hi guys!
first up, i'm building something up purely for spl. not for sq at all.
is a 100mm diameter port big enough for a single 12inch sub? do i need to go larger?
i have my heart set on some earthquake subzero 12" subs for this little project.
i dont know how important it is but the enclosure i plan to use will be around 50-55 liters or so and the ports will be flared at both ends. i guess i'll try to tune it and between 40-55hz depending on the situation. the port itself will be fully external of the enclosure.
any ideas or tips guys?
first up, i'm building something up purely for spl. not for sq at all.
is a 100mm diameter port big enough for a single 12inch sub? do i need to go larger?
i have my heart set on some earthquake subzero 12" subs for this little project.
i dont know how important it is but the enclosure i plan to use will be around 50-55 liters or so and the ports will be flared at both ends. i guess i'll try to tune it and between 40-55hz depending on the situation. the port itself will be fully external of the enclosure.
any ideas or tips guys?
At that relatively high tuning frequency with a high xmax driver it's nowhere near enough, SPL needs ports just as big as you would with SQ as the problem becomes restricted port operation choking SPL, rather than noise.
I'd guess with such high tuning you are going to be looking at two 100mm diameter ports.
I'd guess with such high tuning you are going to be looking at two 100mm diameter ports.
You better download some software to calculate the port. The port size is very important. Not port itself but mass of the air that is inside the port. Yor goal is to design the port in a way so back side of woofer push the air and it comes out of the port in phase. In you case port size ( air mass) is very important🙄
I think the next step is to watch and read a few tutorials on hornresp to work out the best flange for both ends of the port. has anyone stumbled apon a good tutorial on how to use hornresp for a complete beginner of the software? or know of any other good software to work out a good flange?
really keen on learning about designing horns and the like.I've read allot of theory but don't know how to implement it. also, while I'm not bad with maths, I don't like doing it thus the software lol
really keen on learning about designing horns and the like.I've read allot of theory but don't know how to implement it. also, while I'm not bad with maths, I don't like doing it thus the software lol
What are creating? A monster?
The idea is ( this is how I see the problem)
1. you get the driver with data sheet, some basic parameters
2. you download the software or sort of it and calculate the box
3. you prototype it, close to calculated date as possible
4. you connect it to your amp and realize that it sounds like a rubbish
5. you look for some method to measure the complete box resonance freq and other parameters ( some sort of, AC generator, AC voltmeter, R- divider, that you apply the voltage, change frequency and look for spikes, something like this)
6. you try to understand why real parameters dont match the calculated ones.
7. You try to adjust the port, box or do some sort of reverse calculation
8. After few days you grew frustrated and want to drop it, at this point you must be very patient, do not allow your inner devils to over take your mind!
This is how I built my speakers. And dont forget to put acoustic absorbs into you box, to avoid parasite oscillations
p.s. my opinion, personal, it is better not to have crazy sub that can push tons of air straight to the moon but have it in phase with you front speakers. It is so annoying when front and sub play differently due to phase lag.
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What are creating? A monster?
The idea is ( this is how I see the problem)
1. you get the driver with data sheet, some basic parameters
2. you download the software or sort of it and calculate the box
3. you prototype it, close to calculated date as possible
4. you connect it to your amp and realize that it sounds like a rubbish
5. you look for some method to measure the complete box resonance freq and other parameters ( some sort of, AC generator, AC voltmeter, R- divider, that you apply the voltage, change frequency and look for spikes, something like this)
6. you try to understand why real parameters dont match the calculated ones.
7. You try to adjust the port, box or do some sort of reverse calculation
8. After few days you grew frustrated and want to drop it, at this point you must be very patient, do not allow your inner devils to over take your mind!
This is how I built my speakers. And dont forget to put acoustic absorbs into you box, to avoid parasite oscillations
p.s. my opinion, personal, it is better not to have crazy sub that can push tons of air straight to the moon but have it in phase with you front speakers. It is so annoying when front and sub play differently due to phase lag.
i totally agree with you! HOWEVER! my plan is to enter SPL competitions. there are lots of rules for spl comps, and one is that the class i am entering; 1000wrms, says that i can only have a single woofer. so my plan is simple. my enclosure will have 3 openings; two for speakers, one for a port.
the enclosure will have 2 configurations:
1, when i'm doing comps, i have a single woofer (as per the rules) and a port. the hole in the enclosure where the second driver is usually attatched, i will simply screw a piece of wood/baffle to cover and seal it, converting the enclosure to a single woofer vented enclosure.
2, when i am NOT in comps, and just driving around, i have two speakers in the same enclosure and seal the port hole with a piece of wood, as i did for the second sub hole, for comp use. this converts it to a sealed box with two drivers.
this gives me the best of both worlds.
as you probably know, the enclosure for a sub box for the same driver is ROUGHLY doubled for a vented enclosure versus a sealed one. (well, what you can get away with anyway!) this works perfectly with my plans!!! mwahahaha!!!
as such, all i care about is spl. sq can go out the window for pure DB at a tuned frequency! i plan to also take my old JBL 15", play a sweep from 20hz to 80hz and record the sound output in an open field. then place the speaker in my spl competition car, record the sound. i then look at the two frequency responses, see where the peak is, and tune the enclosure to that. that should, at least be a good start.
if i put two subs in the same enclosure and block up the port to convert the vented enclosure to an sealed enclosure, i should have a nice punchy system. when i pull one sub out and put a port in it, i should have a crazy spl machine that sounds like poo but wins comps.
also, with comps, i would generally turn off the front speakers as they would simply use power that could go to the subs for spl. i'm just getting into it, but i wanna give it a good go, you know 😉
edit: also, in the sealed box config, i'll have acoustic fluff, but in the vented config, i take it out as extra dampening equals lower spl.
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what about this?
i read somewhere, long time ago, that it works like atomic bomb. But it is extremely hard to fine tune it
i read somewhere, long time ago, that it works like atomic bomb. But it is extremely hard to fine tune it
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I thought about the various band pass enclosures, but I can't make them easily out of fiber glass and can't convert it to a sealed enclosure easily
btw, i need to make it from fiber glass because of the vehicle it is going into is quite limited in space and the fiber glass can match the internal contours of the car interior quite easily. anso for the same strength as wood, it is ALOT thinner, a piece of fiber glass 10mm thick would easily be as strong as a piece of mdf 30mm thick, with the sacrifice of Being dang heavy. (but i doubt more heavy then an enclosure made as strong with mdf) this means i can utilize the space in the vehicle alot more efficiently and still have a "practical" vehicle that i would simply not get with a flat sided, thick timber enclosure. the other sacrifice is due it not being a flat sided box like enclosure, working out the enclosure size is tricky at best, so trying to make a band pass out of fiber glass would be beyond my skill, patients and f**ks to give to get it right 😉 one day though, i WILL build a band pass and get it right 😉 there is a bandpass calculator that runs in bass box pro that looks quite promising, but as i said, not for this project
Hi,
I don't know where such nonsense is coming from.
A 4"and flared port will be fine with a 12".
FWIW the lower the tuning the bigger the port
you will need, the higher the smaller it can be.
rgds, sreten.
I don't know where such nonsense is coming from.
A 4"and flared port will be fine with a 12".
FWIW the lower the tuning the bigger the port
you will need, the higher the smaller it can be.
rgds, sreten.
damn lol so the speaker is not really going to "breath" better with a 6"port? no matter the spl of the 12"? I'm planning to get a pretty silly sub with a lot of xmax.
keeping in mind I don't care about sq with this setup, just Spl. pipe organ harmonic resonances are ideal.
A tapped horn (TH) will have the highest specific SPL capability for a given power, if you can get the right driver for it. A bass reflex or band pass box cannot compete with the efficiency of the TH due to the smaller radiating area of the port on a BR. In a tapped horn, the huge mouth is the port. Think of it as one huge port and box combined.
Do you have a low freq extension requirement?
Do you have a low freq extension requirement?
again, I'm in total agreeance with you about the horn idea however there a two reasons why a ported enclosure is more practical in this particular project:
1, a horn big enough to do the job will be too big to fit in the vehicle AND will also not pass the rules of the class I plan to enter due to the size (it's going into a Ford xr6 ute which is tiny inside, must not pass the "B" pillar, must be no closer then 300mm from the roof line etc )
2, I want it to be able to be converted easily from a speaker system capable of crazy Spl at a specific frequency with a single 12 inch driver, to a nice sounding flatish responding system with 2 x 12 inch drivers. the easiest and most practical way, without building two completely different enclosures is being able to set it up as a vented enclosure with one driver, and a sealed enclosure with 2 drivers.
low frequency extension is kind of redundant in this situation as sound quality will not even be a thought, just spl at a specific frequency.
also remember the microphones that are used at the competitions are placed on the passenger side wind shield, no part of the enclosure can pass these b pillar, meaning that the microphone will be around 1.2-1.5m from the speaker. I mention this because I feel perhaps a horn, unless it's used to focus the sound directly into the microphone, Ms waste energy filling the rest of the car with sound. just things to think about i suppose. have a flick over my other posts to get up to speed with the sillyness I'm doing 🙂
1, a horn big enough to do the job will be too big to fit in the vehicle AND will also not pass the rules of the class I plan to enter due to the size (it's going into a Ford xr6 ute which is tiny inside, must not pass the "B" pillar, must be no closer then 300mm from the roof line etc )
2, I want it to be able to be converted easily from a speaker system capable of crazy Spl at a specific frequency with a single 12 inch driver, to a nice sounding flatish responding system with 2 x 12 inch drivers. the easiest and most practical way, without building two completely different enclosures is being able to set it up as a vented enclosure with one driver, and a sealed enclosure with 2 drivers.
low frequency extension is kind of redundant in this situation as sound quality will not even be a thought, just spl at a specific frequency.
also remember the microphones that are used at the competitions are placed on the passenger side wind shield, no part of the enclosure can pass these b pillar, meaning that the microphone will be around 1.2-1.5m from the speaker. I mention this because I feel perhaps a horn, unless it's used to focus the sound directly into the microphone, Ms waste energy filling the rest of the car with sound. just things to think about i suppose. have a flick over my other posts to get up to speed with the sillyness I'm doing 🙂
as I mentioned earlier, I will be tuning the enclosure to somewhere between 40-55hz, I haven't decided yet. I still need to work out the resonant frequency of the interior of the vehicle.
Hornresp will tell you the approximate air speed in the port. IIRC the recommended maximum for HiFi is 17 m/s. Just round off the ends and avoid flat and wide. As close as possible to round or square section is one of the goals.
40-55 Hz is quite reasonable, and should not lead to extreme port dimensions, if the box size is also reasonable.
40-55 Hz is quite reasonable, and should not lead to extreme port dimensions, if the box size is also reasonable.
thanks alot for that!! but what exactly do you mean by flat and wide? i have my own ideas of what shape the flair should be, but that is not based on any facts, just me imagining how the air would most easily flow in and out of it. my initial idea was to get a flare basically made of 100mm pipe bends arranged around the edge of the port. that shape anyway, its construction would be a little different but you get the idea.
is there a better shape? i usually see something similar, but it flattens out at the front of the flange instead of continuing the radius around like it would with the pipe angle i mentioned.
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