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General speaker questions for audio and home theater.

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As soon as you start....

using "vents", tight / accurate bass goes out the window. If one is willing to live with this undeniable fact and trade-off, both bass extension and max spl's can be increased by using a vent. If one is not willing to deal with slop but can deal with losing a few Hz of extension and not being able to play at 115 dB's at the bass extreme's, sealed designs using properly chosen drivers with the "most correct" sized and built boxes will always provide the "tightest" bass. As such, vented designs should be relegated to "low fi" use, such as pro sound reinforcement or use for sound effects ( Home Theater ) where volume of sound ( sensitivity ) is more of a concern than quality of sound ( linearity ). Sean
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PS... ANY driver with a high impedance peak at / near resonance instantly becomes "less tight" and "less controllable". This is due to the inability of the amplifier to load into / transfer power into the driver. Since 98% of all vented designs are of either passive radiator, ported, slot loaded, etc... design, and these designs almost universally have high impedance peaks / multiple impedance peaks due to their very nature, the bass is of lower quality.

PPS... There are ways to improve sealed designs beyond just proper implimentation of the driver / box interphase. This requires more driver(s) and a sturdier amplifier though. Obviously, the cost of such a design is increased, but nobody ever said high performance was cheap.

PPSS... your comments about dipole's and bass extension primarily has to do with either poor placement or lack of physical size in the room to obtain optimum placement. Due to either of these conditions, the wavelengths involved run into problems with out of phase cancellation, therefore reducing the output at the lowest frequencies. Optimally, one would want to use a dipolar loaded compound arrangement in a large room. Not only is transient response improved, but so is power handling. Due to the improved loading of the dipolar design and the lack of cancellation from increased room size, neither spl's or cancellation are as much of a problem. At the same time, linearity is improved due to improved transient response and less of a load on any given motor structure.

PPPSS... Horns are another valid attempt at achieving this, but the size and construction of the cabinet itself is relatively prohibitive. Internal reflections and standing waves within the horn body itself tend to lower performance and increase distortions. Radiusing the internals and paying attention to the flare rate / parallel surfaces inside the horn can minimize most of this though. The biggest problem here is the sheer physical size of the horn body itself, as the mouth of the horn would literally be quite huge in order to reproduce the lowest audible frequencies. As a side note, some bass horns are sealed, some are vented. The problems associated with vented bass horns and the horn body itself can then further compound themselves, producing what is truly a "high spl, low linearity" device.

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