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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Wireless and Communications => Topic started by: Dave Garoutte on February 02, 2019, 04:56:44 pm

Title: Is this real?
Post by: Dave Garoutte on February 02, 2019, 04:56:44 pm
I'm considering building an 8ch Senny wireless rack.
What are my combiner options?

 8 ch combiner  (https://www.ebay.com/i/323645004930?ul_noapp=true)

Thanks
Title: Re: Is this real?
Post by: Brian Jojade on February 02, 2019, 06:14:51 pm
That looks like an 8 channel SPLITTER.  Allows you to split the antenna signal to up to 8 mic receivers.  RF is relatively universal and you should be OK mixing and matching brands as long as you're working within the frequency bands of the equipment.

Now, I'm confused as to why it would have a display with antenna signal strength meters.  What is it actually measuring? 

Also, the BNC outputs don't look like the same size as the inputs.  You might need different patch cables to your receivers. to make it work.
Title: Re: Is this real?
Post by: Brad Harris on February 02, 2019, 09:38:36 pm
Yup, antenna Distro, not a Combiner ...

Meters are probably reading how much mW (crude signal strength meter) is at a the receiver input (not per frequency per say)

Also, SMA connectors for the output ... that many (18) BNC won't fit (nicely) into a 1u space


Brad
Title: Re: Is this real?
Post by: Scott Helmke on February 02, 2019, 09:42:36 pm
Looks like Chinese counterfeit crap. The front panel display is probably just a light-up with that information permanently displayed, and the antennas are some weird copy of Shure UA874 paddles. 

Also, SMA antenna outputs?!?
Title: Re: Is this real?
Post by: Ray Aberle on February 02, 2019, 10:36:31 pm
I'm considering building an 8ch Senny wireless rack.
What are my combiner options?
If you want to stay legit, grab Mike, or myself, or Tim, as Authorised Sennheiser Dealers and let one of us whip up a package. :-)

-Ray
Title: Re: Is this real?
Post by: Russell Ault on February 03, 2019, 12:35:13 am
8 ch combiner  (https://www.ebay.com/i/323645004930?ul_noapp=true)

You might have noticed that the listing doesn't actually say "Sennheiser" anywhere...

For 8 channels of Sennheiser G3/4 then a pair of ASA1s is pretty typically (Sennheiser does make an 8-channel distro, the ASA3000, but it's a lot more money).

Of course, if you're looking to save money (and don't mind going off the beaten path a ways) I've had very good experiences with a pair of good quality 8-channel unity gain cable TV distribution amplifiers...

-Russ
Title: Re: Is this real?
Post by: Lyle Williams on February 03, 2019, 07:55:50 am
An amplified splitter is likely to be the second least sophisticated piece of electronic equipment you will own (after a transformer-based wall-wart)


Title: Re: Is this real?
Post by: Dave Garoutte on February 03, 2019, 04:13:02 pm
Doh!  I didn't notice it was a splitter.  I figured it was cheapo, though.

I have two 4ch roadcases now with asa1 combiners and am looking at adding 8 more channels in one case.
Is it possible to combine the output from multiple combiners?
I'm hoping not to end up with an antenna farm if I need paddles.
Title: Re: Is this real?
Post by: Russell Ault on February 03, 2019, 05:53:46 pm
Doh!  I didn't notice it was a splitter.  I figured it was cheapo, though.

I have two 4ch roadcases now with asa1 combiners and am looking at adding 8 more channels in one case.
Is it possible to combine the output from multiple combiners?
I'm hoping not to end up with an antenna farm if I need paddles.

I think we might have a terminology issue here. A "combiner" is something that takes several RF signals and combines them into a single signal path. A splitter (or distro) is something that takes a single RF signal path and splits it into several identical copies. Combiners are used with IEM transmitters, taking several separate IEM signals and combining them into a single transmission line. Splitters are used with wireless microphone receivers, taking a single (typically pair of) antenna feeds and splitting them out to multiple receivers.

The ASA 1 is an 4-way antenna splitter, splitting one pair of antenna feeds to four separate wireless microphone receivers. A pair of ASA 1s can be cascaded into each other to create an 8-way splitter, which is the typical setup for 8-channel Sennheiser racks.

For IEMs, the Sennheiser 4-channel combiner is the AC 3. Sennheiser does make an 8-channel combiner, the AC 3200-II, but it is a lot of money. In theory you can passively combine the output of two 4-channel combiners, but you'll suffer ~4dB of loss for doing so (i.e. more than half your transmit power).

I'm still not sure if you're talking about wireless microphones or IEMs...

-Russ
Title: Re: Is this real?
Post by: Tim Halligan on February 03, 2019, 07:26:17 pm
Looks like Chinese counterfeit crap.

Sure does.

Avoid.


Cheers,
Tim
Title: Re: Is this real?
Post by: Mac Kerr on February 03, 2019, 07:50:42 pm
I'm still not sure if you're talking about wireless microphones or IEMs...

THIS^^^^^
Title: Re: Is this real?
Post by: Erik Jerde on February 04, 2019, 12:35:43 am
I think we might have a terminology issue here. A "combiner" is something that takes several RF signals and combines them into a single signal path. A splitter (or distro) is something that takes a single RF signal path and splits it into several identical copies. Combiners are used with IEM transmitters, taking several separate IEM signals and combining them into a single transmission line. Splitters are used with wireless microphone receivers, taking a single (typically pair of) antenna feeds and splitting them out to multiple receivers.

The ASA 1 is an 4-way antenna splitter, splitting one pair of antenna feeds to four separate wireless microphone receivers. A pair of ASA 1s can be cascaded into each other to create an 8-way splitter, which is the typical setup for 8-channel Sennheiser racks.

For IEMs, the Sennheiser 4-channel combiner is the AC 3. Sennheiser does make an 8-channel combiner, the AC 3200-II, but it is a lot of money. In theory you can passively combine the output of two 4-channel combiners, but you'll suffer ~4dB of loss for doing so (i.e. more than half your transmit power).

I'm still not sure if you're talking about wireless microphones or IEMs...

-Russ

Iíve combined to AC3 through a shure passive combiner and had zero problems.  Shure even used to have a paper on this but I canít find it anymore.
Title: Re: Is this real?
Post by: Lyle Williams on February 04, 2019, 03:25:58 am
Sure does.

Avoid.


Cheers,
Tim

If you are looking for a place to go cheap, far better to go cheap here than on the mics.
Title: Re: Is this real?
Post by: Scott Helmke on February 04, 2019, 11:35:41 am
An amplified splitter is likely to be the second least sophisticated piece of electronic equipment you will own (after a transformer-based wall-wart)

The old Sennheiser ASA (2-space unit sold maybe 15-20 years ago?) was basically a rack enclosure with off-the-shelf TV amp and splitters inside.
Title: Re: Is this real?
Post by: Dave Garoutte on February 04, 2019, 12:37:12 pm
I think we might have a terminology issue here. A "combiner" is something that takes several RF signals and combines them into a single signal path. A splitter (or distro) is something that takes a single RF signal path and splits it into several identical copies. Combiners are used with IEM transmitters, taking several separate IEM signals and combining them into a single transmission line. Splitters are used with wireless microphone receivers, taking a single (typically pair of) antenna feeds and splitting them out to multiple receivers.

The ASA 1 is an 4-way antenna splitter, splitting one pair of antenna feeds to four separate wireless microphone receivers. A pair of ASA 1s can be cascaded into each other to create an 8-way splitter, which is the typical setup for 8-channel Sennheiser racks.

For IEMs, the Sennheiser 4-channel combiner is the AC 3. Sennheiser does make an 8-channel combiner, the AC 3200-II, but it is a lot of money. In theory you can passively combine the output of two 4-channel combiners, but you'll suffer ~4dB of loss for doing so (i.e. more than half your transmit power).

I'm still not sure if you're talking about wireless microphones or IEMs...

-Russ

Well, D'oh! again.
I was visualizing the wrong direction.
Splitter it is.
I had also forgotten about daisy chaining two ASA1s together.
I saw it when I assembled the racks, but promptly forgot about it as it wasn't necessary for me at the time.

Thanks Russ!
Title: Re: Is this real?
Post by: Henry Cohen on February 04, 2019, 09:17:13 pm
If you are looking for a place to go cheap, far better to go cheap here than on the mics.

I doubt the talent that has to listen to the IEMs would agree . . .
Title: Re: Is this real?
Post by: Jason Glass on February 05, 2019, 01:36:56 am
The old Sennheiser ASA (2-space unit sold maybe 15-20 years ago?) was basically a rack enclosure with off-the-shelf TV amp and splitters inside.
Please cite your sources on this before I vigorously refute your statement.  I don't want to unnecessarily raise an argument.

It was a POS by today's standards but those Germans sure as hell designed it for its purpose, as a through and through 50 Ohm system.

Sent from my mobile phone using Tapatalk
Title: Re: Is this real?
Post by: Scott Helmke on February 05, 2019, 11:04:05 am
Please cite your sources on this before I vigorously refute your statement.  I don't want to unnecessarily raise an argument.

It was a POS by today's standards but those Germans sure as hell designed it for its purpose, as a through and through 50 Ohm system.

My source was  that I opened the box to fix something, and found it full of off-the-shelf components. Likely they were high quality components, but they were in fact little boxes cabled together with coax inside the Sennheiser box.
Title: Re: Is this real?
Post by: Jason Glass on February 05, 2019, 11:07:01 am
My source was  that I opened the box to fix something, and found it full of off-the-shelf components. Likely they were high quality components, but they were in fact little boxes cabled together with coax inside the Sennheiser box.
Roger that.  Can't fault a personal inspection!

Sent from my mobile phone using Tapatalk

Title: Re: Is this real?
Post by: Scott Helmke on February 05, 2019, 12:56:36 pm
Roger that.  Can't fault a personal inspection!

It's not like distributing wideband antenna signals is anything new.  The cable TV industry has been doing it for half a century already.
Title: Re: Is this real?
Post by: Russell Ault on February 05, 2019, 03:14:21 pm
It's not like distributing wideband antenna signals is anything new.  The cable TV industry has been doing it for half a century already.

My impression too was that the VSWR-related attenuation caused by a 50 ohm to 75 ohm impedance mismatch (and back) is pretty nominal, at least in receive applications (not to mention that even good professional wideband antennas usually exhibit characteristic impedances somewhere between 50 and 75 ohms in their passband, so there's going to be some mismatch anyway).

-Russ
Title: Re: Is this real?
Post by: Don Boomer on February 05, 2019, 04:14:19 pm
My impression too was that the VSWR-related attenuation caused by a 50 ohm to 75 ohm impedance mismatch (and back) is pretty nominal, at least in receive applications (not to mention that even good professional wideband antennas usually exhibit characteristic impedances somewhere between 50 and 75 ohms in their passband, so there's going to be some mismatch anyway).

-Russ

True enough if all you are considering is signal levels. But Iím thinking that varing impedances may cause havok with any passive front end filtering that commonly occurs before the first active stage.
Title: Re: Is this real?
Post by: Russell Ault on February 05, 2019, 04:37:01 pm
True enough if all you are considering is signal levels. But Iím thinking that varing impedances may cause havok with any passive front end filtering that commonly occurs before the first active stage.

Right, makes sense, but wouldn't real-world antenna impedance variation cause similar problems?

-Russ
Title: Re: Is this real?
Post by: Henry Cohen on February 05, 2019, 09:28:44 pm
True enough if all you are considering is signal levels. But Iím thinking that varing impedances may cause havok with any passive front end filtering that commonly occurs before the first active stage.

Not unless you're a SETI listening post, listening for signs of the Big Bang or otherwise need to discern tenths or even hundredths of a dB. The 75Ω/50Ω mismatch results in barely a .75dB loss, about the same as for an inline adapter, or a somewhat tight bend in a coax, all less than the mismatch between the receiver front end and a wideband antenna. With a filter, I'd be more concerned with the reflections from the filter's stopband(s).
Title: Re: Is this real?
Post by: Don Boomer on February 06, 2019, 02:35:06 am
Yes, I do realize that the change in a real world antenna and coax does vary with frequency. But you are simply stuck there. 

Seems to me that even a simple first order filter would shift itís corner frequency by half an octave moving from 50 ohms to 75 ohms. 
Title: Re: Is this real?
Post by: Lyle Williams on February 06, 2019, 03:09:54 pm
If you filter at any point without a rock solid impedance it is wise to add a small attenuator to tie down the impedance.

If you have $15,000 worth of receivers in a rack should you buy this splitter?  Hell no.

But a cheap-ass splitter is less scary than a cheap-ass mic.
Title: Re: Is this real?
Post by: Brandon Scopel on February 11, 2019, 01:02:09 pm
If you filter at any point without a rock solid impedance it is wise to add a small attenuator to tie down the impedance.

If you have $15,000 worth of receivers in a rack should you buy this splitter?  Hell no.

But a cheap-ass splitter is less scary than a cheap-ass mic.

I've seen Professional Wireless in a lot of large scale RF deployments.....

http://www.professionalwireless.com/product/rx-antenna-combiner-distros/