Subs in the basement

dalaman

Hello people!
I'm new here so be gentle.

Background: I will be having my new HT in a finished basement with 9 foot ceilings. My area will be 18' wide by 38' long. Viewing area will about 18' wide by 14' in depth. The HT will be on the 18' wide wall so that means that all my front speakers will be aimed out toward the wall 38' away. Only things in the way will be some furniture and a pool table.

Question: will my 2 - 100watt, 8 inch subs provide enough oomph for this size room? The floor is concrete with carpet. Will I need to do something special because of the concrete floors? Will it sound as good as a wood floor unit would?
Thanks for any feedback. I won't be moving in until mid-august so I can't test it now.

Dalaman

scottnbnj

this is a pretty good article to keep you busy while waiting for replies:

http://www.ethanwiner.com/acoustics.html

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scottnbnj

just curious, what are you doing for ceiling and walls(ie concrete, steel/wood studs, insulation, wallboard, paneling, etc.)?

scottvamp

That is a huge room man. Two 8's would not even come close to enougth bass for me. Do you have a budget for an upgrade?

Dr. Spec

That is a huge room man. Two 8's would not even come close to enougth bass for me. Do you have a budget for an upgrade?

Ditto - big room. Concrete rules for bass quality but won't give much tactile feel through the floor.

Give the boys at SVS (in your home state BTW) a jingle and bag a PB2+. Think he'll be disappointed, Scott?

dalaman

Originally posted by scottnbnj
just curious, what are you doing for ceiling and walls(ie concrete, steel/wood studs, insulation, wallboard, paneling, etc.)?

My ceiling and walls are finished drywall and insulated.

mantis

I assume then the floor is done as well.What you could have done is raise the floor about 2 to 4 inches so the floor now becomes suspended over the concrete and making is wood.This is what I'm doing with my basement floor only in the theater.All other room will be to the concrete.

This will allow the transfer of sub bass energy to the seating area.It makes a huge difference when you can feel the bass.On concrete slaba I feel some of the impact is lost.

Dan

scottvamp

Do you have a budget for an upgrade?

Dr. Spec

What you could have done is raise the floor about 2 to 4 inches so the floor now becomes suspended over the concrete and making is wood.This is what I'm doing with my basement floor only in the theater.All other room will be to the concrete.

This will allow the transfer of sub bass energy to the seating area.It makes a huge difference when you can feel the bass.On concrete slaba I feel some of the impact is lost.

Yuck.

Anything but concrete muddies up the bass IMO. The "impact" you are losing is really unwanted vibration and resonances from the wooden floor. If you can't feel the bass through the air, then buy more sub.

I know this technique has been recommended in the past Dan, and don't get me wrong, it WILL increase tactile sensations, but at what expense? I'll take an acoustically inert, vibration-free surface anytime over someting deliberately intended to transmit vibes (and its own sound).

Your basement, your call obviously. Just my $0.02.

dalaman

Originally posted by scottvamp
Do you have a budget for an upgrade?

Unfortunely I just purchased the Polk RM7200 package and the downfiring, 8-inch sub comes with it. I have another 8" Energy sub from a previous system. I just want to be able to hear some decent bass while watching DVDs. Music listening is secondary. I guess I'm just not that picky.

Dennis Gardner

You won't know until you set it up and try it. Give the 2 8's a go
and if they aren't enough, sell them for a couple franklins and get a real sub that will fill your room. The 7200 sats will not take much midbass or any deep bass, so the subs will have to work pretty hard to fill your space.

Then again, if you aren't that picky, you may have plenty of bass.

dbournival

I had the same issue a couple of years ago, I put a play room in the basement. The Left and Right Towers have small (6"?) sub builtin. The LFE was somewhat lacking compared to my first system in the family room (however in some movies it was better as it moved between the speakers). I finally added a separate sub. After the addition of the Sub it sounded great but I did not get the vibration that I was used to (I have carpet over concrete also). But when I put my hand on the wall (wow!). Do yourself a favor and set your speaker levels with a SPL meter as you may set the LFE levels to high otherwise.

dalaman

Originally posted by dbournival
I had the same issue a couple of years ago, I put a play room in the basement. The Left and Right Towers have small (6"?) sub builtin. The LFE was somewhat lacking compared to my first system in the family room (however in some movies it was better as it moved between the speakers). I finally added a separate sub. After the addition of the Sub it sounded great but I did not get the vibration that I was used to (I have carpet over concrete also). But when I put my hand on the wall (wow!). Do yourself a favor and set your speaker levels with a SPL meter as you may set the LFE levels to high otherwise.

Well I'm glad to hear that it does work somewhat. I was thinking about putting my 2 subs on a fabricated, "fake" floor by building a small platform ( 4' square, 6" high) for each to sit on. Do you think this has any merit?

scottnbnj

i don't think the carpet over the slab is a problem except, depending on the sub, its feet/spikes and the resiliency of the carpet, it might not be a stable enough. i think most folks will say, if anything, patio blocks or stone slabs under the subs might be a step up.

it sounds like the room is built already. it's not in the process of construction is it? if that's the case, there might be some things you could tweak.

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Dennis Gardner

Any changes that you make using 2 8's in that huge room will not be really noticeable.

Just realize that most people use a couple 10 inch woofers in their car to pressurize the cabin and feel the bass. Doing this in your room with less woofer size and power is next to impossible.

You will have some low bass that should be fine for normal music or quiet scenes, but very little headroom or reserve volume to handle the explosions and wide dynamic ranges that movies today have in their soundtracks.

scottnbnj

Originally posted by Dennis Gardner
Any changes that you make using 2 8's in that huge room will not be really noticeable.

i'll go out on a limb and guess that there would be a noticable difference in a room with poured concrete walls with 3/4" drywall ceiling v. a room with light gauge steel studs with 1/2 sheetrock on one side and no strapping on the other and a drop ceiling.

agreed though, that post construction it's almost certainly more cost effective to go out and buy better gear.

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Dennis Gardner

Room construction techniques can add or remove resonances that will change bass response, but getting bass from 2 8 inch woofers in any 6100 cubic foot room is a tall order regardless of construction.

Adding transducers to seating would be a way of adding bass impact for movies that would be cost effective in this situation.
Aura's Bass Shakers can be had cheap and powered by nearly anything. Not really great for music, but the best $50 bass boost
for movies I've seen.

Dr. Spec

I was thinking about putting my 2 subs on a fabricated, "fake" floor by building a small platform ( 4' square, 6" high) for each to sit on. Do you think this has any merit?

Not unless you plan on sitting on the platform with the subs. The idea is to convey the vibes from the sub, through the floor, and to your seat. Not possible with what you're suggesting.

The butt kickers aren't a bad idea.

dbournival

Dalaman, no I don't. The problem is that you are on a slab. anything you put on in to increase vibration will increase distortion. Just go with a bigger sub like I did.

scottnbnj

Originally posted by Dennis Gardner
Room construction techniques can add or remove resonances that will change bass response, but getting bass from 2 8 inch woofers in any 6100 cubic foot room is a tall order regardless of construction.

~maybe~ a tall order but i'm struggling to understand how the difference in those two rooms could not be noticable.

can someone tell me, how given the dimensions (multiples 9 18 38) and sparse(though reflective) furniture, the difference in the two examples could not be heard?

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Dennis Gardner

Given enough bass capability, I concur with your room improvements. I was referring to bass waves needing to pressurize a given room to be felt. IMO, this just isn't realistic at this room size for the given woofers regardless of room construction. I also agree that adding driver displacement, power, and eq is more cost effective than adding room resonance to existing construction.

Giving room resonances to add bass vibrations will only do that- add bass vibrations at the resonant frequency. This may be good if its controlled to desired frequencies, like the soundboard of a guitar, but if the added resonances are added where a room node exists already, it is just added noise to the room. Concrete sure doesn't add like wallboard. But then again most people I have met want to diminish vibrations in their rooms and throughout their homes not add them.

I simply agree with Ed in that I prefer to work with concrete floors and solid walls and add bass capability as opposed to increasing resonant items in the room. Different strokes I suppose.

scottnbnj

Originally posted by Dennis Gardner
Given enough bass capability, I concur with your room improvements. I was referring to bass waves needing to pressurize a given room to be felt. IMO, this just isn't realistic at this room size for the given woofers regardless of room construction. I also agree that adding driver displacement, power, and eq is more cost effective than adding room resonance to existing construction.

i'm sorry if i wasn't clear. i didn't offer these examples as improvements. i responded to "Any changes that you make using 2 8's in that huge room will not be really noticeable."

for good or bad, there would be a totally noticable difference in the way the two rooms felt, sounded and graphed, even with the small drivers. that's all.

Originally posted by Dennis Gardner
Giving room resonances to add bass vibrations will only do that- add bass vibrations at the resonant frequency. This may be good if its controlled to desired frequencies, like the soundboard of a guitar, but if the added resonances are added where a room node exists already, it is just added noise to the room. Concrete sure doesn't add like wallboard. But then again most people I have met want to diminish vibrations in their rooms and throughout their homes not add them.

we probably agree then that the main problem with the steel stud wall example would be that it would become the largest resonating item in the room and would add its own new sound just like the guitar soundboard. at the very least, if the 8" drivers were placed next to it, the drywall vibrations would be localized.

it could easily get worse if the energy that passed through it (into the small cavity between the steel stud wall and the foundation wall) reflected off the foundation wall and was still strong enough to further exicte the steel stud wall resonance (calculate the volume and modes of the cavity for an idea of what could be going on inside of there).

a backfilled poured concrete foundation wall bearing the weight of a house on top of it doesn't vibrate itself and create its own new sound like the guitar soundboard and the steel stud wall so much as it strongly reflects most energy and frequencies back into the room, which, because of the strength of the reflection, are likely to create different sorts of resonances and distortions.

Originally posted by Dennis Gardner
I simply agree with Ed in that I prefer to work with concrete floors and solid walls and add bass capability as opposed to increasing resonant items in the room. Different strokes I suppose.

we agree then.

the problem is, most finished basement wall construction is closer to the steel stud wall example than the solid wall we agree on.

if you think about it before construction, there are cost effective ways to beef up finished basement light gauge steel stud walls that wouldn't be so likely to suck the life out of subs and add their own sound and resonaces to the room.

if there were ever a sub upgrade in the future, such tweaks would become even more important and noticable.

anyways, that's why i asked if it was pre-construction.

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Dennis Gardner

In agreement with you on pre-construction of an HT room. Any thoughts about how to maximize sound is best tackled in the planning stages.

I still see more concerns on how to stop the bass from running throughout the house than how to build the room to increase it.
Dedicated rooms usually end up being isolating rooms, with channeled walls and lots of insulation. Acoustical treatments are limited to interior additions instead of elemental designs of the construction. Most contractors of homes just aren't up to speed with what it takes to build a neutral sounding room.

I just saw similar thread on another forum with a guy asking how to get great bass for $1000 from a commercial sub in a 40x25x10 room. 10,000 Cubes A tall order, doubt!

DG

scottnbnj

Originally posted by Dennis Gardner
I still see more concerns on how to stop the bass from running throughout the house than how to build the room to increase it.

agreed, transmition does raise the bar higher and add further costs, some modestly though.

to a degree, to contain and control sound in the listening room by definition lowers sound transmition. beyond that, alot of it is pretty straight forward, even if in some cases costly.

for finished basements, there is usually a pretty thick space for insulation in the ceiling. you also want to limit transmition through mechanicals and any openings for them. then control resonances where the ceiling and walls are normally coupled to the first floor. fwiw, building code revisions helped with updated fire stop requirements, these help limit sound transmition.

with pre-construction of the home, as opposed to just finishing an existing basement, you can also get the architect and contractors on board early to keep most of the mechanicals on the unfinished side of the basement and take steps to control the problems caused by runs that must be on the finished side. in this case transmition through the staircase can also be addressed early.

there are reasons that basements often easily allow sound transmition to the first floor and beyond in common construction (more in spite of uncontroled sound transmition, rather than to aid it). so be prepared to create new problems when treating this one.

for contractors, you have to shop for them the same way you shop for your gear.

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Dennis Gardner

I am currently in the middle of a move and wonder how my new basement theater room will compare with the current setup. It is set in an old house with 4 really thick concrete walls in a 12x30 room that I will use about half of the length for my Front PJ setup and the other for a pool table area. Being already finished, I will determine whether I can use my dual Shiva EBS in this room effectively, or if I end up building a larger IB to get deep natural bass extension. Transmission throughout the house is a given when doing anything this large, but the end result for me is simply great impact and smooth frequency response for my bass needs.

scottnbnj

good luck with the project.

i wouldn't just accept that uncontroled transmition is a given, though, what you have will answer alot of the questions about how far you can go without major expense.

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