Nearfield measurement with second order lowpass filter ( 10mH and 120uF )
The idea is simple:
remember an organ... Pipes, a lot of pipes. Small sized and sometimes very big ones.
So, i took a PVC tube with 8 inches diameter and 2 meters log, mounted a 8 inch woofer and tried to get some bass.
TSP of used woofer:
Vas: 98 liters
To calculate the resonant-frequency of this 2 meter tube:
fs = c / ( 4 * l )
c = 344 meters ( speed of sound )
l = length of tube in meters and 4 because is a quater-wave-pipe
Resonant frequency of the pipe = 344 / ( 4* 2 ) = 43 Hz
Impedance ( no filter and no filling )
Impedance ( with filter and filling )
Second OrdProjects/er ( 12dB ) crossover
Bowers & Wilkins Compact Domestic Monitor 1
I was long searching for B & W Loudspeakers. Now I've found what I was looking for: B & W CDM 1.
Voted "Loudspeaker of the Year" by European journalists in 1995.
B&W is an example of a company that got very big by doing things right, and still does.
They manufacture their own drivers. Quality control is tops.
The CDM 1 exudes quality. Cabinetry is first-rate. The black ash finish looks stunning in my living room.
The CDM 1 is a two-way design rated at 88dB/2.83V/m sensitivity.
Nominal impedance is rated at 8 ohms, going down to a minimum of 4.5 ohms.
Electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.)
Notice the bullet-shaped nose cone smack in the middle of the woofer's voice-coil, in lieu of a dustcap. B&W calls it a "dispersion modifier."
There's only so much bass you can get from a small speaker, but the CDM 1 does very well, except for the lowest octave.
Better banish that lowest octave than have the deep bass shake the cabinet and muddy the sound! You could always mate the CDM 1 with a good subwoofer.
The bass performance is very much dependent on the amplifier.
Anechoic response on tweeter axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with complex sum of nearfield woofer and port responses plotted below 300Hz
Step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth)
The enclosure is constructed from 3/4" MDF, and is made rigid by a vertical brace at the sidewall centers. I want to call this a "figure-8" brace, except that it has three rather than two holes. The cabinet walls are lined with 1" foam. The reflex port, almost 2" in diameter and 6" deep, is situated on the front baffle immediately beneath the woofer and is flared to minimize wind noise.
The High Frequency unit is a metal-dome unit descended from the 1" tweeter used in B&W's classic Matrix 801 design. The 6.5" woofer features a yellow cone formed from Kevlar, the synthetic material used in bulletproof vests. The woofer cone is also surrounded by a circular plastic molding to minimize reflections. The tweeter is covered with a black wire mesh, the woofer and port with an elliptical grille made from black cloth stretched over a minimal plastic space frame.
The crossover is set at 3kHz, with the circuit mounted on a small printed circuit board attached to the inside of the inset plastic terminal panel. The woofer low-pass filter appears to consist of a single soft-iron-cored series inductor, while the tweeter high-pass filter, a damped T section, features an air-cored inductor and non-polar electrolytic capacitors.
Dimensions: 15" (381mm) H by 9" (229mm) W by 11" (280mm) D.
Weight: 18 lbs each.
I discovered that standard low-cost components were used in the cross-over.
The problem is on the capacitor. These are expected to age significantly. An increasing fatigue in the heights I could definitely identify with the years.
I like the Chario Syntar 200 Tower and this speaker is not expensive!
dB SPL 2.83V/1m Frequency @ -3dB: 55 Hz Acoustic Allignment: LR4-Like * Rated Impedance: 4 Ohm Configuration: 3
way vertical array Size: 960x210x300 Weight: 20kg
* Fourth order Linkwitz-Riley crossovers (LR4) are probably today's most standard
type of audio crossover. They are constructed by cascading two second order Butterworth
filters. Their steepness is 24dB/octave (80 dB/decade).
This Horn Speaker is build in 2001 (just for fun and my EL84 Amp)
E.J. Jordan horn with only one transducer the entire audible frequency range to show, is the probably most fastidious goal of a loudspeaker chassis developer.
The broadband loudspeaker chassis JX92 of Ted Jordan supplies a smooth frequency response with its light and rigid aluminum diaphragm up to 20kHz.
As housing for this transducer a bass horn is the best solution. A horn loudspeaker is with correct adjustment to the driver easily in a the position to improve the efficiency around the factor 10 which corresponds to a level gain of 10 decibels.
The loudspeaker must be aligned both horizontal and vertically for hearing position, since the JX92 bundles the sound clearly starting from 4kHz.
In addition the housing at the front edge can be placed on spikes.
The position in the area is uncritical: During hitting a corner list the bass becomes more pressureful, in addition, before a wall or freely set up bass is present in sufficient quantity.
Very pressureful and precise the bass of the E.J. Jordan horn sounds, whereby extreme low bass is missing.
From the middle bass situation upward into the basic clay/tone range the loudspeaker supplies with to very much pressure, to be dosed by the damping of the horn.
dB SPL 2.83V/1m Frequency @ -3dB: 45 Hz Rated Impedance: 8 Ohm Size: 85cm
x 24cm x 50cm Weight: 28kg
At this time i used a Tubeamp (based on the EL84) with only 6 Watt per chanel.
The used driver is the famous Jordan JX92
At the moment i'm busy to update this loudspeaker
a tweeter will be added ( 4kHz - 20kHz )
new impedance & frequency measurements
the crossover network has to be designed
the notchfilter (150Hz problem) will be recalculated
All measurements and new pictures coming soon ( 2-3 weeks )
For years and years I was using standart speakercable...
Now I bought something good (for a good price) ;-))
Four brown and four black braided conductors
2 x 14awg / 2.08mm2
Special formula polyethylene dielectric.
The performance of 4PR is evident on even the most modest systems. With 4PR, bass
and treble frequencies are allowed their full extension, while dynamics emerge unrestrained.
Through the use of our proven braided technique, 4PR rejects noise regardless of
length, making it an excellent cable for professional, studio and home use.
Because a Subwoofer is used, f-3dB @ 130 Hz is perfect...
180 x 320mm
156 x 320mm
120 x 180mm
12cm x 18cm x 24cm
Vb = (5.18ltr - DrviverVol = 0.3ltr)
New Network: 12dB Crossoverfrequency (acoustical: 2.5kHz, electrical: 1.7kHz)
The network is totaly recalculated. One capacitor is not working...
Now it's a 12db network with impedance compensation for Midwoofer and Tweeter. There are problems at 6.5 kHz and 10kHz.
This is caused by the Tweeter...
But i don't change this because the network components would be 4 times the money as the both drivers...
And, the speaker is used as PC loudspeaker and not as HiFi loudspeaker.