Ground Zero GZRF 6900P

A pressed steel chassis six by nine from Ground Zero. This is a brand that goes to very high extremes in SPL products for both ends of the audio spectrum both bass and unusually, high frequencies too. Their mad end tweeters are pure hearing damage if used carelessly (We do have all of them to test out soon they look like professional PA speaker drivers.) Ground Zero have a set of ovals called GZRF 69X in this range also, but those are only rated to 100w RMS, whereas these GZRF 6900P are rated to 250w RMS, which is very high indeed for this sort of product. Apart from JBL and especially DLS (although theirs is a 10×7 that fits into a 6×9 hole) I do not know of any other company who produces a six by nine oval speaker rated anything like this high in power handling. The signs are good. The magnet assembly is very large indeed, the spider, which is a pukka Conex job, has the tinsel wires woven in as braided flat ribbons and they can be seen on both sides of the bass cone, not just where they go from the terminals to the voice coil. This must be to balance the speaker spider on both sides. It looks unlikely to be the tweeter and midrange feed, as this is clearly seen entering the base of the magnet underneath via a shallow plastic stuck-on centre cover, having come around the outside of the motor from the terminal block under another skinnier cover.
There are two fat yellow capacitors seen on the chassis. One at the terminal block acts as a six decibel crossover for the highs and mids together, another is mounted adjacent to the tweeter inside and so is clearly intended to offer a different frequency point of crossover to protect the tweeter itself by another six decibels. There is no facility to bi wire or bi-amp this product, although an undoubtedly warranty-voiding modification would be simple.
They come with fixings, badged grilles and a length of cable with terminations on one end to connect to the speaker. There is a specification sheet for the entire Radioactive coaxial line also included. This has a slightly confusing template printed on the back for six different speaker sizes/shapes. Once carefully cut along the line for your speaker, though, it should not be too hard to use.
They look good and seem to tick all the boxes. Let’s go see how well these work
– Tri-axial speaker (three way)
– Pressed polished lacquered steel chassis
– Power Handling: 250w RMS, 400w max
– Efficiency: 92.7dB 1w/1m
– Coated paper cone
– Rubber top roll surround
– Conex Spider
– Woven-in Tinsel leads balanced on both sides
– 19mm Mylar dome tweeter, Ferrite magnet, pole mounted
– 50mm Mylar cone midrange, Ferrite magnet, pole mounted
– Two 6dB per octave crossovers by way of single capacitors
– Ten-inch sub-sized motor assembly with polished back plate to magnet and decal wrapped around edge
– Mounting Depth: 85mm
– Complete with grilles, fixings, specification sheet with printed multi-template and two hanks of terminated wire
Review by Adam Rayner
When I first saw a Ground Zero product at the CES in ‘Vegas it was so mad that it became the inspiration for the look of a cartoon character that was once part of my life called BoomZilla. (And will be again, as we are going to resurrect him as Son of BoomZilla.) Ground Zero make stuff under the slogan ‘Hard Core Attitude’ and these 6x9s are from their ‘Basic’ Radioactive series. They do make a lot of different levels of kit, but in the coaxial type, these are their baddest. There is also a lesser-rated set for the less hooliganistic amongst you that is ‘merely’ rated as high as most other makers go at 100w RMS.
In my youth I was an inveterate blower-upper of six by nines. In fact it was discussions over my blown mids or tweeters at the JBL headquarters with their then expert repairer that was to form a part of my education for dealing with speaker warranty repairs myself in later life. There is always a nutter who has the power but not the restraint or more often the lack of it, (driven hard into square waves) to kill a speaker. The 6×9 is where so very many people start their addiction. This sort of speaker helps shape drivers’ urges for ever yet more power and clarity in their mobile music. So this is a very important category. Not beloved by the elite, 6x9s are a definite mainstream thing, yet GZRF 6900P are slightly odd in that they are aimed at the top end of that mainstream user.
They don’t come with a lot of extras or accessories, but that helps keep the price down to the £110 level. Still, it’d be nice to get a window decal and perhaps a flyer showing all sorts of swag like shirts or what have you. This brand has a cool name and I reckon they should promote more. Anyway, I plugged these into the house test enclosures, made complete with nice standy-up bits when Fusion ran their Area51 installation salon, and I powered them up using the Genesis Stereo 100 amplifier from the test bench test rig.
I should have used a bigger amplifier, as these ovals ate the watts, real ‘Genesis Watts’ as the fans say, for breakfast. I pulled out the AudioControl SA-3055 real time analyser that the utter sweeties at AudioControl sent us from the Pacific Northwest (home to pukka coffee and lots of clever people) and applied it to the output of the speakers. Nothing too scientific, just an idea of how sodding loud these go. Just to confirm the ruddy obvious in numbers.
They is loud, Bruv! I was getting of the order of 127dB close up to them when they were rocking on music by Yello and was achieving around 110dB in the air at around seven or eight feet away a possible distance from them in a car although by that far away, you might worry that there is some ‘room stuff’ (acoustics) going on. Having said that, I take over the landing for these tests and the space the speaker boxes stand in have two doorways to other rooms immediately either side of them and the stairwell faces them opposite. So any standing waves in the room space will be from big ****-off bass wavelengths mostly below where these play.
I flicked to RTA from SPL measurement and checked out the relative levels. There wasn’t much below 40Hz, a bit of 30Hz and just every now and again the last 25Hz ‘anniversary-edition blue’ LED would flicker, which was absurd, as this cone is only a wee thing. The tweeters and midranges are far from posh and refined. After all, you have spent all the money on the stonking bass these things can make as they really can take the power. They are also horribly efficient and so they could slice your head apart if used injudiciously, since the highs and mids can become really intense.
I wasn’t expecting silver Mylar drivers, meant for high power use to be terribly refined but that was to miss the point. What they do achieve is a bone-blasting belt of sheer LEVEL. If you have urges to get it put in writing by the environmental health officer in Eastbourne, or want to drive with the windows open and share your tunes with a whole selection of the world and don’t care whether they want to share or not, these may well be perfect for you.
Back in the days when I was just concluding that I had to go to the effort of adding a real, actual subwoofer to my own system, I would have bloody adored these. I confess a soft spot for them. Indeed, they score highly enough, with their insane power handling, coupled with killer efficiency, to rate them a Recommended flag. They are no-rehearsals Rock N’roll, big-bollocked rocking phuckers and if you don’t like it, you’re probably too old.
Overall 9.0
Sound Quality 7
Build Quality 9
Power Handling 10
Efficiency 10
Value For Money 9