Okay lets start off with some basics of what I hope to do here.
I have a pair Rockvilles Budget $60 18 inch subwoofer's they claim to be 1200w peak / 600w rms and the goal here is to create a dual 18, ported case for them.
Heres what I've come up with so far:
The case's winisd settings:
32ft3
30hz tune
1 square port 10 inch by 29 inch, 15.23 inch deep.
2 drivers
600w
80 feet distance
I am getting this max spl without any pEQ:
127db at 30hz
130db at 40hz
131db at 50hz
131db at 60hz
130db at 127hz
The plan is to cut them at 30hz and 130-150hz depending on how they sound.
I plan on using MDF for the first couple test cases (I assume I'll need at least two prototypes) then when I have a finalized design, using birch.
Played around with the sizes a bit more and I think the 32ft3 gives the best/tightest db spread along those hz bands. I tried 24ft3 and 16ft3 but the loss was 2-3 db and 4-5 db for each one, so the combined difference from 16ft3 to 32ft3 was pretty big. However the difference going past 32ft3 didn't seem to be as effective, 40ft3 only offering a extra 0.5-1db.
I played with the shape a bit more and by making the case 52inch x 30inch by 36inch deep instead of the 2x4x4. I made it roughly the same 32ft3 volume after I take into account my building edits that effect the volume inside such as cutting one of the back corners off for a spot to mount casters, port volume and handle volume ect. This makes it a bit taller, a bit wider in exchange to reducing how deep it is from 4f to 3f so its easier to manage and gives me enough room in the middle for the port, while also keeping the space between the edge of the case and the raw subwoofer mounting ring equal on all 4 sides.
When its already flat like this, should I even be using pEQ?
I'm only hitting 0.39 cone excursion so I'm pretty sure they could bump harder if my uneducated eyes are looking at this properly.
I'm seeing maybe 3 sheets of wood to build this.
While I am not concerned at all about the math convertions and the construction aspect of building the case since I think I can handle those pretty easily. However I am not the most educated person when it comes to winisd so crunching these numbers may look fine to me but I could be missing something. Once I have the correct numbers (volume/port sizes ect) I have no doubt I can easily build it, however I would love some input on this and have someone double check it, since I obviously don't know winisd all that well, but from what I can see this is the best case I've come up with and I feel like any changes I did, either added too much volume/size to be useful or didn't add enough extra db to make the change worth it. So I'm not sure how I could improve this from what I can see.
Open to suggestions that are not telling me to get other things aka to buy other subs or other amps. I already have these, I'd like to play with them and make the best case I can with the speakers I already have. Yes I'm aware there are better subs out there, however I don't own those, so unless your willing to DONATE me new subs, please don't suggest other subs since these are the ones I own and will be using in this build.
I'm going to wait for a bit of feedback and hopefully start construction not this weekend, but the weekend after.
I have a pair Rockvilles Budget $60 18 inch subwoofer's they claim to be 1200w peak / 600w rms and the goal here is to create a dual 18, ported case for them.
Heres what I've come up with so far:
The case's winisd settings:
32ft3
30hz tune
1 square port 10 inch by 29 inch, 15.23 inch deep.
2 drivers
600w
80 feet distance
I am getting this max spl without any pEQ:
127db at 30hz
130db at 40hz
131db at 50hz
131db at 60hz
130db at 127hz
The plan is to cut them at 30hz and 130-150hz depending on how they sound.
I plan on using MDF for the first couple test cases (I assume I'll need at least two prototypes) then when I have a finalized design, using birch.
Played around with the sizes a bit more and I think the 32ft3 gives the best/tightest db spread along those hz bands. I tried 24ft3 and 16ft3 but the loss was 2-3 db and 4-5 db for each one, so the combined difference from 16ft3 to 32ft3 was pretty big. However the difference going past 32ft3 didn't seem to be as effective, 40ft3 only offering a extra 0.5-1db.
I played with the shape a bit more and by making the case 52inch x 30inch by 36inch deep instead of the 2x4x4. I made it roughly the same 32ft3 volume after I take into account my building edits that effect the volume inside such as cutting one of the back corners off for a spot to mount casters, port volume and handle volume ect. This makes it a bit taller, a bit wider in exchange to reducing how deep it is from 4f to 3f so its easier to manage and gives me enough room in the middle for the port, while also keeping the space between the edge of the case and the raw subwoofer mounting ring equal on all 4 sides.
When its already flat like this, should I even be using pEQ?
I'm only hitting 0.39 cone excursion so I'm pretty sure they could bump harder if my uneducated eyes are looking at this properly.
I'm seeing maybe 3 sheets of wood to build this.
While I am not concerned at all about the math convertions and the construction aspect of building the case since I think I can handle those pretty easily. However I am not the most educated person when it comes to winisd so crunching these numbers may look fine to me but I could be missing something. Once I have the correct numbers (volume/port sizes ect) I have no doubt I can easily build it, however I would love some input on this and have someone double check it, since I obviously don't know winisd all that well, but from what I can see this is the best case I've come up with and I feel like any changes I did, either added too much volume/size to be useful or didn't add enough extra db to make the change worth it. So I'm not sure how I could improve this from what I can see.
Open to suggestions that are not telling me to get other things aka to buy other subs or other amps. I already have these, I'd like to play with them and make the best case I can with the speakers I already have. Yes I'm aware there are better subs out there, however I don't own those, so unless your willing to DONATE me new subs, please don't suggest other subs since these are the ones I own and will be using in this build.
I'm going to wait for a bit of feedback and hopefully start construction not this weekend, but the weekend after.
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You're not looking at it properly, your drivers only have 5mm(0.19") xmax so you need to reduce box size and raise tuning until you find a combo that will handle rated power without exceeding xmax, or tune it to something normal for a PA sub like 35-40hz and reduce input power. Then play with the port size until you find something that keeps rear port air velocity under 20m/s at whatever that max power ends up being.
What would putting the tune at 35-40 be helping? Wouldn't that lose me db around 30hz?
Do you have any reading material for this port air velocity under 20m/s?
It currently says 26f/s at 24hz peak... 20m/s is milla sec or meters per sec? If its meters I'd be within it, if its millasec I have no idea how to change over to that in winisd, clicking it didnt change it.
I see the ? 5mm ? in the sheet from a user here on diy audio (thats the one I have included) however I'm not totally sure if thats actually the real xmax since I've already bumped them harder then that in a gsub case, so thats a guess based upon some educated math, but isn't actually from the manufacturer (who refuse to give me the xmax btw cuz its all through audio savings so you get their customer service not a techie)
Yes. The basic rules of reflex sub design is larger boxes and lower tuning reduces power handling, so there are always tradeoffs to make for any given driver.
Check the help files in WinISD. When port air velocity exceeds 17 meters/sec it begins to generate audible noise, so the more power you throw at a design the bigger the ports need to be.
Click on the wrench(go into settings), all graph parameters can be changed there.
Those specs look believable and potentially appropriate, did that other member run tests to come up with those specs? I have never seen any manufacturer specs for this far east gear so that would be the only way to come up with them. How much power have you pushed through these in the Gsub enclosure? There is no free lunch, you can't get more output and lower response in a bigger enclosure without an increase in driver excusrion and every driver has it's limits.
It's highly unlikely these drivers have more than about 5mm xmax just based on their construction, look at any modern high excursion sub driver and you will see a bumped back plate not the flat plate that this driver has. Xmax is the one way linear excursion the driver can handle and maintain control of the cone. The cone can usually move more than this(sometimes only a few mm more, sometimes much further) but distortion increases dramatically and the relationship between increased power and increased excursion degrades such that it usually only takes a relatively small amount of extra power to reach xlim.. which is where the voice coil hits the back plate. This will be a metallic POP sound on dynamic bass hits, if a driver is pushed this hard repeatedly the voice coil will be damaged and the driver destroyed very quickly.
First off thanks for taking the time to explain things to me instead of just telling me not to do something.
I found the option to change it so now I have rear port air velocity on m/s and its nowhere near 20, tops out at 8.3m/s at 25hz.
So this means the only issue is the xmax then? Is cone excursion and xmax measuring the same thing or is there a calculation I'm missing here?
I've given these drivers 600w, they are for sure not 1200w subs and I got the first two rings moving and a bit of the 3d ring before I hit clip limiters on my amp.. I mean I could be wrong but I'm pretty sure I bumped them at least that xmax, a 1/5th of a inch isnt much and I'm not sure the 2nd ring would be moving from that.. but I for sure remember bumping them hard enough to move the 2nd ring out. 600w is prob the max I'd ever want to give these.
at what power level?
Xmax is maximum cone excursion.
What are these rings you are referring to here? What amp?
Your drivers are somewhat of an oxymoron in themselves. The high Qes (weak motor) and high Vas, demand a very large cabinet with a low tuning to give a nice frequency response. But as far as Xmax goes, they are made for small cabinets (10 - 15 ft^3 for the pair) with a tuning at or above 40 Hz.
Your approach is going for quality at the cost of quantity (output) so don't stretch it there. Not even going down hill, with the wind in your back that's a 600 Wrms driver, so don't treat it like one. So it's really about finding a balance between quality and quantity. Your current enclosure, with 300 W per driver and a steep high pass at 30 Hz, is probably somewhere around the edge of what they're capable of.
Your port is roughly 4 times as large as it needs to be, so it is well below 20 meters per second.
I would look at some current diy reflex cabinets and look how they solved bracing. In an enclosure that size you could probably double up on bracing.
Those rings are the accordion surround, there movement are not necessarily a good indication of the Xmax (maximum linear excursion). As soon as you hear a rise in distortion or see the cone moving side-ways or flopping around, you probably want to turn down the volume till they're in check again.
Johan
Your approach is going for quality at the cost of quantity (output) so don't stretch it there. Not even going down hill, with the wind in your back that's a 600 Wrms driver, so don't treat it like one. So it's really about finding a balance between quality and quantity. Your current enclosure, with 300 W per driver and a steep high pass at 30 Hz, is probably somewhere around the edge of what they're capable of.
Your port is roughly 4 times as large as it needs to be, so it is well below 20 meters per second.
I would look at some current diy reflex cabinets and look how they solved bracing. In an enclosure that size you could probably double up on bracing.
Those rings are the accordion surround, there movement are not necessarily a good indication of the Xmax (maximum linear excursion). As soon as you hear a rise in distortion or see the cone moving side-ways or flopping around, you probably want to turn down the volume till they're in check again.
Johan
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Got it set to 600w
Yeah I figured xmax was max cone excursion but wasn't sure if theres a calculation for both ways instead of just the max it can go out. Figured it was worth asking lol.
The rings of the subwoofer. If you look at the front of it, its suspended by 3 rings around the edge, I got the first 2 rings jumping out of the sub, I could be wrong but I think thats more then .2 inch.
Yes.. pretty much an infinite baffle driver.
I wondered if that is what he is referring to.
Only driver suspension limits outward movement and there is usually nothing to hit, it's backward movement that always limits total movement. Movement is assumed to be symmetrical(same distance in and out) for the purposes of modeling, in real life it's not always symmetrical.
So is your amp the EP4000?
I made the port that large since it gives a single center port much like a gsub. I wanted it to be from top to bottom long so it was just about playing with how wide (side to side) and deep (into the case) while keeping the 30hz. If I reduced how wide the port was then I would reduce how deep it was at the same time to keep the same 30hz tune and I didn't like having under a foot deep since I didn't want to be able to see into the cab easily, so I thought this was a happy medium haha.
"Those rings are the accordion surround, there movement are not necessarily a good indication of the Xmax (maximum linear excursion). "
Thats interesting, I mean honestly I always thought this was a good way to judge the xmax since your seeing how far the speaker comes out of the speaker basket based upon its physical limits of how far the accordion surround alows it to go without hitting the other limits of how far it can go back without bottoming out. Might be cave man but thats how I've always judged my speakers of where their "max" was to stay away from.
"As soon as you hear a rise in distortion or see the cone moving side-ways or flopping around, you probably want to turn down the volume till they're in check again."
For sure I can hear the rise in distortion if I push them harder then this (I've put them on a bigger amp and they didnt like it at all.) but I've never heard of cones moving sideways or flopping around, that sounds nutty! How would you even do that? In order for it to move sideways, wouldn't the voice coil have to come out of its slot? or are you talking about something else?
Back to the case tho... aside of reducing power what can I do about reducing xmax if I want to keep the low end? I mean having a large case with low tune increases the xmax.. so only way I can see to keep the settings and reduce xmax is reduce power. Would pEQ help in a situation like this on the spike point? Or... does it even matter if I'm cutting them at 30hz and they peak xmax on the chart at 25hz, wouldnt that mean they wouldnt be playing the lower band that would be maxing them out? Should I only be looking at the bands I am using 30hz and above for xmax then?
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Yes I'm planning on using a ep4000 to power them, from what I can see it should power two 4ohm drivers perfectly per side.
But from what I'm hearing from this convo I should be using less power to reduce xmax, so maybe I want four 8ohms per side?
Are your drivers 4 or 8 ohm?
If you select the max power display in WinISD you will see how much power the driver can take at any given frequency based on xmax. Unfortunately the only way to achieve that in the real world would be to EQ it to have drastically less output where xmax is exceded at your chosen power level and that would sound weird to say the least, so the practical solution is to just limit power across the board.
If you select the max power display in WinISD you will see how much power the driver can take at any given frequency based on xmax. Unfortunately the only way to achieve that in the real world would be to EQ it to have drastically less output where xmax is exceded at your chosen power level and that would sound weird to say the least, so the practical solution is to just limit power across the board.
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Well thats the funny thing, I know some other guys locally and between us we got a set of 8ohm and a set of 4ohm. I own a 4ohm set and he owns a 8ohm set he doesn't use that are just sitting around.
So I mean technically we could design a case for whatevers better to use, I assumed the 4ohm cuz they could take his old *** peavy 2x 600w 4ohm and was louder with that in my gsub case then the 8ohms (due to getting more power obviously) so I mean I think the 4ohms are worth using, but if the power need to be reduced to save on xmax on a more efficent case then I'm not close minded to trying the 8ohms.
As an added benefit, whatever case we make we can just toss the other drivers in to see how the same case works with twice the wattage withe the "same" drivers
Does it matter tho that the "peak" of cone excursion is at 25hz and I'm cutting at 30hz?
Would I be measuring then from 30hz up for excursion since it wouldn't be playing from 30hz and below at loud enough levels to matter at 25hz and thus wouldn't hit that xmax at 25hz? Does that sound logical here or does this spike over xmax at 25hz still matter regardless of a 30hz cut off?
Also I'm looking at the max power chart and theres nothing, like green lines, black background, no lines on it. Says 1200w across everything ? I know they are not 1200w for a fact lol. Pretty sure you'd fry them anything over 900w pretty damn fast, I feel like 600w is their true max before you get into distortion ratios and maxing/bottoming it out.
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OK so you got a PV that does 600w/ch at 4ohms and you have one 4ohm driver per channel connected? Nothing wrong with this I have my double 18 subs running the same way.. they came with 4ohm drivers for whatever reason. I have amps capable of 1000w/ch at 4ohms powering these and it works great, bass is very strong and controlled. When I bought these the previous owner was running them at 2ohms(drivers in parallel) and I don't think it sounded as good, there are pro amps that can handle that load but there aren't many that sound good doing it.
Now.. If that config works and you haven't made the drivers fart or pop with even the heaviest bass then I'd say you are getting everything these can deliver, build another G sub, load the 8ohm drivers in it and find another amp that delivers 600w/ch at 8ohms.You will have 2 essentially identical boxes getting the same power and have 6dB more output. It's always better to add more speakers and amps than to increase power into existing speakers, everything lasts longer and you get better sound overall.
Now.. If that config works and you haven't made the drivers fart or pop with even the heaviest bass then I'd say you are getting everything these can deliver, build another G sub, load the 8ohm drivers in it and find another amp that delivers 600w/ch at 8ohms.You will have 2 essentially identical boxes getting the same power and have 6dB more output. It's always better to add more speakers and amps than to increase power into existing speakers, everything lasts longer and you get better sound overall.
None of that sounds right, I'm going to have to run this through WinISD myself to see what is happening, but not tonight I'm off to bed.
Can you post a clearer pic of the driver specs, I can't read a lot of what's in the current picture.
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I'd rather run one cord to one sub instead of two cords tbh, so the ep4000 seems like a good idea to me since I could run two 4ohms in 2ohm mono to give them their rated 1200w/total for two (600w/ea). I would want to build a pair of them so the peavy won't do for that, the ep4000 however could power 2 each channel for 4 total no problem.
Problem with gsubs is that someone else already made them. Call me crazy but if I make a sub I'd like to actually say I made it or helped develop it instead of just copying someones designs and claiming credit. Plus if I like it and want to build more then 4 I can do that and avoid legal issues if that ever happens in the future. I mean I love bass, I would love to have a wall of these haha but that requires first making prototypes to come up with a design worth building more then once.
As you said about buying more amps and speakers, I don't particularly mind doing that since honestly a ep4000 is extremely cheap power and the rockville 18s are extremely cheap.. I can get four 18s AND the amp to power it for less then one 18sound driver, I mean yeah those are great drivers but I just don't have the budget to stack a wall of those for close range listening, those are more for arenas or something bigger then what I'm doing... I just need them for close range EDM 1 to 40 feet away. rockvilles and ep4000s I prob could do pretty easily I think since they are both cheap enough to stack. Wood is extremely cheap in canada too so I think I could have a case with hardware made for around or under 200c, plus drivers for 150-200c is a total of 350-400 canadian for a dual 18 cab made. Thats canadian dollars so even less then that american. Problem is just coming up with a design thats worth building, not so much the supplies or even the people to do it, I already have some friends to help me with a compressor and nail gun so we should be able to glue and nail it together pretty quickly since we all have construction and wood working backgrounds. We're not expert winisd users tho haha.
Heres their spec page:
Rockville RVP18W8 1200 Watt 18" Raw Replacement DJ PA Subwoofer 8 Ohm Sub Woofer - Rockville Audio
The spec I included was a diy member double checking their specs.
I mean alternatively if there is a different super cheap 18 out there I might be interested but $60 is extremely hard to beat and I'm not sure I'd want to randomly test some other off brand and hope they are as decent as rockville. Problem is next best thing is 150-200 from what I can see.
I mean alternatively with a ep4000 if I could find some high efficency low wattage drivers that worked good around 300w I could run four of them per channel.
I mean alternatively with a ep4000 if I could find some high efficency low wattage drivers that worked good around 300w I could run four of them per channel.
A loudspeaker has 2 excursion limits, one is called Xmax, the other Xmech.
Xmax is maximum linear excursion, beyond this point the cone moves increasingly non-linear (so not just back and forth anymore), increasing distortion while the driver looses control of the cone.
Xmech is maximum physical excursion before damage, either hitting the voice coil against the back plate (destroying itself in the process), or launching itself out of the gap on the other side, move side ways and then get stuck.
Those are just two examples of non-linear behaviour. There's other scenario's but I think you get the point. You want the driver to stay within Xmax, excursion between Xmax and Xmech is for damage control in the case of problems like a hum, feedback or low frequency sine-wave content, etc.
Basically there's tuning, chamber size and power applied. If you look at the excursion graph in WinISD you'll see there are two peaks, one below tuning that rises infinitely high, a second centred somewhere near 50 - 70 Hz. You could cut power there, for effective excursion control.
Look at Dayton Audio at Parts Express, they have a cheap 18" that doesn't ask for a very large enclosure, so it's (slightly larger Xmax) matches it's Qes/Vas better.
Johan
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