Opinions on Enclosure Design (TL)

[schmeet]

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 0.1225m²
Terminus Area 0.0525m²

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

 

[planet10]

You should plug the T/S numbers into Martin King's tables as a 1st cut at a design.

dave

 

[schmeet]

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?

 

[planet10]

What are you using to model the TL?

dave

 

[schmeet]

Some software that I made. It seems pretty accurate but I don't have MJK's worksheet so I cant compare them.

 

[bjorno]

...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

 

[schmeet]

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.

 

[bjorno]

..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

 

[schmeet]

I don't fully follow what you have done to get the 'Suggested TL Volume' could you just run through that please?

Thanks..