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i understand that this is goofy, but stick with me...good content coming...i just need to get to my fifth post to post it.
 

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here is a non-tapped horn that i worked up in hornresp for the updated shiva.

it is 10 cubic feet and improves the efficiency of the shiva by about 10db, which is huge. i'm not interested in the contest or getting free drivers, just wanted to kick in a design. [oh, i also post on avs under callsign LTD02]

 

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here is a non-tapped horn that i worked up in hornresp for the updated shiva.

it is 10 cubic feet and improves the efficiency of the shiva by about 10db, which is huge. i'm not interested in the contest or getting free drivers, just wanted to kick in a design. [oh, i also post on avs under callsign LTD02]


Yea... throw an inductor on that and it starts to look good. A lot of people get freaked out by the out of bandwidth wiggle but we are focusing on the <70-80Hz stuff and the upper frequency climb is easy to deal with.

Kevin Haskins
Exodus Audio
 

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here is a non-tapped horn that i worked up in hornresp for the updated shiva.

it is 10 cubic feet and improves the efficiency of the shiva by about 10db, which is huge. i'm not interested in the contest or getting free drivers, just wanted to kick in a design. [oh, i also post on avs under callsign LTD02]


Yea... throw an inductor on that and it starts to look good. A lot of people get freaked out by the out of bandwidth wiggle but we are focusing on the <70-80Hz stuff and the upper frequency climb is easy to deal with. In room with proper boundary loading you get response lower but it would have to be built and measured.

Kevin Haskins
Exodus Audio
 

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i think it looks fantastic as it is kevin. those bumps and wiggles seem to go away when the horn placed in a room and measured, but most folks probably don't know that. if you put a regression line through the frequency response, there is only +/-2db of 'wiggle' in the model from 15-80hz. that is much less than many other designs, even the danley dts-10, and will be dwarfed by room effects. i was very surprised at how well the shiva could do in a 10 cubic foot horn, which is relatively small.

hopefully, others will beat my design. come on guys...bring it on. :)
 

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i think it looks fantastic as it is kevin. those bumps and wiggles seem to go away when the horn placed in a room and measured, but most folks probably don't know that. if you put a regression line through the frequency response, there is only +/-2db of 'wiggle' in the model from 15-80hz. that is much less than many other designs, even the danley dts-10, and will be dwarfed by room effects. i was very surprised at how well the shiva could do in a 10 cubic foot horn, which is relatively small.

hopefully, others will beat my design. come on guys...bring it on. :)
Yea... it looks great. I'm just talking about the 10dB climb from 20Hz to 100Hz. That is trivial to work with but not what many people are used to looking at when modeling traditional boxes. I bet an in-room measurement would get down to the 10-12Hz range.

That is a ton of output... give us the napkin drawing next. ;-)

Kevin Haskins
Exodus Audio
 

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This is set up for a tempest-x but could be narrowed a little to fit a shiva. I'm designing it as a option to an IB install. It will live behind our couch and fire directly into a corner. Hopefully it has a shot at .5 or 1 pi space.

I'm still toying with the specs on s1/2 being smaller thanks to some info from lilmike over at avs to help smooth out the response.

Here are the parameters, response and a napkin drawing :bigsmile:

horn response.jpg

horn info.jpg

Tempest Horn.jpg
 

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i think it looks fantastic as it is kevin.
I agree. Your model looks a titch better than anything I can come up with. The learning curve on hornresp is a little steep.

Kevin. What exactly does an inductor do here?

Also, what sort of compression ratio do you think we can safely subject this driver to?
 

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"Your model looks a titch better than anything I can come up with."

hi fredk, that just seems to be the nature of modelling in hornresp. sometimes, i have farted around for an hour or more and then someone else jumps in with a model that is vastly superior with 2 minutes work. at this point, it seems that there is a little bit of luck at work in arriving at an optimal horn design for a driver. hopefully, somebody will be luckier than either of us and propose a whopper of a horn design for the shiva driver.
 

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"Hate to point this out, but it's not a TH."

a9x, sorry if what i proposed was not a tapped horn, as spec'd in your op. i didn't mean to muck up your thread. i was just trying to show an honest alternative.
 

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Discussion Starter #53
"Hate to point this out, but it's not a TH."

a9x, sorry if what i proposed was not a tapped horn, as spec'd in your op. i didn't mean to muck up your thread. i was just trying to show an honest alternative.
No worries, I'm always happy to see alternatives. I just didn't want anyone else to think it was a TH.

After mocking up the one in the OP with cardboard and tape, I don't think I'll be using them myself, they're just too big.
 

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the horn that i suggested is ten cubic feet, which works out to about:

2.5 feet high, 3.33 wide, 1.33 deep.

that's not too big is it?
 

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Thanks for trying to make me feel better publius. I just don't have a clue what I'm doing yet and there are a whole lot more variables to play with here than other sub designs. I'm still struggling to see the relationships between various parameters. Its still fun though.


After mocking up the one in the OP with cardboard and tape, I don't think I'll be using them myself, they're just too big.
That will be the case for most people. I have a lot of lattitude and still, most of what I have seen that reaches low is larger than I am willing to accomodate.
 

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Yay - the pictures are here!!!

Figured I'd throw my hat in the ring. :D

While it is not a perfect driver for use in a tapped horn, the Shiva X2 is no slouch.



Cabinet is about 400 liters net, impulse response looks fairly well damped, phase is pretty good.

2.83V 2pi SPL


Impulse


Phase


SPL is limited by xmax to around 115 @ 500 W, 2pi, so it should do reference levels in room. I'd suggest a highpass near 14 Hz if you listen loud. There is no such thing as a perfect corner is my house (best I can get is 1pi), so add 5 dB - you'll probably get near 120 @ 1m in room, probably 110-115 at your couch before running out of xmax. I am not sure what the mechanical limit is, so I stopped here.

500 W Excursion


Experience building and measuring several tapped horns tells me that the sharp spike at 56 Hz will either be greatly attenuated or not present at all in the real world. I have also learned that poly batting placed appropriately will significantly attenuate the 10 dB step in response above 70 Hz, but the best placement is arrived at through trial and measurements.

With appropriately placed batting, and a proper crossover frequency and slope, this should have a usable bandwidth of 15 to 100 Hz.

I'm working on a folding pattern, I have several in mind. My Sketchup abilities are pretty light compared to some of these guys.

Here is my general idea for a fold:


Folded like this, the cabinet will be approximately 4.5' high, 2.5' wide, and 1.5' deep.

I have the tools to construct this and measure the results reasonably accurately.
 

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It is just speculation on my part. You won't know how low it will go in-room unless you specify placement and actually measure it with the boundaries, corners etc...

I have never managed better than 1pi (+6 dB), even in a corner, but I have an old house. My in-room response is always uglier than a groundplane measurement

Once again I don't know. It is just a simulation and I don't know how accurate HR models the actual results. You might be able to acoustically damp some of those ripples or they may be swamped by the room issues. The bottom line is you would need to build and measure.

That is the only way to know. The ones I have built and measured typically do not show the sharp spikes, but do show the rising response. Typically, the ripples in the passband are there, and the magnitude is similar, as are the peaks and dips, but at a lesser magnitude. If you're accurate with your modeling building, and measuring, the frequencies are usually really close to the predicted values. Properly placed damping material works wonders.

Sure... there are situations that are right for any tool. That is the nature of the beast and every solution isn't going to be right for every person/build. It depends on what your build skills are, where your size constraints are and what you feel comfortable building. This goes for any sub, horn or otherwise but the larger you build it and the more dependent its output is upon room boundaries, the less flexibility you will have in maximizing the listening position FR. That is just the nature of the beast so you have to think through the complete solution.

No silver bullets here, just more math and physics, and a whole heap of compromises. The right driver in the right tapped horn makes an amazing subwoofer as the effects of these compromises are minimized. I am still on a quest for the right driver....

Kevin Haskins
Exodus Audio
Comments inserted above in bold
 

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For under 300L, a front loaded horn is better at 20hz than at 15Hz:



2Pi, 2.83V in, Offset Driver front loaded horn using lilmike's specs from the above hornresp window...the 15Hz horn gives up output to get the extension in such a small enclosure size....

Although hornresp gives a sub-300L figure for these horns, I always add ~25% to that for wood volume before I begin folding.

Kevin, if there is a chance you'd be interested in me folding up either of these two, let me know. A tapped horn may be able to dig better to 15Hz, and that's why lilmike is here...I am not as good at tapped design as I am with front-loaded designs...


JSS
 
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