Dear Fellow SC IVA owners

I absolutely do not recommend adding a subwoofer to the SCIV system. The SCIV is an incredibly coherent speaker system. Adding a subwoofer would only degrade the coherency. Besides, if the system is set up properly the performance from top to bottom is amazing.
Measurements for the SCIV are actually taken at 10 feet not 3 meters.
My best results with the Dunlavy SCIV were achieved by not using an equilateral triangle, but every room is different. The room will dictate the best arrangement.
A true D'Appolito design requires a 3rd order 18bd per octave crossover allowing the drivers to have the same horizontal dispersion characteristics.
The Dunlavy SCIV actually places the tweeter slightly below ear level.
I also spoke with John Dunlavy on numerous occasions along with his marketing manager who's name escapes me at the moment. John recommended starting as close to the wall behind the speakers as possible and moving them out as needed. 44" from the rear wall may be the reason one might feel the need for a subwoofer.
I have the ability to reverse my listening room. I can turn it around 180 degrees. When I set up speakers on one wall the speakers end up about 40" into the room. It doesn't matter what speakers. All speakers sound the best in approximately the same place.
When I reverse the room the speakers can be much closer to the wall behind them because the listening position moves forward. And this is how the Dunlavys sounded the best in my room, close to the rear wall and spaced far apart in a non-equilateral triangle, but this is how my room works and it has nothing to do with other rooms.

Thank you all for your excellent responses. So it is clear (whether right or wrong) I added the subwoofers not to extend bass (it was already extended and more importantly of very high quality, which characteristic I have found rare in most speakers) but because my engineering friend told me when he did this to his SC IVAs the midrange improved. And sure enough when I implemented subs, it improved the mids. I do not have the SC IVAs bass cut off. I just added the subs in parallel out of the amp and have the smallest amount of gain and the lowest crossover setting. The result was better. However, the biggest change occurred when I put the Symposium platforms under the speakers with Walker spikes under those. And of course keeping the speakers wider apart. Rrog said something interesting about being close to the back wall. I am going to try that. I'm five feet out now. Does anyone else have experience with this? Most speakers are better a good amount off the back wall. SC IVAs may be different. (I know one thing, even if not optimumly set up, and mine are not optimum yet at all, recent changes have made my set of SC IVAs sound phenomenal. Something about this speaker is amazing.) Jonathan

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?

Pryso, thanks for this data. Yes, I believe your basic concept is the answer. Move the speakers bit by bit until you achieve the highest quality or balance. Each room/equipment relationship is different. I know one thing. My speaker are in the world class realm now with recent changes including a clarity and detail which I did not have before. I have more work to do though. And the musicality is not only still there, it has increased. (Yes, I am on twice a week now with the Jazz program. Friday/Sunday at 7pm unitl 9pm EST. NPR affiliate called Robinhoodradio.com. I think you'll enjoy it. All nonprofit. Just finished preparing tomorrow night's show. Jonathan

Jonathan, I just don't understand how letting your speakers run full range and adding a subwoofer can improve the midrange.

I have heard improvements by using a crossover while adding a subwoofer thereby relieving the main amp of low frequencies and removing bass energy from the main speakers.

What exactly was the improvement you heard? I am curious.