bkolfo4

I would assume the dimensions he gave are the overall box size, so after sub and port displacement I doubt he is going to have 4.75 cuft. OP - can you make that box any larger? I did a very quick calculation (on my phone) and came up with a 17.25 x 3 port x 29" long. Drops you to somewhere around 3.7 cuft tuned to ~32 Hz.

Sale pending on all three. . .

Some one has to need some 10's, and I need money to rebuild a motor!!! PM me reasonable offers with your zip code - I need to get rid of these!!!

New lower prices.

That amp would be a little much for it, but nothing wrong with some headroom. Just buy 2 of them. I would knock off $35 if you picked it up and paid cash.

These are new in the box. One of them was hooked up for abot 15 minutes last week for the test I ran on using mutliple sub sizes/brands together. The other two have never been opened. $195 for 1 $370 for 2 $525 for 3 Prices include shipping. No trades - I need cash. They are Dual 2 ohm subs.

It does not have to be quite that big if you want to do around 160 sqin and drop the tuning to down around 34 Hz.

Two quick things to learn: Port area is not related to box volume. It is related to air velocity through the port which comes from cone area x excursion and tuning frequency. The idea of large port area is only for SPL is not correct. I think people have come to this conclusion based on large, short ports that are tuned to higher frequencies in SPL setups. In reality, ports are usually too small in car audio boxes due to the smaller sizes and the very long ports that would be required to get the desired tuning.

160 sqin is enough port, but as long as it is tuned correctly, 180 is not going to be bad. Brian

This is wrong. (3) 4 ohm drivers in parallel is 1.33 ohms Edit - but now I see they are dual 4, so that would be: "Each sub series up to 8, then all three parallel down to 2.67 ohms"

X2!!!!!!

When you start talking different frequencies, then it is more like a 3 way or 4 way setup. No issue there, except you want to get drivers that have the right parameters to play in the range that you want them to. I would not buy an 18" for low bass, and then a 12" of the same sub for midbass. . .

I see what you are saying. Two 10's vs. one 10 and one 12" - what is the difference I was mainly just going for the different brand, different size has a negative effect theory. I have several chaos 10's and 3 other brands of 10's, along with 2 different 12's. Maybe next time I am building a box, I will throw together a quick test box. Brian

I only had the ability to run the test with these subs without building something. Did not feel like building anything. I see the 'issue' being discussed with different size subs and with different brands. I though two different size subs that were also different brands would kill two birds with one stone. . .

So I keep seeing people post on here that using 2 different size subs, or two different brands will not work. . . The reasoning is normally "you will get cancelations". I have run multiple sub sizes before with good results, and I really don't see why 2 different subs playing the same frequency are going to cancel each other. I see that as 2 sources added together. If multiple people in a choir sing the same note, doesn't it get louder? Their voices are not exactly the same. To be clear - I am not saying this is my favorite thing to do!!!! There really is no reason for it. I have customers call all the time wanting to buy (2) 10" and (1) 18" because "They want to get the lows and the highs". I have to explain that the size of the sub is not always going to determine how low it will play. There are 10's that play low, and there are 18's that don't. Box design and driver parameters will decide how it will perform. So, today I did a little experiment. (1) 10" Chaos and (1) 12" MTX shallow mount, and an AQ2200D. To perform the test: I ran three conditions - just the 10", then just the 12", then both. I maintained the same voltage on the speaker output of the amp for all 3 conditions (used 50 Hz to measure to output voltage) I measured output from 30 to 50 Hz in 2 Hz increments. The 10" was in .6 cuft sealed without stuffing, the 12" was in .7 cuft sealed with 12 oz of polyfill. The results: Freq (Hz) 10" Chaos 12" MTX Both 30 90 95 96 32 95 96 97 34 95 96 97 36 95 96 97 38 95 96 97 40 95 96 97 42 95 96 97 44 95 96 97 46 95 96 97 48 95 96 97 50 95 96 97 I also played several songs that I am very familiar with in my truck on the MTX 12". I played these songs with both the 10" and the 12" playing together. While it was not much louder, there definitely were no issues. Bass was clean and strong. No missing notes, etc. I also want to point out - You can always have issues with cancellations, but you can have those issues with 2 of the same sub. Having the subs as close together as possible and facing the same direction will normally minimize or eliminate the issue. I know some people are not going to like this, but I think a lot of people just jump to conclusions because it is what they have read or heard. What's new. . . Brian

If you have 17 cuft before sub and bracing displacement, I assume that is around 16 cuft net volume? I hope that 17 cuft already has the port displacement accounted for. A port big enough for 4 18's tuned to 25 Hz will have a big displacement from your box volume.

Please tell me why he cannot. . .

I ran 4 15" BTLs in 11.7 cuft with 386 sqin of port tuned to 34 Hz. 155+ playing music down to 30 Hz. 157 peak from 37 to 43 Hz. Designed to play music and played music like crazy. . . http://s183.photobucket.com/albums/x24/bkolfo4/?action=view&current=MVI_0950.mp4

I always love this example. If the boxes are the same NET volume, and the tuning is the same, the change seen in output and peaks is caused by an undersized port not operating correctly. There is not something magical that causes large CORRECTLY designed ports to have a different F3 and peak.

I would really like to hear your thoughts about this if you have a min...pm me if you want I have posted it many times as have many other people. Port size is related to the Vd of the driver and the tuning frequency (actually air velocity through the port). The amount of power can also come into play, but is hard to factor in without modeling the enclosure, since large enclosures allow for more driver excursion with less power. I guess some people could argue that the driver will have less excursion in a smaller box, so less port area would be required, but that is the same situation as going by how much power will be used. Unless you know it is a situation where the driver will be limited from using its full range of excursion, the port should not be undersized based on box volume or power applied. I always ask people this question: If I have some cheapo 18" driver with low excursion capabilities on 100 watts in 6 cuft tuned to 32 Hz, why would it need the same amount of port area as an 18" high excurision driver on thousands of watts in the same 6 cuft tuned to 32 Hz. And I am not saying it can't, it just does not need it.

Maybe you are the one who did not pay attention. If you would read, you would learn that the .65 is the DC resistance, not the impedance. Those two specs are published on the Fi website - DC resistance and nominal impedance. He was confused thinking the amp would see .65 per coil, but it will not unless it outputs DC current. Either way - your stating that dual 2 ohm coils wired in parallel to the amp will be .6-.7 ohms is wrong. Once again, that is the DC resistance, not the AC impedance when an AC signal is applied.

Wrong. Where are you coming up with this??? I doubt you have ever seen a dual 1 ohm sub playing music at 1/3 ohm, or a dual 2 playing at .6-.7

OP - why did you bump the thread? Joe X provided you with the correct answer. The sub is dual 1 ohm.

300in2 for a 12ft3 ported section is 25in2 per 1ft3 300 sqin is not too much port area for a pair of 18's. When will people stop worrying about box size vs. port area????!!!!!

Xmax is how far it can move within it's electromechanical limits (I think that's the right term?) - when the voice coil runs out of steam per se You were thinking of Xmech If you want to be really technical, you have the electro and mechanical limits. Xmax is the smaller of the two.