Hi Chris,
The comparison was 2ft^3 sealed vs 3.7ft^3 vented per driverSorry I should have been more clear.
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The more I sim those woofers, the more I would lean towards using 6 rather than 12. When limited to 45ft^3 for all of the woofers, 12 does nothing but increase initial costs, increase power requirements, and increase long term operating costs compared to 6. Once it's EQed out flat the additional drivers do nothing but waste more energy.
Hmm. What if they are running as IB though. With a whole in the bottom of my enclosure that is just as big a the box itself wouldn't the enclosure act as a big huge IB box? If so then I would assume the additional woofers will allow me to play lower and at less effort?
IB would work well for efficiency.
Ran the sims again to double check and came up with this:
Blue is 6 drivers, 45ft^3, vented.
Green is 12 drivers, 45ft^3, vented.
White is 12 drivers in 24ft^3, sealed.
Yellow is 12 drivers, 45ft^3, sealed.
Orange is 12 drivers, IB (simulated via 1000ft^3 sealed box)
Signal levels are chosen based on where Xmax is reached for the system above 20hz. The vented enclosures are tuned slightly differently to match Pe at 20hz with the bottom of the Pe "dip" above tuning frequency.
Ran the sims again to double check and came up with this:
Blue is 6 drivers, 45ft^3, vented.
Green is 12 drivers, 45ft^3, vented.
White is 12 drivers in 24ft^3, sealed.
Yellow is 12 drivers, 45ft^3, sealed.
Orange is 12 drivers, IB (simulated via 1000ft^3 sealed box)
Signal levels are chosen based on where Xmax is reached for the system above 20hz. The vented enclosures are tuned slightly differently to match Pe at 20hz with the bottom of the Pe "dip" above tuning frequency.
Attachments
Great. Thanks for all the effort! One more question. I see that the IB have 200W as input and it plays at the orange curve. Is this the limit of the 12 drivers? What if I indeed had 800W per tower of six woofers?
Hi,
In that case IMO about 50W per driver might be about right.
There is no point limiting excursion further up with low power.
This is the case with all low Q sealed or IB alignments.
rgds, sreten.
I like that! Maybe I could do a test tone over in the US and thus save on shipping on the way over as well I'm still waiting for MCM to return my query about shipping. Hopefully I'll find a way of getting them over here.
To me it sounds like 116db at 20hz is good enough. If the curve is correct then I will even have some 105 db at 10hz . Will I really?
What is reference level by the way?
I've seen some powerful IB systems where people are using 8 18" proper high quality subwoofers with high excursion. They feed them with loads of power. How loud will those play and will they ever use their full potential? I the reason sound quality?
Hello exipnos,
The "curve" is based on maximum power input at 20hz, not 10hz. In the IB, your maximum SPL before over-excursion at 10hz is going to be slightly lower, with a max Pe of just 10W per driver before going over Xmax.
These simulations are based on the idea that you are taking a measurement at 1 meter in open space. In the real world, when you are dealing with large numbers of woofers, the simulations and the real world performance don't match up as well, and more importantly, they do not bring into effect room loading characteristics at all. Generally speaking, you can count on there being some overlap in losses and gains when you factor in driver positions and room loading, at the end of the day it's all very academic and isn't a major issue IMO (other's will argue differently). The reality is, if you put 12 x 15" drivers in a home theater, it doesn't really matter what the simulation looks like, you can expect some pretty respectable sound levels through most of the listening range depending on how they are boxed up and EQed.
Reference is generally considered to be ~110db, however, that depends on who you ask and at what frequency you are dealing with. Some would consider reference to be ~110db except in the bass range, where it is more like 115-125db by some standards.
The "curve" is based on maximum power input at 20hz, not 10hz. In the IB, your maximum SPL before over-excursion at 10hz is going to be slightly lower, with a max Pe of just 10W per driver before going over Xmax.
These simulations are based on the idea that you are taking a measurement at 1 meter in open space. In the real world, when you are dealing with large numbers of woofers, the simulations and the real world performance don't match up as well, and more importantly, they do not bring into effect room loading characteristics at all. Generally speaking, you can count on there being some overlap in losses and gains when you factor in driver positions and room loading, at the end of the day it's all very academic and isn't a major issue IMO (other's will argue differently). The reality is, if you put 12 x 15" drivers in a home theater, it doesn't really matter what the simulation looks like, you can expect some pretty respectable sound levels through most of the listening range depending on how they are boxed up and EQed.
Reference is generally considered to be ~110db, however, that depends on who you ask and at what frequency you are dealing with. Some would consider reference to be ~110db except in the bass range, where it is more like 115-125db by some standards.
FYI:
The European 15” WM.STX.15.2.500.4.F.S.MC is not that expensive:
WM.STX.15.2.500.4.F.S.MC - Kino domowe, g?o?niki, kolumny - STX polski producent
Here in a T-TQWT:
b
The European 15” WM.STX.15.2.500.4.F.S.MC is not that expensive:
WM.STX.15.2.500.4.F.S.MC - Kino domowe, g?o?niki, kolumny - STX polski producent
Here in a T-TQWT:
b
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Hej Bjorno,
Around 34E per driver. A bit more expensive but shipping probably cancel that out. 10mm lineat excursion is better the the MCM woofer. Hmm I wonder how this one models in a IB?
Do you have any experience about this driver? Anybody at hififorum that might have used it?
Tack
Hej exipnos,
I will make a try to model an IB later this evening...No I don't have any experience but I think there is members here who have.
Maybe?
Var-så-god!
b
I guess this driver isn't good for IB use: The Xmax
and Qts are the limiting factors..b
Attachments
Maybe they are not optimal and not the most powerful ones, but I would have thought that 12 of these drivers will work better then the MCM drivers in the IB. Their Qts is about the same and these drivers have 10mm xmas instead of MCMs 6mm.
Hi,
As its peak to peak no it isn't if the MCM 6mm is one way,
i.e. the MCM driver is 12mm peak to peak excursion.
rgds, sreten.
I got mixed up in the thread.. Sorry
I thought that bjorno was modeling the MCM drivers IB and making comments regarding said drivers. I missed the driver change up. I apologize. The originally proposed MCM driver would likely be better in an IB when comparing the 2 driver options in an IB scenario, assuming both driver specs are honest.
I thought that bjorno was modeling the MCM drivers IB and making comments regarding said drivers. I missed the driver change up. I apologize. The originally proposed MCM driver would likely be better in an IB when comparing the 2 driver options in an IB scenario, assuming both driver specs are honest.
Ah I thought it was the other way around. So the STX is clear in its spec that its peak to peak. The MCM only says xmax 6mm. Are we certain that its one way travel?
Hi,
No we are not certain and that can be very frustrating,
But the 6mm spec should be one way. The spec sheet
says the voicecoil overhang is 6mm, should allow +/- 6mm.
rgds, sreten.
This is an incredible setup.
however, iirc, he said he wanted 3 towers for his front stage and one for lfe?
if this is so its possible that it may not work as optimally as is presented.
bass management will require all drivers to be on lfe or lfe to be distributed through all 3 front channels with said channels being set to full range and usind an active xo on the amp to drive the drdrivers.
also there is the prospect of mobile lfe, where a wave of lf sound moves accross the front stage.
i expect however it turns out you are in for a ride!
the most startling experience ive had with ht was a store demo of Jurassic Park. When the trex dropped the goat leg on the roof of the tour vehicle i jumped out of my seat. The store owner/system designer thanked me at the end of the movie! It was 6 12" drivers, so you can expect to be afraid, VERY AFRAID!
however, iirc, he said he wanted 3 towers for his front stage and one for lfe?
if this is so its possible that it may not work as optimally as is presented.
bass management will require all drivers to be on lfe or lfe to be distributed through all 3 front channels with said channels being set to full range and usind an active xo on the amp to drive the drdrivers.
also there is the prospect of mobile lfe, where a wave of lf sound moves accross the front stage.
i expect however it turns out you are in for a ride!
the most startling experience ive had with ht was a store demo of Jurassic Park. When the trex dropped the goat leg on the roof of the tour vehicle i jumped out of my seat. The store owner/system designer thanked me at the end of the movie! It was 6 12" drivers, so you can expect to be afraid, VERY AFRAID!
Hi,
The plan seems to be two towers with 6 drivers each, with 3 drivers
front and back for force cancelling, connected into the floorspace
for infinite baffle loading, both being LFE I would assume.
This will work, excellent use of a 15" driver with a Vas of over 10cuft each,
giving a excellent critically damped Q of ~ 0.5 at 33Hz. Nevertheless like
all sealed and IB arrangements excursion increases relentlessly the lower
you go down, and I'd recommend a plate amp with a Q=2 high pass filter
for low bass boost and excursion control below 20Hz for max volume.
PE do one with a peaking 18Hz high pass filter, should be ideal.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-750
http://www.parts-express.com/pdf/300-750.pdf
The towers only have to be about 1 feet deep, 1.5 feet wide and 5ft tall
(or taller to match the mains), still tiny for 6 x 11.5 cuft Vas drivers.
rgds, sreten.
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