Beyma 18P80Nd in sub horn: Am I missing something? - diyAudio
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Old 2nd December 2012, 01:38 PM   #1
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Default Beyma 18P80Nd in sub horn: Am I missing something?

Hi all,

I've been lurking around here for quite some time now and I'm very enthusiastic about the subhorn designs you guys come up with. Encouraged by the possibilities, I started playing around with Hornresp. With the help of some excellent tutorials (thank you lilmike form AVS), I am starting to get the hang of it.

Now for the reason I started this thread: lately I had the chance to buy a smoked Beyma 18P80Nd for a nice price. I still have to receive it (eBay purchase ), but a recone kit can be ordered for 110, so it's quite a bargain if it all works out, I guess. I really would like to come up with a solution for using electric drums on stage (I'm a drummer) and I hope to work out a subwoofer integrated in a drum riser/stage/E-drum set, so I would be able to set up in the blink of an eye.
This drum riser can be as large as 155x94x70 cm, but that would included the e-drum set as well, so I'd like the height to be limited to around 50 cm (or so), otherwise I won't be able to get the whole rig into my car...

So I started working on some horn designs using the 18P80 and the (15.5x9.4x5.0 dm) ~ 700L available. I came up with these. Please tell me what you think about it, as I am wondering if these numbers are to good to be true ...

Tapped horn 700 L:

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800 watts:
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Front loaded horn 650 L:
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800 watts:
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Front loaded horn 700 L:
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800 watts:
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Old 2nd December 2012, 03:29 PM   #2
epa is offline epa  Netherlands
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hallo thijs
the sims look ok.
but there a difference between simulated volume ,and actual(bild)volume.
this can be 25~35% bigger .
so a sim of 500 ltr could turn out to be a huge 750 ~850 ltr cab.
other then that the beyma seems to work verry nice in a th.
what are you going to use for mid/high frequentie?
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Old 2nd December 2012, 05:38 PM   #3
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Quote:
Originally Posted by epa View Post
hallo thijs
the sims look ok.
but there a difference between simulated volume ,and actual(bild)volume.
this can be 25~35% bigger .
so a sim of 500 ltr could turn out to be a huge 750 ~850 ltr cab.
other then that the beyma seems to work verry nice in a th.
what are you going to use for mid/high frequentie?
Hoi Eric,
Isn't the compression ratio of the first fl a little too high (3,59:1) for an 18"?

I did realize there would be a difference in volume, but that big !? I am contemplating to build with 12mm BB on the outside and 10-12 mm underlayment on the inside, with lots of internal bracing and save a little on volume as well as weight. I have 2 T48s in 21" width (they are built with 12mm BB sides and 10mm underlayment internals) that work quite good, but I don't really have a reference since I'm not a pro. I know this probably isn't recommended, but the underlayment is cheap as sh*t, so it practically only costs me my free time.

Yes, the th seems to have the edge in spl. But since xmax (linear) is 'only' 7.5mm, wouldn't the flh with its lower diaphragm displacement values be less prone to power compression and thus ultimately be able to approach the simulated spl?

And how about the dip in the th between 100~200 Hz? Would the flh be able to play higher? Or is that going to sound really 'boxy'? (I know my T48's don't sound very nice above 120Hz)

I'm not sure yet on the mid/high. Any suggestions ? For the time being I think I will use my DR200s.

Last edited by Thijs666; 2nd December 2012 at 05:46 PM.
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Old 2nd December 2012, 06:24 PM   #4
epa is offline epa  Netherlands
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taking a closer look,yes it th cr is a bit high for an 18". 2:1 is reccomended for 18"
working with 12 mm ,and not use angled corner pieces,wil help getting the total volume down.
ofcourse it al depends on the layout.

lower diagram displacement also means less cooling from the pole piece.
id say the th is x-max limited ,and the flh power limited.
both need a highpass filter.
the th hpf can be set lower then the flh hpf in your examples.

the flh wil play much higher.
the th, if you make the th s2 area smaller the dip wil be smaller.

if i understand corectly you wil be using this only as a backline for drums?
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Old 2nd December 2012, 08:51 PM   #5
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Quote:
Originally Posted by epa View Post
lower diagram displacement also means less cooling from the pole piece.
id say the th is x-max limited ,and the flh power limited.
both need a highpass filter.
the th hpf can be set lower then the flh hpf in your examples.

the flh wil play much higher.
the th, if you make the th s2 area smaller the dip wil be smaller.
Thanks! The way I interpreted the displacement figures was that the flh's -in theory- wouldn't need a high pass filter, since 26mm is never reached with 800 watts... (not that I wouldn't implement one!). But I didn't think of the cooling factor. Good one!

Adjusting S2... something like this? (cr raised to 1.90:1)

Click the image to open in full size.
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800 watts:
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Click the image to open in full size.

Quote:
Originally Posted by epa View Post
if i understand corectly you wil be using this only as a backline for drums?
Yes . And perhaps I will allow the bass player to plug in if he needs some back up on the lows, but I think it'll be difficult to get a balanced sound without a sound guy.
Of course with proper PA it won't be needed, but that has practically never happened where I played up to now (mostly cafe's).
Attached Files
File Type: txt Beyma18P.txt (455 Bytes, 5 views)
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Old 4th December 2012, 02:19 PM   #6
epa is offline epa  Netherlands
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yes this looks nice
if you look at the excursion plot ,you can put the hpf at 35 hz and boost 35hz with 6 db with a q of 2.
that way you can extend the sound to a nice 35 hz f3
do you want me to model something like that.
specify the outher dimensions.

erik
edit 155x94x50cm?
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Last edited by epa; 4th December 2012 at 02:33 PM.
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Old 4th December 2012, 04:33 PM   #7
epa is offline epa  Netherlands
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here is a scetch
simple design.
easy tuneable by cutting off the front bafle (red)eg mouth gets bigger and the hornpath shorter.
Click the image to open in full size.
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Old 4th December 2012, 09:30 PM   #8
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Wow Erik! That's easy indeed . I must be the millionth one asking which software you use (or is recommended)? I tried looking for it on the forum, but for some reason it doesn't come up in the results. I must be using the wrong search term . I found a thread with spreadsheets for laying out the horn though. Haven't had the time to read through it though...hopefully tomorrow.

I'll save your design locally, just in case. Thanks again .
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Old 5th December 2012, 04:43 AM   #9
epa is offline epa  Netherlands
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hoi thijs
i use autocad,
but people on this forum sugest sketchup.
i wil check the exact measurments and a detailed drawing.
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Old 5th January 2013, 08:28 PM   #10
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Finally I think I was able to translate this design into akabak. Here's what I've come up with:

|DATA EXPORTED FROM HORNRESP - RESONANCES NOT MASKED

|COMMENT: Beyma 18P80/Nd Tapped horn 700L EPA

|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~

|REQUIRED AKABAK SETTINGS:

|File > Preferences > Physical system constants:

|Sound velocity c = 344m/s
|Medium density rho = 1.205kg/m3

|Sum > Acoustic power:

|Frequency range = 10Hz to 20kHz
|Points = 533
|Input voltage = 2.83V rms
|Integration = 2Pi-sr
|Integration steps = 1 degree ... 1 degree
|Integration method = Cross

|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~

Def_Const |Hornresp Input Parameter Values
{
|Length, area and volume values converted to metres, square metres and cubic metres:

S1 = 252.00e-4; |Horn segment 1 throat area (sq m)
S2 = 833.00e-4; |Horn segment 1 mouth area and horn segment 2 throat area (sq m)
S3 = 1095.00e-4; |Horn segment 2 mouth area and horn segment 3 throat area (sq m)
S4 = 1571.00e-4; |Horn segment 3 mouth area and horn segment 4 throat area (sq m)
S5 = 1190.00e-4; |Horn segment 4 mouth area and horn segment 4 throat area (sq m)
S6 = 1761.00e-4; |Horn segment 5 mouth area and horn segment 4 throat area (sq m)
S7 = 2570.00e-4; |Horn segment 6 mouth area and horn segment 4 throat area (sq m)
S8 = 1999.00e-4; |Horn segment 7 mouth area and horn segment 4 throat area (sq m)
S9 = 2047.00e-4; |Horn segment 8 mouth area and horn segment 4 throat area (sq m)
S10 = 3046.00e-4; |Horn segment 9 mouth area and horn segment 4 throat area (sq m)
S11 = 2245.00e-4; |Horn segment 10 mouth area and horn segment 4 throat area (sq m)
S12 = 2475.00e-4; |Horn segment 11 mouth area and horn segment 4 throat area (sq m)
S13 = 2951.00e-4; |Horn segment 12 mouth area and horn segment 4 throat area (sq m)
S14 = 3998.00e-4; |Horn segment 13 mouth area (sq m)

L12 = 30.00e-2; |Horn segment 1 axial length (m)
L23 = 40.00e-2; |Horn segment 2 axial length (m)
L34 = 10.00e-2; |Horn segment 3 axial length (m)
L45 = 10.00e-2; |Horn segment 4 axial length (m)
L56 = 85.00e-2; |Horn segment 4 axial length (m)
L67 = 21.00e-2; |Horn segment 4 axial length (m)
L78 = 21.00e-2; |Horn segment 4 axial length (m)
L89 = 10.00e-2; |Horn segment 4 axial length (m)
L910 = 21.00e-2; |Horn segment 4 axial length (m)
L1011 = 21.00e-2; |Horn segment 4 axial length (m)
L1112 = 1.20e-2; |Horn segment 4 axial length (m)
L1213 = 38.00e-2; |Horn segment 4 axial length (m)
L1314 = 33.00e-2; |Horn segment 4 axial length (m)

Ap1 = 1225.00e-4; |Throat chamber port cross-sectional area (sq m)
Lpt = 1.80e-2; |Throat chamber port tube length (m)

Vtc = 2200.00e-6; |Throat chamber volume (cubic m)
Atc = 1225.00e-4; |Throat chamber cross-sectional area (sq m)

|Parameter Conversions:

Sd = 1225.00e-4; |Diaphragm area (sq m)

Ltc = Vtc / Atc;
}
|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~

|Network node numbers for this tapped horn system:

| 0-Voltage-1
| |
| -Port-4-Chamber-5-Driver-
| | |
|8-Segment-9-Segment-10-Segment-11-Segment-12-Segment-13-Segment-14-Segment-15-Segment-
|16-Segment-17-Segment-18-Segment-19-Segment-20-Segment-21-Radiator

|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~

Def_Driver 'Driver'

Sd=1225.00cm2
Bl=21.90Tm
Cms=1.93E-04m/N
Rms=2.34Ns/m
fs=30.00Hz |Mmd = 121.16g not recognised by AkAbak, fs calculated and used instead
Le=1.90mH
Re=5.10ohm
ExpoLe=1

System 'System'

Driver Def='Driver''Driver'
Node=1=0=5=20

Duct 'Throat chamber'
Node=4=5
SD={Atc}
Len={Ltc}
Visc=0

Duct 'Port'
Node=4=9
SD={Ap1}
Len={Lpt}
Visc=0

Waveguide 'Horn segment 1'
Node=8=9
STh={S1}
SMo={S2}
Len={L12}
Conical

Waveguide 'Horn segment 2'
Node=9=10
STh={S2}
SMo={S3}
Len={L23}
Conical

Waveguide 'Horn segment 3'
Node=10=11
STh={S3}
SMo={S4}
Len={L34}
Conical

Waveguide 'Horn segment 4'
Node=12=11
STh={S5}
SMo={S4}
Len={L45}
Conical

Waveguide 'Horn segment 5'
Node=12=13
STh={S5}
SMo={S6}
Len={L56}
Conical

Waveguide 'Horn segment 6'
Node=13=14
STh={S6}
SMo={S7}
Len={L67}
Conical

Waveguide 'Horn segment 7'
Node=15=14
STh={S8}
SMo={S7}
Len={L78}
Conical

Waveguide 'Horn segment 8'
Node=15=16
STh={S8}
SMo={S9}
Len={L89}
Conical

Waveguide 'Horn segment 9'
Node=16=17
STh={S9}
SMo={S10}
Len={L910}
Conical

Waveguide 'Horn segment 10'
Node=18=17
STh={S11}
SMo={S10}
Len={L1011}
Conical

Waveguide 'Horn segment 11'
Node=18=19
STh={S11}
SMo={S12}
Len={L1112}
Conical

Waveguide 'Horn segment 12'
Node=19=20
STh={S12}
SMo={S13}
Len={L1213}
Conical

Waveguide 'Horn segment 13'
Node=20=21
STh={S13}
SMo={S14}
Len={L1314}
Conical

Radiator 'Horn mouth'
Node=21
SD={S14}


I tried to take the corner bends into account, but I'm not sure I did it correctly .

Here's the graph:

Click the image to open in full size.

Any suggestions are welcome
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