How about the kids??

[cngbrick]

Hi gang,

I've been hanging around for a while gathering information and components for a manifold type IB sub build, but I am having some doubts on the viability of this project with regards to disturbing my 5 year old's sleep with late evening movie viewing. Before I go making a hole in my hardwood floor I'd like your input on the following points:

1) I see a lot of comments about the back wave being equal to the front in spl. My house has a 4 ft high dry crawlspace with 4 inches of sand on the ground. There is no basement to speak of but the forced air furnace and associated ducting is located there. The access to the crawlspace is through a trap door in the floor. The crawlspace extends the full footprint of the house. Bedrooms are on the second floor, the room over the living room/HT is a guest bedroom (unoccupied most of the time). Will the SPL coming from the IB sub be significantly attenuated by the time the sound wave reaches the second floor bedrooms? If so, is there a rule of thumb to estimate this?

2) Is the sound transmission related to the particular frequency being generated or is it related more to the sub construction/alignment chosen? In other words, can I just switch on a high pass filter at late night to attenuate problematic frequencies or is it the nature of IB alignment to transmit sound throughout the house?

3) Are other alignments (LLT, ported, etc) more suited to my situation? I would rather have the lowest, fastest extension and use filters if this will deal with the situation than be permanently limited by other types of constructions.

To put this in context, my living room serves as the HT with ceiling mounted CRT projector. The room is about 13' wide by 17' but a pantry takes out a corner at the back of about 6' in the width by 3'. There is little extra room for a large sub unless I can disguise it as a decent piece of furniture (right now this is beyond the time/skills I have available).

I am running a Denon 3808CI with Focal 836V/CC800V surrounds. I picked up an QSC RMX2450 along with a BFD 1124P. I was initially planning on a pair of IXL18.2.2's for the IB sub but need to decide if I should revise my plans. I have never had a sub in my system.

Thoughts on this?

Thanks,

Richard

[ThomasW]

If the HT is the living room and the bedrooms are on the second floor, any concern about the output level to the second floor is a function of the front wave not the rearwave.

[cngbrick]

Apr 16, 2009 13:42:36 GMT -7 ThomasW said:

If the HT is the living room and the bedrooms are on the second floor, any concern about the output level to the second floor is a function of the front wave not the rearwave.

So I can assume that I would face the same issues whether I go IB or box sub of some type then?

Is the lower extension typical of IB subs the reason most people remark that the sound travels through the whole house when compared to their box subs?

Thanks for the information.

Richard

[ken]

Hi richard , you should'nt have a problem really re the backwave.....if you wanted to quieten it down more you could build a light frame or something to make a large enclosure under your floor and line it with 12" of insulation...that'd help, though as thomas mentioned it will be the main front wave will be doing much more..........with any sub your house will generally shake and vibrate with any loud stuff...especially something like a powerful ib that can go so low , so you'll have to control your volume to suit your family's needs.....good luck ;D


ken

[ThomasW]

Apr 16, 2009 14:39:47 GMT -7 cngbrick said:

So I can assume that I would face the same issues whether I go IB or box sub of some type then?

Yes

Is the lower extension typical of IB subs the reason most people remark that the sound travels through the whole house when compared to their box subs?

No it's primarily a function of the rearwave propagating throughout the house, but in your case this isn't the situation

[cngbrick]

Excellent guys, thank you for the details!