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bass section - sub/kick

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i-z View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote i-z Quote  Post ReplyReply Direct Link To This Post Topic: bass section - sub/kick
    Posted: 11 August 2025 at 8:11am
Hello

First, to make things clearer: the plan is to build/upgrade our small soundsystem ("set of speakers" might be a better way to describe it) with a new bass section, reflex or sub/kick combo.
We use these for small parties (garden/garage/bar), i don't think we ever played them full power. We'd like a system capable of bass around 35khz.
I've got some equipment and experience in woodworking and know someone to assist with the electronic/connection stuff. So building it will be.

What we have:
-2 old JB systems "full-range" speakers PSX15 + amp (used those with a 18" reflex sub, no idea what design but is is wrecked...)
-2 x second hand P-audio C18-650el, one still sits in a functioning cab, the other cab is faling apart (mdf + moisture.....)
-behringer crossover 2310 super X pro

What we need:
-advice on enclosure design for the 18"ers
-amp to go with them :)

We hooked op the one c18-650-reflex to an friends amplifier and it sounds ok, but not great. I want to take it apart anyway because of the mdf, we want to be able to use it outside.

What we are in doubt about is:
should we build a reflex design (maybe a double?) or a sub/kick combo?
X1 + ES18?
Both go with the C18-650el, X1 maybe not 100% ideal but since we're probably not going to play it full power... Would the X1 be able to keep up with the ES18? I heard them before and they are pretty powerfull, maybe crossover a bit lower? 70?
or is the building teh combo just pure overkill....

Building reflex(es) is a lot easier, i know. But a seperate kick just sounds better (often...)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote i-z Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2025 at 8:15am
Forgot to mention: our music style is pretty wide... that's why we'd like to be able to  go a bit lower :)
mainly dj/electronic music, live band will be very rare
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Post Options Post Options   Thanks (0) Thanks(0)   Quote i-z Quote  Post ReplyReply Direct Link To This Post Posted: 11 August 2025 at 8:17am
Forgot to mention: our music style is pretty wide... that's why we'd like to be able to  go a bit lower :)
Mainly dj/electronic music, live band will be very rare
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Conanski Quote  Post ReplyReply Direct Link To This Post Posted: 12 August 2025 at 10:00pm
Reflex is the swiss army knife of speakers, a box tuned to mid-low 30's will be more compact and easier to move than just about anything else. The 650el will do a good job in a properly built rigid enclosure.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Jan-2T Quote  Post ReplyReply Direct Link To This Post Posted: 13 August 2025 at 9:09am
Music!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote i-z Quote  Post ReplyReply Direct Link To This Post Posted: 14 August 2025 at 8:59pm
Thanks,
Ok, i get it. The X1 looks realy nice but a reflex will probably fit our needs betterWink

Calculating the volume and so on is a bit too much for me... (more the woodworking type i gues). Something like the sub18, would that work?

I gues for now we'll build 1 reflex sub, and the see if we need/want a seperate kickbin

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Post Options Post Options   Thanks (1) Thanks(1)   Quote Jan-2T Quote  Post ReplyReply Direct Link To This Post Posted: 15 August 2025 at 10:57pm
Something like the SUB18 is an easy design to build, needs bracing however (not pictured on the plans)
I can try and sim your drivers in Winisd later this week, busy weekend: event tomorrow, hangover on sunday Tongue
or just go ahead and have a go at it, it's not so hard and it's free
The real box never* behaves as calculated in the simulation, will involve testing and adjusting the port length for the desired tuning.

Im sure you will reach x-max well before the power rating, maybe concider a 50 Hz tuned box so you can get more output.
Or settle for i guess low 30's to 40Hz tuned cab with -6dB or -3dB shelf, so this means reduced output to achieve a lower tuned box.

*not responsible for the one in a fillion** that behaves like simmed
**is made up so does not exist
Music!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote i-z Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2025 at 7:17am
Thanks!
Less output is not a big problem, i think they are a bit overkill for our needs anyways...
Realy want to go for a cab in the 30hz's

WinISD is difficult for me now (only have an old linux  laptop) so i tried some of the online calculators (getting into it Smile) on the sub18 type of design

So if get this right (newbie section right?):
-longer port means lower Hz
-speaker, port and bracing are subtracted from total inside volume (so longer port = less volume)
-if i make the port 45cm long and make the cab 5cm longer/deeper it'll go much lower? (or make it 60cm wide)

How much distance should remain between the port and the backpannel? I mean do you have to make the box deeper when you lengthen the port or is it just the total volume that counts?

Meantime i'm on the lookout for amplifier, right now what i am looking for is a bridgable amp with RMS a bit above my speaker's RMS. Good idea or not?


Edited by i-z - 16 August 2025 at 10:12am
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Post Options Post Options   Thanks (1) Thanks(1)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2025 at 12:56pm
Originally posted by i-z i-z wrote:

Thanks!
So if get this right (newbie section right?):
-longer port means lower Hz
-speaker, port and bracing are subtracted from total inside volume (so longer port = less volume)

Yes to both of these Thumbs Up.

Quote How much distance should remain between the port and the backpannel? I mean do you have to make the box deeper when you lengthen the port or is it just the total volume that counts?

Generally, you want at least one port-diameter clearance between the end of the port and the back wall. It's best to do this using the total port area, so for the B&C Sub18 that's 541 square cm. That converts to an equivalent diameter of 26.25cm, so that's your target clearance.

Now, the thing with tuning a box lower is that you lose performance due to a couple of factors, as Jan-2T was getting at.
Firstly, due to Hoffman's Iron Law, it gets less efficient.
Here's  a sim of (this old version of) the 18-650 in 173l tuned to 35, 32.5 and 30Hz. Even stepping the tuning down a few Hz at these frequencies can lose you nearly a dB of level each time:



However, on top of that, the lower tuning means the port is not helping control the driver's excursion as well in the middle of it's passband, so we end up having to de-rate the applied power to keep it sounding clean at high volumes.

Here's the excursion curves for the same 3 tunings. I've modelled the 35Hz option at 8mm excursion because P.Audio's 5mm figure was calculated using an older, more conservative approach and isn't as useful for comparing with other more modern drivers, but I don't have enough info to be sure if 8mm is exactly the best figure to use.
Both the lower tunings are driven at the same level.



If we de-rate the input to the lower tuned versions to stay within that 8mm of excursion then the lowest tuned version is now limited to just over 2dB less maximum SPL, if you want to keep the output clean:



So, all that being said, if this is the version of the driver you have (or indeed, for any other driver with limited Xmax), I'd stick with tuning no lower than 35-ish Hz, to avoid those penalties in level, unless you're super sure about never needing to push it that loud. FWIW, the de-rated input to the lowest tuned version in the above sims is being fed approx 380W so I wouldn't worry about bridging or finding particularly high powered amps if you do choose to tune low.

HTH,
David.


Edited by DMorison - 16 August 2025 at 12:57pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote i-z Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2025 at 1:51pm
Ok thanks a lot!

So i've been trying some things in the online calculator (micka.de)
If i make the cab a bit wider, 60 cm, which makes it easier to stack should we build a kick or something else (60 cm wide seems a common size)

with a 35cm port (+bracing and speaker) i'd have about 210L volume and these results:
half power frequency: 36.33 Hz
resonance frequency: 40.78 Hz
SPL: 95,42 dB
reference efficiency: 2.2%

About the amp:
so what you are saying is the amp's RMS doesn't need to be higher as the speaker's RMS? correct?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote levyte357- Quote  Post ReplyReply Direct Link To This Post Posted: 16 August 2025 at 5:36pm
Originally posted by i-z i-z wrote:

We'd like a system capable of bass around 35khz.

I assume you mean "sub starting at 35hz"

For newbies, the thought of messing with sim software, and re-inventig the wheel/designing a cab may seem exciting, but for those of us with limited budgets, and pass the exciting phase of "wasting money",
would strongly suggest you look on Facebook Rig Resale, for loaded used 2x18" Reflex cabs.

Originally posted by i-z i-z wrote:

-2 x second hand P-audio C18-650el, one still sits in a functioning cab, the other cab is faling apart (mdf + moisture.....)


Sounds like a perfect time to be done with the Paudio riff raff 18s.

There's a good chance you can grab a pair of B&C/Fane loaded 2x18" reflexes for peanuts.

If you don't have an LMS, or don't know how to use one, maybe best you stick with 2x18 reflex and your CX2310, and just get 2x12"+Compression driver (with Crossover)  Mid tops.

Run Sub - 35-100hz
Mid tops - 100hz up.

Get a QSC 5050 or QSC PL4.0  for sub, 
QSC PLX 3402 for Mid tops, and you'll be happy for years.

That setup will also earn you money in Pubs/House parties.



Edited by levyte357- - 16 August 2025 at 5:41pm
Global Depopulation - Alive and Killing.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote DMorison Quote  Post ReplyReply Direct Link To This Post Posted: 17 August 2025 at 10:28am
Originally posted by i-z i-z wrote:

Ok thanks a lot!

So i've been trying some things in the online calculator (micka.de)
If i make the cab a bit wider, 60 cm, which makes it easier to stack should we build a kick or something else (60 cm wide seems a common size)

with a 35cm port (+bracing and speaker) i'd have about 210L volume and these results:
half power frequency: 36.33 Hz
resonance frequency: 40.78 Hz
SPL: 95,42 dB
reference efficiency: 2.2%

OK, so you're using one of the more recent versions of the driver - there have been about 3 different ones using the same model number so as long as you're using the right parameters for whichever generation of driver you actually have you'll be fine - my models won't match yours exactly though.

Quote About the amp:
so what you are saying is the amp's RMS doesn't need to be higher as the speaker's RMS? correct?

Well, power handling is one area of speaker design that simply doesn't have a nice, easy, single number answer that will cover all applications, unfortunately.

I've pointed out that in these sims, the driver will reach a particular peak excursion at well below its continuous power rating.
In the real world, you may not be driving it with a signal that happens to include that frequency at maximum level - real world music usually has its content split up across several frequencies at once, depending on the type of music, specific arrangements within the music, specific tones of the instruments involved etc.
So in a lot of cases, many people would find that they could run this driver in that box with more then the 380W I mentioned, and not notice excessive distortion.

But, as I don't know what music you'd be playing through it, or how loud you might want to try and push it, or how clean you want to keep the sound, the best advice I can give is to point out the worst case scenario, which is that distortion is likely to increase once you're past that 380W in the 45-55Hz region.
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