Horizontal mount

[one_happy_hippy]

Right im thinking about horizontally mounting a 12 - 15" woofer to fire downward in the base of my 3way floorstanders im constructing.

The enclosure for the 15" is ~ 200L with 1 10cm x 5cm vent (front panel thickness with a -3db freq. Hz. of 29Hz. XO @ ~ 300 - 500Hz (dependant on finally mid choice)

I have worked out the the sag will be less than 5% of the Xmax and so theoretically should be ok.

I have read that dispersion will be omnidirectional up to the freq where the effective cone diameter is equal to wave length
A 12" = ~ 1200Hz upper limit.

Is it better to have a solid panel for the woofer to fire at (as with some subs) I know that firing directly at carpet will affect the sound. From what i have read ideally a cone shaped panel (pointed towards the cone???????) would be best for dispesion without colouration.
Also what panel material would you recommend for best dispersion. I was thinking of a solid stone plinth (being a geologist).

So what do ppl think and what issues am i going to encounter?
Cheers

[johninCR]

I think bass becomes directional around 100hz, not 1200hz, so I'm not sure what you are trying to accomplish with radial dispersion of the bass up to 300-500hz .

[sreten]

For a c/o frequency of 300Hz to 500Hz bottom mounting
is simply out of the question, you should front mount.

sreten.

[one_happy_hippy]

The reason for horizontal mounting is the tapering cab shape i was working on would not allow use of a woofer larger than 10". As i was aiming to get really low bass extension i was hoping i could horizontally mount a larger woofer with a high spl - front ported to give a sense of directed sound while the really low bass would be omnidirection - to give an almost sub-bass feel to the sound.

Im not convinced by the woofer being omnidirectional at 100Hz - a number of sources suggest a much higher value - Can anyone clarify this?

Also what frq would you suggest that i i could realistically use as an upper limit for xo.

[Mudge]

Why not go with a four way if you want low bass extension and can't fit a large front driver?

You could even use a passive xo between the bottom two woofers and active for the rest, ie a 3.5 way hyrbrid along the lines of the large Wilson's (although they are all passive XO'd)...

[johninCR]

I understand omnidirectional to mean that we can't perceive the direction of the source. It seems to come from all around. This is what makes the use of a single subwoofer effective and 100hz may even be a little high for this effect. In your case, that point doesn't matter because you are going to have one in each speaker anyway.

I think you are talking about baffle step where the frequencies below a certain point begin to wrap around the sides of the cabinet instead of radiating in the front of the baffle.

Regardless of the baffle step effect, down firing frequencies from say 80-100hz up to 300-500hz is not going to result in the same sound as front firing because you will be listening only to reflections and no directly radiated sound.

Your idea will work great if restricted to sub frequencies of 60hz or 80hz or maybe even 100hz and below.