Side firing woofers in 3-way

[Mos Fetish]

Hi

There's been some discussion from time to time on side firing woofers but not enough for me to make an opinion, so...

I had an idea to use the following drivers in a 3 way config:

1 x Peerless 850146 10" CSX side fired on a 400mm baffle
2 x Peerless 850488 5" HDS mids on a 220mm front baffle
1 x Peerless or Vifa tweeter (not sure yet)

XO for the woof/mid at around 125hz, mid/tweet around 3500.

What are the design problems I'm likely to face here?

Feedback much appreciated.

Mos

[7V]

The wavelength of the sound at 125Hz is nearly 9 feet (2.6m) so you shouldn't have any problems with a side firing woofer but, if you're going this way, I would suggest a 3rd or 4th order low-pass filter on it.

Steve

[DIY_Peter]

Why isn't it a problem 7V? because those frequencies aren't directional?

It looks like a great way of making a more elegant cabinet. The Mission 782 have side firing woofers. Maybe it's just a coincidence, but most magazines rate them high, apart from the bass that seems a bit odd...

It didn't really sound odd to me when I listend to them in a store though.

[Mos Fetish]

7V

I was goning with a 2nd order. The values are large and I'm sure 2nd order will be fine.

Quite frankly, side firers seem to polarise opinion.

Mos

[phreeky82]

well if u did a search, you probably would have found my questions about it before i made mine

similarly, mine had a single 1" dome tweeter, 2x5" mids and 1x8". i went for the 8" because my enclosures were big enough, and a 10" (at least one i could afford) didn't have very good response in that size enclosure. by the way, i used all Response drivers.

i've tried a couple of things with mine to get good sound out of them. i originally put the mid/tweet xo @ 3.5k 2nd order. i then didn't bother crossing the 8"s over, but just ran both the mid/tweet combo, and 8" parallel in full range. i did this because i hadn't gotten around to purchasing components for the rest of the crossover, and i was thinking about bi-amping.

i am still yet to try it like this with the 8" facing inward, but facing outwards there was no imaging problem.

i then, using a active xo built into my pc, ran them bi-amped. i can change the xo freq variably with a slider. it will depend on your driver sensitivity and response, but i found around 130Hz to be good. this was because my 5"s (in a sealed enclosure) response started to get around -1dB at this point.

i would honestly like the 8" to be on the front, but a 10" like you're using would be a little big. i however want the small front profile of these cabinets of mine (around 16cm wide externally).

i should also mention that my 8"s are also sealed, but the response down low is fine for music, and for movies i have my sub (so ultimately i'm running a 4-way system for movies ).

[7V]

Originally posted by DIY_Peter
Why isn't it a problem 7V? because those frequencies aren't directional?

Yes, keep the freqiencies low enough and you could even put the woofers in separate boxes, I do.

Originally posted by Mos Fetish
I was going with a 2nd order. The values are large and I'm sure 2nd order will be fine.

Quite frankly, side firers seem to polarise opinion.

You're probably right. You would be 3dB down at 125Hz and 15dB down at 250Hz. For a side firing woofer in the same cabinet this will probably be fine. I would say not a separate box job though, with 2nd order at 125Hz.

Yes, this issue does polarise opinions. I suspect that this is as much psychological as actual, if the implementation is right.

[SY]

IIRC, NHT uses a second order from the woofer in their well-regarded 3.3. You might even think about copying their idea of a tilted baffle and long, wall-loaded cabinet.

In most side-firing designs, the woofer loading is near the floor, a good thing for bass smoothness (see Roy Allison).

[kelticwizard]

The difference is in center-to-center spacing.

If the centers of the bass unit and midrange are ½ wavelength apart at the crossover frequency, there will be cancellation there. If they are ¼ wavelength apart there, there might be some cancellation, like 3 dB. If they are much less than ¼ apart, you don't have to worry.