Even though my Grand Heil MEH project is still not finished, I just had to buy the GRS PT6816-8 planar drivers since they could be a base of a more "living room friendly" MEH / Synergy with a single or maximum two mid/bass drivers. My thoughts on the design:
1) The woofer. While playing around in Hornresp, I have no problem with the upper end of the mid driver(s). What I cannot really simulate is the low end response. I discovered the LaVoce WSF081.82-8, which seems to be a suitable driver for the task. I am simulating the worst case port distance and up to 10" sized driver could be used. I am really lost here and I do not know what should the ideal parameters be for a two way MEH woofer. The crossover will be DSP and ideally, I would like the horns to be able to play on their own, they would be helped by a mono subwoofer if needed, sort of a 2.1 system.
2) Coverage angles. The planar driver will beam vertically - that is common knowledge - but from which frequency and how severe is that? That would dictate the vertical coverage. Other projects using planar drivers on horns choose usually 30 - 40 degrees, and 30 degrees seems to work fine on my AMT based project. When listening, I do not really move vertically, so narrow vertical dispersion would not be a problem. Horizontally, I see typically something between 60 and 90 degrees, with the preference closer to 90 degrees. A 80 H x 30 V pattern should work fine.
3) Secondary flare - yes or no. Reading of other builders' experience gives me the impression that a secondary flare is not really necessary. Not having one makes the build easier. Would it make any sense to make a secondary expansion in one direction only? What would then be the preference - dual expansion horizontal or vertical and why? I am considering if large radius a la onni's compact Synergy would be a better option - at least visually it looks good, athough I have no issue with the classical bwaslo-spreadsheed-designed style look.
4) Size. I would be glad if the resulting box could be about the size of a Bose 901 cabinet, SPL Runt outer dimensions being the absolute limit. I see that the Hornresp record I posted is quite larger than that.
Any input on the topic will be welcome as this project is in a very early stage and as usual with my other projects, it will take quite a long time before it will materialize🙂
1) The woofer. While playing around in Hornresp, I have no problem with the upper end of the mid driver(s). What I cannot really simulate is the low end response. I discovered the LaVoce WSF081.82-8, which seems to be a suitable driver for the task. I am simulating the worst case port distance and up to 10" sized driver could be used. I am really lost here and I do not know what should the ideal parameters be for a two way MEH woofer. The crossover will be DSP and ideally, I would like the horns to be able to play on their own, they would be helped by a mono subwoofer if needed, sort of a 2.1 system.
2) Coverage angles. The planar driver will beam vertically - that is common knowledge - but from which frequency and how severe is that? That would dictate the vertical coverage. Other projects using planar drivers on horns choose usually 30 - 40 degrees, and 30 degrees seems to work fine on my AMT based project. When listening, I do not really move vertically, so narrow vertical dispersion would not be a problem. Horizontally, I see typically something between 60 and 90 degrees, with the preference closer to 90 degrees. A 80 H x 30 V pattern should work fine.
3) Secondary flare - yes or no. Reading of other builders' experience gives me the impression that a secondary flare is not really necessary. Not having one makes the build easier. Would it make any sense to make a secondary expansion in one direction only? What would then be the preference - dual expansion horizontal or vertical and why? I am considering if large radius a la onni's compact Synergy would be a better option - at least visually it looks good, athough I have no issue with the classical bwaslo-spreadsheed-designed style look.
4) Size. I would be glad if the resulting box could be about the size of a Bose 901 cabinet, SPL Runt outer dimensions being the absolute limit. I see that the Hornresp record I posted is quite larger than that.
Any input on the topic will be welcome as this project is in a very early stage and as usual with my other projects, it will take quite a long time before it will materialize🙂
Hi pelanj, wish i could help more. I don't have any experience with smaller MEH builds.
The smallest i've made was a 34" x 20", 90x60, without secondary flares.
It was (is) a stunningly good box given the inexpensive drivers in it...two 10fe300's and four 4fe35's.
Well, inexpensive other than a high $ CD. But i think a low $ CD would work just as well, because xover to mids could easily be up at 1-1.2kHz.
And i certainly have no experience with using a planar ...but i'll definitely be watching what you do 🙂
The smallest i've made was a 34" x 20", 90x60, without secondary flares.
It was (is) a stunningly good box given the inexpensive drivers in it...two 10fe300's and four 4fe35's.
Well, inexpensive other than a high $ CD. But i think a low $ CD would work just as well, because xover to mids could easily be up at 1-1.2kHz.
And i certainly have no experience with using a planar ...but i'll definitely be watching what you do 🙂
The RADIAN LM8K has the same vertical dimension and has polar data that indicates even at +/-15 degree vertical weird stuff is happening, I think with this type of driver they are like beam at high frequency. The usable frequency range for the GRS PT6816-8 is indicated as down to 320Hz and fs looks to be around 400Hz so it should be very easy to meet a 10" driver. If compact size is a priority you could try no secondary flare and instead using foam absorption.
So I just started with a simple horn ca 80 x 30 and a central hole for a 170 mm woofer. External dimensions are roughly as Bose 901. If I will be happy with the sound, they will turn into proper boxes.
For the low end woofer response (the maximum DSP boost) will be determined by the frequency, x-max, SD, and desired SPL. I don't have that formula. I think Linkwitz site has an excel spreadsheet like spl_max that may help. With the volume displacement (x-max*SD) you may want to check that the tap velocity does not cause chuffing (aka port noise).
My MEH did not have a secondary flare. I occasionally have some honk. I'm told I need a smoother exit transition to eliminate the honk.
My MEH did not have a secondary flare. I occasionally have some honk. I'm told I need a smoother exit transition to eliminate the honk.
I use the MaxSPL function in Hornresp, that one shows the maximum SPL limited by x-max and available power - and it also shows the max velocity. Here the transition will be smooth - it is rectangle to rectangle🙂
