DIY M&K In Wall Sub - will it sound good?

Mad Monk · 13-07-2009, 1:06 PM

I saw these on ebay and was thinking of buying them to use in a DIY in wall install as I am really pushed for space in my multi purpose gym/cinema room. I was considering lining up 4 odd speakers underneath my screen to provide me with my bass.

I only have a depth of 4" in the wall to play with. My walls are

4" Brickwork
3" Celotex insulation
4" Brickwork

I suppose that I could cut out the 3" of Celotex to expose the external brickwork and insulate that somehow, this would give me a depth of only 7".

I did some calculations over at hometheatreshack and 4" is practically no space at all if I am to go by the recommendations off the guy who is selling these on ebay. He recommends 1.3 - 1.75 cubic feet whereas a 4" enclosure will give me barely .3 cubic feet.

I really don't want to build a false wall in front of my main wall as the room is small enough as it is plus I will need solid walls to hang some equipment.

Has anyone built a DIY in wall sub and if you have how did it sound? I used to build speakers boxes for custom car installs 15 years ago so the build quality should be pretty good if I can get the box dimensions right.

Any thoughts would be much appreciated on my choice of speaker or the install itself.

Thanks

k13 wjd · 13-07-2009, 2:01 PM

Hi, I too used to build in car stuff, full car installs, i.e boot and rear seat area, completly fibreglassed etc......As im sure you'll know, you end up adding more and more speakers and amps, to counteract the lack of volume AND odd box dimensions.

What i would do, and its just my idea.....Find/buy some mdf, and build the box to size....then, try it out....see how its going to sound, prior to commiting to cutting walls etc.

Im sure someone here will come up with a better suggestion....Is it really a great idea to have the subwoofers facing you ???

Im not sure...

Mad Monk · 13-07-2009, 2:22 PM

Quote:

Originally Posted by k13 wjd

Hi, I too used to build in car stuff, full car installs, i.e boot and rear seat area, completly fibreglassed etc......As im sure you'll know, you end up adding more and more speakers and amps, to counteract the lack of volume AND odd box dimensions.

What i would do, and its just my idea.....Find/buy some mdf, and build the box to size....then, try it out....see how its going to sound, prior to committing to cutting walls etc.

Im sure someone here will come up with a better suggestion....Is it really a great idea to have the subwoofers facing you ???

Im not sure...

For the price I guess it's worth doing. At £200 for the 4 drivers I can't go too wrong, if it all goes belly up I'll just have to give them to my nephews for their car boot subs.

I have a friend coming over from the states so I need to pull the trigger pretty quick if I am to avoid and postage and custom charges.

Thanks for your suggestion.

BlueWizard · 13-07-2009, 5:47 PM

You have brickwork interior walls and brick work exterior wall with an insulation filled gap in between. What type of insulation is it? That is, is it soft fiber insulation or stiff foam insulation?

If it is soft fiber insulation leave it there. If it is ridged foam insulation, that complicates things as the foam leaves no space for the required speaker volume.

Next, are there barriers in the walls? Boards, rafters, studs, etc? The cabinet volume is all the horizontal and vertical space available until you run into some type of barrier. In standard wood and plaster construction walls, that would be a space 17" wide, by 8' tall, by 3.5" deep or (17 x 96 x 3.5 = 5712 / 1728 = 3.31 cubic feet).

Next if the interior wall is brickwork, how do you plan to cut a hole to accommodate the speakers. Are you going to try to cut a precise round hole for the speaker? Or, are you going to cut out a large square section, mount the speaker to a board, then mount the board to the brick?

Then the next question is, do you really feel you can adequately secure the speaker or the speaker board to the brick?

And do you feel that cutting a large section of brick out of the wall is going to devalue your house?

Next question, is the interior brick exposed, or is it covered with some type of wall board?

Next, unlike brick houses in the USA where the brick is merely a facade, I assume the brick in your house is part of the structural integrity of the house. Are you undermining that structural integrity but cutting into the brick?

A lot of things to consider. Personally, with brick interior walls, either build a false wall or build stand alone cabinets.

The false wall doesn't even really have to be a full false wall. It could be more like wainscot. You could build a section out from the wall, say about 3 feet high and 12" to 16" deep. Sections of it could be enclosed for your subwoofers, and sections of it could be shelves for you equipments. The top area could be a slightly wider shelf to set the TV on, or just general odds and ends (books, etc...).

Just a few thoughts.

Steve/bluewizard

Mad Monk · 14-07-2009, 1:00 PM

Thanks for the reply Steve.

I'm not too worried about the structural integrity of the house being effected as the room is a first floor one that does not share the load of the main roof. My structural engineer has told me that I have no problems at all should I wish to have openings in the wall just as long as I use a 3x4 concrete lintel or similar sized piece of wood to act as a platform for the brickwork on top of the box.

The insulation I'm using is called Celotex CW3000.

Quote:

With low emissivity foil facings, CW3000 is manufactured from rigid polyisocyanurate (PIR) uniquely reinforced with glass fibre using a blend of blowing agents that have zero ozone depletion potential (zero ODP) and a low global warming impact

The room's construction is going to start soon and as it is a solid wall there are no openings or barriers as the only opening in the wall will be the one that my bricky leaves. I understand that if it was a stud wall I'd have room inside to play with but I don't have that option.

My plan was to have a square shaped hole in the wall which I would line with 4x3 timber. I was then going to fix the sub onto a 1.5" board and screw that board onto the 4x3 frame in the wall leaving a flush finish. On the inside of the lining and on the insulation board I was planning on sticking some very thick foam to it once I had sealed all of the corners and edges.

The interior brickwork is going to be rendered and then plastered over which will be appx half an inch in thickness. I really can't build any type of false wall or have any type of structure sticking out of the wall to house the subs. The room is a matted gym area and I can't risk someone being judo thrown and bashing their head on any sharp edge whatsoever, hence the in wall route for all of my speakers. All of my equipment is going in the loft in order to keep the room clutter free and also help keep the temps down.

I do like the idea of the wainscot though. If I can have protruding no more than a few inches whilst bevelling off the top to avoid any sharp edges it may just work. Would this area inside of the wainscot act as the cubic capacity of the subs in place?

Indy

**Bald Monkey** · 14-07-2009, 1:28 PM

Moving to the Subwoofer forum as per OP's request.

kwakr · 14-07-2009, 3:41 PM

fwiw - don't let the drivers dictate the design - at least not the drivers you linked to as they don't appear to be that special in terms of mechanical or electrical parameters.

How large is the room and what sort of final design are you considering - 4 dissimilar drivers could be difficult to have work well together in the first place, without adding less than optimal enclosure spaces and tuning into the mix.

I'd suggest quality over quantity - certainly when trying to reproduce sub bass frequencies.

Nimby · 14-07-2009, 4:11 PM

If you bung a 33Hz driver into a small sealed space the system frequency will shoot up like your blood pressure when you asked for some bass and got nothing.

No mention of Xmax and you'd need 12 x 12" for an IB anyway.

If you'd given us more time you could have ordered a couple of hand made Fi IB18s and had a world class IB system which was completely lost in a hole right through the wall to another room/attic/underfloor or cupboard. No projection on either side. Just great bass.

My advice is don't even consider using these drivers for your intended in-wall project.

Russell.Williams · 14-07-2009, 4:15 PM

The MK drivers are quite specific to working in sealed boxes and the protection against over excursion that provides. I would caution against using them in-wall unless you have a way of guaranteeing against air leeks, because they will just destroy themselves in fairly short order unless sealed effectively.

Russell

Nimby · 14-07-2009, 5:20 PM

Quote:

Originally Posted by Russell.Williams

The MK drivers are quite specific to working in sealed boxes and the protection against over excursion that provides. I would caution against using them in-wall unless you have a way of guaranteeing against air leeks, because they will just destroy themselves in fairly short order unless sealed effectively.

Russell

Really? I thought M&K subs were usually those weird, ported, dual driver jobbies with no real bass?

albriscoe · 14-07-2009, 5:45 PM

Quote:

Originally Posted by Nimby

Really? I thought M&K subs were usually those weird, ported, dual driver jobbies with no real bass?

Jealous, just jealous

Nimby · 14-07-2009, 6:09 PM

Sincere apologies for the deleted post.

Not what I meant at all.

Post in haste. Repent at leisure.

Russell.Williams · 14-07-2009, 10:02 PM

Quote:

Originally Posted by Nimby

Really? I thought M&K subs were usually those weird, ported, dual driver jobbies with no real bass?

I can't remember an MK that ever had a port.

If however you mean push-pull sealed subs, then yes; that's them.

Russell

Nimby · 15-07-2009, 6:09 AM

MX90 & MX350THX, MX5000THX?

All seem to have lost their radiator grill.

Dare I suggest an image search, Sir?

Mad Monk · 15-07-2009, 11:13 AM

Thank you for the replies gents.

My internal room measurements are 4m x 4.1m x 2.7m high. Here are some images of the room layout

I did some reading up until the late hours of last night and came across these guys who do a slim line woofer but to be honest I'm thinking of doing something very similar to what Nimby has done using those IB15's or something using another equally good speaker.

Would it be possible to get decent bass if I house a huge speaker box into my ceiling clamped onto a beam that I have running down the centre of my room? It will be very rigid. Would the insulated roof area where the back of the speaker box be sitting in be good for this type of setup?

Judging by the prices of those IB15's and the sound that they can give it really does sound like a no brainer.

@ Nimby, I had a read over at the AEspeakers sites, which ones would you recommend now that I am seriously considering turning my ceiling into one big subwoofer?

I have time as there is plenty of work to do around the house so I'm in no rush should I need to order something from abroad.

I think I better head on over to the room acoustics and calibration section now that big bass may be heading my way

Cheers

Nimby · 15-07-2009, 12:10 PM

I'd forget about IB until you can get a larger room with better proportions.

Buy or make a cylinder sub and put it in a corner. It won't take up much space.

Mad Monk · 15-07-2009, 12:26 PM

I don't think that's going to be possible as I've a M&K 1250 sub in my current gym and it has caused a few sore heads already. Any speakers must be placed in the walls or the ceiling.

Will the IB15's sound poor in such a small room or are you saying that it will be a waste of money? If it's the latter I don't mind building such a box as the 4 speakers are very cheap. If it fails in my HT I can always integrate them into my loft office area which is 5.2m x 6m so a tad larger.

Nimby · 15-07-2009, 2:58 PM

The problem with smaller room is that the room gain tends to produce a rising response into the deep bass which can become a bit much. Your room is almost square which will produce odd results somewhere around 40hz. The office sounds like a far better bet. If it is already in the loft it could be just a matter of placing a manifold against the wall firing into the rest of the loft. A couple of IB15"s or IB18"s would probably do if you aren't a complete bass head. I believe there is some problem with availability of 15" driver baskets at AE so you may have to consider Fi at UK prices. $US = £GB. By sheer coincidence somebody here pointed me to Blade ICE as the European distributor only today. Superb drivers if you can afford them at these UK prices. Prices are so similar for the different sizes that you should seriously consider a couple of IB3 18"s.

Mad Monk · 15-07-2009, 3:25 PM

Thanks Nimby, I just checked out Black ICE and they seem to have the IB3's in stock. I'll do some further reading into them tonight and the type of enclosures they recommend. Hopefully they are a little flexible on the price if I buy 4 odd speakers. The speakers look identical to the US IB15's, are they the same speaker only in different sizes?

At the moment the US versions from AE are less than half price and thus could be the ones that I end up going for unless I can get away with 2 x 18" IB3's.

Nimby · 15-07-2009, 4:05 PM

2 x Fi IB3 18"s = 4 x AE IB15"s

AE is struggling to find 15" baskets according to their forum so forget about AE for the moment. You can't avoid VAT or freight so the Blade ICE prices for a couple of IB18s is a hassle free bargain.

The box (manifold) for an IB is dead simple: An open sided box 1.5" thick (a layer of 3/4" MDF + 3/4" OSB or 3/4" plywood) and large enough to hold the drivers. It doesn't have to be pretty because hopefully you'll hide it out of sight.

Have a look at the Cult of The Infinitely Baffled forum galleries and FAQs for examples.

Russell.Williams · 15-07-2009, 4:29 PM

Quote:

Originally Posted by Nimby

MX90 & MX350THX, MX5000THX?

All seem to have lost their radiator grill.

Dare I suggest an image search, Sir?

Yup that's them.

Polish your bifocals and remove the sterident splashes from your screen and you'll see that they're sealed push/pull designs.

The hole at the bottom is just a vent for the bottom driver - there is no tuned port.

Russell

Nimby · 15-07-2009, 4:49 PM

So the second driver could just as easily have been placed on the exterior of the box and avoided all that extra "boxy colouration"?

I'm a Colgate Man, myself. 'Brings up 't nickel plating on 'told, National Health bifocals a treat.

albriscoe · 15-07-2009, 6:07 PM

Quote:

Originally Posted by Russell.Williams

Yup that's them.

Polish your bifocals and remove the sterident splashes from your screen and you'll see that they're sealed push/pull designs.

The hole at the bottom is just a vent for the bottom driver - there is no tuned port.

Russell

I wanted to say that Russ but couldn`t put in into words that I knew you could and it wouldn`t have had the same effect

Mad Monk · 19-07-2009, 10:33 PM

Quote:

Originally Posted by Nimby

2 x Fi IB3 18"s = 4 x AE IB15"s

AE is struggling to find 15" baskets according to their forum so forget about AE for the moment. You can't avoid VAT or freight so the Blade ICE prices for a couple of IB18s is a hassle free bargain.

The box (manifold) for an IB is dead simple: An open sided box 1.5" thick (a layer of 3/4" MDF + 3/4" OSB or 3/4" plywood) and large enough to hold the drivers. It doesn't have to be pretty because hopefully you'll hide it out of sight.

Have a look at the Cult of The Infinitely Baffled forum galleries and FAQs for examples.

Thanks so much for tip on visiting the Baffled forums. I've spent a few days lurking but have plucked up the courage to ask a few noob questions.

I'm definitely going to go down the IB route and will be housing my speaker manifold in the ceiling. I spoke to my carpenter about making a flush finish with the ceiling whilst at the same time making it secure and he assured me that it will be no problem and not to worry about a 300lb manifold falling on someone's head.

This is exactly the type of bass I was looking for cheap, loud and low

I'll update this thread as I begin construction, but as the box manifold is going to be so large I'm going to have to wait until the room construction starts before I get cracking. I think the best thing to do is to build the manifold in the room to stop me having to cart it from my garden to the HT.

Great blog Nimby, although I doubt the sub manufacturers think the same

recruit · 19-07-2009, 11:04 PM

Quote:

Originally Posted by monkeykong

Great blog Nimby, although I doubt the sub manufacturers think the same

I doubt they'll be worried as IB is to the extreme and I would of thought the number of people to be relatively small compared to the masses of AV folk who will settle for box subs....

Nimby · 20-07-2009, 6:08 AM

Quote:

Originally Posted by recruit

I doubt they'll be worried as IB is to the extreme and I would of thought the number of people to be relatively small compared to the masses of AV folk who will settle for box subs....

My latest manifold will probably put off more people than it will ever recruit to IB.

It really is a monster but no larger than some high-end speakers like the bigger Wilsons and electrostatic panels.

There is no way I'd have one in the room but it doesn't really matter where it is sitting now. I just didn't have anywhere sensible to put another 4x15" manifold on the other side of the speakers. So all eight ended up in one big box.

Good luck with your IB installation mk.