Wolfhorn SDX Design Finished - Page 6

PL phase 1 is complete - all panels are permanently married to the bottom panel now.

This went a whole lot smoother than the last time. Mostly because I knew this time I had enough time to lay down a nice, slow bead... no need to rush things. The partial tube of PL from the storage room did indeed yield useful adhesive, but I had to squeeze the gun grip like Hercules to get it out of there. However, as a result, it looks like I will get this whole project done without even touching my second new tube of the stuff.

Did I get some on my hands? Yes. But the second I did, I went over and washed my hands with the mineral spirits. As a result, I don't seem to have stained hands this time. Of course, I didn't kick the bucket of mineral spirits over this time either. This was helpful in cleaning my slipjoint pliers too, which were in charge of removing and replacing the nail in the PL.

I also used several pieces of scrap wood this time for resting the PL tube on, so I have a lot less of the stuff smeared all over the horn panels inside.

And now, pictures. I decided not to use polyfill at all in this one, though it will get stuffed inside the dead space in front of the horn throat just in case.



Getting ready to PL the first panel... the throat block.



The old tube, ready to go.



Throat segment in place, including the driver baffle. The driver baffle was tough, because it was still warped to kingdom come.



How I pushed out the warp so I could screw the panel down. The dowel has now been removed. That panel ain't going anywhere now.



PL goes down for the last panel. I did inner panels first so that the two side panels would hold the big bottom panel true while I worked on the inner fold panels, and then did the outer panels last with the inner panels holding things true. Worked out great.



All done. Tomorrow I check for leaks, measure and drill screw holes for the top, and PL the top on. Drivers go in Saturday.

Oh yes, I expect much from this one. Currently trying to decide what demo material I'll be trying it with. Debating between my current standard, the Flight of the Phoenix plane crash, the tripod emergence scene in WotW, and the hydra and/or minotaur fight in Percy Jackson.

I could do Tron Legacy, but I don't know the movie well enough to pick a certain scene. Might be the first full movie through the new horn though.

And then... the old horn goes back into the chain. Once I have the two dialed in... extended Lord of the Rings trilogy. I've been waiting for both horns for those movies

The problem with the countersink bit is I had to drill the mounting holes for the internal panels top down... which chipped the birch layer on the underside. Therefore, there's no way to make it look good anymore, and thus no reason to use the bit.

I suppose I could have measured and then drilled up from below, but I'm a busy guy and that takes time

As is, it's taken me most of the week to get this thing together.

The other thing is, the drill is so powerful it's able to make the screws countersink themselves most of the time.

That'll probably be my approach with the top panel... measure, draw guide lines, pre-drill enough holes to line up the panels, and then just go to town on the screws. I'm using #8's, so the internal panels shouldn't split from those.

I gotta get this beast done so I can have a movie night with the old beast while the PL cures

I don't have that one, and the local rental place doesn't either

The front runner so far is Percy Jackson. Might do both scenes I mentioned, and get them on video. I do want some sub 15Hz content in there... want to see where I start getting into trouble with the harmonics on this one.

I'm thinking of a word. Starts with "D" - four letters. Rhymes with "fun."



That's all she wrote for the assembly phase. I will have some PL stains on my hands after this one. After pre-drilling a total of seven locator screws, I heaved the top panel in place, got on top of it, and went to town with the drill.

At the end of all this, I still have an untouched tube of PL. Those interested in trying this project should be warned though... I would have needed it had I not had the old stuff in the storage room. Buy two big tubes. Or four little ones. Too much is better than too little. I also have an untouched box of screws left over... 200 was enough for this one with some left over.

Panel fitment is miles better than the last tapped horn, but the top doesn't quite square up as I'd like. Ah well... close enough for horseshoes and hand grenades.

Some pics of today's progress:



Ready to start. Horn off the sawhorses.



Before anything else, I scraped off some of the excess PL and removed the brackets holding the kludge block in place. I forgot to plug the screw holes with PL, but no big deal - they don't go all the way through anyway.



My oops from the other day.



Changed my brain on the polyfill. Thin layer at the throat. Yes, I did remove that errant staple.



Using the two piece saw guide to mark for the guide lines.



Laying down the guide lines using both saw guides to insure straightness.



Final PL beads laid down.

Now, there's an idea. I have that movie lying around somewhere. I'll think it over some more.

They work, it's just that when you've been measuring and putting huge panels in place for hours with sweat pouring off you the thought of extra steps seems like torture

Hmm... it seems to be Saturday. Perhaps I should get to work again.

Sine wave testing and leak testing this morning. Will do the video stuff later this afternoon or evening depending on whether or not I decide to fire up the projector. The video will need to upload overnight (slow upload speeds here), so don't wait up for it.

Will update the thread after sine wave testing is done. This will at least tell me where the low corner really is.

I may try to use my MCACC mic to take some measurements. Don't expect accuracy from it. If it doesn't at least come close to what my ears tell me the horn's doing, I won't even bother to post it.

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.

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!

They may not be tight enough yet. Will be rectifying that soon.

Before I start really having fun, I have some work to do on the old horn. Want to get rid of the binding posts and Speakon it as well.

And then I have to call my brother in law to help me lift a near 200lb horn off the ground and on top of the new one behind the screen. Happy happy joy joy.

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. Remember that my basement is open to the rest of the house. High levels of LFE are hard in here.

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.

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.

Here's the video:

http://www.youtube.com/watch?v=2A0YsNtPqKI

Hokay... 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.

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 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.

Can't do proper measurements yet... you'll be waiting a while on those.

I keep forgetting somehow that the Reckhorn only has a 24dB/octave highpass. That fact might make setting up the MiniDSP for flatness from 15Hz up somewhat easier on me.

As for a picture of me, this is the best I can do for now:

Must be my charming anti-social personality

I've updated the OP with the plans.