haha good dictatorship of course but you have to pick your battles
democracy doesn't work.. well at least not all the time, haha.I love that, SCM100 is about 160L, we can also go taller and have less depths if preffer taller ones but I like the ratio of SCM100 as it is
Forgot about TD15X need for larger cab but how come I get around 81 cm2 for port area ? 150L w fb of 24Hz w port d of 10 and length of 21cm (port velocity around 12 m/s) ?
either way we can go 160L or 170L for both 15FH520 or AE.
EDIT: maybe set a higher fb for AE driver :
15x in 160L fb=30Hz, f3 ~36Hz F6 ~30Hz.
15x in 160L fb=24Hz, f3 ~43Hz F6 ~31Hz .
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TW29DN-B and TW29RN-B are 4 ohms
. I heard good things about TW29BN-B (never heard one myself) but it's way too expensive
I was thinking that added resistance in the crossover from padding down the volume level to match the mid and woofer plus baffle step correction might bring the total impedance up high enough, but I guess that's a big maybe that might give us some unforeseen design constraints later.
What I'm hearing for additional requirements to account for is this:
1. Must be ~8Ω nominal. Do we want to allow 6Ω models in here as well?
2. Price is constrained. $380 is too much (I agree!). Does $150 or less sound reasonable? $200?
Here are a few more that might fit what we're looking for better. Are we willing to consider ribbons?
Fountek NeoCd2.0M
Fountek NeoCd3.5H
Audax TW025A20
I have read good things about the Fountek ribbons - I think it was on zaphaudio? Very low distortion, which tends to be difficult to find in a ribbon from what I've seen.
Edit: The audax is only listed as 93 dB, but we might be able to get away with slightly lower sensitivity due to baffle step correction.
What I'm hearing for additional requirements to account for is this:
1. Must be ~8Ω nominal. Do we want to allow 6Ω models in here as well?
2. Price is constrained. $380 is too much (I agree!). Does $150 or less sound reasonable? $200?
Here are a few more that might fit what we're looking for better. Are we willing to consider ribbons?
Fountek NeoCd2.0M
Fountek NeoCd3.5H
Audax TW025A20
I have read good things about the Fountek ribbons - I think it was on zaphaudio? Very low distortion, which tends to be difficult to find in a ribbon from what I've seen.
Edit: The audax is only listed as 93 dB, but we might be able to get away with slightly lower sensitivity due to baffle step correction.
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Kaffimann
For me no hurry
I am thinking about a cabinet concept and saw this basreflex port issue.
Take your time, i like that you have a look at it with your experience.
Hah!
Experience... I'm just being difficult. But I did spend almost 2 years planning and simulating different drivers to plan my 100db/2.83v setup. And it was a lot of simulations, several hours almost every day to wring the most performance out of as little money as possible.
... I wonder how much time Bjorno has spent in his life planning, simulating and building.
I don't get it. You are paying shipping and tax for virtually EVERYTHING you buy. AE drivers are not special in this regard!?
Yes they are, because he can get the Faital Pro 15FH520 for 178£ each from Bluearan, and the shipping would be maybe 3£ each, no more costs or taxes. So about 181£ total per driver.
The cheapest AE TD15X drivers are 349$ each, and the shipping might be 70-80$ (per driver average if ordering several? Ordering a single one would be over 100$), so that's MINIMUM 419$/317£ per driver, before any other taxes and fees. The UK tax is what, 20%? So that's an additional ca 84$/63-64£ per driver, if ordering several at a time (cheapest option) it totals at 503$/380£ per driver.
The cheapest AE TD15X drivers are 349$ each, and the shipping might be 70-80$ (per driver average if ordering several? Ordering a single one would be over 100$), so that's MINIMUM 419$/317£ per driver, before any other taxes and fees. The UK tax is what, 20%? So that's an additional ca 84$/63-64£ per driver, if ordering several at a time (cheapest option) it totals at 503$/380£ per driver.
I made a first drawing for a cabinet. I like to have a model in Leap for some simulations.
Can this be something close to what we like to built? No problem to change dimensions and driver positions. Drivers are placed in golden ratio rectangles as much as possible.
Dimensions are W x H x D = 46 x 100 x 55 cm. The internal volume for internal midrange cabinet and woofer netto volume, exclusive the port, is 204 L counting with 22 mm walls and 30 mm front panel.
Subtracting 20 L bruto for the midrange cabinet, 5 L occupied by the drivers, about 5 L for bracing, remains 174 L netto for the woofer.
The basreflex port dimensions need some investigation. After the woofer types are chosen we can do that in more detail. Maybe we can choose 2 ports for a B4 version and 1 port for the extended one, just an idea…
I see that the ATC SCM100ASLT is a 12 inch version, so I looked more to the ATC SCM150ASLT with their 15 inch woofer.
Can this be something close to what we like to built? No problem to change dimensions and driver positions. Drivers are placed in golden ratio rectangles as much as possible
.Dimensions are W x H x D = 46 x 100 x 55 cm. The internal volume for internal midrange cabinet and woofer netto volume, exclusive the port, is 204 L counting with 22 mm walls and 30 mm front panel.
Subtracting 20 L bruto for the midrange cabinet, 5 L occupied by the drivers, about 5 L for bracing, remains 174 L netto for the woofer.
The basreflex port dimensions need some investigation. After the woofer types are chosen we can do that in more detail. Maybe we can choose 2 ports for a B4 version and 1 port for the extended one, just an idea…
I see that the ATC SCM100ASLT is a 12 inch version, so I looked more to the ATC SCM150ASLT with their 15 inch woofer.
Attachments
From my side I don't have much practical experience with port and internal cabinet resonances. I think you have more.
I will focus more on the system calculations.
For the minimum port area calculation I use the R.Small formula, see attach.Forgot about TD15X need for larger cab but how come I get around 81 cm2 for port area ? 150L w fb of 24Hz w port d of 10 and length of 21cm (port velocity around 12 m/s) ?
For the port length I use Leap, I thought it was rather correct.
We can compare our results, but finally it has to be measured. Very difficult to calculate it exactly w.r.t. filling etc...
I will have a look at it again.
Attachments
I do not understand the port and volume numbers, it should be ca 39,2cm wide if using a center brace of 22mm if my calculations are correct. not 37,2cm?
And the board for the slot port should be 43,7cm long from distance of front panel, or it will choke the port.
Correcting for this the numbers are as follows: 49,7cm deep * 41,5cm wide * 97,2cm height of the chamber, the board for the slot port is distanced ca 39,5cm from center of woofer, and the internal top of enclosure is ca 57,7cm distance from center of driver. (?)
Then this is the result I get, the port is then 196cm2 (39,2*6) and totals 51,4cm (43,7+5,2+2,5) length.
The maximum recommended power would be ca 250 (about 39 volts) real watts, at which you reach 12,4mm excursion and get about 21m/sec air velocity.
If the driver could be placed a little higher the high freq response would be better.
Other than that it looks ridiculously good.
Paul, please check my numbers.
Attachments
Some more explanation first.
For the upper port panel mounting I have foreseen 2 panels of 60 mm high, 22 mm thick and about 50 cm deep against the side walls to lie on the internal upper port panel. It is very practical to tune the port length.
I should not choose a fixed brace for the upper port panel, not in the prototype.
Then the width of the port is (460 - 2 x 22 - 2 x 22) mm = 372 mm. These side panels for mounting on the port panel are now 22m thick, that can be less, for example 18 mm. Then the port width can be 380 mm.
For the port length I had chosen 450 mm maximum. The internal cabinet depth is 498 mm and I made the internal upper port panel 420 mm long to keep the distance of the back port mouth 78 mm away from the internal back side.
You take 60 mm from the back side. If that is ok, we will do it, but it is more a curve in the port in that way with more local air turbulences. I am thinking while writing now. But that is the reason I took only 45 cm total port length. Also when you like to cover the back walls with dampening material, how will it be close to the port mouth with only 60 mm from the back side?
Your port area calculation is not correct now: 39.2 x 6 = 235 cm2 here in Belgium. Or you do a correction that I don’t understand maybe.
For the woofer position height, please look to the front view. I see there is a mistake in the side view in the drawing, I will correct that later.
Our netto internal volumes are almost the same. I take 22 mm for the wall thickness, and you 22.5 mm, a detail...
Edit:
Difficult to increase the woofer height with the current driver positions. Then we have to make the speaker higher.
But we also like to keep the depth for a maximal port length. The speaker internal volume wil become too high then.
Your port length calculation 51,4cm (43,7+5,2+2,5), I don't understand the 5.2 number, and I suppose the 2.5 number is the upper port panel thickness.
For the upper port panel mounting I have foreseen 2 panels of 60 mm high, 22 mm thick and about 50 cm deep against the side walls to lie on the internal upper port panel. It is very practical to tune the port length.
I should not choose a fixed brace for the upper port panel, not in the prototype.
Then the width of the port is (460 - 2 x 22 - 2 x 22) mm = 372 mm. These side panels for mounting on the port panel are now 22m thick, that can be less, for example 18 mm. Then the port width can be 380 mm.
For the port length I had chosen 450 mm maximum. The internal cabinet depth is 498 mm and I made the internal upper port panel 420 mm long to keep the distance of the back port mouth 78 mm away from the internal back side.
You take 60 mm from the back side. If that is ok, we will do it, but it is more a curve in the port in that way with more local air turbulences. I am thinking while writing now. But that is the reason I took only 45 cm total port length. Also when you like to cover the back walls with dampening material, how will it be close to the port mouth with only 60 mm from the back side?
Your port area calculation is not correct now: 39.2 x 6 = 235 cm2 here in Belgium
. Or you do a correction that I don’t understand maybe.For the woofer position height, please look to the front view. I see there is a mistake in the side view in the drawing, I will correct that later.
Our netto internal volumes are almost the same. I take 22 mm for the wall thickness, and you 22.5 mm, a detail...
Edit:
Difficult to increase the woofer height with the current driver positions. Then we have to make the speaker higher.
But we also like to keep the depth for a maximal port length. The speaker internal volume wil become too high then.
Your port length calculation 51,4cm (43,7+5,2+2,5), I don't understand the 5.2 number, and I suppose the 2.5 number is the upper port panel thickness.
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43,7 + 3cm for the front panel + 2,2cm for the board itself + 2,5cm added distance from the "bend".
I forgot I changed the port to 39,2*5cm. Sorry about that. 6cm from the back should be ok since the port is 5cm, so it should sort of "even out". The resistance in slot ports is higher than tubes, turbulence should not be a big issue, especially since it is this part that sees the highest air velocity, it will just be dampened. The extra 1cm will act as a buffer to reduce the unwanted effects.
I always calculate with half a mm extra, because of the glue and various other factors.
How high is the tweeter going to be? should we not plan to hit ear height sitting in a couch or comfy chair?
Edit:
I think a layer of dampening material on the right spots will even out the response and it will be about flat to 400hz.
I forgot I changed the port to 39,2*5cm. Sorry about that. 6cm from the back should be ok since the port is 5cm, so it should sort of "even out". The resistance in slot ports is higher than tubes, turbulence should not be a big issue, especially since it is this part that sees the highest air velocity, it will just be dampened. The extra 1cm will act as a buffer to reduce the unwanted effects.
I always calculate with half a mm extra, because of the glue and various other factors.
How high is the tweeter going to be? should we not plan to hit ear height sitting in a couch or comfy chair?
Edit:
I think a layer of dampening material on the right spots will even out the response and it will be about flat to 400hz.
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Thanks ... all understood. I will also take 22.5 mm for wall thickness then.
Tweeter heigth is 99 cm, I thought this is ok?
I placed the tweeter at 10.9 cm from top to respect the golden ratio. Otherwise our friend mbrennwa will not be happy.
What about the B4 basreflex option, a second port? Because it needs more port area...
I will adapt the cabinet drawings later.
Tweeter heigth is 99 cm, I thought this is ok?
I placed the tweeter at 10.9 cm from top to respect the golden ratio. Otherwise our friend mbrennwa will not be happy
.What about the B4 basreflex option, a second port? Because it needs more port area...
I will adapt the cabinet drawings later.
At this moment, it is expected the speaker sensitivity will be in the range 90 - 91.5 dB, dependent on the woofer that is chosen. So 93 dB could be just enough.
You can get pretty close to B4 using only a shorter port, reducing the port to let's say 33cm makes it go flat to nearly 30hz, but you seriously limit output below this, even if the impedance spike is 26-27hz somewhere I think actual perceived sound output will be near zero below 30 hz. It's also better than regular B4 alignment. The Faital Pro 15FH520 is actually the driver to choose when using the shorter port, it should have good perceived output to 25hz, but the group delay looks much worse.
The long port might help make sound to 18hz, it does not say so in the sim, and I do not like to estimate low end performance before it is measured, but I expect in-room downwards slope of acoustic power to be just over 110db at 18hz, not 107db.
Edit:
Just tried cutting off the top 20cm, not quite the same low-end of course, but it's just fine otherwise. And it looks much better up towards xo frequency.
The long port might help make sound to 18hz, it does not say so in the sim, and I do not like to estimate low end performance before it is measured, but I expect in-room downwards slope of acoustic power to be just over 110db at 18hz, not 107db.
Edit:
Just tried cutting off the top 20cm, not quite the same low-end of course, but it's just fine otherwise. And it looks much better up towards xo frequency.
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Calcultated with TSP:
- sensitivity TD15H 1m/2.83Vrms = 94.6 dB
- sensitivity TD15X 1m/2.83Vrms = 96.1 dB
almost conform AE datasheet.
Kaffimann,
IMO the speaker should be around 110 cm high to keep the tweeter high enough, it is 99 cm now. Also for the cabinet look it is better to make the speaker not too low, that is just my opinion.
To make the internal volume lower it is better to make the speaker less deep. But then the port becomes too short maybe.
Shouldn't we try to make the speaker 50 cm deep, the available woofer volume becomes around 150 L then. And see how far that we get.
IMO the speaker should be around 110 cm high to keep the tweeter high enough, it is 99 cm now. Also for the cabinet look it is better to make the speaker not too low, that is just my opinion.
To make the internal volume lower it is better to make the speaker less deep. But then the port becomes too short maybe.
Shouldn't we try to make the speaker 50 cm deep, the available woofer volume becomes around 150 L then. And see how far that we get.
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