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My Sub-Low Reflex Project
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wafflesomd View Drop Down
Young Croc
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Joined: 21 September 2007
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Points: 811 		Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 16 September 2008 at 12:57am
Start the builds!

I wanna see these monsters.
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gratzi View Drop Down
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Points: 58 		Post Options Post Options   Thanks (0) Thanks(0)   Quote gratzi Quote  Post ReplyReply Direct Link To This Post Posted: 16 September 2008 at 4:20pm
Originally posted by Elliot Thompson Elliot Thompson wrote:


Beyma 18 SW 1600ND



what price does this driver reaches ? Confused....and where you can buy these driver?...i heard it`s only a prototype for the moment...i didn`t knew it wass lauched for mass production..


Edited by gratzi - 16 September 2008 at 4:23pm
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Elliot Thompson View Drop Down
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Joined: 02 April 2004
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Points: 5365 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 16 September 2008 at 8:44pm
Originally posted by gratzi gratzi wrote:

Originally posted by Elliot Thompson Elliot Thompson wrote:


Beyma 18 SW 1600ND



what price does this driver reaches ? Confused....and where you can buy these driver?...i heard it`s only a prototype for the moment...i didn`t knew it wass lauched for mass production..


In the States, there is a store that is advertising it as "Coming Soon." If it performed better than the 21 L50 in my cabinets, I would have waited.

I'll need to wait nevertheless for the 21 L50's. The shop I visited will need to special order two for me.

Best Regards,


Edited by Elliot Thompson - 16 September 2008 at 9:07pm
Elliot Thompson
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Young Croc
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Joined: 21 July 2008
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Points: 1164 		Post Options Post Options   Thanks (0) Thanks(0)   Quote H... Quote  Post ReplyReply Direct Link To This Post Posted: 16 September 2008 at 9:25pm
Do you drive a V8?
 
 
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Elliot Thompson View Drop Down
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Points: 5365 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2008 at 12:51pm

With the economy turning into complete rubbish in the States, spending nearly $2000.00 on a project that is not necessary, would be an idiotic thing to do. So, I'm going to put this design on hold for now.

As I mentioned in my previous post bass, was never an issue so, this type of splurge can wait.

Best Regards,

Edited by Elliot Thompson - 18 September 2008 at 12:55pm
Elliot Thompson
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wafflesomd View Drop Down
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Points: 811 		Post Options Post Options   Thanks (0) Thanks(0)   Quote wafflesomd Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2008 at 6:05pm
Whereabouts are you located in the states?
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Elliot Thompson View Drop Down
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Points: 5365 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 18 September 2008 at 8:45pm
Originally posted by wafflesomd wafflesomd wrote:

Whereabouts are you located in the states?
 
New York.
 
Best Regards,
Elliot Thompson
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Kumruz View Drop Down
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Originally posted by Elliot Thompson Elliot Thompson wrote:



Volume Displacement Comparison

If you haven’t read Rog’s notes in regards to Volume Displacement hear it is:

Quote Originally Posted By Rog Mogale


Vd: Displacement volume.

Also something you catch from people with an appetite for drivers over 24”. Vd is Sd x xmax. It’s often overlooked but if moving lots of air at low frequencies is your game then you should know about it. I’ve put the parameter here after Sd and xmax because it ties in with both of these. Basically to make sound you need to move air, and the lower the frequency you are trying to reproduce the more air you will have to move for a given output. You can do this with larger cones, which will give you more Sd, or you can do it with smaller cones that move in and out more (have more xmax). So an 18” driver with an Sd of 1150 sq cm and an xmax of 5 mm can move 5750 cubic centimetres (cc) of air. Think of it like a big scoop that will hold 5750 cc of air and then get some one to throw that air at you very quickly and repeatedly, that’s a speaker. Now take a driver like the Precision Devices PD 1850, it has 11.25 mm of xmax and an Sd of 1150 sq cm. So its Vd would be 12,975 cc. Throwing 12,975 cc of air at someone is going to hurt a lot more than 5750 cc of air. Some of you will have noticed than 12,975 is over double 5750, now can you start to see why I rant on about drivers like the PD 1850. Comparing Vd figures is very useful for working out how much bass a driver can produce and is something most people don’t do.


It seems some brands use a two times method where some do not. Pretty much like the measurement of xmax. Some say plus minus while another will say one way. I’m going to use the two times method to prevent any confusion among the drivers.

Peavey Low Rider 18 = 2375 (4752 for two drivers) cc

Beyma 18 SW 1600ND = 2510 (5020 for two drivers) cc

Beyma 21 L50 = 3200 (6400 for two drivers) cc

Amplifier Tone Burst and Speaker Tolerance

With all old Crown amplifiers, there is a Maximum Power chart located in their instruction booklet. While many feel this graph is useless, I do not. It tells you how much wattage the speaker is getting with high dynamic material. Pulses can destroy a driver just as fast as a long-term continuous signal. The Maximum Power listed on a 4 ohm load is 3220 watts 1 KHz @ 0.05% THD and, 2310 watts 50 Hertz 0.05% THD. I’m going to use 3220 watts for the THD is very low and, at 1% THD it is highly possible 100 – 20 Hz will favour the 1 KHz analysis.

I’ve also added my Double Eighteens to compare. The Lavender line will be the Beyma G 550s I’m currently using and, used as a benchmark when I started the whole project.


I’m using Cone Displacement different than how Eminence Designer/Bass Box Pro suggest. With Cone Displacement, it measures the linear movement and darkens the offending line that exceeds its linearity. What I want to know is how much xmax is used before it approaches its xmech limit.

I will more than likely never feed each driver 1610 watts, but for the idiot who boosts the fader from 6 – full on my mixer, I need to know where the woofers will stand.





As we can see the Peavey has encountered some difficulty, and begins to go into compression dropping 1 dB from 134 – 133 decibels. The xmax is the highest amongst all three offering a peak of 16.6 mm @ 40.1 Hz.

Next, is the Beyma 18 SW 1600ND, which maintains its consistency, delivering 133 decibels from 27.9 – 100 Hz. The xmax peaks at 14.1 mm @ 38 Hz. With a one-way peak of 30 mm there is still ample amount of headroom.

We now look at the Beyma 21 L50. This driver still showing it’s class having no difficulty to handle the power. It delivers 134 decibels from 100 – 27.4 Hz in addition offering the lowest xmax out of the two contenders. The one-way xmech is 17.5 (or 35mm Peak to Peak) mm. Its highest peak receiving 1610 watts (3220 for two woofers) is 11.9 mm @ 41.6 Hertz.

The Beyma 18 SW 1600 ND has more leeway than the 21 L50 however we must take the Volume Displacement into consideration here.


Beyma 18 SW 1600ND = 2510 (5020 for two drivers) cc

Beyma 21 L50 = 3200 (6400 for two drivers) cc


The 21 L50 offers 690 cc over the 18 SW 1600ND. In addition to having the ability to deliver 134 decibels at 27.4 Hz whereas, the 18 SW 1600ND offers 133 decibels @ 27.9 Hertz.

So, the 21 L50 is the best choice for my Sub-Low Reflex cabinet.

I will now move on to the next stage, which will be cabinet construction.


Regarding


Volume Displacement Comparison I think that theres error in calculation of VD because if cone surface is 1100cm2  and xmax is 5mm thats 1100cmx0,5cm=550ccm
one liter is 1cubic decimeter  thats 10x10x10cm=1000ccm
also if surface 1100 and xmax 12mm thats 1100x1,2=1320ccm (1.32liter)

Why not consider RCF drivers?
size does matter(to my back and to my wife)
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Elliot Thompson View Drop Down
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Joined: 02 April 2004
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Points: 5365 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 26 September 2008 at 12:34pm
Kumruz,

Beyma drivers perform better in reflex cabinets than RCF for my requirements. There is another brand at the moment that exceeded Beyma's performance (Thanks Deadbeat for bringing it to my attention) however, they are still in the process of getting distributers. Which is fine for me. As I mentioned the economy is rubbish in the States (I guess they are too proud to say that we are in a recession) so, I'm holding off until things get better.

As for the error in the calculation, that is something you will need to take up with Rog.

Best Regards,
Elliot Thompson
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_radu View Drop Down
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Points: 14 		Post Options Post Options   Thanks (0) Thanks(0)   Quote _radu Quote  Post ReplyReply Direct Link To This Post Posted: 06 October 2008 at 4:39pm
Hi Elliot,

Anything new with the cabs ? Pictures maybee ? :)
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Elliot Thompson View Drop Down
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Joined: 02 April 2004
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Points: 5365 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 07 October 2008 at 10:20pm
Originally posted by _radu _radu wrote:

Hi Elliot,

Anything new with the cabs ? Pictures maybee ? :)


Hello radu.

The economy is getting worse in the States. I'm waiting for things to start picking up before I invest in such a project.

Best Regards,
Elliot Thompson
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aperrado View Drop Down
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Points: 315 		Post Options Post Options   Thanks (0) Thanks(0)   Quote aperrado Quote  Post ReplyReply Direct Link To This Post Posted: 08 October 2008 at 5:16am

hey guys I need help to get the volume and wood thickness for a gsub,  I think it is nothing to see with this post but watching the grafics I think u can help me  I tried winisd but I cant use it
Im hard to learn but still asking
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