Hi all! I was asked to create this topic as one of the authors of the acoustic design of subwoofers, which was called PPD (Petrenko Petrushevsky's Dipole). In fact, this design, in our opinion, is an improved version of the traditional ripole by Axel Ridtahler. Its main advantage compared to the Axel rippole is the absence of significant unevenness in the frequency response in the region of 150-300 Hz. Additional benefits are lower overall distortion in the subwoofer's operating range and smaller dimensions. With the right choice of TSP speaker parameters, very good results can be obtained, since the smooth frequency response allows the use of second-order filters.
In this video, an example of using a PPD subwoofer on a 15-inch speaker in triphonics.
In this video, an example of using a PPD subwoofer on a 15-inch speaker in triphonics.
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What drivers will work in the design I have currently Beyma 12BR70 4 drivers. Can you share the dimentions so I can try
Thanks for the inputs How do you find the bass quality compared to a sealed or ripole design. Does it work for a medium room or we need 4 drivers. to get pressure
Restored the message.
I have two subwoofers on the Beyma 12BR70.
The area of the front hole is 1/4 Sd, the area of the rear hole is 1/2 Sd. The volume of the front and rear cameras is minimal. The area of the back hole is 1/2 Sd, not including the area of the magnet
Example: Sd = 540 cm2, D magnet = 13.4 cm, S magnet = 140 cm2, S = 0,5 * 540 + 140 = 410 cm2, D holes = 22.8 cm
The hole in the front is 128 mm. The hole at the back is 224 mm. The size of my subwoofers is 386x386x140 m. You can do a little less. Initially, I did it for larger speakers.
My subwoofers have a magnet that protrudes 2 cm.
I have a cutoff frequency of 85 Hz. The LJM L12-2 amplifier, DSP processor DBX 260.
I like PPD bass better.
The room area is 19 m2. I have two subwoofers - the pressure is enough. Make two, if that's not enough, make four. It is better to power them through a Class D amplifier.
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The view is unpresentable, this is a layout. In the last photo there are inserts to reduce the volume of the rear camera.
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Nice, so pattern is more like cardioidish than dipole as Sd is different for front and back? Any measurements?
Would it work withtout the box so full Sd behind, and 1/2 Sd hole on a baffle for the front?
Would it work withtout the box so full Sd behind, and 1/2 Sd hole on a baffle for the front?
tu100 Thanks for your help with the answers. I will add that suitable speakers should have Bl as large as possible and Mms as small as possible. In terms of bass quality, I also prefer PPD as the most accurate, deep and fast.
Below are the PPD measurements for a 12-inch GW212_4 speaker: in the first graph, filtered and unfiltered measurements from 20 cm from the port. Below is a omnidirectional pattern in two different display modes.
PPD will of course work without a box with full Sd behind, and 1/2 Sd hole on a baffle for the front as you described, but I'm afraid that the quality of its' work will noticeably deteriorate in this case.
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@Sub Sonic
Beyma and Peerless/Tymphany 830669 are very similar in terms of TSP, so you can expect about the same result and it should be good. The only thing I would recommend to get acceptable pressure for home conditions is to make at least two 12-inch PPD subwoofers.
They can be used both in phase (photo No. 1) and anti-phase connection (photo No. 2).
Beyma and Peerless/Tymphany 830669 are very similar in terms of TSP, so you can expect about the same result and it should be good. The only thing I would recommend to get acceptable pressure for home conditions is to make at least two 12-inch PPD subwoofers.
They can be used both in phase (photo No. 1) and anti-phase connection (photo No. 2).
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Thank you for the time you spent on these but you state that it's like a ripole so if the fs is low like 25hz then it should play down to 15 hz like the ripole but can your play her like up to 500 Hz or are they limited like the ripole going up only till 100 Hz
That's right, a PPD subwoofer can operate as low as a ripole. However, you then ask if a PPD subwoofer can reproduce the range of a midwoofer? The answer will be negative, because the mid-bass range puts forward completely different requirements for drivers and their acoustic design.
Right, T/S box loading only extends to a driver's upper mass corner (Fhm = 2xFs/Qts), so using the 212/4 = 2x35.8/1.2 = ~59.67 Hz and if you look at the 60 Hz line in the above response graph you see its response is beginning a 'nosedive', so acoustically you ideally need a horn at this point to extend it.
To play 25-500 Hz requires a 2x25/500 = 0.1 Qts that historically only a powerful field coil driver could get this low, though I imagine a Neo motor could be built at a significant development cost.
Hello to the inventors of the PDD.
Thank you very much for sharing your design!
What should the dimensions of the front chamber be?
I mean the distanz between the the front plate and the plate with the woofer.
As little as possible? I.e. just enough for free movement of the membran of the woofer or a specific volume depending on SD of the woofer?
Cheers, Niels
Thank you very much for sharing your design!
What should the dimensions of the front chamber be?
I mean the distanz between the the front plate and the plate with the woofer.
As little as possible? I.e. just enough for free movement of the membran of the woofer or a specific volume depending on SD of the woofer?
Cheers, Niels
Yes, you think right: as little as possible, I.e. just enough for free movement of the membran of the woofer!