By: Professor Humphreys
Speaker Engineer

Put simply, speakers make sound waves. They pull this off by converting electric signals to movements of air. The mechanics of all this can be easily understood. Since knowledge is power, enjoy the process of becoming more powerful as you journey through this course.

The Anatomy Looks Something Like This:

• Cone: this is what pushes the air and begins the sound wave’s journey. Most modern tweeters move air with a dome rather than a cone.
• Voice coil: the electromagnet that drives the cone.
• Magnet: the non-changing magnetic field that allows the voice coil’s alternating magnetic force to be attracted or repelled.
• Top plate, back plate and pole piece: the magnetically conductive parts that efficiently concentrate the magnet’s energy around the voice coil.
• Spider: a springy cloth disc that keeps the voice coil and bottom of the cone from moving off to the side while allowing it to move forward and backwards.
• Surround: a springy ring that keeps the top of the cone from moving off to the side while allowing it to move forward and backwards. Together with the spider, a suspension system is formed for the parts that move, the moving parts being the cone and voice coil.
• Flex wires and wire terminals: this is how the electricity from the amplifier connects to the voice coil.
• Dust cap: a cover glued to the cone that keeps debris from getting into the gap between the magnet and the pole piece where the voice coil resides.
• Frame (or basket): what holds all these parts together.

To Sum It All Up

The voice coil is an electro-magnetic engine whose north and south poles are determined by which way it is charged. Charge it one way, and the coil move up. Charge it the opposite way, and the coil moves down. Place the coil near a permanent magnet, and by alternating the charge, it will either be attracted to it or repelled away from the magnet. Now, attach this coil to a membrane (the cone) so that you can push some air around, hook it up to an amplifier with an audio (alternating) signal and, eureka! you have a speaker (less the cabinet and cross-over).

The Specs of Specs

Let’s face it, you start shopping for speakers and you have a heckuva lot to keep track of. Acoustics, speaker placement, speaker efficiencies, the sales pitch, and so on. Relying on specs might seem like a handy solution to the confusion but consider this: specifications can be misleading.

One reason is that there is very little supervision in monitoring specs. So some manufacturers are prone to hyperbole. Further, most performance specifications depend on unstated test conditions that aren’t standardized. With this in mind, rest assured there are some tricks-of-the-trade you can learn that will give you a shopping advantage.

Tricks-of-the-Trade

1. What is Nominal Impedance? Think resistance. But first a little background. All electrical devices resist the flow of electricity to some degree. Because they resist at some frequencies more than at others, engineers thought they would confuse the layperson. Thus they chose the word impedance instead of resistance. But the concept is the same. The nominal impedance (resistance) means “the lowest the impedance (resistance) will be at any frequency is not much lower than the spec listed.”  This spec is unrelated to the quality of speaker performance but it can effect how much power your speaker draws from your receiver. The lower the impedance, the more power the speaker will draw from your receiver with the “volume” knob at a given position.
2. What is Efficiency (also known as SPL)? Cars measure their efficiency in miles per gallon, speakers in decibels (dB) per watt at one meter distance. If a speaker is 10dB higher in efficiency than another, it will play twice as loud with the same amount of power. An increase of 3 dB means it will play just as loud with half the power. Don’t mistake efficiency for quality. In fact, many good speakers, like high performance cars, are low in efficiency.
3. What is Sensitivity?This takes efficiency and adds the effect of impedance. If two speakers are the same in efficiency but one as half the impedance (resistance), it will play 3dB louder since it’s drawing twice the power from your amp (and that’s without touching the volume knob). Efficiency and sensitivity are unimportant unless:
   • You’re afraid your receiver can’t play your speakers loud enough, in which case efficiency matters.
   • You want to play two sets of different speakers at the same volume, in which case sensitivity matters. For home theater, your receiver will typically allow you to correct for differences in sensitivity between your speakers.
4. What is Frequency Response? This is usually the most reliable indicator of a speaker’s sound quality.  Unfortunately, it’s also the easiest spec to manipulate given that it depends on microphone placement, room placement, how the graph of the response is scaled and smoothed, etc. If your speaker system really is +/- 3dB from 300 Hz to 18,000 Hz in a lab condition and +/- 5 dB from 30 Hz to 500 Hz in your listening position it’s likely to be a fine sounding system indeed. If you choose to look at response graphs, remember: rough peaks that are narrow in frequency range are actually less of a problem than smooth graphs that have a wide frequency range that is low or elevated.
5. What is Crossover Frequency? This refers to the frequency when one driver starts to play louder than another. This spec, taken by itself, means almost zilch. Sometimes roll off slopes, such as 12 dB/oct, will also be specified. Although this spec might mean a little more, engineers can’t agree what kind of slope is best. If you’d just as soon not go insane ignore crossover specs. They really only mean something to speaker designers.
6. What is Power Handling?Continuous power handling is only limited by how hot the voice coil can get before the glue that holds the wire begins to melt. Peak power handling refers to how big of a momentary burst (at the most troublesome bass frequency) a speaker can take. Because power handling is the one spec that most people think they understand, it’s often used to judge a speaker’s overall quality. Bad idea. Here are three reasons why:
   1. If a speaker claims to handle 100 watts, is that for a second, a few minutes, or an hour? Is it program material, sine wave, or some designed test noise? The same speaker could have been rated by another manufacturer at 20 watts.
   2. Power handling is unimportant unless you intend to play your speakers really loud over a long period of time.
   3. This rating does not have to be higher than your receiver’s power rating.
7. What is Recommended (amplifier) Power? This defines the manufacturer’s idea of a sensible range of amplifier (or receiver) power for their speaker. This specification is a helpful way of subjectively combining power handling and efficiency into one useful rating.
8. What is Max SPL: Again combining power handling and efficiency into one spec, this is a measure of how loud a speaker can play. It’s hard to make sense of this spec. There are ambiguities associated with power handling plus a lack of agreement on whether the test should be done in a live room and at what distance from the speaker.

These speaker specifications try to tell you things like how well a speaker will match up with your receiver, how loud they can play, and some other things that, for lack of a better word, are just plain silly. Some specs also try to convey something about how they will sound. But to really determine how good a speaker sounds, you will need to put aside the specifications and just listen. To help you do this well, get some advice in our “How to Make Fair Speaker Comparisons” class.

For those who can’t get enough of the nitty-gritty about speakers, here are some additional resources to satisfy every level of technical curiosity. Enjoy.

• Sound and Water Waves – The University of Tennessee Department of Physics and Astronomy
• Frequency, Octave, and Wavelength – Room Acoustics
• How We Localize Sound – Physics Today on the Web
• Art Ludwig’s Sound Page – One Guy’s Thing

Why crossovers?

Speakers produce an astonishing range of waves! The highest frequency humans can hear requires a speaker’s driver to move back and forth 20,000 time a second in order to make those 2/3” long sonic waves. The deepest audible bass makes the driver move about 60 times a second and sends 50’ sonic wavelengths out at your room. That may sound like hard work, but speaker drivers do it every moment they’re playing music. The physics that govern what it takes to produce these waves demands different kinds of machines for the fast, short waves than for the long, slow ones. This is why speaker boxes contain drivers that are treble specialists (tweeters), bass specialists (woofers), and sometimes midrange and low bass specialists. So the first job of a crossover is to split these frequencies up and send them along to the proper drivers.

But crossovers do much more. Speaker drivers need help. Lots of help. They play louder (are more “sensitive”) at some frequencies than others and can benefit from being “equalized”. Tweeters are usually more sensitive than woofers and need to be brought into balance. The very cabinet that a driver is put into has a large effect on which frequencies play louder and therefore need to be accounted for. So, the second job of the crossover is to manipulate the signal it sends to each driver so that it:

• Is just what’s needed for each driver to sound its best.
• Adjacent drivers interface well.
• Different driver outputs are matched so that they all play at the same loudness.

And, believe it or not, there’s more. Crossovers affect the timing of when sound waves originate from a driver which, in turn, determines if the waves from other drivers meet in a coordinated fashion or not. Further, they play a large role in defining the only speaker property your receiver cares about: its impedance.

So that’s a brief description of what crossovers do. From here on, the discussion will get a little more technical so, if you’re not already versed in some audio vocabulary and concepts, we recommend that you first read “Physics of Sound” and “How Speakers Work” before proceeding. If you’re fairly well learned in this subject, put on your trusty thinking cap and proceed.

How do crossovers work?

Crossovers create the shaped bands of frequencies that are tailored for each driver through the use of only three kinds of filters: capacitors, coils (called inductors) and resistors. Let’s look at what these filters do “theoretically”, before considering some real-world complications.

Resistors: Say an amplifier is delivering 10 watts of power to an 8 ohm tweeter. Then you place an 8 ohm resistor in line with it (in series), how much power will the tweeter then “see”? The answer is 2½ watts. The new 8 ohm + 8 ohm load tells the amplifier to deliver only half the power as before (5 watts) and half of that power is “used” by the resistor; half by the tweeter. This would attenuate the entire tweeter’s range by 6 dB if, in fact, the tweeter was 8 ohms at all frequencies.

Now, if you place the same resistor across the tweeter’s terminals (in parallel), what would you expect? You might be surprised to learn that nothing will change at the tweeter. The parallel resistor reduces the amplifier’s load to 4 ohms, causing it to deliver twice the power, but all that extra output gets shunted through the new resistor, leaving the tweeter unfazed.

Capacitors and Inductors: A capacitor placed in series with a speaker, as shown in the schematic below, will block the low frequencies and pass the highs on through. Notice that the “roll-off” slope is fairly gradual and smooth – this is the theoretical slope that occurs when the tweeter has a flat frequency and impedance response (they remain constant with frequency). The steepness of the slope eventually reaches the point where it attenuates 6dB for every octave further away from the tweeter’s operating range. This is often called a 6dB/octave or 1st order rolloff slope.

Maybe the crossover designer wants a steeper slope so that the tweeter won’t receive so much energy below where it operates well. They may try something like this, which results in a 12db/oct or 2nd order rolloff slope.

Steeper slopes – 3rd order (18dB/oct) & 4th order (24dB/oct) are sometimes used – can be obtained with more parts. Changing the part values will result in differently shaped slopes – maybe you’ve heard of Linkwitz-Riley, Bessel, Butterworth (not the syrup) or other kinds.

Next, let’s see what happens when we throw a woofer into the design:

Notice how the total speaker output in the crossover zone depends on the sum of the woofer’s and tweeter’s outputs?

Real world complications

So you’re thinking, “That’s pretty easy – Just figure out what frequency and slope type I want, then pick the part values off of a chart.” If that were true, crossovers could be designed in a few hours instead of a few weeks or months! Unfortunately, once real drivers and enclosures come into play, the above crossover might produce a graph something like the one below. Real parts introduce eight complications worth looking at:

Drivers don’t have perfectly flat frequency responses. If these deviations occur near the crossover frequency, adjusting the parts values in the crossover can sometimes adequately address them. Other times, a notch filter can flatten-out a peak.

Tweeters are almost always more efficient than woofers and need to be brought down to a suitable level. This is done with the use of a resistor – an all-pass filter – that attenuates all frequencies evenly if it weren’t for some of the other five problems.

Waves can do some funny things. For example, waves shorter than the surface that makes them tend to beam their energy forward, kind of like light from a flashlight, while waves significantly longer than the front surface of a speaker, wrap around the enclosure and disperse pretty much evenly in all directions. The result is a lower energy density in front of the speaker for the evenly dispersing bass than for the forward directed higher frequencies (shorter wave lengths). This 6dB bass loss, sometimes called a “diffraction step,” means that the rest of the speaker’s output will need to be brought down to the now lowered bass level (unless the speaker near the wall behind it where waves are prevented from wrapping around). Often speaker designers will accomplish most of this by increasing the value of the first coil in series with the woofer, which is why it can be 2 to 4 times larger in value than what a chart prescribes.

Here’s another interesting thing waves do. When two waves of the same frequency meet, they band together (if they’re “in phase” with each other), totally cancel each other out (180° out of phase) or only partially help one another out. With speakers, this happens in the crossover zone where two drivers share the same frequencies. In the graph to the left, the drivers are 180° out of phase with each other even though they are both wired “positive to positive” – because the rolloff slopes introduce phase shifts of their own! Simply wiring the tweeter “backward” (with amp positive to tweeter negative) can correct this problem. But, if the phase differences tuned out to be, say, 90°, then there would always be some cancellation and the driver outputs would need to be increased in the crossover zone to compensate. The rule, if not for still other real world compromises, is that even order slopes (2nd, 4th) cross over 6dB below the overall speaker level (with 2nd order slopes requiring one driver with reversed phase); odd order slopes cross over down 3dB.

So you can see that controlling the rolloff slopes, both output and phase, is important for getting the drivers to sum properly. But the slope that matters isn’t what comes out of the crossover – it’s what comes out of the drivers. This means that driver’s natural roll-offs characteristics, the crossover’s rolloff (and more) all work together to produce the properties, both phase and amplitude) that determine how well the sound from the two drivers will integrate through the crossover zone.

When two drivers share the same frequencies, the amount that their waves add to each other also depends on where the listener is. The illustration above shows a speaker with a tweeter positioned above a woofer, a green listener, who is standing and a blue listener who is sitting down.

Let’s look at what happens at the crossover frequency – 3000 Hz in this case. The woofer and tweeter waves arrive at the standing (red) listener at the same time and add together. But for the sitting (blue) listener, the waves from the more distant tweeter arrive later than the woofer’s. He happens to be 2” closer to the woofer than the tweeter – ½ of the 4” wavelength at the crossover frequency. So the pressure wave from the tweeter arrives at the same time as the rarefaction wave from the woofer (180° out of phase) with the two waves canceling each other out, resulting in the same graph as in point 4) above. By the way, this is why drivers are usually above one another, so that this problem will manifest itself vertically – hopefully above and below the listening area.

While it’s easy to think of crossovers as filters that divvy-up the frequencies and send them on their way, they don’t really work like that. The amount that a crossover attenuates a driver depends on how much impedance it presents compared to the driver. Unfortunately, drivers usually have impedances that fluctuate greatly over their operating range. The graph below shows the impedances of a high-pass filter (capacitor) in blue, an ideal tweeter (resistive) in black and a real tweeter in red. The graph to the right shows the energy the idealized tweeter receives (again black) compared to what our real tweeter receives (red).

The last real-world complication worth listing here is that crossover parts have many electrical properties in addition to what they’re designed to have. This makes for effects that are different than what a textbook would predict.

In Conclusion

A while ago you may have been thinking that crossover design sounded pretty easy – but now you’re convinced that it must be close to impossible. The truth is that it’s really not that bad if you know the secret that many speaker designers keep to themselves – that it’s speaker performance that matters, not theory. Designers don’t need to calculate adjacent slopes, how the sound from two sources will add together and so on. They can just fiddle with everything until they deliver the desired sound — though it’s very true that knowing the theory makes you a much better fiddler. And now there are good computer modeling programs that can get a designer pretty close. But the process really comes down to fiddling with parts, measuring frequency and impedance character, listening and repeating over and over again until the speaker performance gets the big thumbs-up. Which is why good measuring equipment, a panel of golden ears and a good listening room are as indispensable as a phD in crossover theory.

Confused about how to install your banana plugs in your home theater system?  Caleb Denison walks you through the ins and outs in this informative video tutorial.

By Mike Hopkins: Aperion Product Manager

With the constant progression of digital media over the past 5 to 10 years, especially with music, there usually comes a time in your life where you are forced, one way or another, to make drastic changes in how you listen to music. The idea of wirelessly sending music from your computer or laptop to your home stereo system really becomes appealing when you start to realize one or all of these 3 things apply to you: 1. You don’t really buy many CDs anymore; instead you buy the digital copy (iTunes or Amazon) or listen to internet radio (Pandora or Slacker). 2. You have boxes of CDs that you have also ripped to your computer and if you do listen to the actual CD, it’s usually in your car. 3. Now that all of your music is organized and accessible on your computer, it would sound a heck of a lot better if you could listen to it on your home stereo system.

The question becomes, “How do you get music wirelessly from your computer to your home stereo?” The thing is, there isn’t one simple solution, in fact, there are many great wireless music solutions depending on what you want, how you listen and, of course, how much you are willing to spend to get it.

Scenario 1:All of your music is on your laptop and you want to play that on your Aperion home theater system.

Solution:The Aperion Zona Home Audio Link™ (Had to put this one first!)

The Aperion HAL system is an easy and inexpensive way to stream any music from your laptop or computer to almost any audio system in your home. Simply plug the USB from the HAL Send unit into your computer and connect a HAL Receive unit to your AVR just like it was an audio component. Once the two units are linked up anything that you play on your computer will automatically be streamed to your home stereo system. With the HAL system you can also add up to 3 HAL Receive units if you want to stream your computer music to more than one system or room in your home. Cost: $149 for the Aperion HAL Send/Receive pair and $70 for each additional HAL Receive Unit.

Downside: All audio control is done through your computer.

Scenario 2: All of your music is on your desktop or laptop and you want to play it on your home stereo system and other rooms plus be able to control what music plays in each zone via remote.

Solution: Sonos Multi-Room Music System

A Sonos system is a great way to stream music wirelessly to multiple rooms while still having the full control of all of your music via touch screen remote. A Sonos system consists of “Zone Players” (ZP120) which are essentially wireless 2 channel amplifiers. You can add “Zone Players” to different rooms and just connect your speakers. Additionally, you can purchase a “ZP90” which is a wireless zone receiver/sender which you can connect to your existing stereo system. The interface is great and the system has received numerous awards. As a bonus you can download a free App to turn your iPhone into a wireless remote to control the entire system.

Downside: Expensive. Prices start at $999 for 2 Zone Players (one ZP120, One ZP90) and a touch screen remote.

Logitech Squeezebox Duet is another system that is very similar to the Sonos system; however, they do not offer amplified zones. The Squeezebox Duet is a great system if you already have the existing stereo or powered speakers. Prices start at $379 for one zone and a controller, $129 for additional zones.

Scenario 3:I have all of my music on iTunes and I want to listen to it on my home stereo system.

Solution: Apple Airport Express and Air Tunes

If you have all of your music in iTunes, this is a simple and easy solution to stream music over your network from your computer to your existing home stereo system. Each Airport Express plugs into the wall and has a USB, Ethernet and Stereo mini plug output. Not only does each Airport Express unit stream music, but you can use it for networking printers and other computers. Prices start at $99 for a single zone.

Downside: Only works with iTunes.

Scenario 4 – Honorable Mention:I have all of my music on my computer and I want to listen to it wirelessly on my home theater system.

Solution: PS3 or Xbox 360

These two gaming systems can also be used as fully functioning media players. The PS3 has built-in wireless and the Xbox 360 has a wireless adapter for $79. Through the menu system of the game console you can link to your computers media, including music, picture and videos. Both consoles also have internet radio access through either an internet browser on the PS3 or via LastFM application on the Xbox360. If you or your kids have one of the above systems you are just a few steps away from accessing your music on your home theater system.

Downside: Unlike the other solutions using the PS3 or Xbox360 takes some patience to get the music playing. AVR, TV and navigating through the console menus are needed to access the goodies.

By Mike Hopkins
Aperion Audio Product Development Manager

Have you ever wanted to listen to some music in the kitchen while you were making dinner, but you just didn’t have space to add speakers and an amplifier? How about having music playing in the background in every room of your house? Well, the good news is that whole house audio is not as difficult as you might think!  Whole house audio is a great way to improve your home, not only in value, but in lifestyle and livability as well.

How do I get started and what equipment do I need?

There are a few different ways to run extra speakers in your home.  One option is to run the wire directly from a receiver, meaning the volume on your receiver controls the volume on the speaker. One nice feature available on most new home theater receivers is the addition of a powered or assignable second zone.  Some receivers even have three or even four separate zone controls.  A powered second zone on a home theater receiver will allow the addition of one pair of speakers to be used independently at the same time using a separate source. For example, you can be watching a movie in your living room in 5.1 channel surround sound, while the second zone, perhaps the kitchen, can be listening to a CD at the same time. Many manufacturers call this multi-room, multi-source capability. While the second powered zone feature is a great addition, it is really only intended to be used with one pair of speakers. If your 7.1 receiver doesn’t have a separate powered second zone, in most cases the 6th and 7th channel will be assignable to a second zone.  Huh? What this means is that your 7 channel receiver can run 7 speakers only, so you can choose between a 5.1 system and two “zone two” speakers, or a full 7.1 system.   If you want to run a 7.1 system and an additional pair of speakers, you will need another amplifier for the second zone.

Another common way to send amplified sound to multiple rooms from a stereo receiver is to use an impedance matching speaker selector from companies like Speakercraft or Niles.  A speaker selector can take the power signal from a stereo (2 channel) receiver or amp and distribute it to multiple pairs of speakers. The impedance matching ability tricks your receiver or amp into thinking it is just powering one pair of speakers, which protects the amplifier from damage. The only downside of the speaker selector is the audio quality and volume is diminished due to its being spread thin over all of the speakers as opposed to just a pair. Using a speaker selector can work well if you just want background music throughout your house and outdoors.

If you are looking for more volume and higher quality sound the third option is to install a distribution amplifier. Similar to a speaker selector device, a distribution amplifier allows you to run multiple speaker pairs. It improves the sound quality by adding an amplifier to the mix. This will give you more volume along with better sound quality. Distribution amplifiers range in price from a few hundred dollars to a few thousand dollars depending on the number of channels, power output and sophistication of the controls. Think about how you will use your system most often and get the amplifier that suits your needs. If you only plan to have one source and one volume control throughout your entire house, you can get by with a much less expensive distribution amp. If you want to control the volume in every zone separately and have multiple sources, you will need to spend a lot more.

Running Your Wires

If you want speakers in multiple rooms, the most important first step is getting the wires where they need to be. Running wires may seem simple enough, and it can be if done right… the first time.  Before you drill a single hole or run a wire, we always recommend drawing out a wiring diagram and measuring the distance from the receiver to your speakers. Remember to always give yourself extra wire when running to a location; while this may seem wasteful, cutting off a few extra feet of wire is far superior than realizing that you are 6” short on a 50ft run. If you are going through the ceiling or floor, be sure to take into account the distance over floor joists and around studs. This can add significant distance to the run. It is good to buy your wire in bulk on a long roll and pull it from the source to final location before you make any cuts. This will ensure that you don’t cut your wire run too short.

Once you have your diagram drawn up, count how many wires you’ll need and where they are going to end up. A few key ingredients are needed to make this work.   First, you’ll need a hub, or a place where all of the speaker wires terminate.  Each speaker will need two conductor speaker wires run to it, and usually each room will have two speakers. You will want all speaker wires run to the same location. This is where your receiver, amplifier or perhaps a music server will reside.

Be sure to use high quality 12-gauge wire or CAT-5 or CAT-6 cable.  Select a wire that’s durable enough and rated as safe for in-wall use.

Lastly, unless your house is still at the framing stage, consider this – do you have either an attic above or crawlspace below the walls where you want to put the speakers?  If the answer is yes, then you should be able to run the wires easily, if not… well, in our experience it’s time to look at other options, including high quality wireless solutions.
Advanced Options

Unless you use a volume control in each room, your receiver or amplifier must control the volume. Using one of these controls gives you the ability to adjust the volume in the same room as the speakers, instead of running back and forth from the receiver.  When running wires to a volume control, the easiest method is to send a single run of four conductor speaker wires to the volume control, and from there, two (left/right) runs of two conductor wires to each speaker.

If you want the ability to change the source, volume or music tracks, you’ll need a more complex control system in addition to CAT-5 or CAT-6 wire and speaker wire runs to each volume control in every room. Check out Russound, Elan and Crestron for advanced audio control systems.  Usually this is done in a house that is pre-wired and professionally installed and calibrated.  There are a few new gadgets available that can help by pass the need for an expensive control center, like an RF remote control, which is a remote that can control your components through walls using radio frequency — eliminating the need for volume controls or expensive touch pads.

Our Recommendations

If we had to choose a good, better and best system for distributed audio, this is what we would do:

1. Using two channels from your receiver to power another pair of speakers in another room works great.  Most home theater AV receivers already have this feature built in.  This is a simple solution that will only take a bit of effort to execute. You can also use an impedance matching speaker selector to add up to four pairs of additional speakers!
2. Use a receiver with a second zone to send audio to a separate two channel amplifier. Similar to option one, a separate amplifier will give better quality sound and volume levels which is safer for the speakers!   Tip: Use a multi channel amplifier for best results (look at Sherbourn and B&K).
3. Go big, and check out Crestron. This is our, “If we won the lotto…” option.  Absolutely awesome and priced to match, Crestron systems allow you to control the source, volume and music tracks using controls in every room in your house. The runner up would be a wireless amplifier system from sonos.com or check out Logitech’s new “Squeezebox Duet” wireless music server.

We hope this gets you well on your way to immersive, whole house sound.  If you ever have any questions, feel free to send an email or dial us up at 888.880.8992 and we’ll be happy to answer your questions on whole house distributed audio or any other audio or video topic.