[simon wagstaff]

Working on my RM2s. I sent the 626 off to Danny Ritchie at GR Research and he did a great job with them. Replaced the spiral tweeters with the ribbons, and basically build me a new crossover from scratch. They sound GREAT!

However, they just don't have that lower midrange transparency of the RM2s. The RM2s had issues. Channel balance was off by 8 db, room correction showed that they needed to be crossed over at 110 hz, something wrong there.

I couldn't ship them but I found  a local guy who had some experience, not a lot, to take a look at them. Cleaned the l-pads like crazy, fixed most of the channel balance issues. He can't find anything wrong with the crossovers so here is my plan. Keep in mind that as they were, they sounded fantastic.

I am just going to leave the mid and tweeter crossover alone. Hard wire the woofers to the terminals with no crossover. I have a pair of VMPS smaller subs, with plate amps. The plates have a high pass line level crossover. I am going to use the crossover in my pre-pro, it can go up to 250 hz. I might need 280 but I hope this will be close enough. Run a cable to the plate amp, run it up to maybe 80 hz, line out from the plate amp to an external amp to drive the woofers in the RM2.  Levels may be tricky, only one way to find out.

I saw a previous post that mentioned schematics for the crossovers may be available. Certainly this is a case where an external crossover for the woofers might be useful.

[Evoke]

Working on my RM2s. I sent the 626 off to Danny Ritchie at GR Research and he did a great job with them. Replaced the spiral tweeters with the ribbons, and basically build me a new crossover from scratch. They sound GREAT!

However, they just don't have that lower midrange transparency of the RM2s. They had issues. Channel balance was off by 8 db, room correction showed that they needed to be crossed over at 110 hz, something wrong there.

I couldn't ship them but I found  a local guy who had some experience, not a lot, to take a look at them. Cleaned the l-pads like crazy, fixed most of the channel balance issues. He can't find anything wrong with the crossovers so here is my plan. Keep in mind that as they were, they sounded fantastic.

I am just going to leave the mid and tweeter crossover alone. Hard wire the woofers to the terminals with no crossover. I have a pair of VMPS smaller subs, with plate amps. The plates have a high pass line level crossover. I am going to use the crossover in my pre-pro, it can go up to 250 hz. I might need 280 but I hope this will be close enough. Run a cable to the plate amp, run it up to maybe 80 hz, line out from the plate amp to an external amp to drive the woofers in the RM2.  Levels may be tricky, only one way to find out.

I saw a previous post that mentioned schematics for the crossovers may be available. Certainly this is a case where an external crossover for the woofers might be useful.

Hey, Simon -


Time to hit the pause button. Let's break it down. First, outside of some personal opinions, Danny is a very accomplished engineer. He is proficient in crossover design with experience, software and testing. I think upgrading to the ribbons is a great idea. I'm confident he did a great job with the crossover.


That said, it is not possible for the 626 to sound like an RM2. The RM 2 has double the mid-panels and a 12" woofer and a 12" passive driver compared to the single 626 6" driver. The RM2 is moving at least 300% more air. I would talk with Dannie - there's no way he sent the speakers back with that kind of imbalance. I can't imagine he didn't check the L-Pads.


As for your plan - if you run the woofer full range without the crossover, or with an outboard crossover at a different slope than the internal crossover it will be out of phase. It will also result in poor transients in the mid bass that are muddy. This will cloud the imaging minimally. Also, bass plate amps are optimized for frequencies for sub use. They don't typically sound good in higher frequency applications.


None of this is bad news - I would suggest you rethink your plan. It should begin with talking to Danny in my opinion. You may spend a lot of time and money on your ideas and in the end a call with Danny and a shipping charge may be much cheaper with better results in the end.

Mark
Evoke Speakers

[simon wagstaff]

You misunderstood. Danny did a great job. The 626 sound great! There was no way I could ship the RM2s to Texas.

My language was imprecise. I have fixed it.

 The woofers will only see signal from 80-250hz.

The mids and tweeters will not be affected.

[Evoke]

Gotcha - thanks   I was so confused.  AND I was past my coffee quota for the day LOL

[simon wagstaff]

In an earlier post there was a reference to RM2 crossover schematics. I'd like to at least see what was involved in putting them together, at least for the woofer. I did a search and couldn't come up with anything. Thanks!

[Early B.]

You misunderstood. Danny did a great job. The 626 sound great! There was no way I could ship the RM2s to Texas.

You should still talk to Danny. He may have already have an upgraded schematic for the RM2 from previous work. Also, ask him if you can ship only one speaker. He'll probably test it for free. Worst case scenario -- you're out a few bucks for shipping.

Your idea about "fixing" the speaker isn't ideal. VMPS crossovers, generally, can be vastly improved.
FWIW - I've owned several VMPS and GR Research speakers, so I'm familiar with Brian and Danny's work.   

[simon wagstaff]

I have chatted with Danny about them, in general terms. He wanted both of them shipped to Texas, that is really not an option. I'll ask him about a schematic for the external woofer crossover, that is all I would really need. The 626s that he re-worked for me really do sound great, the RM2 though has a transparency in the lower midrange that is to die for.

Keep in mind I have a pair of smaller VMPS subs as well. I just purchased an older Adcom amp that has level controls. It should work, 250 hz crossover from my pre-pro (lower is audessey says so), high pass from plate amp to woofer amp around 80 hz. I am going to try the set up first with a different 250 watt amp for the woofers without the subs, but input level sensitivity may be an issue.

If I can't get them to sing, the 626s are very nice.

[Early B.]

OK, but keep in mind that every time you change the crossover point, you gotta pinch putty. 

[HAL]

Another way to approach the RM2 rework is a digital crossover for three way operation like Brian did with the later DCX2496 systems.  If you like the existing RM2 crossover, a simple measurement system like CLIO Pocket can be used to make the electrical response measurements needed to design the digital version.  The measurements have to be done at the speaker terminals after the crossover, which may or may not be easy.  There are now much better digital crossovers.

Danny's QSO626FST passive crossover is great with mine.  I built the QSO626FST kits with the individual driver wiring to three sets of terminals on the outside of the cabinet to make it easy.  Also did the same thing with a pair of RM40's a long time ago and sounded much better with the digital crossover. More recently with a friends pair of RM50s.

If not, acoustic measurements of the speaker have to be made to design a new crossover, hence Danny needing the speakers. That would also let him check the channel imbalance you have seen.

Good luck with the project! The NEO panels are special with the FST.