My Dual Tang Band 8x12 Tapped Horn Project - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 99 Old 01-15-10, 04:27 PM Thread Starter
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Dual Tang Band W8Q-1071F Tapped Horn (completed)

Greetings, fellow audio nuts. Some of you will already know about this little project of mine thanks to my thread over at AVS, but I thought it would be good to share it here as well; if only to get a few more opinions on this little endeavor before I have the wood out on the deck ready for cutting.

This whole thing started with the advent of the Danley DTS-10, and my complete inability to afford such an awesome subwoofer. Given that I have been planning the installation of a projector here at Crazy Wolf Central, I wanted to build something up that would a) fit behind the screen, b) produce more output than my IXL 18.2.2 LLT ever could, c) teach me about horn design, and d) not cost a pile of bucks.

The gist of it is, I'm building myself a tapped horn with two Tang Band W8Q-1071F drivers. These are 8x12" woofers with 12.5mm Xmax. I found that while there is a rather impressive number of TB drivers that model well in tapped horn configs, these 8x12's are about the only ones that meet all my criteria - they're cheap, they have a good bit of cone area, they can be found for buying in Canada (well, they could... I just bought Solen out of these), and they will allow me to blow away the LLT and still have some headroom.

Before I post the Hornresp screenshots, here is my list of demands for this project:

-subwoofer can have a bandwidth of 16-80Hz, as my room is no good for anything lower than 16 and my mains are fine above 50Hz
-must be no deeper than 20"
-will be corner firing, because that's the only placement that works in this room
-has to be capable of above Dolby reference in eighth space for headroom's sake

The final design ended up being about 16.5" deep x 74" wide x 42" tall. I'm satisfied with this as is, but I would like to hear some opinions on a couple things. First, I've had some assurance that the original version's 3.12:1 compression ratio is ok... I'd like to hear some more feedback on that because in the final design it's now up to 3.35:1. I'd rather tweak it now if I have to than find out I need to buy more wood later. Am I being too paranoid about it?

The second thing I'd like to hear feedback on is whether or not y'all suggest the use of reflectors. I'm almost convinced it won't matter much to not have them in there, but there's still enough doubt in my mind to seek some more opinions on it as the design does have that one 73" stretch between folds.

Ok, screenshot time. These are all in half space. Corner loading looks to get me a good 10dB over reference, so I think I'm ok there. Attaching the Hornresp file so y'all can take a peek and play around with it as you like.

Hornresp parameters:



Schematic:



Diaphragm displacement at 36V:



Impulse response:



Phase response:



Half space SPL:



And finally, my scaled down folding diagram, done to scale in PSP:



Spot any errors? Let me know. The drivers have been ordered, will start with the actual pictures when they get here. The build will likely take place in March, weather permitting. Wood will be purchased from Windsor Plywood sometime in Feb, and will be 3/4" C2 grade void free shop birch.

And yes, there is a Wolfhorn I and even a Wolfhorn III. Wolfhorn I got left on the drawing board because II blows it away. III is still in development, and might stay there due to compression ratio worries - I found out the IXL 18.2.2 models well in a TH. Don't want to take chances with that woofer.
Attached Files wh2r5.txt (433 Bytes) 

Last edited by Oklahoma Wolf; 05-13-10 at 03:41 PM.
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post #2 of 99 Old 01-15-10, 08:40 PM
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Howdy

You don't need the reflectors for the pass band you are planning.

Mark

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post #3 of 99 Old 01-16-10, 08:18 AM Thread Starter
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Thanks - the majority of opinions seem to agree with you, so I'll put that one to bed now. No reflectors. I'm sure my not so good wood cutting skills won't miss them.
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post #4 of 99 Old 01-16-10, 05:04 PM
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Sorry I can't help with the math stuff being "challenged" on the subject, however I am rooting for you on this project because Yes I too have a pair of these drivers laying around. I just wonder how you will place them in the cabinet because mine measure abt 175 mm deep top to magnet bump out. Are you going to place them face to face or just next to each other? Anyway lets see how these drivers do, kinda a "super " KEF B 109 unit, good luck on the project!
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post #5 of 99 Old 01-16-10, 05:09 PM Thread Starter
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Re: My Dual Tang Band 8x12 Tapped Horn Project

You have these 8x12's? Cool - I can't wait to see mine. How do you like them?

On my diagram up there, there is a green line. That's the midpoint of where the woofers will be. One will be in front of the line, the other behind the line. They will be firing downwards in my diagram with the magnets hanging down (or in this case sticking up) into the mouth area of the horn. The mouth is about 420mm x 380mm - that should be enough space.
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post #6 of 99 Old 01-16-10, 08:39 PM
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Ok Wolfy

Here is something a bit different. A front loaded horn. Much better SPL / watt. Actually when I crunch the numbers on your Tang Band you have a bit of wrong data in the input screen you posted. Tang Band's numbers are more than a bit off when you use the Hornresp reality checker. There is a built-in program to compute the real Thiele Small parameters for the driver. That is of course unless you have actually measured what you have posted. But as far as I have crunched the numbers the dual 8 x 12 design is hardly anymore efficient than a competitive sealed box.

The SPL is 200watts in 2 Pi space. If you corner load it you will get at least 6 db better. With ideal corner loading you will get 12 db better.

Mark
Attached Thumbnails
My Dual Tang Band 8x12 Tapped Horn Project-8-12-tang-band-flh.jpg  

My Dual Tang Band 8x12 Tapped Horn Project-8-12-tang-band-flh-200watt-spl-2-pi.jpg  


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post #7 of 99 Old 01-16-10, 09:52 PM Thread Starter
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Hmm, interesting. That makes it look a lot different, that's for sure. Will have to think about this some.

Edit - not sure I follow this. Can't really find anything in there to compute the specs. I do know I had to get some of them by letting Hornresp calculate them, but I'm not sure how you got those numbers for the woofers.

Found a decent tapped horn alignment that works on the new numbers but there's a problem... it drops SPL almost too far and I don't know how to fold the thing when L34 is greater than L12. I don't know that I want to really try a folded horn... kind of had my heart set on the tapped horn idea.

Last edited by Oklahoma Wolf; 01-16-10 at 10:15 PM.
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post #8 of 99 Old 01-16-10, 10:34 PM
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Hey Jeremy,

Can you post the 1w spl graph into full space (4x pi)? Is the SPL graph showing a 36v input (18v per drive)?
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post #9 of 99 Old 01-16-10, 10:53 PM Thread Starter
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Here you go - 1W into full space:



Not sure about the coil config on these woofers - this is 2V in, 1V per woofer.

This is with the original Tang Band numbers, with Rms and Cms being the two calculated specs. Yeah, my original SPL graph was at 36V - the most it would take before passing Xmax.

I'm kind of glad I went and ordered the woofers before the specs came into question, otherwise I might have decided not to go ahead with this at all.

Edit - it was Rms that was the calculated one, not Re. Getting to be late for me.

Last edited by Oklahoma Wolf; 01-16-10 at 11:00 PM.
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post #10 of 99 Old 01-16-10, 11:27 PM
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Re: My Dual Tang Band 8x12 Tapped Horn Project

Don't worry too much. I believe we have had a conversation about the parameter numbers used before.

Using the TB spec sheet from Parts Express you get: SD 460, Cms 2.33E-04, Mmd 143.44, Re 3.20, Bl 15.00, Rms 5.50, and for Le they give "Levc" 0.85. The Le is almost certainly higher, but it only really effects the high end roll-off so it doesn't really matter too much here.

Now most of the time the manufacturers numbers are off, this is why when going off their supplied numbers it is best to not over scrutinize the design. If you have the ability to measure the drivers yourself, that is another story.
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