Enclosure design - NOOB

Helloo! I am a noob with DIY subwoofers but I wanna build 2 subs 15 inch. The subs will be used for playing music and for bands (drums and bass) for wedding purpose. Because I own a small car and I am alone I need to find 2 compact, lightweight subs (30-35KG MAX) with goes at minimum 38Hz. I saw that Beyma has an enclosure design for 15LEX1000Nd that is quite compact but i dont know if its ok for music and bands. I saw than the Nexo LS600 enclosure but i dont wanna copy their design.. Some drivers that I found cheaper in my country but i dont have enclosure designs:
BC 15TBX100 / 15TBW100 / 15NW100
Beyma 15LEX1000Fe
Faital 15FX560

If you have something to recommend (driver and enclosure) I would be very grateful. Thank you very much!
 
(sorry for my probably not very good english)

Ok i see you want something compact but i only have the maximum weight. This may vary depending on the materials you use for the enclosure and i don't know a lot about that.
But if you give the maximum dimensions i may help a bit already. I think a series-tuned 6th order bandpass could be compact but it would probably be a bit heavier than a bass-reflex (for example) cause of the "structure" inside.

If you are a "noob" in subwoofer building, do you know a bit more about active filters (DSP) ?
These are almost necessary if you want to play loud without breaking the driver (unless it's already integrated in the amplifier).

And if somehow you plan to build other speakers, take a look at driver parameters explainations, enclosure designs and hornresp tutorials. I didnt want to read all this stuff at the beginning but now i think it's kind of fun.
 
I was playing a little bit in WinISD, isnt that hard to understand it but I have a few question. In this design (i atached the Beyma 15LEX1000ND recommended enclosure) with is a "cross" at the end of the enclosure wall? Is it helping for a better sound or it s just reinforcement?
Also, when building the enclosure, is it matters the volume of the speaker? (to substract from the box volume) or the volume you need is just the enclosure volume without the speaker?
The XO point will be at 120Hz (I will use Pioneer XPRS 10)
Thanks and sorry for the english.
 
What do you think about this enclosure designed in WinIsd? On the second image is the cross i was talking about
 

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The S-15LEX1000 inner reinforcement parts 5&6 cross are cabinet braces to stiffen the walls. Walls flexing reduces output.
If you use thinner plywood to reduce weight more bracing should be used. The braces can have triangular or circular holes to reduce weight.
Screen Shot 2023-09-19 at 3.43.23 PM.png

The rear chamber volume of the cabinet is reduced by the volume of the port vents, driver, and bracing.
The S-15LEX1000 rear chamber volume would be less than 125 liters, a .5 meter cube is 125 liters.

This cabinet probably has an Fb (box tuning frequency) of around 43Hz, if you want a lower frequency response ("at minimum 38Hz") the port length could be increased to lower Fb, but the cabinet will have less low frequency output.
WinIsd may not predict a triangular corner port Fb correctly.
Hoffman's Iron Law for loudspeakers: Efficient, Low, Small, pick any two ;)
 
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GM

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I was playing a little bit in WinISD, isnt that hard to understand it but I have a few question. In this design (i atached the Beyma 15LEX1000ND recommended enclosure)
The XO point will be at 120Hz (I will use Pioneer XPRS 10)
Thanks and sorry for the english.
Assuming using the factory recommendations, which I presume this cab does, then 115 - 0.968 = ~114 L tuned to 40 Hz, so with driver Vas = 113 L and 41 Hz Fs, it's basically a Vb = Vas, Fb = Fs T/S max flat alignment ergo won't have the broadband dip in your sim.

Great! Well within the driver's box loading ~222 Hz desired upper BW limit for a (sub) woofer.

You're welcome!

It's fine and sorry to say that statistically all the non-English speaking/translated folks here 'speak' it better than most of my neighbors now that it's no longer a bastion of 'blue collar' working & off base military officer families it was specifically built for in 1952. :sigh:
 
Depending on how high your budget is you may take a look at higher Bl/Re drivers. From what i designed in hornresp this is a very important factor for getting strong low output in a small box (and not exceeding x-max without filtering above tuning frequency). But it will also need a larger port for the same air velocity.

Edit: the B&C 15SW115 and 15DS115 are some good examples (but the 15DS115 has a very high Le and i haven't calculated its effect yet).

Edit 2: and if the sim shows a peak in the frequency response at tuning frequency you may either decrease the box volume or increase the diaphragm surface so you can even take a look at the 18" variants (which often allow a stronger energy input). Again, don't forget the port air velocity will also probably increase.

Edit 3 (maybe the last one): I used this site to get you a decent list (forget all these car audio drivers):
https://loudspeakerdatabase.com/search/13.0≤size_in≤16.0/qts≤0.34/9.5≤xmax/11.3≤blre
 
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Thank you for all the info! I will build myself an enclosure to learn about it. Two more question:
1) I made a simple box with rectangular air vent volume=114L and Fb=35Hz. In order to get an air velocity < 18 I made the air vent as long as the box width (516mm - 36mm Plywood = 480mm) and the height 90mm but the problem is that I get the vent lenght too long (746mm), longer than the box itself that I imagined to be 600mm depth... How can I fix this? The design is similar to the first photo atached (Driver used B&C 15TBX100)
2) If I wanted to make a triangular vent, how to calculate the vent lenght? In WinISD I have the rectangular and circle only..
Thx a lot!
 

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2) Normally you should have around the same length for the same area so you should just calculate a triangle with the same area (maybe there is a tiny change as for slot port vs round port so if someone can confirm that would be great).

1) Also i read you don't really need to keep the port air velocity below 18m/s for an high output speaker. 35m/s is the general maximum before port compression (no SPL gain above that) and you can avoid turbulence noise by a port flare (but then i don't know how the port length should change but i think is not that much). Anyway the turbulence noise shouldn't be a big an issue with a high SPL speaker (otherwise i think a ton of PA subwoofers on the market would have port velocity issues then).
I also read once that bigger ports = higher port velocities without port compression but that is to confirm (i've read it only once so i keep my designs below 35m/s).
 
I think I got how to calculate the triangle vent lenght.
I put in WinISD an circle vent and found out the dm3 (8 dm3) needed for that tuning then I divided that number by 4 (because I want 4 corner vent so 2dm3 per triangle) than calculate an prism volume to match 2 dm3 volume and found out the length needed.
Can someone confirm this? Thx
 
Hi daniul,
Port tuning frequency is based on the length relative to the port's cross sectional area (and relative to the net box volume).
WinISD just calls this "Cross Area" at the bottom left of the vents tab.
So the way to do it would be to make the total cross area of your 4 triangles the same as the total cross area from WinISD.
In your example from a few posts up of a vent 48cm wide x 9 cm high, you'd have a cross area of 432cm2.
Each triangle therefore needs a cross area of 108cm2, which would result in using sides of 14.7cm (hypotenuse 20.8cm).
The length is likely to be shorter than WinISD predicts as 2 out of the 3 walls of the port are much longer than the other, so the math WinISD uses (which assumes the ports are well away from the cabinet walls) won't quite be right.
The image attached below shows how we can calculate a revised port length based on alternative values of end correction to account for this. Note though that I haven't built a cab based on these calculations to check how accurate they are - so it's probably best to build one test cab first to to check. It would be best to make at least one panel removable so you can get in and adjust port length as need be - either by cutting them shorter (hard if they're in the corners) or gluing in extra strips of wood at the back of each one to make them longer.
HTH,
David.
 

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Winisd assumes ports have no shared walls
and uses common correction factor K=.732
and with flares assumes K= .850

If calculating triangle ports= 2 shared walls
or Slot ports =3 shared walls.

Winisd predicted length is too long.
Use a program like Virtuix Cad
were correction factor is adjustable.

post #13 is well known graph showing
accepted end correction for shared walls

2 walls K=1.728
3 walls K = 2.227

Once you find a driver WinIsd will give
you known alignments.
QB3, BB4 and your done.
To Hit 38 Hz with live sound 15" in
a reflex. It will be a large box.
Not small and light.

38 Hz is 18" territory since Fs will be low
enough. 15" will high tune around 45 to 55 Hz
so dont expect a drop of accuracy near/below tuning.
18" is feasible since reflex will tune closer to 27 to 35 Hz
and will be Filtered/ added Equalization to hit 38 Hz.
 
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Thank you for all the info! I will build myself an enclosure to learn about it. Two more question:
1) I made a simple box with rectangular air vent volume=114L and Fb=35Hz. In order to get an air velocity < 18 I made the air vent as long as the box width (516mm - 36mm Plywood = 480mm) and the height 90mm but the problem is that I get the vent lenght too long (746mm), longer than the box itself that I imagined to be 600mm depth... How can I fix this?
You're welcome!

You need to use the duct math shown here to calculate a full width rectangular vent and deduct the volume loss and width of the center brace. Note that the chart shows some basic WxH slot area tunings with 39 Hz having a whopping 31.373:1 aspect ratio, so assume yours to be a high aspect ratio one also.

If so, this in turn will make it somewhat aperiodic, so typically not all that long compared to round/square or < the pioneer's ~1.273:1 rectangular one.
 
...take a look at higher Bl/Re drivers. From what I designed in hornresp this is a very important factor for getting strong low output in a small box (and not exceeding x-max without filtering above tuning frequency). But it will also need a larger port for the same air velocity.
I'm not sure how higher Bl/Re drivers will benefit Xmax limits, as these are mechanical limits for the driver. Wouldn't a high Bl/Re driver simply reach its Xmax with lower power inputs? Also, aren't higher Bl/Re drivers usually associated with lower Qts values, which tend towards having compact vented-box enclosures with relatively high –3dB cut-off frequencies? A high-efficiency driver with a low –3dB point would normally require a very large enclosure.
 
Yep exactly they wont be small.
real world for reflex 15" is 50 to 65 Hz -3dB
= Midbass.

38 Hz is a 18" with low tuned reflex.
In Winisd wont be more than a 15"
EQ is added to get any where near 38 Hz

Smack Smack boom boom in actual live music
is 40 Hz to 60 Hz

So 15" = Mid bass
With some high cost exceptions.
Fs wont be lower than 35 to 55 Hz
so 38 Hz in a small box is a fantasy.
Since 45 Hz Fs is common for 15" which actually
fits in a somewhat small box.
So that first humpty bump in the impedance
curve is 60 Hz once it goes in a box.
 
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Anyway the turbulence noise shouldn't be a big an issue with a high SPL speaker (otherwise i think a ton of PA subwoofers on the market would have port velocity issues then).
Wouldn't that really depend on how low these PA enclosures are tuned? PA subwoofers may not be tuned to go all that low, as for a 4-string bass guitar the lowest note corresponds to 41Hz or so. Even the lowest note on a 5-string bass guitar is at 31Hz, so a subwoofer with a –3dB point of 30Hz would probably reproduce that reasonably well. Of course, subwoofers for domestic home theatre applications are expected to achieve 20Hz lower limits on a routine basis, but they wouldn't be asked to energize a stadium.
 
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The difference between " hearing" and "feeling"

Bass guitar yes 30 to 40 Hz for open strings.
You actually hear the 2 nd harmonic. 60 Hz to 80 Hz
Which a pluck or picked string goes too slightly
after the initial attack.

15" cabs are tuned around 45 to 55 Hz
for bass cab and they do 60 Hz fine.
Which is what the player actually hears.

Doing live sound for many many years.
Once you put a bass player on a actual sub.
All they do is whine its too boomy.
Because they have no idea or enough note
control to handle a sub or what 40 Hz even
Feels like. Not sounds like, feels like.

For live sound bands, twack twack kick drum
or zoom zoom bass notes are 50 to 80 Hz.
Actual fretted notes and toms around 80 to 150 Hz
With modern boards I high pass both of them
because a 15" MIDBASS wont fill a room with
pressure. You hear the instrument. If you wanna
fill a room with real pressure that a bass player
and drummer will whine about. 18" or 21"
I spend more time for real subs for electronic events.
15" is 50 to 60Hz the end.
For live sound mid bass with 15" 2x15 minimum
6 to 8 cubic feet box. Port velocity is a issue.
Why junk triangle ports and slot ports are common.
Enough port area to get "OK" velocity rating.
Poor efficiency makes them short enough to fit in the box