OK guys so another update on the baffle project.
After I had completed the new frames Chris came over for a listen and thought the more powerful bass from the deeper side frames was to him swamping the lower mids some. So we did some experiments with attenuating the bass with a inline resistor placed before the 8.2mH inductor of the low frequency filter. After trying a few values we arrived at a value that to our ears seemed to address the midrange issues that Chris commented.
I reported this back to Scott to which he commented that the resistor mod is perhaps not the best way to address the midrange swamping issue and suggested a 22uF cap placed before the first inductor of the bass section of the coax driver a better solution and or try replacing the 8.2mH inductor with a 5.6mH. Doing this one component change at a time and listen to which sounds best. So I ordered a couple the Monacor 5.6mH Transformer Core Coils having some 22uF polyprop caps in stock.
In the interim Scott had sent me the 2-way passive filter to mimic the mini DSP experiments that Nick carried out late last year. Having ordered the components from NickL at HFC these had arrived earlier in the week and set about building these into a spare ply boxes I had from a previous mock-up build. Photo below:
Thursday evening Chris came over to try the new 2-way filter and 3-way baffle minor XO mods suggested by Scott. First we tried the 22uF cap on the bass section of the coax to reduce the amount of lower frequencies generated by the coax driver. We both thought this an improvement on our ill informed attempts at addressing the over bass issue. So out came the 22uF cap and the 8.2mH inductor replaced with the 5.6mH. Chris almost instant response to this change was on the lines 'that's nailed it. The changes though both gave improved results were quite interesting and have nailed the sound the 3-way baffles and increased further my understanding of how filter work. So apart from painting the new frames matt black the 3-way baffles are sorted.
Next we replaced the coax driver baffles with the compression driver/horn baffles and hooked up the new 2-way passive filters.
Wow! We were both blown away how good these sounded apart from some harshness of the high frequencies - cymbals and the like. We were using NickG's P6 amps and both thought that good as the P6 amps are they perhaps were not the best choice for with what are near 100dB efficient 2-way speakers. So the P6's were replaced with my 300B SET amps.
This nailed the combination and Chris commented that originally he was not that impressed with the sound quality of mini DSP experimental set up for the 2-way baffles but this Scott passive filter is something else. I have to agree. Scott has done wonders with this filter and it just goes to confirm my suspicions that the mini DSP modules are adding colouration to the detriment of the sound quality and that a well designed passive filter with quality components will better an all digital DSP XO. Perhaps the new generation of DSP modules are better in the sound quality department?
Having spent most of yesterday listening to different genres of music through the 2-way baffles with the 300B amps I can hear still some harshness and shrill from the very high frequencies through the horn. One some my torture tracks cymbals can be a little too much. Scott has promised a minor mod to the high pass filter to address this but before that suggested I try a different horn. The one I have installed (Monacor MRH-200) Scott says was really designed for PA use and has suggested a more modern design horn in the Monacor MRH-180 might address the minor HF shrillness without having to mod the filter.
The specs for this are:
PA mid-high range horn
• Diecast aluminium horn
• Resonance-free due to rubber elements used
• Can be mounted turned by 90°
• 25 mm (1") flange connection with standard 2-hole screw connection (hole spacing: 76 mm)
• Consistent radiation pattern due to the latest FEA and CAD 3D developments
• Frequency range 1,000-20,000
• Mounting cutout 155mm dia.
• Mounting depth 86mm
• Radiation angle (vert./hor.) 50deg/70deg
• Dimensions 180x180x90mm
So I have a couple these on order and shall be making up some new mounting baffles.
So watch this space for further development updates.