Looking for a little better low end

[todd.brust 29]

alright here's the deal...i have a set of older scott speaker....i want a little better low end so i was thinking about just doing a sub...more specifically and IB.....i was leaning towards and IB15 from AE speakers...but my question is that in another thread someone mentioned using mulitples of 2 drivers opposing each other...why?

and i kind of wanted a more general idea of what advantages IB has sound wise

[JimJ 11]

and i kind of wanted a more general idea of what advantages IB has sound wise

Better transient response, lower group delay, lower frequency extension...all pretty much things you're looking for for a musical bottom octave

Better have an attic or spare room to load the subs into, though...I wish I did

[Robert_J 0]

Here's one example of an IB using four Soundsplinter RL-p 15's - link. Classic example of an attic manifold using opposing drivers. Opposing drivers cancels out the mechanical force of the cone moving back and forth. IB arrays have been known to flex a ceiling or a wall even at low volumes because of the motion of the cone. Just pick up a good 15" driver and play a 20hz sine wave. You can't hold the driver still. For the most information on home IB subs on the entire planet, go to the Cult of the Infinitely Baffled. Be sure and read all of the FAQ's before posting a question. Thomas runs a very tight forum over there. You will also see that there is not much traffic compared to other boards. 90% of everything you need is covered in the FAQ's.

-Robert

Edited February 19, 2008 by Robert_J

[todd.brust 29]

is it nessessary to have to use an entire room...i thought IB was in a sealed enclosure that exceeded the value of the Vas...so i was thinking like a 16 or 17 cu ft. sealed for the AE...or am i confused...

[///M5 2,833]

10x Vas+ is quite the box...not sure the Vas on that driver.

[Robert_J 0]

Todd, you are a little confused. Like M5 stated, the minimum enclosure size is greater than 10x the combined Vas of the drivers being used. For example, the Fi IB 18" sub has a Vas of 381L. Most people use then in groups of 4 so the total Vas of the IB would be 1524L. So the minimum enclosure size would be 15240L or 538 cubic feet. That's larger than most closets thus the reason that most use an attic or a basement.

Tom Nousaine's article 'The Subwoofer That Shook The World' gives you an idea on what home theater bass nuts go to for the ultimate sub. I'm building 4 custom 18's using Fi soft parts, TC 9 motors and 6 spoke frames. If that isn't enough, I'll get 2 more of the recone kits from Scott and end up with a total of six 18's. One pair over each main speaker. The additional pair would go over the center channel.

-Robert

[todd.brust 29]

damnit...i modeled the IB15 in a 16 cu ft. sealed enclosure on BBP6 and it looked really really good...very flat, no peaks or dips and a very mellow roll off with an -3db point right around 20 hz

it doesn't model much different from having 160 cu ft of airspace at all...a slightly lower f3

could i just do the IB15 in a big sealed enclosure and still benefit from the advantages of an IB install?

[Robert_J 0]

could i just do the IB15 in a big sealed enclosure and still benefit from the advantages of an IB install?

Not exactly. Minimum, you want 4x the combined Vas of all of the drivers. From there, the larger the enclosure, the less impact it will have on the sound. The reason we use an attic is no box equals no sound coloration. It's all about the driver in an IB.

but Robert...seriously? sounds like you will have a bangin' sub set up when you are done! i hope to see a build from you in the near future!

Seriously. If I had the money, I'd go with a Thigpen Rotary Sub. I almost installed four 15's in an IB but decided to go all out. When testing the manifold for rattles, I played some 15hz tones that rattled the theater room door violently and made me dizzy. But the odd part was that I couldn't hear anything from the sub. There are some guys who have usable output at 5hz.

I'm going to start a few build logs for the IB and other stuff I'm working on. I feel left out since I haven't done a car install in ages. And even then, it wasn't enough for a build log.

-Robert

[todd.brust 29]

damnit....i was hoping i could do it that way.....but i understand by what you mean when you say the bigger it is the less coloration....how about a Dipole with this woofer?

[mlstrass 1]

If I had the money, I'd go with a Thigpen Rotary Sub. I almost installed four 15's in an IB but decided to go all out. When testing the manifold for rattles, I played some 15hz tones that rattled the theater room door violently and made me dizzy. But the odd part was that I couldn't hear anything from the sub. There are some guys who have usable output at 5hz.

-Robert

The human ear doesn't hear freq's that low. I personally don't care for super low freq's that beat my house to death, but add NO impact and can't be heard. Just not my thing...

[Robert_J 0]

You can always go with a low Vas sub with a Qts of around .3 and install it in a large box. So that the end result will be an enclosure size at least 4x the driver's Vas and a Qtc around .5 or a little lower. It's not perfect but it should provide great results. Just remember to model it in WinISD Pro or Unibox so that you can determine excursion with the amp you are using. Since most IB users don't use a subsonic filter, we design the system with the expectation that we will play material with frequencies down to at least 10hz. If you are using this for music only then you can change your plans accordingly.

Dipole subs are a completely different type of sub. I think the Linkwitz site has some good dipole information.

-Robert

[mlstrass 1]

I had 4 Tempests in an IB set up and the sound was simply amazing, especially for music. Just blended so well with my mains. For HT it lacked some punch, and also the location I had to put them in was -6dB down compared to the old spot for the 2 ported Tempests.

If you do decide on IB, get at least 2 subs and 4 would be better as you don't get the normal dB gain of a ported box, but if placed properly in the room, not in a null spot like mine, then you'll be quite happy I'm sure.

Otherwise I'd just do a small sealed sub...

[///M5 2,833]

Robert, we'd love to see some build logs from you...your projects sounds sweet!! Thanks for popping in.

Todd, perhaps you should look at other drivers that are better geared for what you have for space. You can make a hell of a ported enclosure in 16cuft.

[todd.brust 29]

lol i could make a hell of an enclosure with that but i want something that is purely for good sound....not loud and the IB15s looked like an awesome sub for only 130 bucks...hard to beat a quality driver like that for the price...

i really want to do a big IB enclosure but everything i though about IBs changed as of today

the thought actually went through my head use my closet! lol

the characteristics of an IB really appeal to me....any other ideas?

i was only planning on spending 130 for that AE and maybe 150 on a plate amp so it's a really tight budget with all my other projects going on at the same time...John has some other drivers there...i guess i just really want an AE sub but not much to work with...

[///M5 2,833]

MJ-18

[Robert_J 0]

The AE IB is proven. Especially, the updated version. But the Fi IB 15 has better specs and a lower price - $129 shipped or 4 for $119 each shipped.

I see you are already a member of the AE Forums. See if a C15 is available. They are much more capable subs.

-Robert

[todd.brust 29]

sounds good...i'll get on the forum and see if john has any available for me when i get tax returns