[Danny Richie]

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?

Yep.

[bdp24]

And in the Super-V, does the coax get a high-pass filtered signal at 200Hz, or at 300Hz?

[SoCalWJS]

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.

 

Shoulda done the math. Looks like I need something in the .159 or thereabout for what I'm after.

OK, now I'm not sure about FMODS - how do they work? All the info says is "Crossover simulator". If it's just a capacitor, wouldn't the crossover point change depending on input impedance of the Amp?

[bdp24]

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

Ric Schultz at Electronic Visionary Systems use to make over-the-top custom assemblies for things like this, using all-primo parts. I don't know if he's still doing it.

[Danny Richie]

OK, now I'm not sure about FMODS - how do they work? All the info says is "Crossover simulator". If it's just a capacitor, wouldn't the crossover point change depending on input impedance of the Amp?

The FMod's use a small surface mount type cap and a resistor in shunt to create the second order roll off.

And yes the input impedance of the amp actually determines the point at which the roll off begins. So despite what the "crossover point" rating says, it is still just a reference point via average impedance. 

[HAL]

Another easy way is a bunch of cap values a rotary switch, RCA connectors and clip leads to find the value of interest.

If you just need a pair, I can build them if you cannot.  I guess HAL can branch out into analog circuits like the old days of DIY with my Maggie IIB's.

The FMODs are 12dB/Oct filters.   They change frequency response based on load impedance, if I read the specs correctly.

If you want something fancier, maybe Danny has some like above, or Gary Dodd is looking for projects like earlier.

[Danny Richie]

And in the Super-V, does the coax get a high-pass filtered signal at 200Hz, or at 300Hz?

The Super-V uses no high pass filter. It just relies on the high impedance peak of the driver at Fs and it's natural roll off in open baffle.

They also have very high sensitivity so they actually see very little power reaching pretty solid SPL levels.

[SoCalWJS]

Another easy way is a bunch of cap values a rotary switch, RCA connectors and clip leads to find the value of interest.

If you just need a pair, I can build them if you cannot.  I guess HAL can branch out into analog circuits like the old days of DIY with my Maggie IIB's.

The FMODs are 12dB/Oct filters.   They change frequency response based on load impedance, if I read the specs correctly.

If you want something fancier, maybe Danny has some like above, or Gary Dodd is looking for projects like earlier.

The FMod's use a small surface mount type cap and a resistor in shunt to create the second order roll off.

And yes the input impedance of the amp actually determines the point at which the roll off begins. So despite what the "crossover point" rating says, it is still just a reference point via average impedance.

Starting to sound like I'll be guessing with the FMODS - do they publish the actual resistance values?

Probably need to make an educated best guess eventually and have something custom designed/built.

[bdp24]

If you're driving the Super-V's with a separate power amplifier, you can get the amp's input impedance from the manufacturer. I have one amp that has it printed right by it's RCA jacks.

[Danny Richie]

In my previous response I accidentally left out a zero to the figures I posted. I have corrected those values in my posts above.

Sorry about that.

[SoCalWJS]

In my previous response I accidentally left out a zero to the figures I posted. I have corrected those values in my posts above.

Sorry about that.

Thanks Danny.

I went back to that post - makes more sense now. Any reason that the Cap that I have now which says 0.47 would actually be a 0.047? (that would put it in the range where it would need to be to do some good)

[Danny Richie]

If it says .47uF then that is what it is. And that will not attenuate the lower end much at all.

[SoCalWJS]

FMODS are here. Poorly labeled (hard to tell the two values apart, so I put painters tape on 1 set) and zero info on the package or their website http://www.hlabs.com/products/attenuators/ about the values, so no way to tell via the formula of what the actual frequency will be in my system.

Now, can I break away from CFB long enough to do some listening/measuring? 

[HAL]

Are you sure you received the correct item?  The link you posted is for attenuators not FMOD high pass filters.

[SoCalWJS]

Are you sure you received the correct item?  The link you posted is for attenuators not FMOD high pass filters.

Now you got me double guessing - I'm not thoroughly confident I received what I ordered

Packaging is labeled as a hi pass (50 or 70 Hz) and an attenuator - is there such a thing?

This is what I ordered:

QTY     PartNumber     Product 
1    266-270    FMOD Crossover Pair 50 Hz High Pass
1    266-272    FMOD Crossover Pair 70 Hz High Pass
1       US Postal Priority Mail

This is what I got:

[HAL]

The Parts-Express model numbers match what is in the package.  Looks like it is a generic package.

[SoCalWJS]

The Parts-Express model numbers match what is in the package.  Looks like it is a generic package.

Whew! 

I went back and checked the shipping/packing slip and it looks right (catalog part number and the number on the package match), but the "Attenuator" part didn't even register.

I put the 50 Hz pair on and gave a quick listen and it sounded very poor. "Something is out of phase" I said to myself - and it's what I said last night when I dragged Anne upstairs to listen.

The new cat had previously knocked a wire loose behind one speaker. I had managed to hook it up backwards    Should be right now. Will give it another shot after Georgia/LSU (I'm a bit behind on the game at the moment).

[SoCalWJS]

Digging up my old thread so as to not further derail the OB/Rythmic thread......

After a bit of playing around, I think i finally have a fairly flat frequency response out of this hybrid system.

I ended up placing 2 242 absorber panels (8" thickness total) behind and in between and behind the speakers. They are on their sides so they only come up 2' off the floor - about the same height as the OB Servo portion of the Super V's. This seems to have reduced the cancellation of each channel by several db. Also, the right channel dropout is centered at 65 Hz and the right channel is centered at about 45 Hz. Between the two (reduced cancellation from absorption and different frequencies), I have a reasonably flat response, especially if I look at the 1/3 octave sweep  . At 1/48 octave, it still looks pretty good except for a moderate dropout at around 180-190 Hz. I can live with this result! 

Now I need to figure out if I can get a better decay. It's too quick below 2 KHz, then becomes better, but not as uniform above that frequency. I guess that means that the system sounds a bit "dead" below 2 KHz. The search continues.