TH-18 Flat to 35hz! (Xoc1's design)

[j.michael droke]

Originally Posted by tb46

Hi Xoc1,....
it would be interesting to see what it looks like turned (referenced) upside down, so that the whole mouth perimeter would be able to flex. Anyway, great work, thanks.
Regards,

Hi there: If I remember correctly, JBELL uses his live sound TH's on their sides, in pairs mouth to mouth. (For the Xoc1, this orientation would place the 535 dimension vertical) ...regards, Michael

[NEO Dan]

Originally Posted by Xoc1

...the exit mouth internal dimension is 508 not 526. (Adjust S4 from 2814.1 to 2717.8)
Fortunately the effect on the sim is very minimal.

Could you post the current value for S4? I'm trying to follow along

[Xoc1]

Originally Posted by NEO Dan

[IMG]Could you post the current value for S4? I'm trying to follow along

Apologies s4 should read s5 Adjust S5 from 2814.1 to 2717.8

s4 is 409 x 5.35 = 2188.5 sq cm

Use the dimensions in the PDF in post 6 to get the hornresp sizes
Multiply the heights by 5.35 to go from mm to sq cm..
Regards
Martin

[scameron78]

would a peavey lowrider or one of the eminence 18" drivers work in this cabinet. i was getting ready to cut 2 of jbell's SS15, but i saw this thread. i am just looking for a cabinet to use for live band application only. so i will never need anything below say 45hz.

[NEO Dan]

Things are not quite lining up, am I missing something?

[Xoc1]

Originally Posted by NEO Dan

Things are not quite lining up, am I missing something?

You are using the dimensions from my sketch screengrab showing the parametric sketch relations. Thats OK apart from S3 which does not line up with the dimension shown in the screengrab S3 is 238.67 mm not 233.7
So s3 is about 1277 sq cm.
Some drivers sim lower and others sim flatter - But the actual response is still unknown untill cabs get built.

[Xoc1]

Great responses from everyone!
To surmise.
The horn mouth would benefit from having a removable steel grille – Preferably with a metal frame. (Cross braced?????) Many metal grilles have percentage open area below 50% so the material should be chosen with care. Maybe maximum performance might be a reinforcing steel frame with no grille!
The bracing should be more or less like Djims sketch. But a decision needs to be made on the thickness of the bracing to make sure that the performance of the horn is not degraded too much.
A pair of speakers can be made from 5 sheets of 5’x 5’ birch ply.
The base panel of the speaker could possibly benefit from doubling to increase its stiffness.There is enough spare material within a 5 sheet cut pair to cut a second pair of bases, as long as the bracing is not cut from the birch ply. The doubling panel could be external to the given cabinet dimensions.

[Djim]

Originally Posted by Xoc1

Cross braced?????

Only one in middle (horizontal) would be enough.
In case you want an extra 'broomstick' or removable (metal) bar, place it under the magnet.

Originally Posted by Xoc1

But a decision needs to be made on the thickness of the bracing

3x Bracing in the most outside corners 18mm (or same as the cabinet), everything else minimum 9mm.

[Djim]

Theoretical Comparison between SS15 (3015lf) and TH18 (18LW2400)



4 x SS15 Vs 4 x TH18 (2,83V)



Group Delay



In case you want to use SS15's and TH18's in the same time, crossover suggestions:

Xover @ 77Hz (top delay time alignment = 5,8mS)
Xover @ 192Hz (top delay time alignment = 7,4mS)

Also possible but not exact:
Xover @ 130Hz (top delay time alignment = 11,5mS)

[m R g S r]

Hmm perfect! thanks for that info cuz I have a spare ss15 and spare qsc rmx 1450 that I wanted to use with the TH-18's and xti 4000