[scorpion]

I have been away a couple of days to marry my eldest son and this interesting discussion occurs. Well, I had to choose party.

My hope was indeed to engage MJK and johnk in the thread and I think that even we laymans are a bit wiser now. JohninCR served us all as a  good clarifier and middleman. A lot of thanks to all of you.

Of course the discussion shall continue.

Some conclusions so far:

The U-baffle of johnk's design would be an obvious choice for the most compact and also very cost effective sub-woofer solution. I have experimented with two 12"ers in push-pull configuration on a baffle which I could turn into a kind of Ripol/W-baffle and a H-baffle inspired by the Linkwitz' designs. With the Ripol/W-baffle I had no difficulties in both measuring and hearing the fundamental resonance. The H-baffle I measured a much smaller resonance and it was not at all so obvious in listening if it could be identified at all. The sound was much more open and uncoloured. The U-baffle would promise the same response as the H at smaller dimensions.

I think that the lot of us having some kind of baffle with folded wings also should be encouraged by MJK's analysis. I have tried various chassis in wing baffles. The best have been the Ciare CH-250 and the B200 as fullrangers. I have not been able to measure or hear any resonances from these elements in the baffle. It probably will be a bit different with potent bass-elements. But it will also depend on dimensions.
I think that the easyness of identifying the resonances in my Ripol/W-baffle was the result of a small open surface i relation to the cavity volume which I think will affect the amplitude of the resonance. The topless U-baffle I think would be my second choice for bass-baffle also beeing able to go a bit higher in bass before crossing over. And that even with a choice of 90 degree wingattachment. But experiment, listen, measure and report ! 

/Erling

[JohninCR]

Scorpion,

Welcome back to your own thread.  Something we should all keep in mind that JohnK had reminded us of on several occasions is that even if we are only using the bass section below resonance, there is a bass gain to be had of as much as +6db if we properly damp any rearward facing cavities of any folded design.  This acoustic resistance prevents the lumped mass behavior, so you achieve the full propagation delay possible.  This goes for dipole designs like H's as well, as long as you don't damp the frontside.  The most compact designs will derive the most benefit, so if you have a very tall and wide H baffle in relation to your driver size the gain may be minimal.

I hope to come up with some non-standard shapes that have a similar effect as damping, but we'll see how that goes.

[Polarbear]

With the Ripol/W-baffle I had no difficulties in both measuring and hearing the fundamental resonance.

Erling

Hi Erling

Nice test.
At what frequency did you get the resonance in the ripol?

Bjorn

[scorpion]

Hi Björn,

It was some time ago. I can do only discretionary measurements. The Ripol/W was like a N-baffle with two cheap Pro Audio SW12" elements in push/pull over each other on a baffle measuring 60 x 35 cms, openings were 60 x 10 cm, just to accomodate the drivers. This baffle  measured 60 x 27 x 35 cms (hwd). As far as I remeber resonance started to build up about 150 Hz topping at about 250 Hz. It was easily recognised. But most annoying was the colouration starting to set in over 100 Hz. I don't think you can go higher than that with a Ripol or W-baffle.

In the H-baffle the sound was open and on music you would not be able to hear any resonance. The H was only 60 x 35 x 22 cms (hwd). Two of those elements was not quite enough to create satisfactory SPL in the bass.

/Erling