

>Next thing we'll need a disclaimer:
"No violence was committed in the generation of these low frequencies."

I'd like something quantitative such as output levels and distortion numbers for given input frequency + level combinations like independent testers are starting to do with sub-woofers plus a practical frame of reference: In our small and large listening rooms, we could average xx and yy dBC SPL with Sir Solti conducting the Chicago Symphony playing Beethoven 9. Elevator music averages xxdB, the typical middle aged male gets to yydB when his spouse is home, and the average audiophile prefers zzdB in a darkened room with a tumbler of single malt.

A driver is not characterized just by its size. Some 12 and 15 inch drivers have monster magnets and coils, and have a motor strength-to-cone-mass ratio as good as smaller drivers.

Long cone excursion leads to non-linear spring effect, and distortion. The less excursion the better, which leads to multiple large cone drivers, or, better yet, planars.

"Hoffman's Iron Law". First formulated back in the early 1960's by Anthony Hoffman (the H in KLH), Hoffman's Iron Law is a mathematical formula that was later refined by Thiele and Small, whose work now forms the basis of all modern loudspeaker design.
Hoffman's Iron Law states that the efficiency of a woofer system is directly proportional to its cabinet volume and the cube of its cutoff frequency (the lowest frequency it can usefully reproduce). The obvious implication is that to reduce the cutoff frequency by a factor of two, e.g. from 40 Hz to 20 Hz, while still retaining the same system efficiency, you need to increase the enclosure volume by 23=8 times! In other words, to reproduce ever lower frequencies at the same output level you need an extremely large box! This is why we see so many subwoofers or low eff multidriver towers. Using 5-7 in drivers. Larger woofers are better woofers, larger cabinets are more efficient and produce deeper bass with less thermo compression and Superior transient response. If one compromises size efficiency or range one can make a smaller design.

>04-30-12: Unsound
Some have argued that larger drivers will have greater energy storage, and correspondingly slower energy release.

They don't store energy and ring longer. Ringing at resonance is purely a function of driver + enclosure Q.

Some have argued that larger drivers will have greater energy storage, and correspondingly slower energy release.

Excellent insights from Drew, as usual. On the question that Bombaywalla raised about 3 db vs. 6 db, I believe that despite the apparent disparity you are both essentially correct.

For a given drive voltage, the total radiated acoustical power will be 3 db greater if there are two paralleled drivers as opposed to one (everything else being equal). Addition of the second driver will double both the amount of electrical power that is drawn and the amount of acoustical power that is radiated.

However, at a listening position that is approximately equidistant from the two drivers there will be a 6 db increase in SPL, as a result of constructive interference. At some other locations destructive interference will occur, resulting in low SPLs. Averaged over all space there will be a 3 db increase.

Best regards,
-- Al

04-29-12: Sounds_real_audio
>If 12" drivers were as fast and accurate as 4" drivers we wouldn't need any midrange drivers.

It's a function of system design. You're not going to beat a 12" midrange paired with a like sized wave guide for sound quality although the 30" high x 15" wide "stand mounted monitor" combining the two may be hard to get past your spouse.

Your brain hears timbre as a combination of the direct sound and what it identifies as reflections with the later coming off the speaker at extreme angles (> 70 degrees for the side walls depending on toe-in).

So to get a natural sound you need drivers to have similar behavior both on-axis and at those extreme angles.

Drivers also become increasingly directional as their dimensions grow large compared to sound wavelengths. By 900Hz a 12" driver has lost 3dB 45 degrees off-axis and by 1400Hz it's 6dB down.

At those frequencies a 1" tweeter on a flat baffle is omnidirectional.

The two won't match like the waveguide does. A 12cm cone or 5cm dome will match on a flat narrow baffle.

>04-29-12: Bombaywalla

> You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, and 6dB at the cross-over point to a sub-woofer....

>>Drew, why are you adding 6dB? It's power output, you should be adding 3dB in each case.

That's the sound increase you get when you run the drivers out to their physical limits although it'll take twice the power to get there as with a single driver. With the example 5.25" driver I listed 2.83V (1W into 8 Ohms or 2W into 4) will get you to xmax at 80Hz with one driver or a pair in parallel with power around 0.25W for a single driver and 0.5W for a pair (impedance increases as you approach resonance so power drops).

04-29-12: Tamule1
real bass comes from moving a large surface area gently -not a small surface violently . 6.5" is not a woofer size IMO

And you base this opinion on what?

What then shall we call all those 5.25" and 6.5" drivers that provide real bass extension down to 25-30 Hz?

You also left out the part about how the back wave is managed, which accounts for why the Atlantic Technology AT-1 extends usable bass to 29 Hz from a pair of 5-1/4" woofers.

Next thing we'll need a disclaimer:
"No violence was committed in the generation of these low frequencies."

It is cheaper to make a good small speaker with smallish drivers than to make an equally good larger speaker with large drivers. In addition to the cost of the drivers the cost of the speaker cabinet sharply increases with size. This wasn't necessarily the case back in the 70s before rigid, highly dampened cabinets became common. For cone based speakers if you want low distortion, high SPLs and response down below 40Hz large diameter woofers are the only way to go.

real bass comes from moving a large surface area gently -not a small surface violently . 6.5" is not a woofer size IMO

Back in the late 70s when i sold gear at tech hifi, bass drivers in most
speakers back then tended to range from 8 to 12 inches mostly with the
occasional 18. I levitated towards smaller drivers mostly for better sound
for most with their amps in their applications. Larger drivers were largely
inadequately built and under damped in many cases i heard resulting in a
muddier sound although typically with more lifelike impact. .

I think both amp and speaker technology has come a long way since and
that those issues can be adequately addressed these days in a variety of
ways, with both larger or smaller drivers, if the overall design is good.
Often though size, large or small, still matters though to many sound
quality being just one of the important considerations.

You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, and 6dB at the cross-over point to a sub-woofer....

Drew, why are you adding 6dB? It's power output, you should be adding 3dB in each case.

If 12" drivers were as fast and accurate as 4" drivers we wouldn't need any midrange drivers.

Drew, I agree more than disagree. Dispersion can definitely be modified with waveguides and phase plugs, and beaming can be mitigated with 1st order crossover slopes. Large diameter woofers can be just as fast as small ones if they have the magnet strength and cone stiffness.

Still, if the issue is why 5.25" and 6.5" woofers became the de facto standard over the 12" woofers of the '70s, it's probably a combination of manufacturing costs vs. performance and WAF. The old oversized bookshelf speakers of the '70s had no WAF whatsoever and the bass extension (especially of the JBL L100) wasn't so great either. The PSB Synchrony 2 is sexy with a narrow footprint and has flat response down to around 36 Hz.. 12" woofers can kick ass, but not in a 2.4 cu. ft. enclosure; a pair of 6.5" (a la ADS 810) do better in that same oversize bookshelf enclosure; many 12-inch woofers need about 4.7 cu. ft,, at which point you'll hear some *serious* bass.

>04-28-12: Johnnyb53
>More or less true, but bear in mind that a 12" woofer has *at least* twice the mass of a 9.5" woofer, and perhaps more because it will probably have a thicker cone to counteract breakup. All things being equal (which they're not), a 12" woofer has 3.5 times the mass of a 6.5" woofer, so by your reckoning it would need a magnet 3.5x as powerful.

The 12" driver's excursion and acceleration requirements are also scaled down to create a given frequency + SPL sound wave compared to the 6" by the ratio of their surface areas. Using the Peerless XLS12 and Seas L16RN-SL as examples it's less than 1/4 the distance and acceleration (483 cm^2 for the Peerless XLS 12 vs. 104 cm^2).

I don't have the magnet strength on the Peerless; although if you compare the Seas L26RO4Y 10" driver (BL 18, 1.1 Tesla in the gap, mms 173g, Sd 363 cm^2) to the L16RN-SL (BL 6.2, .88 Tesla, mms 14.8g, Sd 104 cm^2) with force / mass * Sd to make a meaningful comparison the big driver comes out ahead at 39.93 vs 37.44 for the small.

I could also point out that the smaller driver probably has a higher resonance which in turn means more group delay from the inherent minimum phase response of a driver+enclosure combination although all this would still remain irrelevant for purposes other than internet arguments based on inapplicable science.

Your brain needs a lot more than a fraction of a cycle to pick up a sound and assign direction, and where transients are of interest they split into low and high frequency components which are sent to the tweeter courtesy the cross-over network.

>Maybe, maybe not. However, speed aside, the the large driver still has a disadvantage in driver blending because its dispersion pattern turns into a beam at a lower frequency. A 12" cone starts beaming at 1100 Hz; a 6.5" at about 2K Hz. Guess which is easier to cross over to a tweeter at 2K Hz while maintaining uniform dispersion?

Those are arbitrary numbers (it's a continuum - you could say that the 12" driver is 6dB down at 45 degrees off axis by 1400Hz, or -3dB by 900Hz) although the 12" would work better provided that you didn't do anything contraindicated by decades of subjective listening impressions and research.

You can put the tweeter on a wave guide so the directivity matches the 12" driver at the cross-over point. This produces much smoother spectra in the side-wall first reflections which contribute to perceived timbre than the 6.5" driver with narrowing dispersion crossing to a 1" tweeter on a non-waveguide baffle which has near uniform radiation across its front hemisphere.

You can use a more conventional 3-way design with a relatively small cone or dome midrange between woofer and tweeter with a cross-over to the midrange at a few hundred hertz. This produces more nautral sounding side-wall/front-wall/ceiling reflections with improved vertical polars coming from reduced driver spacing compared to the 6.5" 2-way.

You can use a mid-tweeter that accomodates a very low cross-over point. For instance the 1.6" Aura "full range" driver does well at the sort of moderate SPLs a 6" mid-bass limits you to with a 1KHz cross-over (the big voice coil does roll-off at high frequencies, although most of us can't hear that and where we can it can be compensated for in an active cross-over).

Of course traditional 2-way cone and dome speakers aren't worth considering where your first priority is sound quality especially where you do not limit yourself to simple music at background listening levels. They vary from each other in how their mediocrity comes out (inaccurate timbre, low SPL capability, limited bass extension) but as a listener you're better off skipping the genre and building or buying something excellent. OTOH as a speaker manufacturer this is OK because people buy based on appearance and price and as a competent cabinet maker you can make building such speakers a full-time job. Cabinet/furniture makers with more refined ears do use low cross-over points with extra-beefy tweeters like the Seas Millenium for better directivity matches at the cross-over point so the results needn't as bad as they can be.

There's a lot of latitude in how you get to "excellent" with the many possibilities producing sound more similar than different. You can use acoustically small cones and domes on acoustically small baffles with uniformly broad dispersion like the B&W Nautilus or Linkwitz Pluto (still somewhat dynamically limited). Wave guides work well to bring the high frequency dispersion from acoustically small drivers in line with the lower midrange for moderate dispersion as in the Revel Salon 2 or more directivity like the Gedlee designs or Danley Synergy Horns. Acoustically small dipoles work great where cancellation from the sonic short circuit between front and rear waves brings directivity at lower frequencies in line with higher for each driver like John Krevosky's NaO Note or Siegfried Linkwitz's Orion.

FWIW, in 2004 Sean Olive produced a pair of numerical definitions for "excellent" which correlate exceedingly well with blind subjective speaker rankings. Monotonic off-axis response curves and bass extension are significant where physics dictate conventional 2-way cone and dome speakers lack at least one.

Any one interested in sound reproduction owes it to themselves to read _Sound Reproduction: Loudspeakers and Rooms_ by Floyd Toole where chapter 20 (Closing the Loop: Predicting Listener Preferences from Measurements) is especially relevant. While not "light reading" at 500 pages it's a lot more digestible and affordable than the decades of JAES and other papers it summarizes.

For more conventional designs on more finite budgets you can do better with more less expensive drivers than fewer pricier ones, especially where the speaker maker adjusts the cross-over to compensate for the manufacturing variations (Dunlavy did this) you get at lower price points since polar response has a lot more to do with how close you get to "excellent" than other metrics like on-axis response flatness and stored energy. It's nice to have a scientific explanation for what you hear or suggestion on what to audition next.

If you want a thin spouse-friendly cabinet at the same time you can do it with a side-mounted woofer or W-frame dipole.

(You can tell I'm a bit cranky - I spent my day periodically staring at the boards which will become my next two pairs of cabinets contemplating which grain and figure combinations will look best where instead of making sawdust).

Driver size has nothing to do with "fast" or "slow". Twice the motor strength will accelerate double the mass as a smaller motor/mass combination whether we're talking about vehicles or drivers.

More or less true, but bear in mind that a 12" woofer has *at least* twice the mass of a 9.5" woofer, and perhaps more because it will probably have a thicker cone to counteract breakup. All things being equal (which they're not), a 12" woofer has 3.5 times the mass of a 6.5" woofer, so by your reckoning it would need a magnet 3.5x as powerful.

>Bigger drivers can still have that old school sound. Bigger drivers move more air but tend not to be as accurate and have trouble keeping up with a 5" midrange so you can loose cohesiveness.

Nope.

Maybe, maybe not. However, speed aside, the the large driver still has a disadvantage in driver blending because its dispersion pattern turns into a beam at a lower frequency. A 12" cone starts beaming at 1100 Hz; a 6.5" at about 2K Hz. Guess which is easier to cross over to a tweeter at 2K Hz while maintaining uniform dispersion?

If you are interested in dynamic speaker drivers and technology, read up on Walsh drivers for something completely different, as they used to say.

Thanks, folks. Once again I came to realize to helpful the audiogon can be. A lot of information to think over, "sounds" similar to my thoughts very often. Yes, I am not 15 any more, for the last 40 years. I remember back then in Russia the speakers from Estonia were popular, I can't recall the sound of course, been a long time, but I was really impressed. Then routes of life displaced all, was able to start getting "back in shape" a year ago and guess what - from all out there I bought Audes 027 made in Estonia :-)
Best Regards to all

It turns out the large woofers of the '60s and '70s were counterproductive to bass extension, driver blending, and the distortion of cone breakup.

Smaller drivers solve many problems in dispersion and driver integration. A 12" woofer starts beaming (i.e., no dispersion to speak of) at 1100 Hz. A 6.5" driver doesn't beam until about 2100 Hz, making it much easier to blend with a tweeter. A 6.5" driver will also accelerate and stop faster than a 12' one, and it's easier to make a 6.5" speaker that won't have significant cone breakup at full excursion than a 12" one.

Great strides have been made in cone excursion. A 6.5" driver with 1/2" excursion can displace more air than a 12" driver with 1/8" excursion (typical of a '70s woofer). Twin 5.25" woofers with 1/2" excursion have 50% more potential displacement than a 12" with 1/8" excursion.

Then, as was mentioned before, you get better dispersion and therefore better in-room power response with a narrow baffle than a wide one. So all in all, smaller woofers make for better overall speaker systems--better imaging, better dispersion, faster response, higher crossover points without suckouts. The Atlantic Technology AT-1 manages to get <30Hz bass extension from an MTM arrangement with two 5-1/4" woofers and unique cabinet loading.

Avs9 writes:
>But nowdays I am seing 6 inch drivers stated as "bass". Just curious how well those perform

They provide enough mid-bass output to meet a woofer for serious listening or a sub-woofer at polite but not realistic levels suitable for hold and elevator music.

>or in another words what is the secret behind those if they really can perform at the same level as the 12 inch ones?

They don't.

Output at the maximum linear excursion into full space for various representative drivers at 3 feet is as follows at 120, 80, 40, and 20Hz. Many drivers have less excursion and lower output. Subtract 3-5dB for living room dimensions and more for a larger space for the SPL at your listening position

You can add 6dB for a floor mounted woofer (as in many 3-ways), 6dB if there are a pair of bass drivers, and 6dB at the cross-over point to a sub-woofer.

Size Driver Sd (cm^2) x xmax (mm) 120Hz 80Hz 40Hz 20Hz
4 1/2" Seas W12CY001 50 x 3 89dB 82dB 70dB 58dB
5 1/4" Peerless 830873 88 x 3.5 95dB 88dB 76dB 64dB
6 1/4" Seas L16RN-SL 104 x 6 101dB 94dB 82dB 70dB
7" Seas W18EX001 126 x 5 102dB 95dB 83dB 71dB
8.5" Seas W22EX001 220 x 5 106dB 99dB 87dB 75dB
10" Peerless 830452 352 x 12.5 118dB 111dB 99dB 87dB
12" Peerless 830500 483 x 12.5 121dB 114dB 102dB 90dB

As a frame of reference I like my jazz at less than live 85dBC average levels which makes for peaks on good recordings with 20dB of dynamic range of 105-107dB at the speakers. The scale is logarithmic, so at 80Hz that's more than 10X what you can squeeze out of a 6" driver and 100X at 40Hz.

>And another question which I guess is too simple and too basic around here that's why I couldn't find some point to point answer - when we speak about sensitivity - would that be a true statement to say that higher level (say 92-95 db) will allow to extract "fuller" sound spectr at a lower level of volume?

Not with equal frequency response although design considerations mean you might get a boost in higher frequency bass output so it sounds that way.

Efficiency is at best inversely proportional to the cube of the low frequency cut-off and proportional to the size of the enclosure. To make a speaker play one octave lower using the same bass alignment (sealed, ported, band-pass) it needs to be 8X as big to maintain the same efficiency; or conversely at a given box size a speaker with one octave less bass extension can be 9dB more efficient (or 3dB for 1/3 octave).

When people build speakers with limited bass extension they often boost the output before the roll-off starts so there's the illusion of low bass and since higher frequencies have a lower threshold of hearing you can notice the extra bass at listening levels where you couldn't hear the real thing since our threshold of hearing and equal loudness curves require higher SPLs at lower frequencies.

Small and efficient speakers can't have low bass but are often built this way although that doesn't mean all efficient speakers are.

04-27-12
Responses
04-28-12: Jmcgrogan2
Smaller bass drivers have gained in popularity for two reasons.
>B) they may not go quite as deep, but the bass will be tighter.

Apart from physical limitations on the displacement needed to achieve a given SPL driver size has no bearing on bass quality.

>04-28-12: Sounds_real_audio
Boy you are old. Listening to music in the 70s. Smaller drivers are trendy because they go fast.

Driver size has nothing to do with "fast" or "slow". Twice the motor strength will accelerate double the mass as a smaller motor/mass combination whether we're talking about vehicles or drivers.

Smaller drivers are trendy because they're less expensive (which allows for bigger profits) and not as offensive to women who are more likely to contribute to the family pot and have a say in how it's spent than in the 1970s and before.

People retiring their tube gear in favor of transistors have also made smaller and necessarily less efficient enclosures practical. With 80 transistor Watts you can drive an enclosure with the same low frequency cut-off to the same SPL you could a speaker 8X the size with just 10 tube Watts.

>Bigger drivers can still have that old school sound. Bigger drivers move more air but tend not to be as accurate and have trouble keeping up with a 5" midrange so you can loose cohesiveness.

Nope.

04-28-12: Ngjockey
>Although bass extension is generally less with smaller drivers, some of the dynamics can be equivalent or even superior with multiple drivers.

Right. Looking at the table I provided you'll note that with 10 6" drivers you can match the headroom for dynamic peaks you get with a single 12" driver. Where you only get 2-4 6" drivers the smaller drivers can fall short.

Bigger isn't always better. I keep telling myself that.

For example, there are 12" drivers that sacrifice bass extension for efficiency and midrange performance and there are 6.5" drivers that do the opposite. A lot of the difference since the 70's is how they match drivers to the cabinet and control resonance.

Fact is that "hifi" stereo is a small fraction of the sales of home theatre and LFE subwoofers has become the defacto standard. There is, simply, very little demand for big speakers and the assosciated shipping costs.

Although bass extension is generally less with smaller drivers, some of the dynamics can be equivalent or even superior with multiple drivers.

1) size of the driver is related to efficiency in producing deepest bass. But bigger drivers become problematic in transient response. Sub woofer manufacturers like REL and Velodyne make money selling a well tuned optimized home use choice to supplement less than full range speakers for the lowest bass
2) the ear is most sensitive to high frequencies. When you reduce volume below the original performance db levels the lower the frequency, the more you will feel something is missing (fullness). Inexpensive gear oft had an equalizer feature (loudness) to compensate and avoid ill will from neighbors. Audiophiles don't compromise/take it for granted music is to be played at original volume.

Smaller bass drivers have gained in popularity for two reasons.
A) They allow the speaker designer to make the speakers smaller, so they usually "image" better.
B) they may not go quite as deep, but the bass will be tighter.

AFAIK, Sensitivity has nothing to do with the sound being "fuller". Yes, you may need to turn your amp up a bit more for less sensitive speaker to play at the same sound level, but whatever listening level you are at, 80 db, 85 db, is still 80 or 85 db no matter what the sensitivity rating of the speaker is.

Boy you are old. Listening to music in the 70s. Smaller drivers are trendy because they go fast. Bigger drivers can still have that old school sound. Bigger drivers move more air but tend not to be as accurate and have trouble keeping up with a 5" midrange so you can loose cohesiveness.

More efficient speakers are not necessarily toned to sound full at low volumes. My experience is that more forward sounding speakers sound better at low volume. Some very forward sounding speakers sound best at no volume.

The opinions expressed above are my own.