IDMAX 12v4 box help.

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well his amp does not state 0.75 ohm stable, in my experience most people don't sim at the driver RE

Hornresp help doesn't say much about this issue but WinISD help does. This is a direct quote about how WinISD calculates voltage from the "power" (in watts) input from WinISD help (bold provided by me).

"Term "power" should more correctly be voltage. This term "power" comes from definition by Richard Small, who defined the input power to be P=Eg²/Re (this is to simplify things, because impedance varies greatly depending on the frequency and the box), where Eg is RMS output voltage of your amplifier, and Re is DC resistance of voice coil."

My resources say if you are not using driver Re (dcr) to calculate Eg you are doing it wrong.

If the amp can't handle this load it will fail and/or burn but the amp impedance stability rating has nothing to do with the Eg input in Hornresp.

As I mentioned before there should probably be a bit of series resistance added to these sims to account for real world wiring and connection impedance considerations and that WOULD change things but as far as I can tell you didn't add any series resistance to your script so that point is moot.

I did post the Akabak script, you are more than welcome to change it :D

I'm not interested in changing your script but as long as continue posting mistakes in a thread I am actively involved in, I am going to continue to point them out. Sorry to be so blunt but inaccurate sims don't help anyone, they just confuse the issues and lead to unexpected surprises in the measurements of the finished product.
 
I'm just gonna say fine... most people just go by driver rating ie: 4, 8, 16 ohm etc. if you want to get that specific go for it, in the end it could make a tiny difference in the 'sim' result (1.25dB @50Hz in this sim instance). why not add the resistance of the wire he is using and the resistance of the amp termination points etc. these results are also halfspace which is not 'in-car' response. real world results also vary by altitude (barometric pressure) and ambient temperature etc. this is not enough to fight or cry over

I'm done with this, I don't enjoy bickering with you or anyone else it is not what this place is for
 
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I'm just gonna say fine... most people just go by driver rating ie: 4, 8, 16 ohm etc. if you want to get that specific go for it, in the end it could make a tiny difference in the 'sim' result (1.25dB @50Hz in this sim instance).

An "8 ohm" rated driver can have a dcr of anywhere from 4.1 to 8 ohms. This can make a large difference in the sim if Eg is input based on nominal rating, not just in spl but also in excursion and velocity. In this case it amounts to a full 1/3 too much power.

why not add the resistance of the wire he is using and the resistance of the amp termination points etc.

I already mentioned 2 or 3 times that this should be done. It can make a huge difference when the load is under 1 ohm.

these results are also halfspace which is not 'in-car' response.

There's ways to deal with that, but you can't do anything about it in a program that only sims 2 pi. A simulator can't be expected to do everything but the user can and should understand and adapt to it's limitations.

real world results also vary by altitude (barometric pressure) and ambient temperature etc. this is not enough to fight or cry over

If the sub is going to be used on a mountaintop barometric pressure absolutely should be addressed. There's not much you can do about temperature though, it's going to fluctuate in a car.

I'm done with this, I don't enjoy bickering with you or anyone else it is not what this place is for

It sounds like you are arguing that accuracy is not important. In case it's not clear by now I strongly disagree. Errors and oversights accumulate and at some point the sim isn't going to resemble reality at all.
 
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Just to follow up. I ended up building a box similar to the one you suggested. I just used a straight port. 3.5 x 12 x 30. Ended up with 3.59ft net volume. Tuned to 30Hz. My port velocity was right around 100 ft/sec at the highest. So far i have not had any port noise at all. These IDMAX have to break in though. When i first installed them, i thought i had made a huge mistake. They sounded horrible! After a few days of low volume, they started loosening up. Still not all the way broke in, but they do sound awesome now. I have cranked them a time or two. Wow! is all i can say. Thanks again for all of the help.
 
Just to follow up. I ended up building a box similar to the one you suggested. I just used a straight port. 3.5 x 12 x 30. Ended up with 3.59ft net volume. Tuned to 30Hz. My port velocity was right around 100 ft/sec at the highest. So far i have not had any port noise at all. These IDMAX have to break in though. When i first installed them, i thought i had made a huge mistake. They sounded horrible! After a few days of low volume, they started loosening up. Still not all the way broke in, but they do sound awesome now. I have cranked them a time or two. Wow! is all i can say. Thanks again for all of the help.

I hope you used a lot of bracing in that box. Those will be some sizable panels for that much acoustic energy.

Clearly TundraLTD and I don't agree on a few things but his flared port idea was a good one, it would have been good to try something like that. 30 m/s is a bit high and if you hit it with a full power sine wave at Fb or below it will be a minor miracle if you don't hear port noise.

"Flare It" shows your core velocity is fine but predicts port noise starting at 15 m/s @ 30 hz (and 10 m/s @ 20 hz) for your 42 sq inch port.

An externally hosted image should be here but it was not working when we last tested it.


TundraLTD's flared port idea would have brought that blue line up higher. But as long as you are happy with it, that's all that matters. And I'm sure whatever you came up with is a lot better than the manufacturer's recommended box.
 
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I rounded the edges of the port on both ends. These aren't fully broke in, so i haven't been pushing them hard yet. I am not 100% sure what port noise(chuffing) sounds like. I have been reading up on it, but seems like it is hard to describe. I may have it and just not know it. I may try to build another box like TundraLTD modeled for me just to see if there is a difference. I have the subs facing upward, with the port at the bottom of the box. The port faces the third door. There is about 4" clearance around the port. These subs are starting to hit harder every day. I guess it is possible that they are not pushing enough air yet to cause port noise. Is there a sure waay to check for port noise, or is it something you just have to have an ear for?
 
Is there a sure waay to check for port noise, or is it something you just have to have an ear for?

Hit it with a full power sine wave at tuning or slightly below tuning and if there's chuffing you will hear it. You can't miss it, it's an obnoxious noise.

Chuffing can be masked somewhat by the music that's being played and by placing the port out of your line of sight and some people like to play these tricks instead of properly sizing their ports. But I don't like to try to mask chuffing because turbulence (even before it's audible as chuffing) causes distortion and robs spl. This is why I told you to read up on port compression back in post #30.

I rounded the edges of the port on both ends.

Every little bit helps but realistically a 1/2 inch roundover isn't going to do much of anything.
 
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