Dayton Budget Project MTM
Version
After the very warm
reception that the Dayton Budget Project received, many of you sent me mail
requesting an MTM version. This page chronicles the development of this
project, as it is currently a work in progress.
So far, I've created
numerous prototype baffles and enclosures, based on both the measured Thiel-Small
parameters of the Dayton 295-300 5 1/4" paper cone woofer and the simulated
design I created using the measured frequency and impedance responses of the
woofer and the Dayton 275-070 silk dome tweeter, which I've chosen to use in
this project, as part of the series of Dayton-driver projects I've developed
over the past few years. Concurrently, I'm developing variations on this
project. Once variation is a "2.5-way" version of this project.
Another is a 2.5-way using the Dayton woofers and the Vifa D27TG-05 tweeter.
Stay tuned for updates, as this project develops.
The
simulated crossover, shown on the left, is based on in-box measurements for the Dayton 295-300 and
Dayton 275-070 Silk Dome Tweeter (Gen 3). The front baffle of the box is
8.5" wide and the volume is .94 ft3. The
box tuning is 47hz. Full baffle step compensation is included. The
center-to-center spacing is 4 7/8", which is the minimum spacing possible
without overlapping the driver frames. This is a minor drawback inherent
in the faceplate design of the Dayton tweeter, as it dictates a maximum
crossover frequency of under 3khz. The optimum crossover frequency is at,
or below, the wavelength corresponding to distance separating the center of each
woofer and the center of the tweeter. The formula for calculating this
wavelength (λ) is as follows: λ= the speed of sound ÷ the
crossover frequency (hz). Conversely, to calculate the maximum crossover
frequency, in hertz, we divide the speed of sound by
λ, where λ is the center-to-center spacing of each
woofer and the tweeter. In this instance, therefore, the maximum suitable
crossover frequency is 13,500 in/sec ÷ 4 7/8", or
2769/sec, which is 2769 hz. With the Vifa D27TG-05, which has a smaller
faceplate, we can reduce the interdriver spacing to 4 1/2", which allows for a
crossover frequency of 3000 hz. While this may not sound like much of a
difference, in practice is helps to push the crossover frequency further up into
the audible spectrum, making the crossover less audible where out hearing is
most sensitive.
Also shown
on the left is the simulated response (Calsod Pro 3.10g). Measurements
were obtained with the CLIO measurement system using a gated MLS signal,
providing accurate results down to about 250 hz.
Additional
information will be posted as in-box measurements are obtained and the Calsod
model is put to the test for accuracy and further refined.
