Dear Fellow SC IVA owners

Hi Jonathan. I owned Duntech Princess (older sibling to the DAL SC IV) for 19 years and have four friends who also owned or still own that model. Based on that I've had quite a bit of experience with rooms, placement, amps, etc.

I absolutely agree with your recommendation to add a subwoofer. While the Princess and SC IV have very decent bass response by themselves, they (like most full range speakers) can benefit by the removal of the bottom one or two octaves. As you suggest, this is more to benefit the upper bass and midrange than for bass extension. I did not have room to add subs but two friends did and both the Vandersteen and Velodyne subs can be made to match very well.

A few thoughts on placement. First, John Dunlavy often recommended long wall placement for his speakers. I believe this was because of the need to keep them away from sidewalls. Second, he recommended an equilateral triangle placement between speakers and prime listening spot. Taking a clue from the Owner Manual, factory frequency response measurements were made at a distance of 3M to allow integration of the drivers. Based on this, I feel that 10-11 feet should be optimum distances for the triangle. Third, I did extensive testing for smoothest bass response in my room and ended up with the front baffle of the speakers 44" out from the front wall (your distance may vary, depending on room characteristics). And fourth, I found toe-in with drivers pointing 2-3' behind my head (inside cabinet wall just visible) to be best.

Don't ignore listening height. The D'Apolito array means that vertical spacing is just as important as horizontal. Try to have your ears at the same elevation as the tweeters.

I think the question of spikes, platforms, etc. will be dependent on floor composition (wood suspension, concrete, etc.), floor covering, and amplifier choice (with resulting woofer damping).

I still consider the Duntech and DAL speakers to be among the best available. But they are very revealing of set up and component matching. Spending the time to optimize both for your situation will be musically rewarding.

Unsound, the manual for my Princess showed an equilateral triangle for speakers and prime listening seat. Also, I had the pleasure of chatting with John a couple of times in person and discuss speaker set up. Equilateral is what he advocated and how he set up his speakers (DAL) at shows.

My understanding of a D'Appolito MTM array is for two midrange drivers spaced equal distance above and below the tweeter with a phase appropriate crossover.

http://stereos.about.com/od/glossaryoftermsd/g/Dappolito.htm

While not all of John Dunlavy's designs (Duntech and DAL) conformed to this array, all but the earliest and smallest did so, including the Princess and Jonathan's SC IVas.

Every room is different, to say nothing of our differences in personal taste.

When I owned my Princesses, I went through a careful exercise to achieve the smoothest bass response in my living room. Note that was different than seeking the maximum bass response at a given frequency. Using a Stereophile test CD and a calibrated SPL meter and measuring from the listening position, I inched my speakers out into the room by 2" increments while measuring each position. When I found the best distance I then measured again one inch either way from that position. I ended up with the equivalent front plane of the drivers for each speaker 40" out from the front wall. Any distance closer resulted in an increase in bass frequency (<200 Hz) variation.

My point is not to recommend a 40" placement for anyone else, but to suggest that placement too close to the front wall may produce more apparent bass, particularly if this creates a peak at say 50, 63, or 80 Hz, but this will not be the smoothest overall bass response. Be certain of what you are trying to achieve.

Jonathan I have not checked for some time, are you still doing your jazz program?

I'd like to clean up a few points here before the end of the year. ;-)

Yes, I was wrong to call Dunlavy designs D'Appolito arrays. I do know John Dunlavy liked symmetrical driver arrays because they simulated a point source speaker when matching mid and woofer pairs equal distance (respectively) from the tweeter. I believe all of John's designs had first order crossovers to maintain time and phase coherency. Whatever D'Appolito uses or did use, it apparently was not first order.

Rrog called me out saying SC IV measurements were at 10 feet, not 3 meters. Well, I was referring to the Princess which had factory measured responses made at 3.5 meters, thus my suggestion for 10-11 feet listening distances. And as I think we agree, each room will be different so there is NO specific formula. Trial and error is necessary unless you are extremely lucky.

The third point is my agreement with Rrog in not understanding how adding a subwoofer will help the midrange when the main speakers and amp(s) are not being rolled off. My introduction to good subwoofers came from a dealer who demoed a sub set up by playing s solo violin recording! When the approximately lowest two octaves (20-80 Hz) are removed from the signal going to the main amp and speakers, their job becomes easier and improvements in upper bass and midrange can be realized, in addition to potential extended bass response. Now I cannot say that Jonathan did not hear improvements extending into the midrange (I was not there), but I will suggest he will hear a greater improvement if he reconfigures his system to roll off his SC IVAs and main amp within the range of 50-100 Hz. The best point must be determined in his system.

Lastly, Dunlavy utilized stepped baffle designs, in addition to wool felt, in his Duntech speakers. As I recall the DAL speakers have a flat front baffle but still utilize the wool felt and crossovers to assist the time and phase alignments. Yes John was among the relatively small group of truly great speaker designers.

Thanks Unsound. There is enough mis-information on the internet without my adding to it. ;-)

Probably what I was thinking of, the Duntech baffle step backs are open on the sides to help dispersion. My recollection is the DAL speaker's sides are not.