Increasing HF attenuation on S3100 MKII network

[Ian Mackenzie]

Hello Ian

Hey heads up. Looking at the 3100 Mk 2 it uses the 8 ohm version. Apparently there are an H and J versions.

DCR is 3.2 ohms

Rob

Will probably attenuate less then.

If the impedance of the driver is 8’ohms it will look a 9.4 ohm load. Then adjust the series resister to 4.8 ohms.

At any rate l am aware he is trying to bi amp the S3100mk2 .

I think the problem he’s got is noise from the horn trying to bi amp.
I will give him a call to ascertain where he’s at.

Hi Earl,

That’s a very interesting observation with your sim!

I heard these S3100mk2 recently and l thought they were very good overall.

They are really tight and dynamic. But they need subs which are being deployed.

[Robh3606]

Hello Ian

He's trying to bi-amp? Ok then why doesn't he try passive bi-amp first? Not ideal but there is no noise issue and he can set the HF level quite easily.

Rob

[Robh3606]

dumb thought... Treble knob?

LOL! You mean from when you had preamps with tone controls with selectable shelving, MM/MC phono stages, Cartridge loading., a stereo/mono switch and so on as SOP?

Most preamps this day leave a lot to be desired.

No not a dumb thought!

Rob

[Ian Mackenzie]

That’s a good idea!

[Ian Mackenzie]

It’s intriguing we we don’t have the whole story on these questions…Lol.

My impression is these S3100mk2 are only bi wire , not bi amp after looking at the schematic and the rear panel then the owners manual . That’s the horn attenuation on the terminal panel.

I think our time is better spent having a beer. Too early here…Lol

[Ian Mackenzie]

What we need is a freakin big chart with a column that says Bi Wire Yes/No Bi Amp Yes/ No rather than be deliberating over this sort of thing.if unsure fill out this form…blah blah.
We will contact on return from the beer festival

Of course it’s interesting looking into it and all the possibilities…

[Ian Mackenzie]

I simmed the basics of that 3100 Mk11 network ( I left out the 3 notch-filters ) .

The values for R3a + R3b resistors ( 24R & 62R ) do ( actually ) make sense since they end up being paralleled with the ( always in circuit 12R ) R3_ resistor.

It's a padding trick used within a few other higher-end networks from JBL .

The way the resistors add together allows the horns output in the 750hz ( crossover ) area to be virtually untouched ( since what gets attenuated is mostly over 1K ).

FWIW, placing an Lpad right by the driver will certainly attenuate any desired amount >> the problem is, it'll also attenuate the crossover region which wasn't part of the original network design ( from what I see ).

OTOH, increasing R3_ from 12R to 15R ( while holding everything else the same ) will give another 1.2db of mid-band horn attenuation ( while still keeping the crossover region mostly untouched ).

I have to believe the initial desire for 3 to 6 db more attenuation is a bit over-stated.

Hi Earl,

I spoke with Kelossus this morning.

He has a question around the simplest and easiest way to reduce the horn level overall?
See the reason for this below.

Given you have looked at a sim l thought best to ask you.

Kelossus would like to know if a single 5.1R resister in series with the horn bi wire input terminal to bring down the horn level overall is the best approach or should it be a voltage divider?

Can you kindly have a look at your sim to see what a series 5.1R resistor is doing to the voltage drive? Will a fixed L pad of the same level of attenuation as the series 5.1R work better? He appreciates this is not ideal but wants to avoid more invasive modifications.

Cheers

Ian

Back story
The situation is Kelossus has been running the S3100mk2 with dual subs up till now and they sounded balanced. He is not bi wiring or bi amp yet. He previously has been listening to the 43XX which have a much bigger bottom end than the S3100mk2.

I’ve found a response graph in the owner manual which supports his concerns.

But now he wants to just run them stand alone. What Kelosus want to achieve is more of a 43XX fullness to the overall balance. He said the horns are overpowering in his room. He doesn’t have tone controls.

So what he has done is add a 5.1R resistor in series with the input of the bi wire horn input to drop the horn level overall. He has also tried 2.7R and he said he is happy with the effect of the 5.1R resistor.

[Earl K]

Hi Ian,

A voltage divider is necessary to maintain the desired curve ( since that single 5R series resistor triggers a HF droop//fall-off while the Lpad mostly resists the HF droop )

A 10R resistor across the HF "BiWire//BiAmp" terminals with a 4R series resistor off of the plus terminal of the HF inputs will offer something like 4db of extra attenuation ( when compared to the stock 0.0db setting ).

FYI, an LPad in the front position before the HiPass circuitry ends up offering the HF amplifier a constant 14ohm load ( from say 5hz up to @ 300hz then very slowing decreasing to just under 8 ohms up around 20K ).
- a pretty safe load for most amps.
- With loud listening those added LPad resistors will get very hot.



PS; Here are some visual aids.
- Read the bottom Legend for clues as to "what curves are what".

[Ian Mackenzie]

Hi Ian,

A voltage divider is necessary to maintain the desired curve ( since that single 5R series resistor triggers a HF droop//fall-off while the Lpad mostly resists the HF droop )

A 10R resistor across the HF "BiWire//BiAmp" terminals with a 4R series resistor off of the plus terminal of the HF inputs will offer something like 4db of extra attenuation ( when compared to the stock 0.0db setting ).

FYI, an LPad in the front position before the HiPass circuitry ends up offering the HF amplifier a constant 14ohm load ( from say 5hz up to @ 300hz then very slowing decreasing to just under 8 ohms up around 20K ).
- a pretty safe load for most amps.
- With loud listening those added LPad resistors will get very hot.



PS; Here are some visual aids.
- Read the bottom Legend for clues as to what curves are what.

Hi Earl,

Thank you for looking into this enquiry.

I will let Kelossus know.

Cheers


Ian

[kelossus]

Thanks for the help guys. It sounds like an l-pad is the way to go rather than modifying the crossover values to achieve the attenuation. Gotta say I'm a massive fan of the h2600 horn on this speaker.

[Ian Mackenzie]

How about posting a pic of them

[toddalin]

If you put a resistor BEFORE the first element of a 2nd+ order crossover, you reduce the volume but you don't change the slope. I actually demonstrated this on the other forum.

That said, you could try to put a resistor BEFORE the Red terminal that goes to the horn section of the crossover. A resistor in this position goes a long way so you would use a low value (couple ohms or less) that could carry the wattage.

https://audiokarma.org/forums/index....etwork.926881/

[kelossus]

If you put a resistor BEFORE the first element of a 2nd+ order crossover, you reduce the volume but you don't change the slope. I actually demonstrated this on the other forum. That said, you could try to put a resistor BEFORE the Red terminal that goes to the horn section of the crossover. A resistor in this position goes a long way so you would use a low value (couple ohms or less) that could carry the wattage. https://audiokarma.org/forums/index....etwork.926881/

This is how I am running them now. With 5.1 ohm 10 watt resistor in series with the red terminal of the HF section. I've given the speakers a good flogging and the resistor doesn't seem to get hot.

[Ian Mackenzie]

Hi Earl and Todd,

For the benefit of others it would be cool if you can collaborate together on illustrating the effects of these sort of network modifications with some simulations (voltage drives) and practical implementation with FR measurements.

In this situation Kelossus had a particular need to modify the tonal balance of the S3100mk2 for his preference in line with the 43XX series. The modification outlined here is not a cure but is an easy diy tweak until the owner decides on something more sophisticated such as a line level response tile with bass boost and treble cut or other EQ.

In other circumstances a fix L pad to replace a variable Lpad might be desired. But how does the owner go about this?

I am sure others would find this interesting.

[Earl K]

Hi Ian,

Here are the two different padding scenarios illustrated by XSim ( using real measurements and impedance files ).

First up is the single resistor located at the HF input terminal.



Next pic shows attenuated curves using full LPads located before the HF crossover section.



Either approach to padding ( at that location ) has its merits ( & drawbacks ).
- Ultimately, the ears need to decide.

To be clear, I have no dog in this race.

In fact, I would simply EQ the Low-end and call it a day ( as has already been suggested ).