What type of cabinet for this speaker? JBL 127H - diyAudio
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Old 9th July 2007, 02:33 AM   #1
Klook is offline Klook  Brazil
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Default What type of cabinet for this speaker? JBL 127H

Hello everybody,

I would like to build a cabinet for the following speaker (used as subwoofer):

Click the image to open in full size.

It will be cut around 70 - 100 Hz and used in a small room about 13m2 (140 ft2)

Any suggestions will be wellcome!

best regards
Leo
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Old 9th July 2007, 04:18 AM   #2
Foxx510 is offline Foxx510  Australia
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If you download winisd from this site, you can try different boxes and see the outcome. That JBL driver is in the database.
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Old 9th July 2007, 10:09 PM   #3
Klook is offline Klook  Brazil
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Thank you!!
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Old 10th July 2007, 07:19 PM   #4
Klook is offline Klook  Brazil
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Join Date: Jun 2007
Guys,
I have few questions about subwoofer enclosure designs.

I have used the software above (and the tips located under diysubwoofers.org).

Ok, I found something around 140 liters (36.98 gallons, 4.944 ft3).
I also got the following frequency response:

Click the image to open in full size.

The cutoff freq is 40 Hz. What it means? Do I have to set the XO to cut the subwoofer in this frequency? What happens if I cut above? Around 80hz?

I also realized that all these calculations don't consider the room size.
What happen with the Enclosure + Driver + Room size integration?
If my room is small I think that it has different needs than large rooms.

The software above also gave me the cabinet dimensions. I was thinking build the enclosure like this:

Click the image to open in full size.

This way I can test some driver positions in relation to the floor:

Click the image to open in full size.

What do you think about this design?

Finally, I have made a Sketch-Up model to see how it would looks like:

Click the image to open in full size.

Click the image to open in full size.

Thank you for any help and suggestions.

best regards
Klook
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Old 10th July 2007, 07:45 PM   #5
sreten is offline sreten  United Kingdom
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Location: Brighton UK
Hi,

What your modelling reveals is its not really a subwoofer driver.
You should be able to use a 12" driver in 1 to 2 cuft sealed.

If you build it, the main thing is its big but doesn't need much power.

Cause of all this is low MMS for a 12", for a sub you want much higher.

/sreten.
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Old 11th July 2007, 01:18 AM   #6
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Location: Indiana
Box is too small if I read the params right. Vas is 8.4 ft^3. Box plot models nice EBS in about 15-17 ft^3 very solid below 20Hz. Just on a quick glance it seems that a look at a TL would be in order but much more complicated.

mike
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Old 11th July 2007, 06:27 AM   #7
Klook is offline Klook  Brazil
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Thank you Guys,

You mean that the 40Hz is the lowest frequency this "subwoofer" can reach in the 140 liter enclosure?

If I build a TL this cutoff will be decreased?
The problem is that my main speakers are high-efficient full-range speakers and a TL could lower de SPL of the subwoofer.

What would be the right direction now? Change de driver?

best regards
Klook
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Old 11th July 2007, 10:21 AM   #8
sreten is offline sreten  United Kingdom
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Location: Brighton UK
Hi,

What matters in a subwoofer for maximum levels is cone area times
excursion and whether it is vented or sealed. Then what matters is
having enough juice to drive the driver to its excursion limits.

With a subwoofer and room gain around -10dB is the practical bass limit.

Download WinISDpro alpha - its much better than beta add you can
explore the above issues. You will need to create a file for the driver.

/sreten.
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Old 16th July 2007, 07:11 PM   #9
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i very high Vas, i must say

i too ran the specs in WINisd
Klook [] is all correct, sealed enclosure 140litres which i know is too much, lower 3db freq 40hz as Klook [] said

1 thing for sure u cant use it in sealed enclosure, else u'll need 300litres....

40Hz is not the least freq. that you'll hear in sealed enclosure
Klook[] u'll have half the max power at 40hz, loss of 3db
1/4th of max power at 31hz, means loss of 6db

so i think it will give a decent responce till 30hz,
final advice, this 150 litres to large(unless its too powerfull with 400rms wattage), Vas is large, speaker is not so nice, consult some other guys before u start or look for a new sub.

hop this could be of use to you,regards
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