I haven't tried them full power, but blended them to match the level of my main speakers and then played the whole system at various levels with all types of music.
The main difference between the U-frame and the Ri-pole is that the Ri-pole has a much lower efficiency, with the 27mH/282uF passive low-pass I had on the U-frame connected to the Ri-pole, it was as if the sub wasn't working, I had to change the passive network to 18mH/182uF to get the feeling of enough bass. Therefore there was relativly less sub-bass energy which made it sound less well balanced than the U-frame. So I decided it was time for active filtering and correction.
Compared to the non-corrected version I noticed that the more I had to boost in the 20-30Hz range the more "boxiness" grew with the sound. Listening and feeling the air directly in front of the openings, I noticed that there is a sort of pressure front radiating, similar to when a reflex prot is working hard, but then much larger. With the U-frame I didn't notice this effect, and bass seemed to be more "just there" instead of having a "forced" nature about it. I must admit that I yet have to make an active U-frame set-up, hopefully I will have time this weekend to try that out.
Absolutly speaking, bass is still very impressive with plenty of weight and power, it makes a small 10" closed box sub that I had for a while sound embarrassing. But I still prefer a U-frame for being so totally free of colouration.
The main difference between the U-frame and the Ri-pole is that the Ri-pole has a much lower efficiency, with the 27mH/282uF passive low-pass I had on the U-frame connected to the Ri-pole, it was as if the sub wasn't working, I had to change the passive network to 18mH/182uF to get the feeling of enough bass. Therefore there was relativly less sub-bass energy which made it sound less well balanced than the U-frame. So I decided it was time for active filtering and correction.
Compared to the non-corrected version I noticed that the more I had to boost in the 20-30Hz range the more "boxiness" grew with the sound. Listening and feeling the air directly in front of the openings, I noticed that there is a sort of pressure front radiating, similar to when a reflex prot is working hard, but then much larger. With the U-frame I didn't notice this effect, and bass seemed to be more "just there" instead of having a "forced" nature about it. I must admit that I yet have to make an active U-frame set-up, hopefully I will have time this weekend to try that out.
Absolutly speaking, bass is still very impressive with plenty of weight and power, it makes a small 10" closed box sub that I had for a while sound embarrassing. But I still prefer a U-frame for being so totally free of colouration.
U frame vs W frame
The W frame dipole woofer you developed, as you point out, is a ripole which is designed to lower Fs of the drivers by intentionally making the box openings smaller (which also tends to increase Qts). This would also lower the resonant frequency (of the box) that you see in your frequency plot and could lead to a more boxy sound.
A conventional W-shaped dipole woofer would have larger openings (could be much larger) and is less likely to have the boxy colorations you noticed. It would also still have the motion cancellation effect which the U shaped dipole does not have.
I have both W frame dipole and U frame dipole subwoofers (the U frame is on the same baffle as my midrange and high frequency drivers, while the W frame is a separate subwoofer) and the problem I have with the U frame dipole is that it vibrates terribly. I believe that I can deal with that by doubling the thickness of the baffle (which is only 3/4 inch now) and adding some bracing. The W frame dipole is a self braced box which deals with vibrations inherently in its design through bracing and cancellation.
Retsel
The W frame dipole woofer you developed, as you point out, is a ripole which is designed to lower Fs of the drivers by intentionally making the box openings smaller (which also tends to increase Qts). This would also lower the resonant frequency (of the box) that you see in your frequency plot and could lead to a more boxy sound.
A conventional W-shaped dipole woofer would have larger openings (could be much larger) and is less likely to have the boxy colorations you noticed. It would also still have the motion cancellation effect which the U shaped dipole does not have.
I have both W frame dipole and U frame dipole subwoofers (the U frame is on the same baffle as my midrange and high frequency drivers, while the W frame is a separate subwoofer) and the problem I have with the U frame dipole is that it vibrates terribly. I believe that I can deal with that by doubling the thickness of the baffle (which is only 3/4 inch now) and adding some bracing. The W frame dipole is a self braced box which deals with vibrations inherently in its design through bracing and cancellation.
Retsel
Tony, thanks for sharing. It's always good to hear of others experiences. Have you considered trying a W frame dipole? Any idea what you will keep?
The U frame seems a fairly sensible balance to me, while it is large, its not as big as a W dipole.
Retsel I don't suppose you have had a chance to compare U vs W for a given driver?
I actually have a H frame which I'd like to try out properly, partly to test my subwoofer drivers, see what is the most accurate they can be, test push pull mounting, etc.
The U frame seems a fairly sensible balance to me, while it is large, its not as big as a W dipole.
Retsel I don't suppose you have had a chance to compare U vs W for a given driver?
I actually have a H frame which I'd like to try out properly, partly to test my subwoofer drivers, see what is the most accurate they can be, test push pull mounting, etc.
noah katz said:
Instead of adding mass to the driver you can increase the radiation resistance of the air in front (and back) of the driver. That´s exactly what a ripole does.
@Geenius, regarding the boxy sound of your ripole:
Could it be you are pushing physics too far?
As John Kreskovsky has pointed out, dipoles don´t work beyond certain limits set by room size:
http://www.musicanddesign.com/roomgain.html
Your 32 Hz node suggests that this is the lowest mode of your room. If that is true there is no sense in trying to go any lower. You will only maximise distortion (probably what you mean by "boxiness"), by fighting against the physical limitations of your room.
BTW: The inventor of the ripole prefers front openings that are 25-33 % area of the driver cone (double that for double drivers). Back openings are as small as the driver construction permits. It seems your ripoles are almost W-baffles in this regard.
paulspencer said:
They don't take advantage of room gain and even loose output compared to the level above lowest room mode.
But I better let John K. explain it in his own words:
"... the calculations ... show ... that the low frequency response of a dipole is limited by the fundamental frequency of the room in which it is operating. Applying equalisation to extend the response of the dipole will simply result in over taxing the driver .... Attempting to obtain extended low frequency response from a dipole in a smaller room is a fruitless endeavor."
According to John K. a cardioid woofer (like a u-frame) "will respond in a manner similar to that of a monopole with regard to room pressurization".
Rudolf said:
This is probably why boosting an octave lower had absolutly no effect on the overall output level, only made the woofers move more. I have found that it is possible with a closed box, I used to own a Velodyne DD-15 and could get it flat down to 15Hz.
What I also think contributed to the boxyness, or lack of extreme clarity in the bass, is that the W-frame of Ri-pole doesn't have direct rediating woofers. It's only my subjective idea but I believe there must be some truth in the idea.
.......and the beat goes on........
Next test was a closed box of 2x 45 liters placed back-to-back in a push-push configuration. The first graph shows the results without altering the settings I used from the Ri-pole sub. Obvious is the greater output around 20Hz, but also the lower ouput and octave higher.
The second graph shows the twin closed sub after optimum EQ-ing. Flat down to 17Hz +/-0,5dB The bass produced by this configuration has more weight to it, is warmer and is less boxy than the ri-pole but still doesn't have the clarity of the U-frame. Advantage is that the enclosure is the smallest so far. An interesting observation is that the cabinet is practically vibration free - must be something to do with the back-to-back firing woofers.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Next test was a closed box of 2x 45 liters placed back-to-back in a push-push configuration. The first graph shows the results without altering the settings I used from the Ri-pole sub. Obvious is the greater output around 20Hz, but also the lower ouput and octave higher.
The second graph shows the twin closed sub after optimum EQ-ing. Flat down to 17Hz +/-0,5dB
The bass produced by this configuration has more weight to it, is warmer and is less boxy than the ri-pole but still doesn't have the clarity of the U-frame. Advantage is that the enclosure is the smallest so far. An interesting observation is that the cabinet is practically vibration free - must be something to do with the back-to-back firing woofers.
Something tells me I've seen that amplifier before? See below url, spot the differences! But yes, I've noticed the same in the compound construction I've built recently, it is logical as both woofers move out of phase so there's no pressure build up inside the box. I however found it to sound 'boxy' nonetheless.
http://www.hardwareanalysis.com/content/image/11711/
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
http://www.hardwareanalysis.com/content/image/11711/
Best regards,
Sander Sassen
http://www.hardwareanalysis.com
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