Hi Im having a change round in my AV room and want to build two subwoofers.
The spaces I have is would fit a subwoofer:
1000mm (39 inch) wide
700mm (27.5 inch) high
550mm (21.5 inch) depth
I have bought two Dayton Ultimax 18 inch drivers
Im quite good at building the boxes etc
But need some help on the sizes of the ports and what id expect out of the finished subwoofers in frequency and volume?
I would be building out of 1 inch MDF...many thanks
The spaces I have is would fit a subwoofer:
1000mm (39 inch) wide
700mm (27.5 inch) high
550mm (21.5 inch) depth
I have bought two Dayton Ultimax 18 inch drivers
Im quite good at building the boxes etc
But need some help on the sizes of the ports and what id expect out of the finished subwoofers in frequency and volume?
I would be building out of 1 inch MDF...many thanks
Dunno about a mini Marty, but did a 250 L [net] sim awhile back for a poster, but he chose to use sealed. Anyway, tuned to ~19 Hz with a Sd/2 area vent 152 cm long to get a good enough 5.8 % max vent mach at 1 kW. In 1pi space it's >123 dB/1 kW/m from ~16 Hz, so two will be up to +6 dB more if you and the building can take it.
A full width shelf port will be shorter of course, which can be calculated with this, though no experience with it nor seen anyone post results, so can't guarantee how accurate it is: https://www.diyaudio.com/forums/att...rt-slot-port-math-effective-port-length-1-jpg
Attached my Hornresp sim record if you want to import to view/tweak.
GM
A full width shelf port will be shorter of course, which can be calculated with this, though no experience with it nor seen anyone post results, so can't guarantee how accurate it is: https://www.diyaudio.com/forums/att...rt-slot-port-math-effective-port-length-1-jpg
Attached my Hornresp sim record if you want to import to view/tweak.
GM
I had a quick look at those, and I'm not keen on the cabinet design - the port area is tiny compared to how much air needs to be pushed through.
Depending on the size of your room, I'd consider sealed boxes with some EQ. Sealed boxes go all the way down below 10Hz since there aren't any cancellations, and usually allow a smaller box than a ported design.
Ported will get much louder down to the cutoff frequency, but will do very little below that. With a pair of 18"s in a UK-sized room, I'd go sealed.
Chris
Hi thanks,
My room is 3m x 6m x 2.4m high and the two subs will be placed under my projector screen.
I have a minidsp eq for my subs and would be using a inuke 6000 power amp to drive them.
They will be used for music and movies.
I could build a sealed box ?
What would the ideal size to fit into my space measurements?
I was on another forum and everybody seems to rave about the marty, mini marty subdo?
My room is 3m x 6m x 2.4m high and the two subs will be placed under my projector screen.
I have a minidsp eq for my subs and would be using a inuke 6000 power amp to drive them.
They will be used for music and movies.
I could build a sealed box ?
What would the ideal size to fit into my space measurements?
I was on another forum and everybody seems to rave about the marty, mini marty subdo?
A Dayton Ultimax UM18-22 has dual 2 ohm coils. You have two woofers, so you can wire them to get two 4 ohm loads. At this impedance an iNuke 6000 delivers 2x 2200 W according to the specifications. The woofer can handle 1000 W (long term I guess), so the woofer is the limiting factor. Short term power handling of the woofer should exceed 2200 W.
As you have a DSP available, the frequency response curve does not matter, because the DSP can turn it into anything you want. Then the maximum output is important. For a closed box, that can be limited by the thermal power handling of the woofer (1000 W) or the mechanical excursion limit (22 mm). If you build a closed box of at least 200 L, both limits will be reached at the same time. Building a larger box has no advantage, building a smaller box is OK but reduces the maximum output. If you only want to hit the maximum excursion for short time periods, you can take 2200 W as the electrical input power and the excursion limit can be reached in a box of at least 80 L.
I would build something between 80 and 200 L, for each woofer.
As you have a DSP available, the frequency response curve does not matter, because the DSP can turn it into anything you want. Then the maximum output is important. For a closed box, that can be limited by the thermal power handling of the woofer (1000 W) or the mechanical excursion limit (22 mm). If you build a closed box of at least 200 L, both limits will be reached at the same time. Building a larger box has no advantage, building a smaller box is OK but reduces the maximum output. If you only want to hit the maximum excursion for short time periods, you can take 2200 W as the electrical input power and the excursion limit can be reached in a box of at least 80 L.
I would build something between 80 and 200 L, for each woofer.
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3x6 m is a small room for two Ultimax 18", have you at least tested them both without any box? at least you know what you are dealing with.
build sealed subwoofer and apply eq from your dsp. I'm building stereo sealed subwoofer with 12" driver with nu3000dsp and bigger room 5x6m
btw how do you get the driver when you are in UK? i assume shipment is crazy high.
build sealed subwoofer and apply eq from your dsp. I'm building stereo sealed subwoofer with 12" driver with nu3000dsp and bigger room 5x6m
btw how do you get the driver when you are in UK? i assume shipment is crazy high.
+1 for sealed box with DSP equalization (Linkwitz transform). To get started, just choose the largest box dimensions that work ok for you. Then use the Thielle-Small parameters of your drivers and one of the Linkwitz spreadsheets to calculate the required compensation to get a flat response. Feed your DSP with these parameters and you'll get a very decent result. If you want, you can also measure the in-room or nearfield response to further tweak your subwoofer / DSP settings.
Since you have two woofers, I'd suggest to make the enclosure such that the two woofers are mounted opposite to each other (magnets facing each other). This will greatly help to reduce vibrations of the enclosure ("if one woofer wants to move the enclosure to the right, the other woofer wants to move the enlosure to the left in the same way.") The opposing forces will cancel out, so the enclosure will vibrate much less, which is a good thing.
Since you have two woofers, I'd suggest to make the enclosure such that the two woofers are mounted opposite to each other (magnets facing each other). This will greatly help to reduce vibrations of the enclosure ("if one woofer wants to move the enclosure to the right, the other woofer wants to move the enlosure to the left in the same way.") The opposing forces will cancel out, so the enclosure will vibrate much less, which is a good thing.
Hi thanks for the replies, I bought one driver second hand from eBay and the other also from eBay but new. It gets shipped from the Netherlands so works out at £400 with shipping.
What would be a perfect size for sealed cabinet?
It is two separate spaces I have so could not build a back to back cabinet due to size really. I like the idea of a sub under each left and right speakers too, more symmetrical for my OCD !
What would be a perfect size for sealed cabinet?
It is two separate spaces I have so could not build a back to back cabinet due to size really. I like the idea of a sub under each left and right speakers too, more symmetrical for my OCD !
As I already wrote, make them as big as it fits your situation. This will most likely lead to a misaligned woofer/box system, but that's what you have the DSP for. Just don't make the box too small, because the non-linearity of the air compliance will kick in at some point (see here), resulting in increased distortion.
I can get down to 1Hz.
A ported box puts out way more at (and a little above) the tuning frequency, but much less below, compared to a sealed box.
Some people choose lots of 20Hz, others like 10Hz but quieter.
Chris
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