building bandpass for 15, need some advice.

[///M5 2,833]

I wasn't offended, just trying to explain the "seriousness". Anything I am interested in I want to find out more about. If it is easy I'd like to master it. It is 7th grade Algebra that you need, nothing more. That level of math is obviously rudimentary to me, but unfairly as I am a Physicist with an Acoustics degree as well.

[95Honda 486]

I think the problem is people come here looking for simple solutions to complex design/building/evaluation scenarios.

 

If you want it to be easy and not involve math pay someone to do it.

 

If you want the best possible outcome, as with anything in life, be prepared to do the work...

[heftybone 4]

like i said, I'm good at math, i just don't like it!

m5, what know nd of physicist are you? and then didn't realize that there where degrees for acoustics. huh, you really do learn something new everyday. well, every other day maybe. well maybe once a week or so, cuz when you know it all its hard to learn anything new!

and honda man, I'd never pay anyone to do anything for me! unless it's installin speakers in a dash or doors, man i hate that! or maybe my laundry too.

you guys do realize that i like to joke around alot, so you know that I'm not serious with alot of this stuff. i just can't bring myself to say lol, or somethin girly like that. I'm a MAN! YEAH!!

[cobra93 47]

Nm

Edited February 5, 2015 by cobra93

[///M5 2,833]

Not sure what you mean by nd, but I work in Acoustics & Vibration.

[jcarter1885 995]

So when will this useless thread come to an end, 5 pages deep with no means of coming to a conclusion. People trying to explain things to someone who doesnt care to get it or just cant get it. This is what happens when you feed the trolls, they keep coming back for more.

[heftybone 4]

So when will this useless thread come to an end, 5 pages deep with no means of coming to a conclusion. People trying to explain things to someone who doesnt care to get it or just cant get it. This is what happens when you feed the trolls, they keep coming back for more.

you really don't read much do you. and you have the audacity to call me a troll? you are truely an idiot.

and m5, that was supposed to be "what kind of". my phone was actin funny when i kept postponing my update. it's better now, and you answered my question anyway.

what kind of things do you apply the acoustical physics to? structures, automobiles, etc..?

[///M5 2,833]

You name a company and I've been in helping their Engineering teams. Pretty much anyone who makes: cars, planes, engines, bombs, computers, phones, hearing devices, and tons of other shit. I fly about 150,000mi/yr

[heftybone 4]

wow. that's very impressive. bombs huh? i hope you get those calculations accurate! man you wouldn't think acoustic and vibration physics would be exciting, but yeah. i bet you see some cool shit, man. thanks for sharin, and i am honored to have your help and advice. i feel secure knowin that the teachings came from such a knowledgeable source.

[heftybone 4]

well people, things have changed a bit. thanks to obamacare and me not reporting my $6/hr raise, i owed somebody some money. evidently healthcare.gov.

anyway, i had to 96 the fi, dammit!, in favor of a dayton audio um15-22. still a decent sub, doesn't take nearly as much power as the fi, but it's still 800watts rms, dual 2ohm vc and ¾" xmax. so it somewhat met my criteria, but not like the fi. also, it likes a 6cube box, which i don't have nor will i have because i have to keep some room in the van here! i have a 4.5cube box, so I'm a little short there. it does take a 3cube sealed though, so if it doesn't work right in the ported, I'll just close it up and viola, I'll be right on sealed specs.

I've built this box to be very versatile, i can easily close it off to make 3cubes.

i also had to change up my amp, which is where i chose to spend the majority of the money, so i can have good power next year.

so thanks again for all the help, and I'll let you guys know how it sounds.

Edited February 11, 2015 by heftybone

[heftybone 4]

okay people, it's all hooked up and sounding pretty good. the higher frequencies don't hit as hard as the lows, but i like it low anyway so that's not a big deal for me. i suppose if i did a 6 cubic foot box like the sub calls for, it might sound better, but i don't see how because there's no distortion or waning like alot of subs do in the wrong enclosure. I'm seeing 126db from a radio shack spl meter. i was wondering if that was good for 1 15" sub? i know it hits harder than any other single sub system that I've ever had, it even hits harder than the 3 jl audio w2's i had with 2000watts pushin em.

as far as electrical goes, i definitely need an upgrade, but it's not that bad. just some slight headlight dimming. plus I'm sure i can get more out of this amp if i upgraded.

I've got the sub wired at 4 ohms now, but i intend to wire down to 1ohm after she gets broke in, and perhaps I'll wait until i upgrade the electrical. what's your thoughts on that?

i have to say thanks again to everyone for the advice.

on a side note, i went to my local jl audio dealer, as i was considering one of the w3 15's and the owner and i where discussing my enclosure design with the lengthy port modification and according to jl audio, the port works if you calculate it correctly. what a surprise to me!

anyway, thanks again fellas and please someone tell me if 126db is good for 1 15.

[altoncustomtech 773]

A meter like that isn't really ideal for measuring that, but for a quick reference I did a 131.1dB at 49hz with my single XCON 10" in an enclosure designed for flat SQ reproduction.  It also did 129.9dB at 28hz and 129.5dB at 36hz all measured with a new TermLab meter which is built for the task.

 

 

Not knowing the frequencies at which your response pleases and disappoints you makes it very hard to fix what's wrong.  If the higher bass frequencies are lacking output then you might have to beef up your front stage to help with midbass response.

[heftybone 4]

oh no, the front stage is rather pleasing. very nice sound and loud with just the pioneer hu running the 2 bostons and 2 pioneers i got for cheap. those highs keep up rather well, i was talking about the high frequencies of the sub itself. they don't hit very hard but the lows are hitting hard. that's where i seen 126 at about 32-36hz, that's my guess anyway.

the meter is an spl meter, it has the little mic on top, but only goes to 130db. it has selection for a or c weighting, c being for music so i assumed that it was somewhat precise. at least more precise than the app on my phone!

I'm sure i have to do somethin with the enclosure though. the sub calls for 3cubes sealed (if you didn't read my previous, previous post), so i might just seal it up. but do you think it will produce more decibel in the right sized sealed box as apposed to the wrong size ported?

[altoncustomtech 773]

What is your LPF set to on your subwoofer's amp?  You may have it lower than the frequencies you're expecting to be hearing, though they probably shouldn't be in the realm of where the sub should be required to play.  Another question is what the HPF is set to (if using one) on your front stage.  They could not be playing low enough to cover the frequencies that are missing.  Otherwise, the sub may just not excel at frequencies that aren't considered "sub-bass"

 

A subwoofer, as indicated by it's namesake, is designed to play "sub" bass frequencies.  Generally speaking that's in the 40 to 50ish hz range and down, the exact numbers always seem to up for debate.  A woofer overlaps some of those frequencies and plays into the midbass/lower midrange frequencies, say 40 to 50ish up to around 500 to 600ish hz.  That's where mid range frequencies begin to pick up and somewhere in the 4kish neighborhood is where the tweeter would ideally be playing.  Again all those numbers are debatable but the point is that a subwoofer isn't supposed to play but a very small range of frequencies by comparison to the rest of the system.  I think I calculated the percentages at something like .2% of the general audio spectrum (20hz to 20,000hz) is considered sub bass and when most people set their LPF crossovers in the 60-80hz range that's only .3%.  Everything else can't really even be played by a subwoofer.

 

That's why I said the front stage needs to be looked at.  If the sub is lacking the output you expect in the "high" bass frequencies then a smaller, preferrably more front located driver should be picking those frequencies up.  Proper installation including a solid mounting baffle and sound deadening at a MINIMUM is how the most possible performance is used from the speakers in the front stage.

 

Now, if the lackluster upper bass frequencies aren't bothering you bad enough to do the work and spend the money required to maximize what you have then that's okay.  Everyone has their own listening tastes and goals, I'm just trying to provide you with good information on the possibilities and reasons why the response is the way it is and give you some food for thought on the what and why of how to go about making it better.

 

Your enclosure may be the issue.  Knowing exactly what it's tuned to would be the best place to start.  Sure, you may have an idea but the only way to know for sure is to play tones and watch the excursion of the sub.  The sub will move the absolute least amount at the tuning frequency.  Start at something like 45hz and turn the volume up enough to get it moving good then go down in single increments of frequency until you see the sub move the least amount.  You may have to go up and down a few hertz around the tuning frequency to best determine movement but you'll have your answer.  Really low tuning generally results in reduced upper bass response, its just an avoidable tradeoff.  You can raise the current tuning frequency a few hertz to experiment and see if a slight trade in a few hertz of low frequency response nets you the upper frequency response you desire.  You could also try sealing the enclosure, though I don't think that just covering the ports will NET you 3cuft from 4.5, you're gonna have to fill the box with blocks of wood, bricks, or some kind of ballast.

 

There's plenty of things to do and see what helps.

[heftybone 4]

yeah, i got higher frequencies out of the sub, it just doesn't hit that hard at those notes as it does on the lows. i have the front stage crossed-over at 80hz along with the sub at 80hz, so I'm thinkin I'm gettin all of the range of the music, but i don't know if I'm missing anything because they're both set to stop at that single point instead of overlapping.

i kind of expected to have more spl than 126, but like you said perhaps the meter isn't quite the best or what have you. maybe I'll take it to my local shop, although i may get some reluctance because i didn't buy from them, I'll still ask if they can meter it for me so i can find out from a more reliable source.

[///M5 2,833]

Crappy box will kill a subs sound big time.

[altoncustomtech 773]

They still overlap, the crossover setting isn't a brick wall.  The frequencies roll off, like rolling down a hill, above/below the frequency it's set to.  How steep that hill is depends on the slope of the crossover and that determines how many dB's the response is down each octave (doubling/halving of the frequency it's set to).  Take your sub for instance, at 80hz with say a -12dB slope the frequencies would be down -12dB @ 160hz.  Which means the sub is playing 100hz quite audibly as it would only be down -3dB.  The higher the frequencies the higher the overlap because an octave covers many more frequencies.

 

It may not be that far off, I've never had an opportunity to put a handheld Decibel meter next to a TL or similar SPL meter and compare them.  Too bad you didn't live close I'd have you come over and we'd meter it and go over everything.  

[///M5 2,833]

The ratshack meter is a type II meter, not a type one. At 8kHz the specification is something like +/-10dB or something absolutely ridiculous. Has a roll off down low, but I don't remember it nor have a chart in front of me atm. Using it for anything not just relative is really somewhat pointless.

[heftybone 4]

well thank you alton, i think I'm gonna move now! seriously though, that's good to information. I've always had crossovers and eq's but I've always just tuned by ear until it sounded good to me, (which we all know is all that matters). anyway, now I'm matchin the gain voltage to the hu volts and settin crossovers matching and all that jazz and it sounds good too, so to me what I'm doing now is giving me the same results as I've always got.

and m5, i wouldn't say my enclosure is crappy, it's just not right for this sub unless i seal it. which then I'm afraid it's going to diminish my spl severely. so here's a new question; how many decibels would i lose by sealing it? if it's like 1 or 2 then I'm gonna go for it, but if it's more like 10-20, I'll stay with what i have.

because again, it doesn't sound bad at all and I'm still in the breaking in stage so I'm only putting around 400watts to it. when i feel it's broke in then I'm gonna run it at 1ohm and see what happens. and yes that will be before i make any changes elsewhere.

[95Honda 486]

I guess if it is loud enough is relative.  

 

I was doing 142db, at the headrest, on the Term Lab, with 180 watts total and 8s in a Full Size Bronco...  

 

I would want to get an honest reading, but that is extremely low for any single sub in a bandpass with cabin gain.  But, like M5 said, SPL meter is extremely suspect...  I have had a few of those Rat Shack meters, but the last time I used one was maybe 1993...

[heftybone 4]

reading more on the meter from ratshack? it's hard to call it they because they do sell quality products. well as far as their speaker wire goes anyway, but damn it's pricy. and the only reason i was going there is because they're closing and everything's like 80% off.

oh anyway, the meter says its got +/-2db accuracy at 94db spl, but it also says for home/hobbyist use, so yeah, it's probably not accurate.

i know this sub hits harder than any other system I've ever had, even the 3 jl audio 12's @ 2000 watts. and that system could flip half-dollars on a snug-top.

I'm sure the box needs to be bigger though, but i couldn't imagine it actually gettin harder. but I've still got to wire it at 1ohm so it sees it's full potential. but I've read that a 500watt increase only gives 3db, so i guess it's not gonna get that much harder if that's the case.

i don't know, I've never had a system of this magnitude. the highest quality has been jl audio because that's what the local shop deals in. the shit i got now is much better quality then jl. by a large margin.

[Frostedflakejake 148]

500watt increase only gives 3db, so i guess it's not gonna get that much harder if that's the case. 

 

By definition, a 3db increase would be a double of power, and vice versa. Assuming the speaker has uniform efficiency across the power band, doubling the power to the speaker should yield a 3db increase in output. 

 

So I didn't read all the pages here, but if you're running currently running 500 watts then yes, a 500 watt increase of power will yield a maximum of a 3db increase. 

[heftybone 4]

thanks jake. so i guess 3db isn't going to yield a significant seat-of-the-pants difference then? i wouldn't think it would anyway.

also on a side note, would me changing my 10awg copper+ and aluminum- speaker wire to 12awg both copper and actual 12awg make any difference?

[SpeakerBoy 64]

You got it backwards

Smaller number = bigger wire

Probably not an audible difference

Edited February 21, 2015 by SpeakerBoy

[Frostedflakejake 148]

thanks jake. so i guess 3db isn't going to yield a significant seat-of-the-pants difference then

 

That's kinda relative. The issue is that the human ear is pretty complicated and everyone has one that's a little bit different. It also depends what the 3db increase is from. At higher volumes the increase in DB will be less distinguishable. Meaning that going from 120 to 123 will be more noticeable than going from 160 to 163.

 

From what I hear most people notice a difference but that it's not too significant. But I dunno whether or not that's placebo effect...