what is the driver size mitch?
4 inches.
So equivalent of 2.5 x 15" woofers of surface area.
I wonder what the crossover setup is? Are the drivers split into frequency bands?
whatever the impedimentā¦Iāve always said, "Where thereās a will, thereās a way OUT!
There is only a single capacitor in each speaker box
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Oh yeah thereās a way out but it would probably cost as much as a new piece of hifi! I am in North Queensland Australia.
I live about 200 meters from this beachā¦
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That table is the areas of circles of said size, and not really relevant in comparing equivalent number of drivers, though resultantcomparative figure may not be far wrong in many instances. The piston (cone) area of woofers is quite a bit less than the driver overall diameter, and it is that you really need to compare if you are trying to assess how many of a given small size is equivalent cone area to a single larger size. The relative cone size of different size drivers varies between manufacturers and sometimes between different models of nominally the same size from a given manufacturer. If you look up driver details it is usually given among the Thiel-Small data, denoted Sd. E.g. just picking from one catalogue to hand, the Volt RV3143 12ā radial bass driver has Sd=479cm2 (75in2) Their 6.5ā BM165.1 driver has Sd=154cm2 (24in2) so using three of the 6.5ā drivers the cones would have fractionally further than that of one 12ā for the same sound level.
Interestingly the effective moving masses of these specific two different drivers differ by almost exactly the same ratio as the piston diameters, so the same mass is moving the same distance, just in one a single motor and in the other 3 motors.
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Yeah the table isnāt perfect but it is really close to your finding.
I think it was just interesting to see it in a table this way. Puts things into perspective.
I think a lot of constructions these days are governed by shipping, storage, size and weight etcā¦
It would be interesting to see where speakers would go if these constraints were not an issue.
My guess is that we would see more sensitive speakers with large cabs and 15" woofers. Not the slim line speakers we often see. I believe this is done largely for aesthetics. Then we need attenuation and lowered sensitivity in order to get lots of bass from smaller boxes.
I think i would like to build something like this next and try a high sensitivity speaker & valve amp fed by a Naim streamer. Faital-3WC-15
Mitch I bought a used copy of the cd you recommended. Just need to rip it now!
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Can someone explain a bit how āmultiple smaller driversā can produce bass vs. fewer/larger drivers?
I guess that somehow the diameter of an individual driver isnāt all that important? This surprises me but obviously I believe it! I just donāt know how it works.
I am not going to try to go into too much detail as someone is bound to pick it apart and tell me iām wrongā¦ 
which i most likely am in some way or another.
If you play a 30hz tone at a certain spl on a 12" driver it barely moves.
If you play a 30hz tone at the same spl on a 6 " driver it moves back and forth quite a lot depending on volume but can be even as much as 1"
There is obviously more to it but essentially the bigger cone can move more air with less movement.
The problem arises when that same smaller cone is trying to play nice smooth midrange at the same time. This then starts to distort the frequency response from said driver.
With smaller speakers delivering deep bass, as i understand it, one of the things a crossover does is attenuates (reduces) the volume of the mid and high frequencies in order to match the target spl at say 30/40 hz from the woofer. This is what sometimes requires increases power from an amp.
Higher sensitivity speakers have less attenuation so require less power but need larger cabinets and bigger drivers to get the required low frequency.
Hmmm, not a particularly accurate description, with some errors in there, but I donāt have time right now to go into itā¦
ahh go onā¦ you know you want to.
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Aināt it Copland, mate?
(Tried writing American English)
Oops! when youāre right, youāre right!
I tried to explain above that itās about the amount of air that gets moved.
To use an analogy, think of lifting a stone.
A big guy does it effortlessly (big driver, little excursion)
A smaller guy can do it with more effort (small driver, a lot of excursion)
Multiple smaller guys can lift it together with as little effort as the big guy
Multiple drivers is of course more expensive and more complex to get right.
Having time now: your description of aspects of how speakers work and factors around their behaviour is rather garbled, with some part truths mixed with part fallacyā¦ for the sake of understanding I think it needs clarifying.
For the same loudness the same amount of air has to be moved: so at any given frequency a cone of only one third the area needs to move back and forth three times the distance. That means the smaller cone has to travel faster, so it has to accelerate faster and then decelerate faster on every half cycle. (That is the greater mechanical challenge for a smaller driver, balancing the advantage that with a smaller cone being lighter cone there is less less inertia, therefore the acceleration and deceleration take less effort.) The greater movement means that all else being equal the smaller driver will hit the end stops before the bigger driver, limiting the maximum loudness before distortion and/or damage. It also introduces a greater likelihood of distortion due to reducing linearity of response towards the limits of excursion.
The crossover has nothing to do with matching a target SPL at any frequency from the woofer, but for the signal to the woofer it acts to reduce doppler distortion from the woofer cone reproducing high frequencies as it moves back and forth at low frequencies, and to let the higher frequencies be handled only by a driver better optimised for them. It is nothing to do with requiring increases in power. More power is needed at lower frequencies (regardless of driver size) because for the same SPL the same amount of air has to be moved, so for every halving of frequency (halving of number of movements out/in) the cone needs to move twice as far, taking twice the energy. For the same reason the mechanical demands on the driver also increase exponentially as frequency decreases, requiring everything to be able to move that much further while still remaining in alignment, and with as near linear response as possible regardless of how far in or out the cone is.
On the subject of sensitivity, with one exception sensitivity is nothing inherently to do with size of cabinet, though it has everything to do with the driver motor and driver cone and suspension mechanics. With a given driver it depends on effectiveness of coupling with the air (e.g. horns create better coupling), and whether and how the coneās rear radiated energy (half of its output) is utilised or how effectively absorbed. The one way I can think of in which cabinet volume has an inherent direct effect on sensitivity is with sealed cabinets, where a smaller internal volume means higher pressurisation/rarefaction of internal cabinet air, creating greater resistance to movement of the cone (also reducing amplitude linearity of response). Larger cabinets are needed for effective reproduction of low bass partly because of the sheer amount of air that has to be moved, and in the case of tuned designs or horns because of the wavelengths involved.
Hopefully the above helps in showing how optimum size of driver is not as simplistic as suggested by the statement that smaller drivers produce faster bass, and hence why we see so many different approaches to speaker design. The fastest bass is achieved by curtailing it, as less has to move! And therein lies the challenge in accurately reproducing bass without curtailmentā¦
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For starters, the first section is basically the same but with more detail.
Secondly, crossovers often have to attenuate a drivers level to match that of the driver with the lowest sensitivity. Otherwise how is the volume the same for all drivers?
Thirdly, what i was saying about sensitivity is that it is basically a trade off, if you want low bass and high efficiency/sensitivity then you have to have a large cabinets and big drivers. Not that the size of the cabinet effects the sensitivity. If you want deep bass from a small cabinet then sensitivity/efficiency has to go down in order to achieve that.
http://www.troelsgravesen.dk/HES.htm
Have a read here and you will see what i am getting at with the sensitivity thing. I am not the best at explaining it, you must have misunderstood.
If you want it uncurtailed relative to the rest of the spectrum you will struggle.
Regarding balancing sensitivities between drivers, yes indeed that is designed into the crossover to attenuate the signal to tge more sensitive driver - sorry, it wasnāt clear to me that you had meant that (and is irrelevant in the context of fast bass).
Reflecting on this topic, a question rarely considered is what signals actually have such fast bass rise and fall times as to be a challenge to a decent speaker? Among conventional instruments the answer I believe is only percussion, as the rise time of even a plucked stringed instrument (for example) is not instantaneous. But looking at the bass drum, my understanding is the main impact information (āattackā) of a bass drum, is actually conveyed in the midrange not bass.
As for decay of bass, real instruments do not cease sounding instantly, and certainly are not heard that way especially in any real room. The speaker cone does need to stop movement when the signal stops - which is helped by good damping, both mechanically by the speaker box and electrically by the power amp. However, and significantly, in most untreated rooms there is added reverberation causing extended decay even when the signal and speaker stop abruptly. Therefore to get āfastā bass you actually need to address the room as well, whereas it seems that a more common approach is to blame the speaker and diminish the lower bass instead!
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