Scaling up the SS15 for an 18" driver and other compact 18" designs - Page 3 - diyAudio
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Old 19th January 2012, 12:48 PM   #21
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Default Just wondering

Sorry to go off topic!

I'm just wondering why nobody has simply stuck an 18" in the stadium horn. The baffle is already (just) big enough at 24x 18.5 inches.

What advantages does the scaled up SS 15 over this?

Regards, Ben
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Old 19th January 2012, 01:17 PM   #22
jbell is offline jbell  United States
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Quote:
Originally Posted by salzburgsoundsystem View Post
Sorry to go off topic!

I'm just wondering why nobody has simply stuck an 18" in the stadium horn.
mainly because I haven't found a compelling 18, that gives me more sensitivity at 1 watt and at 500... and a better response curve in either design.

I have several good 15" options, so I stay in 15 land....
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Old 19th January 2012, 01:33 PM   #23
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Default Sorry about that temporary thread hijack!

Thanks JBELL! Will soon have real life results on the dubhorn.

In the meantime, good luck with the SS18 guys!

Regards, Ben
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Old 19th January 2012, 08:42 PM   #24
col is offline col  Australia
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Quote:
Originally Posted by Xoc1 View Post
Hi Col as you note the Peavey 18 Low Rider is good in a BR box, and not so good in a Horn.
The initial scaled up SS15 design was not brilliant with the Peavey - The TH18 sim was even worse! The Cubo sub sim showed some promise, the throat chamber seems to help produce a flatter response.
I have updated the drawing with a bandpass chamber, and run a few sims.
This one seems forgiving of increasing the Le value which is likely to be bigger than the quoted spec.
Internal volume is 340 Litres.
BTW with a driver more suited to to a horn, the response with this design is not flat at all.
There is no optimisation for sheet sizes. External size is 95 cm high 57 wide and 72 deep. Hopefully SUV sized.
If its not worth it, then building a BR box tuned to the response you would like is your best option.
If you want to explore this option I could produce a dimensioned drawing, and maybe a Akabak sim. Grey line in SPL chart is first attempt with the Peavey driver.
Regards Martin (Xoc1)
Hi Xoc1,

Thanks for that, looks interesting, hold fire though. Iv'e just completed my new Xover/DSP:

2 X MiniDSP Balanced 4 inputs and 8 outputs boxed in a 1RU using a laptop SMPS and 12 XLR connectors. Front panel USB access.

Click the image to open in full size.

I'm going to take it, the Cubo18ext and the 130ltr BR box and a few amps out onto a property this weekend and do some more testing utilising the filters and PEQ. Should give me a better indication of whats possible. I'm wondering how much I can boost the 45-50hz using a PEQ when I have a 48db 40hz high pass.

I'm also considering selling the Peaveys in the 130ltr BR enclosures and starting again using the Ande SB18-2:

JDs Sound and Lighting. Ande SB18-2 18" 800W 8 ohm driver / speaker NEW

cheers,
col.
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Last edited by col; 19th January 2012 at 08:49 PM.
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Old 19th January 2012, 08:46 PM   #25
col is offline col  Australia
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Originally Posted by jbell View Post
mainly because I haven't found a compelling 18, that gives me more sensitivity at 1 watt and at 500... and a better response curve in either design.

I have several good 15" options, so I stay in 15 land....
Hi Jbell,

Whilst looking for 18" drivers I spotted this:

JDs Sound and Lighting. Ande Neodymium 15" AN-15C 500W 8 ohm driver / speaker

Would that work in the SS15?

cheers,
col.
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Old 19th January 2012, 09:33 PM   #26
col is offline col  Australia
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Quote:
Originally Posted by salzburgsoundsystem View Post
Sorry to go off topic!

I'm just wondering why nobody has simply stuck an 18" in the stadium horn. The baffle is already (just) big enough at 24x 18.5 inches.

What advantages does the scaled up SS 15 over this?

Regards, Ben
Thats not off topic "and other compact 18" designs" should encompass your post
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Old 19th January 2012, 10:05 PM   #27
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Quote:
Originally Posted by col View Post
Hi Xoc1,

2 X MiniDSP Balanced 4 inputs and 8 outputs boxed in a 1RU using a laptop SMPS and 12 XLR connectors. Front panel USB access.


I'm going to take it, the Cubo18ext and the 130ltr BR box and a few amps out onto a property this weekend and do some more testing utilising the filters and PEQ. Should give me a better indication of whats possible. I'm wondering how much I can boost the 45-50hz using a PEQ when I have a 48db 40hz high pass.

cheers,
col.
Though the driver excursion is at minima around Fb, there is still lots of pressure on the cone there.
The impedance is also lowest around Fb, so most amps can deliver maximum power .

Boosting too much at Fb can cause cone kinking and voice coil burn with enough power. remember a 10 dB boost requires 10 times the power.

BTW, the Low Rider 18 should work OK in the SS15 with a couple dB more level at 60 Hz, and a couple dB less at 100 Hz, but no improvement down low.
Single sheet TH challenge

Nice job on the Minidsp box.
If you notice any 50 Hz (Oz is 50 not 60 Hz AC, right ?) and harmonic noise (100, 150, 200 etc.) you should experiment with rotating the PSU, sometimes a few degree difference can lower the noise floor by several dB.
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Old 23rd January 2012, 03:40 AM   #28
col is offline col  Australia
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It rained so I didn't get to do as much testing as I would have liked. The MiniDSP performed well and is very quite, I think using nylon PCB standoffs instead of metal screws/spacers helps avoid ground loops.

I did manage to test a different one of the 4 Peaveys in 130ltr BR enclosure though. It's a lot closer to the factory spec and looks much better than the previous one I tested. I only have a holmimpulse graph:

Click the image to open in full size.

red = 130BR
blue = Cubo18ext (ignore the amplitude volume was lower)

I took the driver out and tried in in the Cubo18ext but the graphs were fairly similar to the previous measurements. I Tried a 6db and a 10db boost with a PEQ around 50hz but it didn't make much difference. I'm giving up on the Low Rider in the Cubo18ext.

I might try re-tuning the ports in the box that doesn't work very well. I'm supposing that when I built it I did it to the manufacturer spec but the driver is so far off it's not working properly, so by measuring the driver with the WT3 I should be able to adjust the ports to match.

cheers,
col.
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Last edited by col; 23rd January 2012 at 03:43 AM.
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Old 23rd January 2012, 07:40 PM   #29
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Quote:
Originally Posted by col View Post
It rained so I didn't get to do as much testing as I would have liked.

I Tried a 6db and a 10db boost with a PEQ around 50hz but it didn't make much difference. I'm giving up on the Low Rider in the Cubo18ext.

I might try re-tuning the ports in the box that doesn't work very well. I'm supposing that when I built it I did it to the manufacturer spec but the driver is so far off it's not working properly, so by measuring the driver with the WT3 I should be able to adjust the ports to match.

cheers,
col.
A friend of mine used to hypothesize that speaker magnets attracted clouds, it rained on about 50% of our outdoor shows .

For the most part, other than with sealed cabinets, boosting below F3 or Fb is pretty useless.

Fb in a ported cabinet is Fb regardless of the driver loaded, the “bad” driver in the 130 liter box looked like a 45 Hz Fb. You could certainly tune it lower, but don’t expect SPL improvements.

Looks like the ported cabinet has way deeper extension, usable to around 40 Hz.
How much level difference was there between the two cabinets?
What filters were used?

Art
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Old 23rd January 2012, 08:03 PM   #30
col is offline col  Australia
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Quote:
Originally Posted by weltersys View Post
A friend of mine used to hypothesize that speaker magnets attracted clouds, it rained on about 50% of our outdoor shows .

For the most part, other than with sealed cabinets, boosting below F3 or Fb is pretty useless.

Fb in a ported cabinet is Fb regardless of the driver loaded, the “bad” driver in the 130 liter box looked like a 45 Hz Fb. You could certainly tune it lower, but don’t expect SPL improvements.

Looks like the ported cabinet has way deeper extension, usable to around 40 Hz.
How much level difference was there between the two cabinets?
What filters were used?

Art
Taking into consideration the driver and port displacement the vented box comes in closer to 121 litres. It's tuned to 38.66hz (according to WinISD).

The BR box is around 3-6db lower in amplitude than the Cubo18ext but with far better response and much lower extension. Also, it will take heaps of power.

The filters were set at 35hz HP 48db LR and 90hz LP 48db LR.

What if I took the 2 worst performing boxes and rebuilt them using 200 litre BR and tuned them lower, would they still play along nicely with the smaller cabs?

cheers,
col.
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