Hello,
I have 8 bc 8ndl51, I wonder if it would be possible to use them as a slot loaded open baffle from 60 to 400, 4 by side...
The idea is to create directivity.
I have a ripple subwoofer with 2 15" BMS and I love it, but the cavity resonance is quite low, 10*40*40 slot...
If you have any recommendation...
Thanks.
I have 8 bc 8ndl51, I wonder if it would be possible to use them as a slot loaded open baffle from 60 to 400, 4 by side...
The idea is to create directivity.
I have a ripple subwoofer with 2 15" BMS and I love it, but the cavity resonance is quite low, 10*40*40 slot...
If you have any recommendation...
Thanks.
Hi,
I like the B&C driver, I have never used it but it looks good on paper and I am a big fan of open baffle cabinets as the only cabinet better than a heavy bamboo plywood sealed box is no box!!
With open baffles, the limiting factors in low end driver performance is Fs and Xmax... As the driver gets close to its Fs you will start to see large cone movements which will not only result in blurred distorted bass, but the entire midrange will be ruined as the cone is pumping in and out near or exceeding X max trying to produce the bass.... But you should be fine as 4 drivers per side gives you a lot of "headroom".
I mention this as I always recommend using a good DSP / Eq active crossover to allow you to have linear phase steep slopes (48dB per octave ) to protect the low mid drivers from the bass frequencies.
This open baffle array will sound superb, but just for a comparison... I have attached a small sealed box (q = 0.6) sim of a 4 driver array using your B&C 8 inch . The drivers will remain ultra linear with low distortion and excellent sensitivity of 93.5 dB over the 65Hs to 400 Hz bandwidth, with 1 watt at 1 meter (wired for 8 Ohms).
Good luck!
A.
I like the B&C driver, I have never used it but it looks good on paper and I am a big fan of open baffle cabinets as the only cabinet better than a heavy bamboo plywood sealed box is no box!!
With open baffles, the limiting factors in low end driver performance is Fs and Xmax... As the driver gets close to its Fs you will start to see large cone movements which will not only result in blurred distorted bass, but the entire midrange will be ruined as the cone is pumping in and out near or exceeding X max trying to produce the bass.... But you should be fine as 4 drivers per side gives you a lot of "headroom".
I mention this as I always recommend using a good DSP / Eq active crossover to allow you to have linear phase steep slopes (48dB per octave ) to protect the low mid drivers from the bass frequencies.
This open baffle array will sound superb, but just for a comparison... I have attached a small sealed box (q = 0.6) sim of a 4 driver array using your B&C 8 inch . The drivers will remain ultra linear with low distortion and excellent sensitivity of 93.5 dB over the 65Hs to 400 Hz bandwidth, with 1 watt at 1 meter (wired for 8 Ohms).
Good luck!
A.
I just happened to have done ABEC sims of slot loaded dual opposed 8" woofers (8PR200) not too long ago. I made the slot 50mm high and just wide enough and deep enough to fit the driver. This was sealed however, not ripole.
.
There was a bandpass peak of about 8db at 300 Hz, which was very equalizable, Its easily usable beyond 400 Hz. I'm not sure how low you can go with 8NDL51s open baffle/ripole but it looks fine on the high end.
Here are some pictures from the sim
There was a bandpass peak of about 8db at 300 Hz, which was very equalizable, Its easily usable beyond 400 Hz. I'm not sure how low you can go with 8NDL51s open baffle/ripole but it looks fine on the high end.
Here are some pictures from the sim
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It’s important to recall that below 100hz, a closed space is completely modal…….OB works very well above 250hz and somewhat ok from 100-250…..but you have to work at it.
There’s no fundamental non resonant notes below 100hz…..those tones are all produced through resonant enclosures instead of membranes moving air and as such, direct radiation is only possible in the very near field. Below 100hz, play to the room whether it be an even excitation of room modes, extensive treatment to make the room disappear or a combination of both. OB sub bass isn’t advanced audio tech, it’s the biggest hammer you can find…….like a cavemen.
Hello,
I am very happy of the reactions here,
I think that the slot or every kind of dipole or ripple does not behave like a simple dipole, as written in pass article, the velocity of air in the slot is much higher than the one from behind.
I really like my ripple subwoofer for jazz and rock music as it excites the room less than a sealed woofer. If you go next room, you hear no bass at all...
Now here is my design, I measured with the back sealed with 16cm of high density rockwool and without. Without is terrible, but this is not the design we are talking about...
I was worried about directivity at 500hz but it is ok
I am very happy of the reactions here,
I think that the slot or every kind of dipole or ripple does not behave like a simple dipole, as written in pass article, the velocity of air in the slot is much higher than the one from behind.
I really like my ripple subwoofer for jazz and rock music as it excites the room less than a sealed woofer. If you go next room, you hear no bass at all...
Now here is my design, I measured with the back sealed with 16cm of high density rockwool and without. Without is terrible, but this is not the design we are talking about...
I was worried about directivity at 500hz but it is ok
Attachments
Thanks for your input, it is interesting,
I guess it is the same principle as Pass' project but with a sealed back not to loose too much energy.
I will buy scrap wood and start a funny prototype, I guess it is easy like a ripole, not like to one I made with 30 degree angle...
I like to seal the back with this high density rockwool, it helps avoiding sound box...
So the idea is to have a thin slot and do keep it not so deep to avoid noise and turbulence.
It could be fun if it worked because the design would be less wide than mine.
Maybe it would control directivity lower in frequency, mine behaves like a regular 15" driver...
Regards Greg
If you use two pairs with vertical slots, then the Vertical directivity will be determined by the spacing between the pairs and the Hdir will be determined by the width of the slot, and thus be very wide.
If you rotate so the slot is horizontal, then you get the Hdir of an 8" driver but you may have some sag due to gravity. You still get Vdir per the vertical spacing of the two pairs.
If you rotate so the slot is horizontal, then you get the Hdir of an 8" driver but you may have some sag due to gravity. You still get Vdir per the vertical spacing of the two pairs.
Ideally I am looking for 90 degrees of horizontal directivity to match the rest of the setup...
So do you suggest I shall have more width for the slot ? That makes sense
So do you suggest I shall have more width for the slot ? That makes sense
You can get that with two on the front plus two on the sides, inverted and delayed to create a active cardioid, DSP XO required.
You would also get directivity from the ripole, probably easier. That is something I don't have a ready simulation for so I can't be more specific.
You would also get directivity from the ripole, probably easier. That is something I don't have a ready simulation for so I can't be more specific.
Hello,
Yes I cannot go into the active cardioid, it is too much work and it is very difficult to measure at these frequencies. In my room I can gate measurements at 4 or 5ms at best.
And I am already doing active 3 ways with a subwoofer (Ripole).
I am experimenting cardioid for the mids though.
So what I could do is try the Nelson Pass design but with a folded front baffle as sides. A kind of Ripole. I don't know if he did not have the resonance or if he had eq-ed it. I don't know if this would be a problem as the resonance is maybe not evenly distributed in the pattern, this could ruin the all constant directivity project.
A cavity of 4 by 20 by 40 would apparently give a 220 hz resonance frequency, like in your simulation.
Or because he used is project below 150hz, he didn't really care... And we are not talking about the thermodynamics limitations of the port itself...
It is not a lot of work to try it though. Most of the wood can be bought from scrap wood at the diy store.
A different possibility would be to create a multi entry conical horn with 1 speaker on each side... a conical slot with one speaker on each side. I don't think we need to feed the horn through slots as we are not going to be restricted by space here.
Yes I cannot go into the active cardioid, it is too much work and it is very difficult to measure at these frequencies. In my room I can gate measurements at 4 or 5ms at best.
And I am already doing active 3 ways with a subwoofer (Ripole).
I am experimenting cardioid for the mids though.
So what I could do is try the Nelson Pass design but with a folded front baffle as sides. A kind of Ripole. I don't know if he did not have the resonance or if he had eq-ed it. I don't know if this would be a problem as the resonance is maybe not evenly distributed in the pattern, this could ruin the all constant directivity project.
A cavity of 4 by 20 by 40 would apparently give a 220 hz resonance frequency, like in your simulation.
Or because he used is project below 150hz, he didn't really care... And we are not talking about the thermodynamics limitations of the port itself...
It is not a lot of work to try it though. Most of the wood can be bought from scrap wood at the diy store.
A different possibility would be to create a multi entry conical horn with 1 speaker on each side... a conical slot with one speaker on each side. I don't think we need to feed the horn through slots as we are not going to be restricted by space here.
Attachments
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I did find an unfinished ripole simulation. I had abandoned it when the results were discouraging. I managed to clean it up and came to an understanding why ripoles are just used for subwoofers. In the slot loaded woofer, we get a bandpass peak that turns out to be equalizable and can use the woofer fairly high. If we open up the back wall of the slot loaded woofer to create ripole. We get that peaked response out the front but not the back so the dipole like response doesn't extend past the point where the response risess. You can see what happens in the graphs below. This sim is for a pair of 16OB350s. Even if scaled to 8", the response wouldn't be usable anywhere near asa high as you are aiming..
The
The
Yes Dave I have used over the weekend a longer spikes and tilted more than 7-9 degrees.
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