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[Bryce Holland]

OK, this will take a little to explain. I have setup several wireless microphone systems, so I am not new to this. However there are always unique challenges when setting up a system for a non-profit school. This is definitely the case that I need to use what they have.

I will explain, but be as brief as possible.

• This school was donated 10 Sennheiser EW100-G2 wireless systems with the ASP-2 splitters, in the A band.
• This school already had 8 Audio Technica ATW-R3100a systems with two ATW-DA49 splitters, also in the A band.
• Because I only have 10 Sennheiser systems, but four splitters, I have a couple outputs left over.

So the question is:
Would it be acceptable if I use those outputs from the Sennheiser ASP-2 for the inputs of the ATW-DA49 splitters? That would allow me to have all of these receivers on one set of Sennheiser Antenna paddles, which would really help, especially for these old Audio Technica systems. The default small antennas always struggled to pick up well in their cafetorium.

What do you think? I don't want to cause a feud between Sennheiser and Audio Technica, I just need some input on if this is safely feasible. If not, then I will continue to use the antennas that these Audio Technica systems came with.

[Henry Cohen]

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[Russell Ault]

{...}

• This school already had 8 Audio Technica ATW-R3100a systems with two ATW-DA49 splitters, also in the A band.

{...}

Okay, I've searched high and low, and for the life of me I cannot seem to find any reference to an "A" band for Gen2 A-T 3000-series equipment. What is the frequency range for this band?

-Russ

[Henry Cohen]

OK, this will take a little to explain. I have setup several wireless microphone systems, so I am not new to this. However there are always unique challenges when setting up a system for a non-profit school. This is definitely the case that I need to use what they have.

I will explain, but be as brief as possible.

• This school was donated 10 Sennheiser EW100-G2 wireless systems with the ASP-2 splitters, in the A band.
• This school already had 8 Audio Technica ATW-R3100a systems with two ATW-DA49 splitters, also in the A band.
• Because I only have 10 Sennheiser systems, but four splitters, I have a couple outputs left over.

So the question is:
Would it be acceptable if I use those outputs from the Sennheiser ASP-2 for the inputs of the ATW-DA49 splitters? That would allow me to have all of these receivers on one set of Sennheiser Antenna paddles, which would really help, especially for these old Audio Technica systems. The default small antennas always struggled to pick up well in their cafetorium.

What do you think? I don't want to cause a feud between Sennheiser and Audio Technica, I just need some input on if this is safely feasible. If not, then I will continue to use the antennas that these Audio Technica systems came with.

There'll be no feud between manufacturers as it regards antennas, multcouplers ("splitters") and the receivers: RF is agnostic.

The issue here is the operational bandwidths of the splitters. The ASP-2 is 500-800 MHz, and the ATW-DA49 is 440-900 MHz, so they can be cascaded in that respect. The bigger concern is noise figure, for which neither model has a great spec, but should work as long as you don't cascade more than two active splitters deep. Use a passive 2-way splitter as the main feed (inputs connect to antennas) with each output feeding one of the ASP-2's, then each ASP output will feed either one ATW-DA49 or a receiver.

[Russell Ault]

{...} The issue here is the operational bandwidths of the splitters. The ASP-2 is 500-800 MHz, and the ATW-DA49 is 440-900 MHz, so they can be cascaded in that respect. {...}

The ASP 2 itself is wideband, but it's also totally passive. To overcome the 7+ dB of splitter loss, Sennheiser recommended (and every installation I've ever seen did this) that a pair of AB 2 line amplifiers be used just upstream of the ASP 2, and to the best of my knowledge all AB 2s are significantly band-limited. I was ASSuming that the OP's setup included a pair of A-band AB 2-As, which are limited to 518-554 MHz.

-Russ

[Henry Cohen]

The ASP 2 itself is wideband, but it's also totally passive. To overcome the 7+ dB of splitter loss, Sennheiser recommended (and every installation I've ever seen did this) that a pair of AB 2 line amplifiers be used just upstream of the ASP 2, and to the best of my knowledge all AB 2s are significantly band-limited. I was ASSuming that the OP's setup included a pair of A-band AB 2-As, which are limited to 518-554 MHz.

Da**. Missed that part about the ASP being passive. And ">10dB" gain is too much to put anywhere but at the antenna (or better still, the 'misc, never to be used drawer', but that's a different topic). With that, your initial question about what is the AT "A" band holds.

[Russell Ault]

Da**. Missed that part about the ASP being passive. And ">10dB" gain is too much to put anywhere but at the antenna (or better still, the 'misc, never to be used drawer', but that's a different topic). With that, your initial question about what is the AT "A" band holds.

The ASP 2 was probably a tier (or two) below your market when it was released, let alone today.

I'm pretty sure that the "P" in "ASP" stands for "passiv" (you can guess the English translation), especially as compared to the ASP 2's G3 replacement, the ASA 1.

In fairness to the design, half the outputs on the ASP 2 are behind an extra 2:1 splitter (to create a "cascade" output), so a 10 dB amplifier would be pretty close to unity gain for those outputs at least. Plus, the passive design means that you can use whatever line amplifier you like with them (although I don't think I've ever seen an AB 2 fail; heck, part of the reason I'm as "up" on them as I am is because I still see a bunch of them in use!).

-Russ

[Paul Johnson]

remember that signal strength is rarely the real problem in radio systems - the problem that hurts is dropout - and avoiding it. Look at the meters on almost any receiver. They stay pinned to near max, then your transmitter to receiver path gets compromised and off it goes. So any distribution system with antennas up in the clear - and most critically spaced antennas, will give you plenty of signal, and a passive split with it's insertion loss will be much better than you think. A ten minute test will prove the viability. Cascading two passive splitters with well paced, decent antennas in the right place is better than an expensive amplified splitter with the supplied 1/4 waves in the back of it. Avoiding those nulls is the key to RF performance. Giving diversity receivers two very different antenna placement signals is the real key to noise free signal. Insert a 10dB attenuator and watch the max signal only reduce a tiny bit - vs a signal that is very weak at best dying when the 10dB reduction is introduced.

Remember that commercial (non-entertainment) critical performance RF systems often specify passive splitters for reliability and resistance to the over level and intermod products stacking pre-amps sometimes causes. Plug the system up and do some practical tests that are specific to your system and site.

[Russell Ault]

{...} Look at the meters on almost any receiver. They stay pinned to near max, then your transmitter to receiver path gets compromised and off it goes. {...}

I've always gotten the sense that different brands have slightly different takes on this. For example, the RF meters on Sennheiser RXs always seemed to me to be much more "lively" than the ones on Shure RXs (many of which barely have meters at all).

{...} Giving diversity receivers two very different antenna placement signals is the real key to noise free signal. {...}

...unless your RXs use some kind of "intelligent" switching diversity system (ULX-D, QLX-D, SLX-D, and—now that the patents have expired—EW-D), in which case "very different antenna placement" can actually increase the likelihood of drop-outs.

{...} Insert a 10dB attenuator and watch the max signal only reduce a tiny bit - vs a signal that is very weak at best dying when the 10dB reduction is introduced. {...}

That's true of basically all FM receivers, though: if you're constantly driving the front-end into limiting (A.K.A. the Shure approach), a 10dB reduction likely won't show up on the meters at all. With Sennheiser RXs (assuming passive paddles and no extraneous amplification, which in my experience is pretty typical), a 10 dB drop should be fairly evident on the meters (for the OP's reference it'd be two bars on the EM 100 G2).

{...} Remember that commercial (non-entertainment) critical performance RF systems often specify passive splitters for reliability and resistance to the over level and intermod products stacking pre-amps sometimes causes. {...}

It dawned on me after my last post, but this is actually one of the advantages of the older ASP 2 + AB 2 vs. the Sennheiser's later prosumer distro offerings. With a pair of cascaded ASA 1s (or ASA 214s), half the outputs of the distro system will have gone through two separate amplifier stages (and wide-band ones at that), whereas the older approach doesn't suffer from this issue.

{...} Plug the system up and do some practical tests that are specific to your system and site.

That's definitely good advice if time and space allow; however, I think there's also something to be said for at least starting with the manufacturer's recommendations, particularly in the case of designed-to-work-together systems (i.e. if Sennheiser says that their RXs are designed with unity-gain antenna distro in mind, I'm inclined to believe them).

-Russ

[Paul Johnson]

I think the manufacturer advice is always a sensible approach till you know what you can do, and maybe do better.

Regarding the different spacings - the critical factor is really path loss with the usual physical obstructions - so one firing across the mic line is a good sensible choice if the antenna can be got up high so the nearest people don't block the furthest, but then another that crosses that line is always a good choice - after all, what every diversity system is looking for are the times you get two string signals, with just one string one at a push, rather than two nearly the same weak ones. It's also possible for de-sense to occur when one person is very close to an antenna producing too much signal that might weaken the channels adjacent, and Murphy's law says that the adjacent channel is always the weakest one.I've got a couple of Sennheiser racks and the one with the Sennheiser DAs performs, from the practical point of view, just as well as the one with cascaded passives. I'm running a theatre rack at the moment with Sennheiser antenna distribution but retro fitted with Shure receivers and UR1M packs. Touch wood - a dropout free system, but every receiver show nearly full signal strength.

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