THAM15 - a compact 15" tapped horn

[Xoc1]

Way back in post 7......
I commented that the 135mm dimension close to the horn mouth seemed small in comparison to the expansion of the horn.
Martinsson replied in post 10 that this dimension was intended to keep a longer L23 length.
I did a best fit the horn as Martinssons original drawing, and inputted the straightened dimensional data into hornresp. This sim then shows a massive dip at 165-170 hz.
I then reworked to get a linear taper throughout the L23 section. I retained the 135mm dimension.
I did increase the S2 compression slightly from 2.18 to 2.46
This filled in the dip by 5db and made the dip W shaped.
Attached Hornresp sims and reworked dimensions
Hope this helps

[jbell]

Originally Posted by Brian Steele

I can give you one example from the man who actually came up with the TH idea, Tom Danley - the TH-SPUD. He released the plans to the 'net - a search for "TH-SPUD clone" should bring up a few hits.

Please point out to me where he's used "reflectors" in that design. For a sub that wide and high that's designed to do 19Hz to 125 Hz, you'd think he'd have at least one reflector in there, right?

Hmmm... interesting you brought up the SPUD... let's investigate that a little bit shall we?

Originally Posted by Tom Danley

Hi Eva, bjorno, all

A couple thoughts;
Eva said “In a tapped horn the phase varies wildly across the passband” and “Phase matching a mid/bass system and a tapped horn is already difficult enough.”

Perhaps in what you’re looking at but normally a measurement trumps a computer model. Simply, some features that are predicted in Akabak don’t exist in the physical item.
If your going to have faith in a prediction it has to be founded on some track record comparing with measured results. I can tell you Akabak which I use has some issues, it would be no fun at all to tell you what to do anymore than pointing out a trail.

If your first statement were true, where exactly do you see this in the measured response of say a th-215? Keep in mind, in the Tapped horns that aren’t as flat with just one unit, if you choose to eq them flat, you generally correct the phase response.
Also some Tapped horns have as little as approaching half the measured GD associated with it’s low corner compared to a vented box with the same corner F (due to it being a quarter wave 90 degree resonator and not an 180 degree inverter). This much of a difference might be audible and why they sound different.

http://www.danleysoundlabs.com/pdf/T...ec%20Sheet.PDF

The spud is a new product, we have not done the normal formal outdoor half space measurements yet pending time and weather.

So far as using them in a full range system, a Tapped horn is part of at least five of our full range products including the SH-50.
Keep in mind, our stand alone subwoofer products are normally used below 70-80Hz as the spud is for home theater use.
Merry Christmas, Happy Holidays and good sound to all!
Tom Danley

Hmmm.... seems like danley is saying akabak doesn't show you everything, and hornresp agrees with akabak.... hmmmm.....

Also, wonder what function you think sound absorption accomplishes in this location? hmmm.. maybe eliminating some unwanted 'reflections' or 'standing waves' ????

In a HT setup where total spl is not the goal, absorption is an option, where every db is precious, reflection is a better choice.



from here: http://forum.realmofexcursion.com/en...ts-10-kit.html

hmmm....

AND if you follow the diyaudio thread from danley's quote above you'll see where adding additonal absorption where it wasn't necessary created a dip that hornresp said shouldn't be there, and when removed the dip was removed..... How do you suppose absorption created an extreme dip? shouldn't it have just lowered the total spl only?

Hmmm...

sorry, but not buying your TH-SPUD argument.

[Brian Steele]

Originally Posted by jbell

Hmmm.... seems like danley is saying akabak doesn't show you everything, and hornresp agrees with akabak.... hmmmm.....

No argument there. HornResp does not model box losses or the effects of lining along the path of the horn. Will return to the latter a bit later...

Originally Posted by jbell

Also, wonder what function you think sound absorption accomplishes in this location? hmmm.. maybe eliminating some unwanted 'reflections' or 'standing waves' ????

I think they are there to absorb frequencies outside of the horn's designated passband, making x-over work and integration with a full-range system a bit easier.

Originally Posted by jbell

AND if you follow the diyaudio thread from danley's quote above you'll see where adding additonal absorption where it wasn't necessary created a dip that hornresp said shouldn't be there

HornResp does not model the effects of absorption in the horn, so it wouldn't have anything to say about that situation.

Originally Posted by jbell

and when removed the dip was removed..... How do you suppose absorption created an extreme dip? shouldn't it have just lowered the total spl only?

No. The level of absorption of most materials doesn't remain the same as frequency changes. Among other things, it's frequency-dependent. Also, a TH's response is the combined response from both the front and back of the driver and the use of absorbtion changes the relationship between these two, and as a result the combined result will also change, in a way that can't be predicted by HornResp.

[jbell]

Originally Posted by Brian Steele

I think they are there to absorb frequencies outside of the horn's designated passband, making x-over work and integration with a full-range system a bit easier. .

You just can't bring yourself to say that Tom uses various techniques to tackle IN BAND reflections and standing waves. From absorption in the Spud, to helmholz in the dts-20, and (most likely) oblique reflectors in the PA horns.... (last I checked, I couldn't find any real pics of the inside of a TH115.)

There ARE things you have to do in band in a TH in the folding process.... There ARE things you have to do in band... (repeat, repeat, repeat)

In the 12 step approach, you'll never get to step 12, until you start at step 1.

[Don Snyder]

Where did the 160Hz dip go?

[Brian Steele]

Originally Posted by jbell

You just can't bring yourself to say that Tom uses various techniques to tackle IN BAND reflections and standing waves. From absorption in the Spud, to helmholz in the dts-20, and (most likely) oblique reflectors in the PA horns.... (last I checked, I couldn't find any real pics of the inside of a TH115.)

At this point you are only assuming for the Spud and the PA Horns, and you're totally wrong on why Helmholtz resonators were used in the DTS-20. They're used primarily to cut the audibility of driver distortion, not affect in-band frequency response - see PSW Sound Reinforcement Forums: LAB Subwoofer => Helmholtz resonators?

[Brian Steele]

Originally Posted by Don Snyder

Where did the 160Hz dip go?

Nice. And no reflectors required either .

[Xoc1]

Originally Posted by Don Snyder

Where did the 160Hz dip go?

Maybe its something to do with going from a internal volume of 140 litres to 210 litres

[Don Snyder]

Bumping up the volume, different driver, dual taper ... I'm sure all had a part in this mod. All these boxes are about 21 inches wide, and
reflections/cancellations happen side to side as well! I guess that I'll just have to make one of these and see how well it compares to the sim.

Brian: Hornresp sims the schematic layout ... we won't know what effect the folding has until we build one.

~Don

[4pyros]

Don; What was your mod to THAM15? to get that sim? Andy