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Martin Logan Dynamo: high-pass filter?

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goose

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I am considering buying a used ML Dynamo sub, and have been reading the on-line PDF manual. The specs refer to a high-pass filter frequency of 70Hz, but nowhere can I find information on what that filter does. I would assume that it is applied to the L+R RCA passthrough, but assumptions have often been wrong before! Can anyone clarify that?
 

Tube60

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"high pass" or "low pass" are terms used in crossover designs. The high pass will be the output to your amplifier, and it's 70hz and higher in your case. Some high pass crossovers in those applications are variable, which is nice for fine tuning the system. The low pass side will be the lower frequencies below 70hz that the subwoofer will be working with.
HTH!
 
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goose

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Thanks for the reply, but perhaps I was too vague. I know what filters do in a general sense, I was wondering specifically how the filter in this sub is set-up. The manual makes no mention of it, aside from listing it in the specs. One connection diagram shows hooking up the sub using the RCA L+R passthrough (so the sub is "in-line" between the pre-amp and the power amp), but recommends setting the sub crossover the same as if the main speakers are full-range. This would be wrong if the filter was in place, but I cannot think of any other use for a high-pass filter unless it is there. So is the manual confused, or am I?
 

Genesis

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The Dynamo does not have a high pass filter, unlike the Depth or Descent. From what you mention, the Dynamo manual must be referring to high pass filter settings within the processor, assuming it has the capability to do so.
 
G

goose

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OK, thanks. It is kind of misleading to list it in the specs if the sub does not have one!
 
G

goose

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OK, that's just weird. I looked at the manuals for the Dynamo, Grotto, Depth, and Descent. Only Depth and Descent talk about high-pass filters in the manual, but only Dynamo and Grotto list a high-pass filter frequency in their spec. This seems backwards to me, having no spec for something that is there, and a spec for something that isn't!
 

Audiophiliac

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The Dynamo DOES have a 70Hz high pass filter on the RCA outputs. I was in the same situation when I bought mine. So I contacted ML, and that is the info I got. I have it hooked up between my receiver's pre-out/main-in jacks and am running small B&W M1s with the Dynamo on my PC, and it sounds great!

I dont know why they make the manuals so vague. :)
 
G

goose

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OK, so now I am even more confused than ever, but I will assume that because you have one and use it in this manner that you are right! Thanks.
 
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