Mini Scoops - Reality check

Brilliant thread none the less!

Aman Gebru wrote: Oh dear, here we go again. Thinking that lower is the new god and using sound is the best way to define who you are. If you only go out there to use what others have provided to make yourself look good then f**k off really. You have missed the whole point and have become a massive slave to your own publicity machine. You will understand this one day. Hope it's not too late.

Oh dear, here we go again.

Thinking that lower is the new god and using sound is the best way to define who you are.

If you only go out there to use what others have provided to make yourself look good then f**k off really. You have missed the whole point and have become a massive slave to your own publicity machine.

You will understand this one day. Hope it's not too late.

BASSHORSE wrote: whats the defernition of a rear loaded horn??..more volume out the back of the speaker than the front? if so,,my minis are rear loaded horns rather than a reflex

Ooohhh, ha ha, have you just said that.

You just hurt my head lol. Where's that pic of Ray liotta.

Rear loaded horn is a scoop, or anything where you can see the front of the driver, which then has a chamber behind it, (not a chamber like in pyramids of Egypt), and then a horn from the chamber to the outside. A horn normally looks like a long thin thing that gets bigger near the end. No its not ya dick.

"Trouble is we have to split the argument, Roots/Reggae and other. One has pre-amp, one not and there IMHO is the rub."

I don't see any argument Nicky. Everyone wants max output with least size. It's even more important to the pro touring guys as they have to cart the stuff about every night, with smaller and smaller trucks as the accountant's say what the budget is and still put on a show that doesn't get them sued.

Reggae, well it's a way of life. A religion, a way of expressing yourself. For some it's a theme park ride to show whose best. It's still a ride though and I like rides.

You can get off at any time you know.

So Shortman is, "more" of a reflex than other minis, therefore it sounds best because as everyone knows reflex is best in sub heavy music. RC1 have proven this along with the FACT that horns in small places are doggy poo.
Me thinks too many punters are confusing 55/80 hz venue shaking with sub bass too.
Excellent writings Aman
Trouble is we have to split the argument, Roots/Reggae and other. One has pre-amp, one not and there IMHO is the rub.

Aman Gebru wrote: Lets clear this up once and for all. A mini scoop is a reflex design. It's not a transmission line or a rear loaded horn (scoop). This is a transmission line. It's the complete opposite of a mini scoop. In a classic transmission line the beginning of the tapered port should roughly be equal to the radiating area of the driver. The port then decreases down its length until it terminates with an area around 1/4 of its starting area. Not all transmission lines are of this design, it is possible to use a port of constant area thought its length. The port or resonant pipe as its know is tuned to 1/4 wavelength of the required operating frequency of the design. If you want to hit 40Hz then the port is going to have to be 2.15 meters long. For 35Hz the port will need to be 2.46 meters long and for 30Hz will need to be 2.87 meters long. A mini scoops port gets larger, not smaller and if it were a transmission line would not have the required length to load it anywhere near low enough. The longest port paths found in mini scoops are in the 1.4 to 1.5 meter range, and if they acted like a transmission line would be tuned to around 60Hz. Many have ports that are around 1.2 meters long, which would be a tuning frequency of 72Hz if you believe they are a transmission line. Users of mini scoops are reporting hearing notes from their speakers lower than 60Hz, so something else is going on. The truth is that if you reverse engineer a mini scoop you can calculate it as a reflex design. You have a driver in a rear chamber that is ported to the outside. The only difference is that the port is tapered and larger than normal. As the port has a large cross sectional area it will need to be longer for a given tuning frequency, hence why the ports are between 1.2 and 1.5 meters in length. Most mini scoops are tuned between 35 to 40Hz and because of the large port (that can be equal to the drivers Sd), will have more output at the tuning frequency compared with much smaller ports with an identical tuning. If you sim a mini scoop as a rear loaded horn then you start to see what's going on. And that is that the horn acts as a port and the important thing is the rear chamber volume. If you sim with a 1.4 meter horn with a rear chamber volume of 30 litres you get an f3 of 58Hz. If you now make the rear chamber 200 litres all that changers is the f3, which now goes down to 29Hz. This is not what happens in a true horn, as it's the horn length that dedicates the cutoff. The impedance plot is also very revealing when comparing a mini scoop with normal scoop. The mini scoop only has 2 peaks, which is the same as a reflex design, the normal scoop adds a third higher peak around 100Hz that is associated with a rear loaded horn. So a mini scoop is a reflex design with a larger tapered port. People on here say they play as heavy as normal scoops, yeah they will, in fact they could play more heavier as some are tuned around 35Hz or lower. If the track you are playing has a lot of content between 32 - 45Hz then the mini scoop could outperform or be equal to a normal scoop because it can be more efficient below 40Hz. The grunt people talk about from normal scoops is the rising output with frequency. The 60 to 80Hz output of a normal scoop can be very high and it's this that gives the impression of grunt and edge to the sound. A mini scoop plays flat as its a reflex and so while can be as loud as a normal scoop low down, doesn't have that 60 - 80Hz bite that gives the impression of raw SPL. It explains when people say, yeah the scoops at the dance were louder but the minis played heavy that night.

Everything you say does make sense, I've never seen or heard one of these cabs for real and I haven't put the effort into measuring port lengths from any plans around.

It would still be nice to see a near field measurement of port output, that will leave no questions as to how the cabinet is acting. Or an impedance plot would do it.

The only reason I say that is because I wonder if it is possible for the port to act with both characteristics of Helmholtz resonance and open pipe resonance simultaneously? Does it have to be strictly one or the other? If the reflex port was 1/4 60Hz in length would it not necessarily do both? Usually it is a non issues I suppose as ports are far shorter, and any pipe resonances are going to shifted up into a range that the driver assisted by the port is unlikely to be asked to play?

If I have a bit of time later I might see what Akabak thinks about it.