# High efficiency bookshelf for HT



## mayhem13 (Feb 2, 2008)

Hey All, haven't posted here in a while. I've been setting up the video side of things with the new Mitsu 1500 Pj. Now thanx to the massive 100" screen, my audio doesn't seem to be quite to scale as far as soundstage goes. This compulsive need to build things is really out of control !

Thanx to some rants of DS, i looked up some old contacts from the pro audio world and managed to get my hands on some slightly used B&C 8ndl51. Just got around to putting them on an OB of 3/4 MDF full range for testing and WOW-these things get LOUD. Even on the OB, pretty decent response from 150-250hz audibly of course since i have no testing gear...YET. My older Carver 2channel was clipping before the drivers showed any signs of distress!

Well here's the plan. A WT using a Vifa DX25 mounted in a waveguide in 21 liters ported and tuned to 50Hz, crossed at 1.3khz. I believe the DX25 can handle the low xo when mated with the waveguide amd given the freq response of the B*C, looks to be the perfect XO point

Freq response 8NDL51 http://www.bcspeakers.com/sez/popup_graph.php?id_prodotto=53&id_foto_prod=76&tipo_descrizione=40

The freq response of the DX25 can be found here
http://zaphaudio.com/tweetermishmash/compare.html

Before i start asking for XO help, any thoughts on the premise? I'll add that i'll be placing these above 27" tall sealed subs side firing RSS390HOs with Oaudio 500w plates.


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## looneybomber (Sep 20, 2006)

Looks promising. The sensitivities match up pretty well, which makes things easier. Are you planning on playing with an active XO to help with XO points or are you going to go passive from the get go.


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## mayhem13 (Feb 2, 2008)

I's like to go passive but i will need some help and support from fellow forum members-Still trying to figure xover design out.


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## willy-be (Nov 15, 2006)

mayhem13 said:


> Well here's the plan. A WT using a Vifa DX25 mounted in a waveguide in 21 liters ported and tuned to 50Hz, crossed at 1.3khz. I believe the DX25 can handle the low xo when mated with the waveguide


You'd be better off using a compression driver and a real waveguide. The current frenzy about using WGs with dome tweeters is problematic. Reason being Zaph's design doesn't show any off axis measurements. Several experienced DIYers who've tested domes with the MCM waveguide have come to conclusion these dome/WG combinations do not work very well.


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## looneybomber (Sep 20, 2006)

There's always ribbon tweeters.


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## mayhem13 (Feb 2, 2008)

I like the idea of a high quality compression driver but a bit pricey-was looking at some Radian 1" that are highly regarded in the Pro Audio industry. In regards to the dome/mcm waveguide, the Vifa tweeter looks a bit larger including the surround than the Seas so in order to get the right interface, the waveguide will have to be machined down farther resulting is a shallow profile which may help with off axis response-tradeoffs i guess.


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## willy-be (Nov 15, 2006)

mayhem13 said:


> the waveguide will have to be machined down farther resulting is a shallow profile which may help with off axis response-tradeoffs i guess.


Domes aren't compression drivers, and they don't load correctly to the WG even if it is machined. 

Been there, done that, it doesn't work as hyped. 

If you want to use a WG with a standard dome tweeter, the way to do it is custom machine the WG from scratch.

These guys do it right...http://www.4sptech.com/version2/index.html


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