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sounds4u View Drop Down
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    Posted: 21 December 2017 at 7:27am

Hi guys

I am trying to figure out the relationship between the vas of a speaker and box size.  in particular I have a 12" mid high cab that 55l but want to use a faital pro 12pr300 that has a vas of 79l.
Does this mean that the box size is too small for that driver and I should look for drivers with a vas around 55-60l.
 
Thanks 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote djkeet Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2017 at 10:12am
Prob best not to focus on one TS parameter but to get an idea how they all interact with each other in the first instance as VAS alone does not determine a good speaker enclosure
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2017 at 11:35am
Originally posted by sounds4u sounds4u wrote:

Hi guys

I am trying to figure out the relationship between the vas of a speaker and box size.  in particular I have a 12" mid high cab that 55l but want to use a faital pro 12pr300 that has a vas of 79l.
Does this mean that the box size is too small for that driver and I should look for drivers with a vas around 55-60l.
 
Thanks 


When you place a speaker in a cabinet smaller than its calculated VAS, you lose some of the low frequency extension the loudspeaker is capable of delivering. Many place loudspeakers in smaller than the recommended VAS requirements and use heavy equalisation to rectify the loss. This of course, forcethe loudspeaker to work harder, uses more xmax and, at times require more amplifier power to extract those lower notes.

Best Regards, 
Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sounds4u Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2017 at 12:10pm
So basically Elliot it has more to do with the lower frequencies being compromised. Am I right to say if you always running subs under and crossing over anywhere between 95hz to 110hz, it shouldn't be a problem then.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2017 at 12:31pm
Originally posted by sounds4u sounds4u wrote:

So basically Elliot it has more to do with the lower frequencies being compromised. Am I right to say if you always running subs under and crossing over anywhere between 95hz to 110hz, it shouldn't be a problem then.


You will have no issues. There may be an increase in cabinet gain in terms of SPL within the 100 Hz to 200 Hz region if the cabinet is extremely small in the eyes of the loudspeaker's VAS requirements. Many loudspeaker systems that offer a lot of SPL within the 100 Hz to 200 Hz region, with a significant loss below 60 Hz is due to the loudspeaker residing in a very small internal chamber. The average loudspeaker builder will call it "Boomy Bass." Under your conditions, such a phenomenon may go into your favour as, you will not need to focus on a lot of equalisation in terms of gain to attain a lot of SPL within the 100 Hz to 200 Hz region.

Best Regards,  


Edited by Elliot Thompson - 21 December 2017 at 12:35pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sounds4u Quote  Post ReplyReply Direct Link To This Post Posted: 21 December 2017 at 2:28pm
Thank you Elliot
 
in your opinion what other parameters should I be on the look out for when choosing a good 12 inch driver. the comp is also going to be from faital pro ( yet to choose).
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 22 December 2017 at 10:47am
Focus on the frequency response chart offered by Faital Pro. Observe how flat the curve is from 200 Hz to 2 kHz. Also observe at what frequency the high frequency roll off begins. A driver with a 3 inch voice coil will be more suited for midrange as it usually offers a higher high frequency cutoff point than a driver with a larger voice coil. The Le determines the high frequency roll off point from a TS Parameters standpoint.

Best Regards,
Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sounds4u Quote  Post ReplyReply Direct Link To This Post Posted: 22 December 2017 at 11:43am
Thanks Elliot
 
I want to run it active this time, I do have a dcx. Will I need to put any capacitor on the comp driver? the comp is going to be  beyma cd10fe.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote christth Quote  Post ReplyReply Direct Link To This Post Posted: 24 December 2017 at 8:54am
When running active crossover there will be no need for passiv filter components within the speaker, everything is done in the DCX. Some wants some kind off protective circuit for the HF though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Xoc1 Quote  Post ReplyReply Direct Link To This Post Posted: 24 December 2017 at 8:41pm
The Faital Pro 12 has a 3db roll off at 90hz in a 55 Litre box assuming that the box is sealed and not ported,
You could calculate the response using Hornresp. It now has a simple input box that allows you to enter the parameters easier.
http://www.hornresp.net/

The screenshot shows the roll off in a 55litre box
The grey line shows the same driver in half the volume 27.5L
This gives more output above 90 Hz than the 55L
This is why for a simple mid box often smaller is better.


Edited by Xoc1 - 24 December 2017 at 8:42pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 25 December 2017 at 8:01am
Originally posted by sounds4u sounds4u wrote:

Thanks Elliot
 
I want to run it active this time, I do have a dcx. Will I need to put any capacitor on the comp driver? the comp is going to be  beyma cd10fe.


I always use Capacitors on Compression Drivers that offer a 1 inch voice coil. It is just an extra safety precaution in the event the amplifier delivers an unexpected signal after the electronic crossover network.

Best Regards, 
Elliot Thompson
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