To review: As power is increased sound ouput intensity also increases in a direct relationship, until something gives. That something can be the amplifier reaching its power output limit, or it can be the speaker reaching its thermal or mechanical limits. In any case, the result is the same. Increasing power input yields less and less sound output and usually more and more distortion until something really breaks or the power is backed off. This reduced output is known as compression, as the graph below shows.
In Part I, we discussed the need for the entire audio chain to be capable of unrestrained audio reproduction to reproduce the full dynamic range contained on today's digital soundtracks. We also discussed the unique position of pro audio components to fill this need.
In this Part we will examine the role of speakers in meeting the need for full dynamic range playback.
Speakers: The Last Word in the Audio Chain
Speakers are transducers, that is they convert one form of energy (electrical) to another (sound). A perfect transducer would have complete energy conversion and a completely linear response, that is the output would be a perfect representation of the input. But alas, loudspeakers are not very good transducers. Loudspeakers are horribly inefficient and producing one that closely tracks the input signal in both amplitude and phase is very difficult and expensive to do.
Pro Audio loudspeakers were traditionally designed to go after the efficiency issue. Pro Audio speakers were and are designed (at least good ones are) to be capable of reliable performance at high sound pressure levels (SPL's) in keeping with the pro audio laws of: 1. Make Sound 2. Keep Making Sound and 3. Make good sound. Fortunately number 3, Make good sound, has moved up in importance quite a bit as a priority.
The world of pro audio speaker systems can be generally broken down as:
1. Large venue concert systems, mostly line array systems these days.
2. Medium to large live sound concert systems, usually multi-cabinet, multi way systems for longer throw applications at very high SPL's.
3. Small venue and DJ systems, often single cabinets per channel, shorter throw for closer in audiences.
4. Installation systems, can be like 1, 2 or 3 depending on venue or smaller systems for distributed audio
5. Cinema systems, designed for soundtrack reproduction in commercial cinemas.
For home theater use, Large concert systems are too big, too expensive and are designed for listening from long distances. Small venue and DJ type systems as well as installed pro audio systems have promise. To this end, I've experimented in my theater with a number of these speakers.
This picture shows some of the speakers I've tried in my home theater in an attempt to build a system that had the capability to play at true reference levels without distress, compression or audible distortion. The list includes QSC, EV and JBL models.
What were the results?
Ability to play at reference levels: Found that the larger cabinets, those with 12" or 15" woofers and 1" or 2" compression drivers could generally reproduce reference levels in my theater easily.
Sound Quality: I found a bigger difference here between models than I expected. The crossover point and quality of the crossover has big impact, as does the horn design. In general I liked horns with equal horizontal and vertical dispersion best, and those with larger drivers (2" vs 1") better. I was not entirely satisfied with the vocal reproduction, especially in the center channel. There was a bit of sibilance (pronounced 'S") sound, clarity was good, just a bit edgy. I think a lot of this comes from break up modes in the low frequency driver as the 1600 to 1800 Hz crossover points are quite high for a 12" otr 15" driver to handle.
Integration: The directionality that the horn drivers provide allows for the sound to be directed to the seating area and not onto the walls, ceiling and floor. I found these speakers to be extremely sensitive to phase and distance to listener differences. Changing the speaker distance just a half foot in the processor had a huge impact on the front soundstage
Music and Impact: If you want to rock out or have a dance party, these speakers are it. Plenty of SPL's and impact, especially when paired with a capable subwoofer. A sub is a must with these speakers for Home Theater use as their response doesn't extend much below 50-60 Hz.
Conclusions: After living with these speakers for more than a month, I moved on. The primary motiviation was the harshness in the dialog. I'd still recommend them for an affordable system that can really rock, but for me I needed a bit more refinement, especially in the center.
Pro Speaker Questions...
Q: Why do you need anything that plays that loud?
A: It's not the maximum loudness that appeals in this sort of set up but the unrestrained dynamics. The ability to reproduce sound effects and music with it's full range from quiet to loud without distortion.
Q: Don't commercial cinema speakers roll off the high frequencies?
A: Many do, it's called the X curve and it compensates for the high frequency gain added in the film sound reproduction chain. The models I'm using do not employ this curve, and if you use models that do it can be corrected with equalization.
Q: Those Pro Speakers are a bit ugly.
A: It's true. Mine will shortly be mounted behind a screen wall and will be out of sight. The size and finish of pro audio equipment can be a barrier.
Q: What are some good brands?
A: Standard answer: It depends. The big guys in theater sound all have smaller systems that could be used in home theater (JBL, EAW, QSC, Klipsch). JBL makes a line of home theater speakers using their pro components JBL Cinema Array and the K2 line are both rooted in pro-audio. Other pro brands that could work well in home theater are Danley Sound and Yorkville U15's. Of the brands I've personally tried I'd consider the JBL MPro 412's.
EAW Cinema CB153x Screen Channel
Pro Cinema Comes Home:
After my extended experiment with pro small venue and DJ speakers, I decided to check out what was available in commercial cimena speakers. I looked at QSC, JBL, EV and EAW. I ended up finding a set of EAW CB153x front channel speakers and EAW CB82FM surrounds. I bought the fronts used and the surrounds new, but an older discontinued version.
What were the results?
Ability to play at reference levels: 1" compression driver, 8" High efficiency midrange and 15" low frequency drivers with an overall sensitivity of 98 dB SPL with 2.83V input, no problems reaching reference levels with room to spare.
Sound Quality: Voices have lost their sibiliance, yeah! A few tweaks in the form of some absorbtion and equalization to fix some chestiness, probably due to the mounting location close to the front wall.
Integration: Horns provide directionality, putting the sound where it is needed and not where it's not wanted. Much less sensitive to phase than earlier experiments. Tall cabinets will require reworking the screen for optimum placement.
Music and Impact: Still plenty of horsepower and clarity for music. The addition of higher powered surrounds has made listening to multi-channel house music a real treat. Dyanmic soundtracks are reproduced with full impact.
Conclusions: I've had these speakers for several months now and I like them as much as ever. Compression free and hi-fi. Comparing them with the first batch of pro speakers I tried they are much closer in performance to the more expensive models I tried. Comparing retail prices, these speakers are quite a bit more but are a three way design, optimized for theaters.