So finally im building some decent speakers

[demogorgon]

Chopchop.

My last 2-3 projects have been plauged by lack of propper equipment and not-so-good worksmanship.
Iv altso been a bit on the sloppy side with paint and suffered MDF expansion because of it.

But things are taking a turn!

an old buddy of mine and me sat over some beers and discussed music and stereos and came to the exelent ideas of building some speakers, considering we both are using crap, and really love good music, he likes to call it that, Jazz, smooth Jazz, good music.. huhu

anyways, my bud is a carpenter, and he has a workshop. see where this is going?

I bought my Seas G17REXa year back and played with em a bit, then threw them in my parts bin, 60 pund a piece resing in my partbin (one of them, need a whole barn to fit all my crap actually ), complimented by my 27TDFC seas tweets id might actually have something here..

so the basic idea was a 2way crossed at 2k, 2nd order, but with the xovers out of the box to alow me to cross activly in the future, when i get my thumb out of my..err..you know.
Tuned at 55Hz gives me, according to WINISD, a -3db at 58Hz, with a volume of 8 liters.

now, iv had so called "bookshelf speakers" in the past, tho they never actually fit in a bookshelf, and i wouldent put them there anyways, im all for going with floorstanders this time around. - at 8 liters?

nah

so i had an idea.
a while back apexJR had some nifty onkyo 8 inch'ers out of some padgrim sub, not half bad drivers, allthough no data was suplied i snagged a pair. never know when you might need some 8inch subs you know.

so i came up with a rough mental scetch, and that was a top chamber, tuned at 55Hz, 8 liters, square port, quite standard, what i could come up with.
and a bottom half containing the unknown sub, tuned at 35Hz, and a volume that would fill the speaker out.
with the ApexJR cervin wega fullrange amp used to power the sub.
the idea behind that was i saw the need to be able to have some some low end grunt when my 2x12' XLS subs werent available for use, i know me and i dont build stuff for keeps i build them for fun and future uppgrades, tweeks and trails.

theese speakers tho are going to be left alone and so have to serve more roles that your ordinary speaker.

So some preliminary plans have been made, and i do have a scetch on paper, but il be asking questions and try to get the most from this build that i can.


My first question, being a bit sctechy and out of DIY, iv had to many other things that took priority the last year,

is the tuning frequency of a ported encloasure with a given volume indipendent of driver specs?


-Marius

[PeteMcK]

"is the tuning frequency of a ported encloasure with a given volume indipendent of driver specs?"

-Yes,
but how the driver will respond to different tunings isn't....

Good luck, and ask heaps of questions....:-)
Cheers,
Pete McK

[pinkmouse]

If you're using a sub, either in the same box or separate, you don't want to port your midbass.

[v-bro]

Originally posted by pinkmouse
If you're using a sub, either in the same box or separate, you don't want to port your midbass.

Exactly, when I combine the two little BNS two ways (4"ported) I have with my 10"TL subs it allready sounds much better if I switch on my highpass filter (at aprox. 200 hz) on the little ones. The midrange becomes much clearer and if I close up the port it does about the same thing, with both there's not much difference....

The enclosure can probably even be a lot smaller than 8L.

[demogorgon]

Originally posted by PeteMcK
"is the tuning frequency of a ported encloasure with a given volume indipendent of driver specs?"

-Yes,
but how the driver will respond to different tunings isn't....

Good luck, and ask heaps of questions....:-)
Cheers,
Pete McK

hey Pete.

Your answer was the one i was hoping for.

Originally posted by pinkmouse
If you're using a sub, either in the same box or separate, you don't want to port your midbass.

Pinkmouse

could you elaborate a bit on that?
will the two ports mess with each other?
I agree theres "no need" in the general situation of a sattelite-sub situation.
but to get the G17rex to flat out i need to port, a closed box gives a flabby respons, i belive its starts to fall at about 100Hz, unacceptable.

so in this setup i need to port, or at least it seems the best solution.

Originally posted by v-bro



Exactly, when I combine the two little BNS two ways (4"ported) I have with my 10"TL subs it allready sounds much better if I switch on my highpass filter (at aprox. 200 hz) on the little ones. The midrange becomes much clearer and if I close up the port it does about the same thing, with both there's not much difference....

The enclosure can probably even be a lot smaller than 8L.

v-bro

could you give me some more to work on that "it sounds better"?

the sub is ment for situations where i for some reason dont have my 2x12's in action, and so wont se more than "crisis" usage. im kinda killing two birds with one stone here, i got space to use, and this seems the best way to use it.

-Marius

[PeteMcK]

"you don't want to port your midbass" -
well, generally you're probably right, & the result will be more predictable, but my current system has ported mid- bass plus ported EBS woofers below 120Hz & has great solid lows...you can always close the ports off later to see what difference it makes...
cheers,
Pete McK

[v-bro]

It seems to me like it won't be a very big problem in the low frequency range. The only thing that really suffers from the larger cone motion is the midrange area that is still produced by the midbass...

Maybe a filter (with on/off switch like the one I built recently) can help you smooth the midrange...and maybe even improve power handling...

[demogorgon]

Hello

I dont consider midrange to be a problem, since im crossing at 50-60 ish i wont have to worry about bottoming out the G17EX, and as such, distortion will be kept at a relativly low level in the midband.

Il try the ported design and block the port later as Pete suggests, and see if that helps.

v-bro, you say a filter for smoothing the midbass, well, thats what porting has helped me with, it is smooth, very much so. the G17REX is an exelent driver with a smooth freq. response. as you say filter, yes, the drivers will on a longer term be activly filtered.
so i dont see a need to go sealed

[demogorgon]

so when calculating the volume of a box, am i supposed to count the area inside the bassreflex conduit?

oh, and the speaker will take some space inside the box as well, il throw that volume into the equation as well right? ofcource i will..

[Tuukka]

Yep, the volume of the port is subtracted from the internal volume, as well as the speaker volume.

I would also suggest not porting the mid, that is if you are using the 8" subs in the same floorstander. A crossover at 50-60 won't leave the 8's much musical material to play. A crossover around 100hz would make those 8's much more useful as they could provide a nice presence to the bass. Having the seas mids in a sealed box would let you take advantage of the roll-off, making for an easier transition from sub to mid and maybe a simpler filter. Also, by having the mids sealed, there'd be no direct midrange from the backwave as you would have with a ported enclosure.