# (big post) DIY 2x12 cabinet. WinISD. Optimal volume, SPL/cone ex. curves, tweeter, filters, etc...

Discussion in 'Amps and Cabs [BG]' started by Caneestra, Dec 11, 2019.

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## What option would you prefer?

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1. ### Caneestra

Dec 10, 2019
Яussia
Hello everybody!

We play mostly metal in a garage (4-string bass tuned in D), where my old Ibanez sw65 can work only with both gain and volume knobs cranked out to max. So I decided to upgrade my stuff and to have big reserve of power now.

I've got an old Peavey Mark VI bass amp (250W @4Ohms, 400W @2Ohms; specification here) and I want to make a cabinet by myself.
I'm going to use two of paralleled Celestion Pulse12 speakers, but choosing parameters of enclosure appeared a big deal for me.

Chapter I

I used winISD 0.7.0.950 app to make some calculations, but the thing is that I don't know to what exact parameters to aim.
I tried to roughly calculate existing commercial cabs, but I was confused by their's cone excursion calculated by WinISD - it reaches Xmax in about 40-60W (but cabs was rated up to 400 and more!). So by that I know that strict adherence to restrictions is not so necessarily. But where the optimum limit is?

My 1st approach was to design a cab where cone excursion never reaches it's Xmax at 250W above 40Hz. It was only 66 liters (2,33 cu.ft) box. But SPL/transfer function curve wasn't good enough for bass (I think so).
2nd was the other edge - to make optimum SPL curve. Box parameters are 140 liters (5 cu.ft). Both boxes are tuned to 46Hz.
There are few intermediate options displayed on a screenshots.

Transfer Function Magnitude:

Maximum power:

Cone Excursion @250W:

legend
Red: 140 liters (probably the best SPL. / Cone ex. > Xmax, too big to carry and place, I think)
Green: 115 liters (probably the best SPL. / Cone ex. > Xmax, a bit bigger than I wanted)
Blue: 90 liters (my favorite at the moment, 200W is enough (some distortions at 200-250W is not scary) / not sure about dense-bass sound)
Purple: 66 liters (best size, sure it won't break speakers / doubtful performance)
All boxes are vented, tuned to 46Hz, 250W input.
Note: adding 2nd order butterworth highpass filter set to 45Hz fixes cone exc. under 40 Hz, but I don't know if it's necessary.

So, few questions to respected public over here.
1. Should I care so much about reaching Xmax? Xlim is unknown. I think I won't use amp at max power, but it's principal for me to be able to handle all power I have (same feeling when having more powerful car - you will not use all of your 220 h.p., but you must be shure it can handle it reliably). A bit of unlinear abberations at maximum power is ok for me (I'll use it very rarely), but I strongly don't want to blow something up.
2. what loss of power (in dB) is permissible for bass cab at 40/50/60/70/80Hz? As I said, I play 4-string bass tuned in D. Often with distortion/fuzz. I agree with those who pay more attention to 1st harmonic then fudamental, but now it's kind of beliefs, not proofed. Opinion of experienced people is wanted.
3. Is it really much power given under 40Hz (from bass and amp)? Do I really need to set the highpass filter to prevent any damage?

General question: what option would you choose (poll above)?

Chapter II

Celestion pulse12 is designed to handle freqs up to 3,5 kHz.
1. How to choose corresponded tweeter to 2x12? How to calculate needed power, optimum freq. range, filter and so on? I'd appriciate some examples you probably can recommend me. Instruct links (to learn it by myself) are also welcome!

Chapter III

I often see some kind of cotton wool inside enclosure of a box. Sometimes not. Is it necessary? Or it added only when you should virtually enlarge volume (when you noticed that box is too small)?

P.S.: sorry for my English, it's not my native. I learned it by metallica lyrics

Last edited: Dec 11, 2019
2. ### RedbrangusSupporting Member

Nov 19, 2018
Under The X In Texas
First: there's no need to apologize for your English. As long and complicated as your message is, it is more clear than most of the posts here, and most of those are from native speakers. Second, I think maybe you don't have too many responses yet because the questions you ask are so long and complicated. I can't address everything you've discussed, but I'll offer these (mostly) random thoughts and a few questions:

Are you modelling 2 drivers in the same enclosure? How did you choose the port resonant frequency? Was cost a primary consideration in choosing that driver? (I'm asking because there ARE more robust drivers.)

I voted for the 115L box because I think that's the minimum you can get away with. I agree that a 140L box is too big to tote around, and I'd be concerned that the 90L cab just isn't big enough.

I like your overall design methodology. I don't know much about WinISD but I do know it to be kind of quirky. If possible, you should try to run your models on another app to check the work.

Yes, you're right to give priority to not exceeding Xmax, and IME, flat response down to the lowest octave (40-80Hz) is not as important as some people think. I absolutely do recommend an external, active HPF to get the maximum performance out of the driver/enclosure combination.

About tweeters: A whole kettle of fish in this subject. Personally, I don't see the point of them in a bass rig, but I suspect that puts me in a minority in this venue, and I accept that there are situations that call for them. And I'm an old PA designer, so I know a little something about HF stuff. The usual approach has been to use a compression driver/horn combination with a passive crossover, often just a single capacitor HPF (single-pole, 6dB/octave roll-off) with an L-pad to adjust the HF output...the bass driver is allowed to roll-off naturally. That works well enough--it's a common enough solution in bass cabs, and, with a more complex crossover, is what's typically done in 2-way PA speakers. A common criticism of the technique on this board is that the dispersion of the cone driver starts to narrow beginning at about 1KHz (for a 250mm driver) and gets narrower as the frequency rises, so there's uneven dispersion of the HF in the octave-or-so between that point and where the horn response begins. This is important in a PA speaker, but (IMO) less so in a bass speaker system used on a stage. Again, it's just my opinion. One design approach to address the issue is use small-diameter, cone-type mid-range drivers, but that's obviously a more complicated concept. For my own purposes, if I felt I needed more HF response, I'd go the route of a 2-way box with a 250 or 300 mm driver and one or two 125-150 mm cone drivers and not bother with a tweeter, but that's just my own opinion. (I've done some successful experimenting with this concept and I liked the results, I just don't need anything that complicated for my purposes.) It is possible to allow for using a horn/driver in the design, and then building the box without them to try out the design to see if you really need that option.

Yes, do put some sort of dampening material in the box...I typically start by doing all of the back and two adjacent sides with material that's about 35-50 mm thick. Yes, some people try to compensate for too little volume by over-damping the box, but in IMO the effectiveness of the concept is limited.

I'll close by saying congratulations on your mastery of English...clearly you've had more instruction than just Heavy Metal lyrics. I'm going to presume you took it in high school, but as I said, you do better than most folks on this board, and most of us claim English (or more accurately, American English) as our native tongue.

Two parting thoughts: DO put the drivers in a vertical array. And don't use piezoelectric tweets, for any purpose. Good luck with your design...keep us posted as it progresses.

Last edited: Dec 11, 2019
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3. ### basscookerCommercial User

Apr 11, 2010
Northern KY
Cab fan, hobbyist
Consider that if the cab is +/- 6dB from 65-2.5k you're doing better than a lot of bass cabs that have been put on the market. With 400 watt thermal rating, I really would want to see 300 watts with no excursion trouble above its -6 frequency.

Also, even if you have some peaking on that plot, consider where on the spectrum it is; and how far below flat your response plot is (at that frequency). As well, how that could play into an HPF setting down the road.

If you want an HF driver in there, a second order high pass somewhere between 3k and 3400 should do. But but but watch sensitivity! If you have a 96dB woofer and a 96dB mid/tweet you might not like the result. You have 2 woofers and could bury the mid. Conversely if you had that woofer and a 106dB HF, it could be un-tameable high midrange peaks.

4. ### Caneestra

Dec 10, 2019
Яussia
Redbrangus, thanks!

Step by step:

yes, it'll be two drivers in a single enclosure. Pulse12 just because of it's price and ease to get.
I want to make it "cheap and hard".

I love good sound, but I'm not that kind of musicians who want to know in what time of the year was digged ore from which was made their oxygen-free wires. So we can exclude any a bit expensive/complicated solutions which are not essential for general purposes.
BTW, I tried to calculate delta-12 (many people recommended it, and result was a lot worse).

Port resonant frequency was choosen just by moving this parameter while looking at SPL/max.power curves to pick the best match. Not more.

About external active HPF: I've never seen if somebody used it. Everywhere I can see only cord from amp into a cab... So this solution looks a bit complicated for my purposes ("cheap and hard"). Is it much better than passive? (or even without?) I think I should find a way to measure outgoing signal from my amp to see if it's any part of signal below 40-50Hz. Those graphs are not more than imagine of "what characteristics would be if you input X Hz signal at Y Watts", but of course in reality I won't use frequencies down to 10 Hz as it imagined in plots.
Generally, bass-guitar cannot produce any given frequency at significant level, but the question is "is it possible to run out of limits at all", for example, if I'll gain EQ at maximum level at 80 Hz and push "low shelving" to max and just slap on stings (muted or not) - whould it be enough signal at dangerous zone and level?

I like you idea about 2x5" + 1x12", but I think I'll try another one: to make 2x12 without any tweeter, and If I'll feel absense of highs (with fuzz for example), i'll put it to a cab (already provided this opportunity by design).

General design is inspired by my independent investigation of guitar monitoring during rehearsals. I've found that best way is not headphone/ear-monitoring, but the ASS-monitoring. Really, you'll never reach such control on you bass playing until you sit on your cab/combo.
So that I decided to make it maximum flat. If I want, it'll stay vertically. In other case I can lay it horizontally and stand on it. And I even can make removable screwed legs attachable to wide side to make a great bass-bench!!! (when I just invented it I laughed like a horse)

Also I invented adhustable vents (grey). If I cant calculate narrow shelf-port precisely (nobody can), I'll make some reserve in dimensions to make it possible to adjust after compilation and attach it tight after reaching desirable result (port velocity variaty is taken into account).

____________
P.S.: yes, actually i'm engineer in IT and I must practice outside heavy metal, but it was my main reason to learn english harder in school.

P.P.S. I just tried Jensen Punch (bt-12) and it is MUCH better of 115-liter 2xPULSE12 without any HPF and even in 62-liter box! That's insane! But the price is twice bigger than of pulse12 and two Punches is equal to used TC-electronic BC212 cabinet without any headache, which bury whole idea of making custom cab (as I said, I make it custom not to reach something that I can't get on market, but because I want it "cheap and hard").

Last edited: Dec 12, 2019
5. ### Caneestra

Dec 10, 2019
Яussia
Thanks for response too.
I could not get 300W handling in any parameters combination with this drivers

maybe it is good idea to add 106dB HF with level control onboard? some brands make so.

Last edited: Dec 12, 2019
6. ### abarson

Nov 6, 2003
Santa Cruz
Interesting design. Just make sure to stand it up vertically, not horizontally as you've illustrated.

7. ### RedbrangusSupporting Member

Nov 19, 2018
Under The X In Texas
What this means isn't clear to me. I understand cheap, but what do you mean by 'hard'?
We are in agreement on this. Very much so.
So can one live without a HPF? Sure. Most folks have done OK without one up until now. But it really would enable you to get the maximum performance out of your speakers while still offering some protection for them from over-excursion. Would a situation such as you described, with everything maxed out, make it possible to blow a driver with an inadvertent 'string-slap' or something? Yeah, maybe. Maybe not, but it definitely is a possiblility, and it definitely is going to give the drivers a good jolt. I've seen voice coils pushed completely out of the magnetic gap, a decided failure mode. As far as passive HPF's go, that's not what's typically done. For one thing, the passive components have to be able to handle the high current involved, plus some large component values are needed at that low of a frequency. And remember, it needs to be at least a 2-pole filter to have a steep enough roll-off, which is also going to suck up some of the power from the amp. No, I think an active filter is the way to go if you're going to try to do it...but you can certainly build the box and use it without one.
As I said before, I'm totally in favor of this concept.
This is a good idea...do you adjust the cross-sectional area of the port, or the length of the duct? And I agree that none of the software apps seem to do a very good job of predicting the duct-length of a shelf port on the end of the enclosure...the ones that use three sides of the enclosure itself as 3 of the 4 walls of the duct. So it IS a good idea to make some sort of allowance for tuning it after it's built and can be tested.

Yeah, I get making cost-based decisions--I ran my own business for 40 years. And building it yourself isn't typically the path to saving money...not when there is so much good used gear out in the wild. I would recommend leaving yourself the option of modifying the ports easily, so that if you decide to go to a different driver at a later time, it won't be too difficult to accomplish the new tuning.

One last thought: how does your modelling work out with just one driver in half the internal volume? I'm asking, because, as a rule of thumb, I've always built dual-driver boxes with an internal partition that subdivides the enclosure into two sub-chambers. So each driver is in it's own chamber by itself. I don't know that there's any advantage to that, other than a blown driver doesn't turn into a 'drone' cone, being driven with inverted polarity by the working driver.

8. ### Caneestra

Dec 10, 2019
Яussia
I tried to translate one russian idiom I meant something like "good enough for purpose, but without extra-things", "something was made to do the job, and not to be fancy"

Absolutelly the same (and exactly 1/2 where it should be). Also I plan to do some walls inside as
stiffening ribs, so I can make one wall in the middle as a separation wall. The only issue of this design is that I planned to add (may be) a tweeter in the middle. So this wall will make drilling a hole for it in the center hard.

9. ### JimChjones

Aug 6, 2017
SE England
A note on the internal damping/padding. My very limited experience is that it has a very great effect on the tone, and you need to be prepared to do a good deal of experimentation to get the best sound for you.

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10. ### BogeyBassInactive

Sep 14, 2010
1.8 to 2.3 cubic feet or 50 to 65 liters per driver is good generic volume to look at for a 12"
or as far as alignments look at QB3 or BB4

either making the box slightly smaller or slightly bigger to change Q
tuning 3 to 12 hz above or below FS / resonate frequency of the driver to change Q

or do a generic 2 cubic feet and tune to driver Fs
which is close usually to what BB4 or BB3 alignment is

pretty much your 115L or 4 cubic foot 2x12 good option
tune to the Fs of the driver and call it a day.

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11. ### Caneestra

Dec 10, 2019
Яussia
So.
Sorry guys for such big delay! I've done my cab more than a month ago and I'm glad to introduce it!

At first, I purchased drivers.

I decided to use a tweeter and to make it adjustable (at least two options + off position).
Also I used primitive HPF set to about 3500 Hz. Simple 4.7 uF capacitor (reated up to 63V). Series of powerful resistors (up to 10W each) and on-off-on switch. Center position - tweeter off, up - full power (~16 Ohms added), down - half power (~32 Ohms added).
Dummy option to check wiring.

Wood. I took 21-mm (0,85-inch) plywood, cutted it right in a store (local Leroy Merlin). But before I bought it, I spent few nights allocating parts to fit it in a single sheet (1525x1525 mm). Done

It's garage time!

I was so exited to make is faster that I forgot to make photos of a process. Just few final ones:

Final result:

...and what a beautiful handles design!

Take a look onto EQ. I really proud of my work with calculations.
Yes, WinISD lies. My design allows to change port's width, so I've found that for that area WinISD offers 16 cm port while real port for this frequency was 12 cm. Few experiments and I choose 47-50 Hz box resonance. Final volume was 110 liters.

Sounds great!

Last edited: Feb 19, 2020
rogypop, BeauZooka, Stumbo and 2 others like this.
12. ### StumboGuest

Feb 11, 2008
Cool cup.

Last edited: Feb 19, 2020
13. ### basscookerCommercial User

Apr 11, 2010
Northern KY
Cab fan, hobbyist
Looks great!

Get a grill on there, though, before moving it anywhere! It is absolutely over the top, agreed, but seeing unprotected drivers makes me cringe! It actually physically affects me seeing them, lol. I actually tape a fiberboard disc over my drivers for as long as I can between unboxing and installing, and have slightly smaller cardboard ones I lay over them until the screwdriver is put away. I'm so OCD about it sometimes it takes me longer to install drivers than to assemble the enclosure.

Enjoy that cab, bro!

14. ### Caneestra

Dec 10, 2019
Яussia
Sure! It'll be some brutal grill. I have few ideas, but not sure which one can I afford/find appropriate materials.

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15. ### StumboGuest

Feb 11, 2008
How does your design work so the port width can be changed?

16. ### Caneestra

Dec 10, 2019
Яussia
There was only two big ports on both sides. Then I took a piece of styrofoam and filled hole with it. Attaching pieces of plywood, cutting styrofoam was my "adjusting".
Resonance was measured by giving different sound frequency and observing of cone excursion. I laid cab with speakers up, dropped some sugar (you can use any tiny garbage - pieces of wires, breadcrumps...) on it and changed frquency. On the resonance freq sugar almost stops to jump.
When I determined wanted parameters, I made two П-shape units and put them into a port. This was it.

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