Tuning point VS Fs...rules??

Discussion in 'Home Theater Projects' started by Daniel_AVR, Nov 28, 2003.

  1. Daniel_AVR

    Daniel_AVR Extra

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    Hi diy enthusiasts,

    I'm pretty new to this hobby, and my first DIY project is to build a sub

    It begin with a tryout of a Velodyne CHT10 as my first sub. I found it pretty good for HT but a bit boomy for music. Plus I realize that speaker and amp used can be found a ridiculous price as separate components. So I returned this sub with the firm idea to use all this money and put it to good components instead.

    I'm more toward music than HT, like 70/30, but I like the Looow bass extension provided by the Velodyne....

    I've done some search about sub building here and there, I'm not familiar with all terms but I learn....

    I'm pretty set over an Adire DPL12 and an HS200 plate amp.

    I'll have a 15.5" X 15.5" X 18.5" enclosure, this is also pretty set. I plan to build it ported to have the best bass extension for HT but I'll also make a plug to convert it to a sealed one when needed(or just for the fun of it)[​IMG].

    Now I'm doing some simulation with WinIsd and the best curve for transfer function magnitude is with a 13.3Hz tuning point.....does this make sense?? any warning on this? it's lower than Fs of the speaker(16.3Hz)! Does this matter? What's the rule of thumb on this?
    Am I using the right plot?

    Adire doesn't provide all specs for the DPL12, so some plot aren't displayed.

    thanks

    Dan
     
  2. ThomasW

    ThomasW Cinematographer

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  3. Daniel_AVR

    Daniel_AVR Extra

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    No it's way to low.

    What would be the lowest acceptable and why?

    How long is the port in your sim?

    10.24" x 2" diam.

    Do you plan on the port sticking outside the box like a stove pipe?

    Absolutely not!


    Do you understand that 13.3Hz is well below the limits of human hearing, and as a result is inaudible?

    Yes, but could it still help the audible curve? That's why I asked, it sounds weird to me.

    Have you looked at the ported alignments posted on their site for Adire's other 12" drivers?

    I'd take a look but, as the spec of Shiva are pretty different I didn't take them in account, and the Brahma if clearly build for big punch in small enclosure so no correlation with DPL12

    Do you understand that box tuning is basically independent of the driver being used.

    Yes! but I don't clearly understand the influence between the box tuning and the frequency response of the total system, playing with this aspect (box tuning) in simulation show me that it can boost or attenuate output in the order of +/- 1db, any reading to suggest?


    Do you understand the implications of this DPL-12 specification, the regard to the output power of your amp? (SPL: 84 dB SPL @ 1W, 1m (87 dB @ 2.83 Vrms, 1m)

    Yes!

    If these questions are baffling, you should consider visiting your local library or buying a book on loudspeaker design and theory

    I will, I will.....maybe a Christmas gift??.....WIFE!!!!... WIFE!!!....[​IMG]

    Thanks

    Dan
     
  4. ThomasW

    ThomasW Cinematographer

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    You shouldn't use a 2" dia port, it will chuff like a steam locomotive at higher ouput levels

    You need to use at least a 3" diameter flared port. I use and recommend 4" dia flared ports with 12" drivers.

    Now model those bigger port diameters with the very small size of your box, and see what happens to the length of the port(=stovepipe).

    Ported box tuning just boosts the system output at the point where the driver naturally starts to roll-off.

    The efficiency of the DPL-12 is LOW, That combined with your small box and the relatively modest output of the HS200 may create problems. Overall system output will of course be dependent on the size of the listening room and your listening levels.

    The reality is that with your insistance on using your existing box, the only viable option is to run it sealed. As a result 'choosing' tuning is a moot point.

    A good beginners book is
    "Great Sound Stereo Speaker Manual" by David Weems and G. R. Koonce
     
  5. Daniel_AVR

    Daniel_AVR Extra

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    Ok,

    You shouldn't use a 2" dia port, it will chuff like a steam locomotive at higher output levels

    It makes good old sense, experience speaks here....

    You need to use at least a 3" diameter flared port. I use and recommend 4" dia flared ports with 12" drivers.

    I was looking at 2.5" to 3" diam. port at first but like you told, the resulting lengths were unrealistic for my box dimensions...if I boost box dimension, numbers aligns in a more normal fashion

    The efficiency of the DPL-12 is LOW, That combined with your small box and the relatively modest output of the HS200 may create problems.

    Which ones?, others than low max spl? If I'm right the relatively low efficiency of the DPL12 is the price to pay to have this bass extension. But what is the max spl should I expect with this amp, it's 3db of headroom at 200W so +/- 400W max (according to Adire)

    The reality is that with your insistence on using your existing box, the only viable option is to run it sealed. As a result 'choosing' tuning is a moot point.

    Ok good, I should realize that I'm wrong in my search for looow bass extension, I double searched this extension. I pick a speaker with impressive natural bass extension with a pretty good size/match for HIS sealed enclosure. No real need to try to port it. I think I'll use these components as a sealed system and take my time to learn more to still build a bigger ported enclosure later for it.

    But my first though was "low bass need a vented design" Can I really have that low Hz extension with a sealed box, simulation numbers tend to, but reality?

    I was maybe mislead by comparing with so many in store's ported subwoofer that are in the same size league. Is it due only to difference in speakers spec?

    Nothing bought to date, it's always time to re-start from scratch. You seem to questions my components choice....you make me doubt now....


    A good beginners book is
    "Great Sound Stereo Speaker Manual" by David Weems and G. R. Koonce

    Noted, any online reading?
     
  6. michael-e

    michael-e Agent

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  7. michael-e

    michael-e Agent

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    Also, i sent u PM daniel_avr
     
  8. Jack Keck

    Jack Keck Second Unit

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    The Adire site has plans for the DPL 12 and a passive radiator.
     
  9. ThomasW

    ThomasW Cinematographer

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  10. Daniel_AVR

    Daniel_AVR Extra

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    Ok guys,

    I'm not stubborn [​IMG], yesterday I ordered "Loudspeaker Design Cookbook" by Vance Dickanson from Amazon.ca, should have it by the end of the week. So some dumb questions should be answered.

    I found loudspeaker101.com also yesterday, some reading in sight there too.

    Jack (Keck), I saw this Adire plan, I event printed it, but adding a passive radiator also add to the cost so I'm not incline to use this design as I try to keep the cost at what the CHT cost me level at first....hard hard hard...

    Jack (Gilvey), I've done many simulation and some driver can be used ported with this box but not the DPL12 his EBP it too low

    In fact I have a few speaker in my last list, like; Shiva, DPL12, Stryke SAE 1204, Stryke AV12, Dayton Titanic (295-400). All picked for their low bass extension in simulations with WinIsd and Bassbox. I finally settle on DPL12 for primo; lowest bass extension on my speaker choice list and secundo; Adire products are distributed here by Creativesound.ca and they have a pretty good deal on a kit consisted of a DPL12, A HS200 and a 17" x 17" x 20" ext., all parts precut, enclosure. That's the whole story.

    But things tend to change, I found a used HS500 on EBay this week-end for the same price as a HS200, I couldn't resist to buy it.....

    So now things are now open....as i'll not have the amp till one week or two, I'll take the time to read and make a choice. But for sure I'm toward a driver costing 150$ and under and with a good bass extension. Sealed or ported?? I still leaning toward a dual design like a ported box with a pluggeable port....if doable of course.

    But what happen with retail sub? do they fool us with their small ported boxes? the CHT10 had a 1" x 15" port in a 16.25" x 15" x 19.75" box....try to simulate that for fun...


    Thanks for those who help me to see the right portrait...specially ThomasW


    Daniel
     
  11. TimForman

    TimForman Supporting Actor

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  12. Chuck Bogie

    Chuck Bogie Second Unit

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    The Dickason book is gonna make your brain hurt, and if you stick with it, it'll run out your ears. Read a section in the "low end" book, then read a corresponding part of the VD book when you think you understand it...
     

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