Hello everybody
Last weekend I've finished my subwoofer.
Everything is pretty good - nice, clear and tide bass up to 40Hz.
Below that point I got huge boost, at least 10Db or maybe more around 30Hz.coming out from the ports - all the furniture into the room and windows start shaking
I've moved the box around the room. but nothing changed.
I've tried damping the ports with polyfill, but that has very minimal effect.
Driver Parameters
12'' carbon cone
DVC 8ohm in parallel 2x150W
Fs 18Hz
Vas 225l
Qts 0.19
Xmax 5.4mm
Sd 495cm^2
Enclosure
ported
Vd 62l
F3 29Hz
dual port effective diameter 100mm
length 37.5cm
1'' polyfill applied on the sides, top and bottom
Plate amplifier BK BSBP 275W/4ohm
IMO the enclosure size is OK, even is slightly bigger than manufacturer's recommendation of >50l , but the tuning frequency seems to be too high.
I intend to go to a ports extension, making them twice longer about 75- 80cm
I've played with WINlSD last night and I made a comparison between the two different setups.
Would you explain to me what the ''Port Gain'' diagram means, please? Why gain of -6Db makes such a big output?
Any suggestions?
Last weekend I've finished my subwoofer.
Everything is pretty good - nice, clear and tide bass up to 40Hz.
Below that point I got huge boost, at least 10Db or maybe more around 30Hz.coming out from the ports - all the furniture into the room and windows start shaking
I've moved the box around the room. but nothing changed.
I've tried damping the ports with polyfill, but that has very minimal effect.
Driver Parameters
12'' carbon cone
DVC 8ohm in parallel 2x150W
Fs 18Hz
Vas 225l
Qts 0.19
Xmax 5.4mm
Sd 495cm^2
Enclosure
ported
Vd 62l
F3 29Hz
dual port effective diameter 100mm
length 37.5cm
1'' polyfill applied on the sides, top and bottom
Plate amplifier BK BSBP 275W/4ohm
IMO the enclosure size is OK, even is slightly bigger than manufacturer's recommendation of >50l , but the tuning frequency seems to be too high.
I intend to go to a ports extension, making them twice longer about 75- 80cm
I've played with WINlSD last night and I made a comparison between the two different setups.
Would you explain to me what the ''Port Gain'' diagram means, please? Why gain of -6Db makes such a big output?
Any suggestions?
Attachments
I'm really sorry, but I have posted my thread in wrong sub-forum.
May I ask the moderators to move my thread in Subwoofer sub-forum please?
Thank you very much
May I ask the moderators to move my thread in Subwoofer sub-forum please?
Thank you very much
Done.
HI,
Your speaker sub was calculated with a nice alignment.
MONACOR: SPH-300CTC
MONACOR SPH-300CTC, VB = 62.0 L, FB = 29.0 Hz
Make sure of each port diameter ~7 cm
2x Ports total ~77/78.54 cm2 (dual port effective diameter 100mm, length 37.5cm)
V= 14.71 V and P= 54.2 W (4.0 Ohms@FB) for Xmax ± 5.40 mm, maybe you have to much distortion from a 275W power amp. Check at normal listening levels (<50W).
Your speaker sub was calculated with a nice alignment.
MONACOR: SPH-300CTC
MONACOR SPH-300CTC, VB = 62.0 L, FB = 29.0 Hz
Make sure of each port diameter ~7 cm
2x Ports total ~77/78.54 cm2 (dual port effective diameter 100mm, length 37.5cm)
V= 14.71 V and P= 54.2 W (4.0 Ohms@FB) for Xmax ± 5.40 mm, maybe you have to much distortion from a 275W power amp. Check at normal listening levels (<50W).
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Thank you Inductor
As you can see on the last photo I have used triangle ports with cathetus 88mm, which makes cross section of 77.44 cm².
For sure I'm not pushing the amplifier too hard - it works on 25 -30% of the maximum power (the knob position is between 10 and 11 o'clock).
I am wondering is it possible to have some room gain or some resonance on that frequency?
The room size is 7m/3.5m.
This weekend I'll try in another room
Regards Georgi
As you can see on the last photo I have used triangle ports with cathetus 88mm, which makes cross section of 77.44 cm².
For sure I'm not pushing the amplifier too hard - it works on 25 -30% of the maximum power (the knob position is between 10 and 11 o'clock).
I am wondering is it possible to have some room gain or some resonance on that frequency?
The room size is 7m/3.5m.
This weekend I'll try in another room
Regards Georgi
344/2/7 = ~24.57 Hz ergo 3.5 = ~49.15 Hz
Don't forget the ceiling/floor if parallel and any large openings or alcoves. Every parallel set of surfaces has 1/2 WL eigenmodes.
GM
Don't forget the ceiling/floor if parallel and any large openings or alcoves. Every parallel set of surfaces has 1/2 WL eigenmodes.
GM
Hornresp calculates a ~30 m/s vent mach in the ~23-35 Hz BW at 150 W and ~38 m/s at 250 W, high enough to be audible as you've noted, so with your amp's 275 W rating, bass transients can be making the woofer drain or even clipping it.
GM
GM
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Thank you GM
I suppose, the port air velocity is out of suspicion, as I'm getting the low end gain at any levels. Of course, at that levels it won't shake the room, but it still here.
Regards Georgi
I suppose, the port air velocity is out of suspicion, as I'm getting the low end gain at any levels. Of course, at that levels it won't shake the room, but it still here.
Regards Georgi
I just measured the room size and I realised I've been wrong, that the room is 7m long. The size is 6.2m, but there is a massive wardrobe on the opposite wall, so the actual size is 5.5m, which produces a standing wave of 31Hz.
344/2/5.5 =31.27Hz
The wardrobe probably increases the magnitude of that wave, so that's why I'm getting such a gain in that frequency.
Thank you GM for that formula!
344/2/5.5 =31.27Hz
The wardrobe probably increases the magnitude of that wave, so that's why I'm getting such a gain in that frequency.
Thank you GM for that formula!
You're welcome!
'out of suspicion'? How so? I mean just because the amp's volume control is set reasonably low doesn't mean bass transients aren't 'demanding' a lot more power plus vent distortion during these times [if any] will be adding high amplitude noise, comb filtering with the driver.
GM