Sound Advice - Home Audio Related Q&A

Q. What is your "claim to fame"?

A. Without a doubt, our pro-grade ribbon or planar tweeters on larger die-cast wave-guides. This combination provides 30kHz. top-end FR, lower distortion and ringing, a more-uniform sound dispersion and higher-efficiency anywhere from >100db 1w/m down to 1kHz.

The Spectral Decay Plot for a state-of-the-art compression driver at Left shows severe ringing, especially at typical power levels.

The Spectral decay plot for the SA 8535 Ribbon/planar tweeter at Right, shows much less mid-range ringing and almost no High-Freq. ringing, with much smoother and more extended high-freq. response!

The above plots explain why pro-high-freq. compression drivers sound harsh and quality planar tweeters sound natural. Also, the small ribbon & planar tweeters, used by others, only go down to 2 to 3kHz. and don't have uniform dispersion (compared to ours).

Few-costly brands are offering such quality planar tweeters in their production loudspeakers. These high-SPL ribbon/planar tweeters are matched to large planar (or pairs of high-quality cone) MF drivers; it is important to match dispersion from MF to HF, also an unusual feature.

Q. How does the sound quality of your speakers compare?

A. By including premium concert-sound woofers (w/low moving mass & high motor strength) between the true sub-woofers (with ultra-long-stroke/excursion) and the mid-range drivers we are able to provide a much higher sound-level-output (hi-SPL) and exciting/"punchy" bass along with more extended low-frequency response than commonly offered to the concert & studio loudspeaker market.

Q. Does woofer size matter?

A. Yes, woofer size is very important; assuming the use of a quality driver, the woofer cone and voice-coil size are the primary factors in predicting maximum sound-level-output. The box-enclosure size is the primary factor in predicting how low (in frequency) a woofer can play in combination with efficiency; while enclosure type and how low the woofer resonate frequency is, will also be factors.

Classic pro-sound woofers are very efficient, but needed very large enclosures to provide any low bass. Some newer pro-sound woofers work in smaller enclosures by adding some mass (like hi-fi woofers but less so) and/or by requiring equalization to get full low-frequency extension (40 to 50Hz.).

Modern hi-fi sub-woofers tend to be in small-sealed enclosures with a built-in amplifier & equalization to get full low-frequency extension. While a small sub-woofer can sound decent at low sound levels, the notion of a small sub-woofer is basically a contradiction in terms. A small sub-woofer can not be made to:

  1. Play as loud (max. SPL) as a larger unit
  2. Have as low-frequency extension (<30Hz.), and
  3. Have superior dynamic range.

These features are mutually exclusive in a small-sub-enclosure. It's like the old sign in many quick-print shops: "quality, low-price, speed; choose any two".

Mass market consumer (home-stereo) loudspeakers have been getting smaller and lower-cost. Many people don't seem to notice that the sound quality goes down with the size and price.

Q. What are the best types of bass/woofer box/enclosures?

A. The best woofer box type is dependent on your usage (music style & sound level), listening skill, box/room size/space constraints and budget.

Design Goal: Add-on subwoofer for small-room (home) system, low cost, good transient response, small box. Sub system: Typical premium-brand Sealed enclosure with a built-in amplifier & equalization to get full low-frequency extension. But remember that size matters.

Design Goal: High-end home & studio applications; size no object; excellent transients.

Sub system: Infinite or TL type very-heavy walled boxes; subwoofer drivers 12-15″ long-excursion, Subwoofer drivers powered by a >1kW, dedicated amplifier(s) (with DSP EQ/XO).

Ideally, the subwoofer is a bi-amped 2-way system including a short-coil (pro-sound) woofer with a stiff cone for the upper-bass "punch/slam" range (50-150Hz.) and a separately powered larger or pair of opposite-mounted long excursion subwoofer(s) for the lower bass range (15-50Hz.).

Design Goal: High SPL concert sound reinforcement in large spaces, size no object. Mid-Bass using 10-12″ drivers and Sub system using 15-21″ drivers:

A. Multiple-large-Tapped or large-folded-horn subs or,

B. Multiple-large ported boxes (premium-pro-brand).

Ideally reversed cardioid subs added for directional control.

Subwoofer drivers powered by >3kW, dedicated amplifiers with DSP EQ/XO.

For more on sound design in large spaces see my design site at

While the list of bass-box types in the following section Q3 is available online (for the most part), there is not good consensus on the list, much less are the best choices explained nor suggested. This outline above is an attempt to clarify and summarize our subwoofer suggestions and preferences, based on the differences in application, cost, performance and size.

Q. What are the various types of loudspeaker & sub-woofer (bass-box) enclosures?

A. To achieve full low-frequency extension, some sort of loudspeaker box/enclosure is needed. Since the box affects mostly the bass frequencies and bass-box is a more all-inclusive label than sub-woofer, we will use the term bass-box here.

There are several types of bass-boxes; they are well documented in several loudspeaker books (from & other web sites) and on several loudspeaker web sites including, and So our comments here will be brief as possible, omitting history, with minimal technical details.

Over 90% of the hi-fi speaker/subwoofer box types in mass production are Sealed or Vented boxes. Over 90% of the studio and concert-sound bass/speaker/subwoofer box types in mass production are Vented boxes. The most common types of bass-box systems are briefly covered here (Aperiodic, Isobaric and other rare-esoteric bass-boxes will not be discussed):

Q. Are pro-sound woofers better than hi-fi types?

A. For the most part, yes. High-quality pro-sound woofers have many advantages over hi-fi type driver/woofers. Pro-sound woofers are commonly better built (heavy magnet & cast frame & larger voice-coil), to handle the more abusive use in concert-sound & studio applications, so tend to be stronger and handle high power (avg. 1,000W RMS). Pro-sound woofers are much more efficient than hi-fi woofers (typ. 6-9dB greater or more), so they can play much louder or can be used with a lower-power amplifier (like tube amps).

More importantly, pro-sound woofers are more dynamic and life-like sounding because their more powerful magnet and/or lower stored energy, due to lower moving mass (Mms) of the coil & cone; especially when they are mounted in a very-large specialty box/enclosure (bass horn, TL or IB), detailed in post above.

The down side of most pro-sound woofers, is that while they are typ. designed for max. output at mid-bass frequencies (80-800Hz.), they don't have the long excursion nor low-resonate freq. needed for true sub-woofer use, so (multiple) true sub-woofer drivers would be needed as well, to cover the lower <30-80Hz. range. Heavy equalization can be used to extend the lower range, but doing so reduces the maximum sound level.

Note that there are some costly car stereo (competition) driver/woofers that are well built and high-power, but they tend to be high-mass, so more for true sub-woofer use (30-80Hz.) and of low efficiency.

Some great sounding hi-fi mid-bass drivers/woofers are available (from factories like Seas). Hi-fi mid-bass drivers go much lower in freq. (30 to >2kHz.) than what pro-sound people call a mid-bass driver; pro-sound people would call them a woofer. The better hi-fi mid-bass drivers have low moving mass and heavy cast frames, but smaller voice-coils; larger voice-coils (for higher-power) would add too much moving mass or require a much bigger magnet, so they have less max. sound level than (more costly) high-quality pro-sound woofers.

© 2010 David Kennedy, Audio Engineer
Feel free to contact the author for more info.