advantages of 8" vs 6" speaker

[Wombat]

Especially with organ music. I have a sub and 4 in wall speakers for less focused listening, and another system with a pair of big Focal Aria 948 floorstanding speakers and for organ, I usually run both systems so I can really rattle everything with full dynamic range.

What do we call distortion due to rattle?

I love the feeling of acoustic power that large drivers/horns give with pipe organs.

 

[Plcamp]

TOTALLY CURIOUS about the PAP Trio Do you have the horns or Voxative?

Neither (and I am not satisfied with that). I have a Tangband W8-1808.

I no longer believe fullrangers are suitable for open baffles, because the excursion they require to enable the woofers to low pass at 200 hz is too high. I concluded the Tangband can sound great but it needs acoustic cross way up at about 700 hz.

I want to find a new solution, and suspect I will settle on an approx 10” coaxial

But...the bass on twin 15” woofers is really great.

 

[Plcamp]

What do we call distortion due to rattle?

I love the feeling of acoustic power that large drivers/horns give with pipe organs.

Rattle and vibration are pretty severe limitations for my PAP trios...I think it is less than optimum to mount the fullrange to a baffle that’s got twin 15 woofers pumping bass energy. So I created a simple magnet mount for the fullrange such that it can poke through but not touch the baffle. I want to treat the baffle as a sort of waveguide, and not a driver mounting structure as well.

 

[Spocko]

Neither (and I am not satisfied with that). I have a Tangband W8-1808.

I no longer believe fullrangers are suitable for open baffles, because the excursion they require to enable the woofers to low pass at 200 hz is too high. I concluded the Tangband can sound great but it needs acoustic cross way up at about 700 hz.

I want to find a new solution, and suspect I will settle on an approx 10” coaxial

But...the bass on twin 15” woofers is really great.

Yes, I love that you can have the Pass active crossover so you can have great flexibility in drivers to match the amazing dual 15" woofers! I hate to say it, but the Voxative field coil coax looks sooo cool, but I know they probably don't sound anywhere close to the cost it commands.

 

[Plcamp]

Yes, I love that you can have the Pass active crossover so you can have great flexibility in drivers to match the amazing dual 15" woofers! I hate to say it, but the Voxative field coil coax looks sooo cool, but I know they probably don't sound anywhere close to the cost it commands.

They (the woofers) load the room very differently than closed box drivers. The room is less of a factor. But I still used a closed box sub under 50 hz.

way off topic here...sorry

 

[LTig]

What do we call distortion due to rattle?

RHD

 

[Helicopter]

RHD

Distortion with organ is like 5% as bad as with something like acoustic guitar or female vocals... let it happen.

 

[MattHooper]

Sound pressure level is really the ratio of the peak pressure to the partial vacuum between sound waves. To create those pressure fronts, you have to displace air. The more air you can displace at a given frequency, the louder the result.

The amount of air that a driver can displace involves three factors: excursion (how far it moves), area, and linearity. (Sensitivity is another feature--how far it moves at a given voltage, but low-sensitivity speakers can still play low and loud, they just need a bigger amp.) Linearity limits how high the frequency can be at a given excursion before the cone starts to get non-linear waves running through it (called "cone breakup").

Larger woofers are more subject to cone breakup at less-high frequencies, all else equal. But they never are equal--larger cones are designed to be stiffer, or they are crossed over at lower frequencies, which minimizes breakup (at least in a well-designed speaker).

When a driver runs out of excursion, the compliance pushes back on the motion, which has the effect of compressing the peaks. Or, the voice coil bangs against the back of the frame, which...is bad.

More area means the SPL requires less excursion, or the same excursion can move more air.

So, bigger drivers can play low frequencies louder, again all else equal. But, again, all else is not usually equal. My ancient Advents have 10" woofers (nominally) with a high excursion design, using soft foam surrounds. Advent controlled that motion by sealing the cabinet to damp the motion of the woofers. That makes them less efficient, but they have good bass extension and can play loud enough so that the mid-tweeter runs out of capability before the woofer does.

My new (to me) Revel Concerta F12's have 8" woofers, but it has two of them. Two 8" woofer nominally have 50% more area than one 10" woofer, so points to Revel. Revel also used a tuned port, which acoustically damps the speaker motion down to the port tuning frequency (where the woofer is almost standing still but the pressure waves are coming from the port), which is 33 Hz for those speakers. Below that, and the woofers start to run out of excursion, because they no longer have the port tuning to help control it. They make bass just as good as do the Advents, and they do it at (much) lower distortion. In fact, they make bass as well as two Advents at any given level of overall speaker performance (which on the Advents is mostly constrained by the mid-tweeter).

I specifically wanted the older F12's rather than their replacements which use 6" woofers, simply because I wanted the bass extension that benefits from area and excursion, and that low port tuning frequency. The smaller drivers require a higher port frequency to help keep the woofers from running out of excursion when playing too low and too loud. Small woofers run out at higher frequencies. The port frequency of my Pioneer bookshelf speakers, which have 4" woofers, is 72 Hz, and they don't make much bass below that.

TL;DR: It isn't just the size of the woofer, it's also the overall design of the speaker and the driver. But I think bigger (or more of them) is better if you want low and loud, unless you add a subwoofer to the system. Getting really good bass from small woofers is difficult. Most "affordable" new speakers are small because they target home-theater applications where they can count on the presence of a subwoofer. Even most speakers with 8" woofers will work less hard if a subwoofer is available, but I for one prefer not to use a subwoofer on a stereo for playing music. (And the subwoofer has to do more than the speaker--some small subs don't go any lower than these F12's.)

Rick "size isn't everything--but it's something" Denney

That was a great post!

I don't have the technical chops to give any real input, but some of that seems to match my subjective impressions.

Among the speakers I'm using now are the Joseph Audio Perspectives. The JA speakers, Pulsar and Perspective, have a reputation for surprising everyone with the depth, quantity and quality of bass they put out for such small, slim speakers and for the Perspectives, just a couple of 5.5" drivers per speaker. They are SEAS long throw drivers, so an attempt to get good displacement as I understand it. As John Atkinson said when reviewing them "I was astonished by how much clean, low-frequency energy four 5.5" woofers could pump into my room. "

I'm continually amazed at how massive these little speakers can sound, and just how deep and punchy the bass can be...and I'm used to lots of much larger floor standing speakers.

That said, where I feel I hear the limits is when playing really loud, for instance really cranking up the sound to listen from other rooms in the house. There seems to be a point at which the speaker doesn't seem to get much louder, or maybe the bass more powerful. (The sound of the speaker doesn't get harsh at all, it remains really smooth, it just seems to reach the sense of impact starting to lose pace with the volume control).

In contrast, the Thiel 2.7s I have which are 3 ways with an 8" woofer, seem to have a bit more solid bass when louder and seem to go louder without strain. The bigger Thiel 3.7s I owned, 10" woofer, seemed to be even less restrained....I could just keep cranking it up and they only sounded more massive.

So the Joseph speakers with the smaller 5.5" woofers do frankly amazing bass and under most conditions, don't even seem to have to apologize for their size. But I can find their limits.

One set of speakers that has intrigued me were the Devore O/96 speakers, a two-way using a 10" woofer and a tweeter, in a wide-baffle cabinet.
Spec'd down to 25Hz. They sounded just massive for their size, with very deep "big" bass, really powerful. I never did push them in auditions as I have the Joseph speakers at home, and I wonder what the design implies - two 10" SEAS woofer displacement on the Devore vs four 5.5" woofers large excursion design on the Josephs. Are there calculations-on-the-back-of-a-napkin that suggest one should be able to produce more, cleaner or more powerful bass than the other design?

 

[rdenney]

Multiway speakers run out first in one driver or the other. Those Seas drivers must have very long voice coils, some kind of limiting device (like a copper sleeve) to keep them linear through their very long throw, and wide, pliable surrounds and spiders. The trick to long throw, it seems to me, is resistance from the compliance that matches the force applied by the motor. The voice coil loses motor power as it extends out of the magnetic field, etc., etc. It's hard to make small drivers really maintain that kind of linearity at large displacements. It's much easier just to make the woofers bigger.

But back to driver balance. My Advents work by using a tweeter that Kloss designed to have both high frequency and mid-range power, with a center dome surrounded by a cone, which is surrounded by the (minimal) compliance. This is the (in)famous fried-egg tweeter. He found that at low frequencies, the whole shape would displace air, and at higher frequencies, only the center dome would radiate effectively, which created a driver that could go low. But the frequency range of the driver was still a bit constrained on the high end. He crossed it over with the excellent Advent woofer at 800 Hz or thereabouts (it's a simple LCR single-order crossover so the crossover region has a lot of overlap). But the mid-tweeter would run out of motor power before the woofer would, and start to distort (and overheat). That's why replacing the fried-egg with a wide-range, wide-dispersion horn (so-called "econowave") is a popular modification. In a three-way speaker, that Advent woofer would have been even more famous (if that's possible), except that they would have had to charge more for them, and they wouldn't have drawn in so many attentive college kids during the golden age of stereos (like me).

My new Revel F12's start to distort in the mid-range driver first. When the Canadian NRC tested it at 100 dB SPL (at two meters, in an anechoic chamber), the speaker showed the beginnings of a loss of linearity at right around 1 KHz--the output signal dropped a couple of dB normalized to the response at 70 dB. The tweeter also started to lose a bit in the top octave. But the woofers aren't losing much. This is compression caused by the cone suspension of the mid-range driver running out of compliance.

The very expensive and highly regarded Wilson WATT/Puppy starts to lose linearity at 5 Khz first (the NRC only tested it to 95 dB). The Martin Logan Motion 60XTI, which is similar to the F12 in configuration and retail price, also started to compress in the mid-range first (though at a lower SPL). But the ML was very hot in the treble--the ribbon tweeter was overpowering the mid-range on axis, but greatly diminished off-axis. The Revel showed a similar shape on and off-axis, which is what makes the Revel really excellent (as an expression of the Revel/Harman/Toole/Voecker philosophy). The NRC didn't push either as hard as they did the Revel, based apparently on their opinion that they were already seeing limitations. (Testing linearity at 100 dB is like running at an average of 106 dB at one meter, which would be 108-110 dB SPL peaks with even moderately dynamic music--LOUD.)

We focus on woofers, but mid-range drivers are even more important to the sound of a speaker, particularly when played loudly. Small two-way speakers can do well here, because small woofers can be crossed at higher frequencies and do real mid-range duty, rather than asking the tweeters to go low (as with the Advents). This brings us back on topic (from a great distance): If we demand powerful low bass from small speakers, we need to bring our checkbook, or we will probably find compromises elsewhere, such as a hole in the mid-range, a rolled-off top end, or a constrained maximum output. For small speakers made for use in the near field, the reduced maximum output is the usual (and acceptable) victim.

Rick "with apologies to the OP" Denney

 

[restorer-john]

Two 8" woofer nominally have 50% more area than one 10" woofer

Mmm. Not so sure about that. 30% perhaps at the most.

 

[dfuller]

Mmm. Not so sure about that. 30% perhaps at the most.

28%, ballpark.

 

[Doodski]

Mmm. Not so sure about that. 30% perhaps at the most.

I don't consider even a 10"er to be all that rowdy of a woofer. A 18"er is thumpy for sure.

 

[restorer-john]

28%, ballpark.

Exactly. I was being generous. Consider also larger diameter speakers have larger roll surrounds reducing the effective piston area even more and it drops even lower.

 

[restorer-john]

Woofers start at 12". Anything smaller is a midrange.

 

[dfuller]

Way I see it, there are sort of two solutions to "more bottom end":
1, more surface area. This is sort of how bass reflex systems work, they essentially let the rear side of the cone actually, well, do something.
2, more excursion. Long throw sort of does the same thing, but you start having to worry about distortion more.

Woofers start at 12". Anything smaller is a midrange.

I've got 4 8" drivers in 2 speakers with +/- 9.5mm xmax each, you think those count?

 

[restorer-john]

I've got 4 8" drivers in 2 speakers with +/- 9.5mm xmax each, you think those count?

A good start.

 

[rdenney]

Mmm. Not so sure about that. 30% perhaps at the most.

I was just going on nominal diameter. R^2 a 10" circle is about 50% more than for an 8" circle (and I was comparing Advents to my new-to-me Revels). Of course, that's not what the OP was asking about, but that's where my mind was

But a 6" circle is only 56% of an 8" circle, so the difference is larger than between an 8 and a 10.

The effective radiating surface is, of course, less.

Well, damn. I said before that two 8" drivers have 50% more area than one 10" cone, not that 10 was more than 8 or 8 more than 6. The area of two nominal 8" cones is around 100 square inches, and one 10" cone is nominally 77 square inches. There's John's 30%. Sheesh. I really do read well, when I bother. Sigh.

Rick "too lazy to look up or measure the actual cone diameters, but the Advent is a true 10" cone in a 12" basket" Denney

 

[restorer-john]

All good Rick "πr²" Denney.

 

[MattHooper]

This brings us back on topic (from a great distance): If we demand powerful low bass from small speakers, we need to bring our checkbook, or we will probably find compromises elsewhere, such as a hole in the mid-range, a rolled-off top end, or a constrained maximum output.

Oh yeah. I had to bring out my pocket book
I believe the Joseph Perspectives use SEAS most expensive mid drivers. (FWIW).

I was just reading about someone who replaced big JBL L220's, which use a 14 inch woofer with a 15 inch passive radiator, with the Joseph Perspective speakers and the owner still managed to be blown away by the bass of the Perspectives and their lil' 5.5" drivers.

Still, all my intuitions expect more powerful bass from bigger drivers.

 

[notabenem]

Woofers start at 12". Anything smaller is a midrange.

Any advice where to look for 1) good sounding, 2) >=12" 'woofers' with a 3) reasonable budget? I know. You'll tell me I have to pick two.