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In the Forum: Horn-Loaded Speakers
In the Thread: A Frankenstein Macondo - Injection channel - trying it as open baffle.
Post Subject: A Frankenstein Macondo - Injection channel - trying it as open baffle.Posted by Rewind on: 7/2/2013
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Hi,
I am slowly building my own Macondo. I understand why the injection channel is there. It brings some kind of softness that the compression drivers lack.
I am using a 12" JBL midbass driver (~100dB sensitivity) in a 50L single driver Marshall cabinet, that I have turned into a U-form open baffle (with a roof). The difference between sealed and U-form open baffle above 150Hz was huge! Everything becomes more open and relaxed, no more muffled bass distortion, as can be heard from many cheap vented or sealed home theater subwoofers. I do have to use a lot of EQ to get bass, which I am not sure I can live with. It is probably better to get a dedicated subwoofer. The tricky part will be to fit a sealed sub to an open baffle midbass injection channel. The dispersion is very different, and a lot other things that I don't grasp yet are probably also different.
I did however confirm my worries that the 2" Radian driver I am using would be much faster. Overlapping both drivers sound wrong. I will try my best to time align them. We might be using them differently. I can still hear my injection channel a little at 2500-4000Hz.
Onto another open baffle dipole experiment in my Frankenstein Macondo:
I have also tried to exchange the 1" Beyma compression driver in a small AG Trio horn, for a Beyma TPL-150, with mixed results. The TPL-150 sounds very pleasant to the ears in chaotic music, but I prefer to use the 1" CD and just stop listening to music not scored for horns. It is a more rewarding experience. It should not be my job to fix badly recorded material with forgiving speakers like the AMT.
Switching between 1" CD and TPL-150 is like listening to live music, versus dead music. The TPL-150 is very analytical, and accurate, but I am not as involved in the music.
The Beyma TPL-150 is also in a smaller U-form open baffle dipole, because it sounded best like this. More open and relaxed. A little less sensitivity and probably less midrange, but I am okay with that. Taking off the back chamber did not change my bored impression of it.
I wish I could be this black and white always, but sometimes I do listen to popular music. Therefore I will try my best to build a bass AMT to better fit with the TPL-150, than the 2" horn. These horn speakers are more like instruments. You don't try to play angry electronica with a bass tuba. I guess I just need a second pair of speakers for those days when angry electronica is high on the playlist.
I am also building a GOTO horn for the 2" in wood. Because I can. 
I just have to hear the difference between Avantgarde Trio type midrange horns and the GOTO. Progress is slow, but one half is done. Will report back. 
BTW, thanks for the idea with the RAAL supertweeter. I am using a Transmission Audio 50cm long/1" wide ribbon that plays heaven. I suspect that there is not that much difference between ribbon drivers. They are so similar, the design so simple. Right now I am trying out a transformeless setup using a pencil as a graphite resistor instead of ribbon driver transformer, inspired by Duelund resistors.
I know a lot of people are against open baffle in this forum, and I get why phase and reflections could be a problem. But I also have ears, and this just sound better than the sealed enclosure i lived with before. It is possible your Tannoy Red 10" won't cut it as an open baffle driver. It needs a lot of excursion and large area. My 12" JBLs are actually too small and have too low Xmax. Best drivers would be the 21" Beyma's. Some use them in dipole line array with high pass 200Hz.Rerurn to Romy the Cat's Site