Okay why does the 300 have a bigger woofer but cost less and then why does the 400 have a smaller woofer but the box isn't ported in the front and it cost more? Is that cost just to add the crossover function on the sub?
Why isn't it ported?
And before you ask I can't afford the 500 model.
For me that is way to much money to spend on a subwoofer.

Thanks

The 400 has a fancy computer controlled amplifier and it won't distort if you try to play it too loud.

The main reason for the cost difference despite the size difference is that the EP400 employs DSP processing which gives the designer much greater control and performance advantages. Basically if you add the DSP to the EP350 you have an EP500.

If you are looking for extension and have a small/medium size room swing for the EP400. The EP350 will likely be able to provide more output across its frequency range for larger rooms.

I wouldn't even say medium rooms. Axiom promotes it for small room only.

For the large majority of situations, the 350 would be the better choice. The 400 is something of a special-use product.

I would use the 350, unless you have a very small room. I'm very happy with mine.

Sealed subs often times sound better than ported subs, seals subs also require more power than ported as well, this is due to the driver compressing the air inside of a sealed box.. In a ported design the air is allowed to escape reducing the power needed...

Probably one of the biggest advantages of sealed subs is that it eliminates port noise all together at high output. Port noise can sound like "flapping" or "farting".

I also believe the EP350 has a 350 watt amp, whereas the EP500 has a 500 watt amp. (Not mentioned in the comparison above)

Cat, i am almost positive the naming scheme (the number) among the subs is how much power they have.

Not quite but close the Ep400 has the same 500W amp as te Ep500 but the DSP is a little different for the smaller enclosure/driver. The EP350 is 300W, so there are some minor differences.

I wonder if I could upgrade my 350 to a 500 by replacing just the speaker and the amp? I doubt if it's that easy, but it sure would be nice not to have to replace the cost of the cabinet too. I'm assuming there is some difference in the speakers between the 2.

The cabinet's somewhat different, since the 350 amp is much smaller than the 500. So at least the plastic boot would have to be changed.

Sorry about the title I mean to say 350-400..
As for me I was looking at the 350, for somebody that is not to knowledgeable I thought it would enough for me, and I can just set the crossover setting with the Yamaha..
As for placement I had this problem with my last Polk sub was that it was next to my left front tower and never really heard it all that well except when I got up to leave the room all of a sudden there was "sub".
So for this one I was thinking about to the right of my sitting position about 6 feet away in the corner.

Thanks

you will have to experiment with sub placement, all rooms are different. I would recomment the "crawl" test. Place the sub in the location where you will be sitting, put on some good low bass tracks, crawl around the perimeter of the room and listen for the best overall location where it is not to BOOOOMY or One Note Bass sounding, then just switch the sub and you back to the seat.

What you are describing with your present sub is room modes - peaks and dips in the response. Basically the sub wasn't placed in the optimal spot for your listening position and you were sitting in a "null". This is all fixable.

So when your waiting for your new subwoofer, google the terms "subwoofer crawl" in the search engine and read about it. This will help you in providing the best placement and extracting the best performance of your new investment.

Yeah have read all about the "sub crawl" but physically not able to do which is also why I can't go out and "audition" speakers and have to rely on online user info and reviews.
As for placement I think in that corner is going to be best if it were up front it would be a good 14 feet away from me.

Thanks

a couple of things that can work quite well if you can't do the sub crawl and you don't want to sit in a null;

put the sub something like one third off the side wall at the front, and just a few inches away from the front wall. you should see an illustration of this if you check at the address below this message. i had to do this, and not the sub crawl, as i could not move the sub easily enough; my sub's frequency resp. is very flat and i cannot detect the changeover from front speakers to the sub. the integration is excellent.

next, have your LP (your ears) at around 38% (of the length of the room) from the back wall; or if you have a large room: from the front wall.

when done, carefully run your Audyssey or MCACC or whatever calibration program you have.

My observations on the EP350 vs 400 based on listning to both at Axiom.

The EP400 has more output than the 350. In Axiom's listening room, the EP400 was still overpowering at its 1/4 setting on the volume dial vs the EP350 sounding good at 1/2. Since the two were on the same channel, the voltage out of the receiver was the same. That room was 12'x20'x8' (1,920 cf)

According to the specs it also plays lower with a -3db point of 18Hz, vs 28 for the EP350. You will notice the difference in movies like Terminator3, Transformers etc. where there is a lot of LFE.

I see from the tech specs, the 350 may have a -3db point of 18Hz. Based on my experience in my concrete slab appartment I would say that is the absolute best case. My 350 is flat to 21Hz and then output falls off steeply, so I may hit that point, but I have no low frequency loss through my walls (concrete does not flex).

or, you could buy 4 subs... and have the best of all worlds.

http://www.youtube.com/watch?v=ayOXz26qm3I

My experience in my home was different than yours. The little EP400 couldn't give me any shake or feel while watching movies and the EP350 easily did the job. I have always thought of the EP400 as a music only sub or one for very small rooms.

Fred, what you describe wouldn't necessarily indicate that the 400 has more output. It could be simply that the level control on the 400 "opens up" more quickly than the one on the 350. The result would be that the voltage output from the receiver that was let in to the sub amp would be equal or more at 1/4 to what the 350 level control let in at 1/2.

good point John. I never thought of that.