Infinite baffle subwoofer

[edouble101 314]

So yet again for the umpteenth time I am changing my sub bass setup. Now that I have an excellent sounding front stage an over powering sub system ruins it. My front stage is also very loud, loudest front stage I ever had. Although I am not looking for the output I have had in previous sub bass setups it still needs have a volume level to match my front stage. One thing I can not have is a large enclosure. Largest possible would be 3 cubes gross.

I am thinking about going IB. I would not have to mess around with an enclosure and from what I have read they are the most accurate sounding sub bass types. I keep eyeing up the Fi IB3 series but what other options are there? My trunk is fairly small (2008 Hyundai Elantra) as well. Is there adequate airspace in the trunk to use two 15" drivers IB?

Edited September 4, 2012 by edouble101

[ricksi30 923]

My first thought was the IB3's, or you could check these out http://www.parts-exp...tnumber=295-455

[ricksi30 923]

Why not just one badass 12 ported?

[ssh 924]

I think IB could be very sweet, but I'm not sure if the trunk would be enough an 18", and a 12" or 15" may lack the output you desire--hard to say since I don't know how loud your looking for it to be. I'm pretty sure there is a chapter in the Cookbook about IB.

I've only heard one IB setup, a 12" Dynaudio Esotar2 1200, and it wasn't shaking mirrors, but it had enough output to match the front stage. It happened to be a SQ install, and the midbass was toned down a bit, so the bass could also have been as well.

Edited September 4, 2012 by stefanhinote

[Impious 1,476]

It depends on what you mean by "most accurate". Distortion is higher with sealed/IB than a ported enclosure playing near tuning, although distortion is also much less audible in the subbass region. Transient response depends on where the final Qtc ends up being at, although generally the damping will be probably better than ported. One of the nice things is that pressure is much closer to even on both sides of the cone which can solve some linearity issues. I've ran IB for several years, haven't used an enclosure in years and have no desire to do so, except for a couple weeks last year which was just for shits n giggles. The space savings is simply phenomenal, sound is still very good and low end efficiency is improved.

What do you have for an EQ? Home audio oriented IB subs such as the IB3 will end up being extremely bottom heavy when installed in a vehicle due to their high Qts and low Fs so the low end will always need tamed down. Likewise and especially in a small'ish trunk, they'll often experience an increased Qtc as well which may or may not bump it up beyond an acceptable level for your listening tastes due to their already high Qts.

Personally I've had best luck with low-mid Qts and low Fs subs. My last IB sub was an Exodus Shiva-X with a Qts around .4 and Fs around 20hz. The bottom end was still strong and still needed EQ'd down a bit to be closer to flat, although I didn't mind the mildly heavy bottom end as it wasn't overbearing.

Any sub can be ran "infinite baffle", you just have to be able to predict how it will respond and see how it matches your goals and/or if you have the EQ to fix response issues. In car audio there are typically two options to achieve relatively flat in-car response without much EQ.....low Q/Low Fs and high Q/High Fs. Those two options keep the F3 on the higher side to keep the low end from bloating once cabin gain is considered. The high Q/Fs route may have the problem I noted above of too high of a final Qtc depending on trunk space, which is why I like the lower Q/low Fs option the best as you'll almost always end up with an acceptable Qtc even if you carry some shit in your trunk. High Q low Fs drivers like used in home audio have a very low F3 which when combined with cabin gain needs tweaked to get right and they generally have a very large Vas so they experience an increase in Qtc once installed in a vehicle trunk.

What is your budget for subs?

[edouble101 314]

Thanks for the explanation Impious.

I have a P99RS head unit. Independent L/R 31 bands eq, fully adjustable xover.

Budget is $500 for sub(s).

[///M5 2,833]

Now that I have an excellent sounding front stage an over powering sub system ruins it.

Turn down the sub and use the eq you have to solve it. No longer ruined. No money spent.

[edouble101 314]

Now that I have an excellent sounding front stage an over powering sub system ruins it.

Turn down the sub and use the eq you have to solve it. No longer ruined. No money spent.

That is exactly what I did. Lugging around a big enclosure and 65lbs sub and 4500wrms amp that isn't being used is pointless though.

The biggest goal is too have a small footprint enclosure or none at all.

[edouble101 314]

These specs are not Shiva or Maelstrom but they look good for IB

15" D2

Re: 3.7 Ohms

Fs: 18.5 Hz

Qes: 0.37

Qms: 6.3

Qts: 0.35

Le: 3.5 mH

Sd: 80445 mm^2

Vas: 220 l

BL: 18.9

Mms: 309 g

Cms: 239

Sensitivity (1W/1M): 87.4 dB

[Duran 387]

I've been throwing around the idea of IB in my Elantra as well.

[Impious 1,476]

These specs are not Shiva or Maelstrom but they look good for IB

15" D2

Re: 3.7 Ohms

Fs: 18.5 Hz

Qes: 0.37

Qms: 6.3

Qts: 0.35

Le: 3.5 mH

Sd: 80445 mm^2

Vas: 220 l

BL: 18.9

Mms: 309 g

Cms: 239

Sensitivity (1W/1M): 87.4 dB

I spy an SI HT subwoofer.

Excursion is reasonable at 20mm, which is of course important for IB just like sealed enclosures. Models nearly identical response wise to my Shiva-X, low-mid Q and low Fs. Looks good for IB in a vehicle to me.

I dislike recommending specific products, but I believe AE also has the SBP4 which was designed to work well IB in a vehicle and generally John builds a very good subwoofer. No idea on cost though.

[95Honda 486]

I would caution against low-Q drivers for IB unless you have ample displacment availible. I say this because the lower the Q of the sub, the more it self dampens and the less output it has as you go lower in frequency without augmentation of some kind. In IB, the augmentation comes in the form of EQ, wich takes power. An exponential amount of power as frequency drops. When the driver has a higher Q, it doesn't self dampen as much as you go lower in frequency and requires less EQ on the bottom.

[jonbearsmt 919]

talk to hugo, screen name of onebadmonte he has done a few IB set ups in his car,

[edouble101 314]

These specs are not Shiva or Maelstrom but they look good for IB

15" D2

Re: 3.7 Ohms

Fs: 18.5 Hz

Qes: 0.37

Qms: 6.3

Qts: 0.35

Le: 3.5 mH

Sd: 80445 mm^2

Vas: 220 l

BL: 18.9

Mms: 309 g

Cms: 239

Sensitivity (1W/1M): 87.4 dB

I spy an SI HT subwoofer.

Excursion is reasonable at 20mm, which is of course important for IB just like sealed enclosures. Models nearly identical response wise to my Shiva-X, low-mid Q and low Fs. Looks good for IB in a vehicle to me.

I dislike recommending specific products, but I believe AE also has the SBP4 which was designed to work well IB in a vehicle and generally John builds a very good subwoofer. No idea on cost though.

Yep, SI HT. At $170/ea the price is good. From what I read they are made with Sundown softparts so they should hold up well. I posted on HomeTheaterShack about the preorder but haven't recieved a response yet.

The SBP4 is over $100 more.

[lithium 358]

I use a single mj 18 in my car. matches pretty seamlessly with my sls 8's up front. really enjoy this set up.

edit: the si look pretty sexy!

Edited September 6, 2012 by lithium

[Impious 1,476]

I would caution against low-Q drivers for IB unless you have ample displacment availible. I say this because the lower the Q of the sub, the more it self dampens and the less output it has as you go lower in frequency without augmentation of some kind. In IB, the augmentation comes in the form of EQ, wich takes power. An exponential amount of power as frequency drops. When the driver has a higher Q, it doesn't self dampen as much as you go lower in frequency and requires less EQ on the bottom.

Thankfully we have transfer function to take care of a large portion that EQ function, as long as Fs is low as well (~20hz in my experience) Obviously you don't want Q to be too low, but IME once placed in a vehicle a Qts around .35-.4 with a low Fs provides great in-vehicle response and generally the low end is still a little on the strong side and needs Eq'd down a bit for a truly flat response.

[Impious 1,476]

Yep, SI HT. At $170/ea the price is good. From what I read they are made with Sundown softparts so they should hold up well. I posted on HomeTheaterShack about the preorder but haven't recieved a response yet.

The SBP4 is over $100 more.

Wish AE kept the store on their website more up to date. I couldn't find anything about them on there.

[edouble101 314]

Yep, SI HT. At $170/ea the price is good. From what I read they are made with Sundown softparts so they should hold up well. I posted on HomeTheaterShack about the preorder but haven't recieved a response yet.

The SBP4 is over $100 more.

Wish AE kept the store on their website more up to date. I couldn't find anything about them on there.

Ironically the price isn't listed in their store. Here is where I found it. Second paragraph from the bottom.

Edited September 6, 2012 by edouble101

[codycr6 0]

In my vintage car I have run IB for years, never had an enclosure. I originally used a pair of inexpensive 12's, now I use four 10's. Very easy to end up too bottom heavy, I do recommend a Qts around 0.5 and Fs anywhere from 30-40Hz. I try to get my response curve as close as I can without equalization, and I have yet to need much power to get results. You will want good soft parts and plenty of excursion, but thermal power handling is seldom an issue. And you will love having no box in your trunk!

[Quentin Jarrell 671]

I would think two 15's IB in a trunk would just equal 1) a big leaky sealed box or 2) a big sealed box is sealed up properly.

[///M5 2,833]

I would caution against low-Q drivers for IB unless you have ample displacment availible. I say this because the lower the Q of the sub, the more it self dampens and the less output it has as you go lower in frequency without augmentation of some kind. In IB, the augmentation comes in the form of EQ, wich takes power. An exponential amount of power as frequency drops. When the driver has a higher Q, it doesn't self dampen as much as you go lower in frequency and requires less EQ on the bottom.

Thankfully we have transfer function to take care of a large portion that EQ function, as long as Fs is low as well (~20hz in my experience) Obviously you don't want Q to be too low, but IME once placed in a vehicle a Qts around .35-.4 with a low Fs provides great in-vehicle response and generally the low end is still a little on the strong side and needs Eq'd down a bit for a truly flat response.

I think the caveat put everything on the same page. Other than the general I'd rather make frequency cuts then have a lack of response. Of course this is where something other than a non-adjustable graphic eq can be helpful. My guess though is that edub will still want a bloated response even without the box. The transition never happens overnight.

[NDMstang65 403]

Displacement is king in IB, do the math..you'd have to buy twice as many AE woofers to equal the displacement of the IB3's.

From experience, around .36 on the Qts end is ideal for IB..any lower then that things start acting funky.

[edouble101 314]

Displacement is king in IB, do the math..you'd have to buy twice as many AE woofers to equal the displacement of the IB3's.

From experience, around .36 on the Qts end is ideal for IB..any lower then that things start acting funky.

I would love to use a pair of IB315. The downside is my trunk volume (empty) is 14.2^3ft. High qts and large vas of the IB315's make them less than ideal for my use. Am I wrong?

Edited September 25, 2012 by edouble101

[Impious 1,476]

Displacement is king in IB, do the math..you'd have to buy twice as many AE woofers to equal the displacement of the IB3's.

From experience, around .36 on the Qts end is ideal for IB..any lower then that things start acting funky.

I would love to use a pair of IB315. The downside is my trunk volume (empty) is 14.2^3ft. High qts and large vas of the IB315's make them less than ideal for my use. Am I wrong?

With a pair you would get a slight bump in Qtc, some where in the .9 range....which isn't terrible, but depends on your tastes. However you can only expect Qtc to increase from there as you start piling things in the trunk and reducing the volume of the "enclosure". The other issue is the lower F3 which will probably need more EQ work to flatten out than something that starts a shallower slope higher up in the frequency response.

[edouble101 314]

Displacement is king in IB, do the math..you'd have to buy twice as many AE woofers to equal the displacement of the IB3's.

From experience, around .36 on the Qts end is ideal for IB..any lower then that things start acting funky.

I would love to use a pair of IB315. The downside is my trunk volume (empty) is 14.2^3ft. High qts and large vas of the IB315's make them less than ideal for my use. Am I wrong?

With a pair you would get a slight bump in Qtc, some where in the .9 range....which isn't terrible, but depends on your tastes. However you can only expect Qtc to increase from there as you start piling things in the trunk and reducing the volume of the "enclosure". The other issue is the lower F3 which will probably need more EQ work to flatten out than something that starts a shallower slope higher up in the frequency response.

I looked at the IB315 again. With two of them I can achieve 1x vas each with an empty trunk. I know this isn't ideal and isn't true IB. In the car audio realm what is ideal. I have a 13W6 sitting beside me that I have been seriously thinking about using IB. I was also thinking about buying another. The 13W6 isn't cheap though, selling for about $450 online. I can buy two IB315's for the price of one 13W6. Cost does have somewhat of a factor on my install but if I was going sealed or ported I wouldn't buy any other brand than JL Audio. .....rant over..... More importantly I will have more displacement with two IB315's than with two 13W6. The only thing I am concerned about is a high QTC. I finally made a decision a dropped the loot on two IB315's. I will keep you posted!