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My Car Audio VS My Home Audio


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mrmsudawgs 
Copper - Posts: 145
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Joined: February 22, 2005
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Posted: March 29, 2005 at 8:58 PM / IP Logged  
Why does my Velodyne CHT-8( specs here) powered sub in my home theatre system have deeper base than my 10" Polk MOMO 2104 ( specs here) installed in my truck (shown here) Granted, the Velodyne is in a vented enclosure and my Polk is in a sealed enclosure but it's an 8" versus a 10" sub and the 8" is winning. Is it room gain?
Opinions?
Mike
Steven Kephart 
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Posted: March 29, 2005 at 9:11 PM / IP Logged  

Actually your vehicle will have a lot more room gain than your home.  There are several possibilities why.  My guess would have to do with lower tuning, quite a bit of EQ on the HT subwoofer, and probably some peaking in the response at say 35 Hz or so to give the impression of more low bass than there really is. 

I did notice that the resonant frequency on that Momo sub is somewhat high.  Add to it that you might be using an enclosure on the small size for the sub (only a guess) and you will run into a peakier response with less low end.  The solution is to increase the size of your enclosure.  That will give you the low end you desire.

Steven Kephart

Adire Audio

Chad7n7 
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Posted: March 29, 2005 at 9:26 PM / IP Logged  

I agree with Stephen, your enclosure sounds to be your limiting factor.

Your enclosure in your truck is on the small side, which will limit your low end. I know, through reading your past threads, it was designed/built with space restrictions. As opposed to your HT enclosure, which are designed for optimal performance, not the space it takes up.

stevdart 
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Posted: March 29, 2005 at 10:18 PM / IP Logged  
Steven and Chad covered this for you very well.  I'll help to put it in perspective - the home sub enclosure is twice the volume as the one in the truck, however the 8" sub at home is only about 2/3 the size of the 10" truck sub.  So it's not only getting twice the air volume, it's getting that much more plus the relative difference in sub size, too.  Compare the ratios 1:1 to 0.66:2 which is comparing relative sub surface area to box volume.....the home sub, in reality, has 3 times the air volume in its enclosure than does the truck sub.
Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
customsuburb 
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Posted: March 29, 2005 at 10:27 PM / IP Logged  
I have the cht-8. It's a great little home theater sub. It can move alot of air for an 8" sub. The woofer it comes with kind of reminds me of an 8" koda...
mrmsudawgs 
Copper - Posts: 145
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Joined: February 22, 2005
Location: United States
Posted: March 29, 2005 at 10:50 PM / IP Logged  
I suspected as much about the small speaker in a big volume but that leads to even more questions:
(1) My enclosure size is 0.74 cubic feet. Polk recommends 0.66 so I'm a little larger than they recommend. Going even larger - say to 1 cubic foot - might damage the woofer by letting it go to full excursion much like a ported box. Is that correct?
(2) Why then, if given the choice between a single 8" sub in a vented, oversized box and a 10" sub in a sealed enclosure of recommended volume, would one choose the 8" sub? Will not a 10" sub out perform an 8" sub in the same way a 12" sub will out perform a 10"
Mike
My Car Audio VS My Home Audio -- posted image.
kfr01 
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Posted: March 29, 2005 at 11:25 PM / IP Logged  
mrmsudawgs:
The best way to see this in action is to download WinISDpro and load up a bunch of different drivers in different boxes.
You'll quickly see that the resulting estimated response curve is -both- a function of the particular driver used and the particular box.
If you load up WinISD try this. Open a Shiva (12") and use a sealed box with a Qtc of .707. Now open another Shiva and run it ported with an SBB4 alignment.
Now, you can see that the larger ported box brings extension down into the 20s, with -3db below 25hz!
The sealed box is -3 db near 40hz.
No matter how big you make the sealed box you will not achieve the same low frequency extension without equalization. You simply can't; you could make the enclosure the size of your house.
Velodyne picked an 8" because they could achieve good response ported in a relatively small box. A 10" would have required a larger box. Smaller boxes sell, especially when a wife-factor is involved. But otherwise, yes, for maximum low frequency HT performance the larger the sub the better, generally.
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stevdart 
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Posted: March 29, 2005 at 11:26 PM / IP Logged  

1.  No, you can normally go very large with either type of enclosure.  For vented, the port volume has to be correct according to the enclosure volume.  Given that necessity for a vented box, for either type it is overpowering that causes overexcursion.

2. First, refer to #1.  Then, for one, one would choose whatever sub is in it's ideal enclosure for the parameters that the sub has.  And as long as the two subs are equal in quality.  A 12" sub will not perform better than an 8" sub if the former is confined to too small, or the wrong type, of an enclosure and the latter has the Taj Mahal.

Use your WinISD program for clues to this.  If you'll put various subwoofers into the database and bring them up, just clicking thru the boxes for automatic suggestions, the program will come up with the best size and type of enclosure given the specs that you entered for that sub.  It just looks at a flat response of a Q at .707 if the situation calls for a sealed enclosure.  It doesn't care what your putting the sub in...a car, a house, a boat, a stadium...so you'll see that sometimes you'll get responses like 10 cu. ft. for a sealed and things like 5 ft for a port with some vented types.  This gives you an indication that oftentimes a speaker is not going to perform as well as it mathematically can within the confines of the environment you want to put it in.  Manufacturers of car audio are well aware of that restrictive environment, and so they will give you a "reasonable" range of enclosure sizes that you can use.  Home audio is much easier because of the room you have there, so you will see 8" subs in enclosures that car audio sometimes tries to fit two twelves into.  That make sense?

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
DYohn 
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Posted: March 29, 2005 at 11:29 PM / IP Logged  

Who said a 12" sub will necessarily outperform a 10" sub?  I've build systems using a  6.5" sub that easily "outperformed" certain 12" subs.  It depends on how the speaker is designed and made, how it is being used, how it is aligned, how it is powered and Eq'd, and how it is installed.  Cone size, by itself, means nothing without taking many other factors into consideration.  It also depends on what you mean by "outperform."

I also own one of THESE, the Sunfire Super Junior.  Although it is not my favorite system, this subwoofer uses 6" drivers and produces bass output that measured in both frequency response and SPL rivals most systems using much larger drivers.  Size does not always matter.

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kfr01 
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Posted: March 30, 2005 at 1:27 AM / IP Logged  
DYohn wrote:
Who said a 12" sub will necessarily outperform a 10" sub?  I've build systems usinga  6.5" sub that easily "outperformed" certain 12" subs.  It depends on how the speaker is designed and made, how it is being used, how it is aligned, how it is powered and Eq'd, and how it is installed.  Cone size, by itself, means nothing without taking many other factors into consideration.  It also depends on what you mean by "outperform."

I also own one of THESE, the Sunfire Super Junior.  Although it is not my favorite system, this subwoofer uses 6" drivers and produces bass output that measured in both frequency response and SPL rivals most systems using much larger drivers.  Size does not always matter.

***sighs of comfort***   Posts like this is what makes the12volt my car audio forum of choice.  The other forums are bubbling over with newb SPLers whose analysis ends at "cone area * xmax." 

New Project: 2003 Pathfinder
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