So after almost a dozen articles we finally arrive at the end of the signal chain—the loudspeaker. We will approach this is two or three parts. This time we will concentrate on full-range speakers or what are often called “top boxes” when run in a system with subwoofers. The next part will cover Subs and possibly monitors.

One of my favorite quotes about PA speakers, in that they are always perceived as too small going into the gig, and too large coming out. My opinion on speakers may catch you by surprise, but I believe main audience speakers are a lower budget priority when planning the things you “must have” to create a sound system. Not that main audience speakers are not important, but you are likely going to upgrade these speakers often as your act moves from garage band gigs to working bigger clubs and occasional outdoor gigs. And as you move up the ladder, your better venues often have good speakers already in place.


JBL MRX515

First Buys
So what should you buy as your first set of speakers for your band? I actually recommend scouring music store used sections and online auctions for getting the most speaker for the limited bucks you have. If lack of money overrides all other criteria, shopping for used mains speakers is the best way to get “capability” for the limited money you have. After all, your budget priorities should be first in getting good quality microphones, monitor system, and a usable mixing console before Front Of House speakers. (One word of warning here—beware online auctions where you cannot actually hear the speaker before buying. Also make sure to consider shipping costs. Speakers are heavy and expensive to ship.)

Back when I started shopping for mains speakers decades ago; the standard was “PA Columns”, where narrow and tall cabinets featuring small woofers and maybe a high frequency horn was the norm. Today, the basic “top box” featuring one or two 12” or 15” woofers and a decent high frequency horn is considered the proper first mains cabinet for starting out bands. A classic example is Peavey’s SP-2 speaker (a.k.a. the Spider Series) with a 15” low frequency driver (woofer) and a large horn driven by a 1” throat high frequency driver (tweeter). And do not forget the tripod stands for these cabinets.

 

Getting Picky
After getting past that initial set of capable speakers for garage band gigs, you may be willing to put more funds into a “quality” set of top boxes, and maybe add some subwoofers as well. The next criteria for top box speakers is efficiency; in other words, the most loudness for the given power amplifier watts you have available.

Most professional sound loudspeakers have sensitivity ratings in the range of 93 to 103 dB SPL with around 98 dB SPL a typical value for many popular models. If you decide to go with powered speakers, then the sensitivity is buried in the loudness rating (dB average) where the amplifier power in watts is multiplied by the unlisted sensitivity rating. Most decent quality speakers should be capable of attaining close to 125dB SPL or better when run between average (RMS) and program power levels.

 

Peavey SP Series

 

Power Ratings
Speakers with large power ratings will help deliver the loudness to the audience. The RMS or average power rating is derived by manufacturers testing speakers with constant signal levels to the point were the woofer or tweeter voice coils overheat and go open-circuit like a fuse. A better rating is the continuous music power or program power rating is which music-like signals are used to arrive at maximum undistorted reproduction. The peak power rating is mostly a damage level wattage rating in which the drivers mechanically destroy themselves by over-excursion of cones or diaphragms.

Typically, these power ratings hold close to a “doubling” relationship; in which program power is about double the RMS rating, and peak power is about double the program power rating. So the JBL MRX515’s 400/800/1600 watt ratings for RMS/Program/Peak make sense.

Frequency Response
And all of these contributions to the loudness equation do not help much, if the speaker can not reproduce the music frequencies needed for the gigs. Typically top box speakers are expected to evenly handle audio frequencies from 80Hz to 12kHz in range. Below 80Hz, subwoofer speakers are better suited for these lower frequencies coming from bass guitars, kick drums, and synthesizers. Above 12kHz, all you are getting is increased fidelity of cymbal sounds. And most middle-aged men (like me) or older do not have a shot of hearing beyond 12kHz.

FBT HiMaxx 40A

Driver Combinations
Beyond these basic specifications, the next obvious question is; why one combination of woofers and tweeters over another, versus a three-way system with mid-range speakers as well? Smaller two-way speakers may make things easier transport, but a 12” low frequency plus horn tweeter will not give you good low frequency support and is best suited to vocals-only sound reinforcement. But a pair of 12” woofers and a horn tweeter makes up for the weak low-end plus gives you more sensitivity to work with. The 15” woofer and tweeter horn is a classic combination, but sometimes can be a little rough in the mid range frequencies. As always, let your ears be your guide.

By also doubling up on woofers (two 15” and horn), the added low frequency support might be a good stop-gap before affording subwoofers. Three-way speaker systems typically are configured with 15” on the lows, 6.5” to 10” on the mids, and a 1” tweeter for the highs. For the increased size, cost, and internal crossover sophistication; they have the benefit of providing a bit more vocal frequency fidelity than similar two-way speakers. But three-way speakers may also give up a couple dB’s of sensitivity compared to a dual 12” or dual 15” top box speaker. So loudness and mid-frequency fidelity may be a tradeoff.

Buying Decisions
As always it comes back to that most basic of questions “What are you gonna use it for?” Always remember the term “sound reinforcement.” That is what a sound system is meant to do—reinforce the sound produced onstage. At higher levels of the production world, the PA bceomes more like a very large home or studio playback system with very little if any sound actually coming from the stage but we’ll worry about that scenario later.

For now that means getting the vocal up above the band and making acoustic instruments louder. If you are trying to amplify vocals and acoustic guitar or even a sax, then a two-way system with a 12” speaker will do nicely.

Moving up from there, again you have to look at the ultimate goal? How loud do you need to be? If fidelity is more important than brute power then moving up to a three-way system will work nicely. If you are doing heavier music and need the volume then a two-way system with dual 15’s will move a lot more air.

In the next chapter, we will elaborate on subwoofers and how to pick the best model for your needs.

Originally posted 2009-08-28 17:49:50.