TH-18 Flat to 35hz! (Xoc1's design) - Page 13 - diyAudio
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Old 16th June 2011, 02:02 PM   #121
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I have some experience with the 5100. I have one sitting on my desk at home currently. It will handle more power thermally and with just as good of cooling as these other drivers despite the ratings. I would have no qualms putting a 2-4kw rated amp on it if you use some care to set it up right. It has probably twice the vc mass of most of these other drivers mentioned and 1.5-2x the linear displacement. Power handling specs are some of the most worthless in my experience. It has so much dependancy on the cabinet loading on the driver, the content run through it and the duration of it. It is a very good driver but very very expensive now. Unless you are going to go for real 25-30hz extension and maximum output per cubic foot of cab it is a little bit under utilized. You can get 90% of the performance for less than half of the price. YMMV, FWIW and all of that.
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Old 16th June 2011, 06:00 PM   #122
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Quote:
Originally Posted by Djim View Post
Both should be working in the Xoc1 fine although there could be a small difference in Group Delay. I haven't seen any PDF about the 4 ohm version but I'm working on it. Maybe Art has the Thiele-Small for the 4Ohm version since he uses them.
There are quite a few minor differences in the specifications.

The heat dissipation the BC-18SW115-4 is quite impressive, in side by side high power testing of some Eminence drivers the ceramic magnets would be hot to the touch, while the BC seemed to not have raised in temperature hardly at all.

There are very few amps (unless bridged mono) that have enough power to utilize the peak potential of the 8 ohm version.

The 4 ohm version is not really half the impedance of the 8 ohm, I am using Crest CA-9 bridged mono into a single speaker, but it is just tickling the speaker at clip levels (perhaps 3000 watt peaks). I think amps capable of 7000+ watt peaks would not be at all out of line for this speaker.

Here are both the 8 ohm and 4 ohm versions:
Attached Images
File Type: png BC-18SW115-8.png (69.0 KB, 1082 views)
File Type: png 18SW115-4.png (92.4 KB, 1062 views)

Last edited by weltersys; 16th June 2011 at 06:15 PM.
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Old 16th June 2011, 07:12 PM   #123
Djim is offline Djim  Netherlands
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Thanks Art for the info. There seems to be no difference in the gap between the 4 and 8 ohm version which means some distributors need to correct their Thiele-Small parameters.

I made both HornResp to compare the difference between the 8 and 4 Ohm version. Based on 1 watt calculated for each driver.
Eg for the 4Ohm version = 1,8V
Eg for the 8Ohm version = 2,3V

As you can see there is no difference between sensitivity and a very minor difference in response. As suspected the minor differences you only will see back in Group Delay and impedance.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Last edited by Djim; 16th June 2011 at 07:17 PM.
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Old 16th June 2011, 09:10 PM   #124
hisense is offline hisense  United Kingdom
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Quick question for Djim / Xoc1 or the many experienced horn men on this thread...

I noticed many of the other drivers proposed for the design show a smoother and more extended response than the BMS18n850V2- albeit the model response are for 4 cabs. As size is not an issue for me should i look at tweaking the design to better suit this driver? Or as a horn novice am i wasting my time and opening a can of worms trying to improve on this? - i definately want to try a tapped horn and have the BMS units sitting on the shelf.

I have been trying to learn about horns and playing with hornresp and will get stuck in if there is a chance adaption of the design will help get the driver / cab combo to start rollling of at 40hz rather than 45hz as it does currently. I am guessing i need more effective lenght?

Sorry for the basic questions and not contributing anything useful to this thread!

Once its built i will post measuremens - have an earthworks mic and smaart live.
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Old 16th June 2011, 10:09 PM   #125
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Quote:
Originally Posted by hisense View Post
Quick question for Djim / Xoc1 or the many experienced horn men on this thread...

I noticed many of the other drivers proposed for the design show a smoother and more extended response than the BMS18n850V2- albeit the model response are for 4 cabs. As size is not an issue for me should i look at tweaking the design to better suit this driver? Or as a horn novice am i wasting my time and opening a can of worms trying to improve on this? - i definately want to try a tapped horn and have the BMS units sitting on the shelf.

I have been trying to learn about horns and playing with hornresp and will get stuck in if there is a chance adaption of the design will help get the driver / cab combo to start rollling of at 40hz rather than 45hz as it does currently. I am guessing i need more effective lenght?

Sorry for the basic questions and not contributing anything useful to this thread!

Once its built i will post measuremens - have an earthworks mic and smaart live.
Longer path length and a bigger cabinet will go lower.
I could not find any specs for the BMS18n850V2, so hard to speculate how big, or long, or how low.

Hornresp shows multiple TH cabinets having a lower LF corner, while in reality that simply does not happen.
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Old 16th June 2011, 10:43 PM   #126
Djim is offline Djim  Netherlands
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Hi sense, like Art already pointed out, stacking TH’s wont lower the Fb of the system. In this case it is set out at 37,6Hz and the knee (where the signal starts to drop off) will always stay above this point.

But I have checked 4cabs response to be sure. Although maybe the sound of the BMS will have a German accent for the rest it will perform just like any other high quality driver in the Xoc1. The bumps in the response from the prediction will be less in reality so you don’t have to worry about that either.
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Old 17th June 2011, 12:19 AM   #127
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Quote:
Originally Posted by hisense View Post
As size is not an issue for me...

...i definately want to try a tapped horn and have the BMS units sitting on the shelf.

I have been trying to learn about horns and playing with hornresp and will get stuck in if there is a chance adaption of the design will help get the driver / cab combo to start rollling of at 40hz rather than 45hz as it does currently.
Since size is not an issue, check this thread where Xoc1, epa and others have already modeled a few enclosures around the 18N850v2 to play 30-35Hz and up!
C/E/X PA Flat to 30 (FT30) PA TH Awesomeness

Hope this helps!
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Old 17th June 2011, 02:02 AM   #128
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Quote:
Originally Posted by CRESCENDO View Post
Left: 18Sound 18LW2400 vs Pro 5100 (SPL)
Center: B&C 18SW115 vs Pro 5100 (SPL)
Right: B&C 18SW115 vs Pro 5100 (Group Delay)

(In Hornresp, the Pro 5100 reaches its AES power rating of 1000W way before xmax)
Correction: the Pro 5100 is currently $1270, not $900..
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Old 17th June 2011, 12:29 PM   #129
hisense is offline hisense  United Kingdom
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Thanks guys, i did look at the 30hz thread and will give it some more attention - will probably opt for this 38hz version as i can see quite a lot of work has gone into it so far and design has evolved.

Either way will post pics and measurement results once i have completed the first cab.

Cheers
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Old 18th June 2011, 02:49 AM   #130
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Click the image to open in full size.

Quick question...are these all strips of 18mm ply? Or is this brace cut from a single piece then the triangles are cut out to reduce the volume the bracing takes up?
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