A34 - The low frequency roll-off of a woofer and its associated group delay are optimal, from what I have observed, when they follow the response of a 2nd order highpass filter with Q = 0.5. When a driver is mounted in a dipole W-frame or H-frame its mechanical resonance frequency Fs decreases to Fd, due to air mass loading, and Qts increases by a similar percentage to Qtd. For example, a driver with very strong motor, Fs = 18 Hz and Qts = 0.2 might have Fd = 16 Hz and Qtd = 0.

A28 - The shorter you make D, the distance between front and rear openings of the PHOENIX and H-frame woofers, the higher the frequency for which the rear wave adds in phase to the front wave, and the unequalized dipole output reaches its first 6 dB peak. Unfortunately, there is a resonance that comes into play before this peak. The cabinet structure between the driver cone and the cabinet opening forms an acoustic transmission line.

A30 - A dipole placed in a room corner should provide minimal excitation of room modes or resonances. The corner is a region of maximum sound pressure and it is well known that a typical monopole woofer in this location will couple optimally to all room modes. A monopole woofer would be a high impedance pressure source in the high impedance region of all wave modes (Z = p/v) and be optimally adapted to support them.

A39 - It is often assumed that excessive amounts of power are required to drive a dipole woofer, because of the necessary 6 dB/oct acoustic roll-off equalization and additional boost required for drivers with Qts below 0.5. In fact, equalization does not change the power requirement. It is a driver's cone excursion for generating a desired SPL which determines how much output voltage and current an amplifier must be able to provide.

A31 - Yes, there is, from a sound reflection and also from a standing wave point of view. Both are a consequence of the figure-of-eight or cos(angle) free-space polar response of a dipole with its opposite phase front and rear radiation and very low output at 90 degrees off-axis. Assume the dipole speaker is placed at the same distance from the front wall as the listener has to the wall behind him.

I give a formula in Ref. 2 and in Design Models A1 that relates the sound pressure level from a driver on an open baffle to the SPL from the same driver in an acoustically small closed box, assuming that both have the same cone excursion. frequency Fequal the SPL is the same for either driver arrangement. The open baffle driver output decreases at 6 dB/oct below this frequency relative to the closed box.

Ans. nil is the only instance of the class UndefinedObject and it is the default value for any new variable until a specific value is assigned to it.

A25 - A rear firing tweeter for the PHOENIX would increase the speaker's high frequency 4p acoustic output by 3 dB for an even more uniform power response. In earlier designs I actually used such a tweeter. Because of the physical size and separation of the two tweeters - in terms of wavelength - it is impossible to obtain a simple cos(a) polar response.

In general, use only high quality, digitally-recorded audio source material. If you are encoding material from a CD, try to record the file via direct digital transfer instead of recording through the analog input of your system's sound card. This can be done with standard tools such as QuickTime 4 Pro on the Mac, and with both commercial products and shareware tools on the PC. If you must record from an analog audio source, use the highest quality sound card available.

My MIDI playback is crackling no matter what SoundFont I use - what should I do? I have VIA chipset and AMD processor.

A34: Thank you for considering linking to us. Please visit our Link to Us page for linking instructions.

It is open to the public. The directions are as follows: From I-25 take exit 141 west. This will place you on Cimarron Street (also known as Highway 24). Travel west on Cimarron Street approximately 5 miles until you reach the Manitou Springs exit. Get off on the Manitou Springs exit-traveling west. This will take you under Cimarron Street. Turn right on Garden of the God's Place, i.e., the first street past the Cimarron Street overpass.

Physics. The trend in the world of powered subwoofers is to have big numbers out of small cabinets, and it doesn't matter what happens to acheive that end. Thus you have many "audiophile" subwoofers pumping out dirty, overly EQ'd bass. In reality, if you want clean bass, you have to have the cabinet size to allow for sufficient loading of the woofer cone--that's the physics part.

No. Most rear-facing car seats are not designed to be tethered. The top of the seat will be able to twist and rotate toward the back of the vehicle. This is normal. If the carseat rotates DOWNWARD into the seat cushion significantly, you may try to put your weight on it and install it a bit tighter.

Yes. The top of the monitor should be at eye level because the eyes are at their most comfortable position straight ahead but slightly downward. This is why reading lenses in bifocal glasses are placed just below the horizontal plane. This posture also makes it easiest to balance your head above your shoulders with the least muscular effort.

The recommended precast panel to panel joint width for architectural projects is 3/4". This is the minimum nominal joint width needed to adequately account for production and erection tolerances and still maintain an effective minimum joint width that can be caulked. A 30' long spandrel panel is allowed, per PCI tolerances up to a 1/4" variation in length. Keep in mind that of 3/8" is the minimum width that caulk suppliers will warrant.

Check the sight glass regularly. You should see a stream of bubbles when the system is running properly. Continuous foamy bubbles indicate low refrigerant level, no bubbles usually means no refrigerant. If your system is designed for R134a or R12, ensure only the proper gas is used to top-up/refill the system. No other gas can be used. Do run the system every week even during cold seasons for at least a couple of minutes. This ensures all rubber seals and pipes are kept well lubricated with oil.

A driver is software code that the video card manufacturer provides to implement the OpenGL and/or Direct3D software. In order for a program to use OpenGL/Direct3D to interact with your video card, the manufacturer has to provide a driver.