Bass Response on Dunlavy SC-IVa

While i can dig up the facts / figures on this speaker, does anybody happen to have the crossover points handy?

I agree with what Tom / Audiotweak is saying in that the woofers are non-symmetrically loading into the room. Since all rooms have various ceiling heights, the results with this type of speaker will vary from installation to installation. Then again, this is true ( to varying extents ) with any design that raises the woofer(s) up above floor level / very bottom of the cabinet. That's because boundary effects are somewhat "set in stone" with a design of this type.

One will also encounter this with woofers that are stacked vertically but somewhat spaced apart from the other. This is especially true if the bottom woofer is already measurably up off of the floor. The larger Vienna Acoustics speakers suffer from this quite noticeably and even the reviewer in Stereophile commented on this. If i remember correctly, he went so far as to say that they were the hardest speakers that he's ever had to deal with in terms of placement.

Having said that, the staggered woofer array can be put to great use, but one would have to fine tune the spacing between the drivers and the crossover points for the individual listening area that the speakers would be used in. By "tuning" the output range of one woofer where the nulls of the other woofer(s) are occuring, the response sums to something that is much flatter overall. This is probably what Dunlavy was trying to accomplish, but without knowing the ceiling height and the distance from the side walls and how far they are pulled out into the room, there is no way to optimize the design.

Having said that, Dunlavy gives pretty specific placement suggestions for these speakers that seems to work quite well, but if you can't follow them, there are other methods that may work for your given installation. Only problem is, this requires a LOT of moving & listening, which large speakers like this aren't exactly easy to work with. Sean
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Try this: Move your listening chair,place a ladder where your chair use to be. Play a constant test tone at about 60hz. Climb the ladder up to ceiling height, make reference of the 60hz tone with either an spl meter or your audio memory. As you come down the ladder at each step make another measurement and record the output, do this until you reach about 2 feet from the floor. Now after you have done this move the ladder, re-install your chair at the original position and take the same measurement at ear level {38to40in.}..At ear level you will have a 6 to 8 db suckout..in contrast to the floor and ceiling measurements.The frequency of the suckout maybe 50 to 80 hz so your reference tone may vary slightly.While doing any of these tests do not touch the volume control. ..You can mitigate some of the phase cancelation by moving your ceiling or by building an acoustic lens attached to the ceiling ..Tom

I agree with Theaudiotweak. But a potentially easier way to mitigate phase cancelation here might be to just lay the IVa's on their sides. But that solution is not without it's own problems. :)

John, Peter Snell had a speaker [Type 1} that had its drivers near the floor level on an angled baffle tilted back with a ramp in front to reduce the floor bounce effect..He also had a U.S.patent on baffle designs to reduce room boundary effects. Truly a designer who thought outside of the box. Had a in home demo of that Type 1 speaker and a sales meeting with Peter Snell...that was probably in 1980 or 81..to bad he is no longer with us.He was truly a innovator. Tom

It is a very interesting question, cathedral ceiling and Dunlavy 4.
I had never known it until I bought a Behringer deq2496. It also took me a week to spot root cause of the problem. However, I got a 20dB hump, instead of suckout, from 45 to 65Hz at listening position, 3.5' from floor. If I move vertically up to 7' from floor, the hump reduces significantly by more than 10 dB.