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Old 22nd April 2012, 03:41 AM   #21
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Quote:
Originally Posted by revboden View Post
Nice to see you have your' head wrapped around this very nicely.

Cheers,
revb
I am probably not that good at formulating my thoughts properly, but there probably is some sort of process going on somewhere, most likely my gut, maybe not that accurate, but it's all I have.

I am modeling a lot of different designs with a lot of different drivers daily, but it is hard to really find something that is a better compromise than the box I stated as my final decision in post #15

After all, everything is a compromise I always say. Increasing size of the box will of course help on bandwidth in some ways, but then there may be other issues one has to deal with.

Here is another solution that is interesting, the problem is that the depth of the box will be just over my "pain limit", and the other is that the driver will sag over time with the box standing up. Bandwidth is impressive nevertheless. Driver placed at the very beginning of T-TQWT. Almost 2,5 octave usable bandwidth or so, I do not like the hammock, but it's not too bad.

Edit:
I am expecting maybe 1-2 dB possible loss (worst case) from placement compared to 2pi simulations no matter what I end up with.
Attached Images
File Type: png T-TQWT - Beyma 12BR70v2.png (61.1 KB, 137 views)

Last edited by KaffiMann; 22nd April 2012 at 03:43 AM.
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Old 22nd April 2012, 11:14 PM   #22
bjorno is offline bjorno  Sweden
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KaffiMann,

Have a look at the following simulations:

b
Attached Images
File Type: jpg 1_Beyma-12BR70_T-TQWT_OD-corner-T-TQWT_versus_TTQWT.JPG (454.3 KB, 125 views)
File Type: jpg 2_OD_T-TQWT_versus_T-TQWT.jpg (448.3 KB, 123 views)
File Type: jpg 3_Beyma-12BR70_T-TQWT_OD-corner.JPG (151.2 KB, 118 views)
File Type: jpg 4_Beyma-12BR70_OD-TL.JPG (793.6 KB, 117 views)
File Type: jpg 5_Beyma_12BR70E_ML_TL.JPG (348.0 KB, 25 views)
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Old 23rd April 2012, 08:07 PM   #23
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Bjorno:

Thanks for all the work, but that design i posted last is not even up for consideration. As i mentioned it's: a) too deep b) the driver will sag over time, making it another deal breaker for me.

Regarding the possible/not possible part, what i did was take the very beginning of the tqwt, before any sort of tapering has occured, and put the driver there, on a 33x33cm board (1089cm2), big enough for mounting the driver.

Which part of it is not possible?

Sure, i am not even remotely interested in it, but why is it not possible? Is it because of the way hornresp simulates TH? It is still a tapped design, just a different one.

I really appreciate the help, and the frequency response you get out of those double fold simulations are very good and promising. However looking at the box dimensions you are basing it on, it seems like it will be a problem with depth, It will be difficult to have a box depth greater than 40cm here (materials included).

I am still considering the solution from post#15 for simplicity and ease of build as well as size.

A lot of the music I am listening to have extension down to 25Hz, in an ideal world it would be nice to have flat response down to this point. But given size restrictions and room modes it seems like a near impossible task. So again, I am forced to compromise.
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Old 8th September 2012, 11:36 AM   #24
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This is taking forever to finish. The kids are having a nap, then we're going over to some friends to eat whole roasted suckling pig, Bali style.

Here is the hornresp of the thingy's I am building, and a photo of the uglies. As well as a close up of the Beyma 12BR70, very much value for the money, I think it is magnesium cast frame? Not sure, it is a very light and stiff material anyway. Also a picture of one of the amp channels assembled including SMPS, and both the boxes that the two amp channels wil go into, not finished.

I have tried firing up one of these, and the two of them may end up beating my big TH into pulp, at least under these difficult room conditions. I gave it hell and it rattles the room evenly down to 23-24hz where it gives up fast after that.
Attached Images
File Type: png T-TQWT - Beyma 12BR70 Final.png (70.9 KB, 38 views)
File Type: jpg SL376759.jpg (49.6 KB, 55 views)
File Type: jpg SL376761.jpg (49.2 KB, 49 views)
File Type: jpg SL376762.jpg (57.6 KB, 38 views)
File Type: jpg SL376763.jpg (63.8 KB, 34 views)
File Type: jpg SL376764.jpg (73.4 KB, 38 views)
File Type: jpg SL376765.jpg (66.8 KB, 34 views)
File Type: jpg SL376766.jpg (47.9 KB, 36 views)
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Old 8th September 2012, 12:45 PM   #25
DrDyna is offline DrDyna  United States
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I like the use of angled brackets, you've given me an idea for the THs I'm building this weekend
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Old 9th September 2012, 12:44 PM   #26
tvrgeek is offline tvrgeek  United States
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Has it come to anyone's attention that pretty much by definition low frequencies are omni-directional? Localized bass would require something like ultrasonic carrier modulation and you could never move your head. Just physics folks.

There is no good or bad place to put a sub. Each reacts with the room differently. I can make good use of a corner, but I design the sub to be in a corner.

There are only two ways to smooth out bass. Move outside where you have only one boundary ( ground) or learn about room tuning and bass traps. The first is easy but not fun in the rain. The second is very hard. The one thing that WILL NOT WORK, is to expect the next magic driver or box to solve your problems. Sorry, physics again.
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Old 9th September 2012, 07:33 PM   #27
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Quote:
Originally Posted by tvrgeek View Post
Has it come to anyone's attention that pretty much by definition low frequencies are omni-directional? Localized bass would require something like ultrasonic carrier modulation and you could never move your head. Just physics folks.

There is no good or bad place to put a sub. Each reacts with the room differently. I can make good use of a corner, but I design the sub to be in a corner.

There are only two ways to smooth out bass. Move outside where you have only one boundary ( ground) or learn about room tuning and bass traps. The first is easy but not fun in the rain. The second is very hard. The one thing that WILL NOT WORK, is to expect the next magic driver or box to solve your problems. Sorry, physics again.
Your points are valid, the low frequency sounds are perceived by humans as omni directional. We have no idea, or way of distinguishing where the sound originates.

However, I was/am certain that where a subwoofer points or is placed and what is in that direction or part of the room (walls, chimneys, air ducts, doors and such) can have a great impact on the further path of the sound, how it will behave and if certain parts of the frequency spectrum will weaken or increase in amplitude as a side effect from this. We all know that a corner causes the low frequencies to couple more directly with room modes (both good and bad), just as stated earlier in this thread and others (again).

Again, I am stating that my effort to battle this will be to move the aperture of the subs away from floor, walls and ceiling, to reduce coupling with room modes. The short tests I have conducted so far tells me I have succeeded to a great extent, I have a minor boost at around 80hz to be concerned about, but response is far more even and controllable than when using the TH firing straight into a very troublesome corner (air duct and poorly sealed balcony door, almost a wall full of windows).

This project is already a great success, and I am not even finished yet.

Edit:
Will a bass horn magically provide even bass response no matter where you place/point it? If so, it would make my diy audio life a lot easier. I know it works on flat ground outside, but it does NOT work in my room.

Edit2:
The apertures from these T-TQWT's will point directly at listening position, not at wall, not at the floor, not into a corner, I do not want to rely on reflections in this room, it does not work.

Last edited by KaffiMann; 9th September 2012 at 07:59 PM.
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Old 12th September 2012, 04:42 PM   #28
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Quote:
Originally Posted by KaffiMann View Post
Will a bass horn magically provide even bass response no matter where you place/point it?

Edit2:
The apertures from these T-TQWT's will point directly at listening position, not at wall, not at the floor, not into a corner, I do not want to rely on reflections in this room, it does not work.
A bass horn is more directional in the upper range than a direct radiator, so has less even response and is less forgiving regarding where it is pointed.

Unless you have a very large room, the low frequency you hear at any point in the room will have a large reflected content.
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Old 12th September 2012, 06:53 PM   #29
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Originally Posted by weltersys View Post
A bass horn is more directional in the upper range than a direct radiator, so has less even response and is less forgiving regarding where it is pointed.

Unless you have a very large room, the low frequency you hear at any point in the room will have a large reflected content.


The difference is where the first room reflections originate.

I have no good explanation for it, other than with the TH, I had mainly 40hz and nulls although it was designed 0db at 80hz evenly down to -5db at 19hz, works well in other rooms. Now I have a very even response, and a minor boost at 80hz.

Last edited by KaffiMann; 12th September 2012 at 07:03 PM.
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Old 12th September 2012, 07:33 PM   #30
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Originally Posted by mdocod View Post
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]
Very interesting, I'll have to model this too. Thanks.
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