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Discussion Starter · #1 ·
Mike, I know I shouldn't do separate threads for every idea..so if you delete/combine/ or move this I understand... I just like to keep different ideas separate.

So I will never ever seal ( infinite baffle included) a sub again if I can help it. I like my 128 cubed 10-15Hz tune idea..may stick with it. Tapped or any other horn doesn't look feasable for this driver. Thank you Mike Cason for getting me to do what I should have done a while ago... learn to plot PRed!

So I have begun, I couldn't find the 15" AE PRs Mike was refering to so for now I used:

AE Passive Radiators PR18-1600

Fs: 4 Hz
Qms: 85
Vas: 1840 L
Mms: 1600 g
Sd: 1200 sq cm
Vd: 9 L
Xmax: 3" p-p

PR18-1600 Highlights:
Soft compliance for optimal performance
Capable of moving nearly 9L of air
Cast aluminum frame
Can be custom massed for any desired tuning




They appear to be too good... too low... I am aiming for a 10Hz-15Hz tune with an exaggerated 8Hz-18Hz hump, little concern for 18Hz-35Hz, and NO concern for 35Hz on up! I am NOT looking for flat!

So I was able to add and subtract the number of PRs, add mass, and alter volume.... I've got a lot of playing to do, I had a few questions but I'll ask tonight after work! If anyone wants to play, I'm all eyes for some plots resembling the 128 cubed 10Hz tune plots and 15Hz tune....
 

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Discussion Starter · #2 ·
alright so I plotted 125cubes 10Hz vented and 125 15Hz to compare to for a desired goal. Then I did plots with 1, 2, 3, and 4 PRs to compare what adding PRs does...defaut was almost 10 cubes I believe. Then I changed them all to 100 cubes to see what that did.



 

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and the verdict is?

Arent PR's a little unpractical in a box that large? i mean there really isnt gonna be too much motion is there? i may be wrong as ports work in boxes that large but the PR idea... to me it needs some kind of air compression inside the box to push it out... i think the total amount of air to compress would be too high in a box that large. someone correct me though i hope im wrong.
 

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Discussion Starter · #4 ·
and the verdict is?

Arent PR's a little unpractical in a box that large? i mean there really isnt gonna be too much motion is there? i may be wrong as ports work in boxes that large but the PR idea... to me it needs some kind of air compression inside the box to push it out... i think the total amount of air to compress would be too high in a box that large. someone correct me though i hope im wrong.
I'm going to take a stab at it and say I used to think that the larger a box was the less air you got forced through the port, so the larger the box yields less output..gain... from a port. This is untrue I guess so I'm going to guess before looking at excursion plots that it's the same with PR... either no effect or you actually get more excursion the larger the box.
 

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Discussion Starter · #5 ·


excursion increases with 500 watts input across the board... 10 cubes, 20 cubes, 40 cubes, 100 cubes

blue is hard to see, but, also note the peak frequency shifts!
 

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Discussion Starter · #6 ·
How do I get the PR plots to match the ported plots? I've added volume but too much brings the peak down too low as the PRs Fs is 4Hz... too little airspace and the height of the peak gets too low. I seem to get the best results with 4 PRs vs 3, 2, or 1... maybe I should try more PRs...
 

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Okay. i guess it makes sense, i always forget how much air these large excursion drivers are capable of sweeping. I think in terms of cost/build benefits, wouldnt it be just as effective to use a giant port and SLLT the box?
 

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Discussion Starter · #8 ·
I think I may end up doing just that, especially since it's looking like for what I want ( very different than from what anyone else wants ) I will need quite a few PRs and still need lots of internal volume. But I'm in it to learn! I've been meaning to learn PRs for years, same as horns, thanks again Mike for getting me to just go for it. Even if I never build one, I'd like to grasp the concepts, rules, of PRs.

Can anyone please guide me to how I can model a PR system with a Maelstrom-21 that matches up with 125 cubes vented with a 10Hz tune and another with a 15Hz tune please? I played and I can't... I assume it's because of the PRs and I need to try with PRs with higher Fs. I'll try it myself when I can.

Thank you!
 

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Turns out that its pretty much a wash. theres very little difference in output, we're talking less than 1.5 dbs at max power when comparing 90 cubes at 8hz vs 125 at 8 hz. and aiming for 10 hz is only a 1 db gain again but a loss of overall output down low. I'd tune for 8 hz, at 90 cubes, give it a monster port roughly 16 inches diameter. 81 inches long :O lol! this will still chuff at full power though. 10hz is only 48.25 inches of port. but with that 21 it seems that you'd need a 24" port to get rid of noise at full power. 193 inches long...

125 cubes at 10hz is the best tradeoff. 82.4" of port with a 24" diameter. Max air speed is 22 m/s at 9.6hz at 1500w The 8hz tuning would be for the lowest note possible on a full sized organ. But then again, theres almost no music and very few movies with real content that low. (118 db at 10hz is insane.) factor in room gain, thats closer to 125-128... Ouch.
 

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Discussion Starter · #10 ·
I dont recall the details but I figured if I simply use 4'x8' sheets to make 4 sides and 1 to cut in 1/2 for top and bottom, thats 128 before displacement. Assuming 125 cubes to be on the safest side, I could use a 16" port that would result in a 10Hz tune if I keep it 16" off the rear wall for port clearance. After playing for a while, I may raise it to 15Hz... but as I am enjoying this 18" IB3 off 60ish watts with a terrible 45Hz bass boost with only an 18Hz tune... I think the "terible" loss in output staying at 10Hz vs 15 will be actually just what I want.

a 24" port to keep a 21" from chuffing... doubt it...
 

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Discussion Starter · #11 ·
OK... so what is the best way to get the most output from 8Hz-18Hz? Flatness is not an issue. Space is not an issue. $2000 on drivers $500 on amps. IB? Sealed? Ported? 4th order? 6th order? 8th? Tapped? Front loaded? 50 12's or 4 21's?

I changed my frequency range on my WinISD to show 1Hz-20Hz as I am NOT concerned with anything above 20Hz with this.

I used the M21 for now, no consideration for power given, no filtering, just a quick FR curve
1 yellow default sealed
2 yellow 125 cubic feet sealed
3 grey default vented
4 grey 125 cubes 10Hz vented
5 turquois 4th order
6 turq played a little for a 16Hz tune total 125 cubes ( needs a lot more time to tweak)
7 red IB 999 cubic feet

 

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I'm curious, it looks like you want to maximize the efficiency and output between DC and 18Hz or so?

What do you have in your system that will take care of >18Hz?
 

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Discussion Starter · #13 ·
I'm curious, it looks like you want to maximize the efficiency and output between DC and 18Hz or so?

What do you have in your system that will take care of >18Hz?
yes, 8Hz-18Hz_ish. haven't got that far yet... 18Hz on up should be easy :)





looks like 6th order is what I need!
 

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Are you checking the Xmax in any of these graphs?
Also power input.

I think he should just buy 2 EP2500's ($600) and buy 8 Fi IB 18's ($1600), IB them. That would be way over the top already. If he really wants to get crazy just build a 350cu ft enclosure in the basement for the 8 18's and somehow port it at 8hz into the upstairs with a 24" OD x 37" deep port. No port overload even with 5000w system input. Might seriously be able to do this:hsd:


Ryan,

You've already said that you don't care about the FR curve so why even look at it? you need to be looking at the spl curve with huge input power, xmax limited.
 

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Discussion Starter · #16 ·
Also power input.

I think he should just buy 2 EP2500's ($600) and buy 8 Fi IB 18's ($1600), IB them. That would be way over the top already. If he really wants to get crazy just build a 350cu ft enclosure in the basement for the 8 18's and somehow port it at 8hz into the upstairs with a 24" OD x 37" deep port. No port overload even with 5000w system input. Might seriously be able to do this:hsd:


Ryan,

You've already said that you don't care about the FR curve so why even look at it? you need to be looking at the spl curve with huge input power, xmax limited.
I told you I listen to you... that's why I plotted all this and tried everything I could :help:

plotting 8 18's vs 2 21's 6th order.....
 

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Discussion Starter · #17 · (Edited)
8 IB3182's in default sealed 1236 cubes, 9999 cubes sealed for IB, and 99999 cubes ..... add another 9 and it drops...what gives?



why is there a #1 and #2 for the downloadable Shiva and Tempest files? I DLed #2



notice 16 Shiva I could only do 999 cubes, one more 9 and it goes down, 12 Tempest in 9999 and 8 IB3 in 9999



1300 brings shivas to 26mm 900 brings tempests to 26mm and 2300 brings IB3s to 30mm

 

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Also power input.

I think he should just buy 2 EP2500's ($600) and buy 8 Fi IB 18's ($1600), IB them. That would be way over the top already. If he really wants to get crazy just build a 350cu ft enclosure in the basement for the 8 18's and somehow port it at 8hz into the upstairs with a 24" OD x 37" deep port. No port overload even with 5000w system input. Might seriously be able to do this:hsd:


Ryan,

You've already said that you don't care about the FR curve so why even look at it? you need to be looking at the spl curve with huge input power, xmax limited.
Now that would be insane. I wish I could blow $1600+ on speaker stuff :innocent:

Edit: I wish I had that much money lol :bigsmile:
 
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