Dual SDX10 Tapped Horn - Page 9 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #81 of 144 Old 06-11-11, 12:42 PM Thread Starter
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Jeremy
 
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Re: Dual SDX10 Tapped Horn

I got the drivers in and ran some sine waves. Guys, I am so disappointed right now...







...that you can't be here to experience this

Fed it with 15V for testing. Low corner is approximately 16.3Hz. No leaks found. Usable extension to 13.5Hz with 15V in. At 13, it gives you more harmonics than fundamental.

It was kind of hard to listen for leaks with everything in the room rattling and all, but all I really heard was the sound of the diaphragms moving. Nothing I can do about that with the woofers so close to the mouth. Drivers look to do just fine with the 3:1 compression ratio. I had them moving pretty good. Nothing near Xmax, but just enough to see what she could do.

This thing has a real chance of beating the stuffing out of the Tang Band horn. Can't wait for the real fun later today. I'd best go upload some pictures.
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post #82 of 144 Old 06-11-11, 12:57 PM Thread Starter
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Re: Dual SDX10 Tapped Horn

Picture time again.



Everything lined up and ready for driver installation and wiring.



Gardner-Bender duct seal ($2 at your local electrical supply or hardware store) is a handy thing to use for sealing drivers and other things. Using the last of my 12 gauge hookup wire on this project. I only have white left, so I'll wrap the negative lead with electrical tape on the end. Drivers will be wired in series (8 ohm to the amp - it's a currently bridged RMX-1850HD).



Getting ready to duct seal the Speakon. Heh... Speakon. Speakon, speakoff. Speakon, speakoff. Speakon, spea... hey, who threw the popcorn? Aim at my mouth next time, willya?



Duct seal in place, ready to install.



Wires were soldered to the Speakon. I have no fast-on connectors for 12 gauge handy and didn't want to buy them.



Rear driver duct sealed and mounted.



Both drivers in place and wired. Now, let's get us a Speakon on that big 10 gauge wire from the amp.



Ready for testing!
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post #83 of 144 Old 06-11-11, 05:31 PM Thread Starter
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Jeremy
 
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Re: Dual SDX10 Tapped Horn

I got the Percy Jackson minotaur fight on video

Good news and bad news. Good news is, the new guy hits like a meteor. Bad news... reference level on this scene makes bad noises happen. The drivers were ever so slightly kissing the backplates. Measured 122dB sustained at 1M, corner loaded.

I suspect this is a highpass issue more than anything else. This is how the Reckhorn B-2 is calibrated:



Even so, it's a bit disappointing that the old Tang Band horn can take this scene without bad noises. Even so, that design is still way too big to be practical, and has an advantage in that the compression ratio is higher.

Currently, the old horn is stacked on the new one. I expect to be joining the two to the amp before too long.

All in all, I'm calling this mission accomplished. The SDX horn mostly does what the TB horn does in less space. That's all I wanted. Wait until I highpass it properly... I should get a bit more SPL out of it

Tried to get MCACC to calibrate the system with just the one horn... it screwed everything up. I must have had the mic placement wrong.
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post #84 of 144 Old 06-11-11, 09:27 PM Thread Starter
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Re: Dual SDX10 Tapped Horn

Ok, last major update for the day until I can get the video uploaded.

Clanking drivers was indeed down to the highpass being too low. I'm just not used to dealing with drivers that have XBLL motors. The Tang Band woofers, when they get to Xmax, stop pushing as hard and start absorbing power instead. The SDX's keep pushing.

Therefore, a properly set highpass is somewhat more critical with the SDX horn. I strongly suggest to anyone interested to grab a MiniDSP. While you could still use something like my Reckhorn B-2, it's not easy at all to get it set up right for this horn.

Now that that's out of the way, I just ran my first full movie through the SDX horn. And the TB horn, too. Incredible Hulk. The sonic cannon scene was out of this world with both horns running at the same time. That said, I need to try and do some EQ'ing. I have too much above 50Hz this way. Another excuse to buy a MiniDSP.

A couple more pictures:



The standing wave correction MCACC applied to the SDX horn for Percy Jackson.



The two horns side by side. One's 850L after materials, one's about 730L.



Yes, I did end up having to stack a 180lb horn on top of another horn by myself. That was not easy. Old one on top, new one on the bottom. Center speaker removed due to low clearance otherwise. While moving the TB horn around, I heard rattling inside. Did a few horn acrobatics, and some loose dried PL fell out of the mouth. Explains the odd noises I heard from it now and then.

Each horn is getting a channel of the 1850HD at 8 ohms, clip limiters off. The two get incredibly loud together, even with the improper highpass.

Giving the two a rest for the evening. I think I've had enough five star bass for one day, and the power is going crazy here. Tomorrow, I'll see if I can get the response smoothed out some and fix the highpass.
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post #85 of 144 Old 06-12-11, 04:23 AM
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Re: Dual SDX10 Tapped Horn

Quote: Yes, I did end up having to stack a 180lb horn on top of another horn by myself.

I don't think OH&S would approve.

Silence is golden but duct tape is silver.

DIY completed:

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post #86 of 144 Old 06-12-11, 04:51 AM
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Re: Dual SDX10 Tapped Horn

180lb!! Imagine if your horn was build using MDF

On the other hand, any issues with your neighbours complaining?
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post #87 of 144 Old 06-12-11, 08:35 AM Thread Starter
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Re: Dual SDX10 Tapped Horn

Quote:
robbo266317 wrote: View Post
Quote: Yes, I did end up having to stack a 180lb horn on top of another horn by myself.

I don't think OH&S would approve.
Meh... I may have my health problems, but I'm still 6' 6" and plenty strong for my size. Once lifted one of my 1988 New Yorkers off the jackstands one rear wheel at a time because the jack failed

Quote:
killa12222 wrote: View Post
On the other hand, any issues with your neighbours complaining?
Nope - we're on the edge of town, and the only neighbor is in her 90's. I don't normally listen to stuff over reference anyway. I couldn't until this second horn... the room is open to the rest of the basement, which in turn is open to the whole house. Takes a lot of SPL to fill all that up. That's why I was so unhappy with one 18" in a vented box.

Anyway, the video's online now:


I wanted to get more of that scene on there, but I also wanted to stop the drivers from clanking. I might do a better video some other time.
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post #88 of 144 Old 06-12-11, 10:20 AM
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Oliver
 
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Re: Dual SDX10 Tapped Horn

Lucky! Whenever I try to crank my bass, the neighbour comes knockin on my fence

Anyway, how does the horn sound on music?
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post #89 of 144 Old 06-12-11, 11:31 AM Thread Starter
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Re: Dual SDX10 Tapped Horn

Haven't tried it with music yet.

This morning I got the Reckhorn re-calibrated. I got MCACC to run properly. I then tested using Flight of the Phoenix.

Big, big improvement for the SDX horn from yesterday, even though I was calibrating and running both horns. Measured 120dB one meter from the mouth of the SDX horn, and I don't think I saw the front driver move past maybe 15mm both ways. But then again, that's with both horns working. As I have the time, I want to recalibrate to use only the SDX horn and see if it's out of trouble now. But I'm waiting on decent measurement gear too, so my general observations will have to do for now. Would rather do it all when I can get those measurements so I don't have to be constantly tweaking the Reckhorn.

I did try to get some measurements with the old SPL meter and cal file, but high level sine wave testing this morning tells me it's nowhere near accurate below 20Hz.

Anyway, here are the before and after tweaks to the Reckhorn's low pass filter:



Green is before, purple is after. 3dB decrease at 15Hz vs. before.
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post #90 of 144 Old 06-12-11, 05:49 PM Thread Starter
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Jeremy
 
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Re: Dual SDX10 Tapped Horn

Did a little more testing this afternoon using test tones and sine waves. In room response looks to be a lot like the graph of the Reckhorn's output with some nulls here and there.

As to excursion, I tested high level sine waves from 10-15Hz. 13Hz looks to be the problem area for the SDX design. I ran both horns up to +5dB, and 13 was where I saw the most excursion on the SDX horn. The TB horn didn't have a problem with it, but that's because the W8Q-1071F's motor runs out of gas faster past Xmax, as mentioned.

That said, with the new lowpass settings, running at +5dB, I couldn't get the SDX drivers to bottom out this time. So, I'm safe now to well above reference level. Of course, having two horns doesn't hurt, there, either.

So, I think for prospective builders I'm going to suggest a 12Hz 48db/octave highpass. Higher if you want to really get the SPL out of it. Lower if you have a small room. I want to do 96dB/octave, which will require that MiniDSP I mentioned. It's becoming a priority to get one now.

In terms of audible harmonics, I didn't hear any until 0dB with the current highpass settings on the super low stuff. I'm talking 12-14Hz. 10Hz produced harmonics at -5dB. 14Hz fundamental was very strong. 15 even more so... measured 106dB on the SPL meter. And of course, 16 is where the horn starts to really get going.

Last edited by Oklahoma Wolf; 06-14-11 at 10:52 AM.
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