GM I'm a bit confused are you saying that putting 2 passive radiators in my 35 liter box will not improve frequency response around 30-40Hz?! Then what will 2 radiators aposed to 1 radiator do for my sub...nothing?!
The software i have been using is basically an excel dokument, It's called Unibox and it is freeware (I dont have the money to buy loudspeaker software).
I am open to any and all suggestions/recomendations regarding my sub project. i only have one rule. The outside mesurements of the box must not exeed 42*42*42 cm which is 49 liters with out the drivers and the amplifier, and about 40 liters with the drivers and amplifier.
And again Thanx for all your help guys!
The software i have been using is basically an excel dokument, It's called Unibox and it is freeware (I dont have the money to buy loudspeaker software).
I am open to any and all suggestions/recomendations regarding my sub project. i only have one rule. The outside mesurements of the box must not exeed 42*42*42 cm which is 49 liters with out the drivers and the amplifier, and about 40 liters with the drivers and amplifier.
And again Thanx for all your help guys!
Nope.
Please re-read my posts for what performance gains doubling up PRs, i.e. two 'vents', yields.
Don't have Excel 2k loaded, so can't run Unibox.
Hmm, there is a dual PR scheme where one PR loads another in a double reflex like design. Maybe it designs one of these? The cab size goes up though, as does group delay, so not worth it IMO, but as always YMMV.
GM
Please re-read my posts for what performance gains doubling up PRs, i.e. two 'vents', yields.
Don't have Excel 2k loaded, so can't run Unibox.
Hmm, there is a dual PR scheme where one PR loads another in a double reflex like design. Maybe it designs one of these? The cab size goes up though, as does group delay, so not worth it IMO, but as always YMMV.
GM
The Amplifier is a digital 400Watt subwoofer amp. But I am not sure if the 400Watts are in 8 ohm or 4 ohm. I think it's in 8 ohm after all it's the model Jamo uses in their top of the line D8 sub. The only other thing I know about the amp, is that it has a highpass filter (3 or 4 order, can't remember which it is) that cuts in some where between 20 and 30Hz, and it 2 channels bridged into one.
Jonn:
An 8 ohm amp will deliver only half it's power into 4 ohms. You can tell it's power by it's voltage. At 4 ohms, 400 watts is 40 volts. 200 watts is 28 volts. Check with a signal generator and voltage meter, and subtract about 20% for the unloaded condition-max voltage goes down a bit when a real load is put on it. At least, in the amps I am familiar with.
I will try to get hold of Madisound today or twomorrow. However, I have simulations here from Subwoofer Simulator, a program by our own member, F4ier.
The first simulation is for a 12" Peerless XLS in a 40 liter box, 12" PR with standard 425 grams total on it-nothing added. 40 Volts is fed to it. that is 400 watts into a 4 ohm load.
The white line is the PR excursion,
the puple line is the driver excursion
the light green line is the total speaker response
See how 400 watts pushes the PR somewhat past it's limit of 22 mm:
An 8 ohm amp will deliver only half it's power into 4 ohms. You can tell it's power by it's voltage. At 4 ohms, 400 watts is 40 volts. 200 watts is 28 volts. Check with a signal generator and voltage meter, and subtract about 20% for the unloaded condition-max voltage goes down a bit when a real load is put on it. At least, in the amps I am familiar with.
I will try to get hold of Madisound today or twomorrow. However, I have simulations here from Subwoofer Simulator, a program by our own member, F4ier.
The first simulation is for a 12" Peerless XLS in a 40 liter box, 12" PR with standard 425 grams total on it-nothing added. 40 Volts is fed to it. that is 400 watts into a 4 ohm load.
The white line is the PR excursion,
the puple line is the driver excursion
the light green line is the total speaker response
See how 400 watts pushes the PR somewhat past it's limit of 22 mm:
Attachments
Try It With 2 Passive Radiators
Here is the Subwoofer Simulator printout for the 40 liter box with two 12" PRs. The power fed into this is 400 watts-actually 40 volts into a 4 ohm load. (Subwoofer Simulator lets you program in the voltage-it is up to you to decide what the wattage is at that voltage). I had to almost double the weight-750 g for the two, or 375 for each PR-to maintain the same tuning frequency.
Incidentally, here is the link where you can download this freeware program by our own member, F4ier:
http://www.geocities.com/f4ier/newsubsim.htm
It has over 20 different curves, which you can enable or disable at will.
I'll let others analyze for now. Overall, I would say that you can probably get away with a single PR if you feed 200 watts into the subwoofer. If you want to feed 400 watts into it, then you probably need two PRs.
Again, if your 400 watt sub amplifier is 400 watts into 8 ohms, then it is only 200 watts into 4 ohms. That is important for you to decide. I should point out that most commercially available subwoofer amp/crossover combos tend to be 4 ohm output. But again, your manufacturer might have had a custom run.
Check that output impedance out, if you can.
Oh yeah, one more thing. It sure looks like you can benefit from a low cut filter around 20 Hz or so.
PS: All these simulations are without room gain. Like GM, I think room gain is a great bonus, but it is better to get the output you need first and then take whatever benefits room gain gives you.
Here is the Subwoofer Simulator printout for the 40 liter box with two 12" PRs. The power fed into this is 400 watts-actually 40 volts into a 4 ohm load. (Subwoofer Simulator lets you program in the voltage-it is up to you to decide what the wattage is at that voltage). I had to almost double the weight-750 g for the two, or 375 for each PR-to maintain the same tuning frequency.
Incidentally, here is the link where you can download this freeware program by our own member, F4ier:
http://www.geocities.com/f4ier/newsubsim.htm
It has over 20 different curves, which you can enable or disable at will.
I'll let others analyze for now. Overall, I would say that you can probably get away with a single PR if you feed 200 watts into the subwoofer. If you want to feed 400 watts into it, then you probably need two PRs.
Again, if your 400 watt sub amplifier is 400 watts into 8 ohms, then it is only 200 watts into 4 ohms. That is important for you to decide. I should point out that most commercially available subwoofer amp/crossover combos tend to be 4 ohm output. But again, your manufacturer might have had a custom run.
Check that output impedance out, if you can.
Oh yeah, one more thing. It sure looks like you can benefit from a low cut filter around 20 Hz or so.
PS: All these simulations are without room gain. Like GM, I think room gain is a great bonus, but it is better to get the output you need first and then take whatever benefits room gain gives you.
Attachments
Here's Ingemar Johansson's project with Mmp = 1000 g
http://www.ijdata.com
Look for the "Ugly Duckling" project. It's a nice tutorial on speaker design using LspCAD and JustMLS. Ingemar used a 12" XLS and two 12" PRs massed up to 1000 g each.
"The original cone mass of the PR is 425g, therefore 575g weights was manufactured that was attached to the backside of the PR."
http://www.ijdata.com
Look for the "Ugly Duckling" project. It's a nice tutorial on speaker design using LspCAD and JustMLS. Ingemar used a 12" XLS and two 12" PRs massed up to 1000 g each.
"The original cone mass of the PR is 425g, therefore 575g weights was manufactured that was attached to the backside of the PR."
In my XLS-sub with 2 PR's i have 490g at the 290g type "drone cone" and it seems to be OK. One thing thoug, if you have 2 PR's be sure to mount them on opposite sides of the box or you will have a box that wants to jump around when the weights starts rocking.
And yes you'll need a high pass filter (or low cut if want) at a around 20.
Keld
And yes you'll need a high pass filter (or low cut if want
) at a around 20.An externally hosted image should be here but it was not working when we last tested it.
Keld
Catapult:
Ingemar Johansen? I must say he certainly is youthful looking for a fellow who lost the heavyweight championship to Floyd Patterson in 1951! That picture has to be from his second marriage, (at least).
More seriously, it is a good page and a very good tutorial. Well worth checking out.
Ingemar Johansen? I must say he certainly is youthful looking for a fellow who lost the heavyweight championship to Floyd Patterson in 1951! That picture has to be from his second marriage, (at least).
More seriously, it is a good page and a very good tutorial. Well worth checking out.
Keltic: I have tried the software you used, and came up with the same results as you (which is not exactly the same result as I got in my software, my friend got yet another result in his lspcad!!! weird).
As I allready mentioned, the sub amplifier has a higpass filter cutting in around 20-30Hz. so the excurtion of the driver will probably not get in to any trouble, besides the sub will never be driven at full power in my little room which is about 20M2.
I have desided to just build it a box of 37Liters and use my first calculations results, and just tune it from there if I'm not happy!!
I just have one more question! If i put the amp in the same box as the drivers (without shielding) would that make me a dumb-***
?? building a box within the sub for the amp will make i nessary to build a 20Liter larger box
As I allready mentioned, the sub amplifier has a higpass filter cutting in around 20-30Hz. so the excurtion of the driver will probably not get in to any trouble, besides the sub will never be driven at full power in my little room which is about 20M2.
I have desided to just build it a box of 37Liters and use my first calculations results, and just tune it from there if I'm not happy!!
I just have one more question! If i put the amp in the same box as the drivers (without shielding) would that make me a dumb-***
?? building a box within the sub for the amp will make i nessary to build a 20Liter larger boxWell, what are the dimensions of your sub amp? The volume must be deducted from the volume of the box.
There have been threads where the question is debated: Does the vibration hitting the outside of an amp translate into distortion on that amps circuitry? Many say, "Yes".
For that reason, many builders do build a partition between their amp and the rest of the box.
However, many builders do not, and seem not to notice the difference. The choice is yours.
If I were buidling a larger speaker, I would take the extra space to build a speaprate compartment for the amp. If were dedicated to making the smallest box possible, I would just stick the amp inside the box.
There have been threads where the question is debated: Does the vibration hitting the outside of an amp translate into distortion on that amps circuitry? Many say, "Yes".
For that reason, many builders do build a partition between their amp and the rest of the box.
However, many builders do not, and seem not to notice the difference. The choice is yours.
If I were buidling a larger speaker, I would take the extra space to build a speaprate compartment for the amp. If were dedicated to making the smallest box possible, I would just stick the amp inside the box.
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