How to port?

[turn2]

For an initiation project I have acquired a pair of junked speakers, ditched the drivers but kept the nice MDF enclosures. I have chosen the Dayton 6.5" woofer (Part Number 295-305) for this 2-way bookshelf box.

The enclosures I have are sealed but I am interested in porting them. I do not believe I am restricted either way by my choice of woofer. However, I am pretty much at a loss at where to go with that wish.

I would like to use a 1.5" diameter port but could go up to 3" if I located in on the back. The box volume is a fraction under .4 cu. ft. If anyone can solve this problem and/or point me in the direction to find it myself I would really appreciate it.

[killerkowalczyk]

With a 1.5" port at 9" long its a tuning of 34hz. Dont even think of fitting a 3" port, its simply impossible. Remember that a port takes away volume from the cabinet aswell.

[kevinp]

Cut your 1.5"er to 6.3"

Will give you a tune of 40hz. Fairly flat to 80hz -3db at 47hz -6 @ 40

Not bad for $13

[turn2]

Hmmm. Since the box is only 8.5" deep this could be a problem. Maybe I need to stay sealed.

What resource do you use for your calcs? Thanks for the help!

> With a 1.5" port at 9" long its a
> tuning of 34hz. Dont even think of fitting a
> 3" port, its simply impossible.
> Remember that a port takes away volume from
> the cabinet aswell.

[killerkowalczyk]

<A HREF="http://home.new.rr.com/trumpetb/audio/fboxjs.html">http://home.new.rr.com/trumpetb/audio/fboxjs.html</A>

Great website, pretty accrurate calcs, super fast. Remember that 34hz is pretty low too, you might want to tune it a bit higher, i think the guy below suggested something like 40hz, id probably go with that. Especially because its such a small cab.

> Hmmm. Since the box is only 8.5" deep
> this could be a problem. Maybe I need to
> stay sealed.

> What resource do you use for your calcs?
> Thanks for the help!

[turn2]

Thanks KevinP as well.

>
> <A HREF="http://home.new.rr.com/trumpetb/audio/fboxjs.html">http://home.new.rr.com/trumpetb/audio/fboxjs.html</A>
> Great website, pretty accrurate calcs,
> super fast. Remember that 34hz is pretty low
> too, you might want to tune it a bit higher,
> i think the guy below suggested something
> like 40hz, id probably go with that.
> Especially because its such a small cab.

[Chris Roemer]

> For an initiation project I have acquired a
> pair of junked speakers, ditched the drivers
> but kept the nice MDF enclosures. I have
> chosen the Dayton 6.5" woofer (Part
> Number 295-305) for this 2-way bookshelf
> box.

> The enclosures I have are sealed but I am
> interested in porting them. I do not believe
> I am restricted either way by my choice of
> woofer. However, I am pretty much at a loss
> at where to go with that wish.

> I would like to use a 1.5" diameter
> port but could go up to 3" if I located
> in on the back. The box volume is a fraction
> under .4 cu. ft. If anyone can solve this
> problem and/or point me in the direction to
> find it myself I would really appreciate it.

I'm sorry they're not on sale also, but the shielded 6.5"ers (-306) like smaller boxes and are a lot better fit in yours. You're still saving $7-8 on a pair of -070 tweeters, so that ain't bad!

WinISD (beta - from <A HREF="http://www.linearteam.org">www.linearteam.org</A> ) says that a 1.5" port will "chuff" when tuned to 40 Hz with the -305 woofer. If you choose to go that route, you should put the port out the back behind the tweeter. Bass to 49 Hz.

With the -306, you'll be tuning to 42 Hz with a 1.5"d by 5.7" port. If you can fit it in there, I'd go with a 2"d by 10.6" port and run it out the top. I use the -306 in .5 cf with a 2.5"d by 14" long top port. Also, if you know anyone with a router, they can make a 1/4" "roundover" inside each end of the (PVC pipe) port to help suppress the port noise. The -306 tuned to 42 Hz will reach down to 44 Hz.

You can copy the xo from one of the BR-1 kits. PE has PDF files that go over all this in detail.

[kevinp]

With 3.5mm xmax and a 50 watt published power handling I doubt that port would be flowing enough air to chuff. Port air speed is not a fixed thing like Winisd plots, it varies with a drivers sd and power input level. I don't see sd posted in the PE info for this driver so I didn't model for port speed. Unibox is a much better tool for modeling as it gives accurate port speed and other info. I love Winisd for its grab and tune box feature. Once I get something that looks good there I dump the design into Unibox for everything else.

[turn2]

Great food for thought guys. I think I may take my chances and rear port for 40Hz. I don't anticipate working these real hard and hey, it's a learning project anyway. I have other details and a crossover to build before I need to decide on the porting.

I love how this hobby puts the ol' gray matter to work.

> With 3.5mm xmax and a 50 watt published
> power handling I doubt that port would be
> flowing enough air to chuff. Port air speed
> is not a fixed thing like Winisd plots, it
> varies with a drivers sd and power input
> level. I don't see sd posted in the PE info
> for this driver so I didn't model for port
> speed. Unibox is a much better tool for
> modeling as it gives accurate port speed and
> other info. I love Winisd for its grab and
> tune box feature. Once I get something that
> looks good there I dump the design into
> Unibox for everything else.

[norman]

> Great food for thought guys. I think I may
> take my chances and rear port for 40Hz. I
> don't anticipate working these real hard and
> hey, it's a learning project anyway. I have
> other details and a crossover to build
> before I need to decide on the porting.

> I love how this hobby puts the ol' gra
> matter to work.

you could put 90 deg. elbow in the port
and if you tune alittle higher you will
get more bass out put and a little higher
power handling.

[Chris Roemer]

> With 3.5mm xmax and a 50 watt published
> power handling I doubt that port would be
> flowing enough air to chuff. Port air speed
> is not a fixed thing like Winisd plots, it
> varies with a drivers sd and power input
> level. I don't see sd posted in the PE info
> for this driver so I didn't model for port
> speed. Unibox is a much better tool for
> modeling as it gives accurate port speed and
> other info. I love Winisd for its grab and
> tune box feature. Once I get something that
> looks good there I dump the design into
> Unibox for everything else.

The -305's definately DO chuff, severely, with a 2" port in a 3/4 cf box. I've heard them.

So I'd either rear port a 2", roundover the inside of both ends, or move up to a 2.5" port (which does get fairly long). I've successfully used option 3 and like it.

[kevinp]

Seems you are correct.

I took the sd of another 6 inch speaker, 130sqcm, and ran this design through Unibox. .4cuft, 40hz tune, takes a 2 inch port 11.2 inches long to not be noisy. This is all based on not exceeding the woofers excursion which happens at 20watts in this design. About 98db output from one $13 speaker flat down to 50hz. Again I say, not bad.

[kevinp]

Could be an answer to this thread.

<A HREF="http://www.pesupport.com/cgi-bin/config.pl?read=317327">http://www.pesupport.com/cgi-bin/config.pl?read=317327</A>