[drtweak]

I'm basically looking for an explanation of why the sound of my add-on Walsh-type tweeter changes so much with the reversal of polarity of its passive 2nd order crossover which is connected to the RM2s in parallel with the mid/high speaker terminals.

I noticed that the EQ I was using on the turntable source was set brighter than that for CD and my digital sources. So maybe the brighter EQ combined with the more extended tweeter put it over the edge for vinyl.

I may try a different (less-bright) EQ setting for the phono over the weekend and see how that works for me. But I'm still curious as to how the polarity reversal of the passive crossover on the tweeter would/should affect the sound and/or the crossover point???

I'm sure some of you may be wondering why I just don't go for the FST ribbon tweeters on the VMPS (instead of the spiral ribbons). I owned RM30s previously with the FST tweeters and I think the Walsh-type 360-degree tweeters I'm using with the RM2's sound better than the FST tweets.

I think I may have this figured out. I don't believe the crossover frequency changes with polarity. I think what I'm hearing is the effect of polarity reversal. One way both tweeters reinforce one another where they overlap and the other way they tend to cancel. I believe the RM2 speaker's internal crossover is around 10kHz and the add-on tweeter's crossover is a bit lower at around 9k or a little below that so I have the potential for cancellations and reinforcements between the VMPS drivers and the add-on tweeter...

I suppose one way to minimize this effect would be to turn down the tweeter and/or midrange pots on the RM2's until the effect of polarity reversal is less apparent. I will try this over the weekend when I have time to play with it.  Meanwhile, any thoughts or comments are welcome!

[John Casler]

Hi DrTweak,

Sounds like a good question for Big B, but the current XO to the FST is at 6.9Khz not 10Khz.

If your RM2s are recent, then you may also be hearing (or not hearing) a substantial gap if you are XO'ing at 9 or 10Khz.

[Brian Cheney]

I have no experience with the Walsh tweeter and can't comment.

[drtweak]

Hi John,

The RM2's I have are a little older I believe and I think they have the higher crossover point to the spiral ribbon pair.

I think the problem is where the spiral tweeters and the Walsh overlap, and for that matter, if the midrange ribbons are crossed at the original 10k then they could be interfering as well.

I am going to try tweaking the midrange and high frequency controls on the RM2's and see if I can fine tune it a little better.  Right now it's real close but I believe I can do a little better.  I will say this is a pretty outrageous sounding setup so I'm hoping I can get it just right.

Thanks to John and Brian for replying.

[John Casler]

If they have the Spiral Tweets then B, can say the XO point, but there may also be another element at play (but remember I am NOT a speaker designer)

All drivers that cover certain frequencies require a preferred spacing between themselves depending on the size of the wavelengths. 

That is the tweeter needs to be a certain specific distance from the MR for the best coverage, integration, and least cancellation between drivers of the forward firing information.

If you are setting the Walsh Drivers on the top of the cabinets then that too "might" play a small role in the blending and interactions.

Just a thought from a non-technical (most of the time) listener, and long time tweeker.

[drtweak]

Hi John,

You make a good point about the driver spacing and the Walsh's are set on top of the RM2 cabinets as you thought. I did play with the spacing fore and aft, and left to right and fine tuned the positioning.

Since my post I was able to adjust the midrange and tweeter pots for the most seamless blend with the Walsh possible (without changing parts) and I am very satisfied with the outcome.  It sounds amazingly good and I think if Brian heard it he might start making such a version.

Thanks again,

Frank