Axiom Home Page Forums General Discussion Advice from Axiom Owners M3Ti Bass Hump

Hi all,

I'm a new user to this forum. Glad to be in the company of so many experts!

Question for you, is there any inexpensive way of mitigating the 90-150 Hz bass hump on the M3ti? With my current set-up, 1 kHz registers as 82 dB. At 90 Hz, I'm reading 92 dB. In order to "smoothen" out this hump, I've had to boost the subwoofer so that I'm averaging 86 dB from 40-80 Hz. The end result is excessive bass and sorely lacking lower-mid (150-300 Hz at 75-80 dB). All in all, the M3 is a great speaker, but I'd like to hear less of the "bump" and more from 30-80 Hz (hence the sub), and more from 150-300 Hz. It's fairly easy to detect the bumps when a sine-wave sweep from 30-300 Hz is done.

Can anyone please help? Is there a way to enhance the 150-300 Hz region? Thanks!

Here are my particulars:
- Speakers: 2 x M3ti and 1 x vp100
- Position of M3Ti: 10 cm from back wall
- Receiver: Harman Kardon AVR 240 (set to "small)
- Receiver X-over: 80 Hz
- Receiver: Bass and treble controls only. No equalizer
- Receiver: Bass = 0; Treble = -6
- Wires = Generic 12 AWG

Were you unsatisfied with how the M3's sounded when you first setup the system?

There really isn't a way to smooth out the bump, it's just a characteristic of the M3's. Some members agree that the M22's are more suited to use a sub with than the M3's, because of the bass hump. There are a few users on this board that use the M3's without a sub, and wouldn't use them any other way. Try them that way and see if you like that. On the other hand, there are some M3's users that are very happy using a sub. I'm sure they can share their experiences.

First, if you have a pink noise or warble test tone DVD, calibrate your M3's and Sub so they are the same level by adjusting the sub. Then, try setting the crossover, see how that sounds.

Try leaving the Tone Controls at 0 for Bass and Treble. They seem to mess up sound for me whenever I have experimented with them. You said you were turning up the sub to compensate for the bump, yet you turned the treble down, which to me would seem to make the bass way overpowered and bloated, which is what you were commenting about.

When I first got my M22's, I got pretty bent out of shape over certain frequencies being higher than the others, and so forth, and it really kind of killed my listening experience because I would have a critical ear all the time trying to listen to those frequencies. It doesn't matter what a graph says, if it sounds good, that is all that matters.

I haven't heard M3's, but if you can't get over how your M3's are mixing with the sub, I bet you can call Axiom and trade up with some M22's, which have a very flat response. They mix with my sub as smooth as butter. Sometimes I can't tell if some bass is coming from my M22's, or the sub. I'm very happy with them.

You can also search the forums, because there are a lot of threads similar to this topic.

Good luck!

Thanks for your great post. I'll try to implement your suggestions regarding the pink noise, as I do have a generator.

Do you think moving the M3TIs away from the front wall and increasing the X-over frequency to say 100 Hz may help, or would it further harm the lower mids (150-300 Hz)?

Definitely try moving them away from the wall! You may very well reduce some of the boominess.

Dan had an excellent suggestion. If the 3's are new enough, see if Axiom will let you upgrade. If not, I'm sure they won't last long if you list them on Audiogone or Ebay.

Try putting the M3s about 3 feet away from back and/or side wall -- start with them 3 feet away from BOTH walls as a test. That should give you a response dip around 90 Hz. You will also get a peak at 2x the "dip" frequency, ie if you dip at 90 you will get a peak at 180 Hz.

Since you are crossing over at 80 you might want to move the dip and peak a bit higher, ie speakers a bit closer to the wall. My first thought would be to dip at maybe 120 and peak at 240, or something, which would be a bit over 2 feet from the walls.

If you want the dip centered at a different frequency, just take 1100/4 feet (ie 275 or so) and divide it by the frequency you want. The result will be the right distance to give you a half wavelength round trip from the speaker to the wall and back, so you should get cancellation at that frequency.

Obviously there will be other side effects with every change you make, but this info might help you understand what happens when you move the speakers around. Let us know how it works.

Thanks to "JohnK" for telling me about this in the first place.

Wan, welcome. I'm not a fan of a bumped-up upper bass to give an impression of greater bass extension and to add "warmth"; that's why I got M22s. However, it would seem possible that the amount of boost that you describe is due in part to room factors. What are your room dimensions and exactly what is the speaker positioning(not just distance from wall behind). As your mention of the term equalizer indicates, you're probably aware that if you did have an equaliztion feature available that you should be able to substantially reduce that upper bass prominance.

Thanks for all the great advice! For your info, the speakers are in a 12 x 10 with hardwood floors, two couches, one bookshelf and one coffee table. I can, unfortunately, move the front speakers no more than 20 cm from the front wall. Although I'd rather not do this, I might have to resort to a high x-over frequency, say, 150 Hz in order to "get around" the bump. Good plan or no?

I will be experimenting with the x-over and speaker placements over the next couple of days. I'll post my results soon.

Thanks again all, you guys are great.

Yeah, unfortunately, the HK AVR240 does not come with any equalizer adjustments, just a plain-jane treble and bass.

Regards,
Andrew

Andrew, if your ceiling is about 8', the 8'x10'x12' dimensions are quite good from the standpoint of room modes, so it doesn't appear that they would pile up in the upper bass to a great extent. The boundary effects which John B. described are a second type of room influence, but you may not have enough space in your small room to set them at the suggested distance from the walls. Note also that a similar effect to the one John B. described at 3' from the walls also occurs when the speakers are separated by twice that distance(e.g. 6')and are playing the same sound. A suckout around 95Hz results.


You haven't mentioned what sub you have and usually a 150Hz crossover would be only a last resort if the main speakers were weak below that area, but you can certainly try it and see if the result is a net improvement.

Yet another placement factor that should be mentioned is that the woofer cones on the M3s should if possible be at unequal distances from the three nearest room surfaces, i.e. the floor and two walls.

Finally, as has been mentioned, trading in for M22s might be considered.

I have a 9 ft ceiling. The back of the living room is open and connects to the dining room whose dimensions are 13 x 8 x 9 ft. Adjacent to the dining room is the kitchen whose dimensions are 8'6'' x 7'6'' x 8 ft. Hardly the ideal listening environment. With this detailed info, does this do me any further disservice in terms of room nodes and the upper bass piling?

The sub I have is a JBL e150P. Not exactly a real rocker, but sufficient for my needs.

I purchased the M3TIs about a 1.5 years ago when I lived in Ottawa. I moved to BC last May. I'd like to replace the M3TIs with the M22TIs as a very very last resort, if possible.

Thanks again!

Regards,
Andrew