Bad Summit

Bad Summit- SOLVED!

Since upgrading my XTZ Room Analyzer to the v2.0 software, I've been doing a lot of measurements while tweaking my setup and acoustic room treatments.

The new version of the XTZ software is so good, it has, unfortunately, revealed a problem with my left Summit! Ever since I got my Summits, I noticed the imaging and bass were never as precise as Craig's pair. [FONT=Verdana, Arial, Helvetica, sans-serif]I had always assumed it was my room, and my "acoustic" treatments HAVE definitely helped. [/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]However, today, I used XTZ to individually measure each speaker (nearfield to avoid room effects, and bypassing the preamp). These measurements CLEARLY demonstrate a problem with the left speaker (see attached plots). The green overlay is the LEFT speaker. The FIRST pic is the full spectrum frequency response and waterfall plot (using a sine/chirp stimulus). The 2nd is the full spectrum frequency response to pink noise.[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Looks to me like the crossover is shot, rather than a bad power board. I didn't have time to measure both speakers in the exact same room position, but doubt that would make any difference, since it's a nearfield measurement.[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]Before calling Jim Powers, I was wondering what everybody thinks about my findings, and whether it might be something other than a bad crossover. I'm hoping this might be a simple DIY board replacement, rather than having to ship the speaker back to ML.[/FONT]

[FONT=Verdana, Arial, Helvetica, sans-serif]The only positive is at least I can look forward to getting significantly improved sound once the repair is made.[/FONT]

sleepysurf said:

I didn't have time to measure both speakers in the exact same room position, but doubt that would make any difference, since it's a nearfield measurement.[/FONT]

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you must do this first as the room could still have a huge effect.

FISH_MAN said:

you must do this first as the room could still have a huge effect.

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Agreed - we need something to compare.

FISH_MAN said:

you must do this first as the room could still have a huge effect.

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Will do that ASAP, though I doubt it will make a difference.

sleepysurf said:

Will do that ASAP, though I doubt it will make a difference.

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I'll be surprised if it makes a big difference too. Measuring nearfield in an acoustically-treated space and having that big of a dip in that frequency range on one side only seems like a speaker malfunction to me. I imagine you are correct that it is a crossover issue.

Rich said:

I'll be surprised if it makes a big difference too. Measuring nearfield in an acoustically-treated space and having that big of a dip in that frequency range on one side only seems like a speaker malfunction to me. I imagine you are correct that it is a crossover issue.

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Hola chicos...you should do the measurements at the same position of the right speaker. When I was at College, my teacher said: never assume...because it will make an ass of you and me ass-u-me. Please confirm it!...happy listening,
Roberto.

Alan,

Here's another idea.

I had a minor "switching" glitch when the speaker received a signal. What occurred was that the amps for the two bass drivers didn't turn on, hence no sound from either driver.

Have you checked to see if you're getting sound from both bass drivers?

My issue turned out to be a non issue. Problem went away. Initial problem probably caused by an AC spike of some sort.

GG

It could be the crossover but it could also be few other things. I'd be cautious about jumping to conclusions based on a quick test. Here are a few possibilities I can think of. I'm sure there are other possibilities to add to the list.

1. Defective Crossover
2. One woofer wired out of phase from the other
3. Both woofers wired out of phase from the panel
4. Defective power supply
5. A deficient component upstream of the speaker (includes cables).
6. Room acoustics (especially in an asymmetrical room) That dropout in that particular freq range could simply be a null in the room where the mic was placed. I have very noticeable peaks and nulls in my listening room. For example; bass is emphasized in the back of my room and drops out near the listening position. That's one of the acoustic challenges of my room. You can hear it and I'm confident that your test would confirm that.
7. Improper test setup or invalid test (placement of mic perhaps ?)(something interfering with the test signal ?) Were all possible testing variables eliminated? Speaker A not in same position as speaker B (?)

The test results look very close except for that one dip in the lower freq range. There are many other variables that can effect imaging and bass. My speakers are typically placed further from the back wall and less toed-in than yours just to name one variable.

Just some things to think about in your troubleshooting. Can you hear a difference between the speakers?

Hi Craig,

I was going for simple based on my experience.

Good input if it's not that easy.

GG

Fortuitously got off work early today, and repeated the tests in a controlled manner... measuring each speaker from the exact same position in the room, with woofer controls each at "0" Unfortunately, got the same result (as expected). See attached plots (the good speaker has the green overlay). Will call ML shortly for their diagnosis.

sleepysurf said:

measuring each speaker from the exact same position in the room, with woofer controls each at "0" Unfortunately, got the same result (as expected). See attached plots (the good speaker has the green overlay). Will call ML shortly for their diagnosis.

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Over exposure to signals fead by a digital source is likely the cause....a strict diet of analog along with two asprin should cure it ! :devil:

Alan, On the serious side hopefully M/L can get you squared away with little fuss and pain.

...and this measurement was done with the same channel of your upstream components?

Good luck finding a resolution. I'm going to have to measure mine now!

Latest measurements all done with single (right) channel of my amp (preamp in bypass mode... unity gain), and everything else kept constant. I've shared the measurements with Jim Powers, and he also had me repeat them far-field (no significant improvement).

He suspects the problem might just be a misconnected out-of-phase woofer. If so, Craig also gets credit for suggesting that!

I did, in fact, pull the left bottom woofer when I first got the speakers to repair a bad connection, so it's conceivable I inadvertently switched wires when reassembling. Jim just sent me pics so I can check the connection, but I won't have time to do that for a couple weeks.

SUPERB customer service thus far (of course!), from Jim, and the entire ML Service Dept, including Melodie, who also works there.

If the only variable that changed was the speaker itself then that should rule out room acoustics or a component being the cause of the dip in the lower freq range. That should help narrow down the possibilities. I doubt it would be a power supply since those typically either work or they don't at all.

I'll be glad to come over and help with the speakers when we both get the time.

you have not swapped the speakers around?

Voila, fixed!!

I pulled the suspect bottom woofer, to check the connectors, but they were correctly attached. Next, per Jim's suggestion, I pulled the speaker back plate out to make sure the woofers were each connected to their proper board (see attached reference pic from Jim). Turns out, the woofer connectors were attached to the wrong boards!!

I presume the top and middle boards have unique phase differences to better integrate the two woofers and panel, or perhaps part of the crossovers reside there.

I had purchased my Summits used (just a few months old at the time), and the original owner was selling them because he was not 100% happy with the bass. Upon receiving them, I had noticed the left bottom woofer was not working, which I easily traced to a loose connector at the speaker end. I never pulled the back plate, but suspect the original owner did (while investigating the non-functioning bottom woofer), and he apparently reversed the front and bottom woofer connections when reassembling! So, for the three years I've owned my Summits, I've always had this problem!! No wonder I could never match Craig's sonics!

After the simple fix, I'm now in "hog heaven"! Overall imaging and soundstage are much improved, and of course, the upper bass and midrange are much smoother!

If it weren't for my recent purchase of the XTZ Room Analyzer, I would probably never have discovered this problem, and never achieved the full potential of my Summits!

Kudos again to ML and Jim Powers, for going above and beyond in helping me solve this issue. Now, time to re-tweak the bass settings and speaker placement for optimal sound! This is just like having a brand new pair of Summits! :bowdown:

Hmm.

Wonder if this is what the problem was with my Summits. I never liked the bottom end on them...that's why I sold them 6 months after purchasing them new.

jtwrace said:

Hmm.

Wonder if this is what the problem was with my Summits. I never liked the bottom end on them...that's why I sold them 6 months after purchasing them new.

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It's virtually impossible that a new pair of ML's would slip through with a problem like this, given how ML does frquency response testing on every individual speaker. My problem was uniquely due to a (presumably innocent) error by the original owner. For those buying used speakers, it would be prudent to measure each speakers frequency response if you have any doubts about the status of the power boards/crossover, woofers, or panel. At the least, you'll have a baseline reference for future comparison if you think a component or panel is going bad.

The fact that I was even able to partially correct the problem with room acoustic treatments, proves how critical the speaker-room interaction ultimately is for proper bass response and soundstage/imaging. I don't know what kind of room setup you had, but IMHO, properly functioning Summits are capable of great bass, if properly set up in a decent room. I can't wait to hear George's pair of Summit X's, and see what further magic ML pulled out of their design hat!

Wow, glad to hear that your speakers are now performing optimally!

Hi Alan,
I can't believe I missed this thread. Been super busy lately.

It's great to hear it all worked out with no further issues or parts. :music:

It does indeed prove the value of using measurement tools to validate system setup and equipment function (or lack thereof).