Weird Bass Reponse on my Speakers.
Follow this link. It is a step by step program on how to correct the frequency response irregularities of your analogue RS SPL meter. I have done this to a few meters and it works MUCH better. Combine this with using a higher grade external electret mic and you've got a very good SPL meter for well under $75 total. Sean > RS SPL meter mods |
Clearly there's a dip around 100Hz (at least at the listening position). Although the Radio Shack SPL meter is not linear (we make a CD that corrects for it's non-linearities)--it's not THAT far off. Now the question is why do you have that dip? Chances are it is a null at your listening point. You can measure this by setting your CD player to repeat the 100Hz tone. Then walk around the room and plot the response of the 100Hz at different points. If you're listening point is in a null, the solution is pretty simple--you need to do some shifting of speakers and listening position (I say simple, but it really isn't that simple, because it will likely cause a null at another frequency). CARA software can help with this, they look for optimum positioning with the least nulls and peaks. You can also use the rules of 1/3 and 1/5 that tend (not always) minimize these problems as well. Lastly, our website offers some help on speaker placement at www.rivesaudio.com It's in the Acoustical Issues Section--go to the listening room and select speakers. There's a download there for a short paper on placement, but I have to admit it does not have a lot about peaks and nulls (we should probably update it some). If your problem is not caused by a peak or null, then it could be the room construction. Some rooms flex in such a manor that they actually create their own notch filter. Fortunately, this is typically not too difficult to fix. First you need to find out which part is creating the notch. In my experience it's usually the ceiling or floor of an older type house. The older construction allows it to sag and flex and essentially soak up a particular frequency--kind of like a resonator. Basically what ever it is needs to be re-enforced and made rigid. This can be easy in some houses, but difficult in others. Hopefully, the problem is just speaker and listening position. |
Ted: You definitely have very nice equipment . Now to the bass.. IF you have a camera tripod you can attach the SPL and set it in your chair at the same position your head is and measure / writing results easier ...... see following comments below 1-First try to measure again at higher volume. At the low levels you´re measuring outside noise might be affecting the readings and with more energy in the room your results can spread better and be closer to the actual SP you get under listening conditions. Go to let´s say 85 for the 1 kHz and repeat your measurements with and without sub as you did before. 2- Repeat the same FOR EACH SPEAKER (disconnect the other one taking all precautions to avoid damages!!!!!!! like short circuits) and with no sub. This will provide you with information on the different response you get at each speaker position in other words you´ll know your enemy better). As you pointed out the room is not symetrical so don´t expect to get even bass response specially not having a wall in one side, hey I also live in the less than perfect real world room most of us do.. 3- As Chilidog says each room / setup is different. Mine is a rebel I´ve been trying to tame..... Move your listening position i.e. measuring point one two feet forward and backwards and you´ll notice changes in the bass response, hopefully you might find a better place for your chair/speakers combo that will be more satisfying. Don´t dispear have patience be methodic on your approach keep a log and have fun!!! Luis |
Looks like you have a nice big dip in the bass response from about 140hz down to 60hz range. This is a common problem I find with monitors on stands in a lot of set ups. The overall perceived result, sonically, is weak sounding mid bass/upper bass, as you're describing. Just out of curriosity, how high is your ceiling and how high are the stands your speakers are on? Also, what are the room dimmensions, including the open area to the left where there's no wall? I'd need to look at where you sit/measure from as well, but speaker/seating location in the room is the single biggest determining factor for bass response from any speaker/system!!! YOu mentioned having some "non-symetrical" layout for your speakers, and that one speaker is out in the room with no wall to one side, where the other I assume is? You are definitely getting different bass response from one speaker to the other, and one speaker is probably producing more of the bass than the other in terms of room/seating interaction. Can you rearange your set up to get both speakers in a more "symetrical" placement in the room? Is this feasible? I usually find people screw this part of the most, and their set ups leave something to be desired. My assesment,not even having seen your room or layout, is that you can fix your problem if you know what your doing in repossitining your speakers/seating/speaker height! I know SF recommends certain height stands for their speakers to immage the way they want, and for proper sound stage height. However, my experiences STRONGLY DISSAGREE with their usually HIGH speaker height for stands in general! ESPECIALLY considering that most people listen to speakers in a room with an average 8ft ceiling height, this tends to always make speakers respond weaker in the mid bass reigion on stands that are much higher than 24=25" for standard monitors! When you consider SF usually recommends stands that are like 31" or so for their speakers (Extremas may be different), the results with low ceiling heights tend to not do so well in terms of response that high! Really, I think its better to use lower stands when you use an 8ft ceiling in general, and adjust the speakers "tip" towards your ears instead!...yielding better response usually. However, as there's inevitably more factors to consider, and each room/set up is different, it can very. But, again, usualy if you have to do stands with a lower ceiling for 2 way monitors, lower usually sounds more "full" and "strong" in the midbass, and reinforces the bsss frequencies from the floors bass augmentation. Sometimes higher can work better overall, and help reduce the 70hz peak that's lower in the middle of the floor/ceiling, and the 140hz mode that you get in the middle of the floor/ceiling can be smoothed by placing the speakers bass woofer at 2ft off the floor, wich is often imprrctical with speakers on stands. Really, there's a lot of factors. Still I believe with different location considerations for your set up, you can get much better, more accuruate sounding results and bass response from those otherwise excellent monitors. Another strong consideration would be to hire someone who knows what they're doing with rooms and speaker set ups! You'd be shocked at what a knowledgeable, experience experied can do! That's often well worth the money if you can find such an individual to do it for you. There's so many considerations in getting great sound from speakers in a room, especially smaller rooms! Those are the most challenging usually, and limitations apply without equalizers in very small rooms unfortunately. There are a lot of "tricks" and techniques to finding the right locations in rooms to place speakers and seats, depending on the room. It's knowing what those techniques and skills are, and how to utilize them, that can make all the difference! Good luck Good luck |
you also need to consider your test equipment, a radioshack SPL meter is by no means flat in it's response. I use one all the time while EQing a room for my PA but always end up fine tuning afterward. My advice is to use your ears and decide what frequency you like best for the crossover. The best part about this hobby is the tweaking (it keeps us all from getting board and spending way more money than we should!) |
You are probably reading a room notch at the 200Hz mark. The mid-woofer probably has a resonance point right around the 80-100Hz area, which would pull it down some there, and the passive radiator kicks in to recover it down to 40-50Hz. The website says the PR is tuned to 35Hz, so it rolls off relatively fast below that. There are also room effects likely in the other frequencies you are reading also.So you are probably reading combined effects of the room and the problems with the resonant spike and the transition to the passive radiator. Don't get too excited about it. Many speakers have behavior like this when placed in a listening room. Remember that most speakers are measured in an anechoic chamber, and not in your room. You always have to tweak the installation to get the best results. You might try crossing the sub out at a 6db slope at 80Hz, and see if you can stand the seam at that frequency. This should boost the midbass to cover the most egregious area, as far as SPL goes. You'll probably wind up with a little peak at 50Hz, but that shouldn't hurt too much. Whether it integrates well sonically with the Extremas at that crossover freq is your decision. |
