Axiom Home Page Forums General Discussion Advice from Axiom Owners Crossover on the EP subs.

Since my impressions with music(portions of The Planets)were as given in my previous reply here, I decided to check frequencies more precisely, by using a test-tone disc rather than music. First, the very sharp cutoff above 100Hz, regardless of whether the sub crossover was set to bypass(which ordinarily on a sub would permit frequencies above 100Hz to be heard), was confirmed as being present(this was with the receiver crossover set to 200Hz, so as to not affect the result).

Then, with my usual 80Hz crossover set on the receiver(with the M22s set "Small", of course)the difference between the bypass setting and setting the crossover on the sub itself to 80Hz was that an 89Hz tone, for example, was significantly weaker with the 80Hz setting. This was as expected, since the combination of the 80Hz rolloff done on the sub by the receiver(24dB/octave)and the sharper cut made by the sub itself made the net M22/EP500 response weaker in that area than it was with the receiver crossover alone in effect.

So, as was said before, I didn't observe any benefit from the sharper sub cutoff. I'd imagine that if there was a room resonance in the 90Hz area that the weaker sub response would aggravate it less.

sirquack

I do have my M80s set to small but I have the x-over in the processor set to 40 Hz for the front channel.

Good morning, Ian.

Good Morning JohnK. It gets a bit fuzzy at 3:50am; is it a late Friday night or an early Saturday morning.

To pick up on my earlier point about room response and its relevance to this issue, you can see the difference between an 80Hz and 40Hz receiver cross-over for my room right here. The blue trace is with a x-over of 40Hz while the red is 80Hz. You can see that the 80Hz setting has pulled up two nulls at around 78Hz and 90Hz. I've used a 40Hz setting for music because it sounds less "boomy" but after running the 80Hz test, I think the boominess is a result of having my LFE gain turned up too high( Yes Randy...still too high ). I haven't quite figured out yet why these two nulls are ocurring in my room. Other nulls are ocurring due to comb filtering as a result of a wall located about 10 feet behind my listening position.

I'm bound and determined to smooth out my room response without using "artificial" sound treatment .

Mojo,

The way to solve this room thing is to add a second sub-woofer; hence the 3rd one going into my room. Four is sort of magic number to eliminate all of the room affects in even the most difficult rooms.

Just out of curiosity, I know you can use a Y adapter for two subs, but how would you hook up four?

Hi Ian,

I've tried a second sub in three different locations, with various cross-overs (on the receiver and sub), gains and phases. The results were disappointing and I have the graphs to prove it . With some configurations I had cancellations resulting in dips where none existed before and with other configurations, there was no practical difference.

The second sub used was my old 150W RMS Sony that has a -3dB point at 28Hz. I'd be more than willing to experiment with three more EP600s if you'd care to share .

I also mapped my room response with the three doors shown below opened. The result was a new big dip below 100 Hz and no practical difference between 100Hz and 300 Hz.



BTW, I am now very happy with my room response below 100Hz. The 80Hz setting in my Denon fixed that. Above 100 Hz, my room response with 2.1 (blue trace) still needs work but with multi-channel (red trace), it's acceptable. BTW, the red trace has a Denon cut-off of 80Hz while the blue trace has a cut-off of 40Hz. The 80 Hz cut-off has eliminated the dips at 75Hz and 90Hz and the multi-channel has almost eliminated the 25Hz band-width comb-filtering as a result of the back wall. As I said before, I am very determined to correct this room without artificial treatments.