Mid-bass distance from floor--minimum?

In a scenario where you are trying to keep overall height of a speaker (3-4 way) from being too excessive, what is the minimum distance from the floor to locate an 8"-12" mid-bass?

For example, assuming you will use a 15" for bass, 12" for mid-bass, and still need to accommodate a mid and/or high frequency horn. Many designs have been built that place the woofer on the side of a cabinet. If the intended crossover point will be about 100 hz, is it okay to locate the mid-bass a few inches from the floor?

I was looking at John Inlow's mid-bass 100 hz horn today, which uses a 12" B&C driver. He places them directly on the floor, with a round horn above. I assume there is a sub/bass cabinet lurking somewhere in the room. If a direct radiator was used rather than a horn, does that affect the sound, and thus its' location?

Thank you for any help!
 
Midbass close to floor

Giralfino: that is interesting. If a person selects a very efficient mid-bass, that could be a very significant factor. The units I have, or are considering, are all in the range of 95-100 db/1w/1m.

Krivium: Thank you for that link. I had never read a good definition on that topic. The plug in calculator is very nice to have! Appreciate your help!
 

celef

Member
2012-11-26 7:40 pm
is the info on that website really accurate? like the example of putting a loudspeaker 1/4 wavelength from the front wall will get you a frequency cancellation, yes that is true only if you sit right up against your loudspeaker, but at a normal listening distance from the loudpeaker there is no such null, but other frequencies comes in to play
 
Midbass close to floor

celef: I would have no idea if that info is accurate. That is a problem with learning...from whom are you learning? I believe about 10% of what I read on the internet.

In this case, I'm hoping to get advice from people who understand this better than I.
 

krivium

Member
Paid Member
2009-10-13 2:43 am
Hi,
The effect is real.
The calculator will give you insight about a geometrical problem which is then easily simulated.
The results are guide which you can easily detect with a measurement microphone, a honnest quality soundcard and free analysing software ( RTAA).

Placement of your loudspeaker will greatly change their sound rendering. Find the best compromise may be headhache and this simulator help to identify some ( possible) offending flaws which will occur.

Is it something you want to bother with is up to you.
Maybe you think that our brain compansate for that floor bounce effect yes maybe this is right. To be sure we should have psycho acoustic studies to refer at but i don't.
My experience led me to thought we don't compensate this and our brain is aware of the effect.

That said you could try to locate your loudspeaker 80 cm away from (both) side wall and 80cm away from the wall behing them. See for yourself if something happen in the 80hz area.
This is a simple test.

As you have this information (which i repeat is a geometrical issue) you can try to develop tactics to counter some of this issue as to delebirately locate a loudspeaker as close to the floor and a mid much higher and choose a x over frequency outside of the range where floor bounce happen.
This come to a price though, you may loose acoustic summation of output of the drivers which will probably located more than 1/3 to 1/4 a wavelength of cross over frequency.
IOW you loose point source behavior and the message might seems to provide from 2 distinct source rather than one.
This an example.
 

celef

Member
2012-11-26 7:40 pm
The info is too simplified i guess, putting a woofer at a 1/4 wavelenght in front of a Wall Will not create a null at the listening position, unless you are sitting on your woofer that is. Since you most likely will sitt at a distance to the woofer and even at a greater distance from the front wall, there will not be no null att the 1/4 wavelength frequency.
 
quite a few successful/proven designs put the co point between a 15" bass driver and mid around 250hz (usually 2nd order CO). any higher and the human voices start appearing to come from an unnaturally low position. any lower and you start to get a floor-bounce dip around 300hz.
 

krivium

Member
Paid Member
2009-10-13 2:43 am
is the info on that website really accurate?

It is good practice to question source of information and try to find different pov. That said this point is well known for years.

Need Help and Advice With Setting Up Your Monitors? | Genelec.com

All the specualations, articles and graphs are meaningless because room acoustics/furnishings cause variables which cannot be controlled.[/QUOTE

Yes this is why i talked about guideline. The way the room is built ( lossy or resonnant in the low end) some furnishing... bring to the real life world variation but nonetheless the issue doesn't disappear if you decide it shouldn't be taken care of.
 
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krivium

Member
Paid Member
2009-10-13 2:43 am
as you know, cancelation happens when two soundwaves are out of phase, and there will be no cancelation at the 1/4 wavelength frequency because the two soundwaves will not be out of phase at the listening position

I always find that arguing against some accepted physical laws to bring strange conversation, like with some of my friends which suddenly became flat earther.
Well up to them to prove the rest of the world is wrong.
'Allison effect' is known for almost a century when Allison depicted it in 1927...

Http://david-janszen.squarespace.com/blog/speaker-setup-minimizing-the-allison-effect2015321
 
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krivium

Member
Paid Member
2009-10-13 2:43 am
Who is right or wrong doesnt matter at all.
This place is great to learn things and we are all here for that ( at least this how i expect it).

If you learned something this is wonderful (even more since you experienced by yourself theorically), even better to make statement about that to stop confusion.

Back to topic:

I regularly use the sbir simulator to check placement of multiwoofer set up stacked vertically. By playing with geometry and xover freq you can lessen floor bounce.
This is one point which isn't often talked about but MTM/ d'Appolito configuration can be pretty effective to lessen the effect ( particularly with 'big' woofers from 10" to 15"). You'll see that for example a Kinoshita Rm8 is good at that and is a sweetspot relative to their overall size ( ...and not only for one parameter other thing come into play, really smart design to study).

Zmyrna, yes what i tried to explain! That said it can be relativised because of schroeder frequency of typical room. It's frequency is around 200/250 hz for medium/large sized domestical room, more often higher in freq with smaller rooms.
That means that everything below this frequency is room dominated.
Usually it is considered that below 80hz we don't manage to locate the source. From my experience this is true outside and in large room.
In smaller one this frequency goes up and i suppose it follow schroeder frequency, so as an outcome you could cross over higher in freq without being able to locate the source. I've heard 150hz frequency crossed sub and wasn't able to locate them.

Maybe higher could be possible, should try.