Undergoing DIY tower speaker project-have a couple q's...

Discussion in 'Archived Threads 2001-2004' started by EmetW, Dec 24, 2002.

  1. EmetW

    EmetW Stunt Coordinator

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    I've been doing custom two and three way component front speaker systems in cars for years, but want to try to build some home speakers (MUCH more flexible with enclosure size, etc....you don't understand what a pain in the a$$ car audio installs are!!!). Here is what I have to work with and my concerns with each:
    1.)
    2 Shivas-side firing or front firing? Yes, I know it would be nice to build two enclosures to test each, but I don't have THAT much time [​IMG] They will be playing up to 100hz if I go three way, 70hz if I go four way...the 100hz concerns me about side-firing because I am afraid it will screw with the imaging. I will be going 2.1 cu. ft. ported and tuned to 25hz...try to talk me into sealed if you like. BTW, each will be getting 100-150 watts.
    2.)
    2 Audax Aerogel 6.5's. They will either run 100hz-2000hz three way sealed in a .7 cu. ft. enclosure or 70hz-500hz ported (about the same size enclosure).
    3.)
    2 LPG 2 inch dome mids. These I am not sure if I want to run. The Audax's have sweet midrange, but the LPG's are killer as well. They would run from 500hz to between 2khz and 4khz. I have a cylindrical sealed back enclosure for them that is custom made for their T/S parameters so enclosure is not a problem.
    4.)
    2 Vifa XT series 1" radiator tweeters. A friend of mine bought some of these last summer and GAWD they sound good!!! Too bad Polk uses them now, but so does Meniscus, so I'm not too concerned with having tweeters the same as a mass market speaker [​IMG] They'll be running 2k-4k on up to whatever.
    Some dilemmas:
    1.) I am thinking of having either a sloped, time aligned front baffle or an angled sideways baffle like NHT's 3.3 for imaging enhancement. Are both of these ideas just gimmicks that won't help much and that my woodworking time shouldn't be spent laboring over, or are either of these a good idea to implement?
    2.) Three way or four way? Making crossovers for either design is not a problem, so the only concern is the best midrange possible...I should have mentioned that I want as much midrange as I can get without having to buy more Aerogel 6.5's (too expensive!!! [​IMG] )
    3.) I'm planning on using 1" MDF and extensively internally bracing the enclsosure. I would like to paint the enclosure to look like piano gloss black, but I would like some solid wood side panels for a nice natural look to "contradict" the modern high-gloss black baffle and top finish. Is it impossible to find pieces of solid wood (rosewood, etc.) that are as large as 20" x 48"? I have been told that it would be economically inefficient, so what alternatives do I have? I'm trying to avoid using veneer, but I fear I may have to...
    If you have any thoughts, please post them as I would like to hear what anyone has to say. Construction starts on Thursday so stay tuned!
     
  2. Rory Buszka

    Rory Buszka Supporting Actor

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    Think of what you'll be using to drive these. The 4-ohm resistance created by your Shiva with both VCs wired in parallel and the 4-ohm resistance of the Vifa tweeter don't go well with most recievers' 8-ohm power rating. If you have a sub in each tower, you could have 500w of major subwoofing. Design the top secion of your towers as a 3-way, and then when connecting it to the reciever, wire it through a plate amp's internal crossover (usually around 125Hz fixed lowpass) and it will take out the sub's signal and amplify it to the proper level for the subwoofer.

    This is complicated to explain.

    First, your enclosure is going to need multiple chambers. The lower chamber will do fine with a 125-hz crossover to the sub, as it is still within the realm of the omnidirectional sub-bass. So, side-firing Shiva woofers will do. The bottom chamber will need to be big for the necessary air volume for the Shiva. You can port with a single 4" flared port out the front of the enclosure. Then for power, get two 120w plate amps from Parts Express. I have one, and they actually put out 155 watts into 4 ohms (which is the resultant resistance of both of one Shiva's voice coils wired in parallel). Put one into the back of each tower. The 120-watt plate amp is compact and narrow, so it will work with a fairly narrow tower. Then build a 3-way top with your Audax midbass, your dome mid, and your tweeter. (I'll let someone else advise you on what to do about the tweeter.) You should keep the top part of the speaker in a separate enclosure fromt he subwoofer for placement flexibility. Then, when you finally have your 3-way mains and your subwoofers all built, run wire from your reciever to the plate amps on the back of the subwoofers using a high-level input. Then use the high-level output on the same channel and run wire from that to your 3-way mains.

    Do you see what I'm trying to get at here?
     
  3. Mark_E_Smith

    Mark_E_Smith Second Unit

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    First of all well come to the world of pain in the a$$ crossover design! [​IMG]
    I would highly recommend using just a 2 way from 100 Hz and up, use the powered subwoofer for 100 Hz and down. Design separate subs and satellite speakers. The Audax drivers will easily handle the mid/bass. A high performance tweeter can handle the rest and you will have a good shot at designing a cross over that is close. 3 way passive x-overs can get real nutty, even the best x-over people dread doing one and it takes 5 times as long. You almost always have to have measurement AND modeling software to get the x-overs tweaked. True 3 ways are very difficult. With a powered sub you are actually designing a active 2 way and passive 2 way.
     
  4. EmetW

    EmetW Stunt Coordinator

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    Thanks for the advice guys.
    Rory-
    Yes, I should have mentioned that I was planning on having a separate chamber for the Shiva apart from the Audax/other drivers. I also forgot to mention that the Shiva's will be driven by a separate amp-my receiver itself will be driving the upper three way.
    Mark-
    You are spot on that the 3-ways are a pain, but a friend of mine is an electrical engineer and builds these things all of the time so I'm in luck [​IMG]
    Thanks again!
     
  5. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Emet, I'd do a two-way on top. Even with an experienced EE friend, 3-way xovers are still complicated, but more importantly, they put LOTS of components between the power amp and the drivers, and if you use high-quality passive components, they are not inexpensive. I'd do 2-way mid/tweet and let the Shivas go down to 60 Hz. Send your LFE channel to a true subwoofer (Tempest?) that you can place for optimum performance. That way you can stick with your single tower cabinet approach and they would do a great job on music and you'd then switch in the subwoofer for movies. With this approach, you could consider using 10" woofs in your main cabinets and make them smaller. Just my two cents.
    Have fun building and enjoying the fruits of your labor![​IMG]
     
  6. Dan_Gtp

    Dan_Gtp Extra

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    Whatever you do decide to go with, let us know when you're done how they turned out, and with pics if you have them. That's some of the best stuff in this part of the forum, seeing everyones stuff and how they turned out. Heck, keep us informed along the way if you feel like it. Great stuff to learn from.
    I want to start reading about DIY towers. I have done my Tempest and am definately happy, and look to more projects in the future. I already have a 5 channel Paradigm Monitor series setup I got this year and would like to know how a DIY rig and for what cost could compare, for future upgrades. Anyways, lots of reading ahead for me. Though I look forward to hearing how your towers turn out eventually. Good luck on them! [​IMG]
     
  7. EmetW

    EmetW Stunt Coordinator

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    My EE friend dug out some 4 way overs today from a pair of older Scanspeak speakers that have blown woofers so we are going to play with those and see if they sound decent or not-if not then we'll go 2 way up top with Shiva-most of this is going to be the fun of experimentation rather than anything that I want to be finished and forgotten about [​IMG] (a separate box with a tempest would be nice, but I think the Shiva's will satisfy my bass needs just fine and take up less space). I will have more updates come January 5th when I return to the states from skiing in Canada. Thanks again for everyone's response!
     

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