My Car Audio VS My Home Audio

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

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

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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.

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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.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

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...

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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

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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New Project: 2003 Pathfinder

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?

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

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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DYohn] wrote:

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ho 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.

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***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." 

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New Project: 2003 Pathfinder

Thanks for all of the replies.

(1) I have already ran several scenarios through WinISD pro and came up with the same results. However, why then do "we" like choosing those 12", 15", and 18", woofers when installation space is not a factor? They are more expensive and take up more room. Why not just put an 8" in a big box and port it? Is there a difference in SPL?

(2) Let's say I remove my 10" polk, modify the box, and port for an 8" sub (polk or other brand). Let's also just say that the existing volume of the box will be oversized for an 8" sub in the manner we have been talking about. When I put my favorite CD in (John Denver - just kidding) and crank up the bass and power will I say (A) "Man! What a huge increase in bass" or (B) "Man - this 8" sub does not hit near as hard as my 10"

You guys are putting new ideas into my head - my wife will not be pleased [:>)

mrmsudawgs wrote:

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You guys are putting new ideas into my head - my wife will not be pleased [:>)

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Yea...Im sure they have done that to alot of people. 

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mrmsudawgs wrote:

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. However, why then do "we" like choosing those 12", 15", and 18", woofers when installation space is not a factor?

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Because it is easier to produce low frequency sound at higher SPL with larger diaphram drivers than it is to do so with smaller diaphrams.  Plus one should never underestimate the "wow that looks cool" factor in car audio.  Just ask all the kids who buy chrome-plated woofers and amps covered with flames and skulls.

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mrmsudawgs wrote:

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(1) I have already ran several scenarios through WinISD pro and came up with the same results. However, why then do "we" like choosing those 12", 15", and 18", woofers when installation space is not a factor? They are more expensive and take up more room. Why not just put an 8" in a big box and port it? Is there a difference in SPL?

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You just answered your own qustion. Why put a smaller sub in a larger box when you could put a larger sub in a larger box?

Larger subs have more cone area which reduces the need for high excursions which reduces the requirement of alot of power.

Also, you must remember that home speakers are almost always more efficeint then car speakers because they're designed with no space limitatoins.

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Okay - I ran several scenarios through WinISD. Basically, no matter what size driver I put in a 0.74 cubic foot box the port's length becomes a problem. WinISD shows a nice looking graph when tuned to 40 hz but 40 HZ just seems too high to me - might sound boomy. The port's length was the reason I went with a sealed enclosure in the first place. Even with an 8" driver the port length is a problem.

Back to the inital question about my home theater system versus my truck's system - okay, I understand that now. Give me infinte room to build me a box and I can build you a great sounding, efficient enclosure. There are many physical constraints to be considered in car audio that forces one, like me, to build to what is available. I did that and I matched a great sub to go in it.

Do I wish I had started with an 8" in a vented enclosure? No because I would then wonder how that 10" would sound. Will I change my system? No because I am very happy with it now. The bass gets really low and it stays very tight. I like it even though I know I could make it go lower with porting and a larger space to build an enclosure.

Wait a minute - larger space?? I have it!!   I could remove my back seat! I'd have tons of room then. No wait, the kids ride back there. Oh, I know! I'll put a cover on my bed and build a large box back there. With that much room I don't have to use an 8". Heck, I'll use an 18"!!! Cool! But I'll have to have more power, a new alternator, cut my truck's sheet metal to port into the cab......SOMBODY STOOOOOPPPPPP MMEEEEEEEEEEE!!!!

Mike