LCS tweeter add-on

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JLM

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LCS tweeter add-on
« on: 14 Oct 2015, 06:38 pm »
In a way, this is a follow-up to a review I did 5+ years ago after having Bud Purvine provide EnABL treatments to my Fostex F200A drivers, that unfortunately are no longer in production.  After 11 years I’m still using the drivers in the same speakers, but Bob Brines (Brines Acoustics) has renamed them M18-F200 (floor-standing transmission lines).  The drivers are rated 30 -20,000 Hz, 90 dB/w/m, 8 ohms and has a full-bodied sound, unlike most extended range drivers.

Since the last review the room has remained the same: my 8ft x 13ft x 21ft basement study (office in the back, listening in the front) that is mechanically/electrically isolated.  But the rest of the system has changed and currently consist of Channel Island D-100 (the original 100 watt mono-blocks bought used) and an Emotiva DC-1 DAC/pre/headphone amp.  I listen primarily to small ensemble jazz, classical, and classic pop (such as Torme and Holliday) at moderate levels. 

As a regular here at Audio Circle I picked up on the whole constant directivity discussion and in particular what our own Duke LeJeune has been up to.  So I PM’d Duke and based on my particulars (especially speakers that without whizzers have extremely limited high frequency dispersion) he suggested adding ambience tweeters that would follow James Romeyn’s “Late Ceiling Splash” (LCS) concept.  The rough idea is to introduce delayed (> 10 millisecond, 11 foot additional travel) sound to provide separation between direct (first sound) and reflected (sounds) to improve imaging.

So I pulled together borrowed tweeters (thanks Scott W.), spare parts I had lying around, and whatever bits I could gather at the local Radio Shack to try it out.  The tweeters just lay on the floor behind the speakers facing upwards, with a cap in series, then wired parallel to the main speakers.  And I liked it!

Next I invested $70 in Duke’s recommended Dayton DC28F-8 tweeters and 1.5 uF Jantzen caps with Madisound 15 gauge speaker wire.  At first I thought they added too much brightness (even for these 59 year old ears), but I’ve acclimated.  The tweeters have filled in the beaminess of the F200A drivers without affecting the character of the sound (just as Duke predicted).  And imaging has solidified.

Finally at the suggestion of a member of my small audio club I’d been experimenting with speaker location (had been following the Cardas equilateral triangular near-field recipe) by widening their stance, but soon ran into collapse of the center of the soundstage.  But adding the LCS tweeters has helped significantly.  I’ve been able to widen the speakers from 58 inches to 105 inches (center of driver to center of driver) and pulled them about 4 inches farther from the front wall to enlarge the soundstage before collapse (recording dependent).  Note that previously I'd aimed the speakers to cross behind me as I also listen (more casually) from my desk (directly behind the listening chair) but now the speakers are aimed to cross in front of the listening position to help spread the imaging away from and between the speakers as perceived from the listening chair, but now the sound is more ordinary far-field from the desk.

Thanks to Duke and James!!
« Last Edit: 15 Oct 2015, 10:01 am by JLM »

Duke

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Re: LCS tweeter add-on
« Reply #1 on: 16 Oct 2015, 07:05 pm »
I hadn't expected that a beneficial side-effect would be your ability to move the speakers farther apart and orient them more optimally.  Thanks for experimenting and passing that information along. 

You might find that 1.0 uF works better than 1.5 uF if brightness is still sometimes an issue, and/or maybe inserting a couple ohms of series resistance, but on the other hand if it ain't broke...


JLM

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Re: LCS tweeter add-on
« Reply #2 on: 11 Mar 2017, 01:57 pm »
Very late feedback.

I did try 1.0 uF cap, which didn't seem to make much difference.  But tried swapping out to nice ($60 each) Jupiter beeswax caps made a nice improvement.  However a $60 cap for a $20 tweeter is a bit ridiculous.   :green: