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Old 25th March 2012, 02:44 AM   #11
mdocod is offline mdocod  United States
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Titanic MKIII 10" in tapped horn maybe?

It comes close to the 95dB sensitivity requirement, has a usable and effectively flat 30-80hz bandwidth, box size isn't too terrible huge for a horn either (under 200l).

I honestly don't know enough about horns to say whether what I am proposing is a good idea or not, but it is an idea Get more opinions.

I'm thinking a pair of such units would probably be more at home as bass bins in a sound reinforcement system, but hey, they could double as house deconstruction duty.

Regards,
Eric

[PS: attachment #5 below is peak particle velocity @40V]
Attached Images
File Type: png Selection_048.png (11.6 KB, 162 views)
File Type: png Selection_049.png (4.8 KB, 163 views)
File Type: png Selection_050.png (14.5 KB, 163 views)
File Type: png Selection_051.png (13.1 KB, 161 views)
File Type: png Selection_052.png (7.7 KB, 160 views)
File Type: png Selection_053.png (3.8 KB, 22 views)

Last edited by mdocod; 25th March 2012 at 03:02 AM.
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Old 13th April 2012, 02:44 PM   #12
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Dangus:
Tactile inducers are interesting, but it would only be as an addition/supplement.

mdocod:
That is not really interesting at all, the box is significantly larger than what i posted, the frequency response is poorer (from my point of view), it will be difficult to place the box properly in-room, i am trying to get bass in ear height.

I have decided on a solution, will post later tonight or tomorrow.
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Old 13th April 2012, 03:35 PM   #13
badman is offline badman  United States
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Quote:
Originally Posted by KaffiMann View Post
mdocod:
That is not really interesting at all, the box is significantly larger than what i posted, the frequency response is poorer (from my point of view), it will be difficult to place the box properly in-room, i am trying to get bass in ear height.

I have decided on a solution, will post later tonight or tomorrow.
Nice attitude

His solution gets 3dB more at 30Hz than yours. That's a lot.

May not fit your needs but no need to be rude about it.
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Old 13th April 2012, 04:18 PM   #14
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@badman & mdocod

Sorry about that, it was not my intention to be rude.

Let me refine my reply:
I do not like the dips and peaks on the fr response, i would like to avoid using eq whenever i can. And the design uses a 4 ohm driver, that is twice the power at 2,83V as i assume this was the voltage used for calculation. The design i have calculated at home is only 90db/2,83V BUT the frequency response is completely flat from 28 to almost 120hz. Making it much easier to use with small good quality fullrange drivers, and it will therefore be my choice in the matter.

Please note that allthough if mdocod used a different voltage the designs i posted are nearly half the size and have flatter and easier frequency response to work with.

Sorry again for being/seeming rude.
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Old 13th April 2012, 08:29 PM   #15
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Sorry about the bump!

As promised, I am posting the design I have decided on.
The box will be 38*37*115 cm with 2,4 cm material thickness, choice of material will most likely be baltic birch ply, 12mm doubled up. Total volume of box including material is 162L. Changing to 18mm single would reduce the volume a lot in theory, but in reality the difference is at most 1,5cm in any direction.

So to sum it all up, i have decided to trade low end for wider frequency extension, and spl for flat and even response.

Thanks to Bjorno for coming up with this, and tb46 for reminding me.

It will be probably another 2-3 months until the project is finished, please have patience.


Edit:
The reason for choosing this driver is cost and local availability combined with quality and required properties for this type of enclosures.
It costs about 100$ a piece here, and i do not have to pay shipping or anything else.
Attached Images
File Type: png T-TQWT - Beyma 12BR70.png (51.1 KB, 55 views)

Last edited by KaffiMann; 13th April 2012 at 08:35 PM.
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Old 15th April 2012, 01:38 AM   #16
bjorno is offline bjorno  Sweden
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Quote:
KaffiMan:..Sorry about the bump!..
Hi KaffiMann,

I'm bumping too..Submitting a simulation using the preffered Beyma-12BR70 drivers.
I believe the OD_T-QWP corner placed would be a good choice if combined with FR drivers:

b
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File Type: jpg Beyma-12BR70_T-TQWT_OD-corner-T-TQWT.JPG (463.1 KB, 64 views)
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Old 16th April 2012, 11:47 AM   #17
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Those are very nice looking.

But i have some questions:
How can you get L34 at less than radius of the driver? If you just made a hole more directly in front of the driver instead of at the end of the box, would you not get any side effects from the cavity, or is part of the driver out in the open? How can this be calculated? And what about material thickness, should i not account for it?

I am also wondering about the xmax when using hornresp.
In the TH i built last year the membranes have never been moving more than maybe 2-3mm total (both ways combined) at levels that should give 6-8mm excursion (enormously present bass, very physical, seems correct), and on the Tangband "horn" i made the year before (flat to under 25hz), the membranes of the drivers are moving no more than 4mm total (both ways combined) when the predicted movement should be far higher,around 10mm.

The response seems just fine from both designs, it's just that the drivers seem to use far less excursion than they simulated in hornresp. This is also the case when using 5hz, they are moving more, but less than half of what my simulations gave, and still well within xmax at high levels, even though i should be exceeding it by a few times.

So either i did something seriously wrong when building but still got the same frequency response, or hornresp have big trouble calculating excursion for tapped designs.

So on this next project i will be aiming for xmax *2 on the simulation on my desired maximum power rating of 28,3V in 8ohm, i assume i will (hopefully) still be under the xmax of the driver, and if i am wrong then i just have a good excuse to try something new and improved yet again. :-)

Last edited by KaffiMann; 16th April 2012 at 11:58 AM. Reason: taypåo
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Old 17th April 2012, 05:50 PM   #18
cbdb is offline cbdb  Canada
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Nice pictures but thats not going to show you what it will sound like. At those low freq. your room is as important as the sub enclosure (the room becomes an enclosure).Thats why I dont think you can make a directional sub in a small room. Try a tuned bass trap (40hz? if that seems to be the problem) in a position where the 40hz is loudest. Learn about room modes.
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Old 21st April 2012, 01:57 PM   #19
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cbdb:

That is of course also relevant, but i still think the first step is getting the sub away from the corner (and concrete floor), which cannot be done easily with my current sub.
The 40hz follows the concrete wall behind my couch, which is the wall parallel to the one where my stereo is. in the middle of the room there is almost nothing.

I think that if the aperture of my th was designed to be about 70-160cm high from the floor this problem would not occur to the same extent. The corner can probably be seen as a secondary problem at that, but corners, as previously stated in this thread and others, couple more directly with room modes, I will try to evade corners and floor in order to start my battle with this problem.

This is the main reason i want to make 2 new subs at specific heights, to serve as stands for a small 90dB or so fullrange (not part of the original goal), and reduce room coupling.

Last edited by KaffiMann; 21st April 2012 at 02:00 PM. Reason: typo
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Old 21st April 2012, 11:33 PM   #20
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Quote:
Originally Posted by KaffiMann View Post
cbdb:

That is of course also relevant, but i still think the first step is getting the sub away from the corner (and concrete floor), which cannot be done easily with my current sub.
The 40hz follows the concrete wall behind my couch, which is the wall parallel to the one where my stereo is. in the middle of the room there is almost nothing.

I think that if the aperture of my th was designed to be about 70-160cm high from the floor this problem would not occur to the same extent. The corner can probably be seen as a secondary problem at that, but corners, as previously stated in this thread and others, couple more directly with room modes, I will try to evade corners and floor in order to start my battle with this problem.

This is the main reason i want to make 2 new subs at specific heights, to serve as stands for a small 90dB or so fullrange (not part of the original goal), and reduce room coupling.
Nice to see you have your' head wrapped around this very nicely.

Cheers,
revb
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