http://i40.photobucket.com/albums/e216/saxwonder05/audio/kel.jpg
one is 1cuft tuned to 50hz
the other
3cuft tuned to 20hz
i need input on whether i could commit to this
it shows on winISD a big boost in 20-50 with a steep roll off on either side.
would the design yeild the curve im looking for?
-Drew
Replies (37)
swez on 08/1/2007 08:52:19
That is typical of most bandpass designs. We get a narrow peak and steep angle slopes above and below the BP region. Depending on the application, this could be good, not so hot or not very usable.
If this were a HT box and designed for deep lows, it would be great as long as the front mains could make up the upperbass region and above.
If for mobile audio, you may wish to adjust the tuning parameters. 20 Hz. is inaudible, but we can feel it. However, there is little music content in this range. DVD movies with lots of high impact subsonic energy would be a likely source for below 35 Hz. (But not most music)
Here, consider shifting the low pass tuning side (F3L) upward so that it's more like 30-40 Hz. The upper region, (F3H) might be a lot better in the 75-80 Hz. range
On the high pass side of the box, 50 Hz is not bad, but closer to 75 - 80 Hz would be better for mobile sound. It also depends on the Mid/high speakers used to fill in the rest of the musical content range. A 6.5" round or 6x9 ovals can do a fair job at ~60 Hz. Smaller speaker formats will struggle below 80 Hz.
Can you fill in the SPL vs Frequency plot numbers in the following ranges? Where is F3L & F3H on your plots now?
20 Hz = xx dB SPL
25 Hz = xx dB SPL
30 Hz = xx dB SPL
35 Hz = xx dB SPL
40 Hz = xx dB SPL
45 Hz = xx dB SPL
50 Hz = xx dB SPL
55 Hz = xx dB SPL
60 Hz = xx dB SPL
65 Hz = xx dB SPL
70 Hz = xx dB SPL
75 Hz = xx dB SPL
80 Hz = xx dB SPL
Swez
MrBrownstone on 08/1/2007 18:30:48
Second guess the Bandpass altogether?
Why are you wanting a bandpass enclosure? basically, it's a one-note wonder...or as close to it as possible.
Almost ALL standard vented enclosures will give you all that you need from this design. I guess my questions is why are we needing a bandpass setup?
swez on 08/1/2007 19:02:58
Not so Grand Pooba... (Mr. B)
A very well designed BP system can be just what the doctor ordered if we define the operating parameters well. NewB is on to something and just needs to shift his tuning parameters to nail it down good.
To the contrary, when a guys knows his stuff and uses a good computer modeling program to design a high impact BP enclosure, it can rock well and stay pretty flat in the BP range used.
Yes, it takes some time to plug in all the T/S parameters and then plot the best curve for the application, but if one can get a solid 30-80 Hz plot that is 4-6dB above using a simple ported/vented system, he's done something note worthy.
NewB.... proof this one out as best you can. If it works, something can be learned by the process. If it does not work out, at least a good effort was made.
Swez
SQLThump on 08/2/2007 02:36:40
NewB, what subs are you planning use do with this box? I have always liked bandpass, and that design look sick.
Victor on 08/2/2007 02:41:15
ooopsss...!!!!
Just a suggestion here newB.... that design is a 6th order BP... it is known to rarely exhibit a perfect bandpass response, there is going to be some sort of out of the band response in its output...you may need a notch filter to avoid this out of band noise.....6th order BP are also know for the most poor transients when compared to all other types of enclosure designs...
like in a ported design its likely to unload a sub below tunig freq here the chances to unload increases as both the Vf and Vr are ported and tuned differently.....
i would suggest going with a 4th order BP if space permits...
Victor....
6th order BP are rarely used for high end audio systems they are only used for low freq reinforcement in HT and multimedia applications...
http://www.diysubwoofers.org/bnd/bandpass.zip try using this calculator.....
newB on 08/2/2007 04:30:14
ok so here are the updates- first off- THE PIX OF COURSE!
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00957.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00963.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00960.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00977.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00978.jpg
ok here are the acoustic notes.
the high tune sounds good- i like it. it has good output and i dont think i'll mess with it as of now. the lower tune is definatly to low. i didnt get any output from that port unless the freq dropped to the 20s. so i ended up with a crappy sounding box-
to compinsate- i'll be cutting down the lower port and raising the lower tuning frequency to the Fb and possibly packing some fiberfill in the smaller chamber (depending on how testing goes)
jury is out- build result pending.
-Drew
newB on 08/2/2007 04:46:58
correction.
the voice coils are wired wrong. will be changed and i'll give another update
-Drew
Victor on 08/2/2007 06:21:36
good going.. if you have the equiplements i would like to see a freq vs db plot in an anechoic room... this will give u the actual performance stats...
if it is flat enough in the frequency band desired then youre definitely successfull in building a 6th order BP.. is there any audible out of band noise???
Victor...
newB on 08/2/2007 06:26:43
yes. but i still have extensive tuning to do for this setup.
so i'll see what i can do-
-Drew
MrBrownstone on 08/2/2007 12:15:50
Swez
The question was why bandpass? There are some great reasons for BP and you didn't see me ****ting on his post like you did mine? This design was popular in the early 90s when everyone was trying to get more out of a speaker...before power went from $700 100Wx2 to 1000Wx1 with 40% less current draw.
I'm not saying the application will or won't be successful, but we need to know why we're doing it. i.e. are you using a sniper rifle or a cannon? Both have different applications, but why build a cannon when you need to crawl through the forest and sneak up on someone?
What i'm trying to say here is that the physics haven't changed. We still can't eliminate gravity on earth without dispersing it's mass, and with these enclosures, we still can't make them with better transient response than standard vented or sealed enclosures.
Also, we CAN'T make them handle the power any better than other enclosures. So, just exactly what CAN we do?
1. Lower power handling
2. Decrease Frequency response to a more limited range (1 octave)
3. Decrease the accuracy of the bass response
4. Decrease the input power required for Xmax
What's the matter with you, man? Walgreens run out of Correctol & Depends :-)
It's not a matter of 'booking up'. Bandpass has been around and so has the software necessary to fine tune the design. What we need to know is the application. Why do we need this design?
Few things we know:
-Volume: BP takes the total amount of both a sealed AND vented enclosure
-Advantages of this design are a high efficiency over a small range of frequencies and some filtering characteristics.
-Disadvantages are decreased frequency response, less accurate reproduction, extreme complexity in design and assembly, larger enclosure size, greater woofer unloading and decreased power handling.
You can TUNA melt, but these boxes have a maximum benefit. This is why most folks don't bother anymore. The design was purposed to get more efficiency, but at the cost of accuracy, power handling & frequency response.
I guess the real question is, do we want a box that produces 30 to 50Hz? if so, Frickin brilliant!! If we don't want a whole lot of quality sound, Fricking brilliant!!
Other than that, they've made a 'New & Improved' typewriter. If you want one, I know where you can get one.
See my point? if not, please don't go off 1/2-cocked with a vendetta until you know what you are shooting at.
I'll bet you $1000 bux we can design a vented enclosure and use the existing crossovers & eq options in most quality amplifiers to accomplish the same things you're trying to do here.
Please don't take the bet. You'll be out $1000 and 40 hrs trying to tune a donkey's hee haw into a swan song. Not to mention the $1000 extra in boxes, audio equipment and lost time invested.
newB on 08/2/2007 14:32:35
whoa whoa....
the reason I built this box was because
1) i wanted to continue my experiece building boxes and liked the challenge the BP box offered
2) best use the 150watts available to push good output from 20-50
his old box is 1.8cuft per chamber tuned to 32hz and was plenty loud, SO, if i cant tune this BP quite right he can always drop that one back in GRIN
i'll keep a post up later this afternoon when i flip the wiring, and double the power (hopefully)
-Drew
swez on 08/2/2007 15:52:54
As Vic stated, this is a difficult box to get a wider range of usable frequency range you may desire. A 4th order BP is a bit more predicatable, but dual tuning a 6th order BP will be challenging for sure.
It seems to me, the ideal option here is to get the F3L up to about 30-35 Hz. The F3H side of the slope would be great if that could be moved upwards of 70 Hz or a tad higher. If that can be done by changing port lengths and still offer a reasonably flat response curve between say 35 - 70 Hz, this might be a neat project. To obtain this performance, we often need extensive notch filters to smooth out peaks and dips.(Ripple affects) Only the designer, builder and user can determine if all that is worth the bother.
As Mr. B points out, used a few BP designs for Pro Audio installs and find them lacking in clarity and overall fidelity/punch too. However, to give some decent low bass in larger rooms, they do work well if we are able to bring the Mids in at the crossover point to fill in the gaps. That often takes an RTA and lots of PEQ power, (Notch filtering) to fill the room with a well balanced audio content. (It's not easy as each room/space has its own quirks to work with)
Swez
PS B, we both have thick hides and I did not intend to crap on your head sir. (Yes, I was direct, but not vindictive... it's not my style) However, if you feel like I did crap on your head, I appologize and do respect you as a man and a talented one at that! (We have known each other a LONG time and it's OK to agree that we sometimes disagree) Yeah, been having some rough days of late, but that's life. If I was too brash, accept my humble appology and let's move froward.
What I am asking here, is that we post information that leads the reader to usable and workable solutions. If there are none, then state the case and why. If that is possible, great! I hold no malace toward anyone here. We do not need a pissing contest on the site and if you wish, we can discuss it privately. (E-mail or phone) In fact, I will call you in hopes of clearing any misunderstanding up. Good frienships are hard to find and that is more important to me than being wrong, right or otherwise. We are probably saying the same things, but in different ways is all.
Victor on 08/2/2007 16:58:46
dont take this to heart .... its a mere dis agreement over a subtle issue.. wether BP are effective or not it ultimately depends on the end user..
if he wants it .. as techies its our duty to show them the pro's and con's of it... and if he yet wants to do it.. i guess we shud stand by him and try to provide him with as much help as possible..
if it works out its something new we learn and if it doesnt he learns it the hard way..... CHILL guys..
Victor...
newB on 08/2/2007 17:52:26
so here is my pan of attack for when he gets off work.
1) fix wiring and bring power to all four voice coils [haha]
2) then do an amp swap and double the power to the pair.
then sample.
if its still not performing to my liking i will increase the bottom port to ~32hz and increase the top port to ~80
and test again!
plenty of ABS/PVC lay'n around so im not to worried
-Drew
swez on 08/3/2007 00:01:19
Worth a try. In this case, you'll be cutting pipes shorter in both chambers. (Change tuning parameters this way)
One thing I am not certain about, is the "phasing results" you'll get between the front and rear chambers. That's a study in physics I cannot comment on. However, adding some polyfill to the rear chamber is often used to dampen rear wave reflections inside the box and smooth out the ripples of a given frequency curve in that segment of the output plot. That might help along with your other mentioned plans as well.
Keep us posted OK?
Swez
cplkittle on 08/3/2007 01:24:01
My friend and I had alot of fun with an adjustable 4th order bandpass box. I can't find a picture of it online, but the sub was mounted in a box without a back on it, and placed in a ported box where the position of the sub could be moved anywhere along the length of the box and screwed in place when fine tuned. It was pretty interesting. The inside box had to fit pretty tight against the outside box to prevent the air from flowing around the edges, and even though it wasn't airtight, it gave a really noticeable difference in sound when moved just a little. We played a 33Hz test tone and slid the speaker until we got a +5dB gain from the port. This is also a good way to find the cabin gain peak frequency.
Victor on 08/3/2007 03:05:04
That is a very good concept there kittle. have seen a few DIY projects documented on the internet of a similar sort. and i am sure they must be fun building and experimenting with....
one surely gets a lot to learn from it even if the box doesnt work well in ur car audio system... i am sure newB is going to have a similar learning experience ... many of us like to actually do it , not fearing failure and learn in the process...
though.. the deeper u will get into BP enclosures all its Con's will poke u like a thousand thorns .... specially if u are a SQ guy.... one certainly wudnt want to trade off a lot of other things just for a few extra db's over a limited bandwidth...
handling detailed issues like tuning, phase difference , time lag, cancellation, reinforcing of sound waves, unwanted bumps in freq graphs, designing notch filters or BP filters to smoothen out the curve and eliminate out of band noise...
it wud not be an easy task to go through all this pain , to learn a lot of electronics and physics and work out a lot of math... but if you are bent on doing it then it definitely is a challenging task capable of giving a lot of self satisfaction at the end of the project..
nothing that is impossible..
personally i have gone thru all this and at the end of it,, just like MR.B, realised its not worth going thru all that pain just for a few extra db's over a limited bandwidth...
instead would prefer going with heavier amplifier and a better sub in a sealed or ported design for a wider range of freq performance...
.......................................................................................
BP is a very old concept.. basically developed to get higher outputs when not many high power amps and subs were easily available for affordable prices... a very efficient way to get a low power system sounding loud.....
using a BP back then made more sense then using it in these developed product markets... yet when u want more SPL with lesserpower BP is definitely a way to go, but with a lot of trade off... ofcourse beggars are not choosers, cant have it all at the same time...
Victor...
There is one design that has really impressed me in terms of SQ and SPL , very difficult to design tho... those are Quater wavelength Transmission Line enclosures.... i have personally auditioned a few designed by experts and found them amazingly sweet . SQ of a sealed and SPL of a ported enclosure.. a very balanced mixed...
dont seem to find the time with money matters being more important as of now, but some day i wanna start experimenting with those....
newB on 08/3/2007 03:19:41
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00983.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00985.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00986.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00987.jpg
-Drew
newB on 08/3/2007 03:21:40
as you can tell after Serious Frustration and plenty of pent up anger we decided (we being the owner of the car) to trash the idea take the 45$ hit and start again. (yay)
no regrets
ive learned a lot during this build- as far as pure construction goes this has been my most solid enclosure yet. down to the 32nd of an inch of any given corner or any given length was exactly as it was drawn up on Sketchup (which is an amazing program)
-Drew
Victor on 08/3/2007 04:04:01
are u trying to pee into the box here... THINK
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00987.jpg
GRIN
newB on 08/3/2007 04:07:32
thats not me- but the owner of the box.
imaginary poo with imaginary stench.
it was horrible
-Drew
Victor on 08/3/2007 04:09:34
if u are really wanting to build a BP... try a 4th order alignment...
the wicked one is a difficult construction but very very efficient and better of than many other BP designs..
its a horn loaded BP....
http://www.decware.com/whorn.htm
http://www.decware.com/whornok.htm
though it wud be a huge box if u want to use 2 x 12"ers....
the wicked one has a dedicated forum too, lots and lots of info there on it as well as other designs.... worth being there...
Victor....
Victor on 08/3/2007 04:12:24
what exactly went wrong with this.... ???
where did u face a problem???
newB on 08/3/2007 04:17:06
we just couldnt get it to sound as good as it looked on WinISD. it was horrible sounding. im sure there are 1,000 possibilities why (as previously stated) but i just couldnt seem to eliminate the variable that was restricting the output. so we opted to take the 45$ hit and try again something more simple.
maybe a spin off his other vented box with better ports and a higher tuning.
-Drew
Victor on 08/3/2007 04:26:21
what is the freq range u are aiming to boost..??
Victor on 08/3/2007 04:26:59
do u ahve yahoo or msn or skype messenger.. its better to chat real time...
newB on 08/3/2007 04:40:51
AIM/msn me at
Saxwonder05
-Drew
Victor on 08/3/2007 05:30:48
seems cant add u to my msn....my msn id is ...
victorexports@hotmail.com
swez on 08/3/2007 09:45:54
Hum, the pics say it all...
BTW, did you ever test the box w/o installing it into his trunk? Sad to see all that effort turn out so unsatifactory. Back to the old drawing board.
I've heard of "burying the hatchet" on a matter, but this one has a twist... "bury the claw hammer"? (Deep into the top of the box's top) That's a fresh concept. lol
Swez
Victor on 08/3/2007 10:29:52
can u give us the specs of the subs u are using.. and lets see if we can come up with somethign interesting and performing at the same time...
Victor...
Victor on 08/4/2007 04:09:54
let me just give u some info on how to select an enclosure system... one cant just throw in any subs in any kinda enclosure.. there are specific parameters that guide the selection of an enclosure for a particular sub....
T/s parameters as you are aware of.....
Qts = total Q of a driver at Fs (resonant frequency).
Q = relative damping of a driver.
horn loaded Bp, 6th order Bp, quasi 8th order Bp and ( other higher order alignments ) best works with drivers which have Qts < 0.3
Ported or vented systems perform best when used with drivers having Qts between 0.3 and 0.4
drivers with a Qts around 0.4 work well in sealed as well as ported/vented systems.
drivers with higher Qts above 0.4 are usually best suited for sealed systems.
4th order bandpass systems can work well with drivers with any Qts between 0.3 to 0.6.
drivers with Qts above 0.7 are usually best suited for free air or infinite baffle use.
hope next time you and your friend decide onto building any enclosure look into this and then relate it to the specs of the subs u are using before starting to build....
if certain technicalities are ignored then its always a shot in the dark...
Victor...
hope u dont learn it the hard way anymore and are open to first learning on paper sheets before u start cutting MDF sheets...
newB on 08/5/2007 01:23:55
i'll have to save this topic. a lot of very useful information on that last post victor.
the subs i was using are TOXIK STREETs.
(( toxikaudio.com ))
the specs are online
-Drew
Victor on 08/5/2007 07:25:22
true... but which ones?? the model number?? please give complete info...
swez on 08/5/2007 08:21:17
STR1242 Street series, 12's. They do list some T/S specs on the web site as well. (2+2 DVC's, 300 RMS)
http://toxikaudio.com/
Swez
Victor on 08/5/2007 16:10:46
Those subs are per my calculations....
if you want to make a 6th order bandpass for one of those..for car audio use.... it would need...
Vr = 1.75 cuft (Net rear Volume)
Fr = 35Hz ( Desired rear tuning freq )
Np = 1 ( Number of ports )
Dp = 4" ( Diameter of ports )
Lrp = 12.5" ( Length of ports )
Vf = 1.25 cuft (Net front Volume)
Ff = 70Hz ( Desired front tuning freq )
Np = 1 ( Number of ports )
Dp = 4" ( Diameter of ports )
Lfp = 2.5" ( Length of ports )
This enclosure will give you an average 6db rise in freq between 35 to 70Hz in an anechoic room...and a 18db per octave roll off...
considering cabin gain and resonant freq of the car you could get around a 9db total acoustical gain in that freq range.....
means each of these subs will occupy a 3 cu.ft internal space if you want to build an optimum 6th order BP for it....
2 subs and 2 encl means twice of everything.....THINK
---------------------------------------------------------------------------------
Anyways, if you want to chuck the idea of a 6th order BP... I would suggest you go with a well tuned slot ported box for these subs.... COFFEE
Victor...
swez on 08/5/2007 22:27:42
I think you meant to say cabin gain of additional 9dB + 6dB gain from the BP enclosure = about +15dB, 35-80 Hz. (depending on cabin resonance)
That is a substantial gain in efficiency. Is this not a small format SUV as well? If yes and the rear seats are lowered, cabin gain would be closer to +15dB.
Swez
Victor on 08/6/2007 02:43:12
thats a huge bump and can sound very booooooomy....
also its a huge enclosure for this sub.... this sub can perform decently well in a 1.5 cuft ported enclosure..that means we shall be occupying twice the volume a total of 6 cu.ft for 2 subs.. thats a lot of space to give up in a small car....
why would we compromise on quality, shall be giving up a lot on transients... you wont be getting very clean and crisp punch from this encl...it will just be heavy heavy bass reinforcement... something you can throw in the car to feel test tones..... not something one can use for regular day to day quality music listening..
one is 1cuft tuned to 50hz
the other
3cuft tuned to 20hz
i need input on whether i could commit to this
it shows on winISD a big boost in 20-50 with a steep roll off on either side.
would the design yeild the curve im looking for?
-Drew
Replies (37)
swez on 08/1/2007 08:52:19
That is typical of most bandpass designs. We get a narrow peak and steep angle slopes above and below the BP region. Depending on the application, this could be good, not so hot or not very usable.
If this were a HT box and designed for deep lows, it would be great as long as the front mains could make up the upperbass region and above.
If for mobile audio, you may wish to adjust the tuning parameters. 20 Hz. is inaudible, but we can feel it. However, there is little music content in this range. DVD movies with lots of high impact subsonic energy would be a likely source for below 35 Hz. (But not most music)
Here, consider shifting the low pass tuning side (F3L) upward so that it's more like 30-40 Hz. The upper region, (F3H) might be a lot better in the 75-80 Hz. range
On the high pass side of the box, 50 Hz is not bad, but closer to 75 - 80 Hz would be better for mobile sound. It also depends on the Mid/high speakers used to fill in the rest of the musical content range. A 6.5" round or 6x9 ovals can do a fair job at ~60 Hz. Smaller speaker formats will struggle below 80 Hz.
Can you fill in the SPL vs Frequency plot numbers in the following ranges? Where is F3L & F3H on your plots now?
20 Hz = xx dB SPL
25 Hz = xx dB SPL
30 Hz = xx dB SPL
35 Hz = xx dB SPL
40 Hz = xx dB SPL
45 Hz = xx dB SPL
50 Hz = xx dB SPL
55 Hz = xx dB SPL
60 Hz = xx dB SPL
65 Hz = xx dB SPL
70 Hz = xx dB SPL
75 Hz = xx dB SPL
80 Hz = xx dB SPL
Swez
MrBrownstone on 08/1/2007 18:30:48
Second guess the Bandpass altogether?
Why are you wanting a bandpass enclosure? basically, it's a one-note wonder...or as close to it as possible.
Almost ALL standard vented enclosures will give you all that you need from this design. I guess my questions is why are we needing a bandpass setup?
swez on 08/1/2007 19:02:58
Not so Grand Pooba... (Mr. B)
A very well designed BP system can be just what the doctor ordered if we define the operating parameters well. NewB is on to something and just needs to shift his tuning parameters to nail it down good.
To the contrary, when a guys knows his stuff and uses a good computer modeling program to design a high impact BP enclosure, it can rock well and stay pretty flat in the BP range used.
Yes, it takes some time to plug in all the T/S parameters and then plot the best curve for the application, but if one can get a solid 30-80 Hz plot that is 4-6dB above using a simple ported/vented system, he's done something note worthy.
NewB.... proof this one out as best you can. If it works, something can be learned by the process. If it does not work out, at least a good effort was made.
Swez
SQLThump on 08/2/2007 02:36:40
NewB, what subs are you planning use do with this box? I have always liked bandpass, and that design look sick.
Victor on 08/2/2007 02:41:15
ooopsss...!!!!
Just a suggestion here newB.... that design is a 6th order BP... it is known to rarely exhibit a perfect bandpass response, there is going to be some sort of out of the band response in its output...you may need a notch filter to avoid this out of band noise.....6th order BP are also know for the most poor transients when compared to all other types of enclosure designs...
like in a ported design its likely to unload a sub below tunig freq here the chances to unload increases as both the Vf and Vr are ported and tuned differently.....
i would suggest going with a 4th order BP if space permits...
Victor....
6th order BP are rarely used for high end audio systems they are only used for low freq reinforcement in HT and multimedia applications...
http://www.diysubwoofers.org/bnd/bandpass.zip try using this calculator.....
newB on 08/2/2007 04:30:14
ok so here are the updates- first off- THE PIX OF COURSE!
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00957.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00963.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00960.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00977.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/audio/DSC00978.jpg
ok here are the acoustic notes.
the high tune sounds good- i like it. it has good output and i dont think i'll mess with it as of now. the lower tune is definatly to low. i didnt get any output from that port unless the freq dropped to the 20s. so i ended up with a crappy sounding box-
to compinsate- i'll be cutting down the lower port and raising the lower tuning frequency to the Fb and possibly packing some fiberfill in the smaller chamber (depending on how testing goes)
jury is out- build result pending.
-Drew
newB on 08/2/2007 04:46:58
correction.
the voice coils are wired wrong. will be changed and i'll give another update
-Drew
Victor on 08/2/2007 06:21:36
good going.. if you have the equiplements i would like to see a freq vs db plot in an anechoic room... this will give u the actual performance stats...
if it is flat enough in the frequency band desired then youre definitely successfull in building a 6th order BP.. is there any audible out of band noise???
Victor...
newB on 08/2/2007 06:26:43
yes. but i still have extensive tuning to do for this setup.
so i'll see what i can do-
-Drew
MrBrownstone on 08/2/2007 12:15:50
Swez
The question was why bandpass? There are some great reasons for BP and you didn't see me ****ting on his post like you did mine? This design was popular in the early 90s when everyone was trying to get more out of a speaker...before power went from $700 100Wx2 to 1000Wx1 with 40% less current draw.
I'm not saying the application will or won't be successful, but we need to know why we're doing it. i.e. are you using a sniper rifle or a cannon? Both have different applications, but why build a cannon when you need to crawl through the forest and sneak up on someone?
What i'm trying to say here is that the physics haven't changed. We still can't eliminate gravity on earth without dispersing it's mass, and with these enclosures, we still can't make them with better transient response than standard vented or sealed enclosures.
Also, we CAN'T make them handle the power any better than other enclosures. So, just exactly what CAN we do?
1. Lower power handling
2. Decrease Frequency response to a more limited range (1 octave)
3. Decrease the accuracy of the bass response
4. Decrease the input power required for Xmax
What's the matter with you, man? Walgreens run out of Correctol & Depends :-)
It's not a matter of 'booking up'. Bandpass has been around and so has the software necessary to fine tune the design. What we need to know is the application. Why do we need this design?
Few things we know:
-Volume: BP takes the total amount of both a sealed AND vented enclosure
-Advantages of this design are a high efficiency over a small range of frequencies and some filtering characteristics.
-Disadvantages are decreased frequency response, less accurate reproduction, extreme complexity in design and assembly, larger enclosure size, greater woofer unloading and decreased power handling.
You can TUNA melt, but these boxes have a maximum benefit. This is why most folks don't bother anymore. The design was purposed to get more efficiency, but at the cost of accuracy, power handling & frequency response.
I guess the real question is, do we want a box that produces 30 to 50Hz? if so, Frickin brilliant!! If we don't want a whole lot of quality sound, Fricking brilliant!!
Other than that, they've made a 'New & Improved' typewriter. If you want one, I know where you can get one.
See my point? if not, please don't go off 1/2-cocked with a vendetta until you know what you are shooting at.
I'll bet you $1000 bux we can design a vented enclosure and use the existing crossovers & eq options in most quality amplifiers to accomplish the same things you're trying to do here.
Please don't take the bet. You'll be out $1000 and 40 hrs trying to tune a donkey's hee haw into a swan song. Not to mention the $1000 extra in boxes, audio equipment and lost time invested.
newB on 08/2/2007 14:32:35
whoa whoa....
the reason I built this box was because
1) i wanted to continue my experiece building boxes and liked the challenge the BP box offered
2) best use the 150watts available to push good output from 20-50
his old box is 1.8cuft per chamber tuned to 32hz and was plenty loud, SO, if i cant tune this BP quite right he can always drop that one back in GRIN
i'll keep a post up later this afternoon when i flip the wiring, and double the power (hopefully)
-Drew
swez on 08/2/2007 15:52:54
As Vic stated, this is a difficult box to get a wider range of usable frequency range you may desire. A 4th order BP is a bit more predicatable, but dual tuning a 6th order BP will be challenging for sure.
It seems to me, the ideal option here is to get the F3L up to about 30-35 Hz. The F3H side of the slope would be great if that could be moved upwards of 70 Hz or a tad higher. If that can be done by changing port lengths and still offer a reasonably flat response curve between say 35 - 70 Hz, this might be a neat project. To obtain this performance, we often need extensive notch filters to smooth out peaks and dips.(Ripple affects) Only the designer, builder and user can determine if all that is worth the bother.
As Mr. B points out, used a few BP designs for Pro Audio installs and find them lacking in clarity and overall fidelity/punch too. However, to give some decent low bass in larger rooms, they do work well if we are able to bring the Mids in at the crossover point to fill in the gaps. That often takes an RTA and lots of PEQ power, (Notch filtering) to fill the room with a well balanced audio content. (It's not easy as each room/space has its own quirks to work with)
Swez
PS B, we both have thick hides and I did not intend to crap on your head sir. (Yes, I was direct, but not vindictive... it's not my style) However, if you feel like I did crap on your head, I appologize and do respect you as a man and a talented one at that! (We have known each other a LONG time and it's OK to agree that we sometimes disagree) Yeah, been having some rough days of late, but that's life. If I was too brash, accept my humble appology and let's move froward.
What I am asking here, is that we post information that leads the reader to usable and workable solutions. If there are none, then state the case and why. If that is possible, great! I hold no malace toward anyone here. We do not need a pissing contest on the site and if you wish, we can discuss it privately. (E-mail or phone) In fact, I will call you in hopes of clearing any misunderstanding up. Good frienships are hard to find and that is more important to me than being wrong, right or otherwise. We are probably saying the same things, but in different ways is all.
Victor on 08/2/2007 16:58:46
dont take this to heart .... its a mere dis agreement over a subtle issue.. wether BP are effective or not it ultimately depends on the end user..
if he wants it .. as techies its our duty to show them the pro's and con's of it... and if he yet wants to do it.. i guess we shud stand by him and try to provide him with as much help as possible..
if it works out its something new we learn and if it doesnt he learns it the hard way..... CHILL guys..
Victor...
newB on 08/2/2007 17:52:26
so here is my pan of attack for when he gets off work.
1) fix wiring and bring power to all four voice coils [haha]
2) then do an amp swap and double the power to the pair.
then sample.
if its still not performing to my liking i will increase the bottom port to ~32hz and increase the top port to ~80
and test again!
plenty of ABS/PVC lay'n around so im not to worried
-Drew
swez on 08/3/2007 00:01:19
Worth a try. In this case, you'll be cutting pipes shorter in both chambers. (Change tuning parameters this way)
One thing I am not certain about, is the "phasing results" you'll get between the front and rear chambers. That's a study in physics I cannot comment on. However, adding some polyfill to the rear chamber is often used to dampen rear wave reflections inside the box and smooth out the ripples of a given frequency curve in that segment of the output plot. That might help along with your other mentioned plans as well.
Keep us posted OK?
Swez
cplkittle on 08/3/2007 01:24:01
My friend and I had alot of fun with an adjustable 4th order bandpass box. I can't find a picture of it online, but the sub was mounted in a box without a back on it, and placed in a ported box where the position of the sub could be moved anywhere along the length of the box and screwed in place when fine tuned. It was pretty interesting. The inside box had to fit pretty tight against the outside box to prevent the air from flowing around the edges, and even though it wasn't airtight, it gave a really noticeable difference in sound when moved just a little. We played a 33Hz test tone and slid the speaker until we got a +5dB gain from the port. This is also a good way to find the cabin gain peak frequency.
Victor on 08/3/2007 03:05:04
That is a very good concept there kittle. have seen a few DIY projects documented on the internet of a similar sort. and i am sure they must be fun building and experimenting with....
one surely gets a lot to learn from it even if the box doesnt work well in ur car audio system... i am sure newB is going to have a similar learning experience ... many of us like to actually do it , not fearing failure and learn in the process...
though.. the deeper u will get into BP enclosures all its Con's will poke u like a thousand thorns .... specially if u are a SQ guy.... one certainly wudnt want to trade off a lot of other things just for a few extra db's over a limited bandwidth...
handling detailed issues like tuning, phase difference , time lag, cancellation, reinforcing of sound waves, unwanted bumps in freq graphs, designing notch filters or BP filters to smoothen out the curve and eliminate out of band noise...
it wud not be an easy task to go through all this pain , to learn a lot of electronics and physics and work out a lot of math... but if you are bent on doing it then it definitely is a challenging task capable of giving a lot of self satisfaction at the end of the project..
nothing that is impossible..
personally i have gone thru all this and at the end of it,, just like MR.B, realised its not worth going thru all that pain just for a few extra db's over a limited bandwidth...
instead would prefer going with heavier amplifier and a better sub in a sealed or ported design for a wider range of freq performance...
.......................................................................................
BP is a very old concept.. basically developed to get higher outputs when not many high power amps and subs were easily available for affordable prices... a very efficient way to get a low power system sounding loud.....
using a BP back then made more sense then using it in these developed product markets... yet when u want more SPL with lesserpower BP is definitely a way to go, but with a lot of trade off... ofcourse beggars are not choosers, cant have it all at the same time...
Victor...
There is one design that has really impressed me in terms of SQ and SPL , very difficult to design tho... those are Quater wavelength Transmission Line enclosures.... i have personally auditioned a few designed by experts and found them amazingly sweet . SQ of a sealed and SPL of a ported enclosure.. a very balanced mixed...
dont seem to find the time with money matters being more important as of now, but some day i wanna start experimenting with those....
newB on 08/3/2007 03:19:41
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00983.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00985.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00986.jpg
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00987.jpg
-Drew
newB on 08/3/2007 03:21:40
as you can tell after Serious Frustration and plenty of pent up anger we decided (we being the owner of the car) to trash the idea take the 45$ hit and start again. (yay)
no regrets
ive learned a lot during this build- as far as pure construction goes this has been my most solid enclosure yet. down to the 32nd of an inch of any given corner or any given length was exactly as it was drawn up on Sketchup (which is an amazing program)
-Drew
Victor on 08/3/2007 04:04:01
are u trying to pee into the box here... THINK
http://i40.photobucket.com/albums/e216/saxwonder05/DSC00987.jpg
GRIN
newB on 08/3/2007 04:07:32
thats not me- but the owner of the box.
imaginary poo with imaginary stench.
it was horrible
-Drew
Victor on 08/3/2007 04:09:34
if u are really wanting to build a BP... try a 4th order alignment...
the wicked one is a difficult construction but very very efficient and better of than many other BP designs..
its a horn loaded BP....
http://www.decware.com/whorn.htm
http://www.decware.com/whornok.htm
though it wud be a huge box if u want to use 2 x 12"ers....
the wicked one has a dedicated forum too, lots and lots of info there on it as well as other designs.... worth being there...
Victor....
Victor on 08/3/2007 04:12:24
what exactly went wrong with this.... ???
where did u face a problem???
newB on 08/3/2007 04:17:06
we just couldnt get it to sound as good as it looked on WinISD. it was horrible sounding. im sure there are 1,000 possibilities why (as previously stated) but i just couldnt seem to eliminate the variable that was restricting the output. so we opted to take the 45$ hit and try again something more simple.
maybe a spin off his other vented box with better ports and a higher tuning.
-Drew
Victor on 08/3/2007 04:26:21
what is the freq range u are aiming to boost..??
Victor on 08/3/2007 04:26:59
do u ahve yahoo or msn or skype messenger.. its better to chat real time...
newB on 08/3/2007 04:40:51
AIM/msn me at
Saxwonder05
-Drew
Victor on 08/3/2007 05:30:48
seems cant add u to my msn....my msn id is ...
victorexports@hotmail.com
swez on 08/3/2007 09:45:54
Hum, the pics say it all...
BTW, did you ever test the box w/o installing it into his trunk? Sad to see all that effort turn out so unsatifactory. Back to the old drawing board.
I've heard of "burying the hatchet" on a matter, but this one has a twist... "bury the claw hammer"? (Deep into the top of the box's top) That's a fresh concept. lol
Swez
Victor on 08/3/2007 10:29:52
can u give us the specs of the subs u are using.. and lets see if we can come up with somethign interesting and performing at the same time...
Victor...
Victor on 08/4/2007 04:09:54
let me just give u some info on how to select an enclosure system... one cant just throw in any subs in any kinda enclosure.. there are specific parameters that guide the selection of an enclosure for a particular sub....
T/s parameters as you are aware of.....
Qts = total Q of a driver at Fs (resonant frequency).
Q = relative damping of a driver.
horn loaded Bp, 6th order Bp, quasi 8th order Bp and ( other higher order alignments ) best works with drivers which have Qts < 0.3
Ported or vented systems perform best when used with drivers having Qts between 0.3 and 0.4
drivers with a Qts around 0.4 work well in sealed as well as ported/vented systems.
drivers with higher Qts above 0.4 are usually best suited for sealed systems.
4th order bandpass systems can work well with drivers with any Qts between 0.3 to 0.6.
drivers with Qts above 0.7 are usually best suited for free air or infinite baffle use.
hope next time you and your friend decide onto building any enclosure look into this and then relate it to the specs of the subs u are using before starting to build....
if certain technicalities are ignored then its always a shot in the dark...
Victor...
hope u dont learn it the hard way anymore and are open to first learning on paper sheets before u start cutting MDF sheets...
newB on 08/5/2007 01:23:55
i'll have to save this topic. a lot of very useful information on that last post victor.
the subs i was using are TOXIK STREETs.
(( toxikaudio.com ))
the specs are online
-Drew
Victor on 08/5/2007 07:25:22
true... but which ones?? the model number?? please give complete info...
swez on 08/5/2007 08:21:17
STR1242 Street series, 12's. They do list some T/S specs on the web site as well. (2+2 DVC's, 300 RMS)
http://toxikaudio.com/
Swez
Victor on 08/5/2007 16:10:46
Those subs are per my calculations....
if you want to make a 6th order bandpass for one of those..for car audio use.... it would need...
Vr = 1.75 cuft (Net rear Volume)
Fr = 35Hz ( Desired rear tuning freq )
Np = 1 ( Number of ports )
Dp = 4" ( Diameter of ports )
Lrp = 12.5" ( Length of ports )
Vf = 1.25 cuft (Net front Volume)
Ff = 70Hz ( Desired front tuning freq )
Np = 1 ( Number of ports )
Dp = 4" ( Diameter of ports )
Lfp = 2.5" ( Length of ports )
This enclosure will give you an average 6db rise in freq between 35 to 70Hz in an anechoic room...and a 18db per octave roll off...
considering cabin gain and resonant freq of the car you could get around a 9db total acoustical gain in that freq range.....
means each of these subs will occupy a 3 cu.ft internal space if you want to build an optimum 6th order BP for it....
2 subs and 2 encl means twice of everything.....THINK
---------------------------------------------------------------------------------
Anyways, if you want to chuck the idea of a 6th order BP... I would suggest you go with a well tuned slot ported box for these subs.... COFFEE
Victor...
swez on 08/5/2007 22:27:42
I think you meant to say cabin gain of additional 9dB + 6dB gain from the BP enclosure = about +15dB, 35-80 Hz. (depending on cabin resonance)
That is a substantial gain in efficiency. Is this not a small format SUV as well? If yes and the rear seats are lowered, cabin gain would be closer to +15dB.
Swez
Victor on 08/6/2007 02:43:12
thats a huge bump and can sound very booooooomy....
also its a huge enclosure for this sub.... this sub can perform decently well in a 1.5 cuft ported enclosure..that means we shall be occupying twice the volume a total of 6 cu.ft for 2 subs.. thats a lot of space to give up in a small car....
why would we compromise on quality, shall be giving up a lot on transients... you wont be getting very clean and crisp punch from this encl...it will just be heavy heavy bass reinforcement... something you can throw in the car to feel test tones..... not something one can use for regular day to day quality music listening..
Copyright ClubKnowledge 2009 * All Rights Reserved
