Markbass 151hf + 151HR =?

mactac · #1 02-01-2011, 03:58 PM

I'm thinking of combining 2 15 inch cabs, the 2 markbass 8 ohm ones - the HR & the HF.

Any thoughts on this? Is it crazy putting the 2 together?

I realize that there may be a lot of low end (hey, I'm playing reggae)

I'm powering them with an LMII

Any other considerations? One is front ported, the other rear - is that a setup for weird phase problems? I would expect the ports to be in-phase with the speakers?

RickenBoogie · #2 02-01-2011, 05:00 PM

The ports are omni-directional, so no problem.

mactac · #3 02-01-2011, 05:27 PM

true, but I was more worried about phase relationships since the distance between the 2 ports is a couple of feet.

RickenBoogie · #4 02-01-2011, 05:54 PM

There is no phase relationship. Only the drivers have a phase relationship.

mactac · #5 02-01-2011, 06:10 PM

Quote:

Originally Posted by RickenBoogie

There is no phase relationship. Only the drivers have a phase relationship.

Perhaps you can explain. I understand the physics of sound - it travels in waves, whether it's from a driver, a port or a bird. If there is sound, there is waves. If there is waves, there is most definitely phase.

If 2 sounds leave 2 different point sources, they can be anywhere from perfectly in phase to 180 degrees out of phase, and everything in between.

What am I missing here? I don't disbelieve you, but I'm having a tough time rectifying what you are saying based on my understanding of the physics involved.

All sound has phase....

RickenBoogie · #6 02-01-2011, 06:14 PM

Let's let an acoustical engineer answer the question with science, but what I'm saying is, the 2 spkrs in question, one from each box, will be "in phase" with each other, or else cancel certain frequencies out. You'd hear that. The ports, are not speakers. They emit the lowest of frequencies, and are, omni-directional. So, it makes no difference if they come from the front, back, or sides- they fill the room every which-a-way, and therefore, cannot be "out of phase".

mactac · #7 02-02-2011, 03:50 PM

I don't think that what you said quite makes sense. Directionality is one thing, but the waveform relationships of 2 sound sources is completely different.

The reason I am concerned about where they come from is that one will be farther than the other (ie coming from the front vs back), and that will potentially throw the 2 waveforms out of phase. Even if they are NOT out of phase, there will still be valleys & troughs caused by interference.

This is why when you're setting up a PA you have to be really careful when you're using more than one sub...

RickenBoogie · #8 02-02-2011, 05:35 PM

Well, I've got nothing for you then, you need more members to answer, and maybe get lucky and get one of the many engineers here to explain. Good luck.