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Dual Faital Pro 18HP1030 LLT Build

Discussion in 'DIY Speaker & Subwoofer Building' started by Liammonty123, Dec 5, 2017.

  1. Liammonty123

    Liammonty123
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    Hey guys, I've recently finished building my HTM-12's and need a sub system to go with them. After seeing how many were pleased with the VBSS style subs and the B&C 21's, I deceided to go ahead and order two Faital Pro 18HP1030's (arriving in 3 weeks) to put into two LLT cabs. The reason for these drivers are that they are readily available to purchase in the UK and seem to offer good value for money. I'm hoping the subs will give me lots of chest slamming midbass with also some ULF.

    As for the cabs I am planning two 400l (after port and driver displacement) boxes tuned to 16hz. With the driver at 15mm excursion, just over xmax I can get 110db at 15hz. The cabs will be 70cm high x 60cm deep x 115cm wide and will sit underneath the trio of HTM's. I will pair these subs with an Inuke DSP3000. My room is very small at just under 1000cuft and 250cm wide, so two of these will fit side by side. I am planning on having side firing slot ports (6x60x90cm) with a 10cm gap between each of the subs as shown by my shoddy drawing.

    Hope I've covered my BASIC outline of the build. I would greatly appreciate any help in terms of the build and even if this is ideal or not! The only things set in stone are the max cab size (70x60x115) and the drivers! Many thanks, Liam!
     
  2. Liammonty123

    Liammonty123
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    Concept.JPG Positioning.JPG
     
  3. mattkhan

    mattkhan
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    have you modelled it?
    do you mean the ports are going to fire at each other?
    is the model meant to indicate how you'll brace it? if so, looks underbraced to me
    ports seems a bit narrow too, 10:1 ratio is pushing it for a slot port I think
     
  4. Liammonty123

    Liammonty123
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  5. Liammonty123

    Liammonty123
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    I was planning on having one cab upside down so one port at the top and one at the bottom.
     
  6. Liammonty123

    Liammonty123
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    Also the sketchup is merely a first concept and the likelihood is that the end product will look much different. What are the problems in terms of port ratio, I think I've read something about 8:1 being good?
     
  7. Liammonty123

    Liammonty123
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    Extra Braces added
     

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  8. mattkhan

    mattkhan
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    actually each port is 30*6 isn't it?
     
  9. Liammonty123

    Liammonty123
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    Sorry yes, I was counting it as one big port but with the wood running down the middle it will be two smaller ports yes, should I model it in Winisd as 2x30 by 6 or 60x6?
     
  10. mattkhan

    mattkhan
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    your model looks quite different to mine, probably because I take it you have a HPF added in that model, what did you set?
     
  11. mattkhan

    mattkhan
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    it is 2 30*6 ports though that shouldn't make any difference to the sim
     
  12. Liammonty123

    Liammonty123
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    I set a fourth order HPF at 16hz with 750w into the driver!
     
  13. Liammonty123

    Liammonty123
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    Modelling two 30cm ports seems to bring the port resonance down to 182hz so exactly 10hz from the 60cm port. Ideally shouldn't the first port resonance be above 190?
     
  14. mattkhan

    mattkhan
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    I guessed a 4th order LR at 14Hz but close enough, anyway seems like this should get things banging away :)

    fwiw I'm glad I used 18mm wood (with an eye towards excess bracing) rather than 25mm, damn heavy thing to move around subs of this size (and yours is 2x the size of mine!)

    port resonance seems fine assuming you're crossing in a typical sub range

    I would say you have a fair bit of flexibility in the precise dimensions here, even +/- 50L isn't going to make that much difference
     
  15. Liammonty123

    Liammonty123
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    I'm planning on building the subs in room so I can literally move them back into place, I don't think it would be possible to build them in my garage and get into the upstairs room, at least I don't want to do this and discover they won't fit!

    In terms of first port resonance I plan on crossing somewhere between 80-120hz, most likely around 100Hz so I'm hoping 180hz will be fine.

    Is there anything I'm missing in terms of volume calculations. The actual net volume of a 115x70x60 box is 417l. The driver takes up 7l and the 60x6x90 port 10l? Also in this application can I utilize side ports or is the distance from one cab to another a problem, and also will the different port position cause different sound signatures from the l/r subs?

    The thing scaring me about ported boxes is chuffing, my model shows port velocity peaking at 17m/s at Xmax, is this likely to cause audible chuffing w/o any port flares etc?

    Many thanks!
     
  16. mattkhan

    mattkhan
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    one thing to consider though

    ports produce markedly higher particle velocity than a driver and it's been seen that particle velocity drives tactile response, by directing the port output away from you then you're missing out on that direct feedback.

    Getting the ports to fire at you will make for a more complicated build but IMO it will be worth it.

    I'm assuming you don't have nearfield subs when I say this btw
     
  17. mattkhan

    mattkhan
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    how loud do you actually intend to listen? 2 of these are going to produce an awful lot of SPL, unless you are *really* caning it then I doubt you'll be going near xmax

    if you do actually cane it that hard then 17m/s is fine. FWIW mine models at something like 20-22 when driven really hard & I have driven it that hard and it's not audible at all, well not audible in the context of a room that contains subs being driven that hard anyway :) seriously though mine is clean as a whistle at that level
     
  18. Liammonty123

    Liammonty123
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    The only reason for side firing ports was for simplicity of build, only one straight piece, with front firing I would need a turn for the extra 30cm of the port, however I could then extend the cabinets to 120cm width and gain a bit more volume and as you say get more tactile feedback. If you think this would be the better option then I'll go for it. Thinking about it now most ported builds do have the ports firing forwards and considering I sit 3m away these should be impressive. In terms of spl I'm also hoping room gain is going to add to the ULF mix!
     
  19. mattkhan

    mattkhan
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    two other things to bear in mind

    If you can get an estimate of your actual room gain then that will be a v useful thing to know when it comes to tuning the port length.

    Remember that slot ports near boundaries tend to result in a tune that comes in a little lower than the sim unless you adjust the sim, you can estimate this if you like but probably ~2-3Hz lower is a reasonable guess. Constructing some way to adjust the port length after it is constructed is ideal otherwise it might be prudent to aim at ~17Hz rather than ~15Hz
     
  20. Liammonty123

    Liammonty123
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    Thats quite reassuring tbh, and hopefully with 2 they will never be stressed!
     
  21. mattkhan

    mattkhan
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    if you're not going with NF as well then I definitely recommend front firing ports
     
  22. Liammonty123

    Liammonty123
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    I don't really have room for near field and to be honest am not overly keen on the idea anyway. I'll try and model a front firing port in sketchup!
     
  23. Liammonty123

    Liammonty123
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    I don't really have an idea of how to work out room gain however my longest room dimension is 16ft so I'm assuming gain will happen somewhere around 30Hz?
     
  24. mattkhan

    mattkhan
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    You can measure it if you have a speaker to use and a mic. On paper it will start to rise in the 20s.
     
  25. Liammonty123

    Liammonty123
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    Is group delay anything to worry about? Just looked and its at 110ms at 15Hz?
     
  26. mattkhan

    mattkhan
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    No, that is normal, it is a ported sub with a high pass filter after all
     
  27. Liammonty123

    Liammonty123
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    Is there any sort of rules in terms of bracing ie how much and should I do a double front baffle? Also should I flare the ports and if so how?
     
  28. mattkhan

    mattkhan
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    Usual guideline is to brace such that your panels become ~150-200mm square at most. Lots of small braces are good for this. My approach to this can be seen in Rebuild time

    Flared slort ports mean either a big round over or constructing a more gradual flare out of separate pieces.
     
  29. Liammonty123

    Liammonty123
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    Do you think a flare is necessary on this box with the already low port velocity, the new ports are 5x35 times 2 btw!
     
  30. mattkhan

    mattkhan
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    probably not, my choice would be to go with a smaller ratio though (i.e. a squarer shape) to minimise the chance the port detunes under load.
     

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