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My DIY 4 way speaker system


Bokke
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Is this speaker intended for music only? Just thinking this may impact how low in frequency may be genuinely useful. My sub gives me bass extension into single digit frequencies but for music I doubt anything below 20 Hz is really useful, and that's a stretch. 30 Hz content is not that unusual though, so I'd definitely target decent output to go below this.

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From the plans posted earlier it looks like a 12" bass driver may have been what was being considered? If so then the BK Monolith subwoofer may be an interesting reference point to consider in terms of size and port tuning:

http://www.bkelec.com/HiFi/Sub_Woofers/monolith-FF_Plus.htm

I have one of the older model of these (with a 300 W rather than 500 W amp) waiting for me to get round to selling it but in my modestly sized room (about 4.6 m x 3.4 m x 2.3 m) one of these had plenty out output for my music needs. It's only for movies where the extra output of my current sub is utilised. There is also a difference in the sound between the ported and sealed designs, possibly just down to a difference in Q but I'm not sure.

I'm just posting this as there is always going to be a tendancy to just assume bigger = better but it's more complex than that. Both in terms of what may be useful and what can be achived (my PSA sub is smaller but more capable than my BK Monolith).

Edited by MartinC
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Super Wammer

My approach was if I could get a reasonable response below 20hz then any low ‘std’ music notes in the 20-30Hz region would definitely be heard.

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1 hour ago, MartinC said:

Is this speaker intended for music only? Just thinking this may impact how low in frequency may be genuinely useful. My sub gives me bass extension into single digit frequencies but for music I doubt anything below 20 Hz is really useful, and that's a stretch. 30 Hz content is not that unusual though, so I'd definitely target decent output to go below this.

music and movies but my target is 20 - 25 hz without losing power if possible 

the bass driver is 15 inch volt radial, similar to @MF 1000 18 inch version.

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30 minutes ago, MartinC said:

Here's an old photo for reference (PSA S1510 on the left and BK Monolith on the right).

873197619_S1510andMonolith_small.jpg.0f83f997a928d9bf6d72a5aadc308632.jpg

totally see where you coming from as I've owned the 500w monolith and during movies it shakes the house

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so last night I went to bed a little confused about the port sizes so Im going to start again with a fresh head.

@MF 1000   @cooky1257  @MartinC

so from what I've read in the comments about the port size:

(lets presume that all port size are 100mm in diameter)

using just one 100mm port gets you a lower frequency in hz than using 2 or 3 100mm ports? (we not getting into length yet)

 once I'm certain on this i can move forward.

regards all

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the reason I'm not worried about port length is that i can add or subtract at any time but the port number and port size is crucial to the front baffle and the spraying and prep to get it looking perfect is very labor intensive 

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Super Wammer

It’s the combination of port dia & length fir any given cabinet volume that enables you to tune the cabinet to hopefully produce a lower Hz than the ‘naked’ driver …the Fs in my case the 18” driver has an Fs of 26Hz and my cabinet/port combo gives 12Hz 😍😍

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Super Wammer

….but smaller bore ports have that inherent risk of too much air velocity and cause a chuffing noise when lots of air are moved by a big driver esp in a smaller cabinet 

big cabinet and large bore ports eliminate this but the trade off of longer ports esp if you use multiple ones

a 100 mm port has 31sq cm of area so as you add more this adds 31per port so the corresponding length of each port increases to keep each one tuned to the selected frequency 

Edited by MF 1000
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Super Wammer
What is end correction factor?
 
 
In short, end correction is the short distance that you add to the end of a resonance pipe in order to figure out its resonant frequency. In other words, it is is a measurement of standing waves. ... In subwoofer box calculations, we assumed an end correction factor of 0.732.
 
Which gave me a single port length of 670mm in my 240 litre cabs …..fir 12 Hz tho 😍
Edited by MF 1000
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4 minutes ago, MF 1000 said:
What is end correction factor?
 
 
In short, end correction is the short distance that you add to the end of a resonance pipe in order to figure out its resonant frequency. In other words, it is is a measurement of standing waves. ... In subwoofer box calculations, we assumed an end correction factor of 0.732.
 
Which gave me a single port length of 670mm in my 240 litre cabs 

so as its a sub do i use this figure in my calculations also 0.732? 

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Super Wammer

Yes use 0.732

If you can accommodate two longer pipes to get a lower freq personally I’d go for it as the response at 25 Hz will be even better 

2 x100  at 670 would get you down to 18 Hz 

We need to arrange you listening to mine before you push the button on the cab build I think 

Edited by MF 1000
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2 minutes ago, MF 1000 said:

If you can accommodate two longer pipes to get a lower freq personally I’d go for it as the response at 25 Hz will be even better 

Please look at my calculations and tell me if they look correct (just so I'm confident I'm using the calculation correct)

IMG-20211030-WA0002.thumb.jpeg.af44b0439e90b8e70f5590ba75cd7a0c.jpeg

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