Tapped horn design for 18TBW100-4

[BP1Fanatic]

The key is the 2 expansions require the same segment lengths.

 

[Brian Steele]

This is why I couldn't get it to work. See attached diagram. Expansion S3-S5 needs to be one expansion because the panel along where those points are situated is a flat panel holding the driver. Same for S1-S2. And S2-S3 needs to be the same as S3-S5 because (1) part of S2-S3 is the same flat driver baffle board and (2) shifting panel (a) off vertical to increase or decrease the expansion at S1-S2 leads to an error because external panel (b) will need to be shifted the same amount, and the box is no longer "square".

 

[GM]

Can you do anything with this one?

GM

 

[Circlomanen]

I'm looking for an existing TH enclosure for the B&C driver. Maximum punch, and sensitivity between 40- 100hz.

http://www.martinsson.cc/blog/index.php?m=03&y=17&entry=entry170302-170401

The words "maximum punch and sensitivity" indicates that you need to build a pair of ROAR18 for your B&C 18TBW100-4.

You will not need any dedicated midbass horns for punchy and tactile midbass.

 

[GM]

Hmm, ~2.38x larger than the TH, but ~ 6-10 dB greater from ~60-100 Hz/140 dB/2 pi/3 kW transients, so if size/weight isn't an issue.........

GM

 

[BP1Fanatic]

This is why I couldn't get it to work. See attached diagram. Expansion S3-S5 needs to be one expansion because the panel along where those points are situated is a flat panel holding the driver. Same for S1-S2. And S2-S3 needs to be the same as S3-S5 because (1) part of S2-S3 is the same flat driver baffle board and (2) shifting panel (a) off vertical to increase or decrease the expansion at S1-S2 leads to an error because external panel (b) will need to be shifted the same amount, and the box is no longer "square".

I'm not understanding why the middle of S3 cannot have a change in expansion. I will play around in HR and Excel today to what I can come up with. Maybe a 5 segment TH needs to be modeled where the change in expansion needs to happen at S3-S4?

 

[BP1Fanatic]

I see now Brian! There is not enough room to mount the speaker with a MTH fold and a 39.5hz tune.

S1 = 490.32cm2 (19" x 4").
S3 = 735.48cm2 (19" x 6").
S5 = 1470.96cm2 (19" x 12").
L12 = 24.13cm (9.5").
L23 = 102.87cm (40.5").
L34 = 102.87cm (40.5").
L45 = 24.13cm (9.5").
Vtc = 2305.05cc (Sd x 0.75").
Atc = 1210cm2 (Sd).

220.252 liter enclosure.
F3 = 40.62hz @ 128.11db's.
11.97mm xmax @ 51.06hz with 70 volts.
Peak = 131.05db's @ 104.36hz.
43.94% efficiency at 51.79hz.
130-131db's from 45-115hz.

Good model for a musical single fold dual expansion TH!

 

[Brian Steele]

I'm not understanding why the middle of S3 cannot have a change in expansion. I will play around in HR and Excel today to what I can come up with. Maybe a 5 segment TH needs to be modeled where the change in expansion needs to happen at S3-S4?

Let me try explaining another way. See attached diagram. Because of the layout of the MTH, the sections in yellow (S1-S2 and S3-S5) will have the same expansion. This leave the section in green to use a different expansion for the path. See that section in purple though? That lies between S2 and S3 and has the same expansion as S1-S2 and S3-S5. So the only way to get another expansion in there is to have another sim point between S2 and S3 (at the end of that purple section), and Hornresp does not offer that. So yes, while you may able to *build* an MTH with more than one expansion, you won't be able to sim it accurately.

Of course, one could argue that the section is question is short and likely won't make much of a difference to the sim anyway if a different expansion is chosen for S2 and S3, but I'm a bit of a perfectionist when it comes to sims

 

[Brian Steele]

Can you do anything with this one?

GM

I managed to come up with an MTH fold that comes close to those sim parameters, but do you see the problem? .

 

[BP1Fanatic]

Let me try explaining another way. See attached diagram. Because of the layout of the MTH, the sections in yellow (S1-S2 and S3-S5) will have the same expansion. This leave the section in green to use a different expansion for the path. See that section in purple though? That lies between S2 and S3 and has the same expansion as S1-S2 and S3-S5. So the only way to get another expansion in there is to have another sim point between S2 and S3 (at the end of that purple section), and Hornresp does not offer that. So yes, while you may able to *build* an MTH with more than one expansion, you won't be able to sim it accurately.

Of course, one could argue that the section is question is short and likely won't make much of a difference to the sim anyway if a different expansion is chosen for S2 and S3, but I'm a bit of a perfectionist when it comes to sims

I totally understand. When I was trying to put my HR model in Excel, I knew the middle inner panel would not be perpendicular to the base board. I stopped playing in Excel once I realized the speaker plate was not long enough to mount the sub.

I think I will model a 30hz TH with the same throat and mouth to get the speaker plate longer.

My thinking is if the 2 expansions are the same length, then you should be able to take 2 single folds and make one square eclosure with a double fold. I think the assumption is the middle inner panel HAS to perpendicular to the base panel. All we need to do is make sure the 4 outer panels are connected at 90*.

 

[GM]

I managed to come up with an MTH fold that comes close to those sim parameters, but do you see the problem? .

Thanks! Not surprised, it's a problem with quite a few drivers I've simmed, but if wanting to build it, then widening that last segment and back filling as required solves the problem, same as Tom did with his DTS-20, so to me it's a doable design.

GM

 

[BP1Fanatic]

Let me try explaining another way. See attached diagram. Because of the layout of the MTH, the sections in yellow (S1-S2 and S3-S5) will have the same expansion. This leave the section in green to use a different expansion for the path. See that section in purple though? That lies between S2 and S3 and has the same expansion as S1-S2 and S3-S5. So the only way to get another expansion in there is to have another sim point between S2 and S3 (at the end of that purple section), and Hornresp does not offer that. So yes, while you may able to *build* an MTH with more than one expansion, you won't be able to sim it accurately.

Of course, one could argue that the section is question is short and likely won't make much of a difference to the sim anyway if a different expansion is chosen for S2 and S3, but I'm a bit of a perfectionist when it comes to sims

You're right Brian! HR does not have enough segments to truly model a multiple expansion MTH fold. I think as long as the enclosure volume is accurate and horn is constantly expanding S1 to S5, then the model will be close to the actual build. Also, the inner middle panel has to be perpendicular to the base panel.

Here is the 30hz TH.

 

[tthorsten]

is there an tham 18 in 60x80cm in front and 60-80deep as a plan with what ever chasis i like 18sound and B&C, or faital

 

[martinsson]

Here are the Tham18 plans:
Martinsson's Blog -

Here they are in a very nice setup:
FaitalPRO | Press & Media | News Archive

Same rig installed:
https://thegloss.ie/wp-content/uplo...zine-5GT-Hens-Teeth-Hennessy-Sound-Lounge.jpg

 

[BP1Fanatic]

Nice stack! I love the grills!