I need help with my new install. This is the first box that i have built. I have always used prefab boxes. Now i am getting a good pair of subs and i want the box right. I have a 98 S10 extended cab truck, so space is a little tight. I have been using some programs to try to figure out my dimensions. I have used winisd alpha, bass box pro v.6, and Torres. They all give different answers. I am really confused about this, and could really use some help. I am getting 2 IDMAX 12d4v4. What i have been working on is to not get port noise. The demensions that i am trying for is 46W x 17.25D x 13.5H with center slot port. Slot 12H x 3W x ?L Shooting for 4.5 cuft net volume At 30Hz tuning. The 13.5H is set in stone. Can't go much more than 46W Depth is optional, but need to keep it down low as possible. Will be pushing 2250 rms watts at a 1ohm load. Would consider using a round port, but have no idea about that. Any help would be appreciated. Thanks in advance. Any other info you need, just ask.
Hi instagater'
Do you know how to measure the (net) inner dimensions of the box? It's important that you plug in the exact same cubic footage of your box with these programs. The software will do the math, provided you're putting in consistent, accurate data. Some programs will even allow you to give the "outside" dimensions of the box and will figure out the total net inner volume... but that depends on accurate input data.
rigtec
Yes. I can figure net and gross volume. It checks out on all programs. It is the port that I am trying to figure out. I just got the new subs and the spec sheet is different than the web site. I guess I have to start over. The spec sheet say 4" x 15" port. This is for 1 sub. I have 2 subs so I will try to recalculate everything. Just trying to keep port velocity down. Anyone have experience with these subs?
Now i am lost on the whole port thing. Here is what i got. 46w x 13.5H x17.5D. This gives an internal volume of 4.635 before displacement. Subs have 0.2 cuft for both. If i try to run a 4" port at pretty much any length the programs show extremely high velocity. Trying to tune to 28-30Hz range. Can someone smarter than me point me i the right dirction please.
I'm pretty sure your t/s inputs are wrong (Re and Bl.) I'll post more info on this in my next post.
And your port is way too small.
Where did these specs come from? They look nothing like the spec sheet.
http://www.imagedynamicsusa.net/files/70537971.pdf
So... the published spec sheet for these drivers has the integrity of a career criminal. The first thing I noticed was this:
That is the LAST thing you want to see on a spec sheet. It implies laziness with keeping spec sheets up to date, or possible bad quality control, or a dozen other equally ominous possibilities.
Also, it seems like the spec sheet quotes Re as a single coil but states Bl as both coils driven in series. This is confusing. Not sure if this is the standard since I don't play with dvc drivers much but it is confusing and I had to use Hornresp to figure out what was correct. Since these are dual 4 ohm coils (Re = 3), for a single driver with coils in parallel Re should be 1.5 and Bl should be 8.32 as far as I can tell.
And the spec sheet says xmax is 39mm peak excursion. Xmax is usually specified as one way linear excursion, not peak excursion. This seems to me like they are specifying one way xlim, not xmax.
Le is not listed at all and it will be considerable. I used a small value for Le in this sim but real world Le and it's effects will have a large impact on the final product.
Having said that, even your hookup wires will have a large effect on the model since this load is .75 ohms. With impedance that low a bad connection could change these results completely and even a good connection will make the simulation somewhat invalid. I usually sim with .1 ohm added resistance for this but I forgot this time.
Considering all this, personally I would sell these drivers and move on to something with a bit more integrity. At the very least I would measure the t/s parameters before using them.
But as an intellectual exercise I completed a simulation. This is larger than what you asked for (it would turn out to be about 46 x 13.5 x 26 inches) and it still isn't really big enough IMO. It could be shrunk down a bit but the humped response around 45 hz would get worse.
Shown with 2000 watts, it takes a 12 inch (round) port to get air velocity down to 10 m/s. It doesn't necessarily HAVE to be that low but I would not exceed 27 m/s personally. So technically this port could be a bit smaller if you wanted it to be. The port length is the full length of the box (44.5 inches internally). This would be a very simple build with a full length slot port. I attached a pic at the bottom so you could see what that would look like (NOT to scale).
This shows all my user inputs (hopefully I got the specs right for all four coils in parallel) so you can check my work.
Graph 1 - response (a bit of stuffing in the right spot would smooth this right out, but it's shown unstuffed)
Graph 2 - rms excursion, you can see the 30 hz tuning
Graph 3 - air velocity, just slightly exceeding 10 m/s
There's a lot of things about this that could be changed, this is just to give you an idea.
That is the LAST thing you want to see on a spec sheet. It implies laziness with keeping spec sheets up to date, or possible bad quality control, or a dozen other equally ominous possibilities.
Also, it seems like the spec sheet quotes Re as a single coil but states Bl as both coils driven in series. This is confusing. Not sure if this is the standard since I don't play with dvc drivers much but it is confusing and I had to use Hornresp to figure out what was correct. Since these are dual 4 ohm coils (Re = 3), for a single driver with coils in parallel Re should be 1.5 and Bl should be 8.32 as far as I can tell.
And the spec sheet says xmax is 39mm peak excursion. Xmax is usually specified as one way linear excursion, not peak excursion. This seems to me like they are specifying one way xlim, not xmax.
Le is not listed at all and it will be considerable. I used a small value for Le in this sim but real world Le and it's effects will have a large impact on the final product.
Having said that, even your hookup wires will have a large effect on the model since this load is .75 ohms. With impedance that low a bad connection could change these results completely and even a good connection will make the simulation somewhat invalid. I usually sim with .1 ohm added resistance for this but I forgot this time.
Considering all this, personally I would sell these drivers and move on to something with a bit more integrity. At the very least I would measure the t/s parameters before using them.
But as an intellectual exercise I completed a simulation. This is larger than what you asked for (it would turn out to be about 46 x 13.5 x 26 inches) and it still isn't really big enough IMO. It could be shrunk down a bit but the humped response around 45 hz would get worse.
Shown with 2000 watts, it takes a 12 inch (round) port to get air velocity down to 10 m/s. It doesn't necessarily HAVE to be that low but I would not exceed 27 m/s personally. So technically this port could be a bit smaller if you wanted it to be. The port length is the full length of the box (44.5 inches internally). This would be a very simple build with a full length slot port. I attached a pic at the bottom so you could see what that would look like (NOT to scale).
This shows all my user inputs (hopefully I got the specs right for all four coils in parallel) so you can check my work.
Graph 1 - response (a bit of stuffing in the right spot would smooth this right out, but it's shown unstuffed)
Graph 2 - rms excursion, you can see the 30 hz tuning
Graph 3 - air velocity, just slightly exceeding 10 m/s
There's a lot of things about this that could be changed, this is just to give you an idea.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
well you got done faster than I did but we're about on the same page here
given your space requirements OD may be a better way to go, humor me I haven't done many of these. Akabak shows port velocity @ 4.55m/s. To view the combined driver/port output - in the "SPL Response" window go to Tools>Combined Response...>press OK .
given your space requirements OD may be a better way to go, humor me I haven't done many of these. Akabak shows port velocity @ 4.55m/s. To view the combined driver/port output - in the "SPL Response" window go to Tools>Combined Response...>press OK .
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Your t/s inputs are still wrong and I'm guessing your port is still too small. I didn't sim it to verify the ports are too small, and I won't, at least not until you are using correct t/s parameters.
Last edited:
Wow! Thanks for the input guys. It just doesn't look like ported is the way to go. The website specs are different than the spec sheet that came with them. It show IMP 2ohm Parallel/8ohm series. Re 3.0/6.0 The rest of the specs are what i listed above. Looks like i need to go with a sealed enclosure. Spec sheet recommends 1.3cuft. 10Hz/41Hz-3db/Free space for normal enclosure. This is per sub. So, i'm thinking 2.5-3cuft sealed. How much output would that lose, and how low will they play if i go this route?
k, I matched your TS data and corrected the window shots. only difference I see is the 'port' velocity went up to 6.46m/s at 47.43 Vrms in Akabak
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
It's a high q driver so sealed is usually recommended. Ported will give more output though, and as I showed it's a feasible alternative (assuming the specs are even remotely accurate).
This is clearly a problem. Which is accurate? Can you measure?
This is physically impossible. It can't be 3 ohms in parallel and 6 ohms in series.
Let's do the math. If each coil is 3 ohms it has to be 1.5 ohms in parallel and 6 ohms in series. It can't work any other way.
Are you asking for a sealed simulation now? You can do that yourself with WinISD or any other simulator. Just make sure you input the correct t/s specs.
Just be aware, this sub was never intended to have anything resembling flat response, as you can see in the manufacturer's graphs for the recommended box sizes. And high inductance will make these even more peaky than the sims shown would indicate. This sub is for getting really really loud at one frequency (or a very narrow band of frequencies) so you can win an spl competition. My sim does everything possible to get flattest response out of the smallest enclosure possible (with a port). If you WANT a hugely peaked response that's easy to do and the ported box can be made smaller. But if you want the flattest response possible a very large sealed box is the way to go.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.