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.
size of the driver
Coming from the "old school" and being a complete (or almost) novice here - in the old days back in 1970-75 we thought that the big (read - wide) driver will have better capability to produce more realistic sound, talking about lower end of the spectr at least. But nowdays I am seing 6 inch drivers stated as "bass". Just curious how well those perform or in another words what is the secret behind those if they really can perform at the same level as the 12 inch ones?
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? My feeling is that with somewhat lower 89 db or less you need to increase the volume in order to have more visible lower end?
Thank you for your time
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? My feeling is that with somewhat lower 89 db or less you need to increase the volume in order to have more visible lower end?
Thank you for your time
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- 45 posts total
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." |
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). |
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 |
- 45 posts total