DOWN UNDER SUB (Off Topic)
by leifchristensen 
, Tuesday, June 26, 2007, 11:51 (6149 days ago)
edited by unknown, Tuesday, June 26, 2007, 13:39
[img]images/uploaded/image303.jpg[/img]
Hello folks
Here´s my latest creation in the shape of a JBL2245H based Elliot sound eq´d closed 110 liter sub project.
Based on Rod Elliots project 48 with sub playing under box resonnance.
X/O @ approx 35hZ and driven by bridged Coldamps with 800WATT@8 ohms.
Not too difficult to integrate with Berts marvelous 15 inch "twintowers".
AND it sure adds another dimension.
Best
Leif
Oslo
DOWN UNDER SUB
by JAM , Tuesday, June 26, 2007, 12:35 (6149 days ago) @ leifchristensen
Congratulations are in order! You just set a new WORLD record in inverted WAF!
Seriously, this is very interesting if it works; additional real low bass with physical dimensions to live with. I reckon you have one sub for each channel? Sub's not slowing down the obvious fast impact of the twin towers?
Is the difference with/without this sub noticeable only on bass-oriented music or is it an improvement regardless of music type played?
Passive or active X/O?
DOWN UNDER SUB
by leifchristensen , Tuesday, June 26, 2007, 13:04 (6149 days ago) @ JAM
edited by unknown, Tuesday, June 26, 2007, 14:07
Hello
As mentioned above it´s based on Elliot Sound´s project 48 which tells that a bass element in a "too small" closed enclosure forced to operate below box resonnance with operate in a vibration free environment at the cost of rolloff at 12 db/octave.
By using to integraters (TL072) with an infinite gain at 0 hz and 0 gain at infinite freq. at the rate of 6 db/octave each, the roloff will be compensated for....at the cost of serious power needs!
however power come cheap these days compared to real estate,so the choice is for me fairly obvious.
It all works beatifully and certainly adds somthing of a new dimension even on e.g Eva Cassidy on solo guitar.
Can also be built as a cube with smaller drivers on all sides to kep the size down!
Most recommended.
Best
Leif
DOWN UNDER SUB
by PeterSt. 
, Netherlands, Tuesday, June 26, 2007, 12:45 (6149 days ago) @ leifchristensen
That looks quite impressive Leif !
How low does it go ?
But now this :
I see you have quite some LPs, and I'd think you use them sometimes;
1. Doesn't that go wrong with sub-low and reflecting back on the turntable ?
2. I imagine that the rummble from the turntable is in the sub-low area itself ...
?
Peter
DOWN UNDER SUB
by leifchristensen , Tuesday, June 26, 2007, 13:11 (6149 days ago) @ PeterSt.
Hello P
My Basis Ovation from 1991 is put in a 19 mm MDF close to airtight box with a custom 10mm,17kg acrylic lid on it.Had to use small pneumatic shock absorbers
to ease the weight of the lid.
It´s all on top of a sand filled VPI stand spiked to the floor.
The box rests on pulsar points and so does the player itself.
Undamped Airtangent Reference with Lyra Titan "i".
FULL THROTTLE (which is fairly LOUUD!!) and no problem
best
Leif
DOWN UNDER SUB
Hi Leif
Halleuja 
Based on Rod Elliots project 48 with sub playing under box resonnance.
I have read nothing about Elliots theories, but knows this:
Actually from a theoretical point of view all drivers sounds best under the box resonance. Also if we talk tweeters or whatever load of a driver.
How come? Easy...under the chamber res. the voice coil acts like a pure Ohm resistor free from "dynamical" parasites such as capacitance and inductance.
Even passive filter components will act as they are supposed to when used under the res. point.
The eventual distortion problem can be solved by just having plenty of displacement surface for the purpose.
Must sound fantastic I think.
GC
DOWN UNDER SUB
by leifchristensen , Tuesday, June 26, 2007, 21:19 (6149 days ago) @ GC
look here:
http://sound.westhost.com/project48.htm
original thoughts by linkwitz
best
Leif
DOWN UNDER SUB
look here:
http://sound.westhost.com/project48.htm
original thoughts by linkwitz
best
Leif
He he Leif...
Yeah I know that storries and theories. I'm though surpriced they adressed only the tweak of equalizing, as the matter of fact, working with the range lower than the Fr has much more to offer. You can take it further.
Remember what a resonator is: An uncontrolled random to electronics (read components) try to control its randomity. No way it does it except the resonating system is silent = 0 db music = no moving mass at all. And it is correct to to it under the Fr.
Now what I learn from the article is about #compensating# the loss of amplitude by doing so, but but but...
Read this:
http://www.pvconsultants.com/audio/eq/linktran.htm
and a layout of it...(done right):
![[image]](images/uploaded/image40.gif)
However it is the L-G approach allows you to control the Q of the speaker taking the room into consideration as well and aim at a total Q control including the room as well.
If you want to mail torben.k@email.dk he will elaborate much more. I guess?
Now having said all this, there is one set-back about it. Woofers which are loaded unsymetrically front side/back side by the fact it has a most uneven air impendance in front of it and in back og it, will have a hard life. If we record the diaphragmes behaviour at those stress points we see a horror. If we see it, don't we hear it as well?
No driver gets a big tourque by means amplifier control. No amplifier can add Tesla and BL into it.
My thinking is to alowe the driver to be itself and leave it as un-enclosured as possible -> back load imp = front load imp. equation.
Said in another way 1=1. Music=music.
I am not spitting on your acheivements..on the contrary. Steen Duelund who implemented battery operated linkwitz greiner circuits before amping in his constructions came far..and more far than Elliot did.
Explore the theory of Q-controlled room response in the lows by Google. There are much to find. there.
My point is to acheive bass by: Nothing replaces cubic inches = free drivers with m2's of mowing mass and tons of tourque by magnets surrounding voice coils.
You can go that way as well and acheive far lower distortion = resolution.
It is after all not possible to completely control a room by means of one 15" or 12" driver/cab/electronic EQ. It's a shortcut.
We need a room to keep winter cold and summer heat away from us. Give us lay and shelter from rain and thunder.
No one ever thought to make the 6 walls in a room of pure bass driver units?
Well maybe too far out, but the ideal it is.
GC 
DOWN UNDER SUB
by Bert , Tuesday, June 26, 2007, 22:25 (6149 days ago) @ GC
No one ever thought to make the 6 walls in a room of pure bass driver
units?
One wall with mirrored driver yes...soon!
Hehe...
http://forum.bd-design.nl/index.php?id=13747
Shaking baby and hardly cone movement? Jeezzz..
Bert
--
BD-Design - Only the Best!
DOWN UNDER SUB
by leifchristensen , Tuesday, June 26, 2007, 23:12 (6149 days ago) @ GC
hello G
I´m impressed ; this is one of your more impessive contributions ever.
Keep up the good research.I certainly will.
Thxs
Leif
DOWN UNDER SUB
hello G
I´m impressed ; this is one of your more impessive contributions ever.
Keep up the good research.I certainly will.
Thxs
Leif
Hej Leif my previous neighbour.
If so, don't trigger anything as I just have to elaborate all. I would like to have the time to. Not to spit on anyones systems and approaches. I'm not born to do that.
I will however write a memorandom on speakers one day. Not on a forum which keep me occupied 24 hours a day...but just as statement.
Leif. Your system is impressive and it reminds me of a lot I did similar to you. No regrets here.
The SWING MKII will, if Bert allowes it, do the job to the utmost. Except advantageing the lower FR tricks which we (you and I) can start to learn people about.
The real offer the L-G do is to make the impossible possible..allmost. Low clean and fair sub-bass from a very small cab.
Steen did it on his small 6 1/2" bass drivers two and three ways speakers. Impressive it ever was.
Now..just test your perceived WAF and build a wall like Bert is doing. He is doing it 1/6th of the optimum. But soon his studio will maybe be filled with 200 bass drivers?
Let's see if we have devotees here on the forum. It takes some bucks to ultimate.
Leif ...still I agree with you. There is a real concert hall to appear in your room following your DOWN UNDER SUB.
Now Google your self to the best likes of acheiving it. Then we can share the whole thing that were forgotten about here.
GC :wink:
DOWN UNDER SUB
by Bert , Tuesday, June 26, 2007, 23:15 (6149 days ago) @ leifchristensen
Nice tower you have there now Leif, thanks for the picture. How many people were needed to get the twin-tower on top your subs?
Hope you didn't hurt anything...
Bert
--
BD-Design - Only the Best!
DOWN UNDER SUB
by leifchristensen , Wednesday, June 27, 2007, 08:38 (6148 days ago) @ Bert
JUST 2 VIKINGS
best
Leif