Danley DTS-10 "Super Spud" DIY kit - Page 4

"The full kit (you can buy just the wood) including loudspeakers, should come in well under 1K."

Wow again!

Hey Tom, long time lurker and just wanted to say thanks for providing a resource that I've been looking for for a long time. Have you found most of the claims and rules of thumb in "Electroacoustical reference data By John Eargle" to be fairly consistent with the real world?

I had just a quick thought about the air velocity in horns...

Is there any reason the chuffing of a port is going to be any worse than the chuffing one might get from a horn of equal mouth area?

For the same SPL and cross-sectional area, I would expect to see much the same air velocity between a port and horn of the same exit size. I know the shape of the exit flare can have a large impact on the turbulence that is created, but one of my concerns with the tapped horn design is that the entire bandwidth is moving through the mouth exit. As the mouth becomes undersized, all of the sound is going to get affected, not just the bottom end. I suppose the proper engineering answer is to just not make the mouth undersized.

I bring it up because my first attempt at a tapped horn a few years ago resulted in all sorts of air velocity at the mouth of the horn...and enough to the point that its easily affecting the entire bandwidth.


Is that exactly true for all frequencies in the passband?

The resolution on the impedance is not really any issue of concern. Agreed that the peaks would be less rounded if a smaller resolution would be used-but what value would that be when considering the load on the amplifier?

Generally the only thing that is of any concern is the bottom of the graph.

Yes a more accurate graph could show things to the designer-but is of no use to the end user.

On the new TEF (TEF25) the lowest resolution you can get is 2Hz. That is why that was choosen.

That is effectively 1/5 octave smoothing for 10Hz and less for higher freq.

"For the same SPL and cross-sectional area, I would expect to see much the same air velocity between a port and horn of the same exit size."

Perhaps, but I don't see how there would be a problem with a port the size of the DT-10's mouth, which I gather is something like 15" x 19".

But those are the parts I'm interested in

Brandonnash,
I remember you saying that the TH 50 was really tight sounding. Now I can't remember how it compared to the other subs you had at the meet. Can you give some comments on it so I have some frame of reference to what Mike Hedden describes? I know it won't be the same environment, but it's good to have an idea.

Hi guys

When Brandon and Josh get theirs, I am sure many questions will be answered by a few photographs and such but until then A couple other questions can be answered now I think.

Mbentz asks about the measurement bandwidth and it's effect on the display which Ivan answered but I thought an additional comment might help if your not a TEF user.

The 2Hz resolution is like Ivan mentioned, roughly like a 1/5 octave smoothing at 10Hz, at 20Hz it is 1/10 octave, at 200Hz, it is 1/100 octave and so on.
As a result, at the low corner, the system will appear slightly more rolled off in the few HZ near the far left graph corner as valid data graphed to the next 2Hz bin which is empty.
You can avoid that droop when important by measuring a little lower but cutting off the display.
Here, I don't care, I just needed to see how close it was to the design model and you can see the effect is small.

Also, as the resolution (data density) is linear and the graph log, one often needs to add a fixed octave smoothing to a broad band measurement. You simply don't need a 1/1000 octave resolution at say 2Khz if that makes sense.

AS I recall, the curve has a 5% smoothing (1/20 octave) added to the display.
This is ok because low frequency systems like speakers do not produce any fine detail on their own, while some measurements show high rez details at low F's, it is normally insufficient noise rejection which goes away with many averages or closer measurement distance.
The TEF has superb noise immunity however.


So far as Port Chuffing / noise, a tapered duct has a small advantage so far as turbulence, the issue is air velocity. For a port that was roughly 14 by 16 inches across, it would make somewhat more noise than the tapered horn at the same velocity.
A quick look at the computer model predicts that at 50VRMS input, at Vmax (somewhat above the low corner) the velocity at the mouth would peak at about 7mtrs a second.
My guess would be that in a room, your attention would be drawn to other things making noise in your room well before hearing noise at 50Volts drive.

If you make one and hear a lot of noise, I would ask was it noise from the drivers rear side or air rushing around the driver?

I met and talked to John Eargle when he was a papers chairman at AES ages ago (before he passed away) but I have not read that book. He was into recording though and was a very sharp fellow.

Is that exactly true for all frequencies in the passband?

Good catch, NO, I should have said at the low corner, clearly an octave higher, the horn is ½ wl long etc.


Noah K, ( hey a name from the ancient Basslist of days past??)
How have you been (if your him)?

Best regards
Tom Danley

Then buy one and measure it however you want

What exactly will you find with the more detailed graph that would give you useful information?

lol, buying one is probably going to happen...

Well hopefully with a more detailed graph one would see nearly the exact same thing as the one that was posted. In other words, I wouldn't know until I saw the more detailed graph.

Thanks Brandon. Great description.

Yes the TH50 was loud, clean, clear with tons of headroom and it did this effortlessly.

How powerful was the amp that was being used? Was there a lot of headroom in the amp, or was it being pushed?

If the DTS 10 can do what you describe the TH 50 can, plus add the extension...

"Noah K, ( hey a name from the ancient “Basslist” of days past??)
How have you been (if your him)?"

Hi Tom,

Yep, I'm him

I'm fine, thanks, except my memory sucks.

So I'll use this opportunity to again ask you a question that you answered, which I either forgot or didn't understand to begin with:

How does acoustic levitation work?

Somehow it must be creating a pressure difference between upper and lower surfaces.

Does the object need to be like a wing with more surface on the top, and uses the AC airflow from the SPL?

Another question is, why do you need levitation in 0 g?

Wow...then the sub sure is efficient even down low (12Hz is ~ 7 ohms...very close to 90dB/m/W). Seriously I don't know how you guys are able to do that with this kind of size (compared to TH-221). Really friggin ridiculous efficiency below 25Hz. Even with one unit 2kW-program 30-70Hz output would have so much punch in a home environment that it wouldn't be funny (duals would make Mktheatre really happy ).

If its well below 1k per piece then I want 2. Heck the size...I shall put it on wheels and store it in the storeroom. Now what do I do with my TH-112....

PS. Only 6dB of room gain at ~ 11Hz? Are you sure guys, I am very sure even a 6000 sq ft room is more than that.

Thanks again Brandon. Truly incredible.

The unit has not made it out of the shop yet. Mike will take it home this weekend-I think.

Since we use pro processors-they have a lower limit of 20Hz for a high pass. So we will just not use a highpass as we would be losing a full octave.

It has been real busy around here so not much actual listening at the shop either.

Does a TH design work as well or better than an IB design? I ask because I have been considering building an IB in the attic space above my listening room. However, it seems that a TH would be more efficient as it returns both pulse waves to the room as well as the enclosure being thermally more energy-efficient, i.e. not a source for energy leakage during the cold winter months here in Connecticut.

This kit would be ideal because I could assemble it in place in the attic space.

Thanks!

Louis

My impression of the TH50 was that it was powerful, dynamic and efficient. I didn't spend much time listening to it and none of it was at low level chamber music levels. It did have a very clean, low distortion sound to it at very loud levels. I attribute this to the cabinet design filtering out some of the extra noises from the driver



Good to see you around Mike.

BTW I didn't hear any port type noises or any other turbulence from the horn mouths on the TH50 or THspud and I think that we pushed them both pretty hard at the bottom of thier intended range at the GTG. With >250sq in of area I just don't see the velocities getting up that high.

I own a TH-50 and have pushed its limits. It has never chuffed through the horn mouth. It just keeps getting louder. Truly a remarkable subwoofer. I have a very open floor plan and the 50 has no issues making the entire house a tactile environment

If that will work, that is not a bad idea. Since the the output is on the front or back face, you would have to lay the box on top of your trusses/joists. This would mean you would have a short plenum going from your ceiling to the face of the DTS10. In my case the plenum would only need to be 4" long. Not sure how big it would need to be so that it did not extend the throat of the horn. Would this work very well if installed in a ceiling sort of like an IB?

That would work fine. There are a fair number of DTS20 users who have done the same type of thing-put it in another room or beneth the floor with just the small exit into the room.

My biggest concern with putting it in the attic is keeping all the "other stuff" from vibrating and making all sorts of noise.

You WILL move some stuff with this sub.

Hi Guys

Brandon, Josh have commented on how the TH-50 sounded at the Southern GTG a while back, actually it was that event that sort of inspired this project. Thebuckman has one also and has chimed in as well on it in his house.
On that subject;
Mike has taken a measurement at the shop this morning which I thought would be interesting to post.
Keep in mind this is a big room (like 80 feet deep , 20 foot ceiling etc if I remember).

Here is a TH-50 and DTS10 measured in the demo area of the shop IE: same room, same drive Voltage, same distance etc.
This was with a different measurement system than before (EASRA with an Earthworks mic and pre) so the graphs look a little different.

In any case, it should give somewhat of an idea what the difference is sound may be like between them.
It would appear that in the 11 Hz to 20 odd Hz range, the DTS10 produces about 15 to 20 dB more sound (20dB being 100 times more).
Mikes comment was you can hear that too haha.


Noah asked how does acoustic levitation work.

Well, sound travels in two components, pressure and velocity, the minimum and maximum for each are separated by 90 degrees in phase. A radio person might recognize that radio waves travel similarly, a Voltage and Magnetic field, each separated by 90 degrees.

If one sets up a standing wave between a source and reflector or uses two opposed sources, the position of these pressure and velocity maximums are stationary in the interference pattern that is produced.

If you place a small obstruction in that sound field and it is intense enough one can levitate. The object has to be about 1/3 wl or less in size and the intensity has to be about 150dB to levitate Styrofoam, about 160dB for more interesting things like ceramic and approaching 170dB for lead.
Anyway, when you place something in that field, gravity pulls it down.
The acoustic pressure is high BUT is alternating so that pressure cancels out.
90 degrees away, you have the velocity maximum, here is the levitation force and as Noah guessed, it is like an airplane wing in a real way. The air velocity is forced to travel around the object, this is the longer path the top of the wing feels.
Here, a spherical object is pulled radially but that force BUT gravity is pulling down too.
Now the object sinks slightly so that it is in the lower part of that velocity field and so that radial force now is an upward component to it.
Stable levitation happens when that upward force is greater than the object mass and the sample sits in the bottom of the levitation well.
Humorously, one can have too much intensity, if you levitate something like 5 min epoxy (or experimental ceramic heated to 1500 degrees C in a furnace) a too high intensity squashes the sample into a disc, thick at the edges and thin in the center.
Levitating a cockroach with excessive SPL causes high speed rotation, at a lower level one could observe a very confused bug as it tries to run to no avail.

Why zero G?
Well the velocity of sound increases with temperature and passing sound from a room temperature source into a really hot furnace is no easy task. In fact, my first horn modeling software was written so that it accommodated a temperature gradient, later altered to reflect the use with loudspeakers.
Anyway, it is much harder to levitate at high temperatures so in the sounding rocket and shuttle flights, the purpose of the levitation was only to position the sample without any contact. NASA's interest was in making new forms of ceramic and glass which could not be made in a container due to contamination from a container or nucleation, (crystallization triggered by contact with a solid). The experiments were flown on Shuttle flights STS-7 and STS51a and then when the shuttle exploded, all of that work was put on hold and a few years later Intersonics closed it's doors without having that work.
Unfortunately the Servodrive woofer business (concert sound) I had started as a side endeavor , was not robust enough to save the company. Japan and Germany (science agencies) purchased several ground based levitators near the end, we thought if we could do high temperatures in one G that this might save the company but it was not to be..

It was some short time after that I started going on line and eventually ran into (electronically) Noah on an old forum called the Bass list.
Anyway, hope that helps.
Best,
Tom Danley

OK, joke's over. I don't know how or where but I've got to get one of these in my living room.

Guess I really need to get on the ball with converting my LLT's to sealed. I really need that room for one or two of these monsters.

Gah! What am I going to do with four 18's then?!?!