The sims so far have been at 20cm from mouth. I have run some at 10cm and they are very similar - maybe -1.5dB loss of bass. I would compromise and put at 15cm from front. At 10cm they just look funny - too close to the front and too visible. If you get me an ellipse width and height at 15cm from front I can model it for you. For now will show what it looks like at 10cm and you get a feel. It will be a few hrs befor I am in front of Akabak computer though. Isn't it getting a bit late over there and this is a "school night"? Just hassling you. The only time I have to build speakers is when all others are sleeping.
When I get back to the computer I will plug in the 6FE100's. Maybe there is something there - although you just can't beat pure displacement capacity when it comes to bass and two 8's are a lot bigger than a pair of 6's. But then again a pair of 91dB vs 88dB makes a difference too.
The model will keep you from getting buyers remorse on the SB23's.
When I get back to the computer I will plug in the 6FE100's. Maybe there is something there - although you just can't beat pure displacement capacity when it comes to bass and two 8's are a lot bigger than a pair of 6's. But then again a pair of 91dB vs 88dB makes a difference too.
The model will keep you from getting buyers remorse on the SB23's.
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We leave them Faitals but the model post 56 was that with 64 watt input to one driver Faital verse SBA, therefor if we add one more driver is +3dB then they inside 1/4 wave rule gets 3dB more, and when xrk971 add a BW2 HP in Akabak in area 60-80Hz they probably accept same 128 watt as he probably feed to SB23NRXS45-8 to hit that high spl. In datasheets 6FE100 have 2,5dB better sensitivity and 100w max thermal power, SB23NRXS45-8 have 60w max thermal power and 1,25mm more excursion but in that it only has a 8 liter high Q box verse 38 liter to hit Q 0,7 box a lot of watts can be feeded without hitting XMax.
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32mm dia holes with SB23
Ok, so I am eeking everything I can out of a smaller hole. Now at 32mm qnty 4 and I moved the port to 5cm from the horn mouth. The smaller port shifted the tuning up a bit so f3 is now 89Hz. Max SPL is a formidable 113.6dB. So basically I think this driver can work, and if you like small injection ports, 32mm isn't a bad size to stick 4 of on the wall of that pretty big WG.
Ok, now onto a sim with the 6FE100...
But before we go there I had a sneaking suspicion that the velocity from an 8in woofer going full bore through a couple of 32mm holes isn't going to cut it. And no it doesn't - velocity at xmax is a screeching 50+ m/s = a recipe for chuffing and wind noise. At 65mm dia it is a much more reasonable 13m/s. There are tradeoffs everywhere. Maybe we are just pushing this little guy too loud and need to stay below say 105dB or so? That way, you can use smaller drivers, smaller holes, etc...?
Here is injection port velocity at max SPL for 32mm dia holes:
Here is injection port velocity at max SPL for 65mm dia holes:
So.... if we widen to 40mm dia port hole AND ease off on the juice and go only up to 11 volts (heck my, little TPA3116D2 can do that) we get 106dB SPL and 14.7m/sec max velocity. On the top limit of wind noise.
The moral of the story is: If you want 113.6dB max SPL, you need monster port holes, if you can live with 106dB, the 40mm hole is quite doable. Although, to be fair, a curved arc slot may not look so bad to achieve same CSA as 65mm dia round hole which is obtrusive looking as heck.
Ok, so I am eeking everything I can out of a smaller hole. Now at 32mm qnty 4 and I moved the port to 5cm from the horn mouth. The smaller port shifted the tuning up a bit so f3 is now 89Hz. Max SPL is a formidable 113.6dB. So basically I think this driver can work, and if you like small injection ports, 32mm isn't a bad size to stick 4 of on the wall of that pretty big WG.
Ok, now onto a sim with the 6FE100...
But before we go there I had a sneaking suspicion that the velocity from an 8in woofer going full bore through a couple of 32mm holes isn't going to cut it. And no it doesn't - velocity at xmax is a screeching 50+ m/s = a recipe for chuffing and wind noise. At 65mm dia it is a much more reasonable 13m/s. There are tradeoffs everywhere. Maybe we are just pushing this little guy too loud and need to stay below say 105dB or so? That way, you can use smaller drivers, smaller holes, etc...?
Here is injection port velocity at max SPL for 32mm dia holes:
Here is injection port velocity at max SPL for 65mm dia holes:
So.... if we widen to 40mm dia port hole AND ease off on the juice and go only up to 11 volts (heck my, little TPA3116D2 can do that) we get 106dB SPL and 14.7m/sec max velocity. On the top limit of wind noise.
The moral of the story is: If you want 113.6dB max SPL, you need monster port holes, if you can live with 106dB, the 40mm hole is quite doable. Although, to be fair, a curved arc slot may not look so bad to achieve same CSA as 65mm dia round hole which is obtrusive looking as heck.
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Must say 8FE200 have nice sensitivity data in 95dB, 6FE200 is also 95dB but could not reach low end target roll off.
For all three 8FE200 examples either 2 x38mm diameter ports or 1 x 52mm should do job with the 1mm frustum lip, and spl is for one driver only so add 6dB for dual drivers inside 1/4 wave rule.
Picture 1:
64 watt input sealed Q 0,7 f3 89,78Hz verse band pass with same high volume Q 0,7 52,43 liters back box, 0,165 liter front box with 1000Hz resonance. Comments is impedance resonance is close to our target roll off slope but we live what such for subs and XMax limit lacks so lets look a smaller back box volume than 52,43 liter.
Picture 2:
Same as above but with 8 liter back box it gives overshoot going from 52 to 8 liters volume but low end reach seems lost.
Picture 3:
In that excursion went down with 8 liter back box volume then if feed 128 watt and we see only one driver is close to 114dB in band pass there should be room to EQ overshoot and roll off to a textbook BW2 in 80-90Hz area.
Regarding port diameter like the the smaller footprint for 6FE100 two times 23mm diameter injection ports per driver or with one port 32mm diameter per driver.
4FE35 in picture or 4FE32 looks good as rear mount driver will check later with 4 times those 91dB sensitivity drivers 4FE35 or 4FE32 they both available in 4/8/16 so six configs to check if they can hit low end reach and have advantage in lower diameter for injection port.
For all three 8FE200 examples either 2 x38mm diameter ports or 1 x 52mm should do job with the 1mm frustum lip, and spl is for one driver only so add 6dB for dual drivers inside 1/4 wave rule.
Picture 1:
64 watt input sealed Q 0,7 f3 89,78Hz verse band pass with same high volume Q 0,7 52,43 liters back box, 0,165 liter front box with 1000Hz resonance. Comments is impedance resonance is close to our target roll off slope but we live what such for subs and XMax limit lacks so lets look a smaller back box volume than 52,43 liter.
Picture 2:
Same as above but with 8 liter back box it gives overshoot going from 52 to 8 liters volume but low end reach seems lost.
Picture 3:
In that excursion went down with 8 liter back box volume then if feed 128 watt and we see only one driver is close to 114dB in band pass there should be room to EQ overshoot and roll off to a textbook BW2 in 80-90Hz area.
Regarding port diameter like the the smaller footprint for 6FE100 two times 23mm diameter injection ports per driver or with one port 32mm diameter per driver.
4FE35 in picture or 4FE32 looks good as rear mount driver will check later with 4 times those 91dB sensitivity drivers 4FE35 or 4FE32 they both available in 4/8/16 so six configs to check if they can hit low end reach and have advantage in lower diameter for injection port.
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6FE100 doesn't go low
I just can't get it to work - the T/S parameters apparently don't want a flat bass shelf to 100Hz.
To get the following requires a 40mm dia hole x 4 and the velocity is still too high in the 20+ m/s.
I think the two SB23's are the way to go.
I just can't get it to work - the T/S parameters apparently don't want a flat bass shelf to 100Hz.
To get the following requires a 40mm dia hole x 4 and the velocity is still too high in the 20+ m/s.
I think the two SB23's are the way to go.
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SB23NRXS45-8 seems the way to go for many reasons but see below if there is anything about that is reason why your sim for 6FE100 and 8FE200 don't show lower reach.
SB23's have more overshoot than 6FE100 when forced into low volume 8 liter and that overshoot you probably softened with electric high pass filter point set relative high or a EQ notch, so a guess because you can't get 6FE100 to go lower is because in script you use same electric high pass filter as for SB23's, 6FE100 is a 80Hz f3 in Q 0,7 box so set electric high pass filter a little lower or turn it off to see 6FE100 can reach lower. Think a BW2 electric high pass filter close to 80Hz for 6FE100 would throw a close to acoustic LR4 80 Hz that is -6dB down at XO point.
SB23's have more overshoot than 6FE100 when forced into low volume 8 liter and that overshoot you probably softened with electric high pass filter point set relative high or a EQ notch, so a guess because you can't get 6FE100 to go lower is because in script you use same electric high pass filter as for SB23's, 6FE100 is a 80Hz f3 in Q 0,7 box so set electric high pass filter a little lower or turn it off to see 6FE100 can reach lower. Think a BW2 electric high pass filter close to 80Hz for 6FE100 would throw a close to acoustic LR4 80 Hz that is -6dB down at XO point.
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I even tried turning off the high pass filter completely and did not work - see below. Making rear chamber volume larger did not do it either. I think it is the stiff suspension and higher fs "pro tuning" that prevents the cone from moving deep to go low.
Although, we could just de-rate max SPL level to say 107dB and then EQ level everything flat towards that target and then it would be able to reach 80Hz f3.
Although, we could just de-rate max SPL level to say 107dB and then EQ level everything flat towards that target and then it would be able to reach 80Hz f3.
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Weird when seen in light of for SB12NRX25-8 our sims were in agreement, then i only see reason one of us have wrong T/S parameters set for 6FE100 or accidently choose closely named 6FE200, but let it be SB23NRXS45-8 will do the job nicely and when lowered in system spl their 60 watt thermal power specs is not pressed.
I love this guys!
I go to bed, wake up and you have done amazing work!
So, conclusions:
1. keep SBA 8 inchers.
2. Ports closer to front much better from diffraction viewpoint and minimal effect on tuning.
3. Port size a real compromise between SPL, mechanical port noise, and diffraction effects- likely the Goldilocks's port to be chosen- not too big, not too small!
Ok, after work I will start cutting some white paper port outlines and take some photos on the horn so we can see what looks best.
Thanks again.
I go to bed, wake up and you have done amazing work!
So, conclusions:
1. keep SBA 8 inchers.
2. Ports closer to front much better from diffraction viewpoint and minimal effect on tuning.
3. Port size a real compromise between SPL, mechanical port noise, and diffraction effects- likely the Goldilocks's port to be chosen- not too big, not too small!
Ok, after work I will start cutting some white paper port outlines and take some photos on the horn so we can see what looks best.
Thanks again.
I think this is going to work well with the dual 8 inch woofers.
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And for reference, sensitivity at 2.83v is about 93dB:
Same sensitivity could get from normal WHW, with dual 8" and a horn in the center.
Easier ?
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Oh yes, for sure the same sensitivity and easier but look at how much bigger the frontal baffle area would be to accommodate that. Most importantly though, the bass injection through the horn walls provides a virtual point source and beam width variation effects through XO frequency are not an issue. One could argue that with a 500Hz XO frequency these effects are already minimized and indeed we use them to advantage in traditional dual driver FAST speakers. It is hoped that with a virtual point source integration no noticeable multipoint XO effects will be noticeable - especially in near field minitor work.