[noah katz]

I thought I remember reading that someone had modeled the DTD-10 and got decent agreement w/its actual measured response, but I forget who.


I was wondering if that person could tell me what the predicted effects are if I extend the horn length (same expansion rate as the rest) 15" and 40".


The former is pretty straightforward, the latter more work.


I'm sure it will beef up the low end, but I can't do anything that will mess up the top end, as I need to cross to the mains at 80 or 90 Hz.

 

[Ricci]

I had a sim that seemed to agree decently at-least.


Give me a few days and I'll see what I can do. Without even looking at it I think you are going to be screwed up near 90hz if you make the length much longer as that will extend the corner and should bring the notch right at 100hz down along with it. I could be wrong though. If you keep the expansion rate the same you are going to have a larger mouth with either extension length.

 

[noah katz]

Thanks, really interested to see what you get.


Interesting, I wonder then if corner loading then also imposes an upper end penalty.


Can the s/w tell you that?

 

[Ricci]



Quote:
Originally Posted by noah katz /forum/post/18101956


Interesting, I wonder then if corner loading then also imposes an upper end penalty.


Can the s/w tell you that?

That's a different thing I believe. The upper bandwidth peaks seem to be tied to the low end cut-off of the TH cabinet design. If you make a 10hz TH sim the first big null seems to drop into the 80hz range and the peaks all move down too. It all seems tied together (low corner, resonances, nulls) as part of the fundamental way it loads the driver. You only get so much bandwidth to play with. Remember I'm by no means the most knowledgeable on horns.

Maybe Littlemike, Soho54 or someone can comment on the above.

 

[noah katz]

My new receiver w/Audyssey XT32 gives lower XO freq so I have some room to play with.


Can you give me your Hornresp model so I can play with it?


Curious how you handled the throat area.


The inmost driver looks like it's in a chamber, and the other one isn't, and would be considered to be offset, no?


Also, how did you get T-S parameters for the drivers?

 

[t6902wf]

I have run my DTS-10 with a 8" long horn extension and a 30" long horn extension. When I was installing it I had a choice.


Here is a measurement from the listening position for both extensions.

The Black is the 30" and the Purple is the 8. I chose to go with the short horn because it looked better and I doubt there would be a meaningful difference is sound.

 

[soho54]

I have a DTS-10 model, but as it is still being sold I don't want to spread it around.


Here is something similar. It isn't optimized or anything, just a quick sim with similar characteristics to get you started.


You have one, right?

 

[noah katz]



Quote:
Originally Posted by t6902wf /forum/post/19867140


I have run my DTS-10 with a 8" long horn extension and a 30" long horn extension.

It sure is, thanks, Bill.


Interesting, I'd have thought 2 1/2' more would make more difference; if the corner is 14 Hz to start, that would lower it to 12.4.


But that's just on length; did your 30" extension have any flare?

 

[noah katz]



Quote:
Originally Posted by soho54 /forum/post/19867144


Here is something similar. It isn't optimized or anything, just a quick sim with similar characteristics to get you started.


You have one, right?

Thanks, and yes, I do have one.

 

[soho54]



Quote:
Originally Posted by noah katz /forum/post/18100728


what the predicted effects are if I extend the horn length (same expansion rate as the rest) 15" and 40"

They are actually pretty much what t6902wf shows in his pic above.


As you add length you gain a little more extension down low, but the rear tap position is in a progressively worse position. This will show up mostly as all the dips getting deeper here. Especially above in the 20s, and in the dip after the big peak ~50Hz. It will have a general reduction in SPL everywhere, but at the few extra Hertz you have added down below.


Up top the same things are happening, and moving down in frequency the same amount.


It is generally not a good idea to add an extension to a TH, or to try and "corner load" it by pointing it into a corner.

 

[noah katz]

Hmm, OK.


Does it make any difference if the extension has increased flare?


Seems like the bigger mouth could help LF efficiency, and maybe not do as mucg harm to the high end.

 

[t6902wf]



Quote:
Originally Posted by noah katz /forum/post/19868362


Hmm, OK.


Does it make any difference if the extension has increased flare?


Seems like the bigger mouth could help LF efficiency, and maybe not do as mucg harm to the high end.

Before I did this I traded e-mails with Tom Danley. He said it should go a little deeper.


My horn extension did not flare.

 

[jpmst3]

Interesting, I was assuming the difference would have been more dramatic.

 

[noah katz]

OK, I’m wondering if it's worth the effort to do something like the below to hopefully get a bit better output (in the form of efficiency from a bigger mouth, and as well as a little lower cutoff), and put the output at midwall for best modal performance per Welti (my other sub in opposite mid-wall.


I’m thinking a faster expansion near the mouth might be better because “real” horns seem to do that, so I can make the left walled curved or segmented if that makes a difference.


The rounded box at the right in the wireframe sketch is my center speaker; the angled right wall of the extension allows makes a space for the port output.


In the 3D view the magenta box is the DTS-10 and the blue slab it’s on is the area behind the wall where all of the equipment resides (the purple diagonal stripe is a graphics artifact).


I can set the angles to continue at the same expansion rate as the last run to the mouth, which I calculate as 34% per foot averaged over the length of the partition. The partition angle is 3 deg.


The height would stay the same as the mouth exit, 17.5”.


I calculate from the dimensions shown that the area expansion rate of the extension is 9.6%/ft; the last leg of the DTS-10 is 5.0%/ft.


Would appreciate it if one of you guys try this out in your model.

 

[noah katz]

Actually I just realized the above creates complications in cabinetry to cover it all up; there's lots of stuff not shown in the pic.


Something like the below will save me a lot of work, and is actually the DTS-10's current configuration and location.


The question is, what is the optimum angle for the left side wall of the extension.


When I get OmniMic I can try both DTS locations to see if it's worth the work to get it midwall.


Right now it's 4' from the center of the 22' long front wall.

 

[LTD02]

adding flare will tend to shift the frequency response to the right and increase the sensitivity of the top end, but for the sizes that you are talking about the differences are neglible. the horn extensions that you propose probably aren't worth the effort, just as t69's measurements show, unless it provides some other benefit such as better room interaction. the dts-10 looks pretty well optimized for its purpose.