Question Stereo Integrity HT15 sealed box build

Discussion in 'DIY Speaker & Subwoofer Building' started by surayne, Jul 23, 2019.

  1. surayne

    surayne
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    I've just bought a pair of these drivers (dual 4 ohm) from a forum member for my very first (semi) DIY sub effort, and I'd be very grateful for some feedback about my plans. I already have a Behringer NX6000D that I'll be using to power and EQ them. I plan to get a pair of sealed boxes made up in 25mm MDF and have 2 options - either a 75L or 100L box.

    I've modeled both in WinISD and have attached some graphs... from what I can see the bigger box will hit max cone excursion with only 425W at 5Hz and the 75L will take 600W. At 10Hz it's 600W and 750W respectively. Not sure I can see any major differences otherwise. I've attached the WinISD file for the driver in case anyone would like to have a go themselves, but is there going to be any real advantage in building the larger box?

    Given that I'll have more than enough power on tap, would it be possible to implement a Linkwitz Transform using the Behringer to give more output at the lower end? What are the pros and cons of this?
     

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  2. mattkhan

    mattkhan
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    An LT doesn't change max output and this is something you may choose to end after room gain is factored in

    There is a parameter (whose name I forget, Qb maybe) which will flatten out that rise at the v end of the FR and better reflects the behaviour of a sealed sub

    I would forget modelling for 5Hz when modelling a pair of 15s, even 10Hz. Focus on 15Hz and up. I would go with the size that fits your space better.
     
  3. surayne

    surayne
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    Thanks. Modelling for 15Hz gives max cone excursion at 850W in the 75L box, which is the preferred option. Should I be using the limiter on the amp to prevent damage to the driver, or is this unnecessary in a sealed box?

    About the boxes - I'm hoping to have a local body shop spray them in gloss black. However I'll have to prime the surface first. I see some have used multiple coats of dilute PVA as a primer. Would there be any benefit in that rather than just applying a couple of coats of MDF primer like this, lightly sanding between coats?
     
    Last edited: Jul 24, 2019
  4. mattkhan

    mattkhan
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    Google says it depends what type of paint you use on top (as to whether PVA will do something bad or not)

    I have generally used zinnser (bin or 123) which works well, never tried to gloss paint them though
     
  5. surayne

    surayne
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    Does anyone have a copy of the technical drawings for the SI HT15? They’re not available on the website and I can’t find them elsewhere.

    Edit: managed to find one and have attached it here for further reference.
     

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    Last edited: Jul 30, 2019
  6. surayne

    surayne
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    Made some progress over the past week. Cabinets received, unfortunately there were a few dings to corners in transit that I touched up with filler. Drilled the cabinet for the threaded inserts and speakon connector.

    I started off with a plan to spray the cabinet in gloss black but decided to go with matte Tuff Cab in the end. Three costs of Zinsser BIN went on and I've just finished the third coat of Tuff Cab.

    Had a bit of a mishap with one of the feet when moving the cabinets which led to some damage to one bottom corner which I've filled with epoxy. Seems pretty solid thankfully.

    Next step is to cut the underlay I've acquired to size and stick it on the inside of the cabinets. I'm also planning to put a couple of hollow fibre pillows in each cabinet to increase the apparent internal volume, as the cabs have turned out a little smaller than I planned. Would any other stuffing be better?
     
  7. surayne

    surayne
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    More progress... Lined the enclosures with foam underlay and stuffed them with 1kg of polyfill each. Secured the drivers and they are done!

    All seems to be working well. However the EQ in my receiver (Audyssey MultiEQ) is pretty pants at bass equalisation. I plan to take some measurements with REW and use Multi Sub Optimiser to generate some filters to plug in to the NX6000D. Once I figure out how to use all of them!
     

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