Bass in my room isn't good? Help

1. The dip in 160Hz is probably the speakers fault.

2. The peak in 40Hz is probably the standing wave in your room. Is one of your room demension is 14ft(+-1ft)?

3. I don't think your mini speakers can go down to 57Hz. It will go down to 57Hz but at -7db or more(just a guess). From the data it looks like your mini speakers starting to roll off rapidly after 80Hz. If you set the crossover frequency of the subwoofers at 80Hz, you are probably set it too low and creating a dip(50Hz & 60Hz) in the frequency response. Try to set the x-over point a bit higher, go 100Hz or even 125Hz or more and check it with your Sound Level Meter/Stereophile Test again and again until you get it right(leveling the dip in 50Hz and 60Hz). Also use the volume control in the subwoofer to fine tune the output level.

4. When you do the testing, try to do one test with the Echo bass trap and one without. Compare the result and see what happening.

Interesting case! E-mail me and tell me the result and I can offer you more useful info.

Make sure that if you are sending a signal already crossed over from the Classe ssp25 that the sub is run at full frequency. It is common with home theater systems that this is misunderstood and the sub woofer is also set at the the same frequency. If you are already doing this then it is not adding to your problems. Good luck

Adding to Edle's to-the-point words, the 40Hz/ 160Hz "anomalies" could be due to speaker placement vs. room acoustics.

Is your JM the Mini Utopia? If so, roll-off should be sharp @ a little over 70Hz -- so play with the sub accordingly, as Edle suggests.

Good luck!

Two comments, the low frequency response you measured, while not excellent, is actually quite good. The two dips in response are not particularly serious and you have no real peaks. As a rule peaks are much more objectionable than dips in frequency response. You should play around with speaker placement to see if you could further smooth out the sound. Second, refer to the following: http://audiogo5.iserver.net/cgi-bin/fr.pl?htech&983682086&read&keyw&zzradio=shack, it gives the corrections for the Radio Shack meter.

EXCELLENT suggestions !!! I too think that the crossover needs fine tuning as there is not enough "blend" taking place between the two woofers.

I would also like to add that the drop at 160 hz could be due to floor bounce from the monitor. I am not familiar with these speakers or their size, so i don't know how high up on stands they are mounted. Adding a "speaker beard" below them might help to cure this, as it adds baffle area below the drivers. One would have to play with the length of the "beard" to fine tune the response accordingly.

Other than that, i would take the bass trap out of the room and then measure the response. Then try several different placements for the trap and compare readings. I would start off by walking around the room and see where you hear the muddiest / most bloated response and place the bass trap there, as that is where the strongest node is occuring. Sucking up the excess energy at that spot will PROBABLY do wonders in terms of "bass detail" in the rest of the room.

Overall, it appears that your problems are not nearly as severe as others might be dealing with and mostly correctable with some fine tuning. Good luck and keep us posted.

Hi,
Thanks for your responds. Here are more of information.
My stereo system is on second floor and don't have any spikes yet. Room size L=14.8'X W=12'X H=8'. The Jmlab monitor Electra 905 goes down 57Hz with -/+3db. The Classe SSP25 has only one crossover frequency 80db, and I set the sub at 85db. The vollum on the sub is about 1/4 of the max.
I set the speakers 5'from the wall behind it, and 3'from the side wall for the last measurement. I changed the speakers 3' from the wall behind it, 2.5' from the side wall this morning.
1k=79; 200=76; 160=74; 125=78.5; 100=75; 80=78.5; 63=69.5
50=67.5; 40=78; 31.5=75
Look like everything are almost the same except for 160Hz improving a bit and 63, and 50Hz get worst.
One more question, if I measure from 30Hz to 20Khz, what should I expect the grap look like? How many db difference between the peak to valley is acceptable?
Thank you very much
DT

Just for kicks, turn the crossover on the sub as high in frequency as it goes and then check your readings again. If that doesn't do it, it's time to "bust out with a beard".

Quite honestly, your response is NOT bad. You are looking at a baseline of 75 db's +/- 4 db's and that is with NO work on your room. I have seen systems that were FAR worse than this with TONS of work put into them.

Since frequency response / tonal balance is but a small part of the picture, don't forget to deal with such things as soundstage, imaging, etc... Once you get the best in-room response that you can ALONG with good imaging and soundstage, I would THEN work on "tweaking" the small peaks and dips that you have. Sean
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