Building the RA-8 kit from Raw Acoustic

Discussion in 'Home Theater Projects' started by Ted_Polzin, May 11, 2006.

  1. Ted_Polzin

    Ted_Polzin Stunt Coordinator

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    Ok ... I've been thinking about building some new speakers for a while now and with fathers day comming up my wife gave me a early gift ... I can build new speakers

    I then set out to find something new that would wow me. After speaking with Al for a good hour on the phone and countless e-mails (how does he ever get any work done ) I decided to go with the RA8. Part because they should sound fantastic ... part because my wife approves and likes the way they look (as long as the finish is "shiny" she says)

    So what did I build ... a total of three RA-8's for the LCR ... I have a front projection system so the center will fit nicely there.

    For more info on the build process please see the thread at AudioCircle



    For my impressions,

    Anyways ... amazing is what I have to describe the sound ... clear is another ... speech has always been "hard to hear" unless I turn up the calibration on the center way to high ... of course that lead to other problems .... I have also never had a properly matching front stage ... now all I can say is wow ... speech is clear and there ... I can hear everything I'm supposed to ... both in movies and TV. Also I was playing with things last night and went outside ... I had not realized I turned it up that loud .. I could hear it clearly to the garage ... hmm .. always in the past if I turned it up louder it would hurt the ears before I got to loud ... not this time ...

    I put on short passages from the following movies

    Black hawk down .... very very good .. could hear the bullets and still hear people talking ... in the past that has been hard ..

    Resident evil 2 .. say what you will about the movie the sound is fantastic ...

    Star Wars 3 - opening scene .. wow things were buzzing around me every which way

    War of the worlds - scene where the tripods first emerge ... again wow

    Also it was amazing how the speakers melded ... it really was one very big speaker across the front ... nothing else to say ....

    Well I'll let things break in for a while before doing a better demo .. I've also got some new electronics coming in a week or so ( the UL's from Mark Schiffler .... I'm in the first shipment ). I'm looking forward to seeing what those electronics do for these speakers....

    Feel free to ask any questions you may have.

    Ted
     
  2. David_P

    David_P Stunt Coordinator

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    I love the concept... I'm concerned about the ribbon on two fronts:

    1) I've heard that ribbon, specifically, and I don't care for the sound. Hard to describe... somewhat sibilant or etched to my ear. They don't annoy me as much as say, a horn or piezo tweeter, but they have a "sound" that i don't care for. And it's a sound that transfers from speaker to speaker that uses that ribbon.

    2) I'm deeply concerned about the fragility of the ribbons. One fellow I know went to the trouble of building grills, and his wife wrecked the ribbons on two speakers by vacuuming the grills for him.

    That said, i wish these were offered with the option of a dome tweeter (GR T6? ro something with matching efficency) as an alternative.

    Everything else about them... the look, efficency, impedance... is all stellar, IMHO

    David.
     
  3. AllanRW

    AllanRW Second Unit

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    Ted.
    Have you got up off the couch yet [​IMG]

    David
    Our designs with our ribbon we have made for us have a lot different perspective in the upper octave over other ribbons.

    Not as bright of harsh on any tweeter really has a lot to do with the crossover design as well as other parts in the network.

    Any tweeter can be very sibilant I will agree with you.

    The ribbons being fragility as you have noted.
    Well anyone vacuuming any tweeter will suck out a element on a ribbon and on a dome the cover as well!! A ribbon element is repairable.Over and over.
    A dome, well! Yes and no to repair.

    We have someone working on a custom element and in a ribbon of ours he has replaced the ribbon element now almost 80 times!Yes a lot.We are doing work with other materials for the ribbon element.

    Why we use a ribbon.Well the off axis says it all and if you use the ribbon against a dome you will have better off axis (crossover dependant) over a dome as the ribbbon area is smaller.

    Why not use another tweeter well I really answered that in the response above.
    All has to do with horizontal dispersion as well as THD over the band width as well.

    David have you ever got to listen to one of our designs using our tweeter?
     
  4. David_P

    David_P Stunt Coordinator

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    yes I have actually... in your house, in fact :) And other places in the lower mainland.

    I've never heard the RA-8, but many of the HT series speakers. I mean no disparaging remark against your designs, simply that ribbon tweeters in general (those you use included) have a particular identifiable sound to them. And it's a sound that sounds un-natural to me, or at least draws attention to itself.

    As previously noted, it's not as annoying or grating as a horn or piezo tweeter, but there is a lack of smoothness and some kind of heightened edginess, sibilance, or presence etc to ribbon tweeters. You could be right in that implementation has everything to do with it... if so your design are remarkably consistent, as I hear the same high end in all your speakers which I've heard which use that type of speaker. So I tend to chalk it up to the driver. That said, others at various DIY meetings at your place didn't seem bothered in the least by what bothered me.

    All that said, the RA-8 looks like a fabulous design... everything about it is attractive: appearance, impedance, efficiency. I personally just wish there was a different option as far as a tweeter.

    FWIW, the ribbons were "vacuumed" through the grill... ironic as the grills were in place for non-critical listening and specifically to supposedly protect the ribbon from casual damage. How expensive is it to replace the ribbon element anyways?

    Anyway, nice work and a great design.

    David
     
  5. AllanRW

    AllanRW Second Unit

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    David.

    I will say what you have listened to in the designs has a great effect of the sound of the RA8 in another way.

    The RA8 has very little resistance in front of the ribbon and the sound out put is greatly changed from the lower vlaue resistors in the RA8 tweeter network.

    I have a pair of RA8 that are getting ready to head out to a customer and if you want to stop by and havea listen before Sunday you are welcome to do so.

    As well a pair of Apex II and the new 95db MTM.

    Will say this we have a pair of OW 4 tweeters here for a new design , nothing against the ribbon but some people just want a dome and we feel we have a good choice in the new Platinum OW4.
     

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