Booming Tunes

Happy Holidays to all the Goners. This afternoons quandry: How do you reduce the bass output of a monitor speaker? My current monitor rolls at about 65-70 hz My room has a boom at about 60 hz (11x14) All the better moniters have extention to 40s to 50s. I have subs but I don't want to EQ the monitors with hi pass. The speakers are placed according to Cardas and have min boundry reinforcement and the speaker cable is as small as I think I can get Also put a sock on the port but that leaned out the mids too much. Thanks in advance for your suggestions. And may powdered sugar fall gently upon your ears this evening!
Lewhite - very good question. I ended up with full range speakers but considered monitors and sub. Not only room has often nodes but designers of monitors tune bass reflex to stretch lows creating hump on first multiple of reflex frequency - usually around 80Hz. How to get rid of it? Some subs like JL allow to equalize sub/room using microphone plugged into sub but it cannot equalize hump (or room nodes) that is above cutoff. I've heard of bass traps (tubes) but never tried them.
Move the speakers well away from the walls. Alo lower the xover for the sub lower than the roll off of the monitors til they sound right.
You could insert a passive high pass filter (single high quality capacitor) between your preamp and amp with a roll off at 80 hz. Then tune your subwoofer accordingly.
I failed to mention that I do have a velodyne SMS1 and a 300b amp. The amp doesn't do the lower frequencys as well as the sub so the idea is to cross as high as possible and let the SMS handle the 63hz node but most of the good monitors that a set can drive won't get out of the way. I have 'some' room treatments but don't want a room full of trash cans full foam and hair.
Bassbusters (trashcans) are designed for this issue, but IME bassbusters rapidly lose effectiveness as you drop below 80ish hz.

So, you can either:

1) Find an active low cut that you can live with for your main speakers (I use an NHT x-2 instead of the bare bones filter in the SMS1) and use the SMS1 to clean up the issue via subs. This is what I do.


2) Find satellite style main speakers that are intended for use with a subwoofer. These have little to no meaningful in-room bass response (and no compensating mid-bass hump) below 80-90hz. You can cross this type of speaker to a sub at a much higher in frequency without actively low-cutting it. (Sunfire Cinema Ribbon Monitors would be one example, I'm sure that there are others.) This way you can cross to your subs using only the subwoofer hi-cut function in the SMS1 and maintain a "pure" main signal path.

Good Luck

BTW, the Sunfire CRMs are more than decent speakers at their price point, but I suspect that they might be a difficult load for a 300b amp.

a) Position the monitors about 56 inches out from the wall behind them. The energy bouncing off the wall will arrive out-of-phase with the direct sound at about 60 Hz, hopefully causing a zig where your modal room interaction is causing a zag.

b) Place your subs as close as possible to the monitors, allow some overlap in the crossover region, and adjust your subs so that they are 180 degrees out-of-phase with your monitors in the crossover region. Find this setting by placing the monitor on the floor woofer-to-woofer with the sub, and playing test tones. The deepest null is the correct setting.

c) Reduce the output from your monitors' ports by stuffing fiberfill or open-cell foam into the port. Open-cell foam is foam that you can breathe through.

d) Reduce the tuning frequency of your monitors by inserting a somewhat longer (if possible), smaller-diameter plastic tube into the port. Wrap at least one end of the tube with enough electrical tape to give a reasonably secure friction fit.

Sorry I havn't been around but the dog died. She was my tweeter reviewer. Thanks Marty and Duke. After reviewing my speaker position I found that they were 54 inches away from the back wall instead of 64 inches. I moved them to 62 inches because that moved them 8 inches closer to the listening position But guess what that did to the 'you are there instead of they are here' illution. More immeadacy and less room acoustics. It's also greatly reduced the 60 hZ boom to manageable levels. Now I'm going to try overlaping and invert and see where that leads. But I think port mods hold a lot of promise. I'll let the SMS1 clean up the remaining mess

Thanks all and may powdered sugar fall gently upon your ears tonight!