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post #181 of 190 Old 07-14-2010, 10:30 AM - Thread Starter
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Take a look at the schematic diagram - you have a horn flare up to S2, but then it goes in reverse up to S3 before going back into a very slight horn flare again. As modeled, it's kind of a weird looking tapped transmission line. Thus, there's not much gain going on.
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post #182 of 190 Old 07-14-2010, 10:34 AM
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Quote:
Originally Posted by Oklahoma Wolf View Post

Take a look at the schematic diagram - you have a horn flare up to S2, but then it goes in reverse up to S3 before going back into a very slight horn flare again. As modeled, it's kind of a weird looking tapped transmission line. Thus, there's not much gain going on.

oh I saw that on the model but I was just using the sliders at that point playing around with. I got it pretty flat but then I looked at the physical model and it showed it as a coke bottle basically.

Is there anything wrong with that though?
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post #183 of 190 Old 07-14-2010, 10:44 AM - Thread Starter
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The impulse response doesn't look too good, and there are phase issues there as well due to the coke bottle effect. Sorry to say it, but there doesn't look to be any advantage there over an LLT with the same woofers.

I'm attaching what I've been doing with those woofers... maybe fiddle around with that a bit. I haven't done a lot with the Epic 10 yet - I think I'm still better off with the SDX 10 for my next one. Just can't get over the price difference.

 

tcepic10.txt 0.4033203125k . file
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post #184 of 190 Old 07-14-2010, 12:52 PM
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Quote:
Originally Posted by Oklahoma Wolf View Post

but there doesn't look to be any advantage there over an LLT with the same woofers..

I've really started to ask myself this question though.

Is a tapped horn horn a good encolsure for sub 15hz content at over 105dB? Most of the models I have played with have the excurions just flying out of control once it gets below the 15hz range, thus implementing a HPF.

I have looked at some of the LLT designs and they get lower but the drivers can be more expensive and you need a higher power.

So there is no free lunch and from what I recall of the maxmercry cinemahorn designs the enclosures get absolutely massive.
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post #185 of 190 Old 07-14-2010, 02:22 PM - Thread Starter
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Yeah - that's when it really helps to use a woofer as close to being ideal for tapped horns as possible, and then trying to get the best efficiency gain as possible. If you can model a woofer in Hornresp at half space and it has no efficiency gain over the same thing in a ported box, then it's not worth the effort.

The Tang Band horn does have an advantage over a ported box, but not a lot. IIRC my SDX10 design so far is about 5.5dB greater at 20Hz (2.83V in, half space) than a ported box with the same woofers. I'd like to get that sensitivity up a bit more, but as with all subwoofers you still have to conform to Hoffman's iron law. I want it small, so I have to give up some SPL or extension. I'm probably keeping the extension and losing SPL. As long as it hits reference in half space at the same corner frequency I'll be happy, because it's an improvement on the TB horn.

It won't be perfect, but I'm still learning this stuff, after all... I learn best by doing

In general though, I'm not planning to ever go far under 15Hz with a TH. They just get too big going that low. I have a 9Hz one modeled using my IXL 18.2.2, but the size is freakishly huge. 1400 liters.
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post #186 of 190 Old 07-15-2010, 07:36 PM
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So figuring out the xmax stuff then, hornsrep has the input for the volts (typically 28.3 volts) and when I model a horn the x-max typically doesn't go outside of the xmax.

But when i go to the max spl and run a 100-150watts through and use the xmax the horn will over run at or around 15-17hz. So does hornsrep derive volts based on watts at the x-max or the other way around? Meaning does it take more volts to run a lower hz?
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post #187 of 190 Old 07-15-2010, 07:44 PM
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Watts = Voltage^2 / Driver Resistance

To see the driver resistance look at the Impedance Graph.

In the MAX SPL you input a Wattage and an Xmax parameter. The program adds voltage at each individual frequency until either of the limits you input are hit.

If the Wattage limit is hit it just stops. If the Xmax limit is hit it turns red.

Does that help?
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post #188 of 190 Old 12-28-2010, 12:44 PM - Thread Starter
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Now that some time has passed since I got this big beastie together, I thought an update on its life in my home theater was merited.

Since I put this thing together, there have been several revisions of Hornresp. I'd long suspected that I unintentionally built this thing better than it was showing in the models. Recently, however, I decided to go revisit my work on this project and completely revise the Hornresp model to match what really got built as closely as possible. I've attached the results to this post.

The short version is, I really did build a better horn than Hornresp simulated back in the day. It's not perfect and never will be, but it's much closer to ideal than I thought it was.

Part of my desire to re-sim this thing was from the realization that it was taking all 350 watts out of one channel of my RMX-1850HD and asking for more. The excursion graphs in Hornresp alone suggested this wasn't possible - Xmax for the woofers is only at 12mm.

This thing is currently getting the full bridged output from my amp. Still haven't found its limits, but after seeing 122dB peaks during Flight of the Phoenix I sure found mine. Realistically, I'm not sure yet it's able to do reference sustained right down to the corner. But, I think that's more to do with the 10Hz highpass on it than anything else. The updated Hornresp model claims that it is indeed capable of it.

No current plans to remove the highpass for further testing, but you never know. I wasn't going to bridge the amp on this bad boy either

Some graphs now. This is simulated with 350W in. Keep in mind that the excursion graphs do not take into account the suspension getting stiffer around Xmax, nor do they consider the increase in compression ratio as the diaphragms move. I have not seen the woofers move much past Xmax in real life. They've done it, but not nearly as far as the graph suggests.

All graphs are half space.









 

wh2r5a.txt 0.435546875k . file
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post #189 of 190 Old 02-09-2011, 06:58 AM - Thread Starter
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Ok, this is a big enough deal to warrant another bump back to the top. Have a look at this picture from just after the horn went together... see a problem?



At the time I took this picture I got so impatient to hear this thing, I missed the fact that there was a screw loose on the front driver. I don't know how, but I proceeded to miss this issue for... oh... only another 10 months or so

/facepalm

Here are a couple of videos from before and after the screw got tightened at last. The duct seal was still doing its job with the screw loose, but not well enough. This is why you make sure your horn has no air leaks. The difference is fairly significant to this design. I have since boosted the bottom end a bit so my ~15Hz content doesn't get lost in all the midbass slam this thing has. I see a MiniDSP in my future.

This is Flight of the Phoenix - chapter 6. The barrel roll scene shows a big difference in excursion... most content right there is at an excursion peak in the horn. LFE level was the same both times, but the amp is bridged in the second whereas the horn was only running on one channel in the first. The before video gave me 121dB peaks at listening position. Not sure about the after video - had the meter by the horn mouth just to show it getting pegged at 126dB by pure LFE goodness

Before:



After:

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post #190 of 190 Old 06-27-2011, 08:05 PM - Thread Starter
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Due to popular demand... well, in this case that amounts to a couple people... I've done up a Sketchup file and added it to the original post. Those of you who want to try this one, it's now a bit easier.

Man... just going over this design again makes me cringe at some of the mistakes I made. It's just not the horn the SDX project is. I've learned a LOT since I built this one.

Make no mistake, it's still a good horn, just nowhere near as good as the SDX project is.
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