Here's the room. At "A" the 30-40Hz bass was not as loud or effective as at "B". What causes this?
The room is only a little smaller than the OP's room. Seems relevant.
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Usually uneven coverage at low frequency is due to modal activity. There are room mode calculators online but they are very simple. For precise answers you would need to provide info about construction materials (rigidity), leakage (doorways, cracks, HVAC holes) and a precise layout (taking into account the overall dimensions of the group of rooms and the boundaries and doorways between them) and absorbtion (furniture, carpeting, etc), among other things. In other words, it's currently impossible to map out response accurately at any given spot in a room but if the room booms it's probably caused by standing waves.
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No, the SI 18 doesn't need anywhere near that much space and can't handle even close to that amount of power.
If used in IB you can fit 5 drivers on an 18 inch cube manifold. You can increase the depth of the manifold and fit more drivers per manifold if you don't mind keeping the low pass crossover relatively low. Or just use more manifolds. Even in a sealed box you can go as low as 4 cubic feet, lots of people do it.
As for power, these are rated at 600 watts rms and I wouldn't push it too far past that. They have a tiny 2.5 inch voice coil and they will burn if you get too aggressive. (They are fairly new and I've seen reports of burned voice coils from experienced users.)
Dear all ,
thanks for all your comments... forgive me if i am going a little too ahead.... But I have a doubt... if iam going to use conventional 18" drivers ... what type of enclosure will help me to achieve the best result in reaching the mark of 10Hz. or below ? taking the room to be a rectangle with (18' x 10'x 10') , with plain concrete walls and one door which may not be perfectly airtight......
regards,
Alex
thanks for all your comments... forgive me if i am going a little too ahead.... But I have a doubt... if iam going to use conventional 18" drivers ... what type of enclosure will help me to achieve the best result in reaching the mark of 10Hz. or below ? taking the room to be a rectangle with (18' x 10'x 10') , with plain concrete walls and one door which may not be perfectly airtight......
regards,
Alex
Here's an idea for sealed boxes for the SI 18 woofer.
4 cu ft Subwoofer box - Subwoofer Flat Packs DIY Sound Group
Shipping costs would be prohibitive to India but you can make your own.
Your room is fairly small and quite rigid if it's concrete, and probably airtight enough, so 2 or maybe 4 of the SI 18 woofers should be enough, depending on how low you want to go and how loud you want it to be.
4 cu ft Subwoofer box - Subwoofer Flat Packs DIY Sound Group
Shipping costs would be prohibitive to India but you can make your own.
Your room is fairly small and quite rigid if it's concrete, and probably airtight enough, so 2 or maybe 4 of the SI 18 woofers should be enough, depending on how low you want to go and how loud you want it to be.
Back in the late 1970's Anicom Sound in Minneapolis used to use a large sealed cabinet called the "Futz" which had 4 drivers on a triangular manifold, three on the sides, one in the back.
The rear driver consistently was ruptured while the other three never had any problems.
There are tougher cones now (the Futz used JBL 15" woofers) but I still would not put a single cone in the back space of a manifold, even if it would not tear up the cone, it would probably add distortion.
I'm having trouble imagining this layout. A quick search didn't lead to any pics of this creation. Are you saying the manifold exit was at the peak of the triangle (like a pyramid)? If so that's an extremely odd layout and I'm not sure why the manifold exit would be made smaller than the cross sectional area where the woofers mount.
Maybe I'm not imagining it right, but any type of triangular manifold sounds very odd and a very bad idea.
Anyway, afaik only pressure can rupture cones and there shouldn't be any pressure worth noting in a 5 driver IB manifold with a consistent cross sectional area and an exit equal to the cross sectional area. Using a smaller sealed box would be different, that could generate extreme pressures.
I can't imagine why the 5th driver would add distortion. It wouldn't have the benefit of opposed forces that the other 4 drivers have but that's not adding distortion, it's just not benefiting from reduced opposed forces distortion.
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A manifold can have just two opposing drivers, or 3, or 4 or more.
Normally the back of the manifold is simply a wall, you suggested putting an additional driver there, just like Anicom did with a three sided manifold.
Showco did have a four driver pyramidal arrangement which worked OK around the same time period (probably the inspiration for the Futz), as would a tetrahedral arrangement with only three drivers.
The 3 (or in your suggestion) four side drivers are all pushing air, the air pressure is at maximum in the center. The rear cone is also pushing air, but is also pushing against the maximum concentration of pressure, and is subjected to more pressure than the rest of the cones.
Extreme throat pressure causes cone flex, which causes distortion, even if it does not lead to cone destruction, as it did with the rear driver in Anicom's Futz arrangement.
I have tested many horn loaded units for distortion, the distortion at a given excursion is more than the front loaded counterpart.
A quad loaded manifold gives around a 3/1 compression ratio, higher than many horn cabinets.
After tearing up the rear cones a number of times, if I recall correctly, the Anicom guys put a plate over the place where the cone was, and had no more problems running three drivers. Those JBLs were very expensive, they learned the hard way that the back cone would not hold up.
The cabinet still was a pig though, the efficiency of a large sealed cabinet could not compare to the rest of their horn loaded system.
Art
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Isn't the size of the enclosure in direct relation to the lowest frequency extension, in this case ~F12=10Hz (80dB - ff, from 92dB). I assume you are using active equalization, can you elaborate.
The power I mentioned is just the power needed to achieve max extension (Xmax) and respective SPL, given by the software. I was not looking at any limitations of the driver of max accepted input power or other restrictions. If the driver burns with less power I assume it can not play at max. volume for required output (voltage) of 94.65 V.
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I didn't design the driver and I didn't come up with the enclosure size recommendation. The manufacturer won't honor the warranty if he knows you pushed it past 600 watts, and if the vc burns it was definitely more than 600 watts.
This driver (an early prototype I think) was tested by data-bass.com and he put way more than the rated power through it with no problem (95 volts I think). Data-Bass
But IIRC a member of avsforum fried a pair of them with a couple of 1000 watt amps, so YMMV.
The enclosure recommendations come from what I've read at avsforum, lots of people are happy with 4 - 6 cubic foot sealed boxes.
I don't own these drivers and I've never seen them IRL and haven't spent much time simulating them so I don't know if people are using more than the recommended power or if they use eq. And I don't care much, lately I've been much more interested in 30 hz and up.
Hi again Alex,
It all will downsize probably to a domestic or semi-pro installation. Do you have access to international drivers from overseas or is your market only local. What is your max. size (internal volume/external dim.) enclosure you can afford as a footprint (taking the) space in your room, that is important to chose the driver.
That was my point previously but you never said anything about this constraint (max. enclosure volume).
Not nice.
It's not the requirement from OP (read #26). I just don't beat a dead horse. Hate that and what good or bad projects others achieved in other forums. My intentions are more related to this one and the possibility of making it work, with the limited experience from the simulations and learning in the process. If others have been there, fine with me. More power to you.
New SI HT woofer specs and info - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com
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Other references to look at in the infra category:
Dayton Audio RSS460HO-4 18"
NEW SUB FROM PARTS EXPRESS DAYTON 18 HO"
Dayton Audio RSS460HO-4 18" Reference HO Subwoofer 4 ohm 295-472
Rythmik DS1501
Rythmik DS1501 Build - Sealed Down-firing End Table
Rythmik Audio 15" servo subwoofer " DS1500 Custom Installation subwoofer
Rythmik Audio 15" servo subwoofer " DS1500 Custom Installation subwoofer - detail
Dayton Audio RSS460HO-4 18"
NEW SUB FROM PARTS EXPRESS DAYTON 18 HO"
Dayton Audio RSS460HO-4 18" Reference HO Subwoofer 4 ohm 295-472
Rythmik DS1501
Rythmik DS1501 Build - Sealed Down-firing End Table
Rythmik Audio 15" servo subwoofer " DS1500 Custom Installation subwoofer
Rythmik Audio 15" servo subwoofer " DS1500 Custom Installation subwoofer - detail
I read 26 and answered it in 27 (with further elaboration in subsequent posts).
I don't own this driver and have no experience with it. I've read conflicting reports of how much power it can handle. Personally I'd take it easy on it's tiny 2.5 inch voice coil and I probably personally wouldn't use it in a very small sealed box. Sealed boxes are not really my thing but that does seem to be it's most commonly used alignment and many people seem happy with it like that.
The OP hasn't really stated any firm goals. With no idea how much money he has to spend, how much space he has to spare (and if IB is even possible in his room), no spl goal and no firm frequency response goal (maybe 10 hz, maybe lower) there is no specific correct answer. He hasn't even given any indication if he likes these drivers or will be able to get them in his country.
I've shown what other people are doing with these drivers and I'm too busy lately to care about going beyond that, at least until the OP gives a bit more details about what he wants to achieve.
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