Let me introduce you to the Trynity (Trynergy was already taken🙂 ). This is just a simple horn shell with interchangeable plates for injection holes to try out various drivers I have at hand. As simple to build as possible. There will be one built for a compression driver with the adaptor shown above and the second will be with ESS Heil AMT-1 at the apex (that is the beauty of parametric models, it will require to change a few numbers only). First, the plan is to test how large can the midrange be to cross over still smoothly to the HF driver. My secret weapon is the BC 8PE21 which should work fine with a small back chamber. As I am not going for extreme SPLs, there will be a single or dual mid on top and a single 15" for bass on the bottom (the pics are 90 degrees rotated). There is also an option to fit some smaller mids on the sides.
I plan to build these from 16 mm chipboard. Once happy with the testing results, the final pair will be built.
I plan to build these from 16 mm chipboard. Once happy with the testing results, the final pair will be built.
Inspired again by mark100's experiments, it seems that a full range MEH can be built. This is some preliminary simulation with a cheap 18" woofer for lows (grey, at ~100 W) and BC 8PE21 for mids (black at ~40 W). I know the 8PE21 can do a little better at the high end from my SPL Runt clone build. 800 Hz crossover should be no problem. The 18" would be mounted from the bottom with the bass reflex port below the horn mouth, the 8PE21 from the top inside a small chamber. The total volume occupied by the box would be around 250 l and it should not be too heavy. And with more power, it should be able to do 120 dB / 1m with more power down to 35 Hz. So the Trynity will be built in a size that would allow mounting of a 18" woofer as well.
Back in the day, I prototyped a MEH with 8" mids. 800 Hz was about the limit. With an injection hole near the surround of the mid is you get cancellation there from the far side of the cone, causing roll of higher frequencies. You may need a volume reduction plug between the cone and the horn wall to get that high. In my proto, I included a volume plug and tunneled through it so sound entered the plug near the dustcap and exited to the injection hole near the surround/cone edge. With this, I was able to get up to 1400 Hz. But the mounting depth of the 8" driver was too high to work in a corner horn and so I went ahead with 2 4" drivers instead of two 8".
This is my measurement of the 8PE21 on the Runt clone (without a back chamber):
Without any volume plug - it looks more like 700 Hz, but that is still OK for Beyma CP755Nd and a breeze for BC DCX464.
Do you maybe have a picture of your volume plug? I have hard time visualizing it. Do I understand correctly, that there are two holes leading to the inner edges of the horn? I plan to use multiple adaptor plates, so I can experiment with placement of the injection holes - I have had some good results with using just a central hole below the dustcap. I did not save the HF/LF measurements, but the second crossover was definitely above 800 Hz (https://www.diyaudio.com/community/threads/ikea-kallax-meh-unity-synergy-speaker.382400/post-7204108)
Without any volume plug - it looks more like 700 Hz, but that is still OK for Beyma CP755Nd and a breeze for BC DCX464.
Do you maybe have a picture of your volume plug? I have hard time visualizing it. Do I understand correctly, that there are two holes leading to the inner edges of the horn? I plan to use multiple adaptor plates, so I can experiment with placement of the injection holes - I have had some good results with using just a central hole below the dustcap. I did not save the HF/LF measurements, but the second crossover was definitely above 800 Hz (https://www.diyaudio.com/community/threads/ikea-kallax-meh-unity-synergy-speaker.382400/post-7204108)
Surprisingly I do. First two photos show the volume plug with a top hat that attempted to equalize path lengths going into the tunnel through the truncated cone shape. The top hat may not have been necessary. In the third photo you can see the tunnel leading off to the edge of the cone. This was created by excavating mdf from the underside. The cone covers the injection hole through the horn wall so you can't see it here.
Attachments
News... did anyone use these kind of drivers in a MEH? Usable? 150Hz ->
https://audioxpress.com/news/radian...ide-band-planar-ribbon-transducer-at-ces-2023
Probably quite costly...
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https://audioxpress.com/news/radian...ide-band-planar-ribbon-transducer-at-ces-2023
Probably quite costly...
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Not exactly these, but I build some MEHs with planar drivers: https://www.diyaudio.com/community/threads/ikea-kallax-meh-unity-synergy-speaker.382400/ and https://www.diyaudio.com/community/threads/ess-amt-1-in-my-projects.349546/post-6891749
Radian says 250 USD a piece, not bad. But I think it is too large and the top end is not so nice. The AMT-1 is about the same cost and sounds really good. The only problem is it shape/form, that makes it difficult for mounting on a horn.
Radian says 250 USD a piece, not bad. But I think it is too large and the top end is not so nice. The AMT-1 is about the same cost and sounds really good. The only problem is it shape/form, that makes it difficult for mounting on a horn.
I keep fantasizing about complex phase plugs for woofers on MEH, after all they are just offset driver horns. thanks for sharing your design.
With a bit of playing around with EQ, one can get this in Hornresp:
Total system volume (net) was reduced to 230 l, which is still big, but not too big🙂
Total system volume (net) was reduced to 230 l, which is still big, but not too big🙂
After thinking about the layout, I actually need to put the ports on the sides - otherwise I could not access the woofers. That means I need to make the horn a bit narrower, so that the full box is not too wide.
The other option is to place the ports on the corners. I am not sure I am brave enough to do that🙂
The other option is to place the ports on the corners. I am not sure I am brave enough to do that🙂
Reading again Scott Hinson's article on his MEH build, there is no reason not to place the ports to the back. That should actually work fine and they will not make the box wider.
I was going to say something earlier. Ports in the corners were the standard until Mark100 found that ports in the center of the flare worked better for large woofers. Danley believes they are less disruptive to the polar pattern there; still the way to go for mid ports.
Yesterday I found out, that it is not that easy to fit one 18" to the underside of the horn, so the latest one is 85x65 with 90 cm wide mouth based on datasheet dimensions. I will get the woofers on Tuesday, so I will be able to measure them more precisely. I will need an extension on the bottom as mark100 did need on the sides, so the bass reflex ports will be placed there and there will be still a comfortable place for a 500 mm wide access panel.
This is what I got with EQ and first order LP/HP on the mids. There is no LP on the bass, the slope is done by EQ. This is at 100 W to the woofer and the mids at a roughly matched level. I think this shows the potential nicely. I would like to send my thanks to @mark100, @Cask05 and all who contributed to my thread https://www.diyaudio.com/community/...sign-properly-using-dsp-please-advise.383231/ for instructions on how to use EQ to create the required acoustic slopes, after looking at the FRs in Hornresp (thanks also to @David McBean for this great software!), it all suddenly started to make sense to me
I am limited by the capabilities of my small DSP, and even with the limitations, it seems I can get really close to a perfect result.
Now back to the CAD, get some chipboard and build the Trynity🙂
I am limited by the capabilities of my small DSP, and even with the limitations, it seems I can get really close to a perfect result.
Now back to the CAD, get some chipboard and build the Trynity🙂
@TNT Hadex Q378 (datasheet here https://hadex.cz/spec/q378.pdf). It is relatively cheap and has a low fs. Its performance is reported to be pretty good by the local guys. For serious PA, it is not really suitable, there are much better drivers that can be used in smaller volumes - it seems to fit my purpose though.