[usp1]

You shouldn't hear any, you are correct. But with fmods, who knows what freq and impedance they are actually built for.  Remember the formula above, you may just want to build one for better results.

Sorry it's not working out

Jp

High or low pass, you will get better results with your own creation

They are supposedly designed to have a -3 db point at the rated frequency with an impedance of 22Kohms and they specify the following drift.
50hz brown band (54hz @ 10K / 46hz @ 47K)
70hz purple band (76hz @ 10K / 65hz @ 47K)

The Crown xls402 I connected to has an input impedance of 10K unbalanced and 20K balance. Not sure which one to consider since I used an RCA to XLR cable. But in either case with a 50hz nominal I should at worst see a 54hz cut-off.

[Danny Richie]

Another popular option with those Gallo's is to power the lower woofer with a sub-woofer plate amp. And if you get one with a phase control too that will really help. The passive version has a bit of a dipped out area in the crossover region that a shift in phase might help a lot.

[jtwrace]

Another popular option with those Gallo's is to power the lower woofer with a sub-woofer plate amp. And if you get one with a phase control too that will really help. The passive version has a bit of a dipped out area in the crossover region that a shift in phase might help a lot.

Maybe you and the Ninja should offer a complete ready to install package.  Then you can have your buddy Ron review it. 


There are a lot of Gallo's out there!

[usp1]

Another popular option with those Gallo's is to power the lower woofer with a sub-woofer plate amp. And if you get one with a phase control too that will really help. The passive version has a bit of a dipped out area in the crossover region that a shift in phase might help a lot.

Do I need one or two plate amps to do this?

[BobRex]

Plate amps are mono, so you will need 2 of them.  You can also look at the Dayton sub amp, parts connexion has it.  If memory serves, that is a stereo unit.

[usp1]

Plate amps are mono, so you will need 2 of them.  You can also look at the Dayton sub amp, parts connexion has it.  If memory serves, that is a stereo unit.

I looked at the Dayton before but was trying to avoid spending that much. Gallo sells a sub amp and they go used for around the same as the Dayton amps.

[bdp24]

I still have to figure out a low pass filter  since the fmod cable does not seem to be a very good solution. The fmod cable I purchased is supposed to give me a low pass filter with cut-off freq of either 70hz or 50hz depending on cable orientation. Regrdless of which cut-off I use, I can hear vocals if I just power the second voice coil on my Gallo 3.1s. The vocals are significantly attenuated, but I would have expected that with a 50hz cut-off and a 12 db slope I should not hear any vocals at all.

Not only does the FMod connector not know the input impedance of your power amp, using one results in another connection the signal has to pass through. And I'm sure the FMods are made of brass, a crappy material to put in the path of the delicate signal. Brass contains tin, for God's sake! Most RCA jacks (male and female) are made of brass.

[Davey]

The Fmod's are a compromised design.  There's an internal loading resistor that's quite a bit lower value than a typical amplifier input impedance.  This allows to optimize the capacitor/resistor values and make the units somewhat universal across various source/load combinations.  However, the lower impedance levels can provide significant insertion loss and skewing of the advertised specifications if the source output impedance is fairly high.

The best bet when constructing DIY inline crossovers is always to build your own.  You have total control of the design and your source output resistance and load input resistance are (or should be) fully known beforehand.  There's no reason you can't achieve your target objective exactly.

Dave.

[Danny Richie]

The Fmod's are a compromised design.  There's an internal loading resistor that's quite a bit lower value than a typical amplifier input impedance.  This allows to optimize the capacitor/resistor values and make the units somewhat universal across various source/load combinations.  However, the lower impedance levels can provide significant insertion loss and skewing of the advertised specifications if the source output impedance is fairly high.

The best bet when constructing DIY inline crossovers is always to build your own.  You have total control of the design and your source output resistance and load input resistance are (or should be) fully known beforehand.  There's no reason you can't achieve your target objective exactly.

Dave.

I agree 100%.

[Danny Richie]

I looked at the Dayton before but was trying to avoid spending that much. Gallo sells a sub amp and they go used for around the same as the Dayton amps.

It really is the best solution.

[usp1]

The Fmod's are a compromised design.  There's an internal loading resistor that's quite a bit lower value than a typical amplifier input impedance.  This allows to optimize the capacitor/resistor values and make the units somewhat universal across various source/load combinations.  However, the lower impedance levels can provide significant insertion loss and skewing of the advertised specifications if the source output impedance is fairly high.

The best bet when constructing DIY inline crossovers is always to build your own.  You have total control of the design and your source output resistance and load input resistance are (or should be) fully known beforehand.  There's no reason you can't achieve your target objective exactly.

Dave.

To achieve what I want, do I simply put an inductor of an appropriate value inline with the positive wire of the interconnect feeding the amp? I think this would give me a first order crossover (correct?).

[usp1]

It really is the best solution.

I may have to go this route because of some issues I have had with the alternative solution that I tried. I will give a brief description and perhaps someone can help me identify where the problem might be.

Apart from the fact that the FMODS are a terrible low-pass filter, I have been experiencing some real problems with my McCormack DNA-1 blowing fuses with the new configuration.  This is how I connected my system: The Dodd pre has two outputs. I used one to connect to the DNA-1 which then connects to the standard posts on the Gallo 3.1. I used the second output from the Dodd and used the inline FMODS to connect to a Crown XLS 402 which then was connected to the "subwoofer" posts of the Gallo. (the subwoofer posts are the ones that connect to the second voice coil of the woofer.) Everything runs for a short while (5 to 30 minutes) After that the McCormack will blow its fuse. So far I have blown the Mains AC fuse twice and the internal fuse on the circuit board once. Steve McCormack told me that this happening because the two amps are somehow getting connected! I am now very hesitant to try anything for fear of damaging the amps. Could it be the outputs on the Dodd pre? Or something in the speakers?

Each time the fuses have blown, I have been using the two outputs on the Dodd. I tried in between (before I realized the issue) using one output on the Dodd for the DNA-1 and then using the analog output on a Benchmark Pre for the Crown. That ran well for at least an hour. I don't want to try it again for fear of damaging an amp.

[Danny Richie]

usp1,

You can't connect one amp to one voice coil and a separate amp to the other voice coil. Just let one amp drive both voice coils. Make sure the impedance is not too low also.

In the end you will need to get a good sub-woofer plate amp so that you have some flexibility and control over the bottom end.

[usp1]

usp1,

You can't connect one amp to one voice coil and a separate amp to the other voice coil. Just let one amp drive both voice coils. Make sure the impedance is not too low also.

In the end you will need to get a good sub-woofer plate amp so that you have some flexibility and control over the bottom end.

Danny,

The Gallos are designed to do exactly that. They have two sets of binding posts. The top sets drives the tweeter, the mid-range and one voice coil of the woofer. The second set of binding posts connects to the second voice coil of the woofer. The recommended way to get best performance is to use one amp with the top set of binding posts and their Gallo SA sub amp with the second binding posts! As long as the lower coil gets a signal that is low passed below 80 the results are supposed to be very good.

[Davey]

To achieve what I want, do I simply put an inductor of an appropriate value inline with the positive wire of the interconnect feeding the amp? I think this would give me a first order crossover (correct?).

It would, but I think you'll find the calculated inductor value is very high.    Inductors of this value are not easily sourced, or even DIY constructed.  This is why line-level low-pass filters are generally constructed with a series resistor followed by a shunted capacitor.

However, it's not clear to me that your equipment combination is even suitable for this type of passive-line-level filter.  I'm not that familiar with the Dodd preamp and its specifications.

Dave.

[Danny Richie]

Danny,

The Gallos are designed to do exactly that. They have two sets of binding posts. The top sets drives the tweeter, the mid-range and one voice coil of the woofer. The second set of binding posts connects to the second voice coil of the woofer. The recommended way to get best performance is to use one amp with the top set of binding posts and their Gallo SA sub amp with the second binding posts! As long as the lower coil gets a signal that is low passed below 80 the results are supposed to be very good.

They may indeed recommend that but to be honest, it is not a good idea. A simple phase delay could have one amp fighting the other over which way the woofer will move. And there is no good reason for doing it in the first place. It is also the likely cause of your amp blowing fuses.

[usp1]

They may indeed recommend that but to be honest, it is not a good idea. A simple phase delay could have one amp fighting the other over which way the woofer will move. And there is no good reason for doing it in the first place. It is also the likely cause of your amp blowing fuses.

I had the same misgivings about it as you do. In fact, I had posted something in this thread about that but took it down because I thought it may be off-topic. Short of tearing the speaker apart, since there is no way to use the second voice coil other than the Gallo recommended way, would you suggest that I not use the second voice coil at all?

[Danny Richie]

I had the same misgivings about it as you do. In fact, I had posted something in this thread about that but took it down because I thought it may be off-topic. Short of tearing the speaker apart, since there is no way to use the second voice coil other than the Gallo recommended way, would you suggest that I not use the second voice coil at all?

I'd pull the driver out and check the impedance of those voice coils first. A simple DCR check with give you the minimum impedance.

[ebag4]

I need to hi-pass the input to my amp.  The value I need for the BH (270K input impedance) is small, I am looking for something in the .0033uF to .0056uF range to give me a Hi-Pass in the 100Hz to 175Hz range (@ -3dB).  These sizes are not available in a Sonicap Platinum or a Jupiter cap so I am looking for alternatives.  One idea I had was to hi-pass the input to my Tortuga LDR volume control, it is said to have an input impedance roughly equivalent to a 20K pot, that should bring me into capacitor sizes more readily available in hi quality caps, are there any holes in this idea?

Thanks,
Ed

[jparkhur]

Ed.  I pmed you a present jon