Eminence 18 Scoop

It would seem this scoop has pots of Negative expansion, but it is an absolute killer with the PD1850.

Why does it work? (Quotes from SP)

Saul wrote: yep the second turn just doesnt look good.

mobiele eenheid wrote:
At first glance it seems to have quite some aspects in common with the superscooper (like ~horn length, overall dimensions/layout and horn mouth).
speakerplans.com/index.php?id=18superscooper

It's about 9% more in volume and the rear chamber is 34,5% bigger. The first isn't bad, the latter might work in you disadvantage. Due to the alike-ness, it seems suitable that you're using similar bracing. The extended bracing from the superscooper also shows, what I would call, corner bracing: In the upper right corner, a piece with 45 degree angles, with dimensions that it more or less follows the horn flare throughout the horn (path) design.

Wkr Johan

paulus wrote: yeah theses are great, first scoops i ever had,but they do not fit though a house door(interenal)had to take it of hinges ex misses was not pleasedLOL hence the cuttin down in width

Meat wrote: Ask Davey T. I think he built ours exactly as drawn in the plans. They were great. Made a helluva noise.

levyte357 wrote:

Autograff wrote: Quick question , would the Turbomax 1200 , 1500 and 1800's all generally work in the same box?

Roy says Turbomax 1200/1500 are basically same driver, with 1500 having stronger JBL'ish chassis, and improved cooling due to increased venting on Magnet.

I have heard 1000/1200/1500 in same mini scoop, and they were lovely.

However, Marvin is the Turbomax expert over all the range.

Comments pls..

PM'd from The Mighty Staiper

Staiper wrote: Hi,

Yes .. negative "expansion" not always have to be bad thing.
In fact a bit of area reduction through horn path practically forms a kind of natural low-pass filtering
which in turn may "preserve" some power for lower frequencies.

This "negative expansion" is a bit contrary classic horn theory and it is very shaggy to simulate and get predicted results on real thing. ..That may be major reason why most speaker designers trying to avoid "negative expansion".

A little bit (25mm) of area reduction on top of angled panel will not make nothing "bad" ..but really do not know will it make any noticeable low pass filtering at all compared to normal-expanding horn.

With more drastic negative expansion (like on original Eminence plans) effect will be more pronounced but than there is also much more chance to mess things up.
For example to tight area reduction may form nice low pass filter (which may make low bass sound to appear even deeper) but also will kill good part of real SPL.

Best wishes,
Stipe

why not make the last corner less sudden? is this sudden turn a good thing? the bit which is basically making the mouth on the top side of the horn. Is there are purpose to it and what would be bad/good about taking off the hollow triangle making the final part of the horn 2 angles instead of 1.

hope that's clear..

bassmish wrote: why not make the last corner less sudden? is this sudden turn a good thing? the bit which is basically making the mouth on the top side of the horn. Is there are purpose to it and what would be bad/good about taking off the hollow triangle making the final part of the horn 2 angles instead of 1.

In all honesty, this design disobeys most laws of folded horns... and smokes most "pre HOG" scoops... smiley29

I was almost definite on getting prototype built with modified expansion, but after the PM from Staiper, and remembering how's these things sound, I'm personally altering as little as possible, on my 1st prototype.

Mods, Please move this thread to the Scoop Forum.

levyte357 wrote: Mods, Please move this thread to the Scoop Forum.

Done !

One of the things I find interesting is the fact that all the folds in a horn of a scoop are to small, technically, to make much difference to the sound if you move them one way or the other. The scoop must be the most varied bass cab ever to be built. With my take on resonance, I think that different sounds can come from the way the cab is held together. Also materials used make a difference. It's also hard to get a like for like comparison. I can understand the chamber angle, because that space has a great influence on the speaker, but moving parts of the horn around an inch or two, I'm not convinced.
If people really want an improvement an the existing scoops, it's easy. Just make them 4' deep and develop an extension of the horn to suit.
I do think that the cab has gone as far as it can go with the existing excepted size. Of course, I could be wrong.

Tony.A.S.S. wrote: With my take on resonance, I think that different sounds can come from the way the cab is held together. Also materials used make a difference. It's also hard to get a like for like comparison. I can understand the chamber angle, because that space has a great influence on the speaker, but moving parts of the horn around an inch or two, I'm not convinced.
If people really want an improvement an the existing scoops, it's easy. Just make them 4' deep and develop an extension of the horn to suit.

Ah, the master speaks.

Thanks for that Mr T.

I completely agree with you there. I just want a 636mm wide Turbomax compatible cab, so hopefully just increase in chamber size by extending front of cab, and compensated throat , will do the job.

I know most builders always build the cab with at least top right corner brace, so I'll be adding those. But that's it.

GIVEorTAKE wrote:

levyte357 wrote: Mods, Please move this thread to the Scoop Forum.

Done !

Marvellous service. smiley32

Tony.A.S.S. wrote: I do think that the cab has gone as far as it can go with the existing excepted size. Of course, I could be wrong.

Granted, but so has the Mk1 and Mk2 Ford Escort. Despite that every Sunday, especially in Ireland there are hundreds rallying them, pushing for that little bit more... The reason they shirk the new technology? They are loyal to the design and it's fun.
So, about this 4ft deep scoop, nothing wrong with that for an install, under the stage maybe? smiley20