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markosolo 6th June 2012 11:46 AM

Martin Logan Sequel ii upgrade
Hi everyone,

my names Mark and I live in Switzerland. I have a pair of ML Sequel iis stading here which I purchased almost a year ago. Im quite happy with them, except the lows dont quite satisfy me. They seem a bit weak and sharp, I think they should be voluminous, room filling, powerful and smooth. I was hoping someone could help me figure out a way to improve this without purchasing a subwoofer. My thoughts so far were to replace the bass drivers, to build in a second driver driver beneath the existing one, to replace the existing crossover with an active one, to modify the bass chamber to a bass reflex system...
But I would really need help with this, my knowledge in electronics is very limited.
best regards from Switzerland

Calvin 6th June 2012 02:44 PM


afaik ML introduced the Sequel2 with a closed cabinet as a ´european version´ as the bassreflexed MK1 put out too much bass of low contour.
In any way, the integration of bass and panel was quite bad, electronically as well as acoustically. If You intend to put quite some effort into tweaking Your Sequel, You might consider to think about a completely different bass system alltogether. A bassreflexed box might add the desired slam but will hardly be an adequate partner for the panel. It will very probabely sound desintegrated, without harmony and the BR-typical tendency to a boomy unprecise bass.
My suggestion would be a basstower of 4-6 stacked smaller bass drivers in a CB, positioned in close proximity to one side of the panel or, as top-notch solution, a dipolar basstower in the same position, but bandwidth limited to ~50Hz and a dedicated small subwoofer.
A ESL profits from good active crossovers alot, especially when built from metal sheet stators as the Sequels, since these panels require extensive external equalization measures. Built in passive technology this EQ costs on efficiency (~10dB with the Sequel) and sonic quality.
With restricted electronic knowledge a digital crossover filter like the MiniDSP or similar could be a very good start, also since these digitall filters are easy to set up and handle and are very flexible and will give more pleasing results than standard analog filters which are rather useless for ESLs.
A ´ESL-specialized´ analog active filter means an effort well above the capabilities of an unexperienced builder, even if it could be the sonically most pleasing solution.


Bazukaz 7th June 2012 12:38 PM


Changing driver or modifications to crossover will not be easy to implement properly, especially for ESL hybrid.
If the only problem for you is lack of bass then adding bass reflex tubes could be considered but only if you know parameters of bass drivers. Stuffing inside the box(if exists) should not be removed in that case.
You could try to get a very rough approximation of bass reflex effect by applying eq. to low level bass. You could experiment with a slight boost(~4db) to around 30-35 hz.
Keep in mind, room also plays a very big role and sometimes different placement can influence bass by 10 db or so.


markosolo 9th June 2012 06:51 AM

Thank for your replies,

how would I connect an active crossover if I had one ? Should I use the biwiring feature ? I cannot really afford financially nor in matters of space to get a big woofer and from what I understand, bass reflex or other similar mod would also influence the lows quality.
About my room, its about 5mx5m and right behind me is wall which i suspect reflects a lot of sound. Theyre selling foam blocks specially designed for sound absobation, would that make an audible difference ? I mean if there really can be up to 10db of difference, that seems like a cheap solution..

ticknpop 9th June 2012 08:42 AM

You likely can't bypass the internal passive crossover becuase the crossover for most martin logans has a notch filter to cancel floor reflection, even the CLX has the notch filter. You can duplicate the slopes of the cross over - usually 6 or 12 db on the woofer and 12 or 18 db/octave on the cells , but you can't duplicate the notch filter unless you do it digitally.

Panos AC 9th June 2012 10:12 AM

Some info about the Sequel II
Hi Mark

i have a pair of Sequel II in my "test" system that i use for evaluation of various gear. They have a lot of bass that is room-filling and warm. Especially with electronic music! I have some drum and bass music tracks that even in low listening volumes can make lots of things in my whole apartment rumble. So i am thinking that its not that the sequels lack bass, its that the bass is "lost" somehow.
You dont give details about your amp, room etc so i just have to say that if the amp cannot drive them, you are not going to have bass, so better check that too.
But i think the most probable cause is the speakers.
When i bought the sequels few years ago i opened their crossovers for a quick service and to check if there is something wrong. As far as i remember there are a lot of contacts in there that might got oxidized, so you have to clean them all. Also you have to bear in mind that they are more than 10 years old now so some crossover capacitors might be just old or damaged from big power amps ( if i remember well mine got a couple of caps - in the bass section - in bad condition)
Thats all i remember about them, but check inside the martin logan site, there is a forum with model specific areas that has a lot of information that will help you.


markosolo 23rd June 2012 11:07 AM


Im driving my sequels on a denon pma 816 and I just replaced the big caps inside. Im not shure whether or not there is an audible difference though...
If Im not mistaken, mine are from 1989. About the room, it is about 5*5m, and behind the listener there is a bed on the same height as the sub drivers.
The things I suspect might be causing my lack of depths are:
1) the hard wall behind the bed possibly causing standing waves
2) the "weak" amp: I have to turn it half way up for a decent acoustic level
3) old electronics inside the speakers (except for the replaced caps of course)
Has anyone had experience with tube amps on Martin Logans ? Im not shure if tubes are strong enough for them.

peregrin288 24th June 2012 12:02 AM

Hi markosolo,

Have you tried the forum at MartinLogan Owners (MLO) Somebody over there may have additional suggestions. There is a frequent poster by the name of Jonfo that uses Sequel IIs as surround speakers in his setup with an active crossover, so he bypassed the internal passive crossover. He also built a custom center channel using just the ESL panel from a donor Sequel II. I know there are instructions on that forum somewhere for removing the internal crossover as well.

Frommerstop 9th July 2012 12:26 AM

I had a pair of Sequel 2s years ago, and I can't say I ever had issues with not enough bass output. My suspicion would be your amp. I used a Krell KST100 full range with good results, and I later biamped with a CJ MV52 to drive the panels. I wouldn't expect to be able to control the bass on them with a tube amp run full range unless it was something really powerful - perhaps a Carver Silver 7, or a hybrid from ARC. When I first got them, I used an Adcom GFA555 II, and it worked pretty well, though the Krell was a noticeable improvement. My point is, IME the Sequels really like power, so before messing with the woofers, I'd upgrade your amp.

liching1952 8th August 2012 10:09 PM

how is it now? I am in Switserland too, will you sell your Sequilas? Tell me if it is, my mail is


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