Question about my first DIY project.

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pinkmouse said:
Prash,

I'm confused, I thought you said this box gave you a -3db at 52Hz, what has changed?:xeye:
 

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pinkmouse said:
Prash,

I'm confused, I thought you said this box gave you a -3db at 52Hz, what has changed?:xeye:

Sorry, the reply portion got cut off....

Ok here's what has changed. I reduced the box size to around 25 liters with a box tuning freq of 52 Hz. THIS has given me a
-3db point of 110 Hz. Previously the box was quite huge (about 40 liters) and Andy suggested that i reduce the volume and i also rechecked my calcs on SW and found that the volume needed to be reduced as well because there was a spike at around 50Hz ie., the box graph was not smooth as it should be.

But yesterday I was playing around with WinISD and SW and found that a box tuning freq of about 62 Hz made the box graph look much better with a -3db pt. at the box tuning freq of 65Hz or so. I dont know if this is good or if the tuning freq is too high to be practical. that's where i stand right now....

volume: 25 lt
Vas: 7.11
Qts: 0.38
Qes: 0.58
Qms: 1.09
Fs: 82 Hz
 

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Ex-Moderator
Joined 2002
Hi Prash,

Ok I reread the thread and am now up to speed again!:)

That tuning looks fine to me, and I can't see any problem, a quick look at Win isp online port calculator suggest that if you are using 18mm MDF, all you need is a hole 46 mm in diameter to tune to 62Hz, using the thickness of the timber as the port walls.
 
pinkmouse said:
Hi Prash,

Ok I reread the thread and am now up to speed again!:)

That tuning looks fine to me, and I can't see any problem, a quick look at Win isp online port calculator suggest that if you are using 18mm MDF, all you need is a hole 46 mm in diameter to tune to 62Hz, using the thickness of the timber as the port walls.


I am using 0.75 in MDF (which is about 19 mm). I have two ports each 2 inches in dia. (~50 mm each) though.
 
Ex-Moderator
Joined 2002
Ok, with 2x50mm vents each one should be 86mm long to tune to 62 Hz.

One thing you could try, although, I am not familar with any software that can simulate this, so it would be trial and error, is to try using staggered tuning.
This means tuning the two ports seperately to bring the f3 of the box lower. It might work, it might not:)

Have fun...
 
1. the tuning looks like an EBS tuning not bad per se but i find EBS to have a hangover on some bass passages. I played around with EBS using 2 8" focal woofers and the tuning was in the region of 40Hz or so.

The reason I am a bit vague with my replies is that I belive that a lot is to be done by ear. I would even venture out to use 2 different pot lengths and see what happens.

One expriment I used to do is take 3 different port lenghts (10cm, 14cm and 21cm) and change the port asking my friends to listen. they did not know which port was being used. funny we found that in teh same room, using teh same elctronics and speaker/box and port dia, different port lenghts sounded good for different music.

For a while I began cataloging my CDs with the port lenght that sonded best then i got a day job, bought too many CDs (now over 600), and gave up. Evtually I got so frustrated with getting the "exact" and "best" tuning for my entire CD collection that I swithced from bass reflex to sealed.

My next pair (8" active bass, 6" midbass, and 1" tweeter) discussed elsewhaere is also going to be sealed. However I am contemplating TL for the project that I will start after I finish this one.

Moral: You can have a lot of fun tuing the bass but dont let drive you nuts. After a while depending on your source and room you should decide on a port lenght or 2.
 
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