subwoofer advise

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Moritz Bachmann

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Nov 7, 2019
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hey guys, I need some advices/ help on my next project, a subwoofer for a compact PA-Setup.
This setup is meant for DJ-Monitoring and small gigs, where really high SPL isn´t required.
The Top is not finished, so no measurements here, but it uses a Mundorf AMT and a Beyma 10MC700ND in a closed box (maybe this will be changed to BR, as I have not that much experience on how much SPL is really required, and the Beyma in the closed box will be limited to max 115dB if crossed over at 100-120Hz, acc. to my poor Hornresp skills)
So now to the sub requirements, from most-important to least:
-sound quality (I use a ~400€ AMT and a 200€ Midbass driver-hopefully in a CB, so I also want the sub to be precise, fast, and so on, you know what what I mean)
-compact design, MAX. 150L, better 120-130L
-of course high SPL and good low end but I don´t know what is possible here. I think 40Hz and 125dB would be nice to have, but the two points before are more important

What´s not (so) relevant:
-The driver... everything from 12"-18" is possible, if it can meet the requirements (300-400€ max. are OK if they are worth it)
Multiple enclosures are possible, the price range is planned for two of them, so it´s more like 600-800€, maybe 4 cheaper 12" will do it better than 2x15"?
-complicated build- I have a carpenter and a CNC router on my side
-Amp-Power, there is a LabGruppen FP10000Q waiting to get used (although this might change, as the subs will get an own amp-module maybe)

I started with 12" 6th order BP Designs from B&C and 18sound, but they both didn´t seem good enough, so I tried to re-design them... but I don´t want to built X prototypes, and I know enough about Speaker Design to not think that I can one-shot a perfect BP- design from a "good" Hornresp sim.
Then I came to 15" BR enclosures, the drivers are not that more expansive, and the output from 40-100Hz is compareable.

The Drivers I tried the 12" BP system:
Beyma 12P1000ND

12" BR-design:
B&C 12NW100
Oberton 12NSW600

Drivers for 15"BR:

B&C 15SW100ND/ 15SW115ND
Beyma 15LEX1000/ 15LEX1600
Oberton 15NSW600


Actually there are so many possibilities that I have lost the track many times, so some some advices/ hints for any good directions are very welcomed.
It´s also not that I really WANT to design my own sub (not yet) so if anyone knows, or would share a good design with me, please let me know.

I hope some of you can help me out here
 
input Hornresp.pngoutput Hornresp.png

Those are the Hornresp in-/ output for the 12" BP system, I would really like to make at least one prototype for this design, but I don´t know if it isn´t better to spend the time and money into a good 15" BR design...
 
I still think this is a good, compact subwoofer design. Been thinking about building one to try it out.

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Moritz Bachmann said:
Already thought about this one, but for a single cab it's too large, and I would prefer a little more output for less extention
Click to expand...
Some thoughts:
BP designs may look good in Sim, but what happens if the driver gets hot.
The more SPL you try to extract from the enclosure design the more the response can change with drive level.
Hornresp gives the option to simulate Power Compression.

BR designs on the other hand are pretty simple, not too many parameters.
From your 15" driver list I have not tried the 15SW100 in my own designs, but think one German manufacturer uses them in single and double versions. These subs are quite good driven by PLM+12k44.
 
For a few years I've used 4 x 50l sealed 18s crossed over at 100Hz with about 2kW per pair, which just keep up with Beyma TPL150H/Beyma 10LW30N tops (20l ported 80Hz). I now find it very difficult to listen to any system using ported or horn-loaded subs, such is the accuracy of sealed subs to my ears. One of my acid tests is double-pedal drums such as used by Metallica, which comes through as the brutal machine gun-like staccato it should, not as a transient-blurred phrrrrt-phrrrrrt sound most usually reproduced. (Please don't for one minute think that this genre is all I play!). To my mind, the lowest possible stored energy in a subwoofer system is crucial, but both relfex and horn subs have it in droves.
It is super-quick and easy to build a trial sealed enclosure. Try it - and with the correct EQ and power you might like it!
 
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I don't know if it's possible within your price range, but I'd give the DS range a look as well. The amount of Bl is just monstrous, so you get that "fast precise bass" you want. ;)

In all seriousness, I believe it's a significant step up from the SW series in terms of performance.
 
The 15DS115 would do the job I think. I have tried in in a 6th order BP design. Net volume of the rear chamber was around 80L and first tuning was 37Hz. While 40Hz was the aim (so I have to shorten the port), the 15DS115 was still underdamped at Fb.

If interested, I am selling the 15DS115-8's. The BP design from above was accually not designed around the 115, and I am going for the intended driver now.
 
thank you all for your input.
I think I should give a CB sub a try... with the option to make some BR enclosures later.
My main question is now if it pays off in closed box too, to bet on high performance drivers?
For a comparison, what drivers would you buy with, let´s say 1000€ :

3x 15DS100
3.2x 15SW100
2.5x 15DS115
2.6x 15SW115

2.8x 18DS100

2.7x 15LEX1600ND
3.5x 15LEX1600FE
3.8x 15LEX1000ND
4.4x 15LEX1000FE

any other suggestions? the weight of FE magnets doesn´t matter that much, so if there is a compareable FE driver at lower cost, that would be ok too.

Atm I would try the 15DS100 or the 18DS100 in a dual opposed CB. The-115´s wouldn´t provide that much more output/ control, compared to their price, would they?

Amping will be two 2k Hypex Modules, for just two drivers first, but i guess two others will follow soon
 
I've finally built my first self- designed subwoofer.

I decided to go for the 15DS115, ~90L net Volume and big ports with 3D adapted flares.



The difficult part was actually to make the front small enough that the ports fit within the depth of the speaker, while trying to get as much flare area as possible. A simple 40mm flare radius would have made the front much larger.



Tuning was more or less a blind shot. The vents were removable and I tryed 3 different lenghts before they and the back panel were glued. As I ran out of time, I measured just some short sweeps in REW, trying to tell the tuning frequency from the SPL and phase graph and then cut some cm off the vent pipe

Tuning should be somewhere at 38 Hz now, but that's just what I can tell from the Rew measurements.



I put more than 90 hours into the design, but therefore it is an enjoyment to put all the parts together and see how perfectly all of it fits.

I havn't really tested them to their limit, they are way to overpowered as monitor subwoofer, but I'm looking forward to hear and measure what they are capable of.



https://www.dropbox.com/sh/frit8jmum8ptds3/AADfJ97ODnKO5Y4Gz1iBtawva?dl=0
 

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Looks very impressive, would love to see the measurements too if you're willing to share them.

If you have a bit more time, you can measure the impedance using REW to get a more definite idea of the final tuning frequency.

Regards,
David.
 
Nice work. It is difficult to determine the interior port profile from the photos, so apologies in advance if you have already done this! The port should have similar flaring on the inside to make the airflow as symmetrical as possible - it is not a horn - otherwise it is distinctly non-linear, introducing harmonic distortion and port rectification which will push the cone away from its rest position on long bass notes, reducing the available Xmax.
 
I will post measurements as soon as i have time to make some. The ones I did to test tuning frequency were really dirty (no fix mesaurement distances and even bader, a back panel that was hold together with clamps, as I had to be able to remove the pipes through it to make them shorter).
Actually, I always made a ~2m ground plane measurement and another one at the outlet of the port. With the second one it was pretty easy to determine a tuning frequency, although I have no idea how close this one comes to an impedance measurement.
Honestly, I don´t even know why it´s important to know the exact tuning, or how I can find the optimum, but the measurements showed some dB more around 40Hz with the shorter port, still there was enough low end in the listening test.
The great thing is that the ports are so big, that it should be ok to close one of them for small gigs or a home theatre show at home, tuning drops down to ~25Hz with one port closed.

I only watched a short video about the impedance measurement in REW, and already lost the link, so if someone has an advice for me, how to do this properly, I will try it during the next testing.


Carl you don´t need to worry, the vent back flare was planned to be removable too, it was just the last part that was cnc machined and not ready when I made the pics :)



Some facts about the cab:
The "main" front is 30mm, plus 15mm added under the driver cutout to have enough depth for the 40mm Flare, and another 15mm at the backside of the front, as reinforcement for the driver (30mm-20mm would have left just 10mm for screws) and as pipe-holder. (this one was meant to be 12mm, I just didn´t think about it and used 15mm instead).
So at the thickest part, the finished front is 60mm or 2,36" thick, yet it wasn´t that heavy, obiusely because the front is mainly just three holes rather than remained material.
All the other parts were made of 15mm MPX, but as you can see, i didn´t skimp on brazings, so the cab should still be pretty stiff....
I hadn´t time to put it on a scale yet, and this one isn´t a lightweight for sure, but at least, a single person is able to lift it up and put it on a wheel board.
Outer dimensions are 43x58x65,5cm so ~164L.

1631613472171.png1631614035354.png
 
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This thing is nuts.

It's got all of the industrial engineering I'd want to do but don't have the time or money for, and even I wouldn't have bothered with that level of port flare. (or is it flair? ;) )

You probably need to fill the voids in the corners though. I know Peter Morris has used plumbers foam on the Mid-Hi.

Oh, and as far as a wheelboard goes, I would personally just bolt casters on the back of the cabinet. If you use Tee-Nuts and thread locking compound they stay pretty affixed for quite some time.
 
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I already thought that the voids in the corners may create unnecessary resonances or sthg similar.
Maybe I will fill them up before painting, as you suggested.

About the wheelboards- I somehow have a problem with wheels directly mounted on subs...
I think this is one of the few points- if not the only one, where I disregard the rule of design follows function.
Seems as I have to learn the hard way, how usefull those are, during a setup preperation haha
 
Moritz Bachmann said:
Honestly, I don´t even know why it´s important to know the exact tuning, or how I can find the optimum

I only watched a short video about the impedance measurement in REW, and already lost the link, so if someone has an advice for me, how to do this properly, I will try it during the next testing.
Click to expand...
Hi,
Knowing the tuning is useful as you will need to have a High Pass Filter set to prevent over-excursion from causing increased distortion and potentially damaging your driver when you use it at louder volumes, eg for gigs. This filter needs to be set a few Hz lower than the tuning frequency as that is where the cabinet "unloads", ie it stops helping control the cone's movement.

I believe there is a guide to impedance measurement in the REW manual so it should be accessible any time.

HTH,
David
 
that makes sense, to be on the save side, I set the HPF at 35Hz, which should be 3- max. 5Hz under tuning frequency.
I will read the manual, but I don't think I will have time this or even next weekend, so the new measurements have to wait a little
 
I'll give some sage advice, hard fought through the years, regarding the use of HPF for protection:

All the big boy companies seem to push the margins more and abuse a 4th order HPF to control the excursion, but a 3rd order filter seems to more naturally control the roll off, in my experience. Give it a try; see if you like.
 
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