Bipolar MLTL Speaker with FR125S/WR125S
I recently completed a bipolar MLTL using the CSS FR125S as the front driver and the WR125S as the rear driver. The connection of the two drivers in each box is in phase so that a bipolar field (forward and rear radiation) is created.
The box duplicates Greg Monfort's (GM) design that he describes in his posting:
http://www.diyaudio.com/forums/showthread.php?postid=672120#post672120
I built Greg's MLTL design that is the 45 Hz and +/- 1 dB. The drivers are located 14" internally below the top of the box. I lightly stuffed the top of the box (from below the drivers). The port tube is on the rear of the speaker and just above the bottom floor of the MLTL line. The drivers are positioned about 33.25" above the floor. I located the terminal plate in a cavity at the bottom of the enclosure. The cavity spaces the drivers upward to their listening position plus allows room to add mass to stabilize the box. Also any contouring components, if needed, could be located in this cavity.
The enclosure was constructed of 0.75" thick MDF panels for the baffle, rear, and bottom of the box with walnut top and side panels. Internally, three braces are used to stabilize the structure. The outside dimensions of the enclosure are 48" high, 7.5" wide, and 8.75" deep.
The sound of these speakers is very nice indeed with more bass than you would expect from the volume. The four drivers do a nice job in adding low end impact to your music. The frequency response of these drivers is very flat across the band and this design retains this benefit. More important these speakers exhibit the coherent nature that we have come to expect from quality full range drivers without a crossover.
The bipolar drivers in these speakers necessitate that you position them away from the wall--I'm using 3 feet in my room. Their bipolar nature of this speaker does two things that you will notice to your listening. First, you'll notice a little ambiance as sound energy is reflected from the back wall in the room. In this case ambiance is a good thing--more apparent during say a newscast--but with not an issue when you listen to music. Secondly, the soundstage is wider than you'll have with just a single front firing driver. One very minor disadvantage to the bipolar nature of these speakers is that the stereo image is a little more diffuse than with direct firing drivers. In my opinion having a wider sweet spot is an advantage in my book.
The FR125S full range driver does an excellent job across the frequency band and for most music you'll not miss any extra airyness that a separate tweeter might contribute.
Bottom line is that this is a very simple design yet it yields great results. A lot of bang for their cost.
Jim
I recently completed a bipolar MLTL using the CSS FR125S as the front driver and the WR125S as the rear driver. The connection of the two drivers in each box is in phase so that a bipolar field (forward and rear radiation) is created.
The box duplicates Greg Monfort's (GM) design that he describes in his posting:
http://www.diyaudio.com/forums/showthread.php?postid=672120#post672120
I built Greg's MLTL design that is the 45 Hz and +/- 1 dB. The drivers are located 14" internally below the top of the box. I lightly stuffed the top of the box (from below the drivers). The port tube is on the rear of the speaker and just above the bottom floor of the MLTL line. The drivers are positioned about 33.25" above the floor. I located the terminal plate in a cavity at the bottom of the enclosure. The cavity spaces the drivers upward to their listening position plus allows room to add mass to stabilize the box. Also any contouring components, if needed, could be located in this cavity.
The enclosure was constructed of 0.75" thick MDF panels for the baffle, rear, and bottom of the box with walnut top and side panels. Internally, three braces are used to stabilize the structure. The outside dimensions of the enclosure are 48" high, 7.5" wide, and 8.75" deep.
The sound of these speakers is very nice indeed with more bass than you would expect from the volume. The four drivers do a nice job in adding low end impact to your music. The frequency response of these drivers is very flat across the band and this design retains this benefit. More important these speakers exhibit the coherent nature that we have come to expect from quality full range drivers without a crossover.
The bipolar drivers in these speakers necessitate that you position them away from the wall--I'm using 3 feet in my room. Their bipolar nature of this speaker does two things that you will notice to your listening. First, you'll notice a little ambiance as sound energy is reflected from the back wall in the room. In this case ambiance is a good thing--more apparent during say a newscast--but with not an issue when you listen to music. Secondly, the soundstage is wider than you'll have with just a single front firing driver. One very minor disadvantage to the bipolar nature of these speakers is that the stereo image is a little more diffuse than with direct firing drivers. In my opinion having a wider sweet spot is an advantage in my book.
The FR125S full range driver does an excellent job across the frequency band and for most music you'll not miss any extra airyness that a separate tweeter might contribute.
Bottom line is that this is a very simple design yet it yields great results. A lot of bang for their cost.
Jim
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It can also use a standard port, which will be in the base and downward facing with a couple of inches floor clearance.