Which 15" driver for a 4cubic foot ported box?

Discussion in 'Home Theater Projects' started by Wes, Sep 15, 2003.

  1. Wes

    Wes Screenwriter

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    I have been running some older drivers in the boxes I have made and now want to upgrade to reach lower. The boxes are 4 CF and have a 4" port 9" long!
    I have two boxes and will need two drivers and would like to keep the cost below $300.
    I will have a 130w amp to power these that can be ran at 4 ohm!
    Was looking at Daytons but not even sure which ones to buy!

    Wes
     
  2. Paul Spencer

    Paul Spencer Stunt Coordinator

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    If you haven't already, first check out the LDSG (Loudspeaker Driver Selection Guide) ... do a Google search for it as I can't put in a link.

    The Adire tempest is a great driver, I have heard the Dayton is really an inferior copy of the Tempest. You can get it for $150 but it really needs a bigger box 7 CF and your amp won't make the most of it. That size suggests a driver like the Shiva vented. Also you will probably need two ports of that diameter, and they will need to be much longer - 2 vents 4" tuned to 20 Hz in a box that size would be almost a metre long!!! ... suddenly you have lost 15 litres to those 2 vents!!!

    130 watts @ 4 ohms ... is that a power amp with 2 channels? If it's a plate amp and you have 2 subs it won't be much power - you may end up with two 4 ohm Shivas in series = 8 ohms = less power from your amp (eg more like 80 watts, which is certainly not much for a sub like the Shiva).

    You could also consider the Dayton 12" DVC which is similar to the Shiva, but works in a smaller box. The DVC12" would be like an EBS in that size box. From what I have heard, it is better than its big brother even though it has more output. Dan Marx (good site worth checking out) had the Dayton 15" and ended up replacing it with a Shiva. If you went with either the Shiva or Dayton you could save a little $50 - $80 (I think) and put that towards an amp that has enough juice to show what they are made of.

    I don't think you are likely to find a 15" driver that will work well in a vented alignment of that size with your budget (if I'm wrong someone please set me straight on that one). You could do a Tempest sealed sub - with a Q of 0.7 but then you lose probably 5db out deep bass output, added to the fact you don't really have much power to drive it.

    Hope this helps,
    regards,
    Paul
     
  3. Kyle Richardson

    Kyle Richardson Screenwriter

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    Wes, those enclosures are a bit small (ideally) for most 15" drivers on the market except for car drivers which you really wont want to use, but they can be made to work. Doing some calculations with your box and port size I came up with a tuning of about 26.5 Hz.

    I modeled 3 drivers for that enclosure 1. Adire Tempest 2. Dayton DVC 295-190 3. Dayton Quatro 295-560.

    All three drivers have a bump in the midbass region indicating the enclosure is a bit small for them but the bump isnt terrible at 2db. The Tempest and DVC have the bump centered in the upper 40Hz range while the Quatro has it centered around 40Hz. These bumps can be flattened a bit by adding polyfill to the enclosure which will make the driver "think" the enclosure is a bit larger than it really is.

    After looking at it I really like the way the Quatro looks compared to the other drivers and I think it would be the best choice with the 130 watts you will be feeding it. It is also the cheapest of the three at $84.37 which puts you well below your budget which is always a good thing!

    None of these drivers will be 20Hz monsters in the existing enclosures you have but they will have a lot of punch in the 40Hz range which is where most of the HT bass is centered anyway.

    Hope this helps a bit!
     
  4. Wes

    Wes Screenwriter

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    Thanks for your feed back Paul and Kyle! OK I now have decided to buy a higher powered amp to drive these subs! Perhaps a 250w plate amp or would a Pro amp be better, can't say I want noisy fans!

    I will eventually build bigger boxes but for now will install them in these 4cf enclosers.

    With this new info would you still advise the same. Or would I be better off with a 12" driver in these boxes to reach lower or for that matter making one 8cf incloser out of the two boxes and running one better 15"? [​IMG]

    Let's say I have now $400. to work with! I just sold a CRT projector and have HT upgrade money burning a hole in my pocket!

    My room dimensions are 12'x24'x7'8"!

    Wes
     
  5. Paul Spencer

    Paul Spencer Stunt Coordinator

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    Wes,

    I have a few suggestions:

    1. Get a single Tempest and an amp with more power - Kyle probably has a better idea of how much power for the Tempest but I'm guessing 350 watts is more like it, wire the tempest to 4 ohms. Modify the boxes so that they fit together to make one bigger box, line with carpet if you want. Later make a box that suits your room, taste etc, and if you feel the need for 2 then get another plate amp and make two boxes.

    2. Put the Shiva or Dayton 12" into each, get a more powerful amp - run them from one plate amp initially. Later upgrade to a second plate amp. Alternatively you may find a 2nd hand PA amp is cheaper and will power both right from the start. You can get a sub processor as a kit, and if you do like a PA amp with a fan, you can put it in another room.

    3. Get a pair of tempest drivers, put them in your current boxes and live without the deep bass until you build bigger boxes. Buy the more powerful amps as your budget allows.

    4. Think of another totally different option ...

    Personally I think the first option is the best way to go, as it is the most flexible in terms of upgrade. 3 might be overkill. 2 might leave you wanting more. 1 allows you the choice ...

    The tempest needs a big box. One of them gives you very good bang for your buck, but it also depends on fitting it all into your room. You can make the popular coffee table sub. You can make it look like furniture. Personally I like tall and slim rather than bulky and chunky. One way to fit a big box in the room is to make it very tall and slim:

    eg. tempest in an EBS alignment - 340L (12 cubic ft)
    Adire suggests 0.6m x 0.6m x 1.2m ... those are fridge dimensions, not something you want in your living room!!!
    I'd much prefer:
    0.4w x 0.6d x 1.8h (metres)
    That could fit in the corners nicely, esp if you had 2 of them. Also it is easier to get a box of those dimensions to be very rigid.

    Anyway, enough rambling from me,
    I hope this is helpful
    regards,
    Paul
     
  6. Wes

    Wes Screenwriter

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    Thanks again Paul, I have been searching this site for more ideas and ran a crossed this! Some was stating it would make for a good HT sub even though it was a car speaker!
    http://www.crutchfield.com/cgi-bin/S...ecs&i=109gt150
    And they are showing a 4cf box to be ideal!

    Wes
     
  7. Bryan Michael

    Bryan Michael Supporting Actor

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    i would get a av15 seal the box and get a good amp you will be happy very happy. plus when you get the cash you can buld a bigger box and add more power.
     
  8. Kyle Richardson

    Kyle Richardson Screenwriter

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    Oh sure, put the size and power restrictions on me then go and change your mind! [​IMG]
    If you are going to go with a bigger box and more power in the future I'd go with the Tempest as it has nearly double xmax as the Quatro I suggested earlier. You may also want to look at the Stryke AV15 but it will need a bit more power than the Tempest to realize its potential.
    BTW, 250-350 watts is a good amount for the Tempest depending on the box size and type.
     
  9. Paul Spencer

    Paul Spencer Stunt Coordinator

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    Wes,

    The JBL is not a driver I'm familiar with. In general, most car audio subs don't cut it for home use - most just aren't that good IMHO. Looking at the specs, it has good efficiency, a fairly large xmax so you will get a fairly large output ... hmmmmm no TS parameters, you really need them to design properly. Also the fs is high 28 Hz so you will miss out on very deep bass if you want it for HT use. Polypropylene isn't considered a very good material for subs - not very rigid. The better subs are often kevlar reinforced for stiffness.

    I once heard a review of the Shiva from a guy who used to sell car audio subs - for his own use he preferred the Shiva (despite the fact that he could get discounts) and considered it superior to much more expensive car audio subs ... I think in general you are best to avoid car audio subs - the design isn't really suitable, the sound quality is usually inferior and the cost is often high relative to the vd (volume displacement) which determines the max potential for deep bass SPL. I think you can do better than the JBL.

    cheers,
    Paul
     
  10. Joe.Kuta

    Joe.Kuta Stunt Coordinator

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    Yes, leave car audio in the car.
    Impressive 95dBA sensitivity, that's about it though.


    I suggest the AV15 in your box.
    I have an old 3ft^3 box i'm putting an AV15 in,
    I will be deciding whether to go sealed or ported soon,
    although from WinISD ported would be a -lot- better,
    curious that people say 3-4ft^3 boxes are only good sealed??

    IMHO
    1-2ft^3 = small (sealed!), 3-4 = med, 6 and above = large.

    Stuff your box w/ polyfil ~1.5 lb / ft^3,
    for up to 30% increase in volume.
    http://www.integracaraudio.com/carau...ces/fiberfill/
     
  11. Dave Milne

    Dave Milne Supporting Actor

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    Since somebody mentioned JBL...

    The 2235H is ideally suited to a 4 cu ft vented box in a 6th order configuration (5 dB boost @ 24Hz). The result is F3 of 24Hz and 93dB efficiency. This happens to be exactly the combination JBL used for their B380 sub.

    The 2235 is an impressively built, high quality, low distortion driver. The price tag is a bit steep at $330 and the Xmax is not world-class.

    Just a thought.
     
  12. Wes

    Wes Screenwriter

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    Hay, thanks for all the feed back guy's! I have decided to go with the 15" Quattro's in my current boxes and a plate amp! Hoping it will still be musical and also beat the Fishers for HT. If I find it is not going to cut it I will build new enclosers for them. I'm going to miss the fishers. I have ran them hard for nearly 14 years now and they keep asking for more! The magnet on them I swear is like a 5oz jobby. But they handle 100w and do shake the room.

    Wes
     
  13. Wes

    Wes Screenwriter

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    Ok I have the two 15" quatros, Darrenk at Partsexpress is stating to increase my 4" dia. port to 14" do you guys agree?

    I did put one in with my 6" port and it did sound good, will 14" go lower?

    Wes
     
  14. Paul Spencer

    Paul Spencer Stunt Coordinator

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    14" is way too big for a port diameter! 4" - 6" are sensible diameters, but you really need to simulate them and have a look at the port velocity - and try to keep it under 17m/s with a port that doesn't take up too much space in your enclosure.

    When you simulate the performance of the driver in your box, you need to subtract the port volume to get an accurate box volume. 4" ports work ok for most subs if both ends are flared to reduce turbulence, but 6" ports will often result in a very long vent, depending on the tuning point and the box volume.

    JL audio's website has a good tutorial on vent design.
     
  15. Wes

    Wes Screenwriter

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    At this point If I wanted to increase to a 6" Dia. PVC port I could. I have a couple box programs and to be honest to me they are like reading Chinese. I do not understand them. So if someone can run this out for me and tell me what length 4" or 6" would be best I would appreciate it.

    Like I said PE said 4"x14"!


    Wes
     
  16. Paul Spencer

    Paul Spencer Stunt Coordinator

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    6" is a problem as you will need a 1m long vent ... 4" is much more sane and should be fine for this driver. If it is a problem you could change it. 14" long will get it tuned to just above 20 Hz, which sounds about right.

    I go with the formulas rather than trust a simulation - some of them give funny results.

    The port length required to tune a volume of air to a specific frequency can be calculated by using the following equation:
    Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)


    where,

    Dv = port diameter (cm)
    Fb = tuning frequency (Hz)
    Vb = net volume (litres)
    Lv = length of each port (cm)
    Np = number of ports
    k = end correction (normally 0.732)
     
  17. Kyle Richardson

    Kyle Richardson Screenwriter

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    I think he meant to increase the 4" port length from 9" to 14" to lower the tune. You dont need anything larger than a 4" port with that driver and the amount of power you are running to them.
     
  18. Wes

    Wes Screenwriter

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    Yes, I reread my second to the last post and I did not word it too great! Kyle is correct, It will be a 4" port and looks like all is in agreement that 14" long would be best!

    Even with the port I had in the box it sounded great. So today I have alot of work to do.

    Thanks for all your help!!!

    Wes
     
  19. Wes

    Wes Screenwriter

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    Well it's done!

    I extended the port and stuff the box with poly fill and installed the woofs and the sub amp. It took a little work to tune it to the rest of my system but once there it sounds great! Much better than my old 15's, I tryed one at a time to compare and found my old speaks to fall on their face big time at lower frequencies.

    Thanks for the help, this will work til I can build new boxes!

    Wes
     
  20. Paul Spencer

    Paul Spencer Stunt Coordinator

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