Stereotypen skrev:Hi, and Welcome Jacro!
Very interesting ta read about your study of amplifiers/loudspeakers!
I am interested to hear what you think about Siegfried Linkwitz approach to loudspeaker design, dynamic dipoles.
I myself have found them to solve a great deal of the problems in the speaker/room area in my listening room. The uniform powerresponse may be part of the answer here i guess.
What are your experiences or oppinions regarding this?
Hi Stereotypen,
I have great respect for the work that Linkwitz does and the generosity he has come to exhibit by sharing so fully on his website. (He was much more guarded with information in his younger days.)
You are correct in assuming the importance of uniform, or at least carefully tailored, power response.
My general recommendation is that once one has established an effective direct sound, with minimum interference from early correlated reflections, then the ideal is to have the best full range balance possible on all secondary room sounds, preferably with the appropriate delay between the direct sound and correlated reflections.
To achieve this, I believe the loudspeaker should either be operated as a boundary coupled half-space device, or as an omni or full range dipole well out into the room.
(These out-in-the room, symmetrical dipole, systems work best in larger rooms, so as to be able to be well removed from the front wall, and sidewalls. Small rooms do not accommodate them very well, particularly the more omni-directional devices. Dipoles can be oriented to aim the dipole nulls at the sidewall and front wall first reflection points to minimize early reflections to help work better in a smaller room, but that is still a compromise.)
Unfortunately, most loudspeakers operate in the awkward middle ground between these two approaches. Most (cone in a box) loudspeakers are operated a short distance away from the front wall, but they have omni-directional response at all lower frequencies, and more directional sound in the upper frequencies, with “uneven” power response creating an unbalanced “room sound”. The “rear 180-degree wave angles” tend to exhibit very uneven, frequency response and drive the room to an unnatural secondary sound field.
While I feel the half-space, boundary-coupled approach is the more universally consistent way to achieve the best effect, the Linkwitz approach can also provide a very good result, particularly if the room size is compatible. The equal front/back response at least drives the room in a manner that is consistent with the direct sound, but there are some questionable side effects, such as artificial reflections off the front wall behind the loudspeakers, often creating interference with the direct sound, and also creating “false depth”.
False depth can be an enjoyable effect, but it does not represent an accurate mapping of the original event into your room.
Only recently has Linkwitz finally arrived at making sure that the dipole response is equal on the front AND backside of the loudspeaker. Previously, he only operated dipole up to approximately 2kHz, but now he has adopted full symmetry.
If one is putting a loudspeaker out into the room, it must be either very symmetrical, preferably with constant directivity vs. frequency, and even better, constant “high” directivity with frequency, or it must be power response tailored in a very careful manner.
A few loudspeakers that don’t follow the guideline (of symmetry or half-space), can be made to perform well, but must be tailored very carefully to be successful (Quad ESL 57).
Otherwise, to work well, they should be used in the near field, eliminating room sound as much as possible (Harbeth HL-P3, LS3/5a).
Again, all of this is an over simplification, but as a guideline, but hopefully, it at least points to some of the issues that must be dealt with.
- James
) ! 
)
