Improving bass response

I would like to improve the bass extension in my system. My current system includes Arcam Diva 92 > HT Pro Silway Mk II > Classe CAP-150 > Synergistic Research Sig. 2 > Sonus Faber Concerto speakers. Power cords are stock.

I know the SF monitors cannot reproduce extremely low bass. I have moved them around and believe they are optimally arranged, given the confines of the room. The room measures 15x25 feet and the speakers fire across the width of the room. They are 7 feet apart, several feet off the side walls on both sides and 2 feet away from the front wall. The sitting position is almost against the back wall and is not easily changed.

I want to avoid simply adding a sub-woofer. I have tried a Rel Strata and despite integrating fairly well, I can still hear a disconnect ie. the sound is not seamless.

I'm willing to change anything else except the Arcam which I like and intend to keep until the format wars end. I also like the speakers with the exception of the low end. Should I:

- try upgrading power cords
- change speakers (Grand Pianos or other suggestions)
- change integrated amp to separates with an amp that doubles down into 4 ohms and has better bass extension (the CAP-150 is 150W into 8 ohms and 225W into 4 ohms)
- or anything else?

Any help is appreciated.
Thanks, Dave
Power line conditioning will definitely help. Maybe a lot. I like Tice, but there are several good ones out there. Power cords can also help bass response, but not as dramatically, in my experience. I would try a Tice Solo on the front end and a JPS Labs Power AC on the Classe, straight to the wall. You might also try the HC version of the Solo and run the amp through it, too. On smaller amps, a good PLC can be an improvement overall, especially in extension and blackness, even if you lose a bit of dynamics. The Concertinos are really nice; very coherent, like a good 2 way should be, so I'm not surprised that you didn't like the sub.
Where is/was the REL Stratus positioned? If you want to overlap the cut-off between the sub and the speakers, move the sub away from the corner towards the middle wall somewhere.

Also were you trying to integrate the sub by changing the cut-off frequency? This would seem logically to be the best way to do it, but it is not. It is much better to choose a frequency well below the lowest frequency of your speakers and turn the volume on the REL up slowly until it integrates. My Storm III is set at 38hz. My speakers are rated to 43hz. Many people use a wider gap, but my speakers are on the polite side in the bass. (A Storm III also goes deeper than a Stratus.)

I found a big improvement in the bass response with the Blue Circle BC62 power cords. They are on sale now for $125 on this site from Hello Simply Music. Well worth getting.

Have you also tried moving the speakers closer to the wall or corner?

Thanks for the responses. It looks like power cords are worth auditioning.

Sugarbrie, FYI the Rel was in a corner and I didn't have a lot of flexibility regarding placement (thanks to doors, piano, etc in the room). I did try changing the frequency cut-off and left a gap between the sub and the low frequency extension of the monitors but it didn't help. Who knows? Maybe the issue was more in my head than with the equipment.

Regarding speaker placement, I can't move the speakers closer to the side walls due to doors in both directions. Are you also referring to placing the speakers closer to the front wall as well?

Thanks for your help and look forward to any additional comments.
I was able to get a completely seamless transition. It didn't happen until the sub was completely broken in and it didn't happen until I got the setup right. Took me a couple weeks of adjusting. Once I got it, it was like the Concertos were different speakers. They still had much of their original characteristics, but the sense of ambience and power was greatly improved. Soundstage reality and dynamics were greatly increased as well. Best $1100 I have ever spent on audio. Well, then I ended up selling my Concertos and upgrading to the Sapphrie III LEs, but that is another story. Try it, you'll love it!
Oh I forgot; If you still have the REL, a better power cord for it replacing of the stock cord really smooths out the low bass response (less boomy for a REL, which is not boomy compared to other subs). At least 6 feet long. Maybe then it will integrate well.
I found the following upgrades to my system improved the bass:
1. Nordost quattro-fil cables (from spm)
2. Spiking the speakers.
3. The addition of a sony scd-1. This had an amazing impact.
4. Powerful amps (duh).

Of course you can give up some imaging and get more bass by moving your speakers back. You can also get one of those computerized room analyzers. Those will help you position your speakers for optimal bass response.
With a given room and given speaker/listener positioning, the thing that most effects the bass response is the speakers. By far. Next would be amplification. Then preamp. In some systems the speaker cabling makes a significant difference as well. Power cords make a difference in areas that relate somewhat to the bass, such as bloom and dynamics, but I don't think they can solve your problem. My advice, free and worth every penny.
Your most cost effective solution: power cords. You have some nice equipment. I own both the Blue Circle BC62 mentioned above and the Cardas Golden. The BC 62 at $125 is a steal, very neutral across the board and much, much better if you float the ground. The Cardas Golden, available used if your patient around $200 is, in my opinion even better (I use it at the front end of my system, feeding both my CD/DVD player and my line conditioner; my integrated amp which is plugged directly into the wall utilizes the BC 62, which I have been happy to live with, unlike the other 6 or 7 cords I experimented with before settling on it-I would like to buy a 3rd Cardas for that, but can't really swing it $$ wise right now) with tremendous bass extension, although not "tight" in what I consider to be the "audiophile" sense. You could experiment with both these cords, or others; I used to own an Arcam Alpha 8SE-if you want to keep the costs down, you could go with one Cardas and one BC 62 and switch them between amp and CD player to see which combination gets you the right balance. I have an excellent line conditioner, which works very well with my current set-up, but did not do much for the Arcam CD player when I owned it, and I figure that unless your spending huge amounts (ie. plus $1000) on line conditioning, your amp is better plugged into the wall, so I'd be wary of line conditioners with your current set-up.
I have a bit too much bass in my system. I'll be happy to package up the extra send you some ;-).
I'd say reconsider a subwoofer. Unless you buy kilobuck speakers, you just can't hit those frequencies. I have a REL stadium with proac supertowers and I'm only sorry it took me so long to stop listening to the anti-subwoofer people and just buy it. I listen to (among other things) way-out electronic music which often includes very low frequencies - stuff that you feel more than hear - and the REL was a revelation. I have it on the lowest possible cutoff point and you'd never know it was even in the room - there's no directionality whatsoever.
I had the same problem you have and cured it by replacing my cdp with a Theta Miles cdp. It made a big difference and especially in the bass reproduction. However your speakers will not give you the bass that you are most likely looking for. Sonas Faber's website gives specs (40-20,000 hz) and refers to the woofer as a mid-woofer. I suspect your speakers were designed to work in conjunction with a subwoofer. You probably need to give it another try. Happy listening
I agree totally with Audiokinesis. If you really want to keep your mini-monitors, then more patience and experimentation with the sub-woofer thing is what is called for.