DIY In-Walls - driver suitability?

Discussion in 'Archived Threads 2001-2004' started by Chris Eriksen, Nov 25, 2001.

  1. Chris Eriksen

    Chris Eriksen Stunt Coordinator

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    Hello Everyone,

    I have an unusual DIY question. Due to WAF constraints, I am thinking about building my own in-wall speakers for my HT room. My question is on the suitability of drivers for this application. I have a set of 8 Dynaudio 17w75's left over from a previous project, and I would like to make use of these drivers to build six or seven identical speakers. They seem to model well in an IB configuration, but I would guess that I am overlooking something. Here are the T-S parameters for the Dynaudio 17w75:

    Vas 18.8 L

    Fs 39 Hz

    Qts 0.74

    Qms 2.18

    Qes 1.12

    Pmax 150 W rms

    lin. excursion 5.5 mm

    max. excursion (P-P) 19 mm

    Sd 120 cm^2

    Mms 15 g

    B*L 4.3 Tm

    Le (1 kHz) 0.45 mH

    Sens 89 dB

    I guess my primary concern is the limited xmax of these drivers. If they are constrained to playing 80 Hz and up, will this be an issue? They will see aproximately 80-110 wpc, depending on amplifier selection.

    My other option is to use small sealed enclosures, probably ~12 L, in conjunction with Dynaudio Variovents. This is less desireable for the wife, but I will do it if the IB configuration is a significant problem. However, the trade-off will likely be a smaller enclosure for the planned DIY sub...

    Thank you in advance for any advice you can offer.

    -Chris
     
  2. Chris Eriksen

    Chris Eriksen Stunt Coordinator

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    ^
     
  3. Rich Kraus

    Rich Kraus Stunt Coordinator

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    your treading in an area not to many folks arround here have experience with (or at least not many have posted about it). as i understand it, designing full range speakers into walls can be a tricky affair considering the crossover mods necessary with the huge baffle surface. i have heard that in walls never really immage/soundstage right.
    ...and that about sums up what i think i know about the subject (not to be confused with what i actually know [​IMG] )
    put in an IB sub, and let that be the compromise so that you can slip traditional speakers under SAF. thats what i did [​IMG] !
     
  4. Chris Eriksen

    Chris Eriksen Stunt Coordinator

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    Rich,
    Thank you very much for the reply. After thinking about this further, I am pretty sure I will go with small quasi-aperiodic enclosures using Dynaudio Variovents. Aside from the extremely large baffle surface, I can not imagine that I would be happy sacrificing the ability to reposition my speakers. If I do try the in-walls, it will only be for the rear channels.
    I love your idea on using an IB sub, but unfortunately, there is no way to do it in my HT room. [​IMG] I think it's time to sharpen my carpenrty skills and build some cherry or mahogany cabinets for the mains in order to pass the WAF test. [​IMG] Either that, or invest in an acoustically transparent screen...
    Once I make up my mind and start the project (a few months away), I will post some pictures.
    Thanks again,
    Chris
     
  5. Greg Monfort

    Greg Monfort Supporting Actor

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    These drivers are Xmax limited to ~50Hz/150W in an IB, so an 80Hz/4th order should suffice.

    WRT imaging, in-walls can be just as good as free standing, but they require a more directional speaker (such as horns) and/or sufficient wall treatment to absorb reflections down to 300-400Hz, with the L-R mid/HF toe'd in. Since the walls make them half space, no efficiency robbing baffle step correction is needed, though with these high Q drivers, it's not as much an issue.

    Also, the TV needs to be flush with the speaker wall for best picture/audio integration.

    GM
     
  6. Chris Eriksen

    Chris Eriksen Stunt Coordinator

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    Thanks, Greg! That information is very helpful. I think I may try doing the rear channels as in-walls, and see if I like the results well enough to do the same with the mains.
    On a similar topic, can you recommend a good reference book on crossover design? Thanks! [​IMG]
    Chris
     
  7. Greg Monfort

    Greg Monfort Supporting Actor

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    "Electronic Filter Design Handbook", Arthur B. Williams, McGraw-Hill, ISBN 0-07-070430-9.

    GM
     
  8. Chris Eriksen

    Chris Eriksen Stunt Coordinator

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    Thanks! [​IMG]
     
  9. Hank Frankenberg

    Hank Frankenberg Cinematographer

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    Chris, if nice wood finish speakers will pass the SAF test, then by all means do build your own, either from scratch with a proven design, or from a kit. You can get kits with everything but the cabinets and also some with cabinets. Some are available in unfinished MDF, and if you build your own, use MDF. Then you can buy the veneer of your spouse's choice, apply it and give it an oil or polyurethane finish and have beautiful furniture-quality looks and your good sound, all at a low cost. If you've never built cabinets or veneered before, just ask questions here.
     
  10. Chris Eriksen

    Chris Eriksen Stunt Coordinator

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    Hank,
    Thanks for your advice. That may be the best route, as I have built many cabinets and quite a few pieces of furniture. However, I have never applied a veneer, so I am sure I will have plenty of questions when I finish the cabinets. [​IMG]
    I think I will start with the surround channels, which will be in-walls. Due to the odd shape of my room, this is the best way to cosmetically integrate the surrround channels. Plus, the WAF dictates that one pair of visible rear speakers is the limit, or I can use as many in-walls as I want.
    Thanks again for all of your help! [​IMG]
     

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