Slowest sub project ever is getting there (but need some advice)

[TEK]

Hello again...

Long time no posts! (but still reading on ;-))
My sub project, a project that has been going on for quite some time now, is finally getting somewhere.
Lack of building places (was building it outside) and issues regarding driver availability, promised drivers not available or not delivered and so on and so on combinded with heavy work load and new children have made this problably one of the longest lasting sub building projects ever :T

But finnaly, after occupying our garage (and putting the car outside in the snow) I'm getting somewhere :B

The box is almost completed. Hopfully I will get most of it done this weekend. I also have the amp (http://www.madisound.com/kgnd.html) and driver (http://www.aurasound.com/pdf/NS18-992-4A.pdf) in place in my garage.

I will hopefully post some building pics this evening.

However, I do have a question.

My box has a actual inner volume of 180L (driver and braces not considered). The driver would problably deserve/like more. Based on this and the Unibox numbers it seems as heavy damping is the way to go, right?

So then my question is: What is heavy damping?
How mutch (%) of the sub should be filled with damping material and what type of material should I use?

PS: The sub will have a inner matrix, meaning that I will either get the damping correct the first time, or have to build a solution where the top of the sub might be taken on and off again. I will not be able to reach all the parts of the sub from the driver hole after the top is fixed on.

Best regards, Trond-Eirik

[cdwitmer]

I doubt that you are going to get the additional compensatory stuffing right the first time; however, that may not be a problem as the stuffing does not need to be evenly distributed throughout the enclosure. How much of those 180 liters can you access from the driver mounting hole?

[TEK]

Hmm, when I think about it, if I use both the amp mounting hole and the woofer mounting hole, I should be able to reach approx 70% of the space.

However, then the stuffing would have to be added in small bits, as the matrix will prevent me to apply big pices at once.

[ThomasW]

The usual fill recommendations are 0.5-1.5 lbs/cu ft. So might as well start with 1lb/cu ft.

Fiberglass is best but would be a real pain given your construction. So use loose poly fill, tear it apart and fluff it up before sticking it in the box.

You'll want to fine tune the performance. So once it's up and running, experiment by adding in additional damping add in 4-6oz at a time. With each addition the sound should get a little tighter . When it no longer gets tighter, and the only inpact is a decreased output level, fall back and remove the last amount added.

[TEK]

Thanks a lot for the input. How to know when I had enough fill was my next question, but it seems like Thomas knew what was coming up :P

Tonight I will get the matrix adjusted to the driver and amp as well as get the holes drilled; (to make the air able to flow between the different "cells" of the matrix)
At least I hope so 8)

Btw, Here's some construction pics. No glue applied yet.

I'll add some more later on. The camera was full, so this was all I got.

[TEK]

Some data about the box:
NN is what you see that the matrix is made of, dont know the english name. Stiff and light material

Outer size: 120cm x 60cm x 37cm
Bottom: 2cm MDF + 1cm NN + 1.2cm MDF
Long sides: 2cm MDF + 1cm NN
Short sides: 2cm MDF + 1.2cm MDF
Matrix: 1cm NN
Top: 2cm MDF (then 1cm air, then 1cm NN, then soft stuff to sit)

Phase 1: Get the sub up and kicking
Phase 2: Get the whole thing covered by leather and make seets on top of it

Regards, Trond-Eirik

[cjd]

How does air move between the sections of the matrix?

Looks interesting.

And the last pic looks almost like it did at midnight when we got home after a trip to visit my grandparents. Had to shovel to get the car into the driveway past all the snowplow leavings.

C

[TEK]

Some more pics.
Now the airflow between the cell of the matrix is handled.

The inside box also show how the box has fitted tracks that the plates of the matrix is placed into.

Tomorrow I will hopefully get started on adjusting the top plate as well as gluing the box together...
I have to buy some stuff first, so it might be a bit optimistic, but we'll see.

[cjd]

Don't let Brian Bunge catch you at that kind of hole making! :P

Lookin good.

C

[TEK]

Don't let Brian Bunge catch you at that kind of hole making! :P

Lookin good.

C

The nice thing about it is that no one is ever going to see those holes (except you folks of course)...
So I'm not to afraid about that :W

But sure, if I had had the proper tool to drill nice holes with, I would have used it. But I could either go out and by the tools, or get it done...
So I got i done! :twisted:

[Brian Bunge]

Don't let Brian Bunge catch you at that kind of hole making! :P

Lookin good.

C

Holy Shit! All those holes make my head hurt!!

I haven't used a table saw or router in over a month now. I'm starting to have withdrawals!

[Bent]

neither has he - I think he used a howitzer.
:ROTF

[TEK]

Getting there, getting there...

Some more work was done this evening.

"top beeing prepared 3.JPG":
Adjusting the top plate so that it fits and locks into the matrix. I testing it by fitting it onto the sub afterwards. It looked as a very nice and tight fit.
(Here you can also see my fabolus workbench :T )



"sidewall 1.JPG"
Just a shot by the long sidewass sandwitch standing mounted



"bottom 2.JPG":
Just a short of the bottom sandwitch when not mounted



"cutout 2.JPG"
The box without a sidewall, almost like those fancy pictures beeing shown by the professionals :W



"glueing 1.JPG"
Finally starting to glueing this baby together...
The top will be added separatly after the initially filling is done.



Regards, TEK

PS: What's a "howitzer"?

[ThomasW]

PS: What's a "howitzer"?

Looks like a tank but with a much bigger cannon

[TEK]

Looks like a tank but with a much bigger cannon

he, he

As I recall it's mostly build according to your requirments/ideas regarding thickness and material. The inner walls/bracing might be of a different kind than what you recommended, but it was the strongest I got my hands on. Very much less havy than MDF.

There is a very noticable difference when peforming the nock-nock test with and without the bracing, especially for the top plate that is only 2cm MDF.
(because there will then be 1cm air + 1cm NN + seat foam on top of it)

Without the bracing the box was "singing", with the bracing it sound really dead!
So I think it looks promising. Looking forward to check it out after it's all glued tougheter...

[ThomasW]

Your bracing is fine. Those of us that are artists appreciate the free-form approach to hole cutting.....:T

[TEK]

The usual fill recommendations are 0.5-1.5 lbs/cu ft. So might as well start with 1lb/cu ft.

Fiberglass is best but would be a real pain given your construction. So use loose poly fill, tear it apart and fluff it up before sticking it in the box.

You'll want to fine tune the performance. So once it's up and running, experiment by adding in additional damping add in 4-6oz at a time. With each addition the sound should get a little tighter . When it no longer gets tighter, and the only inpact is a decreased output level, fall back and remove the last amount added.

Thanks a lot for the reply Thomas. It's very informative!

Let's see if I'm getting this right.
1 cu ft = ca 30 liters.
1 lbs = ca 0,5 kg
My box is approx 160 liter (when not including bracing, amp and element)
That should mean that your recommendation for my box would be to start out with approximate 3kg fill.

I'm planning to add the fill before I'm closing the box (gluing the top plate on).
Would it be a good ide/ok to fill all the sections along the edges, but leaving the center space empty.
I can then later on add more fill, but then mainly to the senter sections and most available sections.
Or should it be more evenly divided in the box?
Or more closly pressed against the walls of the box?

Is there any pictures around showing how a heavy filled sub normally would look inside?

Another question; when you start fine tuning the stuffing. Isn't it a good idea to do that after the element has been used a while, so that it has it's correct sound/behaviour before you fine adjust the stuffing?

[ThomasW]

Spread it around equally.

The only things that happen as a driver 'breaks-in' is that it plays a bit louder and a bit lower. This isn't related to tuning the box with damping.

[TEK]

OK, the work is in progress.
Getting closer to the goal every day.

Had a bit of a setback yesterday. The nicely fitted top plate was no longer so nicely fitted after I had glued the bottom, side walls and the matrix together.
Probably the pressure by the clamp + the gluing made some stuff align differently then when I fitted the top.

Got that sorted out and fixed yesterday, but did not get anything else done.

Today I got the box filled, glued the top on and prepared the connectors for the top seat plates.

The 3rd image shows the box ready to be filled. As you can see I have also added some extra damping to the sidewalls by adding some vibration absorbing plates. Based on the nock-nock test, it sounded like it actually did some kind of difference.
I have also used filler and gone over the corners of the box to ensure that it's closed

The 4th image is the box after I have filled it. It's not so fully filled as it looks. Some places there are only a bit fill, and then added a fill plate on top to get it divided out around the box.
I think I have used approx 2.5kilo of fill in the box.

The 1st image show the top after it has been glued onto the box.

The 2nd image shows one part of the connector to the seat plate.
I'm not able to describe how it will work here, so I'll post a describing image when it's connected and working.

Regards, Trond-Eirik

[TEK]

OK, then, finally some more progress.

A few days went by before I got the rest done, but now it's finally assembled

I had to give up opon the top mounting method. I was unable to get a good result. For now I will just have two detachable hatches on top of the sub, as the 4th and 5th image shows.
The hatch "fitting" is a temporary solution. I need something a lot better.

There are two issues going on.
1) Making the hatch fit nicly on top of the sub.
2) Make the hach strong enough and "flat" enought. There seems to be some twisting in the wood.
Any ideas for how this is best done is welcome

So, to the more important part, the SOUND...
NB: based on first/early impression, and I have yet not tuned the filling!

Whoooh... this is something else then my old Rel Storm III! :B

It adds a real fundation to the music and improves the listening expericen a lot! It's a totally different experience than with my previous sub.
When it comes to movies ;x(
It's almost unbelivable. It adds so mutch to movies that was'nt there before that it's incredable. Sometimes I'm a bit afraid that it will tare down my house :E It's really improtant that it's blended in nicly and that it's volume is not to loud, as it's really able to corrupt the sound if the sound level is not correctly matched.

I had no problem getting them to blend nicly with my front speakers
(B&W 803)
I also EQ'ed them to go flat down to 15HZ with no problem.

At the same time I discovered that there seems to be a issue in my system between DD tracks and DTS/Stereo tracks. When playing off DD tracks I get way to mutch bass output. It's not the case when I'm playing DTS tracks.
I have tested this by switching between DTS and DD and there is a huge difference in the bass level. Mutch more than what is resonable due to different mixing.
Example music:
Diana Krall - Live in Paris
Eagles - Hell Freezes Over
Steely Dan - Two Against Nature

[TEK]

After some more testing I find that there is a couple of other issues I'll have to look into.

It might seems like the sound is being compressed at high levels. There's less sound and more rumbling. I think this is due to to low distance between the floor and the sub.
The feets currently on is only 5cm, and was used as a temporary solution.

At the same time I have a 1cm edge between the bottom of the sub, making only 4cm room between the floor and the sub.

I think that having that 1cm edge is a mistake and that it have to go.
What do you folks think?


A issue that is a bit more difficult to do something about is the fact that even if it "looks like a thank", I do have quite a bit of vibration in the sub.
On some volume there is no problem feeling that the box vibrates.
However, there is also no problem feeling that my whole living room is vibrating, so that might not be an issue 8O

What is others experience on that?
Do you actually get your boxes to not vibrate at all, or is that a practical impossible mission when working with 18" elements and 1000W amp`s? :T

[TEK]

In use

[JonMarsh]

When you have a large flat baffle for the bass that close to the floor, it produces some slot loading effects which will alter the freuqency response. This can work to your benefit to counter roll off on the top due to VC impedance, but it would have to be "tuned" carefully. If you have measurement capability, I'd look at the frequency response say, about 6" from the edge of the cabinet and floor boundary on one side. Getting the sub as flat as possible in the upper range will help integration with your mains. Additionally, having too little space between baffle and floor may be impacting the LF output in the same way too small a port does- too high a volume velocity, which changes the effective radiation resistance seen by the cone as a function of playback level.

Something to think about.

Yes, when you have something this massive in "full song", it would be hard to expect no cabinet vibration unless you have a push-push balanced configuration with drivers mounted in opposite directions, and a very, very stout cabinet. Consider, for every action there is an equal and opposite reaction.

~Jon

[ThomasW]

Congratulations....... :T

If you think the sub is being compressed by the floor, turn the sub on it's side. If the output changes considerably you have your answer.

The other option is that is maybe overdamped (too much fiberglass)

[Bent]

Is the vibration a result of the cab flexing, or is the sub trying to "walk" - Thomas' recomendation to rotate the sub onto it's side will show if that is the case as well.

(hey, I just realized, I think that's what he meant...)

[TEK]

Thanks a lot for the input!
I have actually already tested putting it on the side.
(when it all comes to all, I do not have the spacing that you recommended in earlier discussions, so I kindof expected this to be an issue)

To my suprise, the change in effect was a bit less than what I had expected, but I have not done mutch testing so far. So it might be that it's overdamped as well. I'll do some more testing in the days to come, both regarding both issues.

I think I will try to get it a bit more over the floor anyway as that was the plan from the start.
And I'll problably get rid of the 1cm edged on the bottom anyway as well. The gap between the floor and the sub is no issue anyway, the only thing I now have to worry about is the total height of the box.

[TEK]

Is the vibration a result of the cab flexing, or is the sub trying to "walk" - Thomas' recomendation to rotate the sub onto it's side will show if that is the case as well.

(hey, I just realized, I think that's what he meant...)

It does not feels like it's "flexing", it's more a "shake" than flex kindof feeling.
But I'll think about that as well the next time I'll but it onto the side.
Hmm, BTW, as the floor is vibrating, so will the sub as long as it's not decoubled from the floor in any way. And I do not have any vibration damping feets...

But I also think that Jon has a point, there is a lot of power and energi around so it might not be practical avoidable.
(my next version will be using dual elements in oposite directions :twisted: )

But then I would probalbly have to reinforce my house first...

[TEK]

I herby officially joining the "I hate T-nuts club"! :evil:
Someone should start to manufacture some T-shirts with that text 8)

I was taking out the driver yesterday, and one of the T-Nuts was not possible to get loose. I had to drill out the head of the screw to get it loose. And as I have used high quality screws, that was easier said than done!
Well-well, now I have for sure learned it:
1) Always glue the T-Nuts in place!
2) Be SURE that you hit correctly when scruwing into them

Enough said about that.

Yesterday I finally got around to remove the edges around the bottom, remove some filling and make the feets a bit longer.
First impression is that it helped a lot. The sound is more defined and I do not get the impression that it's "compressed". I think all effords helped, but I think that the main issue was that I was overdamping the box.
(I removed 2 full plastic bags of stuffing) ops:

In the time to come I will do some more testing to check out the effect of adding or removing daming material.

Just before I did this I watched the last of the LOTR movies. Phu!
This baby is giving out massage as well as sound :T
And after the last modifications, I think it's REALLY starting to deliver the goods when it comes to music as well :T

It's really a gift to have this sub in my setup.
Now I just have to get some speed on that leather.
But hay, no one has ever said this was a fast project :W

[gimpy]

Hey, nice job, TEK. Sounds like you've done a really nice job. I, too, am not a fan of the t-nuts. I have one that has come completely loose in one of my speakers. The whole screw just spins, but does not loosen or tighten. I keep hoping that one "loose screw" is not affecting the sound of the speaker too much. I have since started using "hurricane" nuts from P.E. I have not tried to take a screw out from one, but they seem to work really nice, so far. I have heard others say good things about them, too. I think MDF is just too hard for the t-nut prongs to work/dig in properly.

good luck and good listening.
Frank

[TEK]

Whooa...
Had to be without my almost brand new DIY sub during this weekend.
Tried to play some music :cry:
Oh man. I'm an bass addic! I really did not think I would become one, but once I have had real bass in my system I will never be able to live without it again

The I was without sub this weekend because I delivered it to a local leather maker to get it fixed up.
Now I have got it back, better than ever!
Pictures below!



The fot of the sub has "built in" vibration dampers. The weight of the sub + loosly tightned screws should cause the whole sub to be connected to the floor only trough these vibration dampers.
(designed for washing machines)



Doing it this way makes it mutch easier to move the sub around without having to worry about the dampers falling off.



Just had to include the element one more time before putting it in again.
This thing is big and heavy!



The element and amp is all in place.
As you can see have I painted the bottom plate black. No one is ever going to see it (except you folks for course), however it feels good to know that it's looking kindof decent. Makes the total impression more "pro"

The box itself is about 58kg, the driver is 19kg and the amp is 14kg, adding up to a total weight of approx 90 kg! Belive me, it's heavy!

[TEK]

Some more pictures from my setup:

There is NO WAY I would have been allowed to have a box of this size here if I had not been able to design it so that it's kindof merges in with the rest of the room/funitures.
Even my wife likes it :T



Preparing for some serious testing!



The new family member in all it's glory!



The complete setup, image 1



The complete setup, image 2

Whoo, would I have loved to have a couple of meters more between the speakers and the listening position :roll: But you just have to make the best out of what you got! 8)

[Dennis H]

Trond-Eirik, that looks absolutely beautiful. Nice job combining the sub function with a good-looking piece of furniture.

[---k---]

Wow, very impressive. I would have never thought about covering a sub in leather, but that looks great! How much did having the leather done run you?


BTW, this would make another great addition to the DIY Subwoofer Showcase.

[JonMarsh]

Some more pictures from my setup:

There is NO WAY I would have been allowed to have a box of this size here if I had not been able to design it so that it's kindof merges in with the rest of the room/funitures.
Even my wife likes it :T



Preparing for some serious testing!



The new family member in all it's glory!



The complete setup, image 1



The complete setup, image 2

Whoo, would I have loved to have a couple of meters more between the speakers and the listening position :roll: But you just have to make the best out of what you got! 8)

Isn't THAT the truth!?! Thanks for sharing the pictures- hope it helps some others out of a "tight situation"!

Pretty impressive, actually, hiding it right out in plain sight!

~Jon

[TEK]

How much did having the leather done run you?

Way to much ops:

But now in the end, who keep track :

The leather used is the exact same as used on the chairs, and is bought from Ekornes (trough a regular funiture shop). The problem with this is that to be sure you have good enough areas on the leather, you have to buy twice as mutch as you need :roll:
In addition I'm no good with laether, so I had to have someone else to do the work. The foam used under the lether as well as on top to make it comfortable to sit on is also quite expensive.
The total cost of the leather, the foam and the work runs up to approx $600.
However, I do have quite a bit of leather left for other, smaller projects

If you could use another type of leather it would have been cheaper.
But I do not think that I would have been able to have this done below $300 to $400.

[---k---]

Wow, that is a lot for the leather, but I think it really is worth it. I've learned that I can't put a price on my wife's happyness - whatever it costs!

Really, it looks great, and here you would pay almost that much for high quality leather ottoman at a furniture store.

[TEK]

Wow, that is a lot for the leather, but I think it really is worth it. I've learned that I can't put a price on my wife's happyness - whatever it costs!

Really, it looks great, and here you would pay almost that much for high quality leather ottoman at a furniture store.

The price for the Ekornes dobbeltpallet with the same leather is approx $900.

If I were to do this again I would have tought very, very, very long and hard about bying that and modify it instead. Or bying it and just move the leather over to a new box.

I did check prices up front, however I did not know that I had to calculate 6 m2 of leather instead of 3.5 m2 as I tought.
My initial estimate did also not include the cost of the extra materials needed. Like sitting foam on top and padding all the way around.

I blow my budged bigtime...
But, what the heck, the wife is happy :T

That's DIY :rofl: