Sub Cross Over Help

Need a little help from you guys running subs. Let me start off with what I have. Power amp, Krel FPB400 CX, KCT pre amp, Bryston CD player, B&W 804s's with a Rel R328 sub. I've been doing a lot of research and reading and learned a great deal from you guys on this site. As of right now I have the sub crossed over at 40hz. The sub is next to the left speaker 18 inches from the corner and 8 inches from the back wall. The speakers are 10 ft apart and a fot from the back wall with my 55 inch plasma TV in the center. My listening distance is 10 ft from the speakers and the room size is 17 x 14. I've used a RTA with a 40hz tone to match the sub with my full range speakers. Everything seems to sound extremely well. The imaging and sound stage is superb. Only thing I've noticed depending on the music I play. I sometimes have to turn down the gain on the sub by 5 clicks, which I'm sure is normal. The gain on the sub sits at 16 clicks from zero. Let me know what you guys think and what I can do to improve my system if any. Please let me know.
You can have good clean tight bass and if it is crossovered too high you will lose some clarity in the lower midrange. If I was you I would try to reposition my sub a little further away from the corner and back wall. I would also try lowering the crossover point and gain. Theres a lot of work involved to get the right position for a sub. If you work hard at it and have a lot patience good things will happen. When you think you have the crossover point right play some vocals and make sure the bass is not coming into the midrange. Good Luck
I did reposition the sup and It sounds the best in the corner with good bass. I can go a little lower with the X over.
Sub position and EQ are the most effective tools but both require the ability to measure performance. (See RoomEQ Wizard, Omnimic, XTZ, etc.) Doing this simply "by ear" with program material is very difficult and fraught with opportunity for error. Also, despite REL recommendations, having an appropriate high-pass filter for the main speakers is very useful.

If you have your crossover point and gain set correctly, you are dealing with room interaction and turning down your gain is not fixing that interaction. It sounds like that you clearly enjoy the boundry boost, but that boost becomes overbearing on some music that have an extra kick at those frequencies. I can only recommend 2 things.... Move the sub out a foot or so at a time and see if the boundry interactions subside and/or if you have a phase dial, change your phasing a bit... that can easily make an acceptable change. Good Luck, Tim
1. You can't use a single tone to match levels because of its interactions with room modes that make some frequencies significantly louder or quieter than others depending on location (even 6" can make a huge difference).

You want to use pink noise containing bass frequencies with the same bandwidth within main speaker and sub-woofer pass bands (for example 1 octave from 60-120Hz) and match the level between a speaker and the sub-woofer with one channel input or both together (the pink noise must be in-phase).

2. RELs are relatively simple to use well with the sealed stand mounted monitors favored by audiophiles. Sealed enclosures have a second order roll-off which will sum-flat with the REL's second order low-pass and excursion remains constant below their pass-band so IM distortion is less of an issue. With a 60-80 Hz F3 point placing them so the SBIR null is outside their pass-band is also easy.

That's not your situation and using the REL's built-in cross-over instead of a separate sub-woofer controller with a higher cross-over point and high-pass filter on the mains (ideally iwth an independent frequency adjustment) is sub-optimal. You're doing nothing to reduce IM distortion inducing excursion in the speaker which will increase to what it would be without an enclosure and are going to have issues getting flat response matching the speaker's 4th order high-pass response with polarity inversion in the port's pass-band with the sub-woofer's low-pass.

Part of your bass problem is a big notch at 200-300Hz which results from the main speaker's SBIR null and nothing you do in the last octave is going to fix that (you need to bring the speakers farther out; preferably with 4-5' from their front baffle to the wall which will put the SBIR null at 70Hz or below and out of their pass-band with an 80Hz sub-woofer cross-over). Other issues are coming from how the speakers are coupling to the room modes which can be worked around by getting those frequencies out of the speakers and into the sub-woofer which doesn't need to be placed where you get the best high frequency performance.
Thanks guys for your help on this. Timlub It the nail on the head. I did move the sub out of the corner witch did help. I dont have so much Bondry boost like I did. The X over is at 35hz. The only thing I notice is when I play hard rock like Rush Then I go to play something like Yellow or something that has a lot of low Bass in It. I will have to turn down the gain a little. I'm still playing with things to see If I can get better. I'm trying to get the sub to play good bass at the right gain. No matter what disc I play. Something tells me this is very hard to accomplish. As it stands right now the sub blends in extremely well with my 804's. Much better then it did before when the sub was in the corner. Any other advise would be helpful. Thanks

The fact that when you changed your subs location and it helped, you may want to try this for sub location. This is how I placed my subs.
Pick some music with lots of bass or the Yellow album you were talking about. Set your systems volume at the level you like to listen at. Turn your system off and put your sub where you normally sit. Disconnect your main speakers and turn your system back on. Get on your hands and knees, crawl around the room until you find the location where the bass sounds the best to you. Put your sub in that location and reconnect your main speaker, then listen. You still may have to make adjustments but the bass should be more uniformed.
You do need an SPL meter to get the volume correct at all speakers to start as Kal said.
I myself do not like subsonic bass when I listen to 2 channel music so I have a crossover to deal with the differences in bass between 2 channel and movie surround sound.
Glad to see it worked for you. I have a similar situation and also have 804S and Rel sub (but a Storm III). I suggest looking into what Kal (Kr4) mentioned briefly: "having an appropriate high-pass filter for the main speakers is very useful". I know I am, and I'm also looking into DSPeaker 8033.

Kal: which high-pass filter would you recommend? The "less components in the chain, the better" credo kind of draws me away from adding a filter, but clearly you must have found something good.
If u have to turn down the gain then the sub is too loud to begin with...a common problem...most people turn up the sub until they can hear it which by then it loses its omnidirectional capabilities...if u can locate where the sub is then its too loud...u can spl match if needed...but I tend to calibrate a few decimals lower for optimum match...hope this helps