Opinions on my setup sub + fronts

Discussion in 'Home Theater Projects' started by Dave Kot, Feb 20, 2006.

  1. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    I was into car audio for a long time but have recently wanted to setup a fairly simple system in my home, mostly for listening to music, but I will also use it every now and then to watch movies. The first question I have is about my subwoofer. I need to know what you guys recommend for wattage to use with the sub and I need help with the enclosure. Here are the small thiele specifications on the sub. It is an eclipse 88120 dvc twelve inch subwoofer rated at 500 watts rms. Also if it helps the room I will have this setup in is my bedroom, its about 14 x 12 so it’s a pretty small room.

    Eclipse:
    Qts: 0.30
    Vas: 90.6 liters
    Fs: 27 hz
    Qms: 5.00
    Qes: 0.32
    Pe: 500 w
    Dia: 11.06 inches
    Sd: 0.051 m^2

    I modeled the sub in winLsd and I came up with 2.7 cubic feet internal enclosure tuned to 27 hz. I don’t know if this is the ideal tuning frequency for the sub or the ideal volume what would you guys recommend? Also a friend of mine had this woofer in a 2.5 ft^3 enclosure, slot ported on 180 watts rms and said it was very loud. Would you guys recommend this or maybe a bit more power? I was thinking of using a parts express amplifier 150 watts rms class a/b for $110 part number #300-804.

    My second question is about my main speakers. The drivers are a component set from Image dynamics with crossovers. They are 6.5” carbon fiber drivers with phase plugs and 1” silk dome tweeters they are rated at 150 watts rms.

    Thiele:

    Qts: 0.39
    Vas: 6.0 liters
    Fs: 70.79 hz
    Re: 3.8 ohms
    Qms: 3.57
    Qes: 0.43
    SPL: 91.00 dB
    BL: 8.12
    Dia: 5.71 inches
    Sd: 0.0013 m^2

    I talked with image dynamics to get the tuning frequency for these and I came up with 58hz and the enclosure size I came up with is 0.3 ft^3 I would appreciate it if you guys could give me some tips on this. Does it look ok or could it be better? Maybe these would sound better sealed?These will be powered by my Onkyo tx-840 receiver at around 120 watts.
     
  2. SamNavy

    SamNavy Stunt Coordinator

    Joined:
    Dec 22, 2005
    Messages:
    50
    Likes Received:
    0
    Trophy Points:
    0
    Dave, I'm not sure this is the best choice of driver.
    This is it, right?
    http://www.pixi.com/~mcaudio/product...88120tidvc.htm

    It's made for car audio... I'm not up on the technical jargon, but there's a reason home audio and car audio should not mix. That driver wasn't designed work in a room... it was designed to work in a trunk. You get a certain type of "gain" from the vehicle itself. You get a different kind of "gain" from a room.

    If you're planning on using this sub to watch movies on, a large part of the "action" happens well below 27hz. You would not be doing yourself a favor if you designed a Home Theater sub above about 20hz given the means. Around here, that's a typical benchmark. I know coming from a car audio background that seems ridiculous, but trust me, some of these guys won't settle for less than around 110db at 15hz or even 12hz.
    Look again at the PE website, through the 23rd, they're having a sale on all Dayton products. A "typical" first DIY home theater subwoofer (this is what I went with and what is often recommended), is a Dayton 12" or 15" DVC in an appropriate sized box tuned to 20hz. For my 12"DVC and a 240watt amp, it was $215 to my door, which is about half of what that Elcipse driver sells for.

    Also, being dual 4ohm voice coils, you'd be placing a 2ohm load on that amp... I don't think there are many plate amps that are 2ohm stable... I know that one is not.
    Maybe someone else will chime in with some technical specifics of why car audio subs are not the best for HT applications, but trust me, there are better choices for WAY CHEAPER than that Eclipse.

    My advice is to stick your Eclipse back in the car and purchase a home Audio Specific driver. At $105 for the 15"DVC, it will knock your socks off!!!

    Check out another thread in this section titled "My first sonosub" to follow my eventual build of a 3.0cuft/20hz 12"DVC box for a room almost exactly the size of yours.

    Good luck, keep us updated. Also, I've got pics of my finished sub if you want one, just email me at [email protected] and I'll send it out. That goes for anybody who wants a peek.
     
  3. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    actually the subwoofer that I have is the eclipse aluminum not the titanium. The aluminum is based more on sound quality than on spl like the titanium. I'm still interested in using this driver if its an option as i'll be listening mostly to music and rarely watching movies. If someone could take a peek at the specs provided and give me a tuning frequency to shoot for i'd appreciate it. Also i was thinking of running it 8 ohm not 2 ohm. I do understand some car audio woofers aren't the best for home audio but there are exceptions and I was under the impression that the eclipse aluminum should be a good candidate for a home setup. Again although i will use it for movies it will be mostly for music.

    Thanks for the comments so far and keep them coming [​IMG]
     
  4. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    Trophy Points:
    0
    Eclipse makes some great drivers and they can work very well for home audio. Go with a much lower port tuning, 18Hz might be good choice...

    And yes you'll want a bigger amp.

    Using a receiver it doesn't matter if the mains are ported or sealed, since you'll be crossing over much lower than the tuning frequency.
     
  5. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    thanks for the info Thomas I'll take a peek at what 18hz looks like in winLsd. Also do you think the partsexpress HPSA 500 watt amp would have sufficient power 273 watts rms @ 8 ohms or would I want to go even higher than that? I was also looking at using a pro amp qsc rmx 850 which would be good for about 500 watts @ 8 ohms.
     
  6. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    Trophy Points:
    0
  7. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    Ok then looks like i'll be taking a look at the qsc rmx 850 rack amp then.

    Is the partsexpress HPSA1000 worth it? It'll do 5oo @ 8ohms and is onsale for $325 untill this thursday.

    Looking at 18hz tuning freq. in winlsd it looks pretty good. Anyone else want to chime in on the tuning frequency? Also thats alot of port to get that frequency, is it ok for me to use pvc elbows?
     
  8. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    Trophy Points:
    0
    Bent ports work fine. Might want to consider a passiver radiator instead, if it fits the budget. It's hard tuning small boxes low.

    If you don't mind the cooling fans in the pro amps, they're the best wattage bang for the buck. The Nady line appears to offer an exceptional watt/$$$ and has gotten good reviews around various forums. Check musiciansfriend for a good selection of various amps to compare.

    In addition to the fans, a pro amp may not offer a rumble filter to protect your driver from over excursion below tuning. Doesn't look to be a real problem with the Eclipse in 2.7 @ 20hz...it'll take 500 watts down to about 15hz, if I got all of my parameters straight for a series vc configuration. Most (all?) of the PE plate amps have a rumble filter around 20hz by default, but adjustable with a little soldering. Some pro amps have selectable filters. The PE 500 & 1000 watt amps also offer parametric EQ and phase controls, which might be useful.

    The Eclipse models an interesting response curve compared to a more traditional home oriented driver like the DVC12 in [email protected] In the end, the [email protected] numbers work out about the same. Let us know how it turns out if you build it.

    wbs
     
  9. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    Well ok i broke down and I bought the parts express 500 watt amp. Which will do 278 @ 8 ohms. Price was a factor here and I think 278 should be fine for now especially since its on sale. It looks like i can get the port frequency 20 hz i need using a pair of 2" ports with a 32" length and winlsd says i shouldn't have problems with vent mach.

    Again i talked to my friend who said the eclipse sounded loud enough for him at 180 watts so i went with the 278 and i think i will be fine as we have a very similar taste in music and we both love this sub.

    Thanks for all of the help and i think i have all the information i need to start building.
     
  10. ThomasW

    ThomasW Cinematographer

    Joined:
    Nov 6, 1999
    Messages:
    2,282
    Likes Received:
    0
    Trophy Points:
    0
    I wouldn't use 2" ports with a high excursion 12" driver. You should use a 4" flared port
     
  11. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    Trophy Points:
    0
    Did you remember to change the input power to 278 watts before you looked at air velocity? You're really starting to climb below 30hz.

    Like Thomas said, one 4" or 2x3" would be the way to go.

    For creative ways to port a cabinet, check out this guy's work:
    http://www.users.bigpond.com/bcolliso/

    wbs
     
  12. SamNavy

    SamNavy Stunt Coordinator

    Joined:
    Dec 22, 2005
    Messages:
    50
    Likes Received:
    0
    Trophy Points:
    0
    You say it's calling for 32"... You'd either have to build a box with one dimension being at least 38" to get enough clearance, or go with some serious elbowing... and the more curves you put in your porting, the less efficient it is. Ports like to be as straight as possible. My local HD/Lowes only sells their big PVC piping in 10 foot lengths... and its around $10 for a piece of 4"... or about $9 for 3". I personally like the look of dual 3" ports. You could be creative and place the ports flanking the driver. The easiest to engineer would be a single 4" port.
    I don't have access to your modeling, but I can guarantee that 2" stuff is not the way to go... no matter how many you use.
    Did I miss it, or did you say how much volume this box is going to be?
     
  13. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    its going to be 2.7 cubic feet. When i plug the numbers into winLsd. A single 4" x 27.81" port would yield a vent mach of 0.22 It says anything above 0.16 will cause excessive port noise.

    However a pair of 3" x 32.39" ports have a vent mach of 0.10 and then i'd have to use a 45 degree or 90 degree elbow on them to get them to fit.
     
  14. Brent_S

    Brent_S Second Unit

    Joined:
    Oct 5, 2000
    Messages:
    472
    Likes Received:
    0
    Trophy Points:
    0
    Dave,

    I think you're mixing measurement systems. WinISD reports air velocity in m/s. At sea level, .10 Mach works out to 34 m/s. The older versions of WinISD say to aim for 34 m/s, while the newer documentation says 17 m/s. Not sure why the change, but Peerless has a white paper that recommends .1 Mach as an upper limit, but obviously, the lower, the better.

    A 4" port has nearly the same area as 2x3" ports, so it looks like you changed some other parameter in your models along with port diameter, most likely power.

    For 278 watts into a 2.7 ft^3 @ 20hz box with your Eclipse parameters I get:

    2-3"x32.93" = [email protected], [email protected]

    1-4"x28.3" = [email protected], [email protected]

    Either should breathe fine with your chosen amp...if you ever go to a bigger amp, you'll want more port area.

    Just for fun...
    1-3"x15.37" = [email protected], [email protected]

    When you actually design/build your box, don't forget those ports consume space in your box. Your gross internal volume = 2.7 + driver displacement + port tube displacement + bracing displacement + amp displacement if cabinet mounted.


    wbs
     
  15. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    Thanks for the heads up Brent.. yes i just realized that I left the power at 500 watts instead of 278. If the 4" port will work i'll go with that since it will be easier for me and i think if i change the dimensions of my enclosure a little bit I can get a straight port to fit into the enclosure with 3" of space between the wall of the enclosure and the port.
     
  16. Dave Kot

    Dave Kot Auditioning

    Joined:
    Feb 19, 2006
    Messages:
    9
    Likes Received:
    0
    Trophy Points:
    0
    Ok so I recieved almost everything from partsexpress... my amp is on backorder for 2 months which is ok i guess cause it will give me time to thouroughly research my enclosure and take my time building it. Ok so the final plan is this if no-one has anything to add I will go ahead and start planning the build.

    2.7 ft^3 tuned to 20hz with a single 4" x 28.3" port.



    Should be nice I am gonna use autodesk inventor to make some 3d models of the enclsoure before i build it. From the looks of it with the port, subwoofer, and brace displacements outside volume of the enclosure is going to be around 4 ft^3 which is about what i was thinking it would be.

    Thanks for all the help and insight into my project.
     

Share This Page