Does Size Matter?

[TLS Guy]

Speaker size definitely makes a difference, because of something we call "the laws of physics". Whether that difference matters is another question, whose answer largely depends on what matters to you.

Please enlighten me on the law of physics which says what you claim above is related to driver size.

 

[JerryLove]

bigger speakers = better sounds period. Bose did the opposite though with their ads in the 80s . Bigger sounds coming from their tiny speakers they claimed.

Really? Let's put some Pioneer or CV 18" floorstanders against, say, a B&W 802D.

 

[WVEAS]

This is what I'm getting at:

5. You saved money by getting two compact speakers you thought would be just fine to fill your 25- x 20-foot cathedral-ceiling living room with high-level sound. But they sound strained and edgy when you turn up the volume .

A speaker is a kind of electromagnetic air pump, and a modest single woofer and tweeter can't be expected to fill a big room with wide-range sound at high listening levels. Too many shoppers expect a "bookshelf" speaker to produce deep, resonant bass. Unfortunately, the laws of physics dictate otherwise. Sure you can get listenable pleasant bass to about 50 or 40 Hz from a shoebox-size enclosure, but if you want the resonant, deep and satisfying sounds that a big rock band or orchestra makes or the deep rumbling of movie soundtracks, you must get a subwoofer or floorstanding speakers--or both!

 

[highfigh]

Using small speakers in a large room is very similar to taking them outside. They can't fill the space and most of the sound either needs to be projected toward a specific area or they just don't move enough air to make it sound real. Sound is acoustic energy and small speakers in a medium to large room just can't produce enough in the range that humans need to hear. Horn-loaded is another story.

 

[TLS Guy]

This is what I'm getting at:

The laws of physics do not dictate much about driver size, but definitely favor large enclosure size.

 

[Ed Seedhouse]

Please enlighten me on the law of physics which says what you claim above is related to driver size.

Well, as it applies to loudspeakers, if bass flatness and extension are kept the same, a smaller loudspeaker must be less efficient than a larger one. Or if efficiency and flatness are kept the same then a smaller speaker must have less extension than a larger one. And this is a straightforward consequence of the laws of physics.

 

[TLS Guy]

Well, as it applies to loudspeakers, if bass flatness and extension are kept the same, a smaller loudspeaker must be less efficient than a larger one. Or if efficiency and flatness are kept the same then a smaller speaker must have less extension than a larger one. And this is a straightforward consequence of the laws of physics.

That is not so, unless you confine yourself to a sealed or IB speaker where there is no acoustic transformation. Also gap flux density is a large determinant of driver efficiency, but not bass extension.

A small driver like a Lowther in a back loaded horn has far greater efficiency then almost any speaker I can think of with good bass extension. As I pointed out before Donald Chave filled St. Paul's cathedral with four six inch cones, when the big speaker boys had failed miserably.

A loudspeaker cone by itself is a very inefficient way to convert electrical energy into sound energy. However load the speaker with a horn or pipe, especially a horn and the situation improves remarkably. To the extent that a Lowther will fill a room with 100 mw.

 

[Ed Seedhouse]

That is not so, unless you confine yourself to a sealed or IB speaker where there is no acoustic transformation. Also gap flux density is a large determinant of driver efficiency, but not bass extension.

Nope. It is so of all speakers, whatever the design. Note the words I used carefully, please. I mentioned bass flatness, as I recall. One can play around with the rolloff slopes, but then one is altering the bass frequency response.

A reflex design, which rolls off the bass at 18 db per octave rather than 12 db, can have a higher efficiency for the same size box as a sealed design, but at the expense of a steeper rolloff and less ultimate extension. Or it can have a lower -3db point for the same efficiency. You can play around with the slopes, but leaving the rolloff slope the same then the size of the box alters either the allowable efficiency for the same extension, or the bass extension for the same efficiency.

Given two boxes of the same basic design and the same frequency response the larger one will always be more efficient, period, as a consequence of the laws of physics.

Contrawise, given two boxes of the same bass rolloff slopes, and the same size, the more efficient system will have a higher bass cutoff as a consequence of the laws of physics.

Flux density is one of the determining factors of system Q. If all else is held equal, then increasing the flux density will indeed alter Q factor of the fundamental resonance, changing the bass slope and consequently the bass response, higher flux density resulting in a higher bass cutoff.

Get yourself a book on loudspeaker design and look it up for yourself. Or read this link on Hoffman's Iron Law.

As wikipedia states "It is not possible to combine high efficiency (especially at low frequencies) with compact enclosure size and adequate low frequency response. One can, more or less, choose only two of the three parameters when designing a speaker system. So, for example, if extended low-frequency performance and small box size are important, one must accept low efficiency.[26] This rule of thumb is sometimes called Hoffman's Iron Law (after J.A. Hoffman, the "H" in KLH).[27]"

 

[TLS Guy]

Nope. It is so of all speakers, whatever the design. Note the words I used carefully, please. I mentioned bass flatness, as I recall. One can play around with the rolloff slopes, but then one is altering the bass frequency response.

A reflex design, which rolls off the bass at 18 db per octave rather than 12 db, can have a higher efficiency for the same size box as a sealed design, but at the expense of a steeper rolloff and less ultimate extension. Or it can have a lower -3db point for the same efficiency. You can play around with the slopes, but leaving the rolloff slope the same then the size of the box alters either the allowable efficiency for the same extension, or the bass extension for the same efficiency.

Given two boxes of the same basic design and the same frequency response the larger one will always be more efficient, period, as a consequence of the laws of physics.

Contrawise, given two boxes of the same bass rolloff slopes, and the same size, the more efficient system will have a higher bass cutoff as a consequence of the laws of physics.

Flux density is one of the determining factors of system Q. If all else is held equal, then increasing the flux density will indeed alter Q factor of the fundamental resonance, changing the bass slope and consequently the bass response, higher flux density resulting in a higher bass cutoff.

Get yourself a book on loudspeaker design and look it up for yourself. Or read this link on Hoffman's Iron Law.

As wikipedia states "It is not possible to combine high efficiency (especially at low frequencies) with compact enclosure size and adequate low frequency response. One can, more or less, choose only two of the three parameters when designing a speaker system. So, for example, if extended low-frequency performance and small box size are important, one must accept low efficiency.[26] This rule of thumb is sometimes called Hoffman's Iron Law (after J.A. Hoffman, the "H" in KLH).[27]"

That is more or less true for sealed enclosures and ported designs. However the efficiency bass cut off problem is related to flux density. There is an inverse relationship between flux density and bass extension. However a horn is such a good acoustic transformer a high flux density (therefore high efficiency) can be used. A horn is so efficient it will pull up the bass response and flatten the response, even with a small driver.

What you are citing above does not apply to horns. The design of horns has until recently been empiric. William Fitz Maurice has developed a plausible mathematical model for horn design. However it is very advanced math and not simple like calculations for sealed or ported enclosures.

Pipes are somewhere in between in complexity. By the way most ported alignments are QB4 and roll off 24 db per octave. An 18db roll off would be a QB3.

 

[Ed Seedhouse]

What you are citing above does not apply to horns.

Yes, it most certainly does. A LF horn is subject to the exact same constraints. Hardly a surprise since they are just as subject to the laws of physics as anything else. And there are NO exceptions to the laws of physics.

Notice for example how very large the Klipschorn LF section is. That huge box has in fact a rather high LF cutoff compared to much smaller and over all far less efficient acoustic suspension designs. An acoustic suspension design of the 1950's, the AR 1, was far less efficient than the K horn in the upper bass, but actually a good deal more efficient at very low frequencies like 20hz. The AR could produce an audible 20 HZ signal, whereas the K horn, much more efficient at 60 HZ was just gone at 20Hz.

This is actually because the K horn is so efficient that for the box size it cannot produce optimum base. An acoustic suspension or reflex design of the same size could go far lower and with much less distortion, unless they made the magnet so huge that it, too, was overly efficient for optimal bass.

That is not an insult to Paul Klipsch, since when he designed that system the relationships discussed here were not known widely.

Notice also, by the way, that "modern" full range horn systems uniformly do not use horns for the deep bass. They use big reflex boxes, and for a good reason too. A horn large enough to keep it's efficiency levels down to 20hz simply won't fit in a normal house.

Show me a horn that is flat to 20 hz and I will show you a horn that sits outside a house, not inside it.

The design of horns has until recently been empiric.

This is false so far as bass is concerned. The LF characteristics of an exponential horn have been known, and the equations that describe them have been known, since the 1930's.

Pipes are somewhere in between in complexity

More nonsense. Actually they are quite simple, as organ designers have known for centuries.

 

[GirgleMirt]

As I pointed out before Donald Chave filled St. Paul's cathedral with four six inch cones, when the big speaker boys had failed miserably.

Imagine the results with eight six inch cones, or four 8 inch cones!!! Horns are probably no exception to the OP's friend's claims. Add more horns, or use bigger drivers in the same horns (well not exact horns obviously), and you'll get more SPL.

Adding horns to the equation is similar to adding a 'submerged in water' condition to a 3 inch woofer reproducing better bass than a 15 woofer... All conditions being equal, adding more drivers or bigger drivers will help max SPL. With horns, to invalidate the premise, you'd have to have horns on both side and demonstrating that adding more drivers or bigger drivers wouldn't improve SPL, which isn't the case... Horn is the cabinet here... Obviously if you'd add a 2nd woofer, it would also have to be in a cabinet... Or have a larger cabinet... But horns do not break the rule.

 

[Coolzrock]

Well it does matter, but still some 5" can beat 10" if they have proper quality and power. --- REMEMBER : MY OPINION.

 

[Ed Seedhouse]

Well it does matter, but still some 5" can beat 10" if they have proper quality and power. --- REMEMBER : MY OPINION.

A well designed small speaker can be better than a poorly designed big speaker, of course. Nor is bass extension and quality the only important factor.

But, in the bass, size makes a difference, period. It might well be that we will prefer the particular set of compromises chosen by the designer particular small speaker better than the compromises chosen by the designer for a bigger speaker.

But the fact remains that if a large speaker has the same bass extension and rolloff of a small speaker, then the large speaker is, ipso facto, the more efficient speaker.

If we have an amplifier of sufficient power and quality these differences may not matter at all - we simply twist the volume knob a bit higher for the small one. But there is a difference nevertheless.

As I originally said, differing sizes mean inescapable differences in performance, but the differences, while real, might not matter to us.