Hello,
BR enclosure for P115S4 which price is at 35 euros and the best option I can buy at this price tag in my country. First attachment is subwoofer "Data Sheet".
Second one is 80L enclosure with 160 sq.cm port @ 33.9 Hz. I'm working with Hornresp for the first time with limited knowledge about subwoofers. I have a few questions about this build:
1. What kind of effect does electrical impedance have on my BR enclosure build and why there is one huge peak at around 50Hz. And what should I do about it?
2. What kind of effect does phase response have. As much as I understand it starts at my F3 (33.9Hz). And how a proper phase response should look like?
3. How group delay impact my enclosure and overall performance?
And I have some basic questions:
1. How to choose correct enclosure volume and port area? Maybe it has some kind of connection to speaker SD area?
2. How to know how long my port can be?
Hornresp:
1. Eg at default is 2.83 (1 watt into 8 ohms). If I choose Eg = 28.3 (100 watts into 8 ohms) does it mean I get simulation and acoustic power of my build at 100 wRMS?
BR enclosure for P115S4 which price is at 35 euros and the best option I can buy at this price tag in my country. First attachment is subwoofer "Data Sheet".
Second one is 80L enclosure with 160 sq.cm port @ 33.9 Hz. I'm working with Hornresp for the first time with limited knowledge about subwoofers. I have a few questions about this build:
1. What kind of effect does electrical impedance have on my BR enclosure build and why there is one huge peak at around 50Hz. And what should I do about it?
2. What kind of effect does phase response have. As much as I understand it starts at my F3 (33.9Hz). And how a proper phase response should look like?
3. How group delay impact my enclosure and overall performance?
And I have some basic questions:
1. How to choose correct enclosure volume and port area? Maybe it has some kind of connection to speaker SD area?
2. How to know how long my port can be?
Hornresp:
1. Eg at default is 2.83 (1 watt into 8 ohms). If I choose Eg = 28.3 (100 watts into 8 ohms) does it mean I get simulation and acoustic power of my build at 100 wRMS?
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I agree with what Perry said.
I see the impedance is directly correlated to the subwoofer cone movement spikes in those two ranges of frequency. The voice coil is moving further through the magnetic field. When impedance goes up, the amount of current pulled through your amp goes down. That’s not necessarily a bad thing.
Back when I used to build boxes for subs I was only concerned about three things. Electrical dampening, mechanical dampening, resonant frequency. I used a few algebra formulas to figure my box size and port size and everything else just took care of itself. Mind you, I never built competition systems, just something for some boom in the trunk or hatchback.
As far as port and box sizes. There are online calculators out there now so you don’t even have to know algebra to figure it out.
I feel sure that by studying the graphs and knowing what you’re trying to achieve, the answer may jump right out at you.
Wish I could be more help. Good luck with it.
David
I see the impedance is directly correlated to the subwoofer cone movement spikes in those two ranges of frequency. The voice coil is moving further through the magnetic field. When impedance goes up, the amount of current pulled through your amp goes down. That’s not necessarily a bad thing.
Back when I used to build boxes for subs I was only concerned about three things. Electrical dampening, mechanical dampening, resonant frequency. I used a few algebra formulas to figure my box size and port size and everything else just took care of itself. Mind you, I never built competition systems, just something for some boom in the trunk or hatchback.
As far as port and box sizes. There are online calculators out there now so you don’t even have to know algebra to figure it out.
I feel sure that by studying the graphs and knowing what you’re trying to achieve, the answer may jump right out at you.
Wish I could be more help. Good luck with it.
David
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1. Check out this:
Impedance chart, need explanation
2. / 3. Phase and group delay are the same data interpreted in different ways as long as your group delay is low enough it should not be noticeable. The noticeable group delay varies with frequency. 20mS at 20Hz is not noticeable.
1. Port area should be such that the particle velocity at maximum input voltage is below 17 m/S (some say 10 m/S it all depends on how much port compression is acceptable).
2. Enclosure volume can be traded off against port length but if they port is too long the upper frequency of the system will be limited:
Helmholtz resonance - Wikipedia
This is due to the pipe mode resonance of the port which goes lower in frequency the longer the port.
Impedance chart, need explanation
2. / 3. Phase and group delay are the same data interpreted in different ways as long as your group delay is low enough it should not be noticeable. The noticeable group delay varies with frequency. 20mS at 20Hz is not noticeable.
1. Port area should be such that the particle velocity at maximum input voltage is below 17 m/S (some say 10 m/S it all depends on how much port compression is acceptable).
2. Enclosure volume can be traded off against port length but if they port is too long the upper frequency of the system will be limited:
Helmholtz resonance - Wikipedia
This is due to the pipe mode resonance of the port which goes lower in frequency the longer the port.
Yes you are right. I have two of those. My trunk isn't big enough to go for more then 2x80 liters enclosures
Yes, BUT it will not show Xmax power limitation, so in theory should be done in the Acoustic Power/Tools/Maximum SPL window, BUT it doesn't take into consideration any room/cabin gain, so if planning on using high power, need to use it to factor in how much EQ cut will be needed where.
GM
Yes, the Qts is very high, they will not perform well in a BR cab. A bandpass isn't ideal either, it can easily become a 1-note subwoofer.
In a 80l sealed enclosure the Qt will be over 1,1 with the 4 Ohm version, the 8 Ohm version at 1,25. In only 80l they will sound boomy, muddy, very unprecise, any ported enclosure with that small volume will be even worse and will have a very long decay delay. Looking at 50Hz (BP) for a 15" does not sound tempting at all.
These subwoofers are made for open baffle, if you really want to put them in an enclosure, maybe try a TML, that could maybe work, nothing else will sound really good.
E: I wouldn't buy them, even for 35€.
In a 80l sealed enclosure the Qt will be over 1,1 with the 4 Ohm version, the 8 Ohm version at 1,25. In only 80l they will sound boomy, muddy, very unprecise, any ported enclosure with that small volume will be even worse and will have a very long decay delay. Looking at 50Hz (BP) for a 15" does not sound tempting at all.
These subwoofers are made for open baffle, if you really want to put them in an enclosure, maybe try a TML, that could maybe work, nothing else will sound really good.
E: I wouldn't buy them, even for 35€.
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Like I said, that won't result in any good sound. You could build an open baffle, they would work there great, maybe a TML. But you'd spend money on wood and postage, why throw good money at bad money? To my experience it's easier to sell the bare drivers instead of a complete box.
Yes, that's impressive looking but doesn't make much sense. Very low spl (on an OB you'll lose more) and very low power capabilities because of the small VC (just 51mm), it will not take the 200/400W, 250W peak at most. Maybe selling them as paperweights will be more successful.
From my point of view comparing BR (the one I provided) and BP4 enclosures I see only difference in upper frequency range. Lower frenquency range is almost the same. Can you elaborate benefits of BP4 when comparing it to BR?
The BP4 got 2 advantages compared to BR in this case: The spl is higher and the sealed back chamber prevents too high excursion below the tuning frequency, you can in many cases drop the low cut filter (which you can't at a BR sub).
The worse heat dissipation can be avoided by mounting the driver with the magnet to the ported chamber (which should always be done at BP4).
It got also disadvantages, it increases the group delay, the impulse answer and the decay a lot.
Thanks, that's valuable information! I did some sketch on Sketchup for BP4. They are in attachments. Dont have Layout for Sketchup so can't actually do proper measurements. Enclosure volume 82.8L (35L sealed, 47L Ported)
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