Pryso, I could be mistaken about some of the details, but, John Dunlavy might have made some prototypes(?) of a statement speaker (Magnumns?) that had active digital cross-overs and separate digital amps for each driver in a rather oddly shaped cabinet that appeared to look like 2 triangles mounted upon each other at a single corners that had flat baffles. The digital cross-overs were to electronically correct for the timing issues of the various voice coil depths. Apparently this avoided the cupped horn loading problems of the stepped baffles. I think John Dunlavy was waiting for higher resolution digital devices to become more of a marketable item to make the speakers more reasonably priced. John told me that this was the future of his designs, and he hoped that as the digital technology developed, it could be trickled down to his less expensive products. He believed that the digital technology could cut the costs of the then necessary labor needed to hand match each set of speakers. Unfortunately, poor health took over before he and us could realize the promise of his brilliant ambition. |
Pryso, you are thinking right. A very basic description would be, Stepped baffle is putting the tweeter behind the same plane of the woofer to align voice coils. (kinda like a stairstep) That is why I called it voice coil alignment in my earlier post, that is stepped baffle. You are actually putting the voice coils in alignment. The idea is that the sound radiates from the same point for correct time alignment of the signal to your ears. The dispersion from the drivers then bounces off the frame of the drivers. The wool felt absorbs part of this to keep the reflections from warping the frequency (defraction). You can also align the signals electronically, this is called stepped baffle compensation for time alignment.
I hope this helps, Tim |
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. |
Pryso, the Dunlavy's also have stepped baffles, in order to maintain proper time alignment. |
Hi Pryso, the wool was strictly diffraction control. I agree with you on the subwoofer points also. |
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. |
Also, Just looked at the SCIVA... The only thing in common with D'Appolito is that they use a wmtmw arrangement. Totally different design parameters. These Dunlavy's are extremely well thought out speakers. Dunlavy achieves time alignment through voice coil alignment, he keeps speakers very cohesive by using 6 db per octave slopes, he handles baffel step compensation by the use of felt...He tackles every problem.... in a different way and by what I can tell with terrific results. |
Hello all, I have researched D'Appolito designs quite a bit and built my first speakers in 1979.
"A true D'Appolito design requires a 3rd order 18bd per octave crossover allowing the drivers to have the same horizontal dispersion characteristics".
The above statement used to be accurate, but no longer is. D'appolito started that way and used 3rd order electrical slopes. Today, he has changed most of his designs to 4th order acoustical slopes. He specifically found that with the tweeter at ear level, this crossover improved the Symmetrical dispertion pattern maintaining good phase and amplitude summation.
4th order (linkwitz riley) acoustical puts your acoustical slope 6db down at the crossover point. Time alignment and proper phasing are much easier to achieve here and D'Appolito did tons of research of lobing and cancelation effects in vertical alignment.
I am currently useing D'appolito I use 12/18 electrical slopes to achieve 24/24 acoustic.
I am not speaking for Dunlavy in anyway, I have not seen crossover schematic for SC IVa |
Dear Rrog, I have no idea why adding subs with no crossovers improves the mids, but it does. I put on JL Audio subs crossing over very very low at 25Hz with very little volume (barely on) and the mids opened up and are cleaner and clearer. And the bass is slightly extended. The JLs match well. I have no idea how this can be and would never try to explain or defend it. But I hear it and so does my recording engineer associate who taught me this. I'm so used to it that when I try the system without the subs I don't like it nearly as well. |
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. |
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 |
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? |
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 |
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. |
Pryso, perhaps the Duntech's have different instructions than the Dunlavy's. I've just double checked my copy of the Dunlavy instruction sheet and the guidelines for speaker setup suggest distances that are not quite equilateral as a starting point. A D'Appolito array is indeed a MTM array, but all MTM arrays are not D'Appolito arrays. D'Appolito arrays require specific distances between those drivers and a very different cross-over than those used by John Dunlavy. I too had the good fortune to speak with John Dunlavy a few times and one time at some length. The audiophile community suffered a great loss with his passing. Please let me congratulate you on your excellent choice in speakers. |
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. |
Pryso, if I'm not mistaken John Dunlavy did not recommend an equilateral triangle and the Dunlavy's aren't a true D'Appolito array. |
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. |
Look up Dunlavy SC IV on you tube.
Usually adding spikes or points to the bottom of speakers is for increasing clarity and improving imaging. My SC IVs did not need improvement in these areas.
These are not near field speakers. The drivers are spaced far apart and in order to get a good blend of the drivers there needs to be a certain distance between you and the speakers. This could be the reason for the improvement you heard by spreading the speakers farther apart. These speakers can actually be spread extremely far without any loss of imaging detail.
Dunlavy, one of the best speaker designers in the world, did not believe in spikes. That's why he didn't supply spikes. He didn't believe in bi-wiring either, but he finally gave in and installed bi-wire connectors because reviewers and dealers hounded him to do it. I experimented with bi-wire and single wire. I felt the single wire was more coherent from top to bottom.
Wire used was Dunlavy speaker wire and interconnects.
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