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C18-600LF

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rastaman View Drop Down
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    Posted: 11 June 2005 at 7:17pm
This is where I demonstrate my newness to this all.

I'm in the US, and looking at the price of the Challenger 18" which is about $180 as oppose to the SD18 which is like $350, I wondered what would be the difference in response between the two.

The Challenger has a slightly higher resonant frequency 39Hz to 33.2Hz and a lower Vas 220l to 264l and a much higher Qts of .35 to the SD's .26 and a lower BL (24.5 to 35.8)

Being a total novice, I plugged all this stuff into WinISD and stood well back. The X1 looks to me to be some kind of 6th order bandpass, with a chamber in front of the driver, and another behind it, but I'm probably way over-simplifying, and the two drivers produced very similar results, with the Challenger producing a slightly steeper incline on the frequency response, and so it looked as if it might be slightly lower at the 3db point.

So I'm obviously missing something really big here, else everyone would be throwing the cheaper driver in, and it doesn't make much sense to me, higher fs and Qts giving better results. I got even better results in a closed and vented box, so I'm really messing something up here, what is it? I know there is magic in the Qts around the .28 mark, but isn't that to do with horns, and not vented/ported enclosures, what is the X1?

NB numbers I put into WinISD Front Chamber volume 83l (calculated), Rear Chamber 250l(total volume - Front). Front tuning frequency 69.3 (Fathomed out by selecting a square vent .12m x .57m then varying the tuning frequency 'til I got a port length of .252) Rear tuning frequency 34.7 (same method, for a port length of .417). At some point I suppose I should redo it to take into account the volume used up by the bracing and shelving.

I can put the ISD project files online for anyone who is interested.

And yes I have my Thiele Small book on order in the local library


Edited by rastaman
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tb_mike View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2005 at 12:29am

The X1 is indeed a BP6 with funny shaped ports.

Get winisd PRO.

You got better results in sealed and ported? I doubt that.The X1 is a resonant,efficient,narrow bandpass enclosure,something near 98db/1watt.

Bear in mind that t/s parameters look at 1watt levels not 1kw(large signal) Tiny xmax means limitation on power input.

Cheaper drivers probably have lower maximum SPL or some other deficiency.

 

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Dom View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dom Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2005 at 4:51am

Probably the best person to answer this would be Rog...

Originally posted by rog mogale rog mogale wrote:

In my tests the V 18 did go lower than both SD 18 and C18 650 EL.

But if you don't need really high output levels the C18 650 EL will give you higher output for its input. The sound is quite smooth and extension is good. But I wouldn't want to stick 1200 watts into the C 18650 EL for to long, especially in a bandpass cab as they don't offer the driver much stability.

So for making use of lower input levels I would go with the C18 650 EL. For more output use SD18, and for ear death useVoid V 18 and stand well back.

Rog.

"It sounded like a million fire engines chasing ten million ambulances through a war zone and it was played at a volume that made the empty chair beside me bleed."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dom Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2005 at 4:55am
Oh and I think your box volumes are way off.  You shouldn't be including the volume of the ports in with the chambers.
"It sounded like a million fire engines chasing ten million ambulances through a war zone and it was played at a volume that made the empty chair beside me bleed."
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rastaman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastaman Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2005 at 10:30am
Originally posted by tb_mike tb_mike wrote:

You got better results in sealed and ported? I doubt that.The X1 is a resonant,efficient,narrow bandpass enclosure,something near 98db/1watt.
Oh no, sorry. I got better results with the Challenger vs. SD18 when modelling them in closed and ported boxes, not that they produced a better frequency response in closed and vented boxes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rastaman Quote  Post ReplyReply Direct Link To This Post Posted: 12 June 2005 at 10:39am
Originally posted by Dom Dom wrote:

Oh and I think your box volumes are way off.  You shouldn't be including the volume of the ports in with the chambers.
Ah, that probably isn't good then, you're right I did include port volume in each calculation. 
The C18-600LF is marked as a low frequency woofer compared to the C18-650EL, it's resonant frequency is lower and it's Qts is a hair lower and it has a much higher Vas, sensitivity is only a dB less than the 650, but only a dB more than the SD.

Would the much lower Vas of the 650 give me more output for a smaller input, given that they all (SD18, C18-650EL and C18-600LF) have the same Sd and xmax? Or am I better to stick with the 600 and it's lower resonant frequency? Given through all this that both Challengers can't take the same maximum power as the SD but all have very similar efficiency figures, Sd and xmax.


Edited by rastaman
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tb_mike View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 15 June 2005 at 1:41am

Originally posted by rastaman rastaman wrote:

Originally posted by Dom Dom wrote:

Oh and I think your box volumes are way off.  You shouldn't be including the volume of the ports in with the chambers.
Ah, that probably isn't good then, you're right I did include port volume in each calculation. 
The C18-600LF is marked as a low frequency woofer compared to the C18-650EL, it's resonant frequency is lower and it's Qts is a hair lower and it has a much higher Vas, sensitivity is only a dB less than the 650, but only a dB more than the SD.

Would the much lower Vas of the 650 give me more output for a smaller input, given that they all (SD18, C18-650EL and C18-600LF) have the same Sd and xmax? Or am I better to stick with the 600 and it's lower resonant frequency? Given through all this that both Challengers can't take the same maximum power as the SD but all have very similar efficiency figures, Sd and xmax.

If their very similar modeling I wouldnt worry. how they sound,large signal behaviour is another thing altogether.

 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote mobiele eenheid Quote  Post ReplyReply Direct Link To This Post Posted: 17 June 2005 at 5:09pm

Quote Oh no, sorry. I got better results with the Challenger vs. SD18 when modelling them in closed and ported boxes, not that they produced a better frequency response in closed and vented boxes

The SD-18 is made for efficiency, those kind of speakers don't model well up in either closed or basreflex, speakers with higher Qts will give nicer results here (for sub).

Also the SD-18 has an Xmax of 5 mm. The usable excursion is actually much higher (more like 9 mm) due to it's much thicker gapheight, this was also taken into account by Rog at the time. Combine this with it's much higher efficiency and you'll get much more output.

Comparing 2 speakers on 1 Watt/meter is useless since it will give misleeding results in most cases.

Wkr



Edited by mobiele eenheid
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