Can somebody give me a good working set of formulas to tune a sealed enclosure. All of the online calculators i use conflict each other BY A LOT! winISD says a 14.8ft^3 and bass-box 6 pro says 2.72^ft3 Please help! I need the formula to exclude polyfill and it needs to be accurate. I am new to speaker building and giving it a try with some cheap but nice drivers. GRS 12PR-8 PLEASE DON'T DO THE MATH FOR ME AND GIVE THE ANSWER!!! I will probably need these answers for future reference, and i don't want to come here each time i need to do a build. Any help is greatly appreciated. Thanks in advance!
This one GRS 12PR-8 12" Poly Cone Rubber Surround Woofer?
With a Q that high there is no box you can put it in that will produce a flat-response. Even an infinitely large box will still have too high a Q.
An open baffle would be the 1st kind of build you would look to use.
I would suggest looking for a woofer more suitable for putting into a box.
dave
With a Q that high there is no box you can put it in that will produce a flat-response. Even an infinitely large box will still have too high a Q.
An open baffle would be the 1st kind of build you would look to use.
I would suggest looking for a woofer more suitable for putting into a box.
dave
Hey Ron? what would be the purpose of finding f3 if vb is found? And if there is can you please tell me why.
I know I wasn't supposed to but I did the maths for you - or rather Jeff Bagby did 🙂
The attached PDF file is a printout from a simulation of your driver in Woofer Box Model and Circuit Designer v5.0, which is very accurate, based on:
+ Factory TSP
+ Sealed enclosure
+ Vb 3.5 cu ft
+ 140W applied power
+ LR2 HP @ 45 Hz
+ LWT: F0 44Hz, Q0 1.45, Fp 35Hz, Qp 0.707 (easy to implement in minidsp)
This results in:
+ Excursion: A touch above Xmax but presumably within Xmech
+ Max SPL: 115Hz
+ F3: ~ 50Hz
+ F6: ~ 40 Hz
WBCD is freeware but requires Excel. I have had problems getting the spreadsheet to work in newer versions of Excel. I ran this simulation in 2010 in compability mode. Still, everytime I save changes, the graphs disappear so I need to close and reopen the file again to see the effect of my changes. YMMV.
The attached PDF file is a printout from a simulation of your driver in Woofer Box Model and Circuit Designer v5.0, which is very accurate, based on:
+ Factory TSP
+ Sealed enclosure
+ Vb 3.5 cu ft
+ 140W applied power
+ LR2 HP @ 45 Hz
+ LWT: F0 44Hz, Q0 1.45, Fp 35Hz, Qp 0.707 (easy to implement in minidsp)
This results in:
+ Excursion: A touch above Xmax but presumably within Xmech
+ Max SPL: 115Hz
+ F3: ~ 50Hz
+ F6: ~ 40 Hz
WBCD is freeware but requires Excel. I have had problems getting the spreadsheet to work in newer versions of Excel. I ran this simulation in 2010 in compability mode. Still, everytime I save changes, the graphs disappear so I need to close and reopen the file again to see the effect of my changes. YMMV.
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Hi,
Many cheap 12" 3 ways have no BSC and a boom
box bass alignment to fatten up the bottom end.
Many are vented to make it even worse.
rgds, sreten.
The facts of the matter here is there is no ideal box.
Sealed and very well stuffed around 3cuft is about right.
Sealed boxes have just 1.5 parameters*: volume and stuffing. You cut your wood and you get what you get. Visual appearance aside, the bigger the lower it goes. If low bass is still shy, boost it and you'll still end up with nicer sound than any other enclosure.
The sims produce screwball results (esp for sealed boxes) because they have their own priorities - usually related to abstract benefits** as opposed to quality of final sound.
I'm not denying some drivers are more natural for one kind of box or another. But if you have a driver on your workbench, proceeding with a sealed box should lead you to good sound.
Stuffing is essential:
Data-Bass
Ben
*location(s) in room very important... for another day
**"flat" below say 50 Hz is an abstract benefit which is not a key measure of sound quality
The sims produce screwball results (esp for sealed boxes) because they have their own priorities - usually related to abstract benefits** as opposed to quality of final sound.
I'm not denying some drivers are more natural for one kind of box or another. But if you have a driver on your workbench, proceeding with a sealed box should lead you to good sound.
Stuffing is essential:
Data-Bass
Ben
*location(s) in room very important... for another day
**"flat" below say 50 Hz is an abstract benefit which is not a key measure of sound quality
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Any designer that knows what they are doing would never settle for "you get what you get". You can get whatever you want. You need to use the right tool for the job (hint - it's not always a sealed box), but you can get whatever you want.
This is really bad advice. A large sealed box is going to make the driver hit it's xmax limits with relatively low power. Boost the low end and it will be even worse. Chasing the low frequencies with a sealed box is possible and even preferable if you want single digit response, but you need the right driver, expensive high xmax driver.
I already showed you how to make a ported box that has almost identical frequency response as a sealed box, and you wouldn't be able to tell the difference in a listening test unless you turn it up loud enough to get the sealed box distorting badly while the ported box still has plenty left in the tank.
I've told you several times, sims don't have any priorities. The designer chooses the alignment, the frequency response and everything else. If the design is bad it's the designer's fault, not the simulator's.
Sealed box does not necessarily lead to good sound, in fact it can be quite bad. If you take a very low qts pro driver and put it in a sealed box (even a very large IB sized sealed box) you are going to get very weak low bass. You can't turn it up and you can't boost it much because this type of driver typically has very low xmax. If you only listen at 80 db this is fine, if you want more you better be aware of what you are doing in the design phase.
No it's not. If you can get the frequency response curve you need without stuffing and there's no audible resonances within about 1 octave of the sub's usable bandwidth, there's no need to add stuffing. The link you presented shows a minor resonance at 170 hz, well outside the passband of a normal use sub. In this case, if it's still audible after low passing the sub, stuff away. If not, there's no point.
The right tool for the for the job is not a $20 1.26 Qts woofer. But if it's the only tool in the OPs shed (or all he's going to spend) then he should put it in as big of a sealed box (or open baffle) as he's willing to tolerate, and live within its SPL limits (whatever they may be).
+1
I am planning a new build with this: Amazon.com: Infinity Reference 1260w 12-Inch 1200-watt High-Performance Subwoofer (Single Voice Coil): Car Electronics It is one of the better price: performance ratios out there.
I am planning a new build with this: Amazon.com: Infinity Reference 1260w 12-Inch 1200-watt High-Performance Subwoofer (Single Voice Coil): Car Electronics It is one of the better price: performance ratios out there.
here's thejessman's graph for a 1260W in a tapped pipe designed by TB46 http://i.imgur.com/0vxhgqq.png
Nice! Forgot about that. I would be tempted to try that design but building one is a bit over my head at this point. (no drawings/sketches/etc) That dye stain you used on yours was gorgeous BTW.
I was talking more about the sealed box for every woofer for every application that Ben advocates tirelessly when I said "right tool for the job".
But you are correct, the OP's woofer isn't really the right tool for the job either, unless it's an OB or sealed box application. If a sealed box is used it will most likely need eq since the incredibly high qts will create a bumped up response above fs. If that works with the room gain curve to provide subjectively pleasing response then it might not need eq, otherwise it will need to be notched down, not boosted as per Ben's advice. This woofer doesn't have enough xmax to viably boost below fs unless a very low spl is adequate.
It's not an "incredibly" high Qts - perfectly "credible" for a $20 Qts. Manufacturers who use large $20 woofers have the same Qts - and they'll make the box a lot smaller. Like an old MCS "stereo" system. The biggest lesson I took from those days is that if you make the box big enough (about 2X what they typically sold) you could push that hump down low enough in frequency to be "useful". That is, maybe 50 Hz. With the bigger box you didn't have to push the 63 Hz slider up all the way anymore - resulting in more system headroom, actually. Today's fight with a cheap high Q woofer could very well be tomorrow's 20 Hz horn, given enough determination to get that bass (and a few engineering courses under your belt).
When all you had were $12 woofers from McGee and an STK439 drivng them, x-max limited power handling wasn't that concerning. It sounded better than what I could buy. If I had to go spend $279 on woofers and another $1k on instrumentation just to get started or "my project is doomed to failure" I probably would havbe just said "eff it" and put the whole idea of building speakers to bed a long time ago (1978). I doubt that I'd have the three home brew PA rigs I own now - or the Scan-speak towers in the living room.
+1... smart remarks from wg_ski. Obviously his intuition extends wider than his laptop sim screen. In contrast to some others whose intuition does not.
B.
B.
Well... this 1.26 qts is definitely at the upper end of the range, not the highest I've ever seen but well outside the "normal" range. You said yourself it's not the right tool for the job.
I know these cheap high q systems well, they were all I had when I was younger. And these cheap drivers never go very loud, I blew them all up despite the sometimes pleasing bass bump. This continual failure of cheap drivers is a big part of the reason I started learning.
Funny, since I can predict response of sealed and OB drivers pretty well without a computer and you have shown you have no idea. You recommended boost for this driver in a sealed box when it needs cut to even approach flat response. Last week you said drivers in sealed boxes show a clear "whomp up" at resonance, when that only happens with very high q drivers, ironically like this driver.
Back in 2009 when I was still pretty young and stupid I wrote this webpage showing how to predict IB and OB response without a computer.
https://sites.google.com/site/amateuraudio/theory/ob-design
You are on pretty shaky ground here since you don't understand the basic theory. I am very good with simulators as you pointed out, but I don't need a computer to know how this driver will behave in a sealed box. Read the link and if you want to discuss this from a scientific perspective let me know.
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