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B&C DCM50/Fastlane Eliptrac 400 sensitivity?


jorjen

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Could not find what I was looking for using the search function and I have no means to measure it so I have to approach it in this manner.

 

For purposes of tap settings on the autoformer, what would you guess the sensitivity of the DCM50 to be "on the horn"? I believe the sensitivity of the driver alone to be 108.5db if I am not mistaken.

 

I am using 0-4 on the 3636 now for -3.0 db. I know what I like and have been experimenting but wanted to hear some additional thoughts.

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46 minutes ago, pzannucci said:

What bottom end?

 

Stock La Scala bottom.

 

22 minutes ago, Deang said:

Knowing that will help a little, but you really need to know the increase or decrease in gain from the horn. I’m sure Dave knows this - that’s the number you need. 

You are right of course Dean. I will hit-up Dave.

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12 hours ago, justinsweber said:

I ran mine at -12db down.  Sounded amazing. 

Wow Justin! I have never tried anything more than -6db. Seems kinda low for the 2404's which are 105db and the La Scala bins which are in that ballpark doesn't it? Guess I could try more attenuation just for the heck of it.

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98db 15c minus 108.5 B&C dcm50 = gets us to 10.5. I pulled it down to -12 to get better integration.  

 

98 + 3db being horn loaded or so.  101db as a realistic starting point. 101-108.5=7.5 

if it were me. I’d try 8db, 9db and 10db to see how thing sound.  

 

 

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On 5/12/2018 at 12:00 PM, Deang said:

If -3dB sounds right to you, you’re probably right in the ballpark - and don’t forget, that swamping resistor is stealing a little as well. 

Made sense to me too and that is where I have had it set.

 

However, after reading the post by Justin I decided more experimentation was warranted. Since I have never tried anything more than -6 I knocked them down to -12.

 

One thing that happened immediately was that it eliminated two  problems that I have been trying to get rid of for some time now. Even thought it was my room at times. One was an edginess/harshness in the mid-range the other was lack of bass. Sounded better. But at -12 things sounded a little dark so I tried -9db and have been thrilled with the improvement.

 

Then this week I talked to Dave and before knowing what I had done he suggested trying -9db with his horn and the 8 ohm DCM50. He thought I had probably had it running pretty hot with my previous setting.

 

He could not have been more spot on. Bass is back and the sound is smooth as silk.

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On 5/13/2018 at 10:29 AM, justinsweber said:

98db 15c minus 108.5 B&C dcm50 = gets us to 10.5. I pulled it down to -12 to get better integration.  

 

98 + 3db being horn loaded or so.  101db as a realistic starting point. 101-108.5=7.5 

if it were me. I’d try 8db, 9db and 10db to see how thing sound.  

 

 

And you were right on target as well Justin, thank you Sir!

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Just something to think about ...

 

The Atlas PD5-VH (K-55-V) is over 110dB. When you put it on the K-400, it drops to 107dB. We then attenuate another 3dB to get it to match the bass bin (104dB).

 

Since you're running a network with a swamping resistor, it doesn't really matter that the B&C is 8 ohms instead of 16. Normally there would be a 3dB gain with the 8 ohm driver, but not in this case. Al has had several posts on this in the past, and the numbers are virtually the same.

 

Assuming there is no loss in gain from the horn (not likely), -9dB means your midrange is tapped out like a Heresy.

 

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Call me crazy, I run my BMS4592 mid driver on Dave's large eliptrac lens down 13.7 dB. This is on top of Lascala bass bins with KHorn bass bins in parallel tucked into corners. I think the BMS and B and C drivers are of similar effficiency.

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19 hours ago, babadono said:

I think the BMS and B and C drivers are of similar efficiency.

No, the BMS is 10dB more sensitive (118dB/2.83V). 12-13dB down is the normal setting for that particular driver.

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