Summit: Technical Problem - need advise

[bluenote56]

Hello,

since a couple of years, i've owned a pair of Summits (not X). Right from the beginning, I was not really happy with bass performance. Although the Summits are known for excellent and deep Bass, there is only very weak bass in my setup. I've heard Summits several times at other places, and compared with mine, lower frequencies were excellent, almost too much.

As I was used to weak bass with my CLS too, I thought, this might be caused by my room, which is not optimal for sure.

But now: accidentally I may have set the 25Hz Knob to -10 dB at one Speaker - and there it was. Enourmous and heavy Sub-Bass ! So, I did several Tests with Test Signals and it turned out, that every time I increase volume of one Woofer, bass disappears.

It seems to me, as if one of the woofers is not in phase. Is there anything I could inspect by myself? Maybe just the internal wiring is reversed. Are the inside connections accessible somehow?

Many thx for your Input,
Johann

[Rich]

Hello,

since a couple of years, i've owned a pair of Summits (not X). Right from the beginning, I was not really happy with bass performance. Although the Summits are known for excellent and deep Bass, there is only very weak bass in my setup. I've heard Summits several times at other places, and compared with mine, lower frequencies were excellent, almost too much.

As I was used to weak bass with my CLS too, I thought, this might be caused by my room, which is not optimal for sure.

But now: accidentally I may have set the 25Hz Knob to -10 dB at one Speaker - and there it was. Enourmous and heavy Sub-Bass ! So, I did several Tests with Test Signals and it turned out, that every time I increase volume of one Woofer, bass disappears.

It seems to me, as if one of the woofers is not in phase. Is there anything I could inspect by myself? Maybe just the internal wiring is reversed. Are the inside connections accessible somehow?

Many thx for your Input,
Johann

Your woofers may very well be miswired to be out of phase. If you bought them new and they are still under warranty, I would call your dealer to check them out. Or call ML directly and ask them about how you can troubleshoot the problem . . . that is, assuming someone still works in the customer service department with any experience.

[bluenote56]

I would call your dealer to check them out. Or call ML directly and ask them about how you can troubleshoot the problem

That's exactly what I did. But my dealer is on holidays till end of month. So, waiting for response from ML now. Maybe one of the members here already had some inside look into a Summit?

[Rich]

Do some research on the previous forum posts. There was a thread recently about a Summit that was received with the woofers wired out of phase, and I believe the thread contains a description of how to fix it. Did you email ML's customer service? That is probably the fastest way to get a response from them.

[Hocky]

The woofer connections are easily accessible by opening the back panel for the front woofer and removing the bottom woofer.

[GDSA]

You may be able to check sub phasing on both speakers is the same by (briefly) touching and removing a 1.5 v torch cell accross the sub terminals and watching whether the cones both jump forward with the same battery orientation?

[bzr]

great tip!

[bluenote56]

You may be able to check sub phasing on both speakers is the same by (briefly) touching and removing a 1.5 v torch cell accross the sub terminals and watching whether the cones both jump forward with the same battery orientation?

Are you sure, this will work with the summits? The woofers are driven by their own internal ICE Power Amps. So right after the terminals there will be a voltage divider. Further, I fear, that feeding the ICE Amps with DC may blow them away.

Meanwhile, I have a very helpful email-conversation with ML Customer Service. There are several things I may check by myself.

Keep you posted,
Johann

[roberto]

Hola What GDSA is saying is, take the woofers out, disconnect them from their terminals, and with the aid of a 1.5 V battery, check that both woofers move in the same direction of the battery polarity. Once, I had one woofer with polarity reversed some time ago. When you apply the + of the battery to the red or + marked at the woofer, and the - of the battery to the - or black of the cone, the cone should come out. Both woofers should do this. It is just a start to track your speaker's problem. If this is not your case, proceed with the instructions from ML service dept. They will guide you easy. Happy listening!

[bluenote56]

Hola What GDSA is saying is, take the woofers out, disconnect them from their terminals, and with the aid of a 1.5 V battery, check that both woofers move in the same direction of the battery polarity

Ok, this way it makes sense! Nice way to detect the correct polarity.

So far, I've tried to figure this out with a test signal, that just sends positive amplitudes to the speakers. So, the woofers should just move out. But as the bursts are to quick, its impossible to determine the correct phase this way. I just see the woofers moving but can't tell which direction.

Many thxs for this hint.
Johann

[gordonmenninger]

So whatever happened? Care to fill us in?

[bluenote56]

So whatever happened? Care to fill us in?

Of course! I had a very useful email conversation with Scott Gribble from ML. He sent me the service manual and gave a lot of hints what to inspect. Everything is ok with my speakers. All Woofers and amps are connected correctly. And: it is possible to check for correct phase by the "battery method". A 1.5V pile battery directly connected to the woofer terminals doesn't do any harm to the amps. Again, everything ok.

So, my problem is definitely related to room acoustics, rather than the speakers. As the speakers are placed on a floating wooden floor, I have granite bases beneath. It turned out, that even firing onto this granite base, the bottom woofer may initiate the floor to oscillate heavily, which results in total annihilation of a certain frequency range.

So, I've experimented with some damping materials underneath the granite bases and ended up with a thick rubber mat used to "silence" washing machines. Works great. The floor now is absolutely quiet and bass response is much better. The strange effects have gone.

Next I will try is a special damping fleece used for railway tracks.
Keep you posted.

Br
Johann

[jmschnur]

Let us know how the fleece works.


J

[sb6]

Bass traps and room treatments are your friend. I was in a similar place with my Summits not too long ago. But between significant trial and error with speaker positioning, rake angle, toe in and bass traps in all 4 floor corners + all 4 ceiling corners - substantially more bass and increased accuracy/tightness. BTW - the ceiling corner bass traps were the tipping point I think. Happy listening!