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Hi guys

I am looking at the krix mx 10 or if I can stretch the budget MAYBE MX 20.  Plan is it will be the front in a 5.1.4 system.  I plan on using the method outlined by krix in their mx installation guide https://www.krix.com.au/wp-content/uploads/2020/06/MX-20_MX-30_MX-40_Installation-Manual-Rev.02_Web.pd.  The method that is isolated/decoupled from the rear wall.  Unfortunately, the room is so narrow at the front (see below for room layout) that I simply cannot do a decoupled wall all the way around as I will lose too much area AND that front section is concrete block wall.  My plan was to use whisper clips (commercial variety...much cheaper and very slightly narrower https://www.tmsoundproofing.com/Commercial-Whisper-Clips.html)  directly to concrete block wall then hat channel (total of 3.8cm total) then 2 layers of fyrecheck 13mm with green glue in between (26mm).  So in total I would lose ~6.5cm on either side leaving me a width of 2.37m for a 2.36m acoustically transparent screen ie https://www.projectorscreens.com.au/16-9-majestic-4k-screens/100-16-9-majestic-fixed-screen-w-evo-ultra-4k-and-fidelio-velvet-frame-as-standard-with-lifetime-warranty-free-shipping.html 

 

I know bulk insulation is recommended behind the fyrecheck and I would do it in all other area of the room but if I attach the whisper clips directly to the block wall I MAY just be able to fit 100"screen.  I realise that this is so close that I would really need to wait until the build was done to see if the screen would actually fit but otherwise would this be reasonable??  I know the room is only as strong as its weakest part from a soundproofing point of view but is having bulk insulation really going to make that much difference in such a small section of the room when all the rest would be ''normally'' insulated?  Alternatively, I could possibly squeeze this in as it is 2.5cm https://pricewiseinsulation.com.au/product/knauf-earthwool-acoustic-insulation-roll/ but it might restrict the clips doing their job and I don't think I could put it directly around the clips??

 

 The reason I would like to squeeze a 100" screen at the front which would give me a) a bigger screen of course and b) probably overkill but the option of the MX20s c) if I go with the mx 10 I can place them a bit further apart maybe improving the width of the soundstage??  Door will be a 40mm solid core door with raven 99si/127si seals at bottom and raven rp 10 for the rest of the frame (or similar). I would build backer boxes for the atmos speakers +- downlights.  Or should I just give up and accept a 92 or 96 inch screen, rule the MX 20 out (budget probably makes that a good thing anyway ;)) and try to do it in a more standard manner?

Thanks for your thoughts/help

Regards

Josh

PS My wife is very sensitive to noise, works shift work and the theatre will be on the bottom level of our 2 level house...our room is upstairs. 

IMG_7927.jpg.4944ab0fe78b49b9fd9b61eab79a9bec.jpg

Edited by jbkinbris
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Talk to the supplier of the clips. I'd have thought not to put anything between the block and the clips - its usually used to stop cavities resonating like a drum.

 

Presumably you're going to clip and channel the whole room?

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hmm not anti krix as i have some older theatre speakers as surrounds) but i would seriously question getting a "wall of sound" vs their MX series with separate subs. (1 front of room behind screen and 1 rear seating)

 

have a read... thought this guy was up with stuff, see the result of blind faith/discounted product.. who knows)

 

 

hhttps://www.youtube.com/watch?v=eIGHVDkenNU

ttps://www.youtube.com/watch?v=z3uBxN5H9Ac

https://www.youtube.com/watch?v=ljCWzAOVQkQ

Edited by hopefullguy
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Thanks hopefullguy... I’m still in the planning stage so haven’t completely decided yet and the SX series along with other options are still in the running. I do, in any case, have a velodyne dd15 that I will add to the mix in any case so if I did have the same problem I have a ready made solution. To be honest the dd15 is going in the theatre regardless as it seems like a waste not to use it and I am not keen on selling it :)

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  • 2 weeks later...

Can you tell us a bit more about the construction of the house around that room? In particular, what is the construction method for the ceiling and floor above?

 

My home theater is on the ground floor of my house, with my kids bedrooms above. I decide to forfeit the isolation clips to maximise my room size, resulting in the biggest possible screen size and ceiling height. Obviously you loose some isolation of the low end, but I was happy with that. The techniques I used resulted in great isolation performace.  The greatest thing not to overlook is making your room air tight.

 

Here is what I did, roughly (probably forgetting a lot of things:

 

1. 2x layers of 13mm soundcheck gyprock + green glue

2. Soundscreen insulation in walls and ceiling

3. Acousitic caulk to seal everything both inside the walls/ceiling and on the outside. (one tiny hole reduces your performance considerably)

4. Door Seals Australia double door seal system, with mechanical drop seals. Added 25mm MDF sheet to back of solid core doors.

5.  Baffle wall has 3x layers of 13mm soundcheck on face + 100mm martini absorb

6. Baffle wall cavity lined with acoustic poly insulation 

7. Capped all ends of joists between the two floors, and framing to exterior walls with cement sheeting to cover flanking paths. Tedious job. Caulked all gaps with acoustic sealant.

8. Lined the bottom of the yellow tounge flooring between the joists of the two floors with 13mm soundcheck and green glue. Caulked all gaps with acoustic sealant. Shown below:

 

IMG_4226.thumb.JPG.cc6c5dae86aea6ebd21115f0fd383378.JPG

 

 

 

 

Edited by DubbyMcDubs
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Posted (edited)

Hi dubby 

that was pretty much my plan except double doors and the fiber cement. Unfortunately with the concrete block wall which is my primary space issue (well it’s all small but that’s the smallest), my understanding is that only adding 2 layers of drywall with green glue in between will do very little as the green glue can’t do it’s work when the board is sandwiched against a concrete wall because you need to be able to dissipate the energy to something. It would add a bit of mass but not damping? This was my understanding from something on AVS (I think Ted white?) said.  
 

with the fiber cement... is this basically in place of clips? How does it help? Isn’t it basically still touching your joists and so you will still get flanking? 
 

with respect to my house... it is a 100+y old qlder. Downstairs was a build in under in the 90s and they put a concrete addition that was the previous owners cellar. I don’t really drink so combining that with the room next to it gives me the above room. Above is living room, kitchen and 2 more bedrooms Flooring is old tongue and groove  6” floorboards above the planned theatre
 

thanks for your input 

regards

josh

Edited by jbkinbris
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Posted (edited)

You'll get better low frequency isolation by direct gluing CFC sheet to concrete block work. Studs or furring channel with clips to create an air cavity can derate the low base region to 15dB worse than a single masonry wall. Is your concrete block core filled? You really need to know what you are trying to achieve. 

 

Creating a double leaf wall only bumps up your mid to higher frequency range.  Eg Rw ratings which relate to the noise reduction of people talking for speech privacy. Or Rw+Ctr for traffic noise reduction. Most issues for HT are base which isn't really covered by Rw or Rw+Ctr.  

 

If you're in a Queenslander you may find treatments are limited generally as sound will travel between rooms through your floor as they are a rather lightweight structure.  Eg I got asked once to fix a massive wall that wasn't performing, was about 0.5m thick. But all sitting on timber floor and joists which transmitted sound straight under the wall. The only solution was to cut out the joists and floor, build new foundations and pour a concrete slab floor for the room. The wall then also needed to be extended above the ceiling to the roof.  They had spent $30k getting to that point before I got called in on builders and bad advice from a well known consultancy. 

 

Edited by DrSK
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Posted (edited)


Hi SK

thanks for your reply.  Concrete block is core filled so shouldn’t create a triple leaf effect.  One thing I haven’t mentioned, however, is getting underneath the house there is a gap of 10cm or so between the concrete block to the underfloor to allow the joists to run under which is only screened by the drywall cornices I am guessing (See below images)
 

  The floor of the planned HT room is also concrete slab although the ceiling of this room is the wooden underfloor of the top level.  Sound isolation across all frequencies is the goal as well as sound quality obviously!03F34AF4-466B-4E39-B38E-8E821BEAC61A.thumb.jpeg.e08ace488477a020a80e6ea76a2dd1f1.jpeg2 rooms that will be combined to form the theatre4BFED1BE-B7D4-4B89-AB83-423100A24162.thumb.jpeg.65031cefd3a03a19590d5b7e1bff4178.jpeg

B51C3ED2-F33E-4611-BE72-1367A23074A7.jpeg

C9922456-5543-4A16-9F49-C39E8A8CDCDD.jpeg

Edited by jbkinbris
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Quote

You'll get better low frequency isolation by direct gluing CFC sheet to concrete block work. Studs or furring channel with clips to create an air cavity can derate the low base region to 15dB worse than a single masonry wa

 

This. Concrete block doesn't get mentioned enough for its acoustic properties. A friend reckons his stereo system has dropped several thousand dollars because he's moved from a concrete blockwall residence to a plasterboard and frame dwelling. He wants his blockwall back!

 

I'd explore green glue directly onto the concrete block.

 

Declaration of conflict of interest: I've 3 spare tubes (unused) and a tube gun to sell, after double layering with Fyrecheck and a soundblock style of batts between the stereo room and the TV room.

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6 minutes ago, ThirdDrawerDown said:

 

This. Concrete block doesn't get mentioned enough for its acoustic properties. A friend reckons his stereo system has dropped several thousand dollars because he's moved from a concrete blockwall residence to a plasterboard and frame dwelling. He wants his blockwall back!

 

 

Nice to hear that, Murray!  :thumb:  35 years ago, I specified concrete block for the walls of the new house we were planning to build - coz I had a feeling their non-smooth surface would be a good thing, acoustically, for the 'listening room'.  (It certainly was a good-sounding room.)

 

Andy

 

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So one thing I really like about the Kroc MX series is that they’re giving you options to match speakers directly to the size of the room you’re fitting out.  There’s no guess work, so putting in an mx20 when mx10 is perfectly suited to the size of your room would be a waste of money.

I know it last tempting to think bigger sub drivers=better, but the performance is almost certainly a function of the position of the drivers, the volume of the space they’re trying to fill and the distance to your seating position.  MX range is designed for reference cinema performance.

I would follow their guide for decoupling the front  false wall.  If you’re already decoupling the entire room, it may be of less benefit. 

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On 02/05/2021 at 3:32 PM, jbkinbris said:


Hi SK

thanks for your reply.  Concrete block is core filled so shouldn’t create a triple leaf effect.  One thing I haven’t mentioned, however, is getting underneath the house there is a gap of 10cm or so between the concrete block to the underfloor to allow the joists to run under which is only screened by the drywall cornices I am guessing (See below images)
 

  The floor of the planned HT room is also concrete slab although the ceiling of this room is the wooden underfloor of the top level.  Sound isolation across all frequencies is the goal as well as sound quality obviously!03F34AF4-466B-4E39-B38E-8E821BEAC61A.thumb.jpeg.e08ace488477a020a80e6ea76a2dd1f1.jpeg2 rooms that will be combined to form the theatre4BFED1BE-B7D4-4B89-AB83-423100A24162.thumb.jpeg.65031cefd3a03a19590d5b7e1bff4178.jpeg

B51C3ED2-F33E-4611-BE72-1367A23074A7.jpeg

C9922456-5543-4A16-9F49-C39E8A8CDCDD.jpeg

Hey, sorry I missed your reply. Best to reply to someones post rather than just adding a post so notifications work. 

 

It seems the cornices are visible from the underfloor in the 3rd and 4th photos? If so this gap with only cornice will make your concrete block wall redundant and the room will leak noise badly.

 

And your ceiling likely is a weak point too if only gyprock. 

 

Personally I'd pull the ceiling and cornice out. Run 4 layers of 25mm CFC sheet instead sitting on the blocks, then seal to the concrete block with mastic. Need to think about a beam maybe in there to support the CFC somehow. Then put your cornice back up. Ratings would at least do the block wall some justice. Don't structurally connect the ceiling to any of the house underfloor. 

Edited by DrSK
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1 hour ago, DrSK said:

Hey, sorry I missed your reply. Best to reply to someones post rather than just adding a post so notifications work. 

 

It seems the cornices are visible from the underfloor in the 3rd and 4th photos? If so this gap with only cornice will make your concrete block wall redundant and the room will leak noise badly.

 

And your ceiling likely is a weak point too if only gyprock. 

 

Personally I'd pull the ceiling and cornice out. Run 4 layers of 25mm CFC sheet instead sitting on the blocks, then seal to the concrete block with mastic. Need to think about a beam maybe in there to support the CFC somehow. Then put your cornice back up. Ratings would at least do the block wall some justice. Don't structurally connect the ceiling to any of the house underfloor. 

Thanks again

Plan is certainly to pull the cornice and ceiling out and have the ceiling isolated from the underfloor. My plan had been to drop the ceiling below the level of the cornices. 
when you say a beam do you mean a cross beam running at the top of the CFC

 

what do you mean by ratings would at least do the block wall some justice. Any specific reason for 4layers of CFC or the point is just adding as much mass as possible? Presumably choosing CFC over drywall as it is about double the mass for a given thickness?

 

the plan would be screen at the block wall end with an isolated wall as per the isolated from rear wall design on page 6 of the krix installation instructions https://www.krix.com.au/wp-content/uploads/2020/06/MX-20_MX-30_MX-40_Installation-Manual-Rev.02_Web.pdf.  Krix is not decided on for sure but regardless of speaker choice plan is to build a false wall

thanks heaps

j

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2 hours ago, jbkinbris said:

Thanks again

Plan is certainly to pull the cornice and ceiling out and have the ceiling isolated from the underfloor. My plan had been to drop the ceiling below the level of the cornices. 
when you say a beam do you mean a cross beam running at the top of the CFC

I'm just meaning I'm not a structural engineer and 4 layers is heavy. 

 

Quote

 

what do you mean by ratings would at least do the block wall some justice.

 

100mm of CFC is at least getting closer to core filled block work in terms of stopping noise breaking out to the rest of the home above. The current ceiling/cornice would derate the room so much that the concrete blocks would be pointless. 

 

Quote

 

Any specific reason for 4layers of CFC or the point is just adding as much mass as possible? Presumably choosing CFC over drywall as it is about double the mass for a given thickness?

Exactly. Easier than pouring a concrete slab. 

 

 

Quote

 

the plan would be screen at the block wall end with an isolated wall as per the isolated from rear wall design on page 6 of the krix installation instructions https://www.krix.com.au/wp-content/uploads/2020/06/MX-20_MX-30_MX-40_Installation-Manual-Rev.02_Web.pdf.  Krix is not decided on for sure but regardless of speaker choice plan is to build a false wall

thanks heaps

j

A false wall creates a double leaf which can significantly derate a wall at low frequency if its not done right. Can you tell me the dimensions of the gap, stud depth etc for both walls and what sheeting and I'll check if it is an issue? 

 

Done right it may also help reduce base in the room as the sheeting can provide some panel absorption. The concrete blocks are very reflective.

 

What is the usage of the room in the last photo? And construction of the wall with the door? How does it relate to the rest of the home? Is the door solid core? You'll probably at least want door seals. 

Edited by DrSK
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On 02/05/2021 at 1:36 PM, DrSK said:

You'll get better low frequency isolation by direct gluing CFC sheet to concrete block work. Studs or furring channel with clips to create an air cavity can derate the low base region to 15dB worse than a single masonry wall. Is your concrete block core filled? You really need to know what you are trying to achieve. 

agreed

On 02/05/2021 at 3:32 PM, jbkinbris said:

Concrete block is core filled

so transmission through that wall shouldn't be an issue...but I accept flanking paths could be...

 

On 02/05/2021 at 1:36 PM, DrSK said:

Studs or furring channel with clips to create an air cavity can derate the low base region to 15dB worse than a single masonry wall.

Sure, but compliance in the walls by using channel/clips/insulation/gyprock can significantly improve the low bass absorption in the room...

...and ideally we want good sound (including bass) in the room, and also good isolation - and great "in room bass" and "great isolation" work against each other when the bass is kept in the room bouncing around taking ages to decay :(

 

On 02/05/2021 at 6:46 PM, ThirdDrawerDown said:

This. Concrete block doesn't get mentioned enough for its acoustic properties

Because concrete block - especially concrete filled concrete block - is essentially a rigid boundary from an acoustic perspective.

It's great for isolation (sound doesn't go through it), but terrible for "in room sound", as everything is reflected back into the room and has to be dealt with.

 

On 02/05/2021 at 6:46 PM, ThirdDrawerDown said:

I'd explore green glue directly onto the concrete block.

Why?

Gyprock with Greenglue directly on to block would have minimal compliance and offer minimal benefit to the "in room" bass absorption, and the block is providing all the "isolation"


@jbkinbris, the posts by @DrSK are entirely accurate from an isolation/sound proofing perspective...

but as @DrSK says

1 hour ago, DrSK said:

Done right it may also help reduce bass (my edit) in the room as the sheeting can provide some panel absorption. The concrete blocks are very reflective.

^this - concrete blocks are the worst for achieving great "in room" sound, particularly great "in room" bass.

 

Ignoring isolation/sound proofing for a bit and only focussing on the "in room" sound - the more rigid the walls are, the harder it is to achieve good " in room" sound.

Treble is easy to absorb (actually too easy).

Managing bass in rigid rooms is hard - absorption gets too large/deep for any bass issues < 150Hz or so, and specialist "pressure" traps are massive and narrow band.

 

As I said above, good isolation typically works against good "in room" sound - especially if the isolation is provided by "rigid" boundaries.

 

Isolation and good "in room" sound can be achieved, but it's expensive :(

Here's a good place to start

https://www.soundproofingcompany.com/soundproofing-101

 

cheers

Mike

 

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4 hours ago, almikel said:

agreed

so transmission through that wall shouldn't be an issue...but I accept flanking paths could be...

 

Sure, but compliance in the walls by using channel/clips/insulation/gyprock can significantly improve the low bass absorption in the room...

...and ideally we want good sound (including bass) in the room, and also good isolation - and great "in room bass" and "great isolation" work against each other when the bass is kept in the room bouncing around taking ages to decay :(

 

Because concrete block - especially concrete filled concrete block - is essentially a rigid boundary from an acoustic perspective.

It's great for isolation (sound doesn't go through it), but terrible for "in room sound", as everything is reflected back into the room and has to be dealt with.

 

Why?

Gyprock with Greenglue directly on to block would have minimal compliance and offer minimal benefit to the "in room" bass absorption, and the block is providing all the "isolation"


@jbkinbris, the posts by @DrSK are entirely accurate from an isolation/sound proofing perspective...

but as @DrSK says

^this - concrete blocks are the worst for achieving great "in room" sound, particularly great "in room" bass.

 

Ignoring isolation/sound proofing for a bit and only focussing on the "in room" sound - the more rigid the walls are, the harder it is to achieve good " in room" sound.

Treble is easy to absorb (actually too easy).

Managing bass in rigid rooms is hard - absorption gets too large/deep for any bass issues < 150Hz or so, and specialist "pressure" traps are massive and narrow band.

 

As I said above, good isolation typically works against good "in room" sound - especially if the isolation is provided by "rigid" boundaries.

 

Isolation and good "in room" sound can be achieved, but it's expensive :(

Here's a good place to start

https://www.soundproofingcompany.com/soundproofing-101

 

cheers

Mike

 

 

Building a room within a room as suggested in this link can destroy low frequency break out performance unless the air gap is correctly tuned for the mass of both the inner and outer walls.

 

As per my other post if tuned then you can control both break out and make use of panel absorption to manage in room low frequency absorption. 

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4 hours ago, DrSK said:

 

Building a room within a room as suggested in this link can destroy low frequency break out performance unless the air gap is correctly tuned for the mass of both the inner and outer walls.

 

Isn't a s-tonne of weight going to do that anyway? The accepted standard by most builders over the past 20 odd years is to follow Ted White's advice - isolation, mass, damping. Then deal with the bass in room. Yates, Erskine et al all do this 

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On 14/05/2021 at 11:31 AM, Peter the Greek said:

 

Isn't a s-tonne of weight going to do that anyway?

Nope, not at all. That is exactly how you stop low frequency noise breaking out. 

 

Quote

 

The accepted standard by most builders over the past 20 odd years is to follow Ted White's advice - isolation, mass, damping. Then deal with the bass in room. Yates, Erskine et al all do this 

 

Not familiar with them. Gave up reading the HT and home hifi worlds advice years ago as there is a lot of uneducated witch craft out there and pseudo science when it comes to acoustics from people that don't have the skills, but think they do, and wouldn't cut it beyond getting away with home installs where things don't matter much and where there aren't any regulators requiring design to targets and compliance with legal enforcement actions when things are sub standard. Some of the YouTube channels are cringe worthy in their explanations and advice but big following from people that don't know any better. I'm not saying these are the names listed above are part of that, I just gave up reading from the many practitioners as I found so much was plain wrong, witchcraft, marketing propaganda, etc etc. Best to stick with actual references on acoustics from the actual respected and peer reviewed masters in the engineering discipline. 

 

On the room in a room thing, people seem to continually not understand that even a 'room in a room' is not isolated. Not unless the inner room is surrounded by vacuum. It is simply a double wall system in 3-d connected by a spring called air.

 

Get the mass of the inner and outer walls and air gap between the 'rooms' wrong and you have an expensive build that performs a lot worse than could be achieved with proper knowledge.  And in a number of instances I've measured, the critical low frequency breakout, which is often what you actually really need to control, is worse than if they hadn't built a double wall or room in a room due to resonant coupling between the two 'rooms' and the air gap.

 

Done right, double walls and rooms in rooms can work well. That is why I asked the OP for further info as it'd take me 15 minutes to model it up, check it and get back to them.

 

And in many instances double walls or rooms in rooms still just rely on the combined mass and act as a single wall anyway at low frequency. Just depends on the design constraints and how you need to tune the inevitable resonant coupling between the two 'rooms' or walls. Ie depends on the impedance at the frequency of interest.

 

People also often get swayed by big Rw or STC numbers which are irrelevant for music and HT. These numbers simply give the noise reduction for speech/vocals which is never an issue for breakout for music or HT. Many designs with low Rw are actually better for music and HT breakout. Some people then try and use Rw+Ctr for lower frequency, again this doesn't help much more as this is the noise reduction for traffic noise which is mostly from tyres and still centred at higher frequencies than the issues for music breakout and HT. 

 

However at this point all I can see is a massive weakness of ceiling and cornice directly under a lightweight timber floor of their home and openings under the house presumably to the neighbours. And to a certain extent they already partially have a room in a room as it is built into the ground under the home's subfloor.  Personally I'd be controlling the breakout through the ceiling/cornice, then making use of a properly tuned internal wall in the room etc to provide some LF absorption and isolation (IF the door pictured doesn't negate any benefit etc) , but I don't know what is through the pictured door and how this relates to anything else. 

 

I'm happy to give a few pointers but at the moment it's not worth my time working in this field for under $10k for a basic room. And anytime I get asked to do work for home owners I usually regret it. People seem happy to pay plumbers $100s of dollars an hour but not university qualified engineers with $100k or more of gear (my microphone that is needed to properly test a wall and find issues costs $14k) that can solve mathematically complex problems, most of which needs to be done back at the office. So the vast majority of skilled practitioners stick to commercial and government clients. We've got highly qualified people in Australia, one of whom helps me out that has also worked with Toole on internal acoustics and has gone beyond what he knows, that won't go near the home market. 

 

Edited by DrSK
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And there is it.....consultants on forums.....we see this all the time. AVS must have burned 50 or so since its inception (thank god). They come in, waive their hands in the air, quote all sorts of complex math etc etc and say you can't do that, it wont work etc etc. The the stark reality of the situation is this, there are 1,000's of DIY builds who have used either double stud walls or clip and channel and achieved truly outstanding soundproofing. Its really not that hard, there is just so much practical, applied evidence that this stuff works. Time and time again. Its the standard consultant model, lay some seeds of doubt in some guys mind, scare the crap out of him, and then put the hand out for a pile of cash to fix the problem they've created in the guys mind. Either come here to truly help, or at least be up front about it "hey, I do this for a living, I can help you, probably cost you X, but I can make sure you get this right".

 

It is a global market. Look at the packages that QuestAI's packages for example....way, way less than $10k. Don't whinge about home owners not paying for it, either meet the market or make the proposition truly worthwhile. Really, if you think Keith Yates or Dennis Erskine are bums, I suggest you do some asking around.

 

 

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