Search Results for: subwoofer

Subwoofer Delay Taper (Update 1)

Here is a quick preview of my next post. These plots contain concentric circles. Each represents a wavelength traveled from the speaker at 125 Hz (2.73 meters). The first one shows 7 speakers spaced at 1/2 wavelength (1.37m) and all set to 0 ms delay. The concentric are all the same for the 7 speakers and we can see where the beam will go – the top center, where all the speakers are in phase. The MAPP plot then shows you the result. We can also see where the nulls will be – the areas where the wavelength rings are spread all over.

The second set is the same speakers, same spacing but with a delay taper of .67 ms per box. So it’s 0.0, 0.67,1.33 …..up to 4.00 ms. At this freq this translates to 0, 30, 60, 90….. up to 180 degrees (30 deg per box). In this case the concentric rings are all different – because the delay sets up a different origin timing. (I will explain this better later – this is just a preview) Where is the beam going to go? Well it is just as obvious as the 0ms version eh?

all for now……………………….

Here are the answers to Matt’s question about what happens on the back side. It is a mirror image with the reflection going in the direction if the delay ===> Right.

front and back -Phase wavelengths 125 Hz 7x Line Source .67ms delay taper per box — Phase wavelengths in front and behind the array

front and back -MAPP levels with Phase wavelengths 125 Hz 7x Line Source .67ms delay taper per box — MAPP levels front and back with delay taper

Here is the same physical setup (67ms delay taper) at 63 Hz. The DELAY is the same (.67ms per box) but the PHASE shift is different – it was 30 deg per box at 125 Hz. Now it is 15 deg per box at 63 Hz. It will be 7.5 deg per box at 31.5 Hz – (not done yet). The concentric circles are rescaled to the 63 Hz size and recentered to the 15 degree increments. ( I will explain that later) Suffice to say – THESE CIRCLES ARE NOT A FEATURE OF MAPP. They are insanely (correct wording) detailed Autocad scaled drawings. There were derived by a simple 2304 step process.

This is a work in progress……….

Phase wavelengths 63 Hz 7 element Line Source .67ms delay taper per box — 63 Hz with delay taper

A Concise Article on Cardioid Subwoofer Arrays – by Steve Bush

By Bob McCarthy Leave a Comment

This article Tech Talk: Building Directional Subwoofer Arrays

Working toward consistency. was posted just today on the ProSoundWeb by Steve Bush.

Well written, concise, plain English and NO MATH!

(lo siento que no es Espanol pero tiene fotografias).

I need say no more. Geez. That was the easiest post I ever did!

6o6

SUB-ARENA-CPPS-WITH-DELAY-31HZ — Cardioid Subwoofer array in an arena

Cardioid Subwoofers

By Bob McCarthy Leave a Comment

A hot topic of discussion is cardioid subwoofers, so this will be the place to get that topic going. At the moment I will use this as a test to see if I can upload a few graphics from the book here. The first will be some pics that describe the behaviour of end-fire arrays.

The above figure shows the timing chain for a set of four speakers in the end-fire configuration. The basic principle is a game of acoustic “leap frog” where the rearmost speakers jump sequentially over the front unit. The timing is set up so that all four speakers are synchronised at the front of the 1st (the rightmost in the figure) speaker. This “in phase” situation causes the signal to sum additively in this forward direction. The phase angles shown at the right for 3 different freq ranges are color coded to reflect their position on the phase cycle (green = +/- 90 deg, yellow = 90-120 deg and red = >120 degrees. The key item here is NOT the exact phase angle, but rather the amount of AGREEMENT in phase between the 4 speakers. In this case 31 Hz shows perfect agreement at 98 degrees so the addition wiull be strong. 63 Hz shows 4 speakers all synch’d at 198 deg and will achieve the same effect.

Meanwhile in the rearward direction (shown on the left ) the timing chain reveals four speakers out of time as they move over the rearmost speaker. The 4 elements are all at different times and range over 17.4 ms apart. The phase responses also fall apart – ranging from a 1/6 cycle (65 deg at 31 Hz) to 2.16 cycles (125 Hz) and all sorts of values in between. These disparities in phase values cause the amplitude response to sum very poorly in the rearward direction, the intended result of the design. In sync at the front – scrambled at the rear. The side directions fall somewhere between and the end result is shown in the 3 polar plots at the bottom of the chart.

This figure shows an alternate spacing/timing configuration. Instead of a constant spacing (as the upper version shows), with a consistent delay timing, this config has a log spacing – and log adjusted timing. The leap-frog game is still played the same at the front – everybody in sync at the front cabinet, but thing play out somewhat differently at the rear. The difference is small but illustrates the options we have available to us.

This 3rd figure has a different twist to it. In this case the intent is NOT to have perfect synchronicity at the front of the array. Instead the timing sequence is set up so that they are slightly off – such that there is about a 90 degree spread at 125 Hz, 45 degree spread at 63 Hz etc. This creates a less than perfect addition at front/center – but causes a better addition at the front corners. The result is a flattened front and an overall triangular shape. This configuration was shown to me by Mitchell Hart way down in Australia.

SIM3 Optimization & Design Seminar at UC Irvine

By Bob McCarthy 9 Comments

We just completed a 4-day SIM3 training seminar in the south side of southern California. UC Irvine is located very near the ocean, which makes one wonder how folks could study when the surf’s up. It is also right next to John Wayne Airport. Naturally I flew in and out of LAX, and drove the hour down to the other airport. Why? Because I live in St. Louis, which USED to be an aviation town (ever heard of Charles Lindbergh, McDonnell Douglas or TWA? – all just museum stuff now.).

Bob McCarthy Sim 3 training UC Irvine Class time — Measuring, measuring, measuring

We had a good sized class of 19, including grad students and professors from UCI, some engineers for Creative Technologies ( a rental house specializing in corporate), some freelancers and two special guests: Daniel Lundberg and Jamie Anderson. There were 3 people (not including Jamie) who had attended my seminar previously and were returning. This is, for me, the highest honor and I am very grateful for the support of Will Nealie (whose photos are shown here), Chuck Boyle and Szilard Boros.

The Venue

We were fortunate to get to do the seminar on the stage of the 300 seat Claire Trevor Theater. This allowed us to measure first in the controlled circumstance of the near-field on stage and then work our way out into the house. As an added bonus we were allowed to measure (and re-design and retune) the house system, which had an up-to-date line array type system of 8 x Meyer M1-Ds.

The class moved along very smoothly. We covered LOTS of ground and the acoustics of the hall were very favorable so that students could get a look at what real systems can do in a good hall.

The class progresses in complexity over the 4 days, beginning with measuring a processor, then on to a near field single speaker, adding a subwoofer , near field arrays, distributed arrays and then out in the house where we design a full system and tune it. All the while the progression of complexity is underscored by the theory behind the data. The number one focus point of a SIM3 seminar is understanding what the data says and WHY they data says that. Proper diagnosis must ALWAYS come before treatment, and all treatments need follow-up testing. If they don’t work then get started on a new diagnosis. SIM school tunings are never rehearsed so when something shows up on the screen, we all are seeing the data for the first time. There are always surprises and this was no exception.

In the course of the tuning here we found that our original design had too much coverage for the room. If we had gone to MAPP On-line or even used a simple protractor on the plan view of the room this could have been seen in advance. But PURPOSELY we did not use those tools to find the answer. It is better for the learning process to see how unkowns can be decoded by the analysis methods. The “Main” array was 2 x UPJ-1P in a coupled point source, located at the house left stage edge. Our goal was to cover evenly across the room – a straight horizontal line along the 3rd to last row. As we measured the 1st speaker across the row we could see that it cover ALMOST the entire width…. almost. Adding the 2nd speaker was WAY too much, leaving it off, left us 4 seats short of the aisle. Conclusion: Our design was flawed. (This made it just like a REAL gig except that the designer’s ego was not at stake).

It is much better (as a learning experience) to use the SIM 3 Analyzer to prove the design was wrong and to force us to consider the optimization options that had the highest prospect for success. If only we could wave a magic wand an turn this 80 degree speaker into a 50 degree speaker! Oh….. WE CAN! In this case we rotated the UPJ-1P horn on the 1st speaker (they are 80×50 rotatable) so that we got 50 degrees of horizontal coverage for the “A” speaker (the longer throw). This covered enough of the room to make a successful, smooth transition to the B speaker. Then we added the “B” speaker – too wide again until we rotated its horn as well. The end result was even coverage across the straight line of the 3rd to last row within 1 dB. The process involved measuring on axis, at crossover and off axis until the splay angles were optimized, the eq’s set (individually and together), levels set and delayedso they were phase-aligned at the crossover. Then we added the subwoofer to the array in both an overlapping and non-overlapping mode (different delays were needed for this). Finally we added a small delay speaker to extend the coverage evenly into the corner. We even took a few minutes to show the effects of adding excess delay (the side effects of the Haas Effect) and watched as the coherence and combined level at the delay location became worse than if the delay speaker had been turned off. This is always an eye-opening moment at my seminars.

Tuning (and retuning ) the Line Array

Because the class moved along so quickly we had the luxury of extra time to take on the house system. This system is made available for students to re-design, re-hang, re-angle, re-tune, re-etc……. This particular config had been specified by a student AMA (against medical advice) so the professors were quite interested to see how it would look under the scope. The answer: ________________________flat line.

The horizontal orientation was the most severe in-tilt I have ever seen (OK I am pretty new to this but I have seen a FEW systems). It was such an inside job that the Left side of the PA missed most of the…………. left side. The mix position was in the very rear of the house right side. From a horizontal standpoint the left speaker was pointed at the right wall IN FRONT of the mix position. If you are having trouble visualing this here is a pic to help.

UC Irvine -Theater view-Speaker positions-1 — Horror-zontal aim points for the PA

So we measured and found that the left cluster was more than 6 dB louder on the house right than on the left. Obviously the speakers would need to be opened outward.

Before- ONAX A vs OFF A - Off mic is near top row at the last seat on house Left

We had, however, spent the previous 2-speaker tuning focused on the horizontal plane interaction between the pair. Here we had 8 boxes in the vertical plane– that is what we wanted to see – and we had 5 mics running from top to bottom in a diagonal line where the speaker was pointed. As it stood, nobody knew what the current vertical angles of the cluster were. We had the 8 boxes wired in 3 zones 3-3-2 as an ABC array. It was offered to bring down the array and see the angles – then we could play in MAPP and see the response…….NO, NO, NO. Much better to turn it on and see what we have. This way we can learn how to hunt down an array in the wild. We know these 3 subsytems are out there – but where?

I don’t recommend working on systems where you don’t know where the speakers are pointed, but it is important to be able to find where they actually ARE pointed – even if you have a piece of paper (or I-pad) to show you. The learning experience here was the process of finding. Here is a pic to get the idea of where the mics were:

UC Irvine -Theater view - mic placement — Mic placement strategy

Terminology sidebar – ONAX (On Axis), X (Crossover), VTOP (Vertical top),VBOT (Vertical bottom).

Before we get to any tuning, we dummy checked each mic and speaker to make sure we had everything wired right. In the course of this we set the delay compensation for each mic and they ran from around 50 ms to 13 ms so we are looking at near seats that are around 12 dB closer (a ratio of 4:1) than the rear seats. The array will need to overcome this difference in proximity.

So we began with just the upper system “A” on (the top 3 boxes). We compared Onax A, VTOP and XAB positions. VTOP (around the mixer ) was a disaster. No HF, no coherence and the far side much louder than the near side.

Before- ONAX A vs VTOP — Original angles - ONAX A vs VTOP

UCI M1D R1 - VTOP A Solo -before EQ-captions — UCI M1D R1 - VTOP A Solo -before EQ

Perfect mix area!!!!! XAB was down slightly from ONAX A so now we knew (vertically) where “A” was pointed: Too low.

The cluster was already very high so we can’t move it much. The real answer would need to be getting some up-angle in the array. This would require some real-world rigging and this was not going to happen in our short time frame so it does not seem that we will fully solve the mix position.

Onward. We moved the ONAX A mic up and down a row and found that our original position had the most level – we had found the center of A. We eq’d it and stored it as a reference level.

Next begins the search for B. We looked at the ONAX B mic and moved it up and down until we found its high-water mark. The level at B was stronger by about 3 dB (compared to A). It was also about 3 dB (70%) closer. This made it obvious that the splay angles chosen for this array were wrong. How did we know? The job of the different splay angles is to create a matched level at different distances. Here we were seeing that as we got closer, it got louder – the expected propeties of getting closer to a symmetric, non-directional source, not one that is creating asymmetry in the vertical plane. We eq’d the B system and reduced its level 3 dB.

Next up was the bottom two boxes, system “C”. This system covered the front rows REALLY well. It was 7 dB louder than at the back and we were still in the 4th row. It got even louder up closer but we gave up.

Conclusion: The cluster system needed to generate around 12 dB of level difference from top to bottom. It actually achieved 3 or 4 dB. Time for the cluster to come down and redesign the system.

Redesigning and retuning the Line Array

We have no drawings of the room. Not even a napkin sketch. The UCI internet is not getting through to my laptop. We are going to have to go it alone.

This is what we know (a) the cluster is too low, we have more than enough angle to reach the bottom and we need 12 dB more level at the top than the bottom. This means that the splay angles for the C section need to be at least 4x wider than the A section.

So how do you design a line array with no Manufacturer Official Line Array Calculator, no Mapp On-line, no drawings? We need to know the angle spread from top to bottom, and the difference in range from top to bottom. So we looked at the existing angles and found that the overall angle spread was 40 degrees. We know that was more than wide enough. We know we have a 4:1 distance ratio.

So we need 35 to 36 degrees of spread – we have 8 boxes (7 splay angles) – the average splay angle will be 5 degrees. (5 deg x 7 = 35 deg). We know the widest angle we can get for an M1D is 8 degrees. If we have 8 degrees at the bottom and 2 degrees at the top (a 4:1 ratio) we will approach our 12 dB range ratio. Add ’em up (2-2)-3-(6-6)-(8-8) = 35 degrees. System A = is 3 boxes at 2 deg (a 6 deg speaker), 3 deg splay to system B (a 12 deg speaker) and then on to C (a 16 deg speaker). Here is a picture of the design in progress: Yes – that is the AS-BUILT paperwork under my hand.

Design in Progress — Calculating the splay angles based on range ratio

The new angles were put into the cluster and up it went – pretty much as high as it could reasonably go (about a foot or two higher than before) and we resumed measuring. This went very quickly now. The center point of each subsytem was easy to find since they each were made up of a symmetric angle set. The center of A was at cabinet #2, the center of B was at # 5 and the center of C was between 7 and 8. Each system was eq’d separately and levels set. The level tapering needed to bring the lower systems into compliance was 1 and 3 dB respectively, a far cry from the 3 and 7 dB previously. The systems were combined – first A & B and then C was added and a very uniform frequency response and level was created over the space. The level from front to back (back being the top row) was now 1 dB. The mix position still sucked – but we knew we could not save that without a rigger.

Bob McCarthy Sim 3 training UC Irvine - Revising the angles-red — Reworking the angles

First we looked at the ONAX A position, and EQ’d it. This will be our level/spectral standard going forward.

The next step was to look at the response at the mix position. We expected that things would not be improved much here since we were not able to aim the array up high enough to hit here……..and we were not disappointed. Well I mean we were not surprised.

After- A at ONAX A Compared to A at VTOP

After- ONAX AB Compared — After - Response of A solo at ONAX compared to B solo at ONAX B

The EQ applied is slightly different for A and B respectively. The difference is minor because both “speakers” are comprised of 3 elements. The splay angle is different which creates a different summation gain of 3 dB – the correct amount to compensate for the difference in distance.

After- A at ONAX A Compared to AB at ONAX A

Above – You can see the addition at A that occurs when B is added. The response shows no loss but the gain varies with frequency. As frequency falls, the percentage overlap increases and the addition increases. At 8 kHz the percentage overlap is so low that we see no addition. By contrast, at 125 Hz we see 6 dB addition. All frequencies between show gain values between 0 and +6 dB. This is a great example of 3rd order speaker behavior.

After- HF ZOOM - AB at ONAX A ONAX B and XAB

Above is a zoomed look at the uniformity of the HF levels.

Combined System A+B EQ

Once A and B are combined we look at the LF region to see where the coupling was shared in both directions. Frequencies that were boosted in all locations can be equalized by matched filters in the A and B sections. In this case a 160 Hz filter was applied. Below we have a zoomed in comparison of before and after the AB Eq was added.

The screen below shows how we have restored the Combined AB response to the same shape as our initial A solo reponse.

After- AB at ONAX A -Combined system EQ compared to solo A EQ

The AB sytem is now complete

After- AB with combined EQ at ONAX A ONAX B and XAB

Combined System: Adding (AB) + C

Now that AB is complete we turn our focus to C. Speaker C (2 boxes) was EQ’d as a soloist and it’s level set to match the ONAX A standard. The solo EQ response appears below.

: After- C at ONAX C EQ and Level

The response below shows the full combined response ABC at ONAX A and C positions, giving us a clear view of the difference between top and bottom (not much!). The distance ratio between these two locations is around 8 dB!

After- ABC at ONAX A and ONAX C - top to bottom compared

Finally we sell the full system ABC at its 3 main locations.

After- ABC at ONAX A B and C — After- ABC at ONAX A, B and C

Was this the best way to design a system? I would not recommend it, if you have the option of drawings etc. But in the end we still have to test it – and that is where the final design comes from. In this classroom setting we made the tuning process drive the design. What we learned from our data was translated into an updated design and this was then measured. The result was a winner. This process, in a few hours was a distillation of 25 years of work for me. Everything I I ever learned about design came from the process of trying to tune an existing design, and learning from it.

There are additional class photos which will be placed in the “Seminars” Page on the right of this blog page.

and finally………………….

I did manage to bring home some good data from this tuning so I will add those to this post later. Soon… I promise.

6o6

Macau COD Tuning: Day 6 – Constellation

By Bob McCarthy 3 Comments

Constellation Tuning

Most of today was dedicated to Constellation tuning. Steve Ellison programmed up the menu of user-settable presets that will become the painter’s pallette for the system designers, Francois Bergeron and Vikram Kirby. The pallette gives them easily understood parameters such as the the reverb Time, gain, etc, that will allow them to tailor the response of the sound system/room to the music and spectacle as the creative process unfolds.

The beauty of electroacoustic architecture is that the acoustics can be reshaped from song to song, gradually so that the audience has no conscious awareness or the opposite: a dramatic moment to create a strong conscious effect. The settings can be made completely plausible for the shape of the space that you see around you, or can be dryer and more intimate than you might expect or, of course, much larger and more reflective. Once the lights go down, the mind loses sight of the scale of the performance space, and creative minds can begin to operate on rescaling the room to most appropriately contain the soundscape.

Imagine yourself having the ability to pull down a wall of thick curtains in a small room and reveal the walls of the Notre Dame Cathedral behind them. This is the level of capability now in the hands of the system designers. This is NOTHING like having a Lexicon at FOH. I use this simple analogy: A dry room with house reverb puts the singer in the shower but leaves the audience watching from the desert. (Who the singer is that you imagine in the shower I will leave up to you). All the reveberation is in front of the listeners, and the room acoustics clues of spatiality are missing. A room with electro-acoustic architecture puts us ALL (audience and performer) in the shower, desert, or something in-between TOGETHER. The spatial clues are there – precisely because they are ACTUALLY there. An audience member’s clap will reverberate from the “walls” just as the performers do – this absolutely will NOT happen with FOH reverb.

Yes it can happen with actual hard walls – but walls only have one setting. Yes it can happen with variable acoustics (moving panels, drapes etc.) such as we see in some modern concert halls. But the Constellation system does not require a four hour labor call to open chamber doors, drop in curtains etc, to move a hall from highly reverberant (symphony) to less reverberant (chamber), or to extremely reverberant (organ). Constellation can move in seconds, with a single click (or cue) from dry enough to feel a tight, pulsing, fast-paced drum beat all the way to cathedral chanting (and very importantly, the land between).

It is no coincidence that this capability was designed into this system. Francois Bergeron has been an expert in complex spatial sound systems for all the years I have known him. After all he is the guy who programmed “The Little Mermaid” show for me at Tokyo Disney Sea, where an entire orchestra is swirls around and goes down the drain. It has been running there every 20 minutes since 2001.

Hopefully you get the idea. What Steve, Pierre and I will leave Vikram and Francois with with will be a simple web page with programmable presets which can be logged in as cues in LCS. Then the fun begins, integrating this into the production.

SIM Tuning – Leftovers

In addition to Constellation tuning there were a few leftovers from our previous tuning work. We had to check the 28 Melodie boxes of the 4 opposite side clusters. The fact that we waited this long for this step lots about the quality of the install by Solotech. The very small number of wiring/install issues gave us high confidence that these clusters would be in good shape. 28 speakers checked: 28 speakers good.

The fact that we did not have to reposition any of the 8 clusters or modify any of the inter-box angles says lots about the quality level of the Thinkwell design team. Anyone reading this who has been on a job site where I did the SIM tuning knows what the odds are that speakers are going to SUBSTANTIALLY moved is: very high. In this install there were 56 Melodies (Mains), 23 CQ-2, 32 UpJunior, 43 UPM-1P, 32 MM4-XP (Surrounds), 10 600 HP (subs) and 24 UPJ-1Ps (Constellation) that required NO REPOSITIONING OR ANGLE CHANGE. The cardioid configuration of subwoofers was re-angled to make best use of its cardioid steering (a very simple job for the riggers). Only the Soundbeams had to be moved (two meters rise in level and angularly adjusted) – again a minor change in the big scheme of things. Hats off to the Thinkwell team for excellent design work and to the installers for putting it in like the plans.

Sound beam discovery

The design goals of the SB-2 are quite challenging: to cover the opposite side of the circle -without disturbing the near side. The intent was not COVERAGE in the traditional sense – as in – sound or NO sound, but foremost for vertical image control. This is where scenic design adds a challenge: a shower curtain. Yes a thin plastic sheet around the room perimeter to obscure technical areas, catwalks etc. The SB-2s are behind it. Acoustically transparent, of course….. kind of. We measured with the curtain in place – and pulled back – 6 dB loss from 2k Hz on up. Result: we have to drive the HF harder to get to the other side. Result: splash and spill on the near side is stronger than desired. Result: Adjusted the tilt angle up to reduce the level on the near side. Result: Better but still not optimal. Decision: Riggers will move the SB-2s up 2 meters during the daytime tomorrow and we will reset the angle down and try again.

More Verification: Opposite side line subwoofers

The verification proofing technique makes use of symmetry of the room. We placed mics at opposite sides and stored the individual responses of box 1 to 5 with its mirror opposite. 1 polarity reversal found.

Still More Verification: Underbalcony speakers 8-32

Level and EQ were verified as matched to each of the remaining UB speakers. Delays were adjusted individually for each because the geometry of the Mains and Ubalcs, as constructed do not make for an absolutely concentric pair of circles. The differences overall ranged about 3ms over the 70ms of approximate range. To have a system designed to able to be tweaked to this level of detail is something you just don’t see every day………. or pretty much ANY other day. Wow!