Introduction
Choosing the best full-range speaker to meet your needs is an important decision. This article will help you understand the problems you will run into in particular situations, and then how each cabinet type is designed to solve the problems caused by those different acoustical environments. This article is broken into sections, but each section progressively builds off of the sections previously discussed. So, it's important that you read the whole article from start to finish. Ramsdell Pro Audio has 30 years of experience in every imaginable situation. Do we have all the answers to every problem? No one does. Chances are though, that if you are thinking about buying a system to handle a specific purpose, or even a wide range of applications, Ramsdell Pro Audio has experience with your situation and a good solution. We will discuss how specialized you should be when making your choice, how to make the best choice, and how each speaker design type is handles different acoustical environments you run into. This article is written so that by the time you're finished, you will have a pretty good idea what type of system would perform best in the situations it will face.
Types of Full Range Speakers Covered in this Article:
- Direct Radiator, Cone Woofer
- Direct Radiator, Cone Woofer with High Frequency Horn
- Cone Woofer with Horn Loaded Mid-Bass and High Frequency Horns
- Fully Loaded Horn Enclosures
- Line Array Enclosures
- Asymmetrical Horn Loaded Enclosures
How Specialized You Should Be When You Are Choosing a Full Range Speaker
Permanent Installation:
In this application it is best to be as specialized as possible as your budget will allow.
Portable Use:
This is a more involved decision to make. The wider variety of venues you want to do with a single type of cabinet design, the more compromises you will have to make and be willing to accept.
How to Make The Best Choice for Your Need
Realize first, reverberant sound is your enemy. The best way to minimize this problem is to create as little amount of reflected sound as possible. This is true with both a fixed installation and a temporary set up at an event. Your first and foremost goal should be to put sound where your audience will be and nowhere else. You do not want to position your speakers where a portion of their projected sound will be reflected off of walls, ceilings, or even an unused portion of the floor in an inside application. This problem occurs outdoors with reflections coming off of buildings or even trees. Your goal is to choose the best cabinet design that minimizes this problem and meets your output needs.
So, reverberant, echoing sound is bad for you. As a general rule, the less reverberant your room or area is, the wider dispersion speaker you can use. For example, if the room is fairly dead acoustically, you can get away with one 120° dispersion speaker per side. If you are doing a show in a basketball gymnasium you wouldn't even be able to step back 50 ft. and be able to understand the same 120° system. You are going to need two or three much narrower dispersion speakers per side to make sure you avoid hitting walls and ceilings as much as possible.
The further you get from any speaker system, your ears receive less direct sound and more reflected sound. There is a distance from your system in any given situation where 50% of the sound is direct and 50% is reflected (reverberated). At this point and farther, intelligibility begins to drop quickly. That's where you start to get lots of comments on how lousy of a job you are trying to do. This point varies depending on the combination of both the environment and your speaker system, so we can't just give you some equation to calculate it. We can only help you understand it.
Advantages and Disadvantages of Different Full Range Enclosure Types in Particular Situations
Read all 6 design types in order
1. The Direct Radiator, Cone Woofer
This design of cabinet has a cone woofer and dome tweeter. It's a non-horn loaded speaker. You will find this type of cabinet in Hi-Fi applications or recording studio control rooms. The direct radiator is basically a point-source reproducer and made to have as wide of coverage angle as possible. Because this type of speaker fires sound as wide as possible, it has a very good near field listening area. However, it needs to be in a fairly dead (acoustically absorbent), non-reflecting environment to sound good. Because this speaker design shoots 98% of its sound in areas where you are not in, this type of speaker would sound unintelligible in an acoustically poor, reverberant room. In reverberant rooms, very little of the original music program will reach your ears and most will end up on the floor, walls, and ceiling and thus will simply bounce back and fourth. Other speaker design types are made to deal with the problems caused by reverberant environments, this one isn't.
2. The Direct Radiator Woofer with High Frequency Horn
The most widely used PA speaker in the world is probably a 12" or 15" woofer with a high frequency horn mounted above it. When we refer to a "horn" we are talking about a horn loaded projection device with a high frequency driver mounted on the rear of the unit. Click for a picture of a cabinet that uses a horn.
The ability of your speaker to shoot a portion of its output in a smaller, more defined area is called 'pattern control.' The first step in improving the pattern control of your speaker is to use a high frequency horn. This is an improvement in your ability to focus the upper mid's and high's to where your audience is and nowhere else.
If your budget is limited to one box per side, a 15" with a 90º x 40º dispersion high-frequency horn would be a good first choice. For example, our 15-2-SS, and 15-X-SS series is designed for this purpose. This 15" with a 90º x 40 º dispersion high-frequency horn box design is not too large to be unmanageable and has a wide enough dispersion to cover most smaller-sized events. The next step up from this would be to have two of these boxes per side with a more narrow horn dispersion angle like 60º x 40º.
3. Cone Woofer with Horn Loaded Mid-Bass & High Frequency Horn
Let's say you start doing more shows, your system is growing in size, and you decide to tackle larger rooms. It costs a lot of money to acoustically treat an auditorium or gymnasium. Chances are you are going to find yourself in a large room with a reverb time of 2 to 5 seconds before the sound quiets down. You can get a ball park idea by clapping your hands once loudly and counting the seconds until the sound quiets. Your going to find out that the wider dispersion system you have won't perform to your expectations.
The next step in improving the directivity of your system is to use a speaker cabinet that horn loads the lower mid's as well as the high frequencies. Tremendous improvements can be heard in auditorium or gymnasium if you can add control in the 400 Hz to 1 kHz range. Pattern control in these frequencies not only helps in overall sound reproduction, but also helps with mid-bass feed back problems that arise in highly reverberant environments.
The only downside of this speaker design is the fact that the size of the enclosure will be larger and more expensive with the addition of a mid-bass horn section. If you don't horn load the woofer section, this design can be an effective trade off in box size, portability, versatility, and price.
4. Fully Horn Loaded Full Range Speakers
One step better than mid-bass and high-frequency horn loaded system is the horn loading of every component in the box. Not only do you get an improvement in pattern control, but also efficiency. With proper design, horn loaded bass and mid-range cone transducers can be as much as 6 - 10 dB louder than direct radiator type speaker designs at the same amplifier output! That's like having an amp that's four to eight times more powerful.
As discussed in the previous section, the lower we can go with good pattern control, the better. A fully horn loaded enclosure can put even more of the audio spectrum where your audience is and less where they aren't, which is where you don't want it. The narrower the dispersion of the horn, the more direct it will be and the further it will throw its projected sound. Remember, you are taking the same amount of energy and focusing it in a smaller area. It's like adjusting a hose nozzle from a wide misty spray to a straighter stream. It's the same amount of water, just focused better. You increase distance and accuracy.
By combining four or more of these speakers properly and flying them in the air you can achieve enough low frequency control to crossover to your ground loaded subwoofer section in the 80 to 90 Hz area. This gives the impression that the system in the air is producing the bulk of the sound, producing a more pleasing sound system.
There is always the Size vs. Portability Tradeoff in the pattern control of bass and mid bass horns. In order to respond and properly load to a particular frequency, the length around the perimeter of the mouth of the horn needs to be close to the length of the lowest wavelength you wish to reproduce with power. However, if you desire real effective pattern control, the length of just one side of the same horn needs to be close to the length of the same lowest frequency you wish to have control of.
Once again, you can see this results in a trade off between what you need and what you can economically transport. This leaves these really large horns to large, permanent install applications where they work well. To keep good coverage without having to transport massive boxes, you can combine four or more smaller speakers together to get improved pattern control and be more economically transportable.
So if the solution is really a setting up and combining a large number of full range boxes and getting really even pattern control, what's the best way to do it? Line arrays.
5. Line Arrays
Line array systems are a calculated combination of a large number specially designed full-range boxes that achieve even pattern control in all frequencies. Line array boxes get their upper-mid and high-frequency pattern control by having a wide horizontal pattern angle and an extremely narrow vertical pattern. Then, to get their mid-bass and low-frequency control they rely on the vertical combination of enough boxes to equal the length of the lowest note you want to control. This translates to approximately 2 meters to get down to 200 Hz and 4 meters to get down to 100 Hz.
Line arrays have a very unique acoustical property. Their output drops off at only 3 dB every time the distance from the array is doubled. Other speaker system designs fall off at 6 dB per distance doubling. That translates to line array systems going at least twice as far at the same level. Remember though, this phenomenon only occurs if you have enough vertical height in your array like we discussed earlier.
This unique acoustical property of line arrays allows you to achieve better levels at the rear of your listening area without being as loud to those up front. That's what we mean by even pattern control.
Line array systems do have some disadvantages. They usually end up being a more expensive box to purchase because of the larger number of loudspeaker components in each box. This results in more amplifiers to operate the line array system along with more cabling and expensive fly hardware. However, you end up with a system that has greater acoustic output and excellent versatility for its size. Check out our line array system and see how it's exactly what we are talking about.
6. Asymetrical Horn Loaded Enclosures
We left this last section out of our progressive explanation because this type of enclosure is usually used in permanent installations. If you are considering an installation in a square or rectangular listening area, this is an enclosure you should consider using.
The asymmetrical horn has a narrow dispersion at the top and a wider dispersion at the bottom. Just so you can see what we are talking about, here is a picture of one of our cabinets that use this horn type.
When you tilt a standard horn forward and fly it in the air , it projects a trapezoid-shaped sound pattern onto the ground with a narrow coverage up front and wider coverage in the rear. This is the exact opposite of what you really need. The asymmetrical horn corrects this phenomenon. It also has another unique quality. Because the asymmetrical horn has narrow dispersion at the top, the sensitivity is increased with distance, performing better than a non-asymmetrical horn flown the same way. This increase in sensitivity over distance results in less of a drop in sound level as you walk back to the rear of the room. This is the same 'even pattern control' concept we talked about previously. Another benefit that comes from this increase in pattern control is that you end up placing less direct sound on the side and rear walls of your installation, decreasing reverb problems and increasing sound quality perceived by your audience. If you are considering an installation in a square or rectangular listening area, this is an enclosure you should consider using.
Conclusion
You are going to run into all acoustical environments ranging from good to horrendous with reverb forever your enemy. So knowing how to choose the best cabinet design for the job is very important.
If you are considering a loudspeaker choice for an installation and you have read and understand this article, you can now look through our different loudspeaker selections and get a good idea of the type of cabinet design will best apply to your particular need. The best advice we can give to you before you make your decision is that you need to get as high of quality of speaker system as you can the first time. You always get what you pay for and if you are trying to cut corners, it will sound like that for as long as the system is installed. Doing it right will be a lasting testament to your reputation as a pro audio professional, and will satisfy your customer.
If you need a portable sound system, we suggest the solutions that we have found work best. We draw upon 30 years of experience Ramsdell Pro Audio has gained in every imaginable situation. The solutions we have chosen work best for what we have done over the years. Your situation may vary slightly, which is why we encourage as much research as possible.
We, at Ramsdell Pro Audio, use two different types of full-range loud speaker designs for our system that share a common subwoofer system. A 15" 2-way for smaller events and a fully horn loaded enclosure for larger venues. We use the same subwoofer system with both system designs. This system is more versatile for the money.
For smaller shows in outdoor environments or in really decent sounding rooms, we use 12" or 15" 2-way speakers with a 60 º dispersion high-frequency horn. If we need wider coverage, we will use two boxes per side. If we need higher output or extended low end, we will add sub woofers, bi-amping or tri-amping the combination.
For larger outdoor shows or highly reverberant indoor events, we use a horn loaded, full-range box that can go down into the 80-90 Hz region. With this, we use a separate subwoofer section that either stays on the ground with the full range system flown or serves as a base to stack the full-range boxes on. This way we have a common subwoofer system that we like and are familiar with.
We have small full-range speakers that can be transported by smaller vehicles instead of large rental trucks. We have a larger horn-loaded system for projection and pattern control for larger events or obnoxious sounding rooms.
These are the general solutions we have found work best in these situations. No two installations are the same, and no one road system will be perfect for every gig. Each system needs to be chosen carefully to meet your specific needs. We hope the understanding and insight this article has given you will help you make a wiser, more informed choice about your full-range speaker system that will leave you and your customers proud to have Ramsdell Pro Audio speakers.
New article coming soon, "How to Use Your Full Range System" |
