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Re: Crossover Frequency vs. Slope Question for Ribbons

Posted by JP van Son (A) on October 23, 2006 at 11:23:53

In Reply to: Re: Crossover Frequency vs. Slope Question for Ribbons posted by andyr on October 23, 2006 at 01:29:52:

Andy,

If I thought these sounded as good as I thought they could already, then I wouldn't feel the desire to modify them. The problem is that the 69" ribbon (not planar-magnetic) is run with a 5" Peerless 146MR2608 polycone midrange/midbass monopole (100Hz to 350Hz) and a 10" pulp-cone woofer for the bass (35Hz to 100Hz). Monopoles make a lousy match for a line array dipole and this disparity is very obvious with listening -- the speakers are lacking in body and the drop in levels greatly differ with distance between the two. This lack of proper integration was even noted in their Stereophile review and I wouldn't be surprised if this also led to there being only 30 built instead of being a wildly successful model. Oh yeah, all three drivers are on 6dB/oct slopes, but the midbass is connected with reverse polarity (another thing surprisingly caught in the Stereophile review).

Here's the schematic I drew up of the crossover for this speaker as I directly observed it, but it's kind of a minor point as most of my plans would involve going without it or at least undertaking a serious redesign:

My question about frequency vs. slope was for the ribbon alone as I'm considering either going fully active (removing the crossover and the crossover point and slopes for the other drivers would very obviously be done to match the ribbon) or using the ribbon drivers with planar-magnetic panels to fill in the midbass and then use separate subwoofers for the bottom end. I've a line on a set of Magnepan Tympani bass panels and I've been very much thinking about snagging them and hanging the ribbons off of those. Either way, I'm trying to figure out how I could take best advantage of the ribbon (the best driver in the Flatlines by far) and avoid the weaknesses of single cone drivers in a planar hybrid. So, I was just asking about how low I could safely go with the ribbon, knowing the current xo freq and slope, without risking damaging it. The ideal would be to bring it all the way down to ~100Hz (I'd think this could just about be possible as I rarely listen above ~85dB anyways), use the Tympani panels from 50Hz to 100 Hz, and use regular subwoofers for below 50Hz. Then I'd be able to enjoy the superior sound of the ribbon (good to up to 40kHz) and dipole sound.

Hope I made myself a bit clearer here.
- JP

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