BG RD75 for line array

[ThomasW]

if they'll work (Spectra 110).

Spectra 11/1100 series aren't what's needed. They're a hybrid design with woofers...

[JohnInKY]

another RD75 setup

Understood Thomas: without tweets, it's going to be a definite "sweet spot" head in the right place system. I do a lot of casual, walk-around, in the next room listening, and special times, sit-down, serious listening when I wouldn't mind keeping my head within a several inch "sweet spot". Okay, I'm warming up to this, except for the "$3500 digital crossover"

here's what I built a few years back...these used one of the panasonic leaf's as a forward supertweeter, a neoplanar as an adjunct to the RD75's (better HF response) and peerless HDS 6.5's for mid woofs (augmented by 3 12" sonosubs)

Image not available

John L.

[CraigJ]

Hi John and welcome to HT Guide.

Thanks for showing your system over at DIYaudio. Your system looks like it should sound fantastic. If you stick around, maybe Dennis H, or someone else, will find a way to assist you in your waveguide experiment.

Craig

[JohnInKY]

waveguides

Hi John and welcome to HT Guide.

Thanks for showing your system over at DIYaudio. Your system looks like it should sound fantastic. If you stick around, maybe Dennis H, or someone else, will find a way to assist you in your waveguide experiment.

Craig

Thanx Craig...

Funny you should mention that

Seems there's little interest in these drivers over there, so I'm kinda loosing interest...

As I'm not so much interested in duplicating the "be all, end all" horn type waveguides, and seeing as I've got these "beamy" RD-75's, I was kinda looking for some info on technical aspects of the VMPS VRM-60's:



to see if I can duplicate some of the alleged benefits op the ribbon's front mounted waveguide...

John L.

[ThomasW]

What are your crossover points?

[JohnInKY]

xover

Hi Thomas...

I have the RD 75's crossed 2nd order L/R at 600 Hz, to the mid woofers, then free running up from there. To be honest, playing most music and HT, the beaming seems to be barely noticeable, but with sine waves (not that i listen to these much :W ) I can easily hear beaming as low as 2Khz.

I'm thinking of re-jiggering the 75's to 600 - 6 KHz bandwidth limited, setting the neoplanars to better match the leaf tweeter xover (6Khz on up only), mostly to see if I can improve imaging between the mains (which is already really good with decent material). But I'm also intrigued with the VMPS waveguide idea, unless someone can disuade me from pursuing it.

Here's a non-smoothed FFT of the listening location (~12 feet back) for the two main dipoles; vertical axis is 7.5 dB/div. and Audyssey room correction is active (ignore the data below ~200 hz)

Image not available

John L.

[ThomasW]

I have the RD 75's crossed 2nd order L/R at 600 Hz, to the mid woofers, then free running up from there. To be honest, playing most music and HT, the beaming seems to be barely noticeable, but with sine waves (not that i listen to these much :W ) I can easily hear beaming as low as 2Khz.

Really? When I was running the test baffles the beaming was only problematic above 5kHz.

But I'm also intrigued with the VMPS waveguide idea, unless someone can disuade me from pursuing it.

Ok, if I tell you it's only a waveguide if you believe in marketing hype is that sufficient?...

The retail RD75 have a build-in waveguide of sorts. That's why the outer edges of the metal frame are curved and there's that pointy thing between the two radiating surfaces. The depth of this 'waveguide' is what causes the cavity resonance that results in the ~5kHz spike in the FR

[JohnInKY]

influence

Really? When I was running the test baffles the beaming was only problematic above 5kHz.

hmmnn... maybe it's actually combing between the neoplanar and the 75's... I'll have to check when the wife's not around.. maybe re-jiggering the xover to move the neos above the RD's will help

Ok, if I tell you it's only a waveguide if you believe in marketing hype is that sufficient?...

yupp... that'l do it... I pretty much suspected such, but I'm always open to try new things, and I've not heard VRM60's... so I won't waste my time... :T

The retail RD75 have a build-in waveguide of sorts. That's why the outer edges of the metal frame are curved and there's that pointy thing between the two radiating surfaces. The depth of this 'waveguide' is what causes the cavity resonance that results in the ~5kHz spike in the FR

kinda figured as much... they do look similar to the EAS-10th leaf tweeters...
only bigger

thanx for the info/insights

John L.

[Newbieaudio]

John L in Ky System

Hi John L.

Are those 25" ATC ribbons in your system? I thought they would carry the high frequencies above the RD75. What range are you using for them?

I can't find any DIY ATC info anymore. I think they've switched focus to military and police applications with their "phased-array" crowd control devices and naval contracts.

Any thoughts on the ATC 25 - if that's what it is?

Thanks,

Dave

[JohnInKY]

ATC neo's

Hi Dave...

Hi John L.

Are those 25" ATC ribbons in your system? I thought they would carry the high frequencies above the RD75. What range are you using for them?

Yes they are the ATC 25" 'ers. I originally had them setup to run in parallel with the RD 75's, from 600 Hz up (less the notch filter) but I'm now modding the xover to run them from 5K up, and limit the RD 75's to 5K max.

Image not available

I can't find any DIY ATC info anymore. I think they've switched focus to military and police applications with their "phased-array" crowd control devices and naval contracts.

here's a bit of info on them:

Image not available

polar (monopole)

Image not available

they're ~ 6 dB more efficient than the BG's (mfg. states 94dB @ 1w, but I'm not so sure) so I have to pad them down a bit... they also (according to ATC) will handle 150 watts, but I'm not gonna push them like that.

Any thoughts on the ATC 25 - if that's what it is?
Thanks,

Dave

With them padded to match the BG's, the only problem I've encountered is horizontal lobing with sine wave signals; music and HT don't show much effect from this.

I'm now changing the xover so the two don't overlap much anymore... I'll let you know how it works... :T

Image not available

John L.

[CraigJ]

John L., nice finish on your speakers, and I expect they sound real nice.

Thomas, I just noticed a guy selling his Wisdom Audio Adrenaline N75s on Audiogon (selling only because of hearing damage....). Didn't you mention that these speakers also use the RD75? The speakers use a crossover point of 140 Hz and it originally sold for $55K. You must be very proud of the system that you've built, especially for your investment.

Craig

[JohnInKY]

Thanx, Craig...

I think the Wisdom's use an upgraded driver, with different film and additional traces for control and extended frequency response.

John L.

[Newbieaudio]

John L in Ky System

John,

Thanks for the extensive information on the ATC driver.

Do you know whether the ATC driver is still available by the manufacturer or as a closed-out stock item from anyone?

Dave

[Newbieaudio]

Question for ThomasW

Hi,

Chasw98 and I discussed this in depth while he was here for the RMAF. Here's what I recommended he do.. (oh and yes he to has an IB sub.

Buy enough Aura Sound NS 10"s to make an array as tall as the planar element. The FR plot should speak as to my reasons for this recommendation..

http://www.madisound.com/catalog/PDF/aurasound/NS10-513-4A.pdf

Yesterday I had a brief chat with Jon Marsh about this same subject. (he bought RD50s years ago). His thought was to use the PE RSS210. When I brought up using the NS10" he said yes they would be a better choice...

Thomas,

I'm going to trust your advice in not using a passband driver in between the IB and the RD. Given your appreciation for the M8a's performance, would you have a preference for using eight M8a per side up to 600Hz, rather than using six or seven NS10s up that high? I'll be trading some output at the bottom of the range by using M8a, but think I'll be gaining clairity up to 600 Hz compared to if I were using the NS10.

Your thoughts?

Dave

[ThomasW]

Either drivers will easily do 600Hz. The question is do you want the wider baffle demanded by the NS10 and the added output it offers down low?

FYI for others following this thread.

I received 16 Neo 3 pdf's. And as soon as I can design a clever mounting system I'll have an line array of them to try out with my spare RD75's

[Newbieaudio]

ATC with RD75

JohnInKY,

I've sent you a PM.

Dave

[ThomasW]

Looking at his profile you'll find he hasn't logged onto the forum since 06-20-2009, so it's unlikely he's checking for PMs

[brucemck2]

What would be the pro's/con's of a line of Neo 8s vs the RD75 (assuming a line of Neo 3s to complement the high end and a line of 6.5" to 10" cones on the low end)?

[Johnloudb]

What would be the pro's/con's of a line of Neo 8s vs the RD75 (assuming a line of Neo 3s to complement the high end and a line of 6.5" to 10" cones on the low end)?

If you use the neo8 you can get a higher sensitvity loudspeaker ... very high actually, with a higher impedance. So they won't need so much power and would be more amplifier friendly.

As far and sound quality, I don't know. That would likely be pretty subjective, since I think both the RD75 and Neo8 are very good midrange drivers.

[Newbieaudio]

ThomasW.

Thanks. I had looked on his profile to see if it showed his activity, but I couldn't find it. I went back and now know where to look.

What I was after was whether he had the opportunity to change the crossover frequency of his ATC with his RD75s. He's commented that they added a lot to the sound in parallel with his RD75 covering the same range, but was going to try crossing over higher as an experiment.

The width of the driven area on the ATC-25 seems at least as wide as on the RD-75, implying the two drivers would have similar beaming.

I got the impression both drivers cover a similar range - neither having good off-axis performance above ~ 5kHz.

Any thoughts by anyone on this?

[ThomasW]

I got the impression both drivers cover a similar range - neither having good off-axis performance above ~ 5kHz.

Correct

[bikmakr]

RD 75....is anyone out there?

I know this thread hasn't been active for a while and I hope those participating are still around. I am re-starting a project I started 3 years ago using 3 RD-75's per channel and 2 Velodyne Sig 1812 in stereo for the bottom and mid-bass. I have experimented with different baffle widths and dispersion angles of the 3 RD's. They seem to like a 1 degree angle for max horizontal dispersion without dead spots. I have owned Genesis 201's and Infinity BETA's and Gammas and love the dipole sound. The shortcoming of the 201's were their ability to create impact-full SPL's. My listening room is 16' x 56' with flat 9' ceiling. My original thinking was that using enough RD75, I could cross them low enough to blend with the upper 12" woofers of the big Velos, without stressing them. THis has not been the case, as there is an absence of mid-bass and an open high end (possibly requiring an array of tweets). I'm a toolmaker that owns my own machine shop, so the mechanical challenge is easy. What I do lack is the electrical knowledge to design a truly exceptional system. Any help, ideas would truly be appreciated and any reciprocal help in the structural area would be gladly given.

[Johnloudb]

I know this thread hasn't been active for a while and I hope those participating are still around. I am re-starting a project I started 3 years ago using 3 RD-75's per channel and 2 Velodyne Sig 1812 in stereo for the bottom and mid-bass. I have experimented with different baffle widths and dispersion angles of the 3 RD's. They seem to like a 1 degree angle for max horizontal dispersion without dead spots. I have owned Genesis 201's and Infinity BETA's and Gammas and love the dipole sound. The shortcoming of the 201's were their ability to create impact-full SPL's. My listening room is 16' x 56' with flat 9' ceiling. My original thinking was that using enough RD75, I could cross them low enough to blend with the upper 12" woofers of the big Velos, without stressing them. THis has not been the case, as there is an absence of mid-bass and an open high end (possibly requiring an array of tweets). I'm a toolmaker that owns my own machine shop, so the mechanical challenge is easy. What I do lack is the electrical knowledge to design a truly exceptional system. Any help, ideas would truly be appreciated and any reciprocal help in the structural area would be gladly given.

Hi, That system looks beautiful!!!

you could build a line array of woofers crossed over at about 250-300hz. Here's my dipole line array project that I'm finishing up. I cross over at 600Hz, but you've got a different design going on there and given the distance that a dipole woofer array would you wouldn't want to cross that high.

https://www.htguide.com/forum/showthread.php?t=36874-Kleos-Dipole-Line-Array

There is also this thread, which inspired my design:

https://www.htguide.com/forum/showthread.php?t=31848&page=1

Once you get things figured out start a build tread cause it would fun seeing this come together! :T

[bikmakr]

John,

Thank you for your insight. Are there any recommendations for a good active PC based equalizer and/or crossover? I've been reading more about boosting the top end above 6K and using an active notch filter, removing the passive one.

[CraigJ]

Hi Bikmakr and welcome to HTGuide,

Thomas has been on a long vacation and I'm sure Jon Marsh will drop in and introduce himself, assuming he is not working. First, extremely nice system and gotta love your media room. I presume you have seen StigEric's build over at diy audio; http://www.diyaudio.com/forums/multi...ml#post2922246





Yes, what looks like pillars in the second picture are actually the RD-75s.

A simple and Siegfried Linkwitz/Davey approved digital crossover can be found here; http://www.linkwitzlab.com/LX521/DSP_challenge.htm

Have fun, time to go kiteboarding.

Cj

[JonMarsh]

I know this thread hasn't been active for a while and I hope those participating are still around. I am re-starting a project I started 3 years ago using 3 RD-75's per channel and 2 Velodyne Sig 1812 in stereo for the bottom and mid-bass. I have experimented with different baffle widths and dispersion angles of the 3 RD's. They seem to like a 1 degree angle for max horizontal dispersion without dead spots. I have owned Genesis 201's and Infinity BETA's and Gammas and love the dipole sound. The shortcoming of the 201's were their ability to create impact-full SPL's. My listening room is 16' x 56' with flat 9' ceiling. My original thinking was that using enough RD75, I could cross them low enough to blend with the upper 12" woofers of the big Velos, without stressing them. THis has not been the case, as there is an absence of mid-bass and an open high end (possibly requiring an array of tweets). I'm a toolmaker that owns my own machine shop, so the mechanical challenge is easy. What I do lack is the electrical knowledge to design a truly exceptional system. Any help, ideas would truly be appreciated and any reciprocal help in the structural area would be gladly given.

Well, you've got some interesting makings here, but you have to remember there's no getting around Father Physics, any more than Mother Nature. So let's review some of the considerations you will need to work with...

• The RD drivers are often looked at as dipole drivers as well as line array type drivers- but they are no more inherently dipole drivers than most other dynamic drivers- they have no built in EQ or shaping to work in a dipole setup, PARTICULARLY not a naked dipole setup, where the dipole cancellation frequency will start fairly high
• The rated response for the RD's is assuming a sealed enclosure. Not a dipole.
• The RD's have a cavity in front of the diaphragm, which creates two effects- a resonance or peak in the on axis repsonse around 5 kHz, and a severe roll off in the off axis response
• Using the RD50 or 75 in a dipole with any significant low end below 1 kHz mandates using substantial wings to extend the physical size of the dipole and lower the dipole transition frequency to a usable range- one good type of wing to use is an electrostatic or dynamic planar driver such as an Acoustat 1+1.
• At the least, the RD's need a notch filter to deal with the cavity resonance at 5 kHz.
• The better solution is to crossover to a different line ribbon tweeter array at or below 5 kHz that has wider dispersion than the RD75- the lower the better, becuase the horizontal spacing creates a narrowing in the polar response the higher that crossover frequency is.
• By measurement, even with good size wings, the RD75 and 50 have their lowest distortion above 600 Hz; they just don't have the radiating area to pump much sound below that.
• Suggested optimum first cut setup (by me) is 500-600 Hz lower crossover and 3 kHz upper crossover.. Yes, this is a midrange driver, and these make a very good midrange driver. They're far from SOTA below 500 Hz and above 5 kHz.

In your case, with your three wide panels, I'd start by adding wings to the panels to extend the low end, (we're talking 12-18" on each side) and I would roll off the outside RD's 1st order above 1500-2000 Hz, so that you don't have such a wide radiating source at high frequencies (which also narrows your dispersion). Realistically, you need to do some shelving EQ to boot the center RD a bit. With something like a MiniDSP this is all fairly doable, just time consuming, and would require measurement as well as DSP EQ. OR, it could all be done with passive crossovers, but the same general procedure applies as for developing a standard three way speaker- measure in place, and use something like LspCAD or SoundEasy to model the system and develop the crossover.

But in your situation I'd be looking for a real tweeter array to use with the RD's, and something different for the mid bass. You can get a lot of ideas, I'm sure, by searching on the internet and even on this site.

This is one of the earliest.



One from Europe:



There are many other line array projects with RD's or other planar drivers which could be useful models, like Chas98's.