How to incorporate Descent subwoofer into 2 ch system? High pass filter/crossover?

[preston]

Hi guys:

Just had the good fortune of incorporating a Descent subwoofer into a vintage two channel music system with good quality cone speakers.

The Descent has a built in low pass filter at 40hz and 70hz, but does not have a high pass filter. This lack of a high pass filter has me puzzled.

My preamp just has one set of left and right RCA jacks out (no low frequency out). To take full advantage of the Descent, and allow for a future stereo sub perhaps, I planned to do the following:

preamp left=>y cable=>Crossover/high filter=>poweramp =>left speaker
================>left sub input

preamp right =>y cable=>right Sub input
===============>Crossover/high filter=>poweramp=>right speaker

Question: How would you incorporate the sub into this system? Is my plan optimal? What are my alternatives to incorporate a high pass filter / crossover into the system? Best quality? Most economical? Best deal? Dumb ideas to avoid?

I have been researching and racking (or is that wracking?) my brain on this question for a while and would appreciate any input you might have.

Thanks,

 

[VanDaRo]

I'll bet that it does have a high-pass filter that is active when you use the RCA out jacks. My guess is that it's set at 70 or 80 Hz. Check the on-line reviews as the reviewer often does substantial research on these types of things.

It IS surprising that ML decided not to make that adjustable on the Decent, but did so with the Depth -- a lesser subwoofer.

Just set the low-pass filter at 40Hz if your speakers are full-range. Then ninja-tweak the system until you get it sounding killer. I set my Depth at 35Hz low pass / 70Hz high pass, and it is doing a great job. But by far the most important things to adjust are the placement and the sub volume knob.

Good luck. :rocker:

~VDR

 

[VanDaRo]

Preston -- Looks like you were correct. The Decent has no high pass built into it. You will be depending on its' natural roll-off, making the application of the volume knob all the more important.

But it's still a state-of-the-art subwoofer, so you should be able to make it work with darned near any loudspeaker.

~VDR

 

[amey01]

The lack of high-pass filter does not matter - very few people use them as it degrades signal going through yet another component.

I'd connect using a spare pair of preamp output jacks directly to the Descent. Leave your speaker connections alone. Then adjust the descent to blend in. You should not need high-pass because the Descent should be adjusted so that it operates only up to where your main speakers roll off.

Another way of connecting would be to use the speaker level inputs. Same as above - leave your existing speaker connections untouched and adjust the Descent accordingly. Many prefer this method as the sub will then take on the acoustic characteristics of your main amp.

That's one mighty world-class sub - enjoy!

 

[preston]

Hi Amey:

Thanks for your response. A few questions:

I'd connect using a spare pair of preamp output jacks directly to the Descent.

My preamp only has one set of RCA outs so do you see any downside to using Y cables to send the preamp signal to the sub and poweramp?

Another way of connecting would be to use the speaker level inputs. Same as above - leave your existing speaker connections untouched and adjust the Descent accordingly. Many prefer this method as the sub will then take on the acoustic characteristics of your main amp.

Do "speaker level inputs" mean passing a set of speaker wires from the power amp to the sub? Is that possible? The Descent only has:
- a LFE input via either a 3-pin mic jack or a single rca jack
- line level RCA inputs (left & right)
http://www.us.martinlogan.com/pdf/manuals/manual_descent.pdf

Thanks again,

 

[amey01]

Hi Amey:

Thanks for your response. A few questions:



My preamp only has one set of RCA outs so do you see any downside to using Y cables to send the preamp signal to the sub and poweramp?




Do "speaker level inputs" mean passing a set of speaker wires from the power amp to the sub? Is that possible? The Descent only has:
- a LFE input via either a 3-pin mic jack or a single rca jack
- line level RCA inputs (left & right)
http://www.us.martinlogan.com/pdf/manuals/manual_descent.pdf

Thanks again,

1: I wouldn't like to use a Y cable - it's certainly not ideal, but may be acceptable. I don't have any experience so I can't comment. Just make sure whatever Y lead you use is as good a qualitiy (or better) than what you're using now.

2: "Speaker Level Inputs" certainly do mean you run speaker cable from your amp into the sub. It doesn't place any extra load on the amp - the sub is purely taking its signal from the amp - the amp is not "driving" it in any way. I didn't realise the Descent didn't have speaker level inputs.

I guess that means you're going to need a Y cable. Anyone else - maybe Descent owners?

 

[amey01]

One more possibility - does the power amp have loop RCA outputs? Some do. You could then connect the sub to the power amp.

Another method would be to connect a Y-splitter at the power amp (good quality of course) rahter than a Y cable.

 

[User211]

Quote VanDaRo: "Then ninja-tweak the system until you get it sounding killer."

Best sentence I have read for a while!!!!

I have a Descent. Simply put - use the y-splitters. Or get a pre-amp with two sets of RCA outs. A tape record out would work fine...

Enjoy. Tis a great sub.

Justin

 

[tonyc]

Another alternative to Y splitters would be analog bass management such as the Outlaw Audio ICBM. Although designed for surround sound it works just as well on a 2 channel system. I have used mine in a HT system with Aeons and a Descent for several years now and this baby is quite transparent. Downside is no balanced ins/outs and the need for extra interconnects. Can be purchased at www.outlawaudio.com. About $250.

 

[preston]

Thanks for the variety of replies relating to the integration of a Descent subwoofer. I also spoke with Customer Service at Martin Logan, a local Martin Logan rep and several certified (in the British sense!) audio gurus regarding connection the Descent sub.

Interestingly enough, bottom line seems to be that most audiophiles connect their Descent subs directly to their preamps, and let the mains run the full signal, without a high pass filter. This setup seems to have the advantage of cleaner signals and simplified integration of sub and mains. Key caveats include:

- good quality set of mains
- good quality poweramp with lots of "headroom"
- ability to integrate sub's and mains' signals in your particular room with this set up
- I am sure there are others that you can, and will, add

My solution (for now!):

* Good quality RCA Y jacks out of my only set of preamp L + R outputs
- one set to sub's line-in
- one to set to power amp's line-in

* I tried integrating sub by ear and came close

* Obtained great sub placement/ integration results using free RoomEq Wizard (REW) software at www.hometheatershack.com; settings were close to my manual efforts by ear but, noticeably better

* Still trying to figure how to equalize sub with the REW software but given results with integration, I will continue learning REW

* Used Descent's built in 70hz low pass filter (not the 40hz). REW helped me select low pass filter for my room and mains combination

==>Bottom line:
With good placement and a simple two wire direct connection to my preamp, the Descent sub sounds great. It provides smooth, very deep bass, integrates into my system perfectly and, most importantly to me, is not localizable in my room. This is the first sub I have owned that has really added to the audio experience.