[SoCalWJS]

Hey guys,

Yes the FMod's are 12db per octave.

The single cap starts a 6db per octave roll. Where the roll starts depends on the input impedance of the amp being used. Typically a value of .33uF to .47uF works well with most amps, but some might require something a little larger or smaller.

The Super-V's did not come with a high pass filter for the P-Audio co-axial drivers. The high impedance rise in the lower end kept them from being effected too much by the lower frequency ranges. But I did find them to sound a little cleaner with a line level RCA type filter.

My favorite cap for the application has been the Sonicap Platinum's. They are not to expensive in the smaller values either.

Is there a formula for this? I know that the published input impedance for my amp is 20 k ohms.

[SoCalWJS]

A very inexpensive way to try them is to buy a male and female RCA connector and wire the Sonicap Platinum between them.  Cardas makes some very good RCA connectors like Gary Dodd uses on his tube buffers and for cables.   Probably cost about $80 for the connectors.  You can use 2%silver eutectic solder from Radio Shack.  Very good stuff, or use the Cardas Quad Eutectic solder.  You will only need a small amount of it.

Just a thought.

I need to figure out how to do this. I can see that on the RCA cables I have, the Cap is soldered to another wire that is twisted along with the standard wires and that it is somehow terminated on the connectors, but I don't know how.

[HAL]

Yes,

C = 1/(2*Pi*R*F-3dB), where:

R = 20K ohms
F-3dB = the 3dB down point for the filter, (i.e. 70Hz)

Solve for C, so for this example,

C = 0.114uF

For the high pass filter, just solder the capacitor between the two RCA connector center terminals (hot) and connect the two ground terminals with a straight wire.  A great starter circuit for DIY.   

[SoCalWJS]

Yes,

C = 1/(2*Pi*R*F-3dB), where:

R = 20K ohms
F-3dB = the 3dB down point for the filter, (i.e. 70Hz)

Solve for C, so for this example,

C = 0.114uF

For the high pass filter, just solder the capacitor between the two RCA connector center terminals (hot) and connect the two ground terminals with a straight wire.  A great starter circuit for DIY.   

Thanks 

Now for part two of this whole thing - deciding on the crossover point.

Backstory:
I have pretty severe listening room space issues. I have left the LS-6s in the room just to the outside of the Super V's, as I had no other option. I recently got rid of a second row of seating and moved the first row back (further away from the speakers) which resulted in a considerable improvement in the sound. I finally decided it was time to move the LS-6s (plan was to put them behind the primary listening position and cover them with a heavy blanket until I decided what I wanted to do).

I decided that I wanted to try one thing before doing so - swap the speaker wires from the Super V's to the LS-6's (so that the LS-6s were running from about 80 Hz up and the Servo's from the Super V's were handling the Bass 

The only way to do this had the LS-6s in a completely different location than I had previously positioned them - they were still 3+ feet from the front wall, but now very near the side walls, so I toed them in a bit more than before.. I sat back and spun up a CD not expecting much.

I was wrong.

This has possibilities. Not quite as much depth of soundstage as the Super V's, but better than before, and very good sound.

Now I want to start dialing this setup in and decide if it's a long term solution. 

(so what I really need to figure out is a crossover point for the bottom end of the LS-6s - thinking somewhat lower than the existing 80 Hz [or so])

[HAL]

Do you have a way to measure the frequency response at your listening position?  REW is a good program for PC and works with a Radio Shack spl meter.  This would help alot in determining the issue.

Just a thought.

[SoCalWJS]

Do you have a way to measure the frequency response at your listening position?  REW is a good program for PC and works with a Radio Shack spl meter.  This would help alot in determining the issue.

Just a thought.

I have the OmniMic system, so I'll start playing around with that, but probably not until tomorrow. Company in town until then for a Funeral 

[Danny Richie]

Is there an easy and relatively inexpensive way to try these? (seems like soldering them into a fairly high quality RCA interconnect would be a little pricey)

There are two even less expensive ways to do this. It depends on your gear.

You can open up your amp and put the cap on the inside coming straight out of the center pin on the RCA input.

Or if you have two outputs on your pre-amp then you can add the cap inside the pre-amp on one of the outputs. I did that with my pre-amp.

[Danny Richie]

Is there a formula for this? I know that the published input impedance for my amp is 20 k ohms.

That is a pretty low input impedance. You might want to go with a .068uF or .082uF Value. 

[Danny Richie]

Oh yeah. Here is one of the filters used on the Serenity Acoustics Super-7's.

[SoCalWJS]

Do you have a way to measure the frequency response at your listening position?  REW is a good program for PC and works with a Radio Shack spl meter.  This would help alot in determining the issue.

Just a thought.

Started playing around with measurements. Not sure what the results really mean. I definitely have a dropout between 70-100 hz. Somewhere in the 5-10 db range depending on left channel only, right channel only, or combined. Figured I'd switch OFF the PEQ to see the changes....

Got virtually identical results 

Ah well. Spent a few minutes beforehand making sure that the speakers were really close to the same distances to front and side walls with same toe-in and letting the system warm up while listening.

I don't care about the measurements at this point.

This system sounds good. 

[Danny Richie]

You likely have a reflection that is arriving just out of phase with the on axis response at that point.

[SoCalWJS]

You likely have a reflection that is arriving just out of phase with the on axis response at that point.

Thanks


The biggest problem with the new arrangement is that I now sit back a bit further and a LARGE computer desk/hutch now is at the first side reflection point for the left speaker (second side reflection point for right speaker) and I haven't quite worked out how the room treatments I have can be utilized. The LS-6'es are so far towards the side walls that the corner of the computer desk almost blocks the direct line between the left speaker and the primary listening position. There is certainly no way to fit any absorption or diffusion on that side. 

[Danny Richie]

It could be the front wall as well. Any way that just for fun you can pull them out into the room another two feet and see (hear) what it does?

[SoCalWJS]

It could be the front wall as well. Any way that just for fun you can pull them out into the room another two feet and see (hear) what it does?

The rear of the speakers are currently about 3 feet (around 39") from the front wall. I would have t re-arrange a few things to move them further forward. I am currently stretched just about as far as I can go on speaker wires, so I would need to re-position amps/amp stands (and them suckers are heavy) as a minimum. Need to find new locations for a couple of other things also. I like finally being a bit further away from the speakers - hesitant to bring them close again.

I may remove the in-line caps first, but really would like to experiment with different value capacitors.

[HAL]

A way to experiment with capacitor values in the high pass filter is to start with the smallest value and then parallel other smaller values to the first.  Not the final way, just to try and see what sounds best.

[SoCalWJS]

Tried removing the inline capacitor - didn't like it. Would guess that relieving them of bottom octave(s) duty really cleans other things up everywhere else.

Went ahead and ordered 50 Hz and 70 Hz FMODS. I think its the cheapest way to figure out the crossover point, then if I figure that out, I'll order some Platinum caps in the correct value and try to figure out how to get them into the system (may just unsolder the existing 0.47 Value M Cap Supreme Silverfoils - should be pretty straightforward  )

[nickd]

John,

Those caps you have are Mundorf Silver/Oil .47 if I remember correctly. They are on the + side of 1/2 meter Kimber KCAG.

[SoCalWJS]

John,

Those caps you have are Mundorf Silver/Oil .47 if I remember correctly. They are on the + side of 1/2 meter Kimber KCAG.

Thanks Nick! I am still playing around with everything. There is just no end to fine tuning this stuff. (never quite satisfied - "Gee, this sure sounds good, but maybe it would sound even better if I just....".  )

[HAL]

A value of 0.47uF will have a -3dB point of 16Hz with your preamp.  Not doing much for low frequency roll-off.

The FMOD's are pretty good.  Easy to experiment with.

[bdp24]

Danny---The cross-over in the OB-5 rolls of the bottom-end (below 200Hz) of the signal it sends to the non-MTM woofers, right?