Why IB Sub? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 73 Old 07-01-06, 09:52 AM Thread Starter
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Why IB Sub?

This question is to help me, and others, understand the benefits of an IB sub.
Looking at the posts and links the only benefit I see is to remove the need of having a sub taking floor space in your HT room, freeing up more floor space.

Could you experts help the rest of us understand more - is this the only benefit?
Also any downside with an IB?
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post #2 of 73 Old 07-01-06, 10:12 AM
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Re: Why IB Sub?

I don't know much about them, but one disadvantage that I could see would be sound levels in the rest of the house (if you're using an attic IB). With a conventional sub, the sound is contained in the theatre. With an IB, the sound would be available to the ceiling of every room, unless it was in a contained attic section.

Advantages would be low frequency extension since the cabinet size is huge. We hear of responses easily extending to 5Hz. The distortion would then be quite low.

I would think that the entire project is fairly cheap compared to retail subs.

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post #3 of 73 Old 07-01-06, 11:34 AM
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Re: Why IB Sub?

Cheap? Well it can be I suppose... not everyone is as insane as me. Mine will run $2500 once it's all said and done. That's about what my two SVS subs cost. It might be a little less depending on if I end up needing a x-over and/or two amps.

I never had a problem with my Velodyne HGS-15 traveling throughout the house and Angibug complaining... but with my two SVS subs... if she's at home she's gonna have something to say when I take a pee-pee break or get done with the movie. I know what she means too... when Chelsea and her friends are out there and we're inside, it's unbelievable. It sounds like some serious thunder. I could hear faint thunder in the distance with my HGS-15, but again not a problem. With the two SVS subs... it's like right on top of the house... loud. Every now and then something will shake or rattle. Angibug made the statement one time that the house was gonna fall apart one day because of that room. Maybe so with the IB's.

Darren stated his IB is not really any worse than his regular sub, but he has a lot of insulation in his attic too. ThomasW has recommended I put insulation in mine.

Anyway... I'm getting somewhat off topic.

My reasoning for trying IB is to get the supposedly ultra clean low response down to 10hz or so, but I've heard on more than one occasion that IB doesn't always have the same impact as some traditional subs. But then I've heard it can if you do it right and have the right conditions.

You ask for experts, why did I even chime in?

I think Chrisbee has a way with words that describes IB like no other. I'm sure he'll chime in and share it with us.

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post #4 of 73 Old 07-01-06, 01:07 PM Thread Starter
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Re: Why IB Sub?

Thanks guys, I'd like to see this post run out so more replies the better.
Then hopefully the tweakers amongst us can weigh up the options of doing it or not.
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post #5 of 73 Old 07-01-06, 01:10 PM
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Re: Why IB Sub?

I'm not an expert but I can give you some info. I have a 4 way 15" IB.

1. Very few have reported any more noise in the surrounding rooms or outside the house than when they had a traditional box sub. Me included, no extra noise anywhere.

2. The sub is hidden and takes up zero space in the room.

3. Mine plays flat to 10Hz, has more output than my box could muster (AV15 PR'd), actually has more tactile feel than any sub I've ever heard/experienced. My entire house shakes between 10Hz and 20Hz sweeps. I also get the chest pounding sensation when appropriate.

4. The only down side I can think of is the absolute need to EQ the sub. With the EQ you can make it behave any way you want.

5. More drivers, more efficiency = fewer watts.

6. The cool factor is very high. Especially when nobody can figure out where the bass is coming from.

7. With multiple drivers playing in an IB you get much less distortion, the bass isn't colored, it integrates with my mains quite well.

8. Placing the IB between the mains is much easier than placing a bulky box sub between your mains unless you have a dedicated space for listening.

9. HUGE WAF if you can get past the hole cutting

With EQ my sub hits 10Hz without loss of output, I can't measure down to 5Hz so I can only assume that it has pretty decent output there but probably drops of a little. I'll be spending up to $1,500 for a 4 way IB once I have my final drivers. I could have one that is quite adequate for a 3,200 cubic foot room for about $700 but I want high excursion, not moderate so I'll probably be going the more expensive route.

For more info you must check this IB FAQ out: http://home.comcast.net/~infinitelybaffled/

Last edited by Darren; 07-01-06 at 01:20 PM.
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post #6 of 73 Old 07-02-06, 12:25 AM
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Re: Why IB Sub?

I also have a 4 15" IB and the performance is incredible.

Flat to 10 Hz and very clean sound. In fact I thought I built it for HT but I am finding myself listening to 2 ch more since it has been up and running. The sound is different then a traditional box, and it takes some getting used to, but once you do there is no going back. The IB is subtle but forcefull. It will hit very hard when it needs to but is not boomy at all. At first it almost sounds wrong, but then you start to realize that is how stuff was meant to sound. Really really cool.
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post #7 of 73 Old 07-02-06, 09:02 AM
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Re: Why IB Sub?

Just an observation that occurs to me when I see a reference to IB "vs" sealed: An IB is a sealed sub (albeit one without an obvious "box"), in that it relies solely on the drivers for output and the back wave is isolated from the front. It has a large efficiency advantage (and less thermal compression) down low from the very large Vb, a typically very low Qtc, and no acoustic high-pass filter in the form of a stiff airspring behind the drivers. Also, since box size is not a restriction, IB-ers usually find it much more easy to incorporate large amounts of displacement, four 15's is fairly common. This has nice gains in dynamics and distortion as you might expect. I think this huge Vd is a large part of the epiphany many experience when they first fire up their IBs...a single 12 to four 15's is a bit of a jump.

The obvious disadvantage to me is the probable lack of placement freedom.
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post #8 of 73 Old 07-04-06, 04:00 AM
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Re: Why IB Sub?

Jack Gilvey wrote:

The obvious disadvantage to me is the probable lack of placement freedom.
Tell me about it! I'm not even allowed to put a manifold in the roof that I put on myself. (working alone)

She doesn't mind giant round holes in the walls but she won't have square holes in the boarded ceiling. In case it rains in?!? ?!?

I have plans for manifolds in the roof access hatches I put in at the same time I built the dormers.

A shame they have 16" of rockwool resting on top of them!

I may have to go in from above!

Oh, you meant acoustically?
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post #9 of 73 Old 07-29-06, 01:55 PM
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Re: Why IB Sub?

I have a dual Avalanche 18" IB, and am quite happy with it. The sound is clean and sharp, but also forcefull when needed. I dont' have an EQ yet, so my frequency response is not ideal. I think I'll be much happier after I finish my passive acoustic treaments and get the BFD. My room is about 3000 cubic feet, but it has a door sized opening to the rest of the house (>10,000 cubic feet). My response slowly drops off below 30 Hz (indicating little if any room gain) so I think I'll end up installing a solid core door with weather stripping... partly to re-enforce the bass and partly to keep the sound down in the rest of the house. The opening happens to the rest of the house happens to be in the front left corner, so a lot of bass is escaping. I also have 57 square feet of windows in the room . The other problem I have is I'm already pushing my amp to its limit (350 watts per driver). I have a feeling I don't have enough power in reserve to boost the lower frequencies once I get the BFD. In summary, the IB gives a very natural sound, and is very pleasant even without EQ. As indicated above, my setup is no where near complete... and I'm sure it'll be very nice once done.

Last edited by jagman; 07-29-06 at 02:02 PM.
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post #10 of 73 Old 07-29-06, 02:02 PM
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Re: Why IB Sub?

jagman wrote:
The other problem I have is I'm pushing my amp to its limit. I have a feeling I don't have enough power in reserve to boost the lower frequencies once I get the BFD.
I'm sure I remember Thomas saying that the VLFs are very easy to drive.

That said, power really makes an IB come alive, at least in my own experience.
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