Subwoofer project using a 12" Peerless 835017 (or better)

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#21
Lol not an engineer, but I'm technically minded and have done a lot of reading on this in the last week.. 🙂

I've read your response over and over but I'm still a bit confused at what your saying here. Sorry if I'm missing something. 🙁

Are you basically saying that I shouldn't be concerned about port velocities etc and it will be fine with a 4" port?

Again I'm sorry if I've missed the point. 😕

Thanks.
 
#22
In theory, a ~115 L/22 Hz Fb alignment @ the ~175 W X-max limit @ ~ 32 Hz requires a 5" dia. vent. [min.] to get a 'close enough' 5% vent mach and dual 4" to get below it.

Flared vents help at the expense of needing to be longer, though won't lower it as much or need to be as long as a 5" dia.. Not many 'free lunches' in audio design.

GM
 
#23
shmb said:
Lol not an engineer, but I'm technically minded and have done a lot of reading on this in the last week.. 🙂

I've read your response over and over but I'm still a bit confused at what your saying here. Sorry if I'm missing something. 🙁

Are you basically saying that I shouldn't be concerned about port velocities etc and it will be fine with a 4" port?

Again I'm sorry if I've missed the point. 😕

Thanks.
Click to expand...
I guess that's what I'm saying. Taking what you said in consideration, you want to use a 4" port, nothing against if you don't use the max. output all the time. If you go to WinISD you can compare the level of power require (max. W) for the limit of the threshold, are you using it? how much is it giving instead of asking me again... :Pumpkin:
 
#24
Inductor said:
I guess that's what I'm saying. Taking what you said in consideration, you want to use a 4" port, nothing against if you don't use the max. output all the time. If you go to WinISD you can compare the level of power require (max. W) for the limit of the threshold, are you using it? how much is it giving instead of asking me again... :Pumpkin:
Click to expand...

GM confirms pretty much what I thought too by my simulations. (a 4.5 inch minimum dia port in theory) Thanks 🙂

Regarding WinISD, I have been playing around with the figures, but this is the first project I'm using it for, so I'm learning.
In my simulations the cone excursion is still controlled (at least above the tuning frequency) at 175w and the maximum port velocity at that same power level is 30m/s with a 4" port, 19m/s with 5" port and 13m/s with a 6" port.
The length of the 5" and 6" ports however are impractical anyway.

I've decided to get the 4" precision port from P/E and try that.
As mentioned, in practice it will probably be enough.
If not, I can always enlarge the hole later. 😀

Again thanks for all the help 🙂
 
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#25
175W max. and can't you use less, that's my question, dig it?!
What's the speed if you use 150W... or 145W (or less)?
You have about (@1.00 m and max. power) 113.5 dB.
So if you use less power, for 19.5 m/s max. speed of air and with your 4" port, how much is the power used? (edit)
 
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#27
#32
Hi,

Just an :2c: observation:


From Post # 26:

Ok, @ 75 watts input I get 19.5m/s with the 4" port.
Click to expand...


No,19.5 m/s is not correct for an 115 l Box, At 75W(Rms):

The Port velocity will reach 46 m/s and xmax limited to 17.4 Hz.

Max input Power is ~32W(Rms) for not to exceed a Rec. Max Velocity = 10 m/s) when tuning at ~22Hz and when the box is minimally stuffed, i.e. using a stuffing density of 0.2 lb/ft^3 and a total weight of <=0.31 kg.

Data collected using MJK program: f -3dB= 21 Hz; A ~ 2dB broad-band Peak occurs at 35Hz and at 2xPI (Sr) the dB-SPL is about 106/ 75W/4Ohm.

b🙂
 
#33
Ok, maybe so. Thanks. 🙂

In any case, now they are built and finished with the 4" precision port and all working and with the limited power I can drive them with so far until I get the correct amplifier(s) I'm happy with the sound.

Very happy in fact. 😀

Just looking for some more suggestions from peoples experience as to what amp.

Thanks.
 
#34
...No,19.5 m/s is not correct for an 115 l Box, At 75W(Rms):...The Port velocity will reach 46 m/s and xmax limited to 17.4 Hz.

Max input Power is ~32W(Rms) for not to exceed a Rec. Max Velocity = 10 m/s) when tuning at ~22Hz and when the box is minimally stuffed, i.e. using a stuffing density of 0.2 lb/ft^3 and a total weight of <=0.31 kg.

Data collected using MJK program: f -3dB= 21 Hz; A ~ 2dB broad-band Peak occurs at 35Hz and at 2xPI (Sr) the dB-SPL is about 106/ 75W/4Ohm.
Click to expand...

Hi, My :2c: Posted Air 🙁 Velocity =46 m/sec is totally wrong...~19.5 m/sec is correct and worth at least: :2c: :2c: :2c: :2c: :2c: = 10 cent or even more 😀

b🙂
 

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#39
Inductor said:
That dimpled 4" flared port a la B&W looks great (and is needed here), heh-heh?!
Driver is not installed in the middle of the baffle, is it? It looks like from this perspective.
It looks great overall. Kudos. 🙂
Click to expand...

Thanks 🙂

It does look like it from the photo, but its about 2.5cm offset towards the top.

FB is currently 21Hz with no insulation inside.
 
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