... it looks pretty amazing how they can reduce / cancel
feedback. So obviously if this new high school has the money and can invest in this
speaker system I'm all for it. Sound is my weakest discipline and if these speakers work the way they claim to it will save me a serious headache while I'm trying to learn new ropes as well as equipment all while keeping the season going from a technical standpoint without constantly fighting
feedback.
1. Are there any of you out there who have witnessed demo's of these speakers or who have them in systems you currently work in or have worked in? If so, are they as good as they claim to be? FMEng is skeptical... Is there a negative side to going with these speakers that may not be well known? For the demo I will be a witness to are there any specific questions I should be asking, or specific situations I should ask the tectonic people to put their speakers in to see results? Keep in mind I have not worked in this
venue yet, just toured it and saw a small band perform for a few minutes.
2. It seems to me that moving the existing speakers
downstage to the front of the
stage extension should solve the
feedback problem and in theory should be way cheaper than going with an entirely new
system. Getting new stuff is great, especially in high school which is typically drastically underfunded and of course I'll take them if they tell me we are going that way, but just saying....
To clarify, the DML speakers don't reduce or cancel
feedback. What they do is
reduce the likelihood of feedback because there are not single point-source relationships between the speakers and the microphones in the same way that cones or horns do. The sound 'comes from everywhere' across the
face of the DML
driver panel which is different than what happens with a
conventional loudspeaker. The other contributing factor to their
feedback resistance is that they don't have a cross-over in the middle of the vocal band. The DML bandwidth is about 160 Hz up to well above 6-8KHz. Crossovers introduce
phase shifts, which create frequencies where the mic and
speaker are perfectly in-phase and facilitate a regenerative cycle. You can make a DML
speaker feedback, it is just more difficult to do so. This can give that extra 'margin of error' for inexperienced operators in challenging rooms.
In response to Question #1: I have heard the Tectonic speakers in five different types of rooms (
Black box theatre, Large movie-theatre renovated into a performance
hall, Classic 1920's style multi-balconied
theatre, a modern sheetrock-on-metal-studs
auditorium, and in modern sheetrock-on-metal-studs church with little diffusion). In each instance the sound was
clear and easy to understand, even when the venues were lightly occupied and there was little absorption due to human presence.
Questions to ask during the demo: This is more about getting a demo that matches your typical presentation situation than it is about sitting in a classroom and studying physics. If you have poor mics, don't expect a DML, or any new
speaker, to help change the situation. Plan on acquiring good new mics for your new sound
system, and maybe rent a few for your demo. This way you don't blame the speakers for the mic's problems (true for any
speaker demo). I have witnessed DML demos where the owner insisted on using a bad mic and/or wireless transmitter / receiver and then they complained that the speakers sounded bad. The mic was replaced and the DMLs sounded fine. The same is true for mixing consoles (yes, even the electronics of some consoles funk-up the sound), and particularly mixing consoles with digital plug-ins (one demo had a plug-in active that really made the sound awful, and once removed from the
system, sound was good). Don't plan on bringing your media player with a bunch of crappy
MP3 files and expect to hear a difference. Bring original recordings from your shows, or better yet, bring in real live actors, singers, musical instruments (acoustic types, not
distortion based electronic types), and lecturers to speak / sing /
play into the
system and listen to how it sounds in the furthest most seats. It is easy to get the middle seats to sound good for most
speaker demos, but it is the people in the back that suffer because they are hearing the most diffuse sound from the speakers interacting with the room reflections. Yes, more directional horn-type speakers will help to 'punch' the sound to the back of a room, but they do so at the expense of the sound quality (the 'honking' of horns becomes very apparent once you have experienced the non-horn DML approach to sound reproduction). Playing-back prerecorded sound tracks is not a good way to demo any
speaker. Listen to how live sound 'sounds' in the typical audience members seat.
Good room
acoustics will always help, however, solving room
acoustics problems is not always part of a sound
system upgrade initiative. The interesting thing about the way the sound waves that emanate from a DML
speaker is that it interacts with the room surfaces in a much less intense way. A good analogy would be to differentiate between the way a soft light source like a 2'x2' studio
wash light with a diffussor panel in front of them would shine light on a wall and it bounces off of it, vs. how a
ellipsoidal spotlight shines light (like a
horn) with a very hard
edge cut-off. Both lights can
bounce off of the wall and provide a specified illumination
level at the seats, but you tend to see (hear) the glare (harsh honk) from the
ellipsoidal (
horn) more noticeably coming off the wall. The best example of this I heard was in a deep (~100' from
stage to rear seating row) room with hard plaster walls. You would normally hear a lot of sound contribution from the wall reflections from a
horn type
speaker, but with the DML's this was inconsequential and the sound was still
clear. Traditionally, in a room this deep, a sound
system designer might have placed a row of delay
speaker about mid-way back so they could keep the back of the room levels up while not pushing the sound levels from the main speakers up into feed-back. This was not necessary with DML's.
Although some have derided the DML speakers of 'having no proof' or just being '
snake oil', they usually have not actually heard the speakers in a real room with a real sound source. Armchair
speaker experts can speak loudly about that which they know little, but if they would take the time to A.) Read the numerous truly scientific papers posted on the Tectonic web site, B.) actually listen to the speakers in a demo or actual installation, and C.) learn how to spell 'Tectonic', it might bring some credibility to their arguments. Sadly, since the
introduction of computerized modelling of sound systems with programs like
EASE, fewer and fewer people actually listen to speakers to make expensive decisions. The reality is that programs like
EASE are written to simulate the effects of
point source sound devices, not DML's. It is not currently possible to simulate the acoustic response of a DML in a room with
EASE. it doesn't make
EASE a useless tool for modelling
point source loudspeakers, but it is applying the wrong tool to the job. It is interesting that many of those that critique the DML's without hearing them are followers of the 'Don Davis School of Sound
System Design' where everything is based upon the Q of a
speaker. If you go back and reread the Davis' books and Pat Brown's explanations about Q and intelligibility, it actually reinforces the fact that a DML
speaker can provide good intelligibility.
Wide coverage angle is not necessarily a bad thing. In the Don Davis School of Q, we are taught to narrow the
speaker coverage angles so that the sound only falls on the seats and nowhere else. This makes designing
conventional speaker arrays that laterally
cover a room well enough to create a good stereo
image very difficult, so what you actually end-up with is the left half of the room hearing the left
speaker array, and the right half of the room hearing the right
speaker array. This does not provide a good listener experience for a majority of the audience. DML's can be cross-fired in a room to provide this coverage with little ill
effect in regard to the
feedback rejection (one of the reasons
conventional speaker arrays are pushed so far forward of the
stage is to try to keep the
speaker spill off the
stage and causing
feedback).
This is also true on the vertical axis. Typically speakers are mounted up high and the coverage
pattern is aimed down so as to get even coverage across the seating. This results in a mental
disconnect between where the performers are located and where the sound appears to come from. DML speakers can be set-up down close to the same elevation as the performers so the sound appears to emanate from the same elevation as the source, and yet not compromise coverage of the audience nor
feedback stability.
Also of note is that the Don Davis School of Q equations say you should have poor
feedback resistance with low Q wide angle speakers, however, the Tectonic DML's clearly show amazing
feedback resistance. If these equations are wrong, then how else are they wrong when it comes to applying them to sound
system design with DML's? Just because you can't fully explain something that work really well, doesn't make it wrong or bogus, it just means that the mathematics and computational simulation software hasn't yet caught-up to the reality.
If you are insistent that "Q" is the most important aspect to reduce
feedback, then you have to explain how an almost hemispheric coverage 'low-Q'
loudspeaker can be so feed-back resistant, as this goes against all of the Don Davis 'standard' sound
system equations. You can't say your equations explain everything and get this result.
If you are insistent that "Q" is the most important aspect to reduce
feedback, then you have to explain how an almost hemispheric coverage 'low-Q'
loudspeaker can be so feed-back resistant, as this goes against all of the Don Davis 'standard' sound
system equations. You can't say your equations explain everything and get this result.
If you are insistent that "Q" is the most important aspect to reduce
feedback, then you have to explain how an almost hemispheric coverage 'low-Q'
loudspeaker can be so feed-back resistant, as this goes against all of the Don Davis 'standard' sound
system equations. You can't say your equations explain everything and get this result.
As mentioned before, the Tectonic DML has no cross-over in the middle of the vocal range (or like some
conventional horn-and-cone boxes, that may have more than one
crossover point in that critical range), so the vocals and instruments that have dominant spectral output in this range between 160-8,000 Hz are not 'buggered-up' by sound coming from disparate drivers and skewed in time through the
crossover filters. The other unique attribute of DML speakers is that they create very little 3rd harmonic (odd order)
distortion. This lack of
distortion provides clarity usually masked by
conventional drivers. When you get to mix sound through DML speakers you have to start from scratch and unlearn may bad habits that you have acquired over your years of experience because many of the 'tweaks' that you are accustomed to placing on a mix are really just crutches to overcome the
distortion you have been hearing from traditional speakers.
The poster said "Getting new stuff is great, especially in high school which is typically drastically underfunded". Regardless of what technology you end-up with, you have to continually remind the administration that "they only get one change to make a good first impression". Each class, each game, each lecture, each and every presentation is a "first impression". If you lose your audience (be they other community members, staff, parents, or students), then the rest of the presentation is pointless. They have to be able to hear without straining to hear. Don't skimp on speakers, mics, or signal processors to keep the
system clear and free of
distortion and
feedback.