[Atlplasma]

I recently dropped a sub into my system and am considering different options for bass management. One suggestion was to add in some FMODs. Does anyone have a suggestion for what might work with the Ncores?

[genjamon]

FMOD? What's that?

I have some cables that convert from speaker outputs on amp to RCA jacks to benefit from the higher gain from amp level into sub input rather than line level. It also helps the subs to have same character as entire amplification chain instead of just preamp. Ed Schilling of the Horn Shoppe made mine, but I think there may be other companies that make them too. That's how I'm doing it with my subs right now anyway.

[Atlplasma]

FMOD? What's that?

I have some cables that convert from speaker outputs on amp to RCA jacks to benefit from the higher gain from amp level into sub input rather than line level. It also helps the subs to have same character as entire amplification chain instead of just preamp. Ed Schilling of the Horn Shoppe made mine, but I think there may be other companies that make them too. That's how I'm doing it with my subs right now anyway.

Here is a link to the FMOD page on Parts Express. http://www.parts-express.com/term/fmod?srch=fmod&AID=1457483&PID=5567334&SID=skim23608X823435X932b5e5817af86778cb4c00a2fb9fbc8

And there description:

"What is an FMOD™? The FMOD™ is an active crossover simulator. It is better than a much more expensive electronic crossover that requires power to operate. FMODs™ are packaged in pairs and can be combined with other FMODs™ to obtain bandpass ranges or with other types of crossovers to change the slope and crossover frequency point. FMODs™ feature a 12 dB per octave crossover slope and are compatible with all RCA type input amps...simply place the FMOD™ in-line with the patch cable running between the source (head unit) and the amplifier."

[genjamon]

Ah, Ok, I think I get it now.  You mean to use Ncore as a subwoofer amp?  In my last comment I thought you meant just integrating a subwoofer into your main system, but I think I was wrong about that?  In that case, an FMOD makes more sense.  At first, I didn't really understand why you would want/need them instead of using in-built variable crossovers.  In my case, I just use the variable crossovers in the sub plate amps.  Sorry for the misunderstanding.

[jtwrace]

I use NCores on my bandpass subs which are fed from a DCX.  I hope to replace the DCX with the Hypex DLCP when it's released. 

[JohnR]

An "active crossover simulator"? 

[Julf]

An "active crossover simulator"? 

I guess they are line-level (impedance) passive filters - as in an inductor and a capacitor, and possibly some resistors. My concern is that as they are specified to work independent of amp impedance - something that is not really possible. Either they require a diving preamp with low enough impedance, or amp with high enough input impedance, or (most probably) both. Unless those assumptions are valid, you get nasty interactions.

[Atlplasma]

Thanks, Julf. That helps me to make up my mind about using the FMODs. I'm using Y splitters to take the left and right signals to my amp. But doing it without any bass management concerns me. I will probably buy something like an old M&K LFE-4/5 or a Velodyne SMS-1.

I don't want to crank up the volume some day and accidentally damage my two-way speakers.

[Julf]

I'm using Y splitters to take the left and right signals to my amp.

Is your sub system stereo or mono?

I will probably buy something like an old M&K LFE-4/5 or a Velodyne SMS-1.

yes, an active x-over or bass management system is the best solution. I am currently using a Behringer dcx2496, while waiting for the Hypex DSP unit or something similar.

[jtwrace]

I am currently using a Behringer dcx2496, while waiting for the Hypex DSP unit

+1

or something similar.

As you have probably seen http://www.diyaudio.com/forums/digital-line-level/215379-dsp-xover-project-part-2-a.html

[EuroDriver]

I would recommend against putting any kind of device or even a connection betwen your source and the Ncores

My audiolab 8200 CDQ has XLR and RCA outputs but with the warning that using both simultaneously can be deterimental to the sound.  With my W4S st-500 as power amp, before I built the Ncore, I could here no difference in SQ when my Velodyne SPL1200 Ultra has hooked up to the RCA output of the 8200 CDQ, but with the NCore there was a noticeable degradation.  I eliminated this degradation by using the highlevel inputs to the Velodyne, and then had only the XLR feeding the NCore from the Audiolab.

The SMS-1 has high level inputs and that would be my recommendation.  FYI the equalization feature on the SPL 1200 Ultra is next to useless for getting room modes under control.  You need a Velodyne DD series sub to have a meaningful level of equalization

I used REW software with a Behringer mic and a m-audio USB mic preamp to take frequency response measurements and then changing the sub placement to tame the room modes. In the worst placment cases the nodes were plus minus 20 dB !!

My suggestion is to use the SMS - 1,  two subs which are sealed and a good quanity of bass absorbtion panels to get a grip on room modes.  It´s hard to find a eq unit that has high level inputs, and the last thing you want to do is to stick an eq unit between your source and the NCore

my 2 cents after going down the wrong road with sub management and placement

[jtwrace]

I would recommend against putting any kind of device or even a connection betwen your source and the Ncores

Yes, that's why I run my speakers run full range and I blend my 4 subs into my mains.   

[Julf]

I would recommend against putting any kind of device or even a connection betwen your source and the Ncores

While it might minimize any noise and distortion, no connection at all between your source and the Ncores might also limit your musical enjoyment

Seriously, if you have a low enough impedance on your pre/source, and keep cables short enough, there should not be any negative impact.

I am of course assuming balanced connections. If you are using unbalanced, all I can say is "why?"

[EuroDriver]

LOL, I am still laughing till my stomach aches !

The velodyne only has RCA low level inputs. Between the main speakers and the subs high level inputs, I am using balanced mic cable, seems to work nicely

[Julf]

The velodyne only has RCA low level inputs. Between the main speakers and the subs high level inputs, I am using balanced mic cable, seems to work nicely

Absolutely - at high level signals, pretty much any cable will work, unless you are actually in the control room of a high voltage power plant or a radar station. Never tried the former, but have actually experienced the latter - a walkman was not useful for listening to music, but very useful for timing the beam rotation...