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Beyma SB18 driver
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Ibex View Drop Down
Young Croc
Young Croc


Joined: 27 May 2009
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Points: 1013 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Ibex Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2009 at 8:09am
Originally posted by Crashpc Crashpc wrote:

I did different box. The size is 55x60x72 centimetres (WxHxL)
I did better angle between speaker and the wall opposite it, so the shape of the horn is more opening. I did only impedance measurement. It was tuned at 50Hz. It really does not go as deep as bassreflex, but it is not noticable in normal music (i like deep bass), but it was noticable louder with better kick especially when you cut it at 150Hz :-)
There is a bit problem with the wall against the speaker - resonating too much when you push 1000W to the speaker. So I left this construction, and I get some similar, but with no "speaker against wall" because this is not any good.
 
resonating wall opposite the driver - maybe it would have been better to build the cab with MDF or birch multiplex. I also think that your wall-resonating-problem was the reason why beyma designed the opposite wall double the thickness...
Good idea to increase the flare rate at the range from the driver position down to the mouth!
I guess the design should take benefit of your modification of a slightly higher tuning frequency attended with a bit higher effiency of the lower tapped-effect peak... Question
It's a pity that you are not satisfied with this design and you will change to another! Cry
no speaker against wall will imply less tapped effect and less effiency... Wink
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Young Croc
Young Croc


Joined: 26 February 2008
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Points: 539 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2009 at 9:07am
I will build it with multiplex, but I tried many enclosures to try what do I like...
The sound of beymasub is cool, but the enclosure itself isn't.
You have to double the thickness of both sides opposite to the speaker, so it makes this enclosure much more heavy. I wanted smallish light cab. If I can't, Ill make bigger, with better efficiency anyway.

Yes. I tried this idea not only for mechanical problems, but the tuning end efficiency, because 18" bass speaker can go deep enaugh for me anyway (if not placed in horn).
I think I'll do something like this:
http://swdradio.iczy.info/service/speaker/RCF_Bassbin.jpg
The Stove :-)


Edited by Crashpc - 01 July 2009 at 9:08am
Nikon and Canon people should not be married to each other. Why did you let this happen?
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Ibex View Drop Down
Young Croc
Young Croc


Joined: 27 May 2009
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Originally posted by Crashpc Crashpc wrote:

I will build it with multiplex, but I tried many enclosures to try what do I like...
The sound of beymasub is cool, but the enclosure itself isn't.
You have to double the thickness of both sides opposite to the speaker, so it makes this enclosure much more heavy. I wanted smallish light cab. If I can't, Ill make bigger, with better efficiency anyway.

Yes. I tried this idea not only for mechanical problems, but the tuning end efficiency, because 18" bass speaker can go deep enaugh for me anyway (if not placed in horn).
I think I'll do something like this:
http://swdradio.iczy.info/service/speaker/RCF_Bassbin.jpg
The Stove :-)
 
as I said before: driver nearer the mouth, higher flare rate @ this position --> less tapped effect, less effiency in the lowest range (1. tapped-effect peak), works more like a ARLS (or like a short path scoop with large chamber)
 
have you already build a test enclosure of the rcf bass bin? how does it sound compared to the beyma sb15?
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Young Croc
Young Croc


Joined: 26 February 2008
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Points: 539 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2009 at 10:49am
No I didn't. I built something different with straight mounted speaker.
http://www.repromania.net/projekty-pa/sub-mt18sub-bc-18pzb46.php
http://www.repromania.net/fotografie/projekty-pa/sub-mt18sub-bc-18pzb46/sub-18-mt18sub-08.jpg
It sounds nice too, but too much bassy and less kicky :-) So I try RCF bassbin or something like this...
It has better and longer horn part of the bin... So less tapped effect, more horn effect...


Edited by Crashpc - 01 July 2009 at 10:49am
Nikon and Canon people should not be married to each other. Why did you let this happen?
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Young Croc
Young Croc


Joined: 27 May 2009
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Points: 1013 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Ibex Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2009 at 11:06am
Originally posted by Crashpc Crashpc wrote:

No I didn't. I built something different with straight mounted speaker.
http://www.repromania.net/projekty-pa/sub-mt18sub-bc-18pzb46.php
http://www.repromania.net/fotografie/projekty-pa/sub-mt18sub-bc-18pzb46/sub-18-mt18sub-08.jpg
It sounds nice too, but too much bassy and less kicky :-) So I try RCF bassbin or something like this...
It has better and longer horn part of the bin... So less tapped effect, more horn effect...
 
I would classify the Megaton MT 18 SUB as a conventional reflex loaded cab with a big and therewith long port to get a low tuning frequency. no horn or neither tapped effect.
I think the RCF bassbin would achieve your requirements of sounding more kicky, as you already said: more horn effect!
Good success and I hope you will be satisfied with the cab!
cheers
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_djk_ View Drop Down
Old Croc
Old Croc


Joined: 23 November 2004
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Post #5
The 'specifications' on that box are pure fiction.

It will only be 101dB above 100hz, and it will be at least 10dB down at 33hz.

It's similar to this EV cabinet, but can't work as well as it's smaller.

http://archives.telex.com/archives/...0L-ER%20EDS.pdf

But on the other hand, many people are satisified with the EV, so you may be satisfied with yours.

Keep in mind:

A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).

The 'horn' on the EV/Beyma is too short to work below 100hz, and the rear volume acts as a vented box below 100hz (and it is tiny).

Note: the correction factor between 2.83V/1M and 4V/10' is +6.67dB

The Beyma is only 2/3 the total size of the EV, so it must be almost 2dB less efficient below 50hz.



Edited by _djk_ - 01 July 2009 at 11:09am
djk
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Young Croc
Young Croc


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Points: 539 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2009 at 11:26am
Ibex: There wouldn't be any reason to build it like this when you do not get any added sensitivity. You can easily build a bassreflex cab with 160l volume behind the speaker, and the overall volume of the bassreflex box will be smaller.
So they build it for some reason. I guess it has some bas enhancement near 100Hz. If people play some bigbeat or hardrock, I guess they cut it at 120-150Hz, so they get that few decibel peak to have a bit kicky bass, cause they do not need 30Hz, even 40Hz maybe not...

djk:
Well I don't care - I need some bassbin with better kick than standard bassreflex cabs, no matter if it is one decibel up or down. I tried this beymasub with QSC RMX1850HD on the firehouse party, and we did not need any bridging. We had to go down to -6db to stop CD players shaking and skipping, because antishock of the players was unable to work when it was turned all the way LOUD..... There would be different situation when we play open air, but I really don't think I need the last decibel possible.
I do not need 33Hz, I need 45Hz and up...
I think there is not only better or stronger bin or bad bin. There are many cabs YOU LIKE and YOU DO NOT LIKE, so against all theory, you can decide for the worse cab only because it is smaller, or lighter, or you like the sound. Do not look only at decibel counts.
Nikon and Canon people should not be married to each other. Why did you let this happen?
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Young Croc
Young Croc


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Crashpc, may I refer you to that link:
 
_djk_, do you know this cab?
looks bloddy similar, what do you think? can you expect the same "kicky" sound from this cab as from the Beyma SB18?
 
Along the way perceived, I have to agree Cashpc's argumentation, I think these cabs are not designed to go load at the low end, IMHO they are rather to extend the frequency range of an infra-sub with a kickbass response and a little bit low end... infra and hybrid designs are currently very popular, regardless if they are the most efficient solution.
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Young Croc
Young Croc


Joined: 27 May 2009
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Beyma SB18 loaded with the MBH-118 driver... I think the designs are 1:1
 
Beyma SB18 - Beyma 18P1200Nd vs. RCF L18S800 - SPL
black = Beyma SB18 (or Jobst MBH-118) - RCF L18S800
grey = Beyma SB18 (or Jobst MBH-118) - Beyma 18P1200Nd
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mobiele eenheid View Drop Down
Old Croc
Old Croc


Joined: 15 August 2004
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Points: 1563 		Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2009 at 4:52pm
Quote So they build it for some reason. I guess it has some bas enhancement near 100Hz. If people play some bigbeat or hardrock, I guess they cut it at 120-150Hz, so they get that few decibel peak to have a bit kicky bass, cause they do not need 30Hz, even 40Hz maybe not...
I've build, simulated and measured quite a few hybride's like the SB18, some conclusions up till now:
 
An Eminence Kappa 15LF in the SB18 will beat or equal an 18" basreflex (18LW1400) of similar size from 50 Hz and up (up till the point were the bigger VC from the 18" will dominate it's effects). Compared with an Kappa 15LF in a 110 liter enclosure tuned to 42 Hz, it can be 6 dB more efficient at 120 Hz and up.
 
It measures and sounds like a 6th order bandpass, I prefer to cross them low (80-125 Hz low pass). Above 160-210 Hz (model dependant), they drop like a rock, never to recover.
 
It simulates quite well, it measures better. It's a 40 Hz and up bin. From 50 Hz and up it's quite flat.
 
Best regards Johan


Edited by mobiele eenheid - 01 July 2009 at 4:53pm
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Young Croc
Young Croc


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Originally posted by mobiele eenheid mobiele eenheid wrote:

 
Compared with an Kappa 15LF in a 110 liter enclosure tuned to 42 Hz, it can be 6 dB more efficient at 120 Hz and up.

It simulates quite well, it measures better. It's a 40 Hz and up bin. From 50 Hz and up it's quite flat.


Hi Johan, thanks for your comment!
Does that mean, that the big peak which is shown in my simulation around 160Hz will not be there in reality (of course without low pass)? Question
I already read something that the two peaks of a tapped horn simulation will be not as high in reality, but not that there will be no peak... Confused
greez
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Old Croc
Old Croc


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Points: 1563 		Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 01 July 2009 at 6:27pm
Quote looks bloddy similar, what do you think? can you expect the same "kicky" sound from this cab as from the Beyma SB18?
This looks similar to my first prototype hybride, though I can't see how long the horn path is. The first prototype was very loud but didn't sound as if it was going very low. The 2nd, 3th and 4th protoype look much more like the SB18. They do perform well enough to be used stand alone (even with dub step).
 
Looking at those measurements I would aspect more kick then a SB18, but less suited for stand alone use.
 
Quote Does that mean, that the big peak which is shown in my simulation around 160Hz will not be there in reality
The peaks will be there but in general the're less high and quite a bit wider (not always as sharp).
 
After it drops down at ~200 Hz I wouldn't aspect those "recovery" peaks.
 
Best regards Johan
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