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3 4" Aeroports with only one causing strong resonance at certain frequencies when played very loud

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Hey man, the first thing I would do is verify your tuning frequency, its probably fine but weird things happen sometimes.  The best way to do this is to get a sine wave generator app, play a sine wave tone at moderate volume and watch/feel cone movement, you are looking for the frequency where cone movement is the least, that will be the tuning frequency.  

Decreasing box volume generally does improve sound quality, but it usually isn't a huge change.  Going from 5 cu ft down to 4.4 probably isn't going to be enough change to really make a difference.  I would go down to 4 cu ft or even less.  Any reduction is box volume is going to reduce output around the tuning frequency as well, but that's the price you pay.  

"Nothing prevents people from knowing the truth more than the belief they already know it."
"Making bass is easy, making music is the hard part."


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hmmm ok, yeah im not really worried about tuning because the tuning reminded me straight away of where I had the type r's and i fiddled with that for so long and decided i would want to go up or down. I dont think I would change it no matter where it end up being as i like the tuning exactly there for the type x and type r's, I dont like the response on either side of that tuning for them.

Im thinking that a reduction in box size might be it, just the sound sometimes makes me think they are trying a bit too hard in that box. Just sounds like its dying to tighten up a little, especially up loud but its weird I notice with lower volumes the sound blending I get a crisper, cleaner sound with the type r's even though the overall SQ is alot less. With the type x's I get alot better SQ overall and bass wise but the bass and overall sound is more murky.

I have mid-tier DDLinier Tweeters and Crossovers and VERY old school "Highly Praised" Polk's for Mids up front with a set of those gold DB Polks coax's with a cap upgrade in the back all running of a MRV-F345 V12 amp and the sound is pretty damn decent especially coming out of that Alpine W900E head deck.

My theory is I think that the type x's are getting pushed to their "extra low low" limits by that box being forced to go even a bit lower than they probably would like to and I just need to tighten its size up to even a 4.5-4.6 and they would be much happier. I get what your saying though to reduce the size would probably only be a small improvement, I wonder if I did make another box to say 4.5 would I lose much lows or basically none? Thats really the deal-breaker for me I guess, another box would not be hard to make but ill try to avoid it if it is a better decision.

Its disappointing I was under the impression that the Type X 12 was like a happy 2nd place for SQ guys to JL W6 12's and then like they were saying Fi Q was about the same SQ as Type X but it was a cheaper made sub. So being that the type x got louder than W6's and was easier to source I just went with them, only to realize now that I want 2 x IDMAX 12's. When I was hearing all this about the top SQ subs I kinda assumed that the Image Dynamic subs must have fell below this rank of those 3, so I didnt bother looking at that them. But now I realize IDMAX is better sounding, lower and louder than JL W6 and Fi Neo so thats what I will get once I get the $2,200AUD up to buy them. I would have never found a set of them second hand around here anyways and i got both type x's for under 800 (brand new btw) so I guess I cant complain really, I just thought they would sound a bit better.

Could I ask a recommendation for an Aeroport box size for 2 x IDMAX 12's running at 1k each, hitting very low and loud please?

I have to make this Type X situation work for the interim though. 


*edit: Fi Q/ Neo is louder and probably lower than IDMAX but IDMAX's SQ is way better and will definitely get loud enough for me so it totally wins over the Fi Neo option for me with it sounding much better and all and gets plenty loud.

Edited by DAN831111
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do you reckon 4.2 for the type x's would tidy up the sound alot? would I lose ALOT of the lows like how dramatic would the loss in lows be going from 5.0 to to 4.2 assuming i keep the aeroports tuned to the same tuning roughly?


also what would be a perfect size aeroport box for 2 x IDMAX 12's to shine at their best low and loud in your opinion? they would be running off the alpine amps 1k each.


*edit: btw current box worked out to be 4.45 cubes after recalculation of displacements, also would 2 x 4" aeroports be ok for the dual type x subs AND dual idmax or will 3 x 4" aeroports be better suited? Is there any way to add mdf inside my current box to reduce volume temporarily so I can remove it if I dont like it?


Ok so scrap all of that the type x has a MUCH bigger displacement than type r even though they look roughly same size and shape, so my box is 5.02314 cu ft. Net, the ports are 16.11" which works out as 0.148 displacement for them each and type x 12 is 0.194 displacement so say 0.184 with my double baffle. All comes down to 4.21114 cu ft.

Ok so I now see I cant really improve on box size for the type x 12's to achieve really anything!

Oh well...

On the plus side I guess my current box will be about perfect for a set of IDMAX 12's 😀, all I have to do is order and then install as their amps are ready too.

My guess is once you get the lows coming from the type x in a ported situation vs a type r (less lows) it adds a muddyness? reduce lows = cleaner sound?


Any opinions or advice is appreciated.


They still sound heaps better and cleaner than the type r's, just seem to have a muddying affect on the rest of my speakers and overall SQ worse than the type r's did. weird. must be the added lows i reckon?? IDMAX will have cleaner lows for sure... hopefully their lows are as strong as the type x's (pls advise the anwser anybody who know this)





*edit again:

Subsonic filter was on 15hz 12db, where I have it normally set for these amps, now turned to "Off". Muddyness has gone 😀 Overall SQ goes up through the roof 😃 Bass suffers slightly but has more impact but is a bit headachey 😏 upon listening to it again later have totally gotten used to the bass, it sounds clearer, punchier and much better, no headache at all 🤣 Overall SQ and Bass SQ VERY good 👍

Edited by DAN831111
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