enclosure type

[mouettus]

all right. this is a car audio question. but your knowledge of home theater applies here.

I want to get a new subwoofer in my car. Mine is presently a 12" infinity reference sub in a closed box. The problem is that I mainly listen to heavy metal/rock music. I find my subwoofer to be a little too boomy for my taste (even in a closed box). So I decided to downgrade the woofer size to 10 inches so it could be faster, which is what I'm looking for. I just want to be able to hear the bass drums from the sub. Now the question is: should I stay with a closed box or go ported? Would I lack SPL in a closed one? Would it still be boomy in a ventend one?

*Sub would be the 10" Infinity Kappa 102,7w
· 10" subwoofer with selectable 1- or 4-ohm impedance
· Recommended RMS Power: 350W
· Sensitivity: 89 dB
· Rec. Sealed Box Dims: .65 - 1 cu.ft.
· Rec. Ported Box Dims: 1 - 1 cu.ft

 

[avaserfi]

I think one thing you should realize is that car audio and home audio are different beasts and that a properly designed 12" woofer will be just as musical as a properly designed 10" in a well acoustically treated room. I believe you are talking about excursion when you say 'faster' which is how far in and out the sub would need to move to produce a signal. In reality the 10" would need to have a greater excursion than the 12" to produce the same SPLs, especially at lower frequencies, as it can move less air since it is a bit smaller.

I have a feeling this boomyness is not due to it being a sealed box/ported etc...What the boomy situation is likely due to is the sound waves interacting with the car. Just like a poorly treated home theater room your car is likely causing a slow decay of these waves thus the boomy sound.

While I don't know too much about car audio I wouldn't expect getting a smaller driver to fix the problem at all.

 

[j_garcia]

Have to agree with all of that. If the box is designed properly, there is no real advantage to a 10" over a 12". All subs reproduce sound at the same speed. Another factor is actually calibration and proper setup - how is the sub crossed over? Have you adjusted the level of the sub relative to the rest of the system? Just like in home theater, you need to properly integrate the sub with your system for the best sound.

 

[mouettus]

i work at a car audio store and I can tell you by listening to all kinds of subs that a 10" has a cleaner sound than a 12" but is less powerfull in the very low frequencies. What I meant by boomy is that a 10" woofer is generally faster to return to it's original position. Woofer sizes isn't all about how much space you got to put it or how much SPL they put out. The only thing I want is SQ.

My system is properly calibrated. My amplifier is set to passthrough and my car deck crossover is set at 50.

Finally, could my amplifier have something to do with that? I'm not quite sure that it's powerful enough :S (even though my gain setting is pretty low cuz I like the bass to blend with the rest of the music). This impedance thing is driving me crazy lol

 

[annunaki]

10" woofers are not faster than 12" woofers. It is a common myth. The fact is, that a 12" woofer has more output than a 10". It also playes deeper due to the increased surface area. What you are experiencing is the subwoofer running too hot. Meaning the level is too high. Deep bass at a high output level will always sound "boomy". Have you ever just listened to a subwoofer with no midbass, mid, or high range playing? They all sound very similar for the most part.

See this link for myths with subwoofers: http://www.audiopulse.com/know-how/subwoofer-driver-guide/myths-about-subwoofers/

Midbass is usually the weakest link in a car audio system. Many people put in a few subwoofers and amplifiers and just replace factory speakers with basic coaxials. Some may run an amplifier on these to help but very few treat the acoustical space around the speaker properly. Even fewer people design proper enclosures for their midbass drivers. Much of the "speed" and "quickness" that car systems seem to lack is due to this issue. Proper enclosure design for the car is the same for home audio. T/S parameters must be used and modeling needs to be applied to identify the correct enclosure.

The fact that the car audio environment is very conducive to bass amplifies the effect of having more bass capability than midbass, mid, high range.

If a 10" woofer were quicker to return to it's original position it would be playing a different frequency altogether. 60hz is 60 cycles a second. If a woofer moves any faster or slower than that, the frequency changes.

If your crossover is set to 50hz low pass, what is the slope? My guess is that because you have such a low crossover point the lowest frequencies are quite loud causing a "boomy" sound. You system has a general lack of response in the critical 60hz-200hz range resulting in your problem. I would also guess that you do not have dedicated mid-bass drivers.

Gain controls on car amplifers mean nothing as to how much they are "turned up". It is possible for a car amplifier to make full power at 0 gain with a high voltage output deck. What kind of head unit do you have? What is the output voltage? What is the input voltage range for the amplifier?

 

[annunaki]

As far as the enclosure goes, I would suggest a sealed enclosure with a QTC of .707. They typically work best in the car environment. Because of the transfer function in automobiles, you could try a sealed enclosure that is slightly over damped at a QTC of .600 and rely on the transfer function to help out a bit more. It may give you the accuracy you are after.

 

[mtrycrafts]

i work at a car audio store and I can tell you by listening to all kinds of subs that a 10" has a cleaner sound than a 12" but is less powerfull in the very low frequencies. What I meant by boomy is that a 10" woofer is generally faster to return to it's original position.

Working in a audio store is great, but doesn't immunize one from picking up audio myths along the way. Annunaki gave you a great link and learning tool about audio science and subs specifically. Most interesting info in there

 

[Sheep]

Have you tried dampening the box a bit? That could help alleviate the booming, and would be the cheapest fix to your problem.

SheepStar

 

[annunaki]

Most enclosures for car subs are designed with the thought in mind that the car (due to a highly confined area) will boost the lowest frequencies by an extreme amount. This is the case with many "recommended enclosures". However, they are typically high QTC enclosures (generally around 1.0) and tend to ring or in this case become "boomy" near the resonance point. If sound q is in mind I would look to a potential redesign of the enclosure by first running it (T/S parameters) through a design program. Sealed is typically my choice here. This may be the difference in sound you are hearing in 10" vs. 12" subs. 10" woofers recommended enclosures tend to be at or very near .707 QTC. Where as most recommended 12" enclosures are almost always too small resulting in a higher "Q".

I did design an ported enclosure for my brother that he uses in a Pontiac Grand Prix. It is a JL Audio 15W3v2 with 500 watts rms. The woofer is extremely linear and offers 3/4" linear one way excursion. It is tuned to 20hz with the equivalent of a 5.5" port (slot vent). This system is unbelievably accurate in terms of bass yet will literally make your head feel as thoughit will implode. Hearing protection in this car is a MUST. It plays extremely deep to boot, useable response down to 10hz. It is one of the "tightest" systems I have ever heard.

If careful attention is used during design ported enclosures will work as well. However, they will have more output so that must be accounted for.

 

[tubesaregood]

i work at a car audio store and I can tell you by listening to all kinds of subs that a 10" has a cleaner sound than a 12" but is less powerfull in the very low frequencies. What I meant by boomy is that a 10" woofer is generally faster to return to it's original position. Woofer sizes isn't all about how much space you got to put it or how much SPL they put out. The only thing I want is SQ.

My system is properly calibrated. My amplifier is set to passthrough and my car deck crossover is set at 50.

Finally, could my amplifier have something to do with that? I'm not quite sure that it's powerful enough :S (even though my gain setting is pretty low cuz I like the bass to blend with the rest of the music). This impedance thing is driving me crazy lol

First off, a 10" subwoofer will not necessarily return to the same position faster than a 12" - that's rubbish. Why? Because inertia is a function of mass, not size. Pressure helps this effect in speaker enclosures as well. Imagine an 18" woofer with a low mass aluminum cone in a very small, high pressure sealed box. Now imagine an 8" woofer in free air with a high mass damped paper cone. Which do you think is "faster?"

Also, the amplifier is able to provide plenty of power, I'm sure.

 

[mouettus]

alright... I'll try to answer a couples of question here. first I'll post my gear:

Head unit: Pioneer DEH-P3600
Crossover settings: 50, 80, 125 (set to 50 here, with a -1db gain)
No slope control
Parametric EQ (always changing the settings depending on the album/recording)

Front speakers: Infinity 6020cs running from the deck
6½ Component speakers with woofers in doors (oringinal position) and tweeters couple of inches higher, turned upwards a little to have better imaging

Rear speakers: Inifnity 6012i running from the deck
6½ 2-way speakers in original position (rear deck)

Subwoofer: Infinity 1230w
12", 350 watts RMS, running @ 4ohms
Sealed enclosure (I'll have to recalculate the volume here, not sure)

Sub amplifier: Rockford Fosgate 200M
200 watts RMS Monoblock amplifier pushing only 100 watts RMS in 4ohms --> maybe this is a problem.
Gain is set to +6db (best setting to my ear), crossover set to passthrough




Although you might be right that a 10" isn't faster, I still hear a great difference between the two sizes when I demo some gear at work. Faster shouldn't be the word then. Punchy maybe?? And no working in an audio shop doesn't mean that I know everything. That's why I'm here. To learn more about audio!!! BTW, could you explain me what QTC means?

 

[annunaki]

The qtc is more or less how strong the resonance is in the enclosure. The higher the number the stronger the resonance effect will be, i.e. boomy bass. Essentially it creates a hump in response much of the time near 60hz in subwoofer systems. A QTC of .7 or so is generally the best balance between a resonance peak and being overdamped. In other words it has the smoothest, flatest response curve.


As far as the difference between the sound of a 10" and a 12", I explained that in my last post. A 10" in a recommended sealed enclosure is usually closer to a .7 qtc than a 12" in a "recommended" sealed enclosure. The 12" is closer to a qtc of 1.0 in most cases (because it relies on the car's confined space to boost the low end. This is done simply to keep the "recommended" volume smaller. I have seen resulting in what may seem as a more boomy or less accurate sound.

 

[Wafflesomd]

Where's Wmax?

 

[annunaki]

The sub you have should work very well for a sound quality type system. You most likely need to do a new enclosure with a lower "Q". A bit more power may help but will not necessary. If you can get me the T/S parameters for your subwoofer I can get you the appropriate volume requirements for said enclosure.

Again, please refer to my previous posts regarding midbass. Many people with your musical tastes have much the same "problem" with their bass. The problem is the lack of midbass, and I am guessing, the enclosure size for the current subwoofer. A larger amplifier will help you out in terms of dynamic capability as well (for the sub).

In the mean time, up your crossover point to around 80hz on the sub lowpass and 80hz highpass on your infinity speakers. Crossover points can be very crucial in the car environment. higher order slopes like 24db/oct. are usually very helpful as well.

Have you done any sound treatment to the woofer location in the doors or rear deck? Dynamat or other similar types of products can help greatly there.

 

[no. 5]

Where's Wmax?

Playing croquet...

 

[mtrycrafts]

Although you might be right that a 10" isn't faster, I still hear a great difference between the two sizes when I demo some gear at work. Faster shouldn't be the word then. Punchy maybe?? And no working in an audio shop doesn't mean that I know everything. That's why I'm here. To learn more about audio!!! BTW, could you explain me what QTC means?

Don't forget though that humans a biased by nature, subconsciously and it is not something that can be turned off or on. So, who knows what you really hear or don't hear if one's bias dictates things or masks reality at times.
Perhaps one 10" has a different frequency response than the next larger one and may be audible.
Without careful comparisons, measurements, not from the maker, it is hard to be objective about these things.

 

[mouettus]

The sub you have should work very well for a sound quality type system. You most likely need to do a new enclosure with a lower "Q". A bit more power may help but will not necessary. If you can get me the T/S parameters for your subwoofer I can get you the appropriate volume requirements for said enclosure.

Again, please refer to my previous posts regarding midbass. Many people with your musical tastes have much the same "problem" with their bass. The problem is the lack of midbass, and I am guessing, the enclosure size for the current subwoofer. A larger amplifier will help you out in terms of dynamic capability as well (for the sub).

In the mean time, up your crossover point to around 80hz on the sub lowpass and 80hz highpass on your infinity speakers. Crossover points can be very crucial in the car environment. higher order slopes like 24db/oct. are usually very helpful as well.

Have you done any sound treatment to the woofer location in the doors or rear deck? Dynamat or other similar types of products can help greatly there.

t/s parameters? another term I need to learn about!

for the crossover settings, I seem to like 50 better than 80 (wish I had 63 like in the new pioneer head units). I've had the same equipment for over a year and a half now and I always seem to like better 50. Less boomy that way cause the speakers are picking up the lower guitar notes instead of the sub. I'll try it anyways. And like I told you, I can't play with the slopes very well. What you said about midbass is true by the way, I really like boosting the 200ish hertz band with my parametric eq. But still, they lack the kick I'm looking for. Maybe powering them with a 4 channel amp would make 'em alive instead of running them from the deck's amp.

and finally yes, I have dynamat as sound treatment for all my speakers. Basic treatment though. I haven't made enclosures so they are running with the air in the door/trunk (but that has nothing to do with my sub problem).

 

[annunaki]

t/s parameters? another term I need to learn about!

and finally yes, I have dynamat as sound treatment for all my speakers. Basic treatment though. I haven't made enclosures so they are running with the air in the door/trunk (but that has nothing to do with my sub problem).

If you have not designed the enclosure based upon the Thiele Small Parameters for the sub , I would say that this is the issue. They are a set of electro-acoustical parameters of the subwoofer. Using the parameters and some math one can figure out what type of enclosure the woofer is best suited for as well as design the best sounding enclosure for said woofer.

As far as the dynamat goes, have you covered the whole door so as to eliminate any air movement from the front of the door to the back or vice versa? Your midbass response has much to do with your sub problem. The better midbass response you have the easier it will be to get the sound you are after as well as integrate the sub. You have to look at the sub as just a piece of the system. The importance of everything is how the system functions as a whole. Improving the midbass response will blend the sub better, and allow the use of such a low x-over point. Redoing the enclosure for the sub will also improve this as well. It may allow you to move your x-over point up some.

 

[mouettus]

If you have not designed the enclosure based upon the Thiele Small Parameters for the sub , I would say that this is the issue. They are a set of electro-acoustical parameters of the subwoofer. Using the parameters and some math one can figure out what type of enclosure the woofer is best suited for as well as design the best sounding enclosure for said woofer.

As far as the dynamat goes, have you covered the whole door so as to eliminate any air movement from the front of the door to the back or vice versa? Your midbass response has much to do with your sub problem. The better midbass response you have the easier it will be to get the sound you are after as well as integrate the sub. You have to look at the sub as just a piece of the system. The importance of everything is how the system functions as a whole. Improving the midbass response will blend the sub better, and allow the use of such a low x-over point. Redoing the enclosure for the sub will also improve this as well. It may allow you to move your x-over point up some.

So all in all... what do you recommend me to do first? Getting my brother in law (carpenter) at work by designing a new sub enclosure or treating my whole door with dynamat? Winter is coming... it is already "too late" to work on my car! lol Building a new sub enclorsure shouldn't bee too hard though. The manual recommends something between .5-1 cubic feet of volume. That's all I know.

Btw... I just tried the 80 hertz crossover point on my system. A little better I must admit

 

[annunaki]

So all in all... what do you recommend me to do first? Getting my brother in law (carpenter) at work by designing a new sub enclosure or treating my whole door with dynamat? Winter is coming... it is already "too late" to work on my car! lol Building a new sub enclorsure shouldn't bee too hard though. The manual recommends something between .5-1 cubic feet of volume. That's all I know.

Btw... I just tried the 80 hertz crossover point on my system. A little better I must admit

You will need to get the T/S parameters from the manual. As I suspected that seems a bit small for a 12" driver.

They are usually listed as:

Fs
Qts
Qms
Qes
Vas
Sd
BL
Mms
Re
Le
Pe (RMS power)

and sometimes more.

Once you have those, I can run them in a modeling program such as WinIsd and find the appropriate sealed enclosure based upon its electo mechanical properties/parameters.