Balanced Attenuator for Stereo Monitors + Subwoofer

GroupDIY Audio Forum

Help Support GroupDIY Audio Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Freddy G

Well-known member
Joined
Jun 4, 2004
Messages
484
Location
Canada
Hi!

I would like to build a stepped attenuator to control my monitors. I have lots of Elma A4 switch parts and I can figure out how to wire them for balanced stereo operation. But here's the thing....I have a subwoofer (balanced input as well) and I would like to if possible control it's level at the same time with the same switch. I don't know how to do that. I know I need 4 decks for balanced stereo. Do I need only one more deck for the sub? and how would I sum the L + R signal to mono just for the sub.

Thanks in advance!

Freddy
 
Not enough info. Where in the signal chain is the crossover? With some (many?) subs the crossover is in the actual subwoofer electronics.

Bri
 
Not enough info. Where in the signal chain is the crossover? With some (many?) subs the crossover is in the actual subwoofer electronics.

Bri
Brian,
The monitors are Meyer Sound Hd1s and the sub is a Meyer UMS 1P. Just got them....i think the sub has a low pass filter
 
I didn't spend much time searching the 'net for manuals of each model but what I found for the UMS 1P made no mention of a crossover. The limited info I found for the HD1s didn't seem to indicate inclusion of a crossover.

Perhaps you can post links for the manuals so we can sort through this. There is a chance you may require an external crossover.

Bri
 
"Integrating a built-in low-pass crossover while accepting a full-range signal, the UMS-1P’s input allows for simple daisy-chain signal distribution and eliminates the need for external crossovers."

Looks like the sub has a loop-through output without a crossover so you'd just feed a stereo signal to the sub and loop out to the speakers
 
"Integrating a built-in low-pass crossover while accepting a full-range signal, the UMS-1P’s input allows for simple daisy-chain signal distribution and eliminates the need for external crossovers."

Looks like the sub has a loop-through output without a crossover so you'd just feed a stereo signal to the sub and loop out to the speakers
Interesting. I had found this manual last night:

https://cdn-docs.av-iq.com/instructions/Meyer Sound UMS-1P Operating Instructions.pdf

I'm probably blind, but saw no mention of the crossover. I'll "leave the ball in Meyer's court'. <g>

Bri
 
"Integrating a built-in low-pass crossover while accepting a full-range signal, the UMS-1P’s input allows for simple daisy-chain signal distribution and eliminates the need for external crossovers."

Looks like the sub has a loop-through output without a crossover so you'd just feed a stereo signal to the sub and loop out to the speakers
Thanks for digging that up pvision! i hadn't seen that datasheet... UMS-1P datasheet
Interesting. I had found this manual last night:

https://cdn-docs.av-iq.com/instructions/Meyer Sound UMS-1P Operating Instructions.pdf

I'm probably blind, but saw no mention of the crossover. I'll "leave the ball in Meyer's court'. <g>

Bri
Brian, that's the manual I found too last night. I called Meyer this morning, but I didn't get to speak to a tech. They took my number and said someone will call back.... still waiting for that call.....
But according to the datasheet then, I don't need a crossover....yeah!

pvision suggests I can send a stereo signal to the sub and loop out to the speakers. But it's just a mono loop through. In any case....looks like this clears some things up eh?
 
@Freddy G I am still confused. The typical powered subwoofers I've seen have stereo line inputs as well as stereo line outs. An internal crossover takes the full range signal, feeds the bass info to the internal amps and sends the high passed signal to the output jacks. Hence, four audio connectors on the sub.

Perhaps the manual we both found is a counterfeit...lol.....but there aren't that many jacks on the sub according to the manual.

Bri
 
@Freddy G I am still confused. The typical powered subwoofers I've seen have stereo line inputs as well as stereo line outs. An internal crossover takes the full range signal, feeds the bass info to the internal amps and sends the high passed signal to the output jacks. Hence, four audio connectors on the sub.

Perhaps the manual we both found is a counterfeit...lol.....but there aren't that many jacks on the sub according to the manual.

Bri
yes, it seems it's a bit of a struggle to get clear info from Meyer! I did read on the datasheet that they have different input modules available....one of which does two inputs summed to mono.
Here's a pic of mine....if we trust that little diagram it looks like there is no high pass processing going on to the looped out.

sub.jpg
 
yes, it seems it's a bit of a struggle to get clear info from Meyer! I did read on the datasheet that they have different input modules available....one of which does two inputs summed to mono.
Here's a pic of mine....if we trust that little diagram it looks like there is no high pass processing going on to the looped out.

View attachment 127134
Your picture matches up with the manual we downloaded. The only other module the book described is some sort of "administration" gizmo. Perhaps that module included a crossover????

Bri
 
Your picture matches up with the manual we downloaded. The only other module the book described is some sort of "administration" gizmo. Perhaps that module included a crossover????

Bri
I just ran some full range audio into the sub. It's low passing for sure....
 
Could be just the inherent response of the internal amp plus the speakers. Still doesn't create a high-passed signal for the main speaker pair.

Bri
Right. But for what it's worth, I ran the sub and HD1s feeding them all full range and I will say I liked it! So at this point I'm happy with not worrying about it and just figuring out how to implement an attenuator for all three with feeding a L+R sum to the sub.
 
Right. But for what it's worth, I ran the sub and HD1s feeding them all full range and I will say I liked it! So at this point I'm happy with not worrying about it and just figuring out how to implement an attenuator for all three with feeding a L+R sum to the sub.
OK...I won't belabor the point that the crossover is intended to keep any heavy LF from rattling the main stereo pair.

I need to find a manual for the main speakers. Do they have a level control pot like the subwoofer?

Bri
 
OK....found a manual. Damn, just a +4/-10 switch. Makes it tricky to balance levels between the sub and mains.

I'm sure you want to keep the whole attenuator setup passive, but I'm seeing some "design issues". Breaking it down into "bite sizes".....

A passive LR summer for the sub will cause at least a 6 dB drop. Hence my question about level control pots on the main speakers.

In addition, adding a passive summer after a passive attenuator control...I see a real possibility of crosstalk between channels.

What is the signal source driving this system?

This might very well require an additional 2 poles on the attenuator switch....ie, create a LR sum before the attenuator.

Bri
 
Oh what a tangled web we weave! <g> For some reason I need a mental challenge this week....lol!

OK, I retract the idea of complicating your stepped attenuator. Sum for the sub needs to happen post attenuator. Can you purchase the (unknown to me) Meyer summing module somewhere?

In this entire system you will need a method(s) to balance levels between the sub and mains without causing problems like crosstalk from the summer.

The Antelope should have a relative Low output impedance....which is useful! Problem as I see it is cascading a bunch of passive circuitry "post Antelope".

You mentioned already doing a "test listen" with what is at hand. I am not an acoustics guru and I don't know your control room acoustics. At his early part of the project, can you do any sort of acoustical frequency response sweeps with this "test setup" to see how well balanced the sub is with the mains?

I am overthinking....you can probably smell burning brain cells wafting all the way to Canada! <g>.

Bri
 
Back
Top