Beyma 18P80Nd in sub horn: Am I missing something?

[epa]

updated the pic with measurements.
best is to buy a 5'x10'(153x305) sheet

 

[epa]

ok ive modified it a bit ,see pic

 

[Thijs666]

Wow Eric, that's fast! Thanks. Ga daar eens voor naar een ontwerpbureau .

I have a sheet of 153x153 BB and some leftovers from previous projects. I intend to brace the hell out of it, but use 12mm panels to keep it as light as possible.

I see you've flattened the output very nicely. Is that because of the higher Le (3,80 instead of 1,90)?

 

[Thijs666]

Just to be correct, isn't S5 (151,4-13,01-72,55)X50 = 3292, instead of 4000?

It doesn't alter the response much, so it's not that important.

 

[epa]

ive took the averige of the red marked piece

le rizes as frequentie drops so doubling it wil give a more realistic picture.

 

[Thijs666]

So a larger horn mouth = larger S5 = shorter horn path? For example, a 10cm decrease of of the 72-cm panel is simmed with HR by the following:
- enlarging S5 by 10x50=500,
- lengthening the second Con (L45) from 27 to 37,
- shortening the first Con (L34) from 185 to 175.

Correct?

Ah, didn't know that about Le. I already wondered why Le is spec'd at 1 kHz...

 

[epa]

almost correct .
in this case the driver is perpendicular on the hornpath. so L4-5 stays aprox 27
L3-4 is shortened by 10 cm

you could make the front closed ,and cut out the mouth,leaving 3cm over on the sides to stiffen top and bottem pannel.

 

[Thijs666]

L45 doesn't change. I knew that. Ok, 2nd try:

A larger horn mouth = larger S5 = shorter horn path? For example, a 10cm decrease of the 72-cm panel is simmed with HR by the following:
- enlarging S5 by 10x50=500,
- shortening the first Con (L34) from 185 to 175.

Regarding the front, I was actually thinking in the opposite direction: make the front detachable/adjustable. That way I could use the horn for pack space, for example shoehorn in a pair of synergy horns .

 

[epa]

L45 doesn't change. I knew that. Ok, 2nd try:

A larger horn mouth = larger S5 = shorter horn path? For example, a 10cm decrease of the 72-cm panel is simmed with HR by the following:
- enlarging S5 by 10x50=500,
- shortening the first Con (L34) from 185 to 175..

you got it, in case of S5 being 4000 lenght is 185,and if S5 is 3300 lengt is ~197,S5=4500 lenght is 175(in reality acoustic path could differ a bit,compared to the sim)
looking forward to see your bild.

 

[Thijs666]

Thanks Eric! I'll take some pictures . I can hardly wait to start building .

 

[Thijs666]

I totally forgot . What about the baffle cutout for the speaker? Should that just be a round hole as big as SD?

First sawdust has been made.

 

[epa]

its 400mm

 

[Thijs666]

Thanks.

So it's not like with many FLH's, where there's a compression chamber in front of the speaker. I wasn't sure about that .

 

[Thijs666]

Some pics...

Top side:

Outdoor work space:

Speaker baffle with T-nuts glued & sealed. Also visible are dados for easy installing of the braces.

 

[epa]

great ,sawdust

 

[Thijs666]

Progress

 

[epa]

no shortage of bracing

 

[Thijs666]

I hope it's sufficient. I used 12 mm(1/2") BB ply everywhere, except for the top (which is on the bottom during construction), which is 18 mm (3/4") underlayment (pine). Max span between braces is ~16 cm (1/2 ft).

 

[epa]

maybe some vertical broomsticks between top and bottem.
horizontal should be fine.

 

[Thijs666]

Working 'prototype' ...

Did I here you think: "Man, that thing is BIG !"? True, true... Now, does it work? Let's find out...