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The right mid panel of my T IVa's started buzzing last week so I swapped in the RD75's. As of now I am using the Magnepan external crossover and will be getting a DBX Venu360 in the near future so I can bi-amp instead.I am looking for a good starting point to cross over, freqs and slopes(s), from the T IVa mid base to the RD75's.
The previous recommendation from @andyr I took to be for a full T IVa set rather than for RD75's\T IVa's.
T IVa's to RD75's would be great but RD75's to anything would be helpful.
Edits: 02/14/21Follow Ups:
Did you make your RD75 baffles and if so, how did you derive/settle on the shape ?
TIA
The guy I bought the RD75's from made the baffles. He sent me some links but I didn't find any relevant background. I was hoping someone on here would know. LOL
I was looking to buy only the RD75's but he definitely wanted me to have the baffles. He drove from Tennessee to Dayton Ohio to deliver them.
It you listen to them standing and then at various heights you can definitely hear more bass as the listening point is lower.
I look forward to measuring the freq response at different height\distance points.
The Venu360 will arrive Thursday. I think I have everything I need to complete the setup except two more XLR cables. Well, I have some cheapie XLR to RCA's that I could use until I get something better.
I may just cut a slot on them for the tweeters and strip the stain and run them like this, at least in the short term, while I figure out if I want to make new baffles and what shape they would be.
Part of it is to average out the effects of edge diffraction (by varing the distance from the center of the driver to the baffle edge and vary the total width of the baffle) over the height of the baffle, but it appears to have redistributed it from top to bottom.
FWIW, you can attach the ribbons to the sides of your existing baffle until you get new baffles. Magnepan did this for their 30.7 for condos demos, but it also appears they trimmed off one side of the metal cage which would not be necessary for a interim configuration.
Edits: 02/17/21 02/17/21 02/17/21
Thank you @emailtim!
Can you suggest a good crossover freq and slope from the RD75 to the tweeter?
I'm using 2500 Hz with my Neo 8's, if only because that's what the original crossover does. :-) But I think it's safe to say that that's safe, given that Magnepan chose it. 18 dB/octave would be safe, seeing as you can't make a compound curve with the midrange since the RD75's play so low. (An LR4 might be even better, but it could make the transition between the RD's and the Neos more obvious.)
In general, the higher the crossover point, the louder you'll be able to play without the ribbons starting to sound hard, but as you raise it, you get more crossover lobing and head position becomes more critical as a result. Satie is the expert here, since he's experimented with various crossover points.
I just did a comparison, Neo 8 array in one speaker and Neo 8 + ribbon in the other, and the ribbon won. It's just a better tweeter, one of the best ever made -- more transparent, extended, detailed, and incisive (transient response -- pianos are more realistic, etc.). Not that the Neos weren't credible on their own, and there are definite advantages to running a single driver full range.
Sorry, have nothing to offer other than to keep the XO's out of the most sensitive hearing range [2kHz-5kHz]. Higher XO points conflicts with the optimal physical proximity limitations. Ideally, you want the mids and tweeters physically located as close as possible which in turn causes line array structural hurdlers.I experimented a little with trying to integrate the ribbons, but ended up running my NEO8's full range on the top end without the ribbons.
I took off the tweeter side wood styles and attached a narrow baffles containing the NEO8's in place of the wood styles to get them as close to the ribbons as possible without cutting the original Maggie frames.
I then put the NEO8's in their own separate baffles and are running them that way. I may try pulling the ribbons and attaching them to the sides of the NEO8 baffle like what Magnepan has done but am not at that stage yet.
FWIW, Josh and I are using software XO's for experimentation which allows you to try virtually any point/slope combinations. Josh and Satie can probably give you a better idea because they are already running the ribbons with the NEO8s.
Edits: 02/18/21 02/18/21 02/18/21
Thank you @josh358. Very helpful!
Initially I will be using a DBX Venu360 which can do a LR48. I will use that for a while to try some different things and hopefully get close to a good setting by the time I build my Pass DIY biamp 6-24 which has 6 to 24 dB slopes.
It is my plan to cut the tweeters into the wings and upgrade and tune the high pass to the tweeter. My friend in Dayton with a woodworking shop has just moved so it might be a month or so before he is set up to make some sawdust.
I am using the Magnepan external crossover now. It is a little strong in the lower mid\upper mid base range.
One of the mids buzzes. All four base panels are fine.
I am a purist. LOL I really like the Tympani bass. Fortunately I have a large enough listening room to let them run. When I was looking for a house I told the Realtor I had three things that were important. A large enough room for the Maggies, a two car garage and indoor plumbing. He thought I was nuts. I probably am. LOL
I need to put my measuring rig together and start doing some analysis. I am sure the system will benefit from some tuning. Did you make those diffusers?
LOL -- a large sound room would be first on my list for a new house as well. :-)I had the same buzzing problem with the mids on my IVA's. It looks like they segmented the driver by sticking the diaphragm to pieces of foam tape and after 40 years the tape is loosening up. I used to fix them temporarily by pressing down on the tape when they started to buzz. I suppose you could make a capo of sorts for the front, keeping a really low profile to minimize diffraction. Or you could drill a bolt hole through everything and hope that you miss the magnets and conductors, yikes.
I also found that the mids had delaminated near the tape and fixed that.
Cool about the Pass XO. These diffusers would be hard to build -- not only do you have to cut all the pieces (which people have done), but some of the surfaces are faceted, so you'd have to do that as well. I bought the Vicoustic DC-2. If you want to DIY a diffuser, a 2D QRD is much easier to build than a skyline -- emailtim is the expert on that, he did some beautiful work. AFAIK, there's no real advantage to a 3D diffuser with full height line sources.
You can buy the Vicoustics here, but they're cheaper if you order them from Thomann in Germany -- 336 Euros including shipping for the six I have (I'm thinking of getting six more). I got the EPS rather than the wood version, because it's cheaper and much lighter so it's easier to experiment with. Based on their data, the EPS version has more effective diffusion than the wooden ones, but also more absorption (painting helps with that). But I always wonder whether you can hear the lively resonance of styrofoam. I wonder if putting damping sheets on the rear would help with that? Painting would tend to damp the resonance too, or add mass, shifting it to a lower frequency. In any case, I haven't yet done any experiments to try to ascertain whether it makes a difference.
I prefer these to my QRD diffusers because with the QRD's I hear the lobing when I move my head.
Here's the impulse response of my left channel (the worse one) with diffusion and some absorption and diffusion in back:
As you can see, everything is below -15 dB in the critical region below 40 ms except for a spike that I haven't tracked down yet. That's much better than it was -- it was up at -10 dB -- and some would say it's enough, though you generally aim for -20 dB in a control room. I'm hoping with some work to get it that low. If your early reflections are higher, you won't believe how much of a difference lowering them makes! The image opens up dramatically, becomes spacious rather than flat and congested.
I've made some pretty good improvements in the waterfall as well with just minimal bass trapping. One nice thing about dipoles is that they really don't need much room treatment.
Edits: 02/20/21
You might want to try steeper slopes on the bass panels to keep the RD75's midrange cleaner.Josh has been experimenting with his NEO8/Tympani XO configuration so maybe he can chime in with his findings.
Edits: 02/14/21
Thanks Tim. I have noticed some congestion in the lower mid\upper bass region during some songs with more complex sound.
Based on my experience, the Neo 8's are a lot cleaner than the Tympani bass panels, so the lower I set the crossover, the cleaner the sound. But the RD-75's cross over at least 100 Hz below the Neo 8's, so my crossover experience doesn't apply. Genesis crossed the RD's to the woofers at 100, which can be increased to 120 in the case of a large room:
https://www.genesisloudspeakers.com/wp-content/uploads/2017/12/prime_owners_manual.pdf
The Genesis does have a huge baffle, though, so you might have to up the crossover to compensate for the smaller baffle.
I'd be inclined to make the crossover slope as high as possible, e.g., LR-8, since it lets you cross over at the lowest possible frequency. (This requires an active crossover.) However, you may be bothered by the abrupt change in sound character, in which case you can use a more relaxed slope and move the XO up to keep from overdriving the RD. (IIRC, the group delay of an 8 pole XO is audible, another consideration.)
BTW, you might find that putting the IVA's ribbon tweeter next to the RD's sounds better than using the RD's alone. I think it depends on the level you like to play at -- the ribbon is a better tweeter, but it starts to sound hard at high levels. The ribbon will work fine on the RD 75's to give it a try. I haven't checked impedance and sensitivity, but with the a few resistors (probably) you can just use the original Magnepan crossover for an experiment.
Re the woofers -- if the bass panels are buzzing, they need repair. Doesn't take long, I did it on my own. I found that the wires had lifted much further in than I would have expected and needless to say that will compromise sound quality. So I'd fix them before anything else.
I don't know that you can do much better than the Tympani panels in the midbass, so I'd stick with those. I'm told that the GR Research H-frame dipoles sound similar (I've only heard them at shows), but since you have the room, I think it makes more sense to use what you have. But if you don't want the ribbon tweeter, you could consider making three of the GR research H-frame OB woofers, or a ripole, and sell the Tympanis -- it would really open up your room.
But crossing them over to the Tympani woofers will definitely sound great, doubly so (I think) if you add the ribbon.
Finally, if you can tolerate the look, I suspect that adding some diffusers at the first reflection points like this will make a big difference (I just moved my speakers to a new room, so they're just propped against the wall):
Thanks for all the info @josh358. It will take me a while to digest all of it.
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