# of heads on front versus rear

[Tambourine-Man]

Various manufacturers recommend variously 2 heads on front and 2 on the rear or 3 on front and 1 on the rear. The maximum that one box will take seems to be 4, correct? So, unless one gets two cpu boxes they have to go with one or the another - although I suppose 4 on front and leaving the rear unprotected is also an option.

I have read that sometimes even just one head on front is sufficient, so seemingly one on the rear might be sufficient. The rear does not have headlights, but on the other hand usually the rear presents more vertical surface. The rear tail lights are designed to reflect light more than what's typically on the front.

I suppose the type of vehicle may influence whether you would follow the manufacturers recommendation. Large SUV's with a lot of frontal area and chrome may need the 3 (or 4) on the front. Also, the prevalence of rear shots in the areas one frequents would be a factor.

But aren't rear shots typically from closer than frontals? So wouldn't that argue for more on the rear?

Why do some recommend 2 rather than 1 on the rear? Or alternately why do some recommend 1 versus 2?

I have small, black car (BMW 335). Do y'all think 1 head on the rear will be sufficient? I believe L.I. recommends 2 on the rear (but money for toys is always a factor. My V1 has never even registered a real laser hit - I get them going through toll booths and once I think it picked up an Infiniti, so it's not like I live in Laser Land (yet).)

[repeter]

If you can get access to a gun, then test out one head on the back of your bmw. That's the only way you'll know for sure..

[Tambourine-Man]

Obviously access to a gun is a good final check - and I am lucky to be near to Suf Daddy who rents them. But it would be nice to know in advance of installing and also forking money over for the gun rental, where and how many to install.

My expectation is that 2 are sufficient (perhaps even more than sufficient) for the front for my car, but the question is whether 1 is enough for the rear as L.I. recommends 2.

[ahmadr]

Various manufacturers recommend variously 2 heads on front and 2 on the rear or 3 on front and 1 on the rear.

No manufacturer recommends 3 front and 1 rear.

[MemphisRheins]

Obviously access to a gun is a good final check - and I am lucky to be near to Suf Daddy who rents them. But it would be nice to know in advance of installing and also forking money over for the gun rental, where and how many to install.

My expectation is that 2 are sufficient (perhaps even more than sufficient) for the front for my car, but the question is whether 1 is enough for the rear as L.I. recommends 2.

Im not taking any chances with my TSX (roughly the same sized car as a E46 3 series, bigger then a E36, not sure what gen you have) Im going two heads front and rear... Rear shots are favored around here lately, I've seen quite a few cops sitting on entrance ramps with Kustom ProLites and other guns (bit harder to identify at quick glance) shooting people in the back.

[repeter]

No manufacturer recommends 3 front and 1 rear.

PASS recommends 3 in the front..

[rsatmans]

It is much harder to jam a cop from the rear. Usually due to the extreme angle and shorter distance to the gun but also the rear has a much larger laser signature so to speak. If you want protection in the rear 2 heads is the minimum. Let me expand many of the tests on the rear that you see are pure crap. They usually try to jfg. This is simply lets drive away from the laser gun and see at what point if any we get pt. Back in the real world it is much different usually if a cop shoots you from the rear he is on a overpass or a entrance ramp onto highway. The angle much greater and therefore harder to jam. The only time i have seen good rear tests was with CFL where the were shooting Cliff from a overpass on the rear I believe.

[Tambourine-Man]

I saw a series of tests with just one head in the front and some of the jammers did OK, but maybe that's because as Rsatman says the laser signature is lower in the front.

But he also raises a good point. I always thought laser traps had to be almost straight head on (or rear on). Obviously if the laser gun is pointed perpendicular to the line of your travel your effective speed as measured by the gun is zero even if you are doing 200.

Most of the testing I have seen is also head on or rear on. Any links to tests done at an off axis angle (not an overhead down angle)?

[TSi+WRX]

So far, all evidence points to the rear of the vehicle being much harder to protect, via active jamming.

The current thoughts as to why this occurs, at the level of the physical vehicle itself, relates both to the typically much more upright vehicle profile at this aspect, as well as the increased number of reflective lighting elements (which cannot, for obvious reasons, be addressed as sufficiently with various passive means; search for the member fulcrum here, and look at how he attacked this problem on his Alfa, a vehicle for which its unique physical shape, as well as his dedicated testing of both its active and passive defenses, illustrates how hard it is to protect this aspect of a vehicle - you can also look for past posts on both this Forum as well as on the Laser Pro Park Suppor Forums, where charles charlie charles illustrated the same considerations, with his multiple-head LPP setup on his late-model Mercedes SUV).

Also, there further exists the presence of the much-hated license plate. And again as with lighting element concerns, this is an area of the vehicle where properly addressing this concern is much more of a headache, as compared with the front of the vehicle.

Combine this with the typical nature of rear-enforcement shots - awkward angles (not necessarily "perpendicular" to travel direction, rather, think three-dimensionally, and more dynamically - what happens from an elevated position, such as a downwardly sloping on-ramp, especially when there's a curvature involved? || also, yes, cosine effect always works to our favor, but what if the velocity of the vehicle is high enough that it overcomes said effect, given the physical setup of the trap?), shorter distances - and it again becomes easy to see why rear-enforcement is so dreaded, and why some setups, such as a single-head on a larger (or even just "wider") vehicle, may fail to even DETECT the threat (which is the "first foul" of active jamming).

The Laser Interceptor's rear heads really is rather amazing, in this respect.

Aside from recommending that two heads be devoted to defending this aspect of the vehicle, Ivan's design of the "Slim" heads is to play a bit of optical trickery and thus obtain better extreme-angle reception, at a sacrifice of both "sun/glare" interference, as well as absolute distance/range. And it just so happens that in physically "shortening" the heads, it gives the LI "Slim" units a unique capability to better fit into the typically more shallow recesses and spaces that present at the back of the vehicle.

^ I know that may sound like an advertisement for the LI's rear "Slim" heads, but believe me, I'm a total-independent when it comes to this game. No affiliations, no ties.

I just really admire the specific-for-purpose design of these heads, for this particular threat.

[ahmadr]

PASS recommends 3 in the front..

But not 1 in rear!