# Weak midbass



## Mrhjelm (Oct 28, 2012)

Yez, here we go again
It has been a while since my last visit here and I have done some reading since then 2012. BUT I can still not figure out why my midbass so weak! 

Not to be rude or ignorant but I had a similar post earlier where I was asking about this and I was told to include BSC to my crossover, which I did not do (but will do to even things out). I am picking this up again now and want to confirm if you still think that is the issue for weak midbass. Earlier I did not have any measurements available which I do now hope you can have a look and give me your thoughts.


Appreciate all you help!
Thank you in advance!
Best regards
Mattias


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## Wayne A. Pflughaupt (Apr 13, 2006)

I assume we’re supposed to be looking at the dark green trace with the big “v” at 89 Hz? It’s right in the crossover region, so I’d suspect the sub is out of phase with the mains, or time alignment is off, or something along those lines.

Regards,
Wayne


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## Mrhjelm (Oct 28, 2012)

Wayne A. Pflughaupt said:


> I assume we’re supposed to be looking at the dark green trace with the big “v” at 89 Hz? It’s right in the crossover region, so I’d suspect the sub is out of phase with the mains, or time alignment is off, or something along those lines. Regards, Wayne


Hi Wayne and thanks for your reply!
I have made some notes at the bottom of the graph. It is correct regarding the big V, the xo-frequency is at about 600hz, so the crossover should be good in this region. What you see is the port & bass driver frequency response (nearfield). Do you think the suck out is due to cancellation from the port? Should I lower the port tuning frequency to solve this or what is your suggestion?

Best regards
Mattias


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## Wayne A. Pflughaupt (Apr 13, 2006)

Oh - I didn't notice this was the DIY speaker section. You’ll get better informed answers from others, this is not my specialty.

Regards,
Wayne


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## jtalden (Mar 12, 2009)

It looks like it may be room effects. How distant was your 'Nearfield' mic? How distant were the nearest boundaries? 

I wouldn't expect your smooth port and driver measurements to result in a rough combined measurement in an anechoic situation so the test conditions and setup are my first thought.


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## Mrhjelm (Oct 28, 2012)

jtalden said:


> It looks like it may be room effects. How distant was your 'Nearfield' mic? How distant were the nearest boundaries? I wouldn't expect your smooth port and driver measurements to result in a rough combined measurement in an anechoic situation so the test conditions and setup are my first thought.


That was my first thought too but I tried the speaker in different rooms and also tested other speakers at the same location with much better result. The nearfield is approx. 1" from the cone and at port "mouth". The only explanation I could think of is cancellation from the port or in some way from the mids, BUT the xo-frequency is much to high and should not be able to interfere. I should mention that the port is placed on the rear panel. 

I do not think box resonance is the issue either, I assume this would show in the nearfield measurement. 

Best regards
Mattias


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## Mrhjelm (Oct 28, 2012)

I will do some extra measurements now and post the results. Hope anyone can help me so that I do not make the same misstake again and also so I can learn more.


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## jtalden (Mar 12, 2009)

Maybe place the speaker near the middle of the room on the floor with the mic also on the floor for a 'ground plane measurement'. That will help increase the time until the reflections from other boundaries impose themselves. A mic distance of 1-2m is pretty typical. There is more info on this method with a browser search. 

If the dip moves with mic distance and speaker location then it is a room effect.


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## Mrhjelm (Oct 28, 2012)

jtalden said:


> Maybe place the speaker near the middle of the room on the floor with the mic also on the floor for a 'ground plane measurement'. That will help increase the time until the reflections from other boundaries impose themselves. A mic distance of 1-2m is pretty typical. There is more info on this method with a browser search. If the dip moves with mic distance and speaker location then it is a room effect.


Thanks again for taking you time! I will try that and get back with my results.


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## Mrhjelm (Oct 28, 2012)

Well, I think it is safe now to say now that my problems are due to room modes. I tested different speakers at same location and moving the mic at different distances from the speakers with almost identical results, in regards to room modes. Thank you for helping me out!


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## jtalden (Mar 12, 2009)

Glad that I could help.


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