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Old 24th April 2012, 06:11 PM   #1
schmeet is offline schmeet  United Kingdom
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So I'm thinking about making a sub with an Eminence LAB12 driver.

Specs can be found here

My initial attempt at a design is for:
Length 3.2m
Mouth Area 0.1225m
Terminus Area 0.0525m

With a bit of stuffing to flatten out the peaks.

This should give a tuning frequency of around 20Hz.

For 300Watts the excursion peaks at around 28Hz and is about 11.5mm (one way). Which is below the xmax of 13mm.

Port velocity peaks at around 20Hz with around 5.5m/s which is acceptable.

Group delay seems to be around 35ms at 20Hz which isn't too bad but I would like it to be a bit less.

Frequency response looks flat from 80Hz down and is about-3dB at 20Hz.

SPL is about 110dB at 1m.


This is all based on my own calculations so I would appreciate any one else thoughts and comparisons..

Thanks,
Pete
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Old 24th April 2012, 06:52 PM   #2
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You should plug the T/S numbers into Martin King's tables as a 1st cut at a design.

dave
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Old 24th April 2012, 08:03 PM   #3
schmeet is offline schmeet  United Kingdom
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I've had a look at the alignment tables and it comes out with a similar length for my taper ratio but with a smaller volume (smaller So and SL).

But from my modelling software it has a bit more of a drop of down to 20Hz (not so flat) and has a higher port velocity.

Am I missing something?
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Old 24th April 2012, 08:11 PM   #4
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What are you using to model the TL?

dave
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Old 24th April 2012, 08:38 PM   #5
schmeet is offline schmeet  United Kingdom
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Some software that I made. It seems pretty accurate but I don't have MJK's worksheet so I cant compare them.
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Old 24th April 2012, 11:31 PM   #6
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by schmeet View Post
...Some software that I made. It seems pretty accurate but I don't have MJK's worksheet so I cant compare them...
Hi schmeet,

Good job! A quick check using one of MJK:s programs:

b
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File Type: gif Eminence_LAB12_OD-TL.GIF (48.9 KB, 109 views)
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Old 25th April 2012, 08:36 AM   #7
schmeet is offline schmeet  United Kingdom
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Thanks for that bjorno.

I've attached the FR output from my program for comparison. It seems to correlate pretty well (although the axis aspect ratio are very different so its hard to see).

It appears that the frequency response of my stuffing attenuation is a bit out though as I have slightly more low end attenuation and slightly less high end attenuation.

I guess the smaller volume TL would be good also with its main advantage being it is alot smaller! I think the terminus velocity would go too high though.
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File Type: jpg EminenceLAB12.jpg (39.4 KB, 95 views)
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Old 25th April 2012, 05:48 PM   #8
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by schmeet View Post
..I guess the smaller volume TL would be good also with its main advantage being it is alot smaller! I think the terminus velocity would go too high though..

Hi,

Agree, and if using a suitable ~20 Hz HPF the terminus velocity should stay lower than 10 m/s when reaching x-max.

Here is a suggestion more in line with a traditional TL design:


b
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Old 26th April 2012, 10:03 AM   #9
schmeet is offline schmeet  United Kingdom
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I don't fully follow what you have done to get the 'Suggested TL Volume' could you just run through that please?

Thanks..
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