Scaling up the SS15 for an 18" driver and other compact 18" designs

[col]

Starting this thread after a need arose from the "SS15 build x8" thread (instead of hijacking it). The initial idea being explored is whether the SS15 could be scaled up to take a 18" driver.

Xoc1 has input some time into hornresp and come up with a concept that can be seen in this post:

SS15 build x8

$$Maan is very interested and is preparing to make some sawdust. I had been thinking about the concept but opted to build a Cubo 18 extended as a prototype. I'm not sure if it is going to play low enough into the 40hz range yet though so I am still very interested.

My work so far:

rebuilding the 18"s

regards,
col.

[salzburgsoundsystem]

Great idea!

but this does raise a question:

Which 18 will be the all-rounder / benchmark that the 3015lf once was, and which price category should we be considering?

Regards, Ben

[m R g S r]

A slightly scaled up ss15 would be the TH-18...very similar folding just sacled up.

Unless you mean just widening the enclosure to fit an 18" driver? Many 18's are much more powerful than a smaller 15, and would probably flex the thin 1/2" walls very easily. So then you get into re-designing the enclosure for 3/4" wood...I think that's what pyro did for the pyroboxes...

[m R g S r]

What's the compression ratio on the Cubo? It doesnt look to be like much at all? And path length looks pretty short for 40hz..

[Xoc1]

The Cubo is a hybrid tapped horn with an added bandpass chamber.
The chamber makes a big difference to the path length needed,
A similar chamber can be used with a front loaded horn, and is used by Turbosound and Funktion One in their horn loaded bins.

[col]

Originally Posted by salzburgsoundsystem

Great idea!

but this does raise a question:

Which 18 will be the all-rounder / benchmark that the 3015lf once was, and which price category should we be considering?

Regards, Ben

Good question, I've already got 4 x Peavey low rider 18"s so I'm kinda of stuck with them. It would be good to use a reasonably priced driver but depending on where you are and shipping costs that differs. At the moment in Australia the best value for money is the Chinese Ande drivers. I guess in the US Eminence would be the first choice and in the UK Precision Devices or B&C.

Maybe that is why the Cubo designs are so popular as they work with a wide range of drivers.

col.

[m R g S r]

Originally Posted by Xoc1

The Cubo is a hybrid tapped horn with an added bandpass chamber.
The chamber makes a big difference to the path length needed,
A similar chamber can be used with a front loaded horn, and is used by Turbosound and Funktion One in their horn loaded bins.

Okay gotchya. I was thinking it didn't look like a traditional tapped horn.

[col]

I guess the trick here would be working out a design where the bandpass chamber can be tuned easily to suit the chosen driver. Also, how does one determine the chamber size and tuning port?

[col]

I did some testing today. results were a bit disappointing. Basically, the Cubo18ext is not suited to the Peavey Lowrider. It can't go anywhere near low enough. Also, measuring the original 130ltr BR cab showed why the cabs need changing! Oh well, back to the drawing board.

First up I did a impedance test with WT3, magnet in the horn:



This gave a good indication of whats to come

Second up a holmimpulse frequency response:



I compared this with the original 130ltr BR cab (in red):




Then I did some 2.83v/1M SPL tests:


Cubo18ext 130litreBR
40hz 69.2 68.7
45hz 81.9 75.3
50hz 70.4 67.8
55hz 79.5 76.7
60hz 84.8 80.0
65hz 88.6 84.3
70hz 89.0 85.6
75hz 89.2 86.6
80hz 89.0 86.9
85hz 89.0 86.4

[col]

The measurements did indeed show at least a 3db increase in volume over the badly tuned 130ltr BR cab though. Also, with all that data and the actual drivers TS parameters it should be possible to work out how to model the cabs in Hornresp?

All the data is in the photo gallery:
rebuilding the 18"s

cheers,
col.