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2nd December 2012, 02:38 PM  #1 
diyAudio Member
Join Date: Nov 2003
Location: Maastricht

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/Edrum 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 edrum 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: 800 watts: Front loaded horn 650 L: 800 watts: Front loaded horn 700 L: 800 watts: 
2nd December 2012, 04:29 PM  #2 
diyAudio Member
Join Date: Apr 2010
Location: amsterdam

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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one good thing about music ,when it hit you feel no pain. so hit me with music. hr driver db 
2nd December 2012, 06:38 PM  #3  
diyAudio Member
Join Date: Nov 2003
Location: Maastricht

Quote:
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 1012 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 06:46 PM. 

2nd December 2012, 07:24 PM  #4 
diyAudio Member
Join Date: Apr 2010
Location: amsterdam

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 xmax 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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one good thing about music ,when it hit you feel no pain. so hit me with music. hr driver db 
2nd December 2012, 09:51 PM  #5  
diyAudio Member
Join Date: Nov 2003
Location: Maastricht

Quote:
Adjusting S2... something like this? (cr raised to 1.90:1) 800 watts: Quote:
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). 

4th December 2012, 03:19 PM  #6 
diyAudio Member
Join Date: Apr 2010
Location: amsterdam

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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one good thing about music ,when it hit you feel no pain. so hit me with music. hr driver db Last edited by epa; 4th December 2012 at 03:33 PM. 
4th December 2012, 05:33 PM  #7 
diyAudio Member
Join Date: Apr 2010
Location: amsterdam

here is a scetch
simple design. easy tuneable by cutting off the front bafle (red)eg mouth gets bigger and the hornpath shorter.
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one good thing about music ,when it hit you feel no pain. so hit me with music. hr driver db 
4th December 2012, 10:30 PM  #8 
diyAudio Member
Join Date: Nov 2003
Location: Maastricht

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 . 
5th December 2012, 05:43 AM  #9 
diyAudio Member
Join Date: Apr 2010
Location: amsterdam

hoi thijs
i use autocad, but people on this forum sugest sketchup. i wil check the exact measurments and a detailed drawing.
__________________
one good thing about music ,when it hit you feel no pain. so hit me with music. hr driver db 
5th January 2013, 09:28 PM  #10 
diyAudio Member
Join Date: Nov 2003
Location: Maastricht

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 = 2Pisr 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 = 252.00e4; Horn segment 1 throat area (sq m) S2 = 833.00e4; Horn segment 1 mouth area and horn segment 2 throat area (sq m) S3 = 1095.00e4; Horn segment 2 mouth area and horn segment 3 throat area (sq m) S4 = 1571.00e4; Horn segment 3 mouth area and horn segment 4 throat area (sq m) S5 = 1190.00e4; Horn segment 4 mouth area and horn segment 4 throat area (sq m) S6 = 1761.00e4; Horn segment 5 mouth area and horn segment 4 throat area (sq m) S7 = 2570.00e4; Horn segment 6 mouth area and horn segment 4 throat area (sq m) S8 = 1999.00e4; Horn segment 7 mouth area and horn segment 4 throat area (sq m) S9 = 2047.00e4; Horn segment 8 mouth area and horn segment 4 throat area (sq m) S10 = 3046.00e4; Horn segment 9 mouth area and horn segment 4 throat area (sq m) S11 = 2245.00e4; Horn segment 10 mouth area and horn segment 4 throat area (sq m) S12 = 2475.00e4; Horn segment 11 mouth area and horn segment 4 throat area (sq m) S13 = 2951.00e4; Horn segment 12 mouth area and horn segment 4 throat area (sq m) S14 = 3998.00e4; Horn segment 13 mouth area (sq m) L12 = 30.00e2; Horn segment 1 axial length (m) L23 = 40.00e2; Horn segment 2 axial length (m) L34 = 10.00e2; Horn segment 3 axial length (m) L45 = 10.00e2; Horn segment 4 axial length (m) L56 = 85.00e2; Horn segment 4 axial length (m) L67 = 21.00e2; Horn segment 4 axial length (m) L78 = 21.00e2; Horn segment 4 axial length (m) L89 = 10.00e2; Horn segment 4 axial length (m) L910 = 21.00e2; Horn segment 4 axial length (m) L1011 = 21.00e2; Horn segment 4 axial length (m) L1112 = 1.20e2; Horn segment 4 axial length (m) L1213 = 38.00e2; Horn segment 4 axial length (m) L1314 = 33.00e2; Horn segment 4 axial length (m) Ap1 = 1225.00e4; Throat chamber port crosssectional area (sq m) Lpt = 1.80e2; Throat chamber port tube length (m) Vtc = 2200.00e6; Throat chamber volume (cubic m) Atc = 1225.00e4; Throat chamber crosssectional area (sq m) Parameter Conversions: Sd = 1225.00e4; Diaphragm area (sq m) Ltc = Vtc / Atc; } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~ Network node numbers for this tapped horn system:  0Voltage1    Port4Chamber5Driver    8Segment9Segment10Segment11Segment12Segment13Segment14Segment15Segment 16Segment17Segment18Segment19Segment20Segment21Radiator ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~ Def_Driver 'Driver' Sd=1225.00cm2 Bl=21.90Tm Cms=1.93E04m/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: Any suggestions are welcome 
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