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New DIY Mid High (90deg) - AKA PM90
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<blockquote data-quote="Peter Morris" data-source="post: 132748" data-attributes="member: 652"><p>Re: New DIY Mid High</p><p></p><p></p><p></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000">The first plots were all “brick wall” and used 12.5ms of FIR time.</span></span></span></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000"></span></span></span></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000">The last plots used 2.5 ms FIR time; they were as follows:-</span></span></span></p><p></p><p><span style="color: #000000"><span style="font-family: 'Calibri'"><span style="font-family: 'Calibri'"><span style="font-size: 12px">-</span></span> </span><span style="font-family: 'Calibri'"><span style="font-size: 12px">HF 6300Hz - brick wall</span></span></span></p><p><span style="color: #000000"><span style="font-family: 'Calibri'"><span style="font-family: 'Calibri'"><span style="font-size: 12px">-</span></span> </span><span style="font-family: 'Calibri'"><span style="font-size: 12px">MID 700Hz - brick wall. Only about 20dB per octave with that FIR time. You could use a 48 dB LR linear phase simulation but the directivity plots are not as good.</span></span></span></p><p><span style="color: #000000"><span style="font-family: 'Calibri'"><span style="font-family: 'Calibri'"><span style="font-size: 12px">-</span></span> </span><span style="font-family: 'Calibri'"><span style="font-size: 12px">LOW – 100Hz IIR LR 24 dB per octave.</span></span></span></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000"></span></span></span></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000">The LOW section of the BMS4594 uses 4 all pass filters to flatten the phase and some out of band filters. The 12 inch MIDS uses four filters, two out of band. The VHF driver is polarity inverted.</span></span></span></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000">While all bands have some in- band EQ, apart from a reasonable large cut at 400Hz as predicted by Hornresp simulation not much EQ is used to get a flat response.</span></span></span></p><p><span style="font-size: 12px"><span style="color: #000000"><span style="font-family: 'Calibri'"></span></span></span></p><p><span style="font-size: 12px"><span style="color: #000000"><span style="font-family: 'Calibri'">There are also a bunch of small raised cosine filters applied to the overall response to make the frequency response look like it was drawn with a ruler.</span></span></span></p><p></p><p><span style="font-family: 'Calibri'"><span style="font-size: 12px"><span style="color: #000000">The first, all FIR settings required two Lake LM26s, one for each channel. The most recent settings allows the MID – Hi box to run with one LM26 and any other DSP for the subs. An all pass filter is used on the subs so their phase response is identical to the low mid through the crossover region,but it’s not critical.</span></span></span></p><p></p><p><span style="font-size: 12px"><span style="color: #000000"><span style="font-family: 'Calibri'">Having described this complex crossover, the BMS driver has a very flat frequency response without EQ. BMS can supply a passive crossover for the driver so the box could be run two ways. The double 12” mid only requires two or three filters to produce a good response, so most DSP’s could be used to achieve a good response. </span></span></span></p></blockquote><p></p>
[QUOTE="Peter Morris, post: 132748, member: 652"] Re: New DIY Mid High [FONT=Calibri][SIZE=3][COLOR=#000000]The first plots were all “brick wall” and used 12.5ms of FIR time. [/COLOR][/SIZE][/FONT] [FONT=Calibri][SIZE=3][COLOR=#000000]The last plots used 2.5 ms FIR time; they were as follows:-[/COLOR][/SIZE][/FONT] [COLOR=#000000][FONT=Calibri][FONT=Calibri][SIZE=3]-[/SIZE][/FONT] [/FONT][FONT=Calibri][SIZE=3]HF 6300Hz - brick wall[/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Calibri][FONT=Calibri][SIZE=3]-[/SIZE][/FONT] [/FONT][FONT=Calibri][SIZE=3]MID 700Hz - brick wall. Only about 20dB per octave with that FIR time. You could use a 48 dB LR linear phase simulation but the directivity plots are not as good.[/SIZE][/FONT][/COLOR] [COLOR=#000000][FONT=Calibri][FONT=Calibri][SIZE=3]-[/SIZE][/FONT] [/FONT][FONT=Calibri][SIZE=3]LOW – 100Hz IIR LR 24 dB per octave.[/SIZE][/FONT][/COLOR] [FONT=Calibri][SIZE=3][COLOR=#000000] The LOW section of the BMS4594 uses 4 all pass filters to flatten the phase and some out of band filters. The 12 inch MIDS uses four filters, two out of band. The VHF driver is polarity inverted.[/COLOR][/SIZE][/FONT] [FONT=Calibri][SIZE=3][COLOR=#000000]While all bands have some in- band EQ, apart from a reasonable large cut at 400Hz as predicted by Hornresp simulation not much EQ is used to get a flat response.[/COLOR][/SIZE][/FONT] [SIZE=3][COLOR=#000000][FONT=Calibri] There are also a bunch of small raised cosine filters applied to the overall response to make the frequency response look like it was drawn with a ruler.[/FONT][/COLOR][/SIZE] [FONT=Calibri][SIZE=3][COLOR=#000000]The first, all FIR settings required two Lake LM26s, one for each channel. The most recent settings allows the MID – Hi box to run with one LM26 and any other DSP for the subs. An all pass filter is used on the subs so their phase response is identical to the low mid through the crossover region,but it’s not critical.[/COLOR][/SIZE][/FONT] [SIZE=3][COLOR=#000000][FONT=Calibri]Having described this complex crossover, the BMS driver has a very flat frequency response without EQ. BMS can supply a passive crossover for the driver so the box could be run two ways. The double 12” mid only requires two or three filters to produce a good response, so most DSP’s could be used to achieve a good response. [/FONT][/COLOR][/SIZE] [/QUOTE]
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