This is the (loudspeaker) way...

Intro

In this post we will cover the basics needed (frequency response, audio spectrum, crossovers) in order to understand the ways of speakers in the most common speaker configurations, along with some examples.

Basics

Frequency Response

Refers to the rate at which sound waves oscillate or vibrate, producing the sensations of pitch and tone that our brain interprets as sound.

The frequency of a sound wave is measured in Hertz (Hz) or Kilohertz (ΚHz), which represents the number of cycles or vibrations per second.

Audio Spectrum

Is the audible frequency range at which humans can hear and spans from 20 Hz to 20,000 Hz or 20KΗz.

Speaker Ways

What is the way?

The separation or division of the incoming audio signal, into different frequency ranges (by using crossover networks/filters) which are afterwards directed separately to the appropriate/individual drivers.

Crossover

Is a type of electronic filter circuitry that splits an audio signal into two or more (4 or 5 max) frequency ranges, so that the separated signals can be sent to the individual loudspeaker drivers that are designed to operate within these different frequency ranges. The crossover filters can be either active or passive.

Passive

These filters are made only with passive components (L/C/R_Inductors/Capacitors/Resistors) and no additional power source is required for the circuit. A passive crossover splits the incoming audio signal after its amplification from the stereo power amplifier, so afterwards the amplified signal can be send to the individual drivers inside the loudspeaker. For a stereo signal one crossover circuit per channel (Left or Right) or per speaker is needed. These filters are considered to be minimum phase filters.

Passive 3-way Crossover example (for a pair of speakers)

Active

This type of filters contain active components (transistors/op amps) so an external power source is necessary. In this case the signal is amplified after the crossover circuit, so a single amplifier is needed per driver. In a 2-way speaker (Woofer/Tweeter) we will need 2 amps per speaker. One for the woofer & one for the tweeter, which results to 4 amps total for a stereo speaker pair (Left & Right Channels).

This type of crossovers can be also implemented digitally with DSP (digital signal processors) using FIR filters. FIR filters have a linear phase response so they considered to be zero phase filters.

DSP board example

Cross outro

Crossovers have different orders depending on the filter slope they implement. The most common are 1st/2nd/3rd & 4th order. Highest orders have steeper filter slope,

so the filters are "cutting" the frequencies below (High Pass) or above (Low Pass) the crossover point more aggressively. We will explain this in more depth, in another crossover episode/post... Stay tuned & check the 4-way diagram to get a better idea about passive crossover circuit, orders & slopes.

Configurations & ways

1-way (Full-range)

Full-range is a loudspeaker with a single cabinet in which one driver (usually), covers the "whole" audio‑frequency range (80Hz-20Khz).

Pros

• No crossover is needed in this design

• Simple Cabinet / no tuning required. Only the appropriate cabinet volume (L) is required for optimal speaker performance.

• Maybe the lowest budget choice

Bookshelf / Driver: Dayton Audio RS100-4

2-way (Coaxial)

Coaxial Is a loudspeaker in which the individual driver unit radiates sound from the same point or axis. The most common form is a two-way design for professional audio, also known as single-source or dual-concentric. Coaxial loudspeakers enable sound from two drivers to come from one source.

Bookshelf / Driver: Tang Band W6-2313

Benefits over full-range

• Equivalent compact volume with higher quality

• Dedicated high end driver

  • More accurate frequency response & possibly "softer" high end

• Less woofer distortion

  • The woofer driver no longer needs to represent very high frequencies

2-way

Is a speaker that has at least 2 individual speaker drivers, Woofer (Low and Mid Frequencies) & Tweeter (Mid and High frequencies) which share the same internal cabinet. The most common woofer driver sizes/dimension ranges for 2-way speakers are between 5,5"- 8" (inches). The smaller the driver and the cabinet size the more likely is to need one (or two) dedicated subwoofer to recreate the low end properly, down to at least 30Hz.

3-way

Is a speaker that has at least 3 individual speaker drivers, Woofer (Low Frequencies), Mid-range (Mid Frequencies) & Tweeter (High frequencies). In this case the best approach for the cabinet would be to separate the mid & tweeter drivers internally from the woofer or sub driver.

If a mid-range dome type driver is used, this separation is not necessary (because the back of the driver is closed) but it's recommended. If a mid-range woofer is used (open back), it is absolutely critical to separate at least the mid-range driver from the woofer. When the driver is functional, the back side of the driver cone, radiates the negative signal in relation to the front side of the driver at all times, so the 2 drivers (woofer/mid) will compromise each other' s performance internally in the cabinet if not separated.

The woofer speaker drivers here can variate in any size from 7" to 18" (inches) or even up to 21". The sweet spot size that is enough to cover and recreate the frequency spectrum properly without compromises & without forcing the loudspeaker cabinet to be extremely big (above 120L internal volume), is the 10" sub or woofer driver.

2-way vs 3-way speakers crossover & frequency range

2/3 way basic differences example

2-way pros

• Simpler crossover design (1 crossover point)

• More affordable crossover & drivers cost, fewer components

• Smaller Cabinet (fewer drivers), more flexible placement & fit in small rooms

• More compact volume overall

• Possibly the best bang for the buck, more suitable for low budget setups

• Woofer & tweeter cabinet is common. Doesn't need 2 separate internal cabinet volumes. So the cabinet construction is simpler & usually lighter.

3-way pros

• Better/higher power handling

• Better frequency response and accuracy

• Each driver covers relatively small frequency range so it performs at it' s best

  • Highest clarity

  • Less distortion

• Bigger woofer (or subwoofer) can be chosen as the low end driver

  • Lower bass extension can be achieved (-6db point)

• Dedicated mid-range driver

  • Vocals, mids & upper mids range can be represented without struggle

• Tweeter doesn't need to do a lot in the mid frequency range so it performs effortless, sounding more open & "soft"

• Overall the 3-way design (if implemented right), offers the best sonic outcome & is capable to cover sufficiently the whole audible frequency range without

  • the need of a subwoofer

  • sacrificing distortion, clarity or power handling

• Can be implemented in a relatively reasonable price for the quality that it provides

  • It is the highest quality choice you can get without the premium hi-end price tag

How to chose between them

2-way: Chose when needed for casual listening, background music in smaller spaces, lower cost "beginner" setups & in any case in which a fairly balanced frequency response is good enough or the more affordable option is more crucial over sonic quality.

3-way: Chose when needed for critical listening, music production, home theater applications, audiophile hi-fi listening & any other case in which the mid-range, proper lower bass extension and accuracy is critical, so a more refined and "demanding" sound is required.

More examples & drivers configurations

2-way speaker

• 1 driver per way

• bass reflex port in front baffle

2-way speaker / 3 drivers total

• 2 mid-woofer drivers in MTM configuration (& parallel)

  • for lower distortion, higher sensitivity (db) & superior dispersion

3-way speaker / 3 drivers total

• 1 driver per way

• double bass reflex ports on front baffle

3-way speaker / 4 drivers total

• 2 mid drivers in MTM configuration

• single woofer driver per speaker

• double bass reflex ports on front baffle

3-way speaker / 5 drivers total

• 2 woofer drivers in parallel configuration

  • for lower distortion & higher sensitivity (db)

• 2 mid drivers in MTM configuration for superior dispersion

• double bass reflex ports in back

4-way speaker / 4 drivers total

• 1 driver per way

• front bass reflex port

4-way frequency range/bands in a passive crossover example

Conclusion

Hear it, test it, A/B compare it if possible and choose wisely, deciding what fits your budget, your listening room and most importantly your ear preference. But beware and be advised that 3-way is the way...

Take care of your vinyls... 'til next post...