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
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
pinkmouse said:
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.
PeteMcK said:"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.
pinkmouse said:
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.
v-bro said:
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
"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
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
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...
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...
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
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
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.
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.
i dont think i will be putting in the 8 inchers for now.
my main priority is to get a couple of speakers up and running, with decent sound. i think i'v pretty much given up on teh 8 inchers, as i'd have to make the cabinets a bit to wide for my liking. as i understand it a wider bafel would lead to bafflestep to kick in earlier, and by keeping the front 8ish inches wide i'd avoid a roll off too soon. just when bafflestep will kick in with a 8' wide front i dont know, is that relative to the size of the driver?
-marius
my main priority is to get a couple of speakers up and running, with decent sound. i think i'v pretty much given up on teh 8 inchers, as i'd have to make the cabinets a bit to wide for my liking. as i understand it a wider bafel would lead to bafflestep to kick in earlier, and by keeping the front 8ish inches wide i'd avoid a roll off too soon. just when bafflestep will kick in with a 8' wide front i dont know, is that relative to the size of the driver?
-marius
Read this tread and reflected over the lack of interest other members seem to have by not continuing to post answers.
I think when nobody wants to contribute or discuss further suggestions, is for this case because of the lack of noob self-criticism, turning away the good evident advises given from other DIY members here above and the constantly insinuations of having good knowledge bases when making decisions for the suggested speaker design except of course from the reality that the questions reveals.
But can you change your mind?
Why is the baffle step a problem at all and where do you get an 8 feet baffle?
Take a look at a simulation of the proposed peaking 8L reflex box 11.5x8.5x9 in^3 with the necessary about 7 in long port, with inner diameter 50 mm and the consequences from 7.65 dB baffle step compensation loss at 640 Hz and up (R=6.5 Ohm and 2mH in parallel and series with the driver) that cures the problem but at a loss of sensitivity any beginner knows from reading other postings here at the forum.
From the very beginning, this is far from a decent design.
With your question here above, you are jumping back to an earlier design stage that’s not matched with your later assertions about expected speaker qualities. I think also nobody will ever agree if you still are making assertions and at the following instant of moment, return with a noob question on your conclusions.
pinkmouse:
Yes, very good advises to follow if you want quality integration as suggested.
demogorgon:
If you cannot tell what acoustical integrated target you are aiming at and what filter order and type you are thinking about; this statement above is almost worthless.
There are no indications that these statements are supported by good practice, but from wishful thinking.
You are polluting the whole mid-band with ripple by designing a speaker with a driver sensing a Qt value >0.5 in a box too small for a good reflex design with the proposed driver.
The transfer function for this 8 L reflex box is of peaking forth order and don’t easily integrate with a sub tuned close at 35 Hz, equipped with a LP filter normally suggested for sub use. Look forward to meet a mishmash regarding acoustic transient response, amplitude and phase.
Its your design, your believes …
Sorry, Your arguments are worth nothing for experienced people here at this forum.
Why put a question at this point when you already seem to be convinced over your 8 L reflex box qualities, it must already rely on dimensioning, ports dampening material and so on, why asking?
If you still are waiting for answers, be more specific and please pay more respect to those who are trying to help you and this tread could be of help for others facing similar design questions that you obviously have too.
Most members take DIY-speaker design more seriously, like the very good answer from Tuuka. If you aren’t convinced by now I suggest search this forum for threads containing noob questions.
b
Attachments
i got that all wrong, thanks for the info! i hadn't known of diffraction issues before, but i found http://en.wikipedia.org/wiki/Diffraction easily enough.
would you say theres a optimum compromise to be had?
i really do appreciate you taking the time to reply, thank you.
Bjorno:
that was quite a spanking!
I really am sorry for my failing manners, as i really do deeply appreciate the help this forums members has offered me through the years.
if theres cause to.
your statements:
"From the very beginning, this is far from a decent design."
"You are polluting the whole mid-band with ripple by designing a speaker with a driver sensing a Qt value >0.5 in a box too small for a good reflex design with the proposed driver."
points in a radically unflattering direction. when someone tells me my "design" is rubbish, then yes, im fully prepeared to change my mind!
and thats why im here to begin with.
"Why put a question at this point when you already seem to be convinced over your 8 L reflex box qualities, it must already rely on dimensioning, ports dampening material and so on, why asking?"
airing my thoughts, getting feedback, a poke in the side when im just plain out wrong..
So im off to the think tank again.
this basic concept of design is obviously just plain wrong, so now i have to figure out where to go from here.
"Most members take DIY-speaker design more seriously"
here i do have to disagree with you, but since i dont have a engineering degree, or any base skills concerning speaker designs, that may not be very evident to those of you who do?
-Marius
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