Home Theater Forum and Systems banner

1 - 20 of 36 Posts

·
Registered
Joined
·
29 Posts
Discussion Starter #1
I’m an old audiophile since back in the ‘80ies. I'm realising, that I'm mainly watching movies and rarely listening to music in the living room these days.

I am now looking for and hoping to get som input and advice on how to achieve my “Invisible Subwoofer” build. I’ve as always done a lot of reading, which has led me to the DIY track in stead of getting a finished stand alone sub. But I need help. :dontknow:

Background
I currently have a MJ Acoustcs Reference 200 sub, which is very good for music, and integrates very well with my main Vienna Acoustics Mozart speakers. It is however not at all up for the task when it comes to movies - not even at moderate levels - no fun at all :rolleyesno: . And even for music, it struggles a bit to really convince in the lower end when playing loud(ish) due to the big room it’s in. But what it does, it does brilliantly.

Location of new DIY sub
I’m intending to replace the 3 drawers in the middle of the cabinet under my TV (see pic) with a DIY integrated sub. It would ideally be an integrated down-firing construction.

This way, with the drawer fronts reattached, it would be completely stealth :bigsmile:. That greatly improves WAF and by that budget is also much more flexible :whistling: There is plenty room for any sub-amp in the adjacent cupboard (below the TV on the photo) with the rest of the A/V stuff and the center speaker in there.

Cabinet details
The cabinet hangs on the wall and is supported at the front by adjustable steel legs.
The outer bounderies of the sub is given by the inner bounderies of where the drawers were.


The cabinet has the internal dimensions / outer sub bounderies of 54,5H*56,8W*56,2D cm / 21,4*22,4*22,2 inches
That adds up to 174l / 6,15cft gross volume.
The cabinet is 17cm / 6,7” off the floor.​

The walls of the cabinet are 1,6 cm particle board with vinyl film. Sides are essentially double, as the ajacent elements are built the same way. Top has the added top plate (1cm). Rear is only a few mm. thick masonite plate, and then there is a gap of 1,6cm to the wall on which it hangs. So there is some structural support that can go into the combined sub enclosure.

The room
As can be seen from the attached picture and plan, the room itself is around 111m3/4000cft, open into a kitchen/dining room around half that size, so the sub 'sees' maybe 6000cft.
One side of the listening area is almost all glass. Other walls are drywall with rockwool insulation behind and then brick outer wall. Floor is lackered wooden parquet floor and ceiling is thin gypsum plates. Roof height is 2,37m/7,8ft.

What do I want for sound
I want deeeep bass. I’m thinking 20Hz before significant roll-off including room gain.
I want higher SPL than what I’m currently getting from the MJ Acoustics.
I want a fast, tight bass that properly represents the timbre of what was recorded.
I will happily sacrifice a few dB’s to more precise tight bass.
I want bass that is entertaining in movies :bigsmile:


How do I achieve this?
This is where you guys :nerd: come in :help:

My initial thoughts are, that the construction could be built like a stand-alone solution precisely to the dimensions above, and then slid into the cupboard and fastened in place there - obviously with any holes pre-cut, and by the materials taking into account the added support/strength provided by the cabinet.

I have an idea, that the most suitable solution will be a sealed cabinet with an 18” driver. I’m however completely open to other ideas and suggestions.

I need input on everything:
  • Construction type - sealed, ported, transmission line, ...?
  • Driver type and size
  • Amplifier
  • Equalizer
I live in Denmark, so components avaliable here or in Europe will be easier to source. USA items will have an added 30% in customs and tax on top of any shipping costs. But if the right driver/amp is US only, I’ll import it... Budget is flexible, but I'm hoping to keep parts within $1.000 before enclosure build. Can be significantly increased if the reasons are good.


Attached ground plane and photo of listening area and intended location.

Your questions, thoughts and suggestions, please :wave:
 

Attachments

·
Registered
Joined
·
147 Posts
Welcome to DIY, and a warning: it can be quite addicting. You have a very neat and attractive listening room. Based on your comments about the accuracy of tone and desire for a "musical" sub, I'm thinking you probably would like a good 15" driver with a Qtc around .707. An 18" driver would move more air, but is harder to control than the 15" and therefore more liable to distortion. A good 15" driver will definitely suit your needs for solid, accurate low bass.
Unfortunately, I don't know what is available in Denmark other than B&O. Perhaps you could suggest some brands available to you and I could research the parameters and look at designs.

Tom
 

·
Registered
Joined
·
29 Posts
Discussion Starter #3
Hi Tom.

Thanks for the kind words and for taking the time.

I was actually starting out thinking that it had to be a 15" from the mere logic you refer to - precision. However, after reading countless posts across the interwebs, I was beginning to doubt if my 'old school' logic would apply to current sub-design pronciples; as i seems that people are successful in driving 18" drivers very controlled, and by the larger size having to use less effort for the same effect, hence less distortion. And then I have this difficult room to take into account as well, which I belive requires some amount of air-moving to fill.

You seem to suggest that my initial assumptions going into this was not completely off. However, everything is a compromise, and i could be inclined to 'sell' the last few percent of accuracy to a convincing HT performance (maybe requiring 18"?).

Denmark actually have been quite well off with HiFi and speaker manufacturers beyond B&O. You may know e.g. Dynaudio, Peerless and ScanSpeak, which are all Danish. That doesn't translate to what is available to buy at reasonable prices though. Online availability in EU is what I will be looking at as preferred (UK is often a good place for price). One place with a reasonable selection inside EU seems to be here (I can't link, but its thomann dot DE and then the PA section top of page, then Speakers and Speaker components where there are 15" and 18" categories). Thats place I found when looking for different options like Eighteensounds. That could be a place to find some options.

If some driver(s) not available there comes to mind as ideal, I would do the research for where they can be purchased inside EU, or otherwise - as mentioned - I can ultimately import.

I don't have any immediate rush to get this done. I would rather have it to be right for a long time (as it effectively will be part of the furniture).
 

·
Registered
Joined
·
147 Posts
There's no doubt that Denmark is the home to some of the best quality speaker driver manufacturers. But subwoofer drivers don't seem to be a big part of the product line. There is a big difference between the PA speakers on the Thomann site, and the home theater drivers I think you are looking for. (Unfortunately, most of the Thiele/ Small parameters for the drivers are not listed on the Thomann site. We need at least the "big 3" specifications: Fs, Qts, and Vas, to get started on modeling a design. But I will keep looking- I'm sure they're listed somewhere.) PA drivers are designed primarily for high SPL output in the mid-bass (40-100 hz), but not for the really low bass found in movies. PA drivers are very efficient in this, but really not good for home applications.
I think you have a great design idea to put this subwoofer in place of the drawers of your cabinet. Please be prepared to build a separate subwoofer cabinet to mount inside the furniture, as the walls of the furniture are not substantial enough to handle the vibrations and pressures of a sub driver. I usually use at least 3/4" MDF with extra bracing for the walls of a sub cabinet, and 1.5" material for the baffle (driver mounting side of the box).
Have you any experience in modeling sub drivers in cabinets, using software? There is a good, free program for this called WinISD, and another called Unibox. No problem if you don't care to do this, as I am happy to help with this.
I'm going to start my research by looking for a good match between your cabinet and a driver available here in the States, with a budget of around $1000 for amp and driver. (Anybody else following this- feel welcome to throw in!)
Finally, my thoughts are that there is no overcoming the laws of physics- a more massive and therefore more inert 18" cone is going to require more energy to move and control with accuracy than a 15" cone. We can achieve almost the same bass response by moving a 15" cone through a longer excursion as an 18" cone, lacking only in the lowest subsonics, but preserve more tonality (a Qtc closer to transient perfect). But I'll look at both...

Tom
 

·
Registered
Joined
·
29 Posts
Discussion Starter #5
I think starting like you suggest by you and/or anyone else inclined to pitch in simply looking at what you know already from your own backyard probably is the way to get this started. :T

I already figured that it would require a (much) stronger enclosure than the cabinet itself (as indicated in OP) - I'm thinking external enclosure dimensions will have same dimensions as the internal cabinet minus just enough to allow it to slide in and be screwed in place. But he cabinet should help stabilize the construction even more. I assume your dimensions will suffice in this case.

I have no fear to try software, so I'll try and play some with the apps you mentioned. Not sure I'll know what I'm doing exactly :scratch: , but we'll see :R Is one preferred over the other, or are they essentially the same?
 

·
Registered
Joined
·
29 Posts
Discussion Starter #6
Just did a volume calculation, and the internal volume before speaker and bracing will be very close to 140l / 5cft.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #8
Hi Mike.

Thanks for taking an interest in this :)

Not sure what volume you're asking for... :scratch:

In the (long) OP, the cabinet internal volume is calculated at 174l / 6.15cft (i.e. where the buildt subwoofer should fit inside)

In post just above the calculated internal enclosure volume is stated at 141l / 5cft assuming a flush inserted enclosure built from 3/4" MDF and no internal bracing. (i.e. the actual internal volume the subwoofer sees). This is calculated using your Enclosure Volume Calculator elsewhere on this site.

I don't know how much to deduct from the internal volume - I'm assuming it depends on driver, required bracing, if it's ported or sealed and so forth.

Assuming sealed, how much should I brace it / how much volume will be lost to that, and how should the bracing be implemented?
 

·
Registered
Joined
·
29 Posts
Discussion Starter #9
For internal reinforcement I will probably have access to add a fiberglass layer or two. Would that be worth it, not make any difference, or be counter-productive?

I built an integrated custom fit removable sub with an MDF front for the side of my Subaru Legacy trunk(with crucial help from a pro installer), and it is quite rigid. But using the stuff is quite an effort, so maybe it's not worth it compared to what bracing will do?
 

·
Registered
Joined
·
29 Posts
Discussion Starter #11
Hi Mike.

Interesting :)

Internal dimensions would be:
H 21,4 -1,5= 19,9 - if the baffle should be thicker, this measurement is eaqually smaller
W 22,4 - 1,5= 20,9
D 22,2 -1,5 = 20,7

The W and D dimensions are the bottom of the box, which is where the speaker would be.

Please let me know what else I can help with.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #13
Thanks Mike.

Let me see if I get this.

  • The ported 15" will be much more linear unequalised than a closed 18".
  • There is not much more SPL from the 18" anyway, and it would probably have to be dialled down in EQ to make it linear
  • The 18" would provide some more sound sub 18Hz (if that is ever present)
And beyond the chart information:
  • All other things being eaqual - the 15" should be much easier to control for an amplifier than the bigger heavier 18", providing more controlled tight bass.
I'm thinking this is a hands down 'victory' for 15" :clap: - right?

So on that conclusion, what is then a good - no excellent - no outstanding driver to use ?

I can see it's modeled on the Mach5 IXL 15", that appears to sell at a very reasonable price. Is that THE driver to use, or are there better alternatives, and how will they be better. Also taking into account if the money will be better spent on amp or equalizer?

The next question would then also be exactly how is this slot woofer then to be constructed? But that mybe depends on the specific driver ultimately chosen?
 

·
Premium Member
Joined
·
19,397 Posts
The graph shown is the output without any room gain which is room size and shape dependent. The ported 15" will give you what you want, 20 hz extension for movies.

As for control, either driver shown will be well controlled.

The IXL-15 is one of the very few drivers that model this well in 4 cu.ft. Most other drivers need a larger box to get 20 hz extension. The IXL-15 will fit your available space perfectly. If your interested in this driver then contact Mach 5 Audio and see if the shipping charges to Denmark are reasonable.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #15
Thanks :D- I will contact them. Sounds like it's exactly what is needed here.

Meanwhile - any input on how (in lack of better words) the timbre will be - how true to instruments will it be?

About the extension WITH the room gain - what would an alternative be if it doesn't have to model all the way down to 20Hz , assuming the room will help in the low end, and is it even likely that the room will do that looking at it in the OP?

Oh - and by the way - when you say 4 cu.ft. it's because the bracing and speaker will take up appox. 1cu.ft. (?)
 

·
Premium Member
Joined
·
19,397 Posts
Most people will say the best design for music is a sealed sub, for HT a ported would be better. if 20 hz extension is what you're looking for. A sealed UXL-18 would do well with both music and HT.

The IXL-15 is modeled in 4 cu.ft. because of the displacement taken up by the driver, bracing, and the slot port.
 

·
Registered
Joined
·
29 Posts
Discussion Starter #17
OK - so maybe it's still sealed for me (boy this don't get any easier).

You still say it can be controlled quite well. So a capable amp will be able to make the 15" setup more "musical"? The pricedifference to 18" will almost finance an antimode for the 15" <pondering if that will ultimately be better).

The sealed 18" design up above looks anything but linear. That can't really be good? Is that where an AntiMode or similar product would flatten the combined output of the sub/room? Or am I missing something?

Anyway - the 18" is sold out, so maybe other 18" options will have to come into play...
 

·
Premium Member
Joined
·
19,397 Posts
The Antimode will flatten the in room response whithin the driver and amp capabilities. You will be hard pressed to find another 18" that performs as well as the UXL-18 in your given box volume, it would be worth the wait since music and HT is what you're looking for. Unless of course price is no object, then there's the T.C.Sounds LMS Ultra 5400 18" which is $925 plus shipping.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=293-666
 

·
Registered
Joined
·
29 Posts
Discussion Starter #19
Well - I'm flexible with budget, but I'm thinking the Ultra is some ways beyond that when all the other expenses are added... :sweat:

Sounds like it will be the UXL-18 that wins :T , provided they make some (waiting for their answer).

So apart from an AntiMode, then a Behringer iNuke NU3000DSP to drive it?
Or what would be the right way to go for amplifier :dontknow: ?

One other driver option has surfaced though. I can get a SDX-15 from UK pre-used (same guy as the ad - just one of his own units - price not set yet, but likely significantly under UCL-18 when at my doorstep) http://www.ebay.co.uk/itm/SDX15-15-inch-30mm-Xmax-15-Subwoofer-Bass-Driver-/400206181980#ht_3651wt_1396

All the data is in there if you don't know the driver already. It seems to have gotten very nice reviews, but is discontinued.

Would that be a viable option? Anyone know this driver?
 
1 - 20 of 36 Posts
Top