Reva

Published 2017-01-18: https://www.soundonsound.com/news/rode-announce-six-new-mics-soundfield-video-mic The originally presented prototype looked different from the more recent one discussed above which shares some mechanical body similitudes with the SVMX.

The cylindrical Li-Ion cells I was referring to are max. approx. Diameter 19 mm x Length 66 mm (mass: 44 g) and one cell can power the device for about 35 h. Indeed I expect that the power required to generate the timecode (as long as no LCD backlight is on) to be so small that it won't affect the discussed figures. With a 4-cell battery you could power the device during 140 hours (or 5 days and 20 h non-stop). Using supercaps would allow comfortable time to hot-swap batteries while device is kept running normally. (I was referring to the bare battery cells, there's some small overhead for the case and and cell protection circuits.) Now obviously it won't work if used permanently in a GNSS-denied environment but if being able to work over 5 days (and more if a larger battery is used or if the battery is hot-swapped) in a GNSS-denied environment wihtout having to worry about any timecode issue using various equipment could still be interesting. The wireless-synched TC units you refer to are different as they still require synching (not based on an absolute time reference like UTC which can be acquired independently) and probably also feature less precise oscillators (to be verified but I'd be surprised if they use oscillators in the 0.1 ppm class (full operating temperature range)). If a local oscillaror drift of 9 ms / 24 h is too large better oscillators can be used but costs and power requirements are increased. BTW no idea why many timecode generators aren't very precise, maybe it's just a question of cost. The 0.1 ppm precision I mentioned is based on quite inexpensive oscillators. A 50 times more precise oscillator module can be used but it's more expensive and requires up to about 2 W (depending on the ambient temperature). Board size isn't much an issue, the battery is much larger.

A few details of the aluminum body, like the camera shoe mount and the 9 V battery compartment, look very similar to those of the Rode Stereo VideoMic X (SVMX). No idea about the price but my random guess would rather be in the same range as the SVMX. I expect that inside the camera shoe mount is machined a female 3/8" thread like with the SVMX (thread is compatible with boom poles, stands and other accessories). Also referring to the form of the body I'd expect a pop shield and maybe also a wind shield (deadcat or dead wombat as Rode calls it). Referring to the picture I can't see if those two accessory could even be the same as for the SVMX, will depend on the required inner dimensions. That said I'm very surprised that this mic has already been anounced about one year ago and is still not available.

If we take as example a single cylindrical Li-Ion battery cell of a very common type "18650" with following specs: - Nominal Voltage: 3.6 V - Capacity: 2.9 Ah - Diameter: 18.6 mm, Length: 65.2 mm, Mass: 44 g the energy storage capacity would be (ignoring losses): 10.44 Wh = 0.01044 kWh = 37584 Ws = 37584 J. The basic power requirement would be around 140 mW but we need some power margin for battery management, stabilizing DC/DC and a more or less sleeping general purpose low-power processor. Lets's add 60 mW, so the total maximal power would be: 200 mW = 0.200 W. As batteries specs are usually too optimistic, let's derate the battery by about 30 % so we can consider 7 Wh per cell (also a low discharge rate application allows higher battery efficiency than short discharge times). Doing so with a single Li-Ion cell: 7 Wh / 0.2 W = 35 h of standby duration (maybe with active LCD display but without backlight). Using for example 4 cells we'd get 140 h of standby (i.e. only running the internal clock and GNSS receiver). As the generated timecode signal is of very low power I don't expect power requirements to be much higher when actively using the device for timecode generation, though using a LCD backlight could draw significant power, especially when set for sunlight readability. Of course the generated code is a matter of firmware and the user should be able to decide about code details. Ideally there should be an incentive for a standard and indeed I'm very surprised that users and manufacturers haven't proposed anything yet. The main benefit would be to allow each device to handle timecode totally independently. Wireless short-range (i.e. very low distance, maybe up to a few meters) sync could be imagined using a portable unit when some sync device would be left on a camera and never be able to receive GNSS signals. The one-time sync precision would be slighty lower but the expected error would still remain way under 1 millisecond. Referring to time units, it's merely a question of conversion and with current low-power-consumption proccessors it's very easy to calculate sync data using odd units with a precision far beyond the required one. Basically the precision will be limited by the timing reference accuracy but not the precision of timecode computations.

I don't shoot videos using DSLR, but with the body I used to check mechanical noise, especially due to the lens and when settings are changed manually on the DSLR (for example rotating the main or sub dial), will not allow a satisfactory sound quality with a hotshoe mounted mic. IMO even using a shotgun with Rycote lyres camera noise will still be a problem (here not discussing the basic pros and cons of using a hotshoe-mount mic as such). Possibly other cameras and lenses are less problematic but I don't know as I haven't checked it. I used several constant aperture f/2.8 zooms and all cause some slight noise even if focusing manually and disabling optical stabilization, old lenses with direct mechanically acting focusing ring are nearly silent but the ident noise of the aperture ring will mostly still be heard and the issue related to operating camera controls remains. If not mechanically connected to the camera there are no handling noise issues with the SVMX as long as it's handled carefully (can even be handheld but it's not very convenient, using some grip with a 5/8" thread or 1/4" to 5/8" thread adapter or a boompole will be safer and more convenient.

RFI sensitivity highly depends on the used GNSS receiver, there are more or less advanced anti-jamming techniques, both based on hardware and software solutions. I expect that modules like the discussed ones to perform well enough in presence of RFI levels like the ones you're referring to, especially also because you don't need continuous time solutions. For the other issue, signal obstruction leading to GNSS service denial, while some receiver/antenna combinations perform better than others, there is obviously no universal remedy. IMO practical tests should be done in order to determine if this factor is critical or not as well as for RFI/EMC. What would be considered as acceptable clock drift per 24 h? I mentioned 9 ms per 24 h worst case but it would be less if temperature variations are lower than 125 K. The required power is quite low (max. 140 mW with GNSS receiver and local oscillator running) so the idea would be to keep the device running 24/24 7/7.

You're welcome. I just tested the Rode Stereo VideoMic X mounted on a DSLR hotshoe to check mechanical noise issues but I used an external recorder with 48 V phantom power though levels are compatible with typical DSLR external stereo mic inputs and there's a pushbutton to cycle through -20 dB / 0 dB / +20 dB which affects both 3.5 mm TRS and Mini XLR outputs. Cycling is always in the same order which means that for example when 0 dB is set and you want -20 dB you first get +20 dB after pressing the pushbutton once and pressing it again you reach the -20 dB setting. The unbalanced 3.5 mm TRS socket stereo (indeed it's dual mono, one per capsule) output is available also when Mini XLR (also called TA3F (F for female) or sometimes Tiny XLR) are used. I didn't check it for unusual conditions like only single phantom power or low battery. Didn't check if there are audible differences between Mini XLR balanced and 3.5 mm TRS unbalanced. It would be possible to dual record "stereo" (or more exactly "dual mono") using both Mini XLR as well as the 3.5 mm TRS "dual mono" jack but I don't expect it to be useful, if phantom power is available it should be used and there is only one preamp per capsule so in case of a preamp failure both balanced and unbalanced outputs will probably die together in most cases, not even mentioning the lower RFI performance of unbalanced cabling. Further, 3-pin Mini XLR, though being much more fragile than regular XLR, still feature a locking mechanism (not sure if it works with all common female cable connector models). If dual recording is required, typically with some preset level offset, it should rather be done internally by the recorder using 2 mic input channels rather than using 4 mic input channels. The aluminium camera hotshoe mount features a 5/8" threaded hole which is compatible with usual threads of boompoles, photo/video and lighting accessories (not to be confused with the smaller 1/4" threaded hole of common video and still imaging cameras but there are thread adapters). Overall the aluminium case (including an aluminium battery compartment door) is well built but the protection of the XY caspules still is quite limited even if using the pop shied or wind shield. If handheld carefully with some generic grip, or boompole-mounted, there are no handling noise issues (just tighten the mount locking knurled aluminium ring even if not used to avoid rattling noise), I mean not more than with other lyre-mounted mics. IMO it's some sort of compromise between fragile toy-like DSLR hotshoe mics and commonly used professional stereo mics. It's relatively expensive but OTOH some features can be useful and it's also relatively compact. For storage I'd highly recommend to get some foam-padded hard case like Peli or similar ones. The pop shield can be left mounted for storage but shall not be compressed. Don't know if the OFF/75/100 Hz high-pass should be used or if it's better to use the recorder HPF or handle it in post. The same applies to the OFF/+6 dB high boost to compensate some windshield attenuation of higher frequencies. When changing dB, HPF or high boost there's some short clearly audible parasitic noise. Make sure the used 9 V battery slides in and out very easily, don't even force it slightly in place or it could be difficult to remove it later (a small 90° hook made of a needle could be used to remove the battery, it will damage the bottom of the battery but not the mic). The battery I used slided in and out very easily. I'd recommend to use a battery as backup in case of phantom power problem. Presets are remanent even without any power but I didn't check if it's indefinitely or only for a limited time with some capacitor. The nearly flush mounted temporary action pusbuttons are not very prone to accidental actuation and to power on the 0/I button must be pressed during slightly over 1 second (estimated). Never carry or even lift the mic by holding the pop shield or wind shield, the shield will easily slip off and the mic could fall on the ground. While I'm not an expert I'd mean that it's mostly for ambient sound, certainly not for dialogue nor music but it not intended for such uses. About the noise floor and possible L/R level mismatch I must check it more in detail. As I tested it quickly again I noticed a sudden increase of noise level in one channel, I verified that it wasn't related to the cables, recorder, RFI or so but suddenly the noise disappeared and levels were matching again correctly. I'll have to further test but I'm nearly sure it is related to the mic as I used an other pair of XLR inputs and also reverted to battery power, switched again phantom power, etc. Those interested should try to test the mic as YouTube and other videos are mostly not a very good reference especially as mostly DSLR or other lower end recording devices are used and other technical issues which make comparisons difficult. Maybe someone could comment how the Rode Stereo VideoMic X performs compared to known XY capsules (handheld recorders, etc.).

I was referring to UTC because it's a universally available reference, there are not issues related to time zones, daylight saving, time corrections or so. The precision I mentioned corresponds to the specs of relatively cheap modules which can easily be integrated in a design, lower precisions won't allow much lower costs and higher precisions are only required for special purposes (maybe genloc or sampling clock reference), in such case maybe 100 to 300 US$ should be added for a much more precise oven-controlled internal oscillator. When GNSS timing is available the time base precision exceeds requirements for sampling and genloc but jitter requirements should be verified. Generating the time reference as I mentioned it does not require complex hardware, from there the used code can simply be either UTC or an arbitrary offset from UTC (though there remains the midnight roll-over issue mentioned by Mungo while true UTC is univoque). I'm simply surprised that no time code standard based on UTC has been proposed, manufacturers and users could simply be offered the option to use either common timecode as usual or an absolute UTC version. To ensure interoperability, the usual timecode shall always remain a possible option, either as UTC offset or with common local (UTC independent) generation and snyc. As the discussed GNSS time reference modules are relatively recent so comparisons shouldn't be based on older similar devices. Performance of the whole system depends also on the overall design including the antennna.

The Rode Stereo VideoMic X can be powered by an usual 9 V battery and/or with 48 VDC phantom power through the two 3-pin MiniXLR male sockets. I didn't notice any difference between dual phantom power and a new 9 V internal battery but I couldn't test it thouroughly. When battery power is low (wihtout any phantom power provided), Rode mentions that mic performance is degraded. The power LED turns red (if power is good it's green when the mic is ON, obviously when OFF no LED is lit) and I suppose green LEDs are dimmed. Gain and filter settings are remanent even if not powered at all (battery removed, no P48). When both phantom power are present the mic operates on phantom power even if a good 9 V battery is installed (according to the manual, not tested). When one phantom power is lost (wthout any 9 V battery installed), the green LEDs are dimmed and the power LED turns red. Doesn't matter if Left or Right phantom power is lost. I suppose performance is degraded like if battery power is low (not tested nor documented). Now as I tested it I noticed an odd not systematically reproductible error: Normally when one phantom power is lost (no 9 V battery installed), both L and R audio outputs are usually still available though in some cases only the phantom powered one remained available while the other one was muted. When a good 9 V battery is installed, if one or both phantom power are lost, the mic reverts to battery power (no LEDs are dimmed and the power LED remains green) but switching on or off any phantom power causes shortly an audible noise. If a 9 V battery is installed and only one phantom power is lost it's not specified if the mic is powered only by the battery or only the channel without phantom power and if the battery level plays a role (i.e. when the battery is low but still useable if the mic uses only single phantom if the 2nd phantom power is missing). I also noticed a quite audible level difference between the L and R output but I must check it more in detail. No idea if the high frequency boost should be used when using the provided windjammer or if it's better to boost in post. The Rode Stereo VideoMic X is delivered with a clip-on elastomer/foam pop shield, a clip-on wind shied (windjammer, some sort of deadcat) and a 3.5 mm male/male TRS short spiraled red cable. Warranty is 10 years if registered. Unfortunately no MiniXLR cables are provided. Approximate weights as I measured them (with 9 V battery installed, no cables): - Bare (no wind shield, no pop shield): 318 g - With pop shield: 354 g - With wind shield: 379 g With some care it can be used without wind nor pop shield though it's better to leave the pop shield on as it's like a soft elastic ball offering some basic protection. Only one shield can be used at the time, both shields are simply pushed in place and hold by friction. Unless bumping in something they shouldn't fall off. As I tested the mic with a DSLR I didn't find the weight to be an issue, the DSLR alone being about 2.5 kg with the basic lens (not a tele) but despite the Rycote shock mount I wouldn't use it on-camera as it easily picks up mechanical noise; even when focusing manually, there's a slight mechanical lens noise which can be heard. Also drive noise can be heard when lens aperture is changed. I'm referring to noise made by the lens mechanism itself, not due to the manual handling. Of course handling noise will also be audible, changing some settings caused annoying noise (for example turning some main or sub dial). IMHO the RF immunity is not as good as claimed, cell phone interference can easily be heard (using balanced XLR and it's not related to the used recorder), at least compared to the RF biased Rode NTG3 shotgun mic which is extremely RFI robust. Holding a cell-phone transmitting at maximal power directly against the NTG3 does not lead to audible interference while with the Rode Stereo VideoMic X the interference noise level is very high with the same test. I forgot to mention that autofocus is way too noisy also I never used autofocus with any video camera. I've no experience with DSLR video, I formerly used some 1/2" and 2/3" 3CCD ENG cameras both with integrated and detachable recorder but that was quite some time ago (all Fujinon and Canon lenses I remember were manual focusing, modern DSLR lenses are awfully bad to focus manually and overall ergonomics don't make DSLR suitable for video unless using very odd cumbersome rigs but that's just my POV).

Thanks for your replies GNSS, which simply means that in addition to GPS, where available, other satellite navigation systems are also used, typically the Russian GLONASS, the other ones not being fully operational yet. For the user it's totally transparent and receivers track as many satellites of any system they can receive and decode (at least within the maximal number of satellites data channels a receiver can track simultaneously). Many receivers are designed to simulatneously track many more data channels (up to 400 or even more) than they can actually receive. More advanced receivers allow shorter times to first fix (TTFF, i.e. how long it takes to compute a position solution after a total loss of signal). The timing accuracy of GNSS positioning systems is very high, which allows simple GNSS modules (costing a few US$) to be used as time reference with a precision way better than one millisecond. The precison of a GNSS-disciplined time base is mostly limited by the precision of its local oscillator when GNSS sync is unavailable. DCF77 (https://en.wikipedia.org/wiki/DCF77) is useless for precise timing, it's widely used for basic clocks and also for industrial purposes and computer networks not requiring a precise time alignment because the required hardware is trivial and the decoding is extremely simple. As cheap GPS modules are now available it doesn't make sense to use any other RTC clock sync as long as it's possible to receive the signal. With a relatively inexpensive basic GNSS time reference module integrating a local crystal oscillator a typical absolute timing accuray of about 20 ns (optimal conditions) and 500 ns (indoor) can be achieved (1 nanosecond = 0.001 microsecond = 0.000001 millisecond = 1E-9 s) in GNSS-disciplined mode. In a GNSS-denied environment, i.e. where reception of satellite signals doesn't allow the processing of a valid UTC solution, the time reference issued by the module is based on its local crystal oscillator. In such case the timing accuracy drops to 100 ppb per 24 h (0.1 ppm or about 8.6 ms per 24 h), the effective precision will be better as the mentioned value applies to the whole temperature range of -40 to 85 °C (-40 F to 185 °F). The required power in any mode doesn't exeed about 140 mW (at 3.3 VDC) and the mass of the bare module is around 2 g so it could certainly be integrated in battery-powered portable recorders or timecode generators. Only for small hanheld portable recorders the power could be too high but the whole device could be shut down simply relying on resyncing after each power up. Cold start acquisition time (TTFF, see above) depends on how well satellite signals are received and is typically around 10 to 30 s (some satellite constellation data is temporarily stored to allow faster cold starts than about 30 s but only if that data is not too old). If GNSS is available the clock drift is negligible for timecode purposes (better than 1 microsecond) and in a GNSS-denied environment the max. drift in the discussed example would be around 9 milliseconds per 24 h (or 1 frame in about 4.5 days at 24 FPS). Any GNSS resync realigns the internal clock to full accuracy. As UTC is an absolute time reference there's no need to worry about time zones, DST and other time corrections. UTC is identical at any moment everywhere in the world. For timecode the discussed precision is high enough. Other applications like absolute audio sampling sync or video genlock could probably also be achieved but I didn't check the specific timing accuracy requirements. If higher precisions would be required more precise external oven-controlled crystal oscillators could be used but they're much more expensive and require around 1 to 4 W of power depending on the ambient temperature.

Would an absolute timecode based on UTC time be a viable option? Using UTC (Universal Time Coordinated, the worldwide used date/time of day reference) as absolute timecode would allow to operate any device totally independently anywhere in the world while keeping a very precise uniform timecode. With a GNSS-disciplined precision oscillator it would be possible to keep absolute time sync better than +/- 3 milliseconds per day even if the GPS/GLONASS/... satellite signal is lost. With automatic GNSS resync a precision better than +/- 1 ms is easily possible. The drift without any GNSS signal to resync until 1 frame is reached would correspond to about 2 weeks. Effective precision depends on the used hardware, figures are based on relatively inexpensive commonly available components but higher precisions are possible (for example GSM networks are synchronized with sub-microsecond precision relying on GNSS time references). With an absolute UTC-based timecode each device could manage its timestamps entirely autonomously. I'd be interested to know if such system could be used as technically it wouldn't be very complex to implement.

I don't know the Switchcraft and Cannon XLR very well, as I'm in Switzerland Neutrik has always been quite popular (Neutrik is in Lichtenstein which is not Switzerland but they share the Swiss Franc, Swiss postal services and many other things, there are no customs nor border controls between those countries). Referring to the female 3-pin XLR cable connector Neutrik NC3FXX-B of the Rode Blimp "Mk II" (with possibly an adapted cable gland as the short cable is very thin) and the Rode NTG3 which features a proprietary integrated male connector design (gold-plated pins in some insulation base, pin 1 (Ground) is slightly longer to always connect first and disconnect last), the outer part with the latching notch is machined in the body of the rear part of the mic) I tried with and without that blue "toothed" elastic spacer washer included with the NTG3 and didn't found it useful, it merely applies stress on the connector latch and tends to slightly harm axial alignement between the cable connector and the built-in mic connector. Also IMO there's not really a mechanical noise issue. As there's basically mainly the mass of the female XLR connector of the blimp, the friction of the connector parts seems sufficient to prevent mechanical noise. Referrring to the male Switchcraft 3-pin XLR cable connector of the preinstalled (but easily replacable) cable assembly of the blimp, matching conditions with a Neutrik NC3FXX-B 3-pin female cable connector seem similar in terms of mechanical play. The issue is only that forces can be higher on the connector as this depends on how the cable is routed (for example at the top of the boom pole). If directly holding the pistol grip by hand maybe it's worth using an elastic spacer (it's impossible to wrap gaffer tape around the connector because the male connector body ends nearly flush at the bottom of the grip) but if a boom pole is used, routing carefully the cable should allow to prevent mechanical noise at the connectors. The comment about the spacer gasket is similar, I didn't notice a visible difference in mechanical play between the NTG3 - Neutrik XLR and between the Switchcraft XLR in the pistol grip and the Neutrik external cable XLR. BTW The discussed female XLR Neutrik cable connector features a profiled annular EPDM gasket (it's not formally an O-ring as the cross-section isn't). As the groove for the gasket has a rectangular profile I suppose that the gasket could be replaced by some common O-ring of the right size, maybe also a combination of two O-rings or a anO-ring in addition to the existing gasket could be used to reduce mechanical play. The corresponding male XLR connector has no sealing gasket. (There are also some protective caps for unused connectors but I never used them for XLR.) Though I'm by far not experienced enough I believe that most handling noise comes from handling errors and possibly from the construction of the boom pole (specifically the absence of some sort of pre-loaded diameter tolerance compensation parts at the rear end of each tube of the telescope, I got the impression that while tube sections are locked without play, the rear of each section has as very slight radial play). BTW I've no idea why Rode installed a Switchcraft cable XLR connector in the pistol grips and also one part of the pistol grip is designed in a way which makes the use of other connector types difficult because it is geometrically adapted to the profile of the cable gland. That said, I didn't notice mechanical noise issues with the Rode Blimp "Mk II" if everything is assembled and tigthened carefully. Not tightening enough the lyre supports and/or the end screws of the rail assembly can easily lead to some mechanical noise. If really required one could make a custom cable assembly with a regular mic cable ending with a very small highhly flexible shielded mic cable and remove the intermediate connector in the pistol grip. Doing so would be an advantage considering mechanical noise issues but OTOH there would be a fixed cable length requiring another intermediate XLR connector junction unless routing with a fixed length directly to the mixer/recorder.

Thanks for all replies. Interestingly manufacturers don't seem to mention much about how to position a shotgun mic inside a blimp and for the reasons mentioned by dfisk one shouldn't rely too much on published pictures. So basically the overall conclusion would be that the precision of the positioning of he mic inside the blimp is not that critical as it will only have a minor (if any audible?) influence. Overall it's probably more important to carefully route the cable and tighten correctly end caps, sliding lyres and the locking screws in order to prevent handling noise. I've noticed that Rode supplies some sort of "tooothed" spacing washer supposed to help reducing the mechanical play between the female XLR and the mic body but as I installed it it mainly pushed asymetrically the connector away (which ended with a slight angle) so I decided to remove that part as it seems to mainly stress the locking mechanism of the Neutrik cable connector. If required I'll rather try to wrap some gaffer tape but I couldn't hear noise specifically caused by the connector play.

IIRC in some video (from Rode or Rycote?) it was mentioned that if the lyre covers a few slots it wouldn't be problem (the lyres are narrow anyway). Maybe seasoned experts would be able to notice a very small influence on higher frequencies as a lyre still represents a small obstruction (even if not covering a slot), I don't know. Due to technical limitations, positioning the lyres only on the non-slotted end of the shotgun mic body leads to a weight load difference on the lyres which make longer tubes somewhat dropping toward the front. Also there would be an increased risk that the tube collides with the blimp body due to the long unsupported length. So basically I assume that it's more important to keep the axis horizontal (and also centered) than keeping the front lyre away from the interference tube, this also allows a better weight repartition between both lyres. Again thanks for your replies.

Thanks a lot for your answer. I agree that product photos don't necessarily reflect the way they'll be optimally used in real life though in user manuals they should pay more attention to such details. Do I understand correctly that the slotted tube part should be centered referring to "front/rear" of the blimp or rather the whole mic even if the non-slotted part of the cylinder varies depending on the model, also there's the XLR connector which takes some space? Due to possible space restrictions I'm not sure if it's even possible to center the slotted part, but centering the mic body (not considering the cable XLR connector) is usually possible. "Left/right" centering (seen from above) and "horizontality" can usually not be adjusted as those dimensions are typically given by the geometry of the installed lyres. I also wonder if Rycote lyres can end slightly permanently deformed if for example the mic is left inside the blimp for longer durations and especially if the blimp is laying on the side like in protective case (though I intend to remove the mic for storage). To me the Rycote lyre material looks like some specially formulated polymer (not elastomer, excepted for the inner co-moulded part which touches the mic) but I can't see if there will be permanent deformations or not. Interestingly there are no low temperature restrictions mentioned, I mean quite below freezing as typically some plastics can become brittle or at least stiffer. Again thanks for your help.

Hi everyone. This is my first post. Which is the best axial position for a shotgun mic in a blimp? Center the middle of the slotted part with the middle of the main body of the blimp (at least where dimensions allow it)? IIRC Rycote recommends to not place the front of the mic further than the main body of the blimp (i.e. before the end covers). Can the maybe about 1" wide annular [non perforated] part where the front end cover connects to the main body of the blimp cause audible degradation? Does it matter if tube slots are left and right OR at top and bottom (i.e. rotating by 90°)? Is it correct to assume that the front lyre doesn't have any negative influence if covering a very few slots (the rear lyre being usually clipped beyond the slotted part)? I did some searches but was unable to find a definitive answer. Also pictures from manufacturers don't illustrate any common practice. Any help would be welcome. Thanks everyone.