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Vandersteen 2Wq subwoofers with M5-HP crossovers - help needed

I have been happily using a pair of Vandy 2Wq subs with single-ended M5-HP crossovers for a few years now. My system was dialed in the way I like it (bass a bit on the full side, but still tight and defined). I just had my amplifier repaired and upgraded, and the new input impedance is 22k ohms vs. the 10k ohms before the upgrade. I followed the Vandersteen recommendation for the jumper settings in the M5-HP (6 and 7 only, "on" or not open), and the bass is just about MIA altogether. As per the Vandy web site, I disregarded the chart on the case of the M5-HP and followed the chart on the web site.  Because I am an idiot, I didn’t bother to mark down the settings of the jumpers prior to changing them. Anybody have any suggestions for me that will restore the bass? I am pretty sure the issue is the jumper settings. Thanks in advance!
bondmanp
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gdnrbob
2,421 posts
 
@bondmanp ,
It sounds like you are doing this the right way.
I, too, had my amps worked on and when they came back, I wasn't informed that they had lowered the impedance considerably (like 100K to 20K), so, of course, the M5-HP's needed to be adjusted. Unfortunately, they only go to 22K ohms in balanced. The bass is just a teeny bit shy, but acceptable. In conversation with Johnny, it seems Mr. V. doesn't want to go to any lower setting-I forget why.
If the batteries were near the end, and you disconnected them for a prolonged period, then they possibly were drained by not having another source (your amp) to keep the crossovers charged. 
Just thinkin'...
B

audioconnection
1,015 posts
 
(((I doubt my amp builder would get the input impedance wrong; he is a bit of a wiz at these things))))
Bond
I believe that you are totally convinced that he is a real genius and
that he thinks its the correct spec.
Problem is many amps with a given input impedance may be using use a
 bipolar driver transistor instead of a JFET and have a varied Input impedance at some frequencies.
This then sends a leaner signal into the 2WQs feed forward design
This is why I have been trying to tell you
 You really have to get a new AC voltmeter meter and confirm the impedance with the directions I gave you above.
 Only the meter will know whats right.
 
JohnnyR
 
 PS pop into the store and ill show you how to do it in 3 to 5 min
   
 
bondmanp OP
1,465 posts
 

Ok - Progress!


Last night I spoke to Richard V.  It was very worthwhile, as he explained a number of things to me about the M5-HPs.  In particular, he told me that a dead battery will not result in diminished bass output, and that the the problem did indeed seem to be the amp and the input resistance.  It was a great call, and took place before I spoke to the amp's builder.  Richard felt, as I did, that it was just too coincidental that both the M5-HPs would have their batteries die or fail at the very same time, and at the same time I put the amp back in the system.


Prior to my call with the amp's builder, I snapped a few pics of the inside of the amp and sent them to him.  Well, that was the problem:  The amp was knocked around a bit by UPS, and stuff had come loose (I had very little idea what I was looking at, but the pics showed everything).  Specifically, the transistor bridge was no longer connected to the heat sinks.  These of course overheated, and caused a chain-reaction of other issues.  So, the amp is going back to have the damage repaired and everything reattached properly.


So, there is light at the end of the tunnel.  Diagnosis is 90% of the battle.  Now, who do I speak to at UPS to get compensated?  ;-)

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gdnrbob
2,421 posts
 
Hmm, do you think it is worth it? Will the repair cost that much?
Knowing how these things play out, I bet UPS will blame the amp builder for not packaging correctly. 
Though I never had an issue of a box being so roughly treated that the internals were knocked apart. Was it double boxed?
When I sent my amps to SMc Audio, Pat recommended that I double box and put lots of extra packing to absorb a shock should it drop 5 feet.-Which is the worst case scenario if your box is the first being deposited into an airplane cargo hold with no other boxes to cushion the blow.
B
bondmanp OP
1,465 posts
 
@gdnrbob - It won't cost me anything.  The amp's builder is covering shipping and the repairs.  He is a stand up guy.  If I had to pay for the shipping and additional repairs, you might have a point, although, based on what I heard with the broken amp, I have pretty high expectations for the repaired one.  The only thing I might pay for is to have it double boxed this time.
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