Martin Logan Monolith III bass fix?

[georgehifi]

Has anyone measured the Monolith III (system bass resonance) in hz/ohms, as the bass could be greatly improved if it had an L/C/R network across the back of the bass driver, it would stop the xover ringing and give a bass that`s equal to the speed and dynamics of the mid/highs.

Cheers George

[georgehifi]

It`s done a friend helped me measure the resonant peak, which was about 4-5db at 40hz. The LCR network to get this flat is 18mh in series with 900uf in series with 5.6ohm across the bass speaker, in the Monolith`s case it`s easy to fit outside as the xover is outside the box.
These values for the LCR are for my speakers which are 100% stuffed this may vary from the standard which is only 30% stuffed.
Anyhow the bass is now tight smooth and dynamic, much different to the standard one note bass the the Monoliths had.
One day i may do the standard measurements, but i like the detailed tight sound of an overdamped, low Q bass, it suits my not so large listening room.

Cheers george

[sreten]

Theorectically with a standard voltage output power
amplifier the network will have no audible effect.

sreten.

[georgehifi]

Sorry you could`nt be more wrong, the amp being used on the bass is the 250 watt Threshhold S500mk2 which can double it`s wattage into 4ohm and then again into 2ohm.
The thing that made me do this is, the difference taking the network out in a pair of B&W 801 Matrix II`s, it sounded just like the Monolith`s standard put it back and all`s tight again. And in the case of the B&W`s the values are 20mh/800uf/10ohm.
These networks really work and you`ll find them on the bass of only the best speakers, as the price of such a network is very expensive because of the very high values.
Cheers George

[Tube_Dude]

Originally posted by sreten
Theorectically with a standard voltage output power
amplifier the network will have no audible effect.

sreten.

Here it will have a audible efect...because if the network as george tell us is connected to back of the bass driver...they see a series impedance of the low pass filter of the woofer...is not voltage drive anymore!!

If that was not possible ,nobody will put zobel ,in crossovers networks ,anymore...

[georgehifi]

Yeah sorry i have`nt replied earlier, been on a surf trip, to Sreten the network equalizes out the motional impedance of the driver, effecting the crossover, just trust me you will not go back after it`s inserted, and it`s the same for the standard amount of stuffing as well, i`ve just tested it.
Cherrs George

[sreten]

Originally posted by Tube_Dude


Here it will have a audible efect...because if the network as george tell us is connected to back of the bass driver...they see a series impedance of the low pass filter of the woofer...is not voltage drive anymore!!

If that was not possible ,nobody will put zobel ,in crossovers networks ,anymore...

Hi TD & GH,

You are correct it will have some theorectical effect if the bass
units crossover has some series resistance / impedance at
low frequencies.

I didn't take note of the crossover also being outside the box.

Glad it works !

sreten.

[ted betley]

The bass tightens up significantly but sounds fuller and more robust at the same time. It allows one to follow more inner details in the critical octaves handled by the ML III woofer. There is more air around bass viols, celli, bassoons, bass guitars, lower voice registers. It is flat out better IMO. It pushes the soundstage back further while adding body to the instruments and voices within that soundstage and oh BTW it becomes more dynamic in the mid bass.

I'd say it was a bargain for the price.

[georgehifi]

I`m glad someones finally tried this mod. I was starting to think that i was the only one who noticed that the Monolith`s bass had some issues that needed a cheap quick fix, Ted you`ve expressed yourself correctly as far as the mod, i`m glad it work out well for you as it did for me.
Of the 2500 odd monolith pairs out there in the world you would think others would be dying to fix the slow ill-defined bass they have.
Maybe now that you`ve started the ball rolling with my mod others may get the courage to do it, not that it`s hard to do.

BTW the mod values remain the same even for the standard amount of stuffing that comes form the factory. And the +5db peak is at 80hz not 40hz as i first posted (misprint).


Cheers George

[Kittle]

okay.. n00b question here:
what does this L/C/R network do that makes the low end sound so good?
and how does one determine if you need one.. and calculate the values & circuit layouts?

Thanks!