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Low Earth Orbit
DIY Audio
New DIY Mid High (90deg) - AKA PM90
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<blockquote data-quote="Frederik Mide-Andersen" data-source="post: 208442" data-attributes="member: 11975"><p style="text-align: left"><span style="color: #111111"><span style="font-family: 'Open Sans'"><span style="font-size: 14px">Hi guys,</span></span></span></p> <p style="text-align: left"><span style="color: #111111"><span style="font-family: 'Open Sans'"><span style="font-size: 14px">Peter, thank you for the inspiration starting of this journey of designing a derivative based on yours and some of my own findings/research.</span></span></span></p> <p style="text-align: left"><span style="color: #111111"><span style="font-family: 'Open Sans'"><span style="font-size: 14px">I've designed a version using two 15" (15NW76) in a sealed enclosure with the drivers facing the end panels through a short horn like adapter. </span></span></span></p> <p style="text-align: left"><span style="color: #111111">[FONT=&amp]<span style="font-size: 14px">I find it imperative to reduce the vertical source size in a MTM. Assuming we have DSP at our disposal, the sealed alignment using two large radiators with good excursion capabilities yields quite good low frequency efficiency (not unprocessed sensitivity though!). It is capable of 135db max spl down to 80hz 24dbLR, when applied eq, which is around the limit of the high frequency driver anyway. It's displacement limited, so those 135dB does not pull lots of power causing power compression and overheating. Unlike, the vented alignment having port noise and very delicate rear volume requirements, the LF output of the sealed alignment decreases at 12db/octave and can be adjusted as low as reasonable as long as one keeps an eye on the excursion below natural cutoff.</span>[/FONT]</span></p><p></p><p style="text-align: left"><span style="color: #111111"><span style="font-family: 'Open Sans'"><span style="font-size: 14px">Link to Don B. Keele's paper (part 1) on Linear phase crossovers and symmetric driver arrays (see MTM):</span></span></span></p> <p style="text-align: left"><span style="color: #111111"><span style="font-family: 'Open Sans'"><span style="font-size: 14px">http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2007-09%20AES%20Preprint)-%20Linear%20Phase%20Digital%20Crossover%20Flters%20Part%201.pdf </span></span></span></p><p></p><p>Here is a sketchup pic. The large cutout in the rear panel is to accommodate an amp module. The entire side and rear is made from a single piece of kerfed 18mm birch ply, to approach a cylindrical enclosure for good damping and minimized wall flex. The front panel is removable to access the 15"s and to allow different HF horn/driver combinations</p><p></p><p>I too considered every imaginable layout possible and ultimately arrived at this fairly simpel one. There is a lot of ways do such a speaker but only a few designs seems to obtain a good balance of requirements. This is just me trying to make anyone who is looking into designing their own version, avoid being blinded by a single design or idea</p><p>Best regards Fred</p></blockquote><p></p>
[QUOTE="Frederik Mide-Andersen, post: 208442, member: 11975"] [LEFT][COLOR=#111111][FONT="Open Sans"][SIZE=14px]Hi guys,[/SIZE][/FONT][/COLOR][/LEFT] [LEFT][COLOR=#111111][FONT="Open Sans"][SIZE=14px]Peter, thank you for the inspiration starting of this journey of designing a derivative based on yours and some of my own findings/research.[/SIZE][/FONT][/COLOR][/LEFT] [LEFT][COLOR=#111111][FONT="Open Sans"][SIZE=14px]I've designed a version using two 15" (15NW76) in a sealed enclosure with the drivers facing the end panels through a short horn like adapter. [/SIZE][/FONT][/COLOR][/LEFT][LEFT][COLOR=#111111][FONT=&][SIZE=14px]I find it imperative to reduce the vertical source size in a MTM. Assuming we have DSP at our disposal, the sealed alignment using two large radiators with good excursion capabilities yields quite good low frequency efficiency (not unprocessed sensitivity though!). It is capable of 135db max spl down to 80hz 24dbLR, when applied eq, which is around the limit of the high frequency driver anyway. It's displacement limited, so those 135dB does not pull lots of power causing power compression and overheating. Unlike, the vented alignment having port noise and very delicate rear volume requirements, the LF output of the sealed alignment decreases at 12db/octave and can be adjusted as low as reasonable as long as one keeps an eye on the excursion below natural cutoff.[/SIZE][/FONT][/COLOR][/LEFT] [LEFT][COLOR=#111111][FONT="Open Sans"][SIZE=14px]Link to Don B. Keele's paper (part 1) on Linear phase crossovers and symmetric driver arrays (see MTM):[/SIZE][/FONT][/COLOR][/LEFT] [LEFT][COLOR=#111111][FONT="Open Sans"][SIZE=14px]http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20(2007-09%20AES%20Preprint)-%20Linear%20Phase%20Digital%20Crossover%20Flters%20Part%201.pdf [/SIZE][/FONT][/COLOR][/LEFT] Here is a sketchup pic. The large cutout in the rear panel is to accommodate an amp module. The entire side and rear is made from a single piece of kerfed 18mm birch ply, to approach a cylindrical enclosure for good damping and minimized wall flex. The front panel is removable to access the 15"s and to allow different HF horn/driver combinations I too considered every imaginable layout possible and ultimately arrived at this fairly simpel one. There is a lot of ways do such a speaker but only a few designs seems to obtain a good balance of requirements. This is just me trying to make anyone who is looking into designing their own version, avoid being blinded by a single design or idea Best regards Fred [/QUOTE]
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