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In the Forum: Horn-Loaded Speakers
In the Thread: MacondoLite
Post Subject: Macondo-clone ramblingsPosted by ayebee on: 8/20/2009
The system is still very much a work in progress, but I have come to the conclusion that the concept as such is very, very good. It's only up to me to make it sound as well as I know it is capable of. Making and fine-tuning the crossover might take me a few years, but I can live with that.
I chose a 3” throat on the 140Hz horn for the exact reason that Romy points out. I wanted the horn to work as a horn with a minimum of direct radiation from the driver. Apparently, using 4” throats on 140Hz Tractrix-horns seems to work in real life. Maybe I was too “ambitious” in my choice, since the 3” throat might disqualify using 8” drivers, but maybe I should try the Fane 8M anyway – I have a pair in stock. The present Fane-driver I do not recommend, it has decent sensitivity, but the highish Qts (0,47) is not suitable to horn loading, resulting in a (relatively) dull and slow sound. I have recently found the 18-sound 6NMB420 which might fit the bill – but as Romy points out, the search might take some time.
The 2440 is a fine driver, but my experiments so far indicate that it can’t be used “full-range” in a home-environment. The 2440 on it’s own in the 250Hz-horn (44 cm diam) with no low-pass filtering was in no way a pleasant experience – very unsophisticated and harsh. I will definitely try using it in an even narrower range. Still – in the present range it has a very positive effect on sound. I’m not very good at describing my sonic impressions in words, so I’ll just say that getting the fundamentals-range right seems very critical in obtaining good sound.
I agree with Romy’s observation that the 2420 is a far more delicate sounding driver than the 2440. I tried using the 140Hz horn together with just the 2420 on a 400Hz horn (down to ca 1200Hz). This led to fine results, but the sound was miniaturized and less robust and "rustic" compared to the 2440-injected alternative. I want to use the horns well above their cut-off frequencies, and I probably need to use the 2440 a bit higher up in order to get rid of all horn colourations, though. These are probably my only real conclusions so far: “don’t push your horns” and “ it’s important to get the fundamentals range right”.
Crossovers are all first order, speaker level. I have a 1/3 octave RTA as a guide when trying out different values. Of course, my testing so far has been quite haphazard, and my knowledge is a bit limited, so I don’t want anyone to take this for anything more than amateurish ramblings. There are so many factors at play... Still, my experiences so far indicate that this might end up as a very satisfying project. DSET seem almost mandatory in this context, and this will be the next step once I have decided on rough crossover points.
And the frame? At the moment I’m just using open book-shelves from IKEA. I haven’t come up with a better alternative yet, but since I have decided on the horns and drivers, and in what vertical order they will be mounted, it’s “only” a matter of engineering.
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