# Forum Home Renovation Home Theatres  Subwoofer issue -need for a riser if house is on a slab

## Dean38

Hello all,
We recently built a house on a slab and have noticed the acoustics are alot different  :Frown: , there fore i am trying to make it sound like our previous house which was on stumps basically. 
We loved the vibrations from the sub as it obviously gave more depth to watching a movie...now we find that yes we can hear the sub, but no depth? I wanna bring the grin back when watching an action movie....feeling the 'boom' is the goal. 
So i was thinking about 2 possibilities and i need advise on both. 
1. I build a riser to house the sub and/or subs. ( i would prefer doing this if its more practical )
2. buy more subs and screw them to the back of the lounge set.  
1. If i build the riser, what would good design involve as far as features? ..
Height requirements for good bass and feel?
Hole requirements for the sub to actually work as it should? ( even thru the subframe of the riser if required?)
Is insulation required?
The room is rectangle with the tv on a small wall....9m x 5m
I have 5.1 surround system.
Its a jamo satellite speaker system so i am wondering about speaker placement too....the rears can be in the top corners but the fronts at eye level?  
2. More subs and bolt to the chairs.
This sounds like the easy out option but im not too sure if this will give the same feel under foot?
Our lounge set is 2 single seaters and 1 three seater. Im not fussed about putting holes in it if required. 
If someone could advise on the better option for movie feel it would be muchly appreciated. 
I wish to gather advise and draw up a plan and submit it here again for further development.  :Biggrin:

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## SilentButDeadly

Basically, your sub is in the wrong spot or is now inappropriate for the new room.  In the old house, it was using the floor etc as a sounding board through resonance.   
In the new more stiff and reflective room it doesn't have the punch.   
You can go some way to recifying this by using a corner of the room to load the bass or a similar acoustic positioning tricks.  But putting it on a riser will do very little.   
It would help to know more about the size, shape, window positioning and furnishing of the new room and the equipment you are working with. 
Honestly, if you want quality sound then it does actually pay to pay a professional to do a sweep of your room to help with positioning and specification of the HT setup.  You may not actually need to buy new gear... 
Moondog will be along with more thoughts soon enough...he's a bit better at this than me.

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## Dean38

> Basically, your sub is in the wrong spot or is now inappropriate for the new room. In the old house, it was using the floor etc as a sounding board through resonance.  
> In the new more stiff and reflective room it doesn't have the punch.  
> You can go some way to recifying this by using a corner of the room to load the bass or a similar acoustic positioning tricks. But putting it on a riser will do very little.  
> It would help to know more about the size, shape, window positioning and furnishing of the new room and the equipment you are working with. 
> Honestly, if you want quality sound then it does actually pay to pay a professional to do a sweep of your room to help with positioning and specification of the HT setup. You may not actually need to buy new gear... 
> Moondog will be along with more thoughts soon enough...he's a bit better at this than me.

  I will post the specs when i get home from work but i made an error in the size of the room...its 4160 x 5160........i dont know where i drew the 9 from.  :Blush7: ...hehe 
I have the Jamo a102HCS5 speaker pack ( 6 ohm ) and a JVC RX-F10s 
I know there old now but they work good in my opinion....or they did in a stumped house at least. The speakers are heavy buggers.
I got them for the HT not for music...they are really great for HT but a little crummy for 2 ch music imo. 
The JVC unit heats up a little but will later be put into a wall cavity with circulation, otherwise it does pretty good. 
Any thoughts or opinions are welcome.  :Biggrin:

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## Moondog55

OK I better jump in then.
Buy more subs, you will loose floor bounce if put on a riser ( -3dB ) 
With subwoofers Bigger is better, what sub do you have at the moment? 
Is the new room bigger and if so by how much?   
 My usual answer is use more subs, 3 is good 5 is better. We have 7 (1 * 15 ) plus (2 * 12) and (4 * 10) all running in parallel and I'm not allowed to turn them up.
Corner placement is not always optimal, you may be seated in a null mode and using multiple subs is better at defeating this.  mehlau.net > audio > multisub

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## Dean38

Jamo : Home Cinema Systems : A 102 HCS 6 
Have a look in the manuals for the specs but the sub is 8" reflex bass 38-200 hz
I have another JVC sub with the same specs JVC SP-DW103
Both have the speaker underneath, i liked this feature because my boys put toys in my last speakers and kind of wrecked them lol. These ones faced downwards so they just looked like boxes which kept the toys off the actual speakers. My boys are past that age now, i have had this system for a good 3 years now....the
receiver is about 10 years old tho. its a quick drawing but thats basically it.....we have white walls  
Im thinking of going a med to drk chocholate colour for the tv wall in a suede paint but the rest of the room will later have a timber theme.
Im sourcing a timber slab atm for a chunky coffee table which will house a 10 or 12" bass......i will also be making 2 side tables as well....so they too might house a couple more subbies too now  :Wink 1:  
In the RH wall next to the bookshelf will be the media centre housed in a unit built into the wall with a clear door. Cooling is also involved. 
I was going to run the speaker wires thru the roof and down the walls if required, but i can also run them along the walls or under the carpet. Cutting holes in walls will also make me happy as i can repair that stuff easy. So the more ideas the better.... 
Cheers

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## Moondog55

Simply not enough subwoofer for a room that size, I would say 2 * 12 inch subs with at least 250 Watts each added to your existing system would be closer to the mark. Warning:::: :Redface:  Bass isn't cheap; good bass is expensive. I'm guessing you were exciting room modes in the last house and listening in a "Sweet spot"
Also good bass demands great wife acceptance factor as big boxes are needed.
you need SPLs around 105db at 35 Hertz and preferably lower and an F10 as low as possible ( I am aiming for 25 hertz ) if you can get a box, amp and woofer combination to get louder and deeper you may want to build your own.
I think THX specifies 105db at 30 Hz

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## Dean38

> Simply not enough subwoofer for a room that size, I would say 2 * 12 inch subs with at least 250 Watts each added to your existing system would be closer to the mark. Warning:::: Bass isn't cheap; good bass is expensive. I'm guessing you were exciting room modes in the last house and listening in a "Sweet spot"
> Also good bass demands great wife acceptance factor as big boxes are needed.
> you need SPLs around 105db at 35 Hertz and preferably lower and an F10 as low as possible ( I am aiming for 25 hertz ) if you can get a box, amp and woofer combination to get louder and deeper you may want to build your own.
> I think THX specifies 105db at 30 Hz

  
Our last house was a unit and the lounge was a little small...but yeah the sub must have been in the 'sweet spot' because we had people complaining of 'dry eyes' and grip marks in our furniture. ( we love action movies  :Sneaktongue:  partly due to that reason ) 
My missus will be ok with it hehe... i will have to do some complaining about it, put my hands in my pockets and kick some dirt and make it sound like i don't wanna do it... but she will turn around and say it has to be done ... :Wink 1: .  
I would love to put them into the coffee table actually, could i have 2 subbies pointing down again? or would i need to face them out and which direction?
The bookshelves both have a storage box at the bottom, i can easily convert those as well.  :Biggrin:  They were the kids until i claimed them...i put desks in their rooms instead. 
I'm in the north-north east of victoria just in the outer burbs/country...got any good links/specs so i can purchase the parts to make myself?

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## Cecile

Be careful here.  Moondog will cheerfully help you spend as much money as you possibly can.     :Sneaktongue:  
As he said, the "WAF" is quite important.  I let him get away with one whole wall of audiophile stereo AND home theatre, which is essentially a 4m wall of assorted shapes and sizes of black boxes and a multitude of pre-amps, power amps, CD, DVD, Blu-Ray home theatre amp...and the list goes on. 
There is a 15" Kicker in an enormous box that he built that I want to turn into a side table.  He also built a prototype coffee table with a subbie in it, but it never became a reality.  Moondog's always talking about putting the Kicker either in the ceiling or under the floor. 
We have black fabric on the wall behind the telly, and when we do the renovation will most likely also have that wall very dark.

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## Moondog55

Hi Dean PM on the way

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## Master Splinter

You could always just stick a few subsonic actuators in the couch for that kick-in-the-seat-of-the-pants feeling!

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## Dean38

> You could always just stick a few subsonic actuators in the couch for that kick-in-the-seat-of-the-pants feeling!

  Yeah i was thinking that too  :Biggrin: ... i got a few possibilities atm. 
it looks like i will be puting a 12" into the base of the coffee table, a couple of 10's in the side tables i will be making and another couple of 10's in the lower bookshelf boxes. 
The 2 8's that i have i might fix inside the 3 seater for the  :Shock:  effect.  :Biggrin:  
Im gonna be a busy boy  :Biggrin:   
Would a sub flush mounted into the wall behind the 3 seater be a worthwhile placement?

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## Moondog55

Subs need lots of box volume and in-wall placement can lead to a resonant "organ pipe" effect that sounds simply awful.
While I do think LoranzAudio products are superb I'm not sure I can recommend a woofer that cost $450- each.
There are some cheap 15 inch woofers on evil bait at the moment that would be OK at $99- each if you could put a couple of biggish boxes in the room, otherwise just import from America

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## Dean38

> Subs need lots of box volume and in-wall placement can lead to a resonant "organ pipe" effect that sounds simply awful.
> While I do think LoranzAudio products are superb I'm not sure I can recommend a woofer that cost $450- each.
> There are some cheap 15 inch woofers on evil bait at the moment that would be OK at $99- each if you could put a couple of biggish boxes in the room, otherwise just import from America

  
I will look into that, i would rather make them i reckon....a bit easier on the old wallet. I did some searches and my eyes popped at some of the pricings of the subbies.  
What would happen if i made new boxes and transfered the guts from the 8" and plugged in a 12" or 15"?

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## Moondog55

Subs ( all speakers actually) need to be designed from the ground up.
The driver parameters and your desired target response determine the amplifier power needed, number of drivers and the box design and volume.
The SPL needed is obtained from room size and you calculate the number of drivers or the size of the driver from that volume.
I would say that 2 * 15inch subs would just about do it without problems.
Just remember that SPL is measured in decibels and the scale is logarithmic, 6dB increase is hearable, 105dB is LOUD.
big rooms need big speakers, iron rule of physics
If you are serious about good sound you will need to do some room treatment as well, I'd leave the little subs "as-is" they usually have P***poor amplifiers and lousy electronics.
Amplifiers are cheap enough anyway, even from places like Jaycar although I would probably import a couple of O-Audio units from the states

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## Gaza

Moondog are the jaycar subs still good value for money like they were 10yrs ago or has the market caught up

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## Moondog55

> Moondog are the jaycar subs still good value for money like they were 10yrs ago or has the market caught up

  NO
Current stock is overpriced and poor quality.
Importing from the USA is the best option, even discounting airfreight cost.  12" Subwoofers for Live Sound Reinforcement, Home Audio Subwoofers, Car Audio Subwoofers, 12" Low Frequency Drivers 
Although "Speakerbits" have some decent stock  Peerless subwoofers
I'm a bit out of the loop as I haven't made a sub in a few years

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## MrHankey

If you're looking for maximum value for money, build your own boxes.   www.*billfitzmaurice.com/ * 
I built a pair of Jack 12 boxes from this site (for live) and they sound great. He has a few HT/auto boxes there also. The plans were clear (apart from being spec'd in imperial!) and easy to build. I imported the Eminence drivers from the USA and saved heaps.

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## SirOvlov

I wouldnt recommend putting a sub in the coffee table or a bookcase, the rattling will drive you crazy.  
Its not always the size, it the way you use it! 
Always check the magnets on the sub as well as the travel. Just cause its a 12", dosent mean its any good! I've got 8" drivers that equate to a normal 12" 
Apart from that, what everyone else said

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## Moondog55

> I wouldnt recommend putting a sub in the coffee table or a bookcase, the rattling will drive you crazy.  
>   I've got 8" drivers that equate to a normal 12" 
> Apart from that, what everyone else said

  More info on the 8 inch please, and comparing woofers and subwoofers is like comparing oranges with cheese, they are designed with slightly different jobs to do. 
BUT if you want to move lots of air for higher SPL then you need 4 * 200mm subs to equal 1 * 300mm sub if the X-Max is the same 
BTW if the coffee table sub rattles it isn't built properly. i have built subs i could put a turntable on

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## SirOvlov

8" lfe driver, or sub bass driver, french custom made audax (for a company i worked for). I cant remember specs but double magnet, 90+ sensitivity and around 30mm travel. 
With subs, its not just about spl, its the htz level you want. As i was saying with the coffee table, a sub running 100db at 20htz, i dont see how you could put anything ontop?! (i guess a good vinyl player with 'antishock' and thick felt pads). Its not about the table making noise, its whatever you put on it.

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## Moondog55

If you found the model number for that little Audax driver I'd be interested in modelling it 
A well built sub won't vibrate, no well built speaker will have cabinet vibrations worth measuring
Mind you that sub massed at least 160 kilos and needed a trolley and 4 blokes to move.
30mm of travel in a 200mm driver is moving the same amount of air as 8mm of travel in a 12 inch driver
I think the new THX specs are 115dB/1M at 24 Hz
To meet the new THX specs usually needs multiple 12 or 15 inch drivers with about 2 kilowatts of power depending on room size of course.
I have to ask how small is the room you are measuring 100dB @20Hz in and at what distance and how you are dealing with Eigenmodes

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## Dean38

> BTW if the coffee table sub rattles it isn't built properly. i have built subs i could put a turntable on

  Just for the record, i aquired a good sized slab  of redwood for the box which is about 1.5 inches thick. It should be pretty darn heavy when im finished. 
There will be no rattles as the weight should take care of that  :Biggrin:  i hope... 
I have decided not to go down the bookshelf option now due to too many possibilities of rattles....too many joins etc...........unless the bookshelf is a slab....nah.....hmmmm...yeah nah too heavy...i wouldnt be able to move it from the garage hehe  :Wink 1: . 
I should be able to get out in the garage soon as its heating up again. Fingers crossed.

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## SirOvlov

Cant find specs on audax, i've got them somewhere..... They werent off the shelf but if you look on their site, its s mix between ht and hm series 8". 
Sorry, i didnt mean the cabinet itself but what ever is on top.  
Ever wonder why amazing speaker makes dont have thx approval? Its like having approval for common sense (hmm maybe a good idea then), almost all speakers from those brands fall within the parameters of thx; I just see it as more coin for George Lucas.
I used 20@100 as an example, my two boxes, each with two 8" and a 300w@8ohm amp ran at 4ohm. measured 28htz in an anechoic chamber. They are not set up yet (only been in first house 2months still with no agreement with the wife re lounge set up) but at the old house, slab with brick, they would rattle the glasses in the kitchen. 
Dean, nice one, I would still suggest to use mdf or hdf for the bix, then 'skin it' with the redwood, bass will find the weakest point. Timber has more and less dense parts and so end up with the bass finding the lesser, even though its 1.5", I'd go 12mm mdf at least.  
Are you going ported box or sealed?

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## Dean38

> Dean, nice one, I would still suggest to use mdf or hdf for the bix, then 'skin it' with the redwood, bass will find the weakest point. Timber has more and less dense parts and so end up with the bass finding the lesser, even though its 1.5", I'd go 12mm mdf at least.  
> Are you going ported box or sealed?

  Table Tuba 
Im looking into the long version coz of the slab. It will be 'skinned' in redwood after i build the box.  
The long table tuba looks the goods to me, when i get too it i will post it as i progress and hopefully it turns out how i imagine  :Biggrin:  
The only thing i have to do is stop the kids using it as a garage for their small cars  :Doh:  which has happened before...

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## woodbe

Jeepers, have a look at the Tuba HT Tuba HT   
If you're going to build your own, why not that one?  :Smilie:  
woodbe.

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## Moondog55

THX at least makes all the specifications relevant to each other.
A lot of subwoofers put there are tuned far too high, 100 - 120 Hz for maximum kick drum impact I assume and don't really do bass very well.
bass being those octaves below 80 Hz. 
None of my current subbies have quite enough depth but the huge size of the box needed for my big driver means we need a church hall to make use of it.

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## Dean38

> Jeepers, have a look at the Tuba HT Tuba HT   
> If you're going to build your own, why not that one?  
> woodbe.

  i dont have a corner to put it in and i was looking at the 10" woofer max, so i was gonna stick with the other.... i would love the 15" woofer option if i had the budget and perspex for windows  :Sneaktongue:  
if i do this one right and the missus loves it, she might loosen the purse strings a bit more when it comes time to upgrade the amp and speakers... hehe baby steps if ya know what i mean.

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## SirOvlov

Bass 200htz to 80htz, 80 to 20htz is sub-bass. 
The Tuba's look good, never built one myself, always been more traditional. All the specs and graphs look awesome though, the long version will do the job nicely.

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## Moondog55

Disagree, 80 to 200 is Mid-bass. Sub bass is all the infrasonic stuff we can feel but don't usually here until the SPL goes way up but I can hear 24 Hz just fine at 96dB

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## SirOvlov

Audio Frequency Bands
Just on first page of google search, I say 80-200, they say 100-300 but overall the same as how I roll.

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## Moondog55

Copy and paste from the site linked  *""Band 2*  Here's the midbass, 100 - 300 Hz (there's activity above 300 Hz because even my lab filters aren't perfect).""  
But every audio engineer and speaker builder has a slightly different slant on the matter

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## SirOvlov

Yeah I'll pay that about bass / mid-bass, but I meant the breaks at 80 and 200. So sub is 20-80 and mid is 80-200. I still say anything in the last two octives is sub bass, below 20htz is infrasonic. 
Either way, the outcome should get the result your after dean38 :Redface: )

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## Moondog55

Trouble is that a lot of modern movies really do have lots of information below that audible 24Hz point, so you really do need to be able to reproduce "SUB-BASS" at loud levels if you want to listen to blockbuster movies.
trying to reproduce high SPLs of 14 Hz bass is expensive and I think a few new movies have tones of 8 Hz

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## SirOvlov

Seeing as it has now "heating up", have you got a finished product yet?

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## Dean38

> Seeing as it has now "heating up", have you got a finished product yet?

  yeah well i need a little luck to go my way lol.... 
im fixing some plumbing that went a bit wrong.. when they build the house and it basically came down to the plumbers not using glue on some of the joins and i have ended up with soggy ground under my garage and leading out basically.
I only found it because i was attempting to put in some aggi pipe and noticed that just under the surface, it was wet. As i dug a little more, it became a little wetter etc etc until i got to the storm water pipes...and it was very soggy indeed.
Im having discussions with the builders... 
As this was a bonus project for me, i had to delay it as advised by the boss  :Sneaktongue:  until next month ( maybe ) due to budget concerns...( she has given up work for a little bit to look after our kids as we noticed our boys were becoming 'different', 12 hour days in care/school was a bit much for them. ) 
Family 1st, projects 2nd.... 
I'll be back... :Biggrin:

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## SirOvlov

Bugger to say the least! Good luck with that one... 
Family always first! :Smilie:

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