[aceinc]

For an exercise I have decided to build a Tapped Horn. Tapped Horns for those unfamiliar are the latest brainchild of Tom Danley, who has brought sound to the world in ways others have never thought of. Some of his designs include Servo Drive, Unity Horn, Synergy Horn, and Tapped Horn.

At any rate I have been on the side lines watching various forums, waiting for an opportunity to build something that had a reasonable chance at being close to one of his designs so that I could determine what all the hubbub was about. I wanted to build something physically similar to one of his designs rather than design one from scratch because I don't trust my design prowess.

Danley Sound Labs has recently started building a HT sub with reasonable specs, and somehow a copy of a design document with physical measurements has gotten on to the web. Other folks identified the drivers used as Tang band W8's The name of the sub is TH-SPUD. Well, I took the design, plugged in the horn geometry to a program called HornResp, and tried two different types or drivers, the Tang Band W8's and the CSS Trio8's. The Trio8's make prettier graphs.

The Trio8's are a bit pricier at $80 each vs $65 each for the WB-740P, but in addition to having a better HornResp plot, they are 8 ohms each, using two should yield a nice 4 ohm enclosure.

I started the thread by saying "For an exercise" and what I mean is that once I am done with testing it, I do not have a place in my home for it. I have an associate that says he has a place that it will fit in his house so I will be giving it to him. I will be testing it against my current set up which includes two 10" Titanics, and 1 Rythmik Audio DS15. If I get some help, I might have a sub shoot out in my front yard (rather large) with the TH-SPUD clone, the speakers just mentioned and a 12" ported sub I built a number of years ago.

The amp that currently drives the Titanics, and will be used for testing the new sub is the an older NAD stereo power amp rated at 100 Watts RMS per channel @ 8 ohms. I am currently running it into the Titanics, 1 per channel. It can be set up bridged I believe, but I've never tried it.

Hornresp says I can get about 113 DB at 20hz using 200 watts with this enclosure/driver configuration. I will be testing with REW.

I am at the stage where I have most of the construction complete, and should finish it tomorrow.

I will post pictures in future posts.

Paul

 

[aceinc]

I actually do have a question for the masses.

Does anyone have an educated guess as to whether any acoustical treatment of the horn's path would have a benefical affect on the quality of quantity of the sound?

For no particular reason I was thinking of treating the bends with felt or foam padding.

I haven't made up my mind, and I will be sealing the cabinet later today, if anyone has any input I'd love to hear it.

Paul

 

[aceinc]

Due to my wood working skills (or lack therof), the actual size is 11" x 47-5/8" x 45-1/2". I am using POS (Piece Of Shizzle) Home Depot 7 ply birch, which is full of voids. I have followed the dimensions as closely as possible with the exception of the 60 degree angle piece for the second driver.

Since the Trio8's are fairly shallow, I offset the portion of the throat by the thickness of the wood (18 mm) and the Trio fits nicely.

All joints are butt joints which are glued & nailed with 2" brads. I didn't think it was needed but I did round over the wood in the labyrinth with a 3/8" round over bit.

Since I can get to both sides of both drivers, I will be mounting them with 10-32 x 1" phillips pan head screws and nuts.

If anyone has a good idea on how to mount the driver access panel so that it will seal well and can be removed and replaced I am all ears.

Paul

 

[aceinc]

Here is a picture of the access opening. I have not installed the top panel yet.

I also added a view of the innards.

Paul

 

[aceinc]

I'm asking questions at DIYAudio collaborative tapped horn, but unless I start a new thread my build would get lost in the sauce, so I decided to post my build thread here. I may start a build thread there as well.

I was going to attach the panel to the top & bottom of the enclosure, as the top & bottom sit inside the sides. Do I need the extra wood? Things might get tight in mounting the drivers.

So you are suggesting standard wood screws? About 3" centers?

I have PE 260-540 speaker gasketing tape. My concern is how to get the tape joints to seal.

Paul

 

[aceinc]

Below are screen prints from HornResp. If you notice the EG box, it has 28.28 which translates into 200 watts at 4 ohms. Each of the Trio 8's are rated at 200 watts at 8 ohms.

In my research (Mainly reading & partiicipating in other forums) I am led to believe that the wild fluctuations at the higher frequencies are not really there when the sub is built. Some folks postulate that it is due to the Hemholtz effect caused by the multitude of folds. This is of course one of the things I want to empirically test.

 

[aceinc]

Well my first test results;

The purpose is to loosen up the drivers.

Playing various "ultimate bass" videos off of YouTube through my Carver Reciever.

My 16 year old son's comment, while standing right in front of the sub, "that isn't a sub, it's an air conditioner."

My lovely bride working on her computer about 5 feet a way said she was getting nauceous, and asked me if the sub could do that?

I will do proper testing soon. My rat shack meter says I was getting up to 105 db at about 1 meter in my computer area. I have no idea what the power rating of my Carver receiver is.

Paul

 

[aceinc]

I thought I'd post one more picture of the unit with the top off. It looks a bit better in the fresh air.

The bad news is I don't have a garage or a basement, the good news is that this is S florida and this is the best time of year to be outdoors.

 

[aceinc]

Over at audioholics, there is a thread that has the drawing that you posted above. In the same thread pretty early on there is a copy of the spec sheet which defines external dimensions, panel placement, etc.

I don't know if anyone is trying the same thing. I suspect that once I post the results of my testing other folks may make up their mind. I believe I will have time to test it this weekend, I will post the results afterward.

Paul

 

[aceinc]

Since I am giving the sub away after I am finished testing, I'll let the new owner worry about an amp.

Paul

 

[aceinc]

Myn, between the two pictures you posted, you should be able to build the box. The material used is 18 mm thick. I adjusted the throat end as you can see in the photos posted earlier, instead of a 60 degree angle for the second driver I followed the same geometry, and stepped it down by 1 thickness of the material, 18 mm.

My approach was to have Home Depot cut two ~43.5" x ~46.5" pieces out of 1 piece of plywood, and rip 4 - 11" x 48" and 5 - ~9.5" x 48" pieces out of another. I took the like pieces clamped them together and using a hand planer made them as even and square as possible. Which I could have done better.

I think the most important part of the project was this step;

I then took the measurements from the first drawing you posted and using a 48" ruler I laid out the position of all of the internal pieces on three surfaces, the top (for nailing), one inside (for placement), and the bottom (for nailing). This took the most time, and I redrew some of the lines three times to make sure I got it right and that they would all line up.

I attached the sides first, though if I were to build another one, I might only do the two sides that internal pieces attach to (I think). I then used lots of glue and two inch brads and a nailer to put in the internal pieces. Don't forget to use a square to get the internal pieces perpindicular to the base. I drew lines on the outside everywhere I needed to nail.

One trick I used for doing the real shallow angles since I didn't trust my cheap protractor, was I used a framing square and a ruler and measured the distance off of square the pieces were at 11.5" which is the width if the bed of my mitre saw. I then cut a piece of scrap that thick and placed it under the piece I was about to cut (11.5" away from the cut). This seemed to work out well. On the piece with the largest angle, the internal piece nearest the mouth, I used the protractor which gave me 94 degrees, and that worked well too.

I am still trying to exercise the drivers so that I can test this weekend. I have disconnected my DS15 and have the sub out of the receiver going to my NAD Amp. On one of the two channels I have the TH-SPUD, nothing on the other channel. I allowed the MCACC auto setup function run, and it had a problem, saying that the sub was too loud. I bypassed the error and let the auto eq finish, when I looked at the settings it had the sub at -10 DB. I watched the Fantastic 4, Rise of the Silver Surfer BD, since I really don't have any movies with good sub wooferage.

I'm not sure about the sound. There are a couple of scenes where I thought there should be more bass, but I haven't watched the movie in a while. I didn't want to do A/B testing with the DS15 just yet. In addition my wife was watching 24 in the family room, and I couldn't turn it up too loud.

Perhaps tomorrow I will take the time and hookup the NAD in Bridged mode.

One other thing I did recently and I would recommend is I had an electrician wire a dedicated 20 amp circuit behind the Entertainment system. Now my lights don't dim when I fire everything up.

Well that's all for now.

Paul

 

[aceinc]

I should be able to do FR graphs ala REW, but that will have to wait until Saturday.

I am at the office right now, I will try to get a few more pics with the top on. It is standing in my living room and looking rather large. My wife is rather understanding as long as I promise it is not permanent. Don't expect beauty, as I am not a cabinet maker.

Paul

 

[aceinc]

Regarding bracing, I did not put in any bracing, but based on the limited testing I have done I would add two braces, one along the long external panel heading away from the drivers, and the second heading down the long side after the first bend. The rest of the cabinet seems fairly vibration free even under heavy load.

I might be wrong on this but the internal panels should be pressurized from both sides at the same time and wouldn't need bracing.

The reason I didn't do the 60 deg. driver mount was I did not believe it would have any effect on the sound, and the drivers I chose are relatively shallow so they fit in the space with what I feel is enough room for breathing/cooling. That combined with the fact that it made construction much simpler.

I did not put any damping material in, I might put some material in behind the drivers, but I have none now. I went back and forth on this but decided in the end to not put any in.

Paul

 

[aceinc]

The drivers are wired parallel out of phase.

If the Trio 8's fall flat on their face, I may try the W8-74p's.

My thoughts on dampening for this enclosure would be to control harmonics, and other anomalies outside of the intended frequency range of the cabinet. If properly crossed over with a steep low pass filter I feel that there shouldn't be much additional that dampening would provide, and there is the possibility that it could/would reduce the overall efficiency of the cabinet.

Were I truly prototyping this cabinet in preparation for production I would do a lot of things differently, starting with making many of the panels removable. This would allow fine tuning in bracing and dampening without building multiple prototypes.

My purpose however, is to prove to myself whether there is something "magical" about a tapped horn. I chose the TH-SPUD because it seems unlikely that you could get room shaking 20 hz bass out of two 8" drivers, whereas a 12" or 15" decent driver in properly designed enclosure can do this. So putting one or more 12" - 15" inchers in a Tapped Horn wouldn't prove as much to me.

I might not be doing any of this if I had been able to get into Danley Sound Labs. Over the summer my family and I were taking a driving trip from S Florida to S Florida via Mt. Rushmore. We all chose things we wanted to do, and I chose stopping by Gainesville Ga. on the way back south. Well, we stayed in Helen Ga., on a Sunday night and early the next morning I called DSL, and to my chagrin they had no one available to do a demo that day. It was my fault as I hadn't called a few days in advance, but I didn't realize I needed to.

At any rate I was bummed:hissyfit:, and I have been scheming of how I was going to satisfy my curiosity, so here I am building this TH-SPUD clone. As luck would have it, my wife will be on the other side of the state this Saturday, so I'll be able to play all day without interruption.:yay:

I'll try to keep everyone posted on my progress.

Paul

 

[aceinc]

I have a radio shack digital SPL meter, REW, as well as a behringer ECM microphone, and small mixer.

The other questions I think I covered in previous posts.

Paul

 

[aceinc]

Had I seen the last picture posted by Myn before I sealed the cabinet up I might have changed my mind about dampening.

It's a bit late now for me on this cabinet, but others can certainly learn from this.

BTW myn, where did this picture come from? Are there additional pictures posted on the web?

Paul

 

[aceinc]

I am starting to test with REW. I have a RS Digital SPL Meter as my Mic. I have a NAD 2200 amp in bridged mode for the amp and a toshiba notebook with an internal realtek sound card as my source.

Initially I will be testing in my living room which is 15.5' x 26' x 9' with various pieces of furniture, a fireplace and openings into the rest of the house.

What kind of tests should I perform?

My first test I thought to perform is to put the Mic about 2" away from the mouth of the horn sitting on a pillow.

What else would folks like me to do?

Paul

 

[aceinc]

Yes the weather is nice, but the person that is supposed to get the sub when I'm done never showed up to help.

I have done some testing, but not enough. Below are some plots in my living room. All plots have no equalization. The first plot is of my main sub(s) documented here - http://www.hometheatershack.com/forums/diy-subwoofers/2569-waf-limited-sub-system.html the only differences from this link and as tested is the subs are slightly off center and pushed together.

The second is as I described above with the RS-meter as a mic and about 2" away from the mouth. Third graph is with the sub centered and the mouth pointing straight up. Both the last and the first graph were taken from the main listening position about 8-10' away. The mic in these (first & last) two tests was a Behringer ECM 8000.

Paul

 

[aceinc]

Unequalized it doesn't have the same low freq visceral sensation that my DS15-titanic combo does. I put my BFD back in, and dialed in a flat house curve, and it sounds better.

I still have the mouth facing up about two feet in front of a bay window. I will be doing some listening today to see whether I can get it to distort. One thing I would like to try is to see if I can get the Pioneer AV processor to send sub data to the sub when the source is stereo, either MP3 player, CD, or ipod. I would like to try some sub torture test mixes.

Paul

 

[aceinc]

Well I watched the movie "Wanted" today, while I would not recommend it from an aesthetic, or artistic point of it does have lots of "boom factor." I had the TH-SPUD upfiring with the BFD in place.

I used the Pioneer MCACC to calibrate the room, and it set the sub at -8db. I boosted the signal to -2db, because I wanted to feel the movie, and I was testing the sub after all.

Let me digress, I did a bit of research on my NAD 2200PE and I found this quote;

"The NAD 2200 is so powerful in the normal stereo mode that few listeners will ever need more. For special situations the two channels of the 2200 can be bridged to form a mono amp of truly immense power. Its rated continuous sine-wave output is 400 watts, while its dynamic power output exceeds 1200 watts into 8 ohms and 1600 watts into 4 ohms"

So I guess for the moment I do not need to look for another amp.

Meanwhile back to my impressions, with the system thus configured and the sub about 8' behind the listening position, I watched to the movie. The bass seemed as good as the DS15-combo, I could feel the things I believe I should feel. Everything felt tight and fast. At the end of the movie there is a "theme song" with fairly heavy bass, so I cranked the volume up from -15 DB to -7 DB before I heard distortion, remembering I had the bass over by about 6 DB according to the way MCACC wanted it setup, I think it did really well.

This is rather subjective, and I will get back to the objective soon.

Paul