In regards to the slot loaded baffles at Burning Amp this year, did anyone get the 411 on the design of his speakers with the slot on the bottom. Going by his article, the slot is 1/3 surface area of the woofer. My question is how important are the size of the side wings? Or how much do they contribute? Reason is, we are just working with materials we have so there are two 18x42" panels, two 10x36"panels, and two 48x7.5" pieces. The rough sketch is here, a smaller version of those burning amp speakers Papa had, but I am not sure what the wing size should be, or how important it is. Also, is tilting the baffle back simply a matter of changing the angle of the wings where they fasten to the baffle?
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I've tried a similar one, with 2 problems:
1. the deep slot forms a strong 1/4 W.L. resonance, deep notch filter is needed if you play it up to midbass.
2. the cone (and air load) moving up and down, causing strong vibration to the whole base, efforts on isolating that from floor and other part of the speaker would be needed.
I dropped that eventually.
1. the deep slot forms a strong 1/4 W.L. resonance, deep notch filter is needed if you play it up to midbass.
2. the cone (and air load) moving up and down, causing strong vibration to the whole base, efforts on isolating that from floor and other part of the speaker would be needed.
I dropped that eventually.
Let me say that I have not read the whole tread, but would like to share a few observations.
A friend of mine build a prototype SLOB with two 18", compression ratio approx 1:10.
We did notice that the quarter wave resonance in the slot was a big problem, showing a large response peak and also a impedance peak around 200 Hz.
There were two surprises: Fs of the driver was pressed down from 37 Hz (free-air) to 24 Hz in the SLOB. The other was that there was no gain in efficiency at distances above 1 meter. In the near-field we measured 9 dB difference between from and back, but at 1 meter there was no difference at all.
All in all we concluded that the SLOB's best feature is smaller size compared to a H- or U-baffle.
A friend of mine build a prototype SLOB with two 18", compression ratio approx 1:10.
We did notice that the quarter wave resonance in the slot was a big problem, showing a large response peak and also a impedance peak around 200 Hz.
There were two surprises: Fs of the driver was pressed down from 37 Hz (free-air) to 24 Hz in the SLOB. The other was that there was no gain in efficiency at distances above 1 meter. In the near-field we measured 9 dB difference between from and back, but at 1 meter there was no difference at all.
All in all we concluded that the SLOB's best feature is smaller size compared to a H- or U-baffle.
We did not compare with a H-baffle of the same size, but its interesting to hear that the efficiency of the SLOB is lower. Anyway, we concluded that - if size does not matter - a regular U-baffle would be better efficiency-wise, and the H-baffle possibly the best overall solution, because of the symmetric front/rear polar pattern.
We also saw that above the first dipole peak (around 150 Hz), the FR of the SLOB was total rubbish, as with all dipoles.
We also saw that above the first dipole peak (around 150 Hz), the FR of the SLOB was total rubbish, as with all dipoles.
Wow, 10% Sd slot is a severe compression in my experience. After some trial & error, eventually I took 40% of Sd for the slot area, bigger than 30% some which Nelson Pass suggested. 10% is a big surprise to me. (BTW, my 40% Sd slot reduces the fs from 27Hz to 16)
Smaller slot tends to suppress the upper half of frequency response, so, relatively the low end would be more pronounced. But there's also a sense of heavy-footed which seems independent to the EQ'ed repsonse. For this reason I didn't make them too small.
I can't put this in numbers, but it's there. Probably related to the driver and the room, I guess.
Smaller slot tends to suppress the upper half of frequency response, so, relatively the low end would be more pronounced. But there's also a sense of heavy-footed which seems independent to the EQ'ed repsonse. For this reason I didn't make them too small.
I can't put this in numbers, but it's there. Probably related to the driver and the room, I guess.
Maybe NP would shear measures and info about the new slot loaded open baffle? 
What is the ideal listening distance, is around 3 meter ok?
As far as i can see the fullrange is a Lowther PM6A and the woofer a Eminence DEFINIMAX 4015LF 15"?
And they are divided with a B5 active crossover? With slopes, fq and baffle step corrected at?
Correct mee if i am wrong
THX in advance
What is the ideal listening distance, is around 3 meter ok?
As far as i can see the fullrange is a Lowther PM6A and the woofer a Eminence DEFINIMAX 4015LF 15"?
And they are divided with a B5 active crossover? With slopes, fq and baffle step corrected at?
Correct mee if i am wrong
THX in advance
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I looked over the original article by NP linked on page 1 here. It is also about 30 dB down at 20 Hz without EQ.
Qts should be about 0.5. With the right parameter set one probably can get away with a simple low pass filter. Let's wait and see how the SLS-12 Ripole turns out.
Actually the Lowther was a special field coil driver that was xo at 160Hz @ 12dB and the bass driver was Eminence Definimax 4015LF xo @ 80dB also with a 12dB slope. I'm pretty sure there were some additional adjustments to make the Lowther sing and not shout. I loved the sound of the set up, clean and clear whether in the front row or in back. This one along with Linkwitz set up were the highlights of the day for me.
Despite all the meanings around dipol peak and uneven f.r. with open baffles NP use a standard method with several designs (after what i have read and some suggestions from NP on email). It is mentioned in the article, and it also works for me with my B5 and Fostex FE203En-S:
It's easier to use an active crossover when you want quick results. You just adjust the
crossover filters, measure, listen, and then repeat the process until you're happy. It did not
take me long to get good results because the mating of the woofer and tweeter were well
behaved. I used a 2 pole low pass filter for the bottom at 80 Hz and a 2 pole high pass filter
at 160 Hz, and because I am lucky the proper response was with both drivers in phase.
Some equalization was called for on both drivers. The woofer received a high Q high pass
filter at 20 Hz which removed subsonics and gave the response a 6 dB bump up at 20 Hz.
The Lowther enjoys 4 dB of step correction above 2 Khz or so to take down the overall top
end. If you are a little off-axis, you might decide that 2 dB is better.
crossover filters, measure, listen, and then repeat the process until you're happy. It did not
take me long to get good results because the mating of the woofer and tweeter were well
behaved. I used a 2 pole low pass filter for the bottom at 80 Hz and a 2 pole high pass filter
at 160 Hz, and because I am lucky the proper response was with both drivers in phase.
Some equalization was called for on both drivers. The woofer received a high Q high pass
filter at 20 Hz which removed subsonics and gave the response a 6 dB bump up at 20 Hz.
The Lowther enjoys 4 dB of step correction above 2 Khz or so to take down the overall top
end. If you are a little off-axis, you might decide that 2 dB is better.
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The actual step of the Lowthers in practice is -2dB. The -4 dB figure gives the
flattest response on axis.
Can you tell us anything helpful in regards to your bottom slot baffles you had this year at Burning Amp? I'm tempted to try these, but also considering h frames, mainly due to my lack of knowledge regarding the single woofer slot loading. I am tempted to use Eminence Beta 15 over the Alpha, and feel if that's the case, they will lend themselves better to the slot vs h frame, as my understanding is that the slot loading will raise q slightly. Is that correct? As well, what effect do the side "wings" have on the woofer, or do they just support the baffle face?
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