Johannus Sweelinck 37 + 2 Walker B1000 Subwoofers + QSC CX302 Amp

[Ophicleide]

We will be adding 2 Walker B1000 subwoofers to a Johannus Sweelink 37. The subwoofers will have their own 2-channel QSC CX302 Amp. We will be using 2 existing connections from output #1 to the speakers. We're looking for help on how to route the signal from the organ's channel 1 through the 2-channel amp and to the speakers.



Any help/advice/suggestions will be greatly appreciated!

[Larason2]

I may be wrong depending on what those wires go to, but I wouldn’t recommend using those outputs. Those look like they’re going directly to drivers or speakers with a crossover, so they are probably the output of the Johannus’ own power amp, and if you tie into those you risk damaging the driver, the amp, or both, depending on how you do it. The amplifier load had to be always balanced with the output to avoid damage. The other problem is generally you want a mix down of all channels going to the subwoofer with a low pass filter to produce the appropriate bass.

Does the Johannus have some kind of Aux out? That would be the easiest. If not, you would want to tap into the signal before it goes to the amplifiers somehow. Usually these kinds of organs have an on board mixer. You would have to tap into the signal before it goes to the mixer, or after the mixer before it goes to the amps. If the onboard mixer is too hard to adjust, you can get an inexpensive mixer and place that in the audio chain to get the signal you desire.

[don60]

This organ likely uses the "dual-bridge" amplifier modules that can be configured, as the name implies, for two-channel single-ended use or single-channel bridged use. In bridged configuration, the two speaker output leads definitely do need to be floated above ground; attempting to ground either one will blow a speaker fuse or worse. Johannus almost always used bridge configuration for the bass channel, so this caution would apply here.

Having said that, I will add that Johannus routinely applied one of their powered sub cabinets such as the UL-5000 to these organs by tapping off the bass channel speaker outputs using a balanced (usually unshielded) cable run to an XLR connector having a resistive attenuator built in. This XLR would plug into the balanced input of the plate amplifer. I don't have one handy to recall the exact resistor values, but an attenuation of about 20x should do the trick.

If the OP is trying to drive single-ended amplifier inputs, an isolation transformer such as those made by Jensen would work.

As far as internal structure, earlier Johanni simply assigned audio Channel 1 as the "bass" channel and ran the 16' and 32' pedal stops through this channel. Later models used a bass crossover board that picked up all of the audio channels regardless of their stops and derived a bass channel from them, still typically assigned to audio Channel 1. Crossover frequency is around 80 Hz. The Sweelinck 37 is a later model and ought to have this crossover board--you can confirm by looking inside the console for a board downstream of the mixer that has RCA inputs and DIN outputs. Channel 1 output should go to a bridge amp that ends up at output 1 on the speaker terminal plate.

I suppose one could take single-ended bass output from the crossover board. However, there are advantages to doing things the Johannus way and using the amplifier output. The biggest consideration is that muting is implemented in the amplifier modules, so if you intercept the bass channel prior to the amp it will exhibit a serious turn-on and turn-off thump and will not be silenced when headphones are plugged in.

[Ophicleide]

Thanks for the replies. We will look into all of this. My wife is more technical/mechanical, so she may have some questions.

[don60]

Happy to help. I enjoy talking about Johannus products.

I see the QSC amp has XLR connectors, so you already have balanced inputs and are ready to go if you tap off the bass speaker output and go through a balanced resistive attenuator. The DIP switches on the back of the amp should allow you to drive both channels from one input.

[Ophicleide]

Happy to help. I enjoy talking about Johannus products.

I see the QSC amp has XLR connectors, so you already have balanced inputs and are ready to go if you tap off the bass speaker output and go through a balanced resistive attenuator. The DIP switches on the back of the amp should allow you to drive both channels from one input.

Thanks! We clearly have some more fishing around in the console to do. At this point, I don't know how to do an XLR connection from the bass speaker output. We have no idea what a balanced resistive attenuator is. You may have to dumb it down for us! 😁

[don60]

The XLR connectors are used for professional microphone wiring. They contain three pins numbered, oddly, 1 through 3. (The numbers are always printed next to the pins, so you do not even need a diagram to remember them.) Pin 1 is the shield (outer jacket) of the microphone cable; 2 and 3 are the inner conductors. In your case, at least for a short run, you do not need to fool with a shielded cable from the organ to the amplifier. So you take the two speaker wires from the bass channel 1 of the organ and run them to pins 2 and 3 of the connector--in this case a male XLR that would plug into the female socket on the amplifier.

Since the speaker output is much higher than line level, you cannot inject the organ output directly into the amplifier or you will overload it and possibly blow up the input circuitry. What Johannus does and what I recommend is to insert two resistors of equal value between the speaker wires and pins 2 and 3--the resistors would go "in series" with the input conductors.Then you would additionally install a smaller value resistor across pins 2 and 3 on the connector (amplifier side)--this resistor would be "in parallel." The three resistors together form a network that decreases the signal level to an acceptable value.

I have not looked at one of these little attenuators in an actual Johannus for several months and do not remember the resistor values offhand. Using 2 kohm for each of the inline resistors and 200 ohms for the parallel should work fine if you fine-tune the amplifier level control as well. Start with the level control at minimum and cautiously raise it as you play some bass notes, stopping if something seems to be overloading.

With a careful solder job, the three resistors will fit inside the connector shell and not require an outboard terminal strip.

I'm sorry that I do not have access to my scanner at the moment; otherwise, I would sketch it out. If the above is unclear, I might be able to come up with an alternative method of posting a schematic.

[myorgan]

So you take the two speaker wires from the bass channel 1 of the organ and run them to pins 2 and 3 of the connector--in this case a male XLR that would plug into the female socket on the amplifier.

@don60

On a Johannus, are there any concerns about phase when making the connections for the bass? My guess is "no" since you stated earlier the bass from all channels is combined in Channel 1 through a crossover. I just want to verify for the benefit of the OP.

Thanks in advance.

Michael

[myorgan]

So you take the two speaker wires from the bass channel 1 of the organ and run them to pins 2 and 3 of the connector--in this case a male XLR that would plug into the female socket on the amplifier.

@don60

On a Johannus, are there any concerns about phase when making the connections for the bass? My guess is "no" since you stated earlier the bass from all channels is combined in Channel 1 through a crossover. I just want to verify for the benefit of the OP.

Thanks in advance.

Michael

[don60]

Michael, I never paid attention to phase in these cases and have not noticed any bass deficiencies. As you noted, all low frequencies across all of the channels play through this one speaker, so cancellation there is not an issue. Strictly speaking, in the crossover region both the bass and main channels are carrying some content and they should be phased. But in practice I have not detected this need. Even when I did note-by-note voicing, I have not found a need to bump up or bump down the levels in this transition region depending on the sub phasing. I know that boutique speaker companies such as Definitive make a huge deal about "phasing" their subs, but maybe it's just hype like the alleged need for $10 per foot speaker cable. It's worth playing with both phasings just to be sure, though, during an organ installation.

[Ophicleide]

Thank you, don60 for taking the time to help us with this. We really appreciate it. Your post above does clear some things up, but there are still things we don't fully understand, such as the resistors and attenuators and where we would get them. The speakers and amplifier will not likely be delivered to the church for a week or two, so we still have time to improve our learning curve!

[don60]

Mouser Electronics, Digi-Key, and Parts Express are all the go-to suppliers for most of us in the organ business. Mouser and Digi-Key will have single resistors available in the full range of values, and all three suppliers carry the connectors. The basic part number for a three-pin male XLR is A3M, with various prefixes and suffixes denoting body material and pin plating.

[Ophicleide]

Mouser Electronics, Digi-Key, and Parts Express are all the go-to suppliers for most of us in the organ business. Mouser and Digi-Key will have single resistors available in the full range of values, and all three suppliers carry the connectors. The basic part number for a three-pin male XLR is A3M, with various prefixes and suffixes denoting body material and pin plating.

Thank you for all your suggestions in this thread! Our Walker subs and amp will be arriving this week, so we need to get our heads around these connections and the actual resistors and connectors we need. A search at mouser.com renders a multitude of options. Would you be so kind as to post some links to the actual parts we'll need? A look at these parts will also help us better visualize this project. We're still not able to fully visualize what gets connected to what. Any further assistance/suggestions will be much appreciated!

[don60]

I started using Yageo resistors many years ago due to low cost and wide availability. A 1/4 watt 5% rating would be sufficient for your needs. Here is the link to a typical value from which you can deduce the part numbers of the others that you might need:

https://www.mouser.com/ProductDetail...WHjNLfgw%3D%3D

I will try to prepare a sketch of the attenuator circuit required at the sub cabinet. I will be guessing on the resistor values but should be close. You can always check the volume level and adjust as needed.

[Ophicleide]

I've reached out to our Rep from Walker Technical for suggestions, with a link to this thread, and got this reply:

"I reviewed your email and the thread you have on the organ forum. We do not recommend connecting an amplifier in that manner. While technically you can do that as a last resort, I find it hard to believe there isn't somewhere in the organ that you can pick up the signal before it goes to their amplifier. I would suggest contacting your local Johannus technician and asking him to help you connect the amp.

Since we don't connect our amps in the manner the folks on the thread were describing, we're not in a position to make any suggestions as to the values of resistors to use. If you do pursue connecting the amp in that manner, please make sure the expression shoes on the organ are closed so the input voltage isn't too high and damages the amplifier."

I tend to agree with him that it would be best to bypass the organ's amplifier, if possible. Does anyone know how to do this? However, the feed from the organ's amp is for all 16' manual and pedal stops and the one pedal 32. Assuming the organ's amp controls the expression/volume, unless we can isolate the pedal stops that do not need to be under expression, none of these stops may be under expression.

[don60]

Walker rep is, with respect, full of crap. I AM a Johannus tech with access to all of their factory data, and Johannus has used the approach I described quite successfully for many years. It has multiple benefits with no downsides other than giving heartburn to Walker reps.

As I said before, muting for turn on/turn off thump elimination and for headphone use is implemented IN THE POWER AMPLIFIERS. If you bypass the subwoofer power amp, you will lose this muting and have to go through five other convoluted steps to try to re-implement it another way.

This approach is quite common in live sound--i.e., pulling a signal off a speaker output and attenuating it to line level for injection into a mixer or other similar equipment. If you are nervous about ground loops, a high-quality isolation transformer will provide all the protection you need.

The advice about starting with the expression shoes closed is good. Keep levels low while dialing in the gain settings on new equipment.

Expression in these organs is implemented digitally on the processor board.

[Ophicleide]

Assuming the organ's amp controls the expression/volume, unless we can isolate the pedal stops that do not need to be under expression, none of these stops may be under expression.

Our Walker Rep responded:

"I don't know of any manufacturers who are presently using the amplifiers to do the expression function. There were a couple that did that back in the 70's/early 80's but as far as I know, everyone handles the expression in their audio processing and preamp sections of the tone generating system. I would be surprised if Johannus does that. Hopefully, your technician can shed some light on that as well. I would think the expression happens before the signal gets sent to the amplifier."

[mrdc2000]

There seems to be some vital information missing, such as: Since the new Walker woofers are external, what other external speakers is he using ?
Are the internal speakers still being used, including the 12" woofer ?

[Ophicleide]

There seems to be some vital information missing, such as: Since the new Walker woofers are external, what other external speakers is he using ?
Are the internal speakers still being used, including the 12" woofer ?

There are at least four external Johannus speaker cabinets being used. There are no internal speakers. The organ never had dedicated subwoofers. The original installers just used the woofer from a standard cabinet for the bass output.

[mrdc2000]

A very unusual situation, all Sweelincks that I have ever seen or heard of, all came with internal speakers. Externals were optional.
Please send us a few pictures of the console, showing the keyboard and stop layouts as well as the electronics from the back.
Can you confirm when the organ was manufactured ? Thank you.

[don60]

I have seen plenty of Sweelincks that have no internal speakers. Whether internals were standard or not, they could certainly have been deleted on special order.