GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Time alignment of drivers

Post Subject: Closer to the bug ?Posted by jessie.dazzle on: 8/17/2010

To save people from researching the differences between Romy's and my systems, I'll note the principal differences here, ignoring our ongoing mid-bass projects, which will be different, but both are incomplete, so not yet in the picture.

As concerns this discussion, the main differences would be as follows:

DSET amplification in Romy's case (in essence, a dedicated amplifier for each driver), vs essentially full-range amplification in my case, though I do use a second pair of amps for lower-bass. I don't see how DSET vs full range could make a major difference with regard to time alignment, but I'm ready to listen.

A very likely place for the "interesting bug" to hide would be in implementation of HF. Romy uses a custom-made ribbon driver, where I use a compression driver (EV T350) playing into its own small horn; easier to align with the other channels than a ribbon-type HF driver, which has a different dispersion pattern. This could be a clue... Yes, HF dispersion; I think this might be it.

Another difference (and this could also be it) is in implementation of MF. Romy uses his main MF channel to cover most of the MF frequency range, then uses what he calls a "fundamentals channel" in a narrow bandwidth at the lower end of MF, with some attenuation (correct me if I've got that wrong). I split MF more equally between the two channels with no attenuation. It is logical that if I were to mess with alignment of these channels, the misalignment would be more apparent, as the lower-MF channels in my case are more easily heard, and need to be very strictly aligned with upper MF, and upper MF with HF; the whole lot referencing the upper-bass driver.

Though used differently, our upper-MF channels consist of the same drivers and horns; S2 into 400 Hz tractrix. Romy's fundamentals channel uses an S3 into a 250Hz tractrix; my lower MF uses an S2 into a 180Hz tractrix.

Finally, Romy uses what he calls an injection channel (direct-radiating MF driver from Tannoy Red mounted in custom sealed enclosure) to inject tone and color into the presentation. I know this is not where the bug is hiding, but I'll mention it anyway. If I remember correctly, this channel is run with quite a lot of attenuation. I'm not sure exactly what frequency range it covers, but it uses a 10" driver, so it can only be lower-MF and below. I like to tell myself that my way of using the lower MF channel (and metal-suspended diaphragms) gives me the tone and color I'm looking for.

I could also cite Romy's direct-radiating mid-bass arrays, or my lower-bass enclosures, but the bug is not living in the LF world... There are many more differences (for example I listen to much better music than Romy), but none of these would allow the "interesting bug" a place to hide... I say he is living in difference between our HF drivers.

jd*

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