Beyma SB18 driver |
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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Do you mean the measurement of the Jobst MBH-118? So you think, that it's not the same design as the Beyma SB18? Refering to my simulation of the SB18 I would also aspect more kick...? http://www.speakerplans.com/forum/forum_posts.asp?TID=26592&PID=281834&title=beyma-sb18-driver#281834 Why do you think, that it's not suited for stand alone use? Do such designs take benefit at the low end by stacking them? Do you know something about the following cab design? http://www.jobst-audio.de/Nachbauten/aw-mtl/awmtl.htm greez |
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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Seems that the Jobst MBH-118 has a lower tuning frequency than the Beyma SB18-1
Beyma SB18-1 - Impedance Jobst MBH-118 - Impedance Is tat the reason why you expect less effiency at the low end/more kick from the Jobst Hybrid? |
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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Wow, the AW-MTL loaded with the low budged Eminence Kappa 15LFA driver is a sly old dog!
Convince yourselves! black = Beyma SB15-1 grey = AW-MTL black = Beyma SB18-1 grey = AW-MTL |
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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Another simulation in which I have changed the drivers of both designs with each other...
black = AW-MTL - Beyma 15P1200Nd grey = Beyma SB15 - Eminence Kappa 15LFA |
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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Someone said, that the Beyma cab is the same as the Electro Voice...
Here are the simulation results: black = Beyma SB18-1 - 18P1200Nd grey = EV T18 - EVX180B black = Beyma SB18-1 x2 - 18P1200Nd grey = EV MTL-1X - EVX180B cheers |
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mobiele eenheid
Old Croc Joined: 15 August 2004 Location: Netherlands Status: Offline Points: 1568 |
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They're both hybrides but likely different hybrides, thus with different performance.
As you might now these hybrides can be described and explained from different perspectives, which will have a certain overlap with each other. It can be described as a rear loaded band pass horn (RLBPH), a tapped horn with a large chamber and a short horn, a reflex cabinet (BR) with an unusual large port and even a band pass device (BP) with a roll off in both the high and low frequency response.
As all RLBPH it will have a dip in the frequency reponse derived from the half wavelength cancelation. Scoops hace long horns, which causes this cancelation usually to take place just beneath 100 Hz. Shorter horns such as these RLBPH will thus have a cancelation between 150 and 250 Hz. Having such a dip in the area that represents the "higher kick" make these enclosures less suitable for kick (at least in my view). By the way: This dip get's smaller as you stack more cabinets
As you can see at the measurement of the MBH-118 this dip is above 200 Hz, whilst mine prototypes similar to the SB18 showed this dip to start around 160 Hz. Because the MBH-118 extends higher I would think it to be more suited for reproducing the "kick".
Because the MBH-118 shows an ever falling response and the SB18 look-a-like prototype is pretty flat from 50 Hz and up I aspect the SB18 more suited for stand alone use. Also because most horn cabinets are either good kick-cabinets or good bass cabinets but usually not both (seen from the BP-perspective).
A cabinet will have constructive interference with similar cabinets as long as it's placed within 1/4-wavelength of any reproduced frequency. A BR-cabinet however doesn't show a significant improvement in it's low frequency reponse such as a RLBPH would. Being in the midst of a BR and a RLBPH, it's feasible to say the improvement in low frequency response should be better as an BR but not as good as a RLBPH.
The last cabinet you introduced is about 250 liter (IIRC) whereas the SB15 from my memory is at least 65 liters smaller. Such a difference can well be responsible for the difference showed in the simulations.
Best regards Johan Edited by mobiele eenheid - 02 July 2009 at 7:40pm |
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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Johan, thank you for the detailed and colorful description!!!
I think I should hand in the cab sizes later to complete the comparision:
Beyma SB15 - 43x50x73 - 157 litre
Beyma SB18 - 54x54x79 - 231 litre
Jobst MBH-118 - 58x58x74 - 249 litre
AW-MTL - 65x60x66 - 257 litre
EV T18 - 62x80x60 - 298 litre
EV MTL-1X - 116x57x75 - 496 litre
cheers
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TDA-Audio
Registered User Joined: 11 February 2005 Location: Russian Federation Status: Offline Points: 294 |
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to Ibex
please on these systems graph 1/2 EV MTL-1X - EVX180B (1x18") and EV T18 - EVX180B can be a project MBH-118 copy 1/2 EV MTL-1X ???? |
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horns plans http://photofile.ru/users/tda-audio/
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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For sure, TDA! black = EV MTL-1X grey = EV T18 x2 black = 1/2 EV MTL-1X grey = EV T18 black = 1/2 EV MTL-1X - L18S800 grey = 1/2 EV MTL-1X - EVX180B Jobst MBH-118 - RCF L18S800 - SPL 1/2 EV MTL-1X - L18S800 Jobst MBH-118 - RCF L18S800 - Impedance Dimensions: Jobst MBH-118 - 58x58x74 - 249 litre 1/2 EV MTL-1X - 58x57x75 - 248 litre TDA, I think so too... suspicious congruent! It would be also very interesting to compare these designs together with some real Tapped Horn designs! What do you think? cheers |
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Ibex
Young Croc Joined: 27 May 2009 Status: Offline Points: 1013 |
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For example:
black = Beyma SB18 - Beyma 18P1200Nd - 54x54x79 - 231 litre grey = Staiper Tapped - B&C 15TBX100 - 63x80x60 - 302 litre black = Beyma SB15 - Beyma 15P1200Nd - 43x50x73 - 157 litre grey = Staiper Tapped by TDA - B&C 12NW100 - 38x80x60 - 182 litre In both cases the low cut-off frequency is allmost the same, but the RLBPH designs have the smaller enclosure. The second peak of the real tapped horns is narow beyond 100Hz. The RLBPH have this peak @ 160Hz, this peak envelopes the upper slim ones of the tapped designs.... Bloody similar, but the tapped designs have more interferences (more slim peaks, more pronounced comb filter effect). Would be interesting how both designs sound... Did anyone compare such designs together and knows how they sound? Did anyone measure the frequency response of both designs? greez |
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jethrocker
Old Croc Joined: 07 June 2006 Location: Chiapas, Mexico Status: Offline Points: 1942 |
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Ibex..worth noting that according to most of the tapped horns built and measured (best place to see tapped horn project results is diyaudio.com forum) to date the reports are that the actual response isn't so spiky at the upper end and is somwhat filtered, generally being more alike to the RLBPH plots you posted.
Thanks for the posts, interesting comparisons :) |
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KenTech
Registered User Joined: 05 December 2006 Status: Offline Points: 133 |
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can u post the Data for building SB18-1 Cab ?
those angles inside... and the lenght of some boards, inside... 10x What about the comparison between ES18 BPH and Beyma SB18-1 ? Loaded with the same driver, Paudio C18-ELF. Edited by KenTech - 04 July 2009 at 2:04pm |
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