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Discussion Starter #1
I currently have this setup in my car.



The subwoofer in question is the Illusion Audio Luccent Im-12 in a sealed enclosure measuring about 1.5 cu ft.

I intend to add one more of these Luccent subwoofers that i just purchased, but intend to keep the install as neat and unobtrusive as possible.
I have been suggested an Isobaric install, where the front of the 2nd sub will be placed facing the front of the already present sub (Clamshell design).

I have read quite a bit on clamshells and isobaric subwoofer setups, and have noted that almost everyone says that this setup behaves like one subwoofer and takes double the power, with the advantage of just halving the volume required.

My prerogative of adding another subwoofer is definitely not to increase the SPL levels, but to improve the sound quality. The general consensus is that subs mounted in isobaric form are quicker and blend better with the front stage. I intend to do the same thing.

The Luccent Sub is anyways a very lightweight sub with razor sharp reflexes, and its forte was never to 'cause a din' or 'break db records'
The current setup in my car doesn't even allow me to feel that there is a sub firing in my boot, and I intend to keep it the same even after the 2nd sub comes in.

My question to you'll is: Am i doing the right thing by going isobaric? Anyone has a better way of doing this? I do not want to replace the enclosure that is pictured. I dont mind making some modifications to it, but I need to keep this, since I just got it a month back.


Some photos of the present enclosure:



 

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If you are going to keep the enclosure and not even get the gain of being able to use an enclosure half the size, I see no good reason for you to do this to be honest.
 

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Discussion Starter #3
so how do i go about the second sub? as i mentioned, i dont want to increase the spl level by adding it. i want it to go in unmentioned, and only bolster the lower frequencies. something that one sub wont do.
SQ is priority. SPL is a no no..
 

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The point of isobaric is to use an enclosure half the size and have the same output.

To do it effectively you'd need to model it up properly. It was more popular when subwoofers needed larger enclosures.
 

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Discussion Starter #5
i read that falkenbd. but my question still stands: is there a better way to mount my second sub in this case?
 

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so how do i go about the second sub? as i mentioned, i dont want to increase the spl level by adding it. i want it to go in unmentioned, and only bolster the lower frequencies. something that one sub wont do.
SQ is priority. SPL is a no no..
2 subs, turn volume down...
 

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Well, you can't "bolster" the low frequencies without adding SPL so you can try tuning more low end in your current setup with an eq but that will still add SPL, just in the lower octaves.
 

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Discussion Starter #8
wont adding the second sub in any other form (other than isobaric clamshell), only add to the SPL levels?
 

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Yes. The subwoofer level will be controlled from eclipse 7200mkii. But i intend to ask, will adding a second sub aid in improving the sq? And how? which is the best way to mount the second sub if i wish to improve the sq in the best possible way? Spl levels i can keep in check.
 

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Yes. The subwoofer level will be controlled from eclipse 7200mkii. But i intend to ask, will adding a second sub aid in improving the sq? And how? which is the best way to mount the second sub if i wish to improve the sq in the best possible way? Spl levels i can keep in check.

BAsically right now you don't have enough lowend. So either the enclosure is wrong or you aren't feeding the sub enough power. And each has an effect on the other.

Is the enclosure built to recommended specs?

Did you model it in WinISD?
 

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so how do i go about the second sub? as i mentioned, i dont want to increase the spl level by adding it. i want it to go in unmentioned, and only bolster the lower frequencies. something that one sub wont do.
SQ is priority. SPL is a no no..
Hi Frank, I am a bit confused as to what you mean by "...bolster the lower frequencies." As you are saying "SPL is a no no," then apparently it is not loudness, so is it a lack lowest frequency output or perhaps a lack of punchiness/impact? It would also help if you described the rest of your system for blending purposes and affect on 'bass'.
Also, I'm not familiar w/ this Luccent IM-12. Do you have the T/S parameters? Looking to see how it compares to the ND-12.
 

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technically another sub will add to the SQ because 2 will reach the same level with less distortion.

for missing low end, i'd say redesign the enclosure. Maybe change aiming, maybe make it a vented enclosure.

You could measure the FR of your current setup and try to figure out what is missing the lowend. Maybe adding polyfill or wood blocks to the enclosure could help shape the FR towards your liking. Maybe you need to lower your crossover point. It really depends on exactly what is happening.

There isn't a quick solution to a question as vague as "how to bolster my low end"

Give us a better idea of what is missing.
 

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Discussion Starter #14 (Edited)
BAsically right now you don't have enough lowend. So either the enclosure is wrong or you aren't feeding the sub enough power. And each has an effect on the other.

Is the enclosure built to recommended specs?

Did you model it in WinISD?
the enclosure is built to the recommended specs. in fact, the illusion luccent sub is known to be very flexible when it comes to its enclosure. I am feeding the sub 25W more than its rated RMS power (300W @ 4ohms), so i think that's decent enough headroom.

Hi Frank, I am a bit confused as to what you mean by "...bolster the lower frequencies." As you are saying "SPL is a no no," then apparently it is not loudness, so is it a lack lowest frequency output or perhaps a lack of punchiness/impact? It would also help if you described the rest of your system for blending purposes and affect on 'bass'.
Also, I'm not familiar w/ this Luccent IM-12. Do you have the T/S parameters? Looking to see how it compares to the ND-12.
the punch is decent. and it blends just perfect. but two subs is always better than one. having 2 subs will surely improve the quality of bass. my query here is, how to mount the second sub, so as to make the setup sound sweeter than it actually is!
the im-12 sounds like a distant cousin of the ND-12. only difference is, the ND-12 has the Carbon fibre cone, and that makes a big difference in demanding tracks, where there is a lot of pacy bass and there's a lot for the sub to handle. that's where the nd-12 comes off as a stellar performer. even the im-12 handles this with elan, but the nd-12 is a better performer.

technically another sub will add to the SQ because 2 will reach the same level with less distortion.

for missing low end, i'd say redesign the enclosure. Maybe change aiming, maybe make it a vented enclosure.

You could measure the FR of your current setup and try to figure out what is missing the lowend. Maybe adding polyfill or wood blocks to the enclosure could help shape the FR towards your liking. Maybe you need to lower your crossover point. It really depends on exactly what is happening.

There isn't a quick solution to a question as vague as "how to bolster my low end"

Give us a better idea of what is missing.
sometimes, the bass has that hunting feeling, maybe doesnt punch you low down in the back. that's what i meant by 'bolster' the lower frequencies. then again i dont mean i want to increase the decibel levels, but i surely want the 2nd sub, so both can hit the right note together, and hence complete the lower spectrum.
i like the idea of the wooden blocks. might add some, or might damp the insides of the enclosure.
 

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the enclosure is built to the recommended specs. in fact, the illusion luccent sub is known to be very flexible when it comes to its enclosure. I am feeding the sub 25W more than its rated RMS power (300W @ 4ohms), so i think that's decent enough headroom.



the punch is decent. and it blends just perfect. but two subs is always better than one. having 2 subs will surely improve the quality of bass. my query here is, how to mount the second sub, so as to make the setup sound sweeter than it actually is!
the im-12 sounds like a distant cousin of the ND-12. only difference is, the ND-12 has the Carbon fibre cone, and that makes a big difference in demanding tracks, where there is a lot of pacy bass and there's a lot for the sub to handle. that's where the nd-12 comes off as a stellar performer. even the im-12 handles this with elan, but the nd-12 is a better performer.



sometimes, the bass has that hunting feeling, maybe doesnt punch you low down in the back. that's what i meant by 'bolster' the lower frequencies. then again i dont mean i want to increase the decibel levels, but i surely want the 2nd sub, so both can hit the right note together, and hence complete the lower spectrum.
i like the idea of the wooden blocks. might add some, or might damp the insides of the enclosure.
Your premiss that having two subs is better than one may take some examining if you are not getting audible distortion at your admittedly not high output levels. I've run one sub and then added another identical sub/box to get more output, but the quality of the bass stayed the same at lower volumes. To get that bass that may "...punch you low down in the back," you may want to try to take advantage of your subs strengths and run the LP up to about 100 to 120 hz and increase your HP to midbasses accordingly and use your 7200MkII's parametric EQ to give you a bit of judicious boost at about 70hz or so or run RTA if ya got access. This should at least be a start to giving you some midbass punch.
However, from my experiance w/ the ND-12 these subs while being very clean, articulate and having the ability to disappear, what they don't do well is hit/reach the lowest octave w/ authority. Your IM-12 models pretty similarly at 1.5 cuft. for Qtc of .69 and F3 of 58hz. Don't know if you can tune or otherwise EQ that low end authority in and maintain your overall SQ.

OTOH it looks cool to run two subs so just double up the volume to 3 cuft. and check to see if your bridged RF can run into a 2 ohm load.:)
 

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Discussion Starter #16
Your premiss that having two subs is better than one may take some examining if you are not getting audible distortion at your admittedly not high output levels. I've run one sub and then added another identical sub/box to get more output, but the quality of the bass stayed the same at lower volumes. To get that bass that may "...punch you low down in the back," you may want to try to take advantage of your subs strengths and run the LP up to about 100 to 120 hz and increase your HP to midbasses accordingly and use your 7200MkII's parametric EQ to give you a bit of judicious boost at about 70hz or so or run RTA if ya got access. This should at least be a start to giving you some midbass punch.
i am going to try that soon. im in the process of a few upgrades, and will complete the list of upgrades and then try this. sounds like a good idea.

However, from my experiance w/ the ND-12 these subs while being very clean, articulate and having the ability to disappear, what they don't do well is hit/reach the lowest octave w/ authority. Your IM-12 models pretty similarly at 1.5 cuft. for Qtc of .69 and F3 of 58hz. Don't know if you can tune or otherwise EQ that low end authority in and maintain your overall SQ.
absolutely true! these shallow subs dont do the lower frequencies good justice. hence i thought, lets have 2 of them do the same job and then see how it sounds. as of now im going isobaric clamshell, and will post more information as it happens. the enclosure will be modified to accommodate the 2nd sub, so lets see how much of an increase in volume we can get.
OTOH it looks cool to run two subs so just double up the volume to 3 cuft. and check to see if your bridged RF can run into a 2 ohm load.:)
my RF is not supposed to be stable at 2 ohms, and the fact that it does only 80 W per channel at 4 ohms, means its time for it to go. the 2 subs will get their power (for the moment) from my ground zero 4 channel amp, that does 220*[email protected] 4 ohms. 220W is a decent amount of power to the sub, considering its musical acumen and ability to play well even at sub 150W (tried that for a bit too)
lets see how it sounds!?
 
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