43 replies to this topic

[3G_]

I am on the move and my new home has a rear separate room with dimensions of 6.5m x 4m.
This is obviously too small for my "ultimate listening room" so I will be extending the room outwards.
As i am now a student i really want to put my money into the build and not professional fees so I am hoping it can be a collaborative build.

Feel free to give design ideas..

The system is as follows
Big 3 way horns similar in size to Avantgarde trios.
Vinyl front end and active amplified Pass labs amps running thru a DSP 2x8 processor for crossover and delay.

I need to add bass from 20Hz to 100Hz and this will be integrated into either subfloor horns or in ceiling horns. I will post some links to ideas for the horns.

The room will have a garden setting and creek visible so there will need to be some big windows, this is the only negative in the design but I am thinking of some large rigid panels which could slide over during listening sessions, especially if the windows are strategically placed.

I will keep the 6.5m dimension which runs along the original rear wall, and extend approx 6 metres to make the room 6.5 x 10 metres. Ceiling height can be upto 3100mm without going above the original roof line.

For bass traps i am thinning of bulkheads around the perimeter of the ceiling and maybe one down the centre lengthways and 2 at 1/3 & 2/3rd of the 10 metres span.


more to come…..

[Peter the Greek]

i really want to put my money into the build and not professional fees

You get what you pay for.......you might want to consider this service as an affordable and highly recommended option.

Everyone here will have an opinion on how to approach this, I suggest getting yourself a copy of Toole's book, Sound Reproduction. if you go with the above for $600 you'll get an acoustic treatment plan and layout from one of the world's foremost acousticians and room designers....money well spent IMO

[3G_]

Thankyou Elill , that looks like a great option.

For me half the fun is the designing and building process, but I am more than happy to pay up to a few thousand for professional service, just not tens of thousands on a project which never gets of the ground like i did last year.

I still like members of this forum to give ideas and tips which they have learnt along the way.

[Peter the Greek]

Its very, very reasonable for what you get.....local guys start at like $2500+++ which i think is a bit rich.

Going to soundproof it? have a read of the articles section on www.soundproofingcompany.com

Bulkheads are good for other thing too - like bringing in HVAC in a quiet manner

[3G_]

As the room is oly going to have one wall touching the house soundproofing isn't a huge issue. Where it does touch is only a study area, not a living or bedroom. I investigated resilmount before but can not see a real benefit on the 3 new freestanding walls.

I will probably build a simple brick veneer construction with 2 layers of fire proof board using green glue between the two.

[Paul Spencer]

You're planning a 20 Hz bass horn and don't think you'll have sound isolation problems?! Hmm ....

Firstly I would plan for both corner vertical and bulkhead traps if you can get to all the corners, the bulkheads being the bonus traps rather than the ones you rely on. They will almost certainly be too small to go down low enough on their own.

Bass horn, fun fun! I'd be inclined to do two rather than one. Divide it up and a few things become easier. Power them with a pro amp with passive attenuators, the one channel drives each sub. So you might have a tapped horn that runs 20 - 40 Hz. You can more easily get away with a small mouth and put it under the floor. The one I built recently uses two 12" drivers, 740w of power and it's a 20 Hz horn that is 400 x 600 x 2250. It equals a pair of Maelstrom 18" drivers with 4kw above 20 Hz. Starting from scratch I'd probably go with a pair of 15" or 18" drivers in a similar but upsized design.

Then above 40 - 50 Hz you go with a front loaded horn which will have less compromise.

Bass horns in the ceiling ... difficult!

Bass horns in the floor ... much easier. In any built-in design, ensure drivers are dual opposed to kill vibrations. The problem with horns in the floor is getting the mouth big enough without creating problems with big holes in the floor. Vertical stacks of bass horn modules firing into the corner are another option, and tapped horns don't need a big mouth. A front loaded bass horn that isn't compromised in size has a smooth extended response.

[3G_]

The site slopes away so i can see concrete horns in a slab situation being a good solution.

http://www.diyaudio....-galerie-7.html

Those PD2450 subs sure are big.

[Paul Spencer]

Sounds like an expensive solution - concrete on a sloping site.

[3G_]

Expensive but really the only option for a music room. It only slopes maybe a meter over the 6 meters of the extension. I have a great footing contractor who does work for a cost plus price which I always very reasonable. I really don't like suspended timber floors. So much so that in the property I just sold I used suspended concrete floors with timber battens then 19mm hardwood flooring over the battens.

[Peter the Greek]

I investigated resilmount before but can not see a real benefit on the 3 new freestanding walls.

FYI, resiliant mount and clips/channels are two different things.

The main benefit, other than proper isolation is that the impedance of the walls and ceiling is the same. So you get a more predictable outcome and you also don't suffer the issues of heavy/fixed walls being highly reflective for bass

You should think about doing two layers of board with GG on the floor as well - again this helps (and is really, really nice to walk on - like a gym surface). The other option is using this stuf called Angelstep which Acoustica make (best to use both actually)

[3G_]

Elill, do you mean concrete slab then glue then particleboard flooring, then glue then particle board, then underlay and carpet?
On reflection since its a new room no harm in doing either staggered wall studs or resilmount system.

[Peter the Greek]

Elill, do you mean concrete slab then glue then particleboard flooring, then glue then particle board, then underlay and carpet?

Concrete
Rubber of some description (Angelstep or another)
Particleboard
GG
Particleboard
Underlay
Carpet

Whisperclips and channel are the ducks nuts, I helped a mate recently do a room with them, so darn impressive its not funny

The reason I am so particular about all this is you cant (well not easily/cheaply) change any of it once the room is done. You can change gear and treatments till the cows come home

[3G_]

Did you take any pics?

[Paul Spencer]

Concrete floor + concrete ceiling = big problems! But just a concrete floor is not a great concern.

[rawl99]

FYI, resiliant mount and clips/channels are two different things.

The main benefit, other than proper isolation is that the impedance of the walls and ceiling is the same. So you get a more predictable outcome and you also don't suffer the issues of heavy/fixed walls being highly reflective for bass

You should think about doing two layers of board with GG on the floor as well - again this helps (and is really, really nice to walk on - like a gym surface). The other option is using this stuf called Angelstep which Acoustica make (best to use both actually)

Elill, 3G

Elill. I have read a number of your posts on acoustic treatment and you are obviously knowledgeable in this area. I agree absolutely with virtually everything that you write but this one time I must beg to differ.

Your suggestion of using gg and plaster for the walls/ceiling is excellent advice.
I would strongly suggest to 3G to consider using standard 10mm gyp rather than firecheck or sound check. The fire/sound chek does have a better stc ie they stop more sound exiting the room but my experience is that they create a harder acoustic internally. The standard gyp creates walls and ceiling that are acoustically softer, acting as a better bass-trap but still giving similar reflection characteristics in the mid-high range. The standard gyp gives walls/ceiling that inherently behave as a bass trap.

You will lose stc rating but, 3G, as you have pointed out, the external transmission is less of an issue for you.

Ellil, where I differ is the floor. The suggestion you have made re ply/gg is excellent for stopping sound from coupling into the slab and propagating thru the slab into other areas of the house. It also has benefit in terms of stopping slab resonances coupling back into the room.
Where the issue lies is in terms of sitting speakers on to this floor finish. The ply over angel step (or similar) is not in any way a solid surface so the speakers do not have anything solid to couple to for the purpose of dissipation of cabinet resonances.
The issues I see and have experienced are:
The speakers will tend to rock back and forth ( drivers move, cabinet moves- refer Newton) causing significant coloration of the sound.
The cabinet resonances have nothing massy to couple to for the purpose of vibration 'drainage'.
The speakers will tend to excite vibration in the 'suspended' floor causing acoustic excitation into the room.

The solution I see, and have used, is to use the floor construction methodology you have suggested, BUT, the speakers spike to the slab beneath the isolated floor.
This can be done a number of ways:
Build the very front section of the room where the equipment and speakers stand from concrete with no suspended floor and the rest of the room with suspended floor as you describe,
Build small islands where the speakers will be from concrete level with the finished timber suspended floor ( tricky cause ya gotta know beforehand with reasonable certainty where the optimum position for the speakers is.... And don't change speakers)
Run the spikes from the speakers thru clearance size holes in the suspended floor down to the slab.

Pick your preferred methodology and do it this way and the results are brilliant. I have typically used the first option having a tiled section over concrete at the front, with suspended floor for the rest of the room. Note that this is for improved room acoustics. It is NOT the best way to do it if you want to stop the noise going out the room.

The wonderful part about doing it this way is that the vibration coupled from the speaker spikes into the slab is prevented from exciting the room via slab resonance because of the suspended ply with gg acting to insulate the room from the slab resonance.

Food for thought.

I can only yet again reinforce the in-room acoustic improvement one obtains utilizing Elills suggestion of isolated wall/ceiling construction, either whisper clips or GOOD resilient mounting methodology.

Cheers
Rawl

[rawl99]

Concrete floor + concrete ceiling = big problems! But just a concrete floor is not a great concern.

Paul,
Concrete ceiling is only a problem if you do not have the headroom to drop an isolated plaster ceiling using resilient mounting.

If you have the concrete as the exposed finish of the ceiling then I totally agree.

One guy gave me a square concrete bunker, concrete all surfaces, and told he wanted to make it a dedicated 2 channel and recording room.
That was a fun one!

Rawl

Edited by rawl99, 20 April 2012 - 07:56 PM.

[Peter the Greek]

Hi Rawl, fair points depending on the speakers. I've never really thought about it from that perspective. I'd not be concerned about subs sitting on such a structure....and I have a tendency to baffle/wall mount speakers, which keeps the LCRs in place.

Thinking of many professionally designed rooms I have seen, most still treat the floor in the above manner - possibly due to the type of speakers being used. Actually I can think of several with large 3 way actives that just sit on the ground. Horses for courses I guess.

You could also build a box and fill it with shot or sand and it on the treated floor. The mass of the box would far outweigh that of the speakers converting any kinetic energy into heat - problem solved

[rawl99]

Hi Rawl, fair points depending on the speakers. I've never really thought about it from that perspective. I'd not be concerned about subs sitting on such a structure....and I have a tendency to baffle/wall mount speakers, which keeps the LCRs in place.

Thinking of many professionally designed rooms I have seen, most still treat the floor in the above manner - possibly due to the type of speakers being used. Actually I can think of several with large 3 way actives that just sit on the ground. Horses for courses I guess.

You could also build a box and fill it with shot or sand and it on the treated floor. The mass of the box would far outweigh that of the speakers converting any kinetic energy into heat - problem solved

Elill
Thanks for your response.
Your comment about baffle/wall mounting suggests to me function aimed toward home theatre style use rather than 2 channel music reproduction. In this home theatre type situation isolation is most typically the driving and governing factor so the methodology used would be as you have described, to use the fully coverd floor with in- wall speakers or floorstanders standing on the isolation flooring.

One would think that the mass of the box would solve the problem. Interestingly, in practice, this is most definitely not the case. The box vibrates with the speaker and couples into the floor.
This is the case with a bookshelf or a floor stander.
Vibration control is an extremely fickle thing in audio that defies a lot of apparently logical 'solutions'. More mass is often not the best answer. Unless you have ridiculous amounts, such as several ton of cncrete slab attached to a few billion tons of earth, in which case sinking the vibration to it is most effective. Have an extended chat with somebody that builds really good loudspeakers/ turntables isolation racking, and this will be reinforced.
Note that there are a lot of pretty ordinarily designed bits of gear in this list which are aimed at commercial profit rather than excellence in design, so be selective with your references.

Please bear in mind the level of back and forth box movement we are talking about.. Really really really small movement is extremely sonically significant. Look at the box movement/ vibration compared with the excursion of a tweeter 20, 40, or 60dB down from average spl from the speaker and you will see what I mean.

Cheers

[Paul Spencer]

Paul,
Concrete ceiling is only a problem if you do not have the headroom to drop an isolated plaster ceiling using resilient mounting.

If you have the concrete as the exposed finish of the ceiling then I totally agree.

One guy gave me a square concrete bunker, concrete all surfaces, and told he wanted to make it a dedicated 2 channel and recording room.
That was a fun one!

Rawl

In that case you have less of a problem, and hopefully there is also insulation in the cavity. The plasterboard will act as a membrane pressure trap and the insulation acts to increase the bandwidth of absorption. So you have gone from a big problem to a smaller one. Room gain is expected to be higher due to the concrete and with the concrete the need or absorption is greater than usual. Whatmough have a showroom with split face masonry and a concrete floor. The result was cave-like bass, which led to them then adding four large corner bass traps which they now sell. Their 10" 200w sub hits with a LOT more punch than you would expect in a normal room of that size. My sub in that room might cause heart attacks!

[Peter the Greek]

One would think that the mass of the box would solve the problem. Interestingly, in practice, this is most definitely not the case. The box vibrates with the speaker and couples into the floor.

It does - do you know what a say 4m x 1m x 200mm box full of sand weighs? The box wont vibrate because it has a significant amount more mass than the speaker - as I said, it converts kinetic energy to heat. This is pretty basic physics.

Edited by Elill, 21 April 2012 - 12:26 PM.

[rawl99]

It does - do you know what a say 4m x 1m x 200mm box full of sand weighs? The box wont vibrate because it has a significant amount more mass than the speaker - as I said, it converts kinetic energy to heat. This is pretty basic physics.

A box of sand that large will create a significant degree of damping. What are you making the top,lid ofmthe box out of and how do you ensure that the 'lid' of the box stays 100% coupled to the sand? ( which has an interesting habit of settling with time)
Something that large is more than a little inconvenient to locate within a room. The most significant problem with a box as large as you suggest is that it will raise the speakers an extra 200 mm above the floor thereby stuffing up the manufacturers design for first floor reflection point. With a stand mount you can shorten the stand to compensate. With a floor stander not a chance. Bass and midbass will be heavily compromised by doing what you suggest.

So, back to square 1.

Rawl

[3G_]

Could you simply once settling on speaker position drill a 30mm or so hole trhu the layered floor to allow speaker spikes to contact the concrete sub floor. Some plugs could easily hide the holes if ever needed.

[Paul Spencer]

Why would you do that?

[rawl99]

Could you simply once settling on speaker position drill a 30mm or so hole trhu the layered floor to allow speaker spikes to contact the concrete sub floor. Some plugs could easily hide the holes if ever needed.

3G

Absolutely one could do that. It does not need to be that big. Merely enough to give clearance for the spike thru the 'suspended' timber section of the floor. Do remember that the spikes will need to be normal length plus the thickness of the 'suspended' timber floor so it would be good to have fairly thick body thread on the spikes to make them as solid as possible.

In terms of Paul's comment about " why would you do that', I think I have answered that pretty comprehensively in earlier posts.

With the box of sand concept the top of the sand- filled box becomes an extension of the loudspeaker enclosure via mechanical coupling and is therefore subject to all of the usual concerns surrounding resonances in speaker cabinet design. Keeping the top coupled to the sand is rather difficult unless the box is 'pressurised' with sand. The top will still have a pretty decent amount of resonance. I have played quite extensively with this principle on isolation platforms and what seems logical or obvious in theory does not always translate so simply into practice.

Have fun designing your room. Feel free to pm as I am happy to offer any thoughts you may wish to seek.

Rawl

Edited by rawl99, 22 April 2012 - 01:33 AM.

[LogicprObe]

Going back to the extension, I'd make the new park half hexagonal design and the three end pieces all glass (very thick, at least 12mm laminate) so you can see the creek or even make them folding doors so you can open the area up.
Then heavy curtains can pulled across in front of them if they are too reflective.

[3G_]

Why would you do that?

to directly couple the speaker to the concrete slab

[PixelPlay]

I like the idea, problem is we all move our speakers about from time to time depending on new additions or modifications.
I have wood floors and they are a pain in the a........

[LogicprObe]

I like the idea, problem is we all move our speakers about from time to time depending on new additions or modifications.
I have wood floors and they are a pain in the a........

When I built mine, I made them doubly think.
Put down a layer of chipboard flooring and then laid floorboards on top of that..
Sandwiched in between is a waterbased glue that remains flexible, like silicon but easier to work with and clean up.

[Paul Spencer]

to directly couple the speaker to the concrete slab

... and again, why would you want to do that?

[Peter the Greek]

Paul, I believe Rawl's concern is that if the speaker isn't coupled to the concrete that it'll invite movement in the speaker (albeit small) which is a bad thing.

Personally it wouldn't bother me if it was or wasn't. I've seen plenty of rooms now with a soundproofed floor either on second floors or a bearer construction and its never bothered me.

But in saying that, I think Rawl was saying that if you can have concrete (something heavy to couple your speakers to) you may as well use it.

Sorry Rawl if I have misinterpreted all that.

[3G_]

... and again, why would you want to do that?

I am not qualified to answer having neither tried or hear the suspended floor which is raised, I was simply giving a simple possible solution to the suggested problem which a suspended floor may give.

[rawl99]

Paul, I believe Rawl's concern is that if the speaker isn't coupled to the concrete that it'll invite movement in the speaker (albeit small) which is a bad thing.

Personally it wouldn't bother me if it was or wasn't. I've seen plenty of rooms now with a soundproofed floor either on second floors or a bearer construction and its never bothered me.

But in saying that, I think Rawl was saying that if you can have concrete (something heavy to couple your speakers to) you may as well use it.

Sorry Rawl if I have misinterpreted all that.

No good sir. No misinterpretation on your part. As someone I know well often says "better is the enemy of good."
Nothing bothers us in audio until we hear better.
Or until we hear the absence of a problem that we did not know existed, eg speaker cabinet resonance or vibration. Once one experiences a bookshelf sitting on an exceptionally well engineered stand sitting directly on a concrete floor, then the type of situation you describe, ie sitting on suspended rubber isolated timber floor, becomes intolerably colored and smeared in the sonic presentation. Ditto for a floor stander.

Rawl

[rawl99]

... and again, why would you want to do that?

Basic physics wrt vibration control. Couple the vibration from the speaker into a MUCH larger mass

Rawl

[Paul Spencer]

If we are talking about the 3 way horns, I wouldn't be too concerned about that. A horn at 100 Hz would surely have a very low moving mass and plenty of mass in the horn itself to counteract. Any steps to "lock" the horn into place against forwards and back motion of the drive units would be overkill - the kind that might make you feel good, and arguable worth doing for that reason, but questionable regarding audibility. Not that I'm against overkill, far from it.

I'd be a lot more interested in how well damped the horn walls are and how diffraction within the horn and at the mouth is handled.

In the 20 - 100 Hz range I'd suggest mounting drivers dual opposed, which then takes care of mechanical vibrations where they are likely to cause problems. The problem is then dealt with right at the source. It also means the entire bass horn will also have less vibration and you can relax the need to have it solid. Very very helpful when you want a big bass horn that does not require a crane. I managed to shift my T20 20 Hz horn from the workshop into the room around some awkward corners. It shakes the whole room but does not vibrate like a box of similar construction and design. You can't tell if it's in use by feeling the walls of the box. To achieve the same thing without dual opposed, it would be a box needing 4 to lift and it would probably be too heavy to get into place under the floor.

You can actually test out dual opposed if you have two sub drivers either side of a box. You turn one of them off, the output drops by 6db (half volume) but the box vibrates a lot more.

[3G_]

I was thinking of the horns just earlier, the driver simulations are for 3 or 4 mm of travel @ 100Hz.I am sure the sand filled 3mm walled steel frame will suffice for now if correctly built and levelled.

[rawl99]

If we are talking about the 3 way horns, I wouldn't be too concerned about that. A horn at 100 Hz would surely have a very low moving mass and plenty of mass in the horn itself to counteract. Any steps to "lock" the horn into place against forwards and back motion of the drive units would be overkill - the kind that might make you feel good, and arguable worth doing for that reason, but questionable regarding audibility. Not that I'm against overkill, far from it.

I'd be a lot more interested in how well damped the horn walls are and how diffraction within the horn and at the mouth is handled.

In the 20 - 100 Hz range I'd suggest mounting drivers dual opposed, which then takes care of mechanical vibrations where they are likely to cause problems. The problem is then dealt with right at the source. It also means the entire bass horn will also have less vibration and you can relax the need to have it solid. Very very helpful when you want a big bass horn that does not require a crane. I managed to shift my T20 20 Hz horn from the workshop into the room around some awkward corners. It shakes the whole room but does not vibrate like a box of similar construction and design. You can't tell if it's in use by feeling the walls of the box. To achieve the same thing without dual opposed, it would be a box needing 4 to lift and it would probably be too heavy to get into place under the floor.

You can actually test out dual opposed if you have two sub drivers either side of a box. You turn one of them off, the output drops by 6db (half volume) but the box vibrates a lot more.

Paul,

I agree absolutely with your suggestion of dual opposed. This makes a world of difference.
Given 3G's description of the sloping site it is reasonable that the bass enclosure can be decoupled mechanically from the concrete slab. That will leave primarily the bass pressure waves to excite vibration in the floor 'diaphragm'.
If the mid and upper horns are sitting on this 'diaphragm', ie the isolated timber floor, then the low bass energy excitation of this floor will be coupled into the horn enclosures sitting upon it with the resultant coloration/modulation/smearing effects I mentioned before.

If the mid and upper enclosures are coupled to the slab then we get:

Bass coupled to earth ( the heavy big round ball)
Mid and high coupled to slab (also linked to the big round ball)
Bass energy excitation within the room excites the isolated green glue laminated floor which is coupled to.... Nothing. The green glue will help to dampen bass energy excitation of the isolated timber floor reducing re-radiation from the floor back into the room.


I can't really explain it any more simply than that.

Damping of horn walls and the diffraction design is obviously critical to the end result.

Rawl

[GregWormald]

When I auditioned the SGR CX4F speakers in *SGR House* , the bass notes moved the concrete floor to which the speakers were spiked. Standing next to the speakers, listening to Melody Gardot, my feet were vibrating. I can't remember how many tonnes of concrete Harry said were in that part of the floor, but it seemed to be an amazing amount. IIRC it was at least 400 mm deep to raise that room above the level of the other rooms.

Here at home, with the same speakers, playing the same music, the standard concrete slab vibrates not at all. Not being willing to deconstruct both floors and houses, I have no idea what makes the difference, but I prefer the sound in my room.

Greg

[Paul Spencer]

Rawl, I thought the speakers were sitting on top of a concrete floor, unless I've missed something.

driver simulations are for 3 or 4 mm of travel @ 100Hz

... and about 125 db SPL?! More typical would be 0.3mm with a horn loaded 8", 1w input and around 100 db output in the listening position. If the horn is tuned a bit lower, then excursion is more like 0.1mm. Dial it back to 90 db, again with the slightly lower tuning and your excursion is now about 0.03mm. I don't know the design of your particular horn or what drivers, but the momentum involved here is going to be pretty minor.

One example. B&C 8PE21 is one driver that might get used in a design like this. mms is 18g

If you have a sub driver with 10x as much mass and over 1000x as much excursion then you have a very different situation!

[3G_]

Yep that was at max spl If I recall correctly. The 8" b@c was the driver I was going to use until the fane 8m was made for us to order

[rawl99]

When I auditioned the SGR CX4F speakers in *SGR House* , the bass notes moved the concrete floor to which the speakers were spiked. Standing next to the speakers, listening to Melody Gardot, my feet were vibrating. I can't remember how many tonnes of concrete Harry said were in that part of the floor, but it seemed to be an amazing amount. IIRC it was at least 400 mm deep to raise that room above the level of the other rooms.

Here at home, with the same speakers, playing the same music, the standard concrete slab vibrates not at all. Not being willing to deconstruct both floors and houses, I have no idea what makes the difference, but I prefer the sound in my room.

Greg

Greg,
In your house is the slab the bottom floor? Ie sitting on the ground?

Perhaps at sgr they built a raised suspended slab to lift up the 400 mm. That would make your slab coupled to an immense mass, that big round ball of earth again, that would act as a massive vibrational sink.
If the slab at sgr is raised, suspended, then excitation of resonant modes is a very common thing. As I commented earlier, vibration control is a very fickle area. One would think that a speaker would not have sufficient energy to vibrate a concrete slab. As you have experienced for yourself, nothing could be further from the reality. This is why, in my experience, the listening rooms that I have done in a ground floor arrangement have always performed better.

Rawl

[rawl99]

Rawl, I thought the speakers were sitting on top of a concrete floor, unless I've missed something.



... and about 125 db SPL?! More typical would be 0.3mm with a horn loaded 8", 1w input and around 100 db output in the listening position. If the horn is tuned a bit lower, then excursion is more like 0.1mm. Dial it back to 90 db, again with the slightly lower tuning and your excursion is now about 0.03mm. I don't know the design of your particular horn or what drivers, but the momentum involved here is going to be pretty minor.

One example. B&C 8PE21 is one driver that might get used in a design like this. mms is 18g

If you have a sub driver with 10x as much mass and over 1000x as much excursion then you have a very different situation!

Paul,

Th setup I suggested is as my post above,
Subs under floor, decoupled,
Mids and high coupled to concrete slab through the timber floor. ( so yes those speakers are sitting on the concrete slab)

Timber floor times 2 with green glue laid over rubber as suggested by Elill, then carpet etc.
Timber floor acts to isolate airborne energy from concrete slab minimizing the slab resonance as mentioned by Greg.

The momentum of the driver that you speak about has little to no relevance wrt what I am suggesting in this particular instance. What I am trying to achieve for 3G is to stop slab-borne resonances coupling into the horns causing mechanical inter modulation effects with the drivers. As you mention, the driver excursion is rather small at normal listening levels so the effect I speak of becomes more of an issue rather than less.

Cheers
Rawl

Edited by rawl99, 25 April 2012 - 10:00 PM.

[GregWormald]

Rawl,

My slab sitting on the ground--yes. And extra thick to accommodate the hot water under-floor heating.
SGR's--don't know, but I'll ask.

I have always found the time required to get the spikes seated properly on the floor to stop **any** speaker box movement well worth while. Even when with 4 spikes it can be a pain.

Greg

Edited by GregWormald, 25 April 2012 - 07:24 PM.

[rawl99]

Rawl,

My slab sitting on the ground--yes. And extra thick to accommodate the hot water under-floor heating.
SGR's--don't know, but I'll ask.

I have always found the time required to get the spikes seated properly on the floor to stop **any** speaker box movement well worth while. Even when with 4 spikes it can be a pain.

Greg

Greg,

You are extremely fortunate to have the thicker slab. Worth it's weight in gold it is.
And I agree wholeheartedly with setting up the spikes as perfectly as you can. Again well worthwhile. Please be so kind as to share with us specifically what improvements you hear from this 'small' attention to detail.
I will keep my comments to myself for the moment so as not to colour your thoughts/experiences. I shall share mine after you.

Look forward to hearing your experiences Sir.

Regards
Rawl

[GregWormald]

I had an email exchange with Harry at SGR and we can't find a "floor reason" for the slight vibration of his floor (it was really *just* perceptible).
I am now thinking it might be the rest of the differences between the rooms. I have quite a large room with cathedral ceiling, wooden walls and lots of glass and wide doorways, a half height wall into the kitchen, and part of each side wall projects into the main room by about a metre or so, so any standing waves and reflections are very broken up. One wide hallway to the library even goes off at a 45° angle! It is really a very nice room for music reproduction.

Getting the spikes 'perfect' seems to both tighten the bass up and make the lower bass more distinct. I sort of think there is a bit more bass too, albeit only a little, but the extra clarity in the bass notes is what makes it worthwhile for me.

There may well be mid-range clarity and imaging improvements too, but I've been fussy about this for more than 25 years and the memory of all the reasons why I found it worth the time have faded. The fact that I do remember it being a "good thing" has not, and it is just a part of my set-up routine.

It does make it tiresome when changing rooms or equipment, 'cause I do it for each speaker positioning trial. I use a tape measure to get the position exact, an adjustable angle to get the toe-in, and then a good level to get the speaker correct in all 3 planes. I then lock the spikes with two wrenches on the locknuts. I test by pushing lightly in every direction to check stability and then by pushing hard! I go back after a week or so and check for any settling.

Greg

Edited by GregWormald, 26 April 2012 - 08:32 PM.