(Mostly) RS dipole 4-way

[Paul Ebert]

I'm considering the following:

Vifa DX25 tweeter
RS52 dome midrange x 2 in bipole configuration
RS270 woofer x 2 in dipole configuration
RSS390 sub x 2 in dipole (w frame) configuration

The design objectives are dipole, efficiency > 90 dB/watt, and cost-effectiveness.

My main question is if the RS270 and RS52 will be able to work together. Can the RS270 be crossed over > 600 hz?

Any other thoughts on this system would also be appreciated.

Oh, I'd be using active crossovers, possibly with the exception of the mid to the tweeter.

Thanks.

Paul

[cjd]

No on the RS270's to the RS52. 600Hz is do-able (though it's snug) for the 270's, but it's not for the RS52 I think.

RS52 is not, of course, dipole. I would mate it to an ~18mm tweeter as well, not the 25mm.

RS225 may do the trick though, I think.

C

[Paul H]

Paul,

I'll second Chris' suggestion to go to 8" drivers to cross to the dome mid - around 1000Hz maybe, although you'll want to fine-tune that - easily done with active crossovers.

Chris - Paul noted the use of two mid domes in bipole - I'm assuming one is rear-firing to get him the dipole effect.

Paul

[Amphiprion]

I'm gonna sound like a broken record today but....

you could use the Neo3 PDR in a dipole setup (take off back plate). The large flange might give you too much distance between it and the mid though.

[Marzen]

I would mate it to an ~18mm tweeter as well, not the 25mm.
C

Any personal prefs for these? I've been procrastinating in finding another tweet to try with the RS52.

thanks,
ward

[joecarrow]

I saw somebody take the plastic cup off of the back of the RS52, and the photo I saw looked really open in the back. They're cheap enough (compared to the rest of the project) that you could probably get one to experiment with and see if you get good dipole radiation by removing the cup.

[Paul Ebert]

I'll happily entertain a smaller tweet if I can find one with efficiency around 93 dB (oh, and I'd rather it wasn't a ribbon).

I've read (Zaph, I recall) that the Neo 3 used as a dipole doesn't work very well. Overdamped, I think he said. Also, the PDR is rated at 90 dB. Alas. The regular Neo 3 is rated at 93, but I wonder if its dispersion is as good as the DX25. I am also considering the HDS tweeter (810921) and the Seas 29TFFW (which is bigger, yet). What I'd really like is a SS 6600 aircirc, but $ 8O $

I was really hoping the RS270 would work as a pair of them in parallel gives me 93 dB or so. The RS225s would be 91, I believe. Perhaps, I should not sweat it, but provide some gain via the active crossover. I'm trying to keep the transfer functions as minimized as I can.

What about using a pair of RS225-4s in series? That would give me 92 dB. Also, it has a unshielded (hence, smaller) magnet which might be better for a dipole.

Yes, the second RS52 would be back-firing to give me a bipole. Do you really think that two of 'em cannot reach 600?

Thanks! More thoughts?

Paul

[cjd]

Are you really intending to go biple on the mids, or do you mean dipole?

That would be *really* odd transitions, dipole>bipole>monopole

Your sensitivity target is putting a lot of restrictions on your driver choices - this is fine, but IMHO is a less ideal method for choosing.

As for a 18mm tweeter, the little (and cheap!) Dayton neo tweeters are better than they should be and are one option - gets you decent center-to-center distance. The OW1 is another option if you need to keep sensitivity up.

I would probably be looking at the Neo8 as mid and Neo3 or a ribbon as tweeter (I would also likely not worry about monopole tweeter).

C

[Paul Ebert]

Well, now that I think about it (bipole vs. dipole), I'm not sure. If I have a rear firing RS52 and I wire it out of phase with respect to the front firing driver, would that be dipole? And, would the same configuration with the drivers in phase be bipole? If that is correct, then I could certainly go dipole and I would be interested in doing so. That is, if I also got the 3 dB boost of the 2 paralleled drivers.

Yeah, I've basically fallen in love with high-efficiency designs and the intended amplifiers are Pass Zen version 9s (10 - 15 watt class A). I'd have an amp for the woofers and another for the mids / tweeters. The subs will (only) have about 40 watts supplied by my ancient, but nice, Stax DA-80.

I'll look into the Dayton tweets. Another option might be the Vifa D26NC55 doubled up in dipole (assuming I can still find them). That doubles the cost for the tweeters, but that's OK. I suppose the Neo 3 PDR could work that way also.

Thanks!

Paul

[cjd]

Neo8 should hit your sensitivity needs in a dipole midrange. If you're crossing ~3k-5k you can toss a monopole tweeter in there - many of the studies I've seen suggest the sound is better with a monopole on the top end. My own choice would be a ribbon.

It will need to cross ~1k, so RS225's work - if you go to the slightly smaller subs, you can work with a quad of RS180's I believe, depends on baffle some IIRC.

At this point though, it's simply what I have been pondering myself. And it's been a while since I've done any of the number crunching. And I *have* been hoping to keep sensitivity up around 92dB even though, if I ever finish them, I'll have some very good amps capable of a couple hundred watts output. More burst output. Sound very similar to Aleph. Backed by a BOSOZ variant.

C

[BobEllis]

...Yeah, I've basically fallen in love with high-efficiency designs and the intended amplifiers are Pass Zen version 9s (10 - 15 watt class A). I'd have an amp for the woofers and another for the mids / tweeters. The subs will (only) have about 40 watts supplied by my ancient, but nice, Stax DA-80...

A pair or trio of ZV9s a side will keep you nice and warm in the winter. I have a pair of hotrodded A75s in my system. As originally set up there was about 800W of waste heat dumping into my room. I couldn't take the heat, even in the winter, and rebiased to about 400W. That's still to much during our current heat wave. Looking at bringing my Leach amps out of the bedroom. YMMV, and I haven't heard a ZV9 to say whether the sound would be worth it.

Just because you have high efficiency speakers doesn't mean you don't need power. A 6dB increase in sensitiviy only reduces your power requirement by a factor of four. If your music has peaks 30 db above average and you're listening at .25W you'll need 250 available to avoid clipping. Dire Straits' "Money for Nothing" has that kind of range between the intro and the drum solo. Sure, single ended amps tend to clip euphonically if not driven too hard, but I'd rather keep it clean. Again it's a personal taste thing. ZV9s would make nice tweeter amps, I bet.

My subs are JBL2245Hs - 94 dB/2.83V midband. With the ~6 dB of EQ required to get to 20Hz in room 250W really isn't enough for loud passages. A bridged DH500 (800+W) brings them alive. Can you tell dynamics are important to my listening enjoyment?

[Doug Lockwood]

I agree that the RS270 isn't optimum at 1 KHz.
However, if you would like a subjective evaluation, I could try it. My current Test Mules are 2 RS270, a Seas 14cm midrange and a Neo3 (not PDR) without the back cup.
Right now the xo is set to 400Hz and 2.5 KHz, but I could re-program the DCX in under 5 minutes.
Let me know.

By the way, Chris is right. The Dayton nd20 neo tweeter is amazing, as long as you can cross it @ 4 KHz or higher.

Sounds like you will have an amazing speaker when you are done. :T

Doug

[Landroval]

Well, now that I think about it (bipole vs. dipole), I'm not sure. If I have a rear firing RS52 and I wire it out of phase with respect to the front firing driver, would that be dipole? And, would the same configuration with the drivers in phase be bipole? If that is correct, then I could certainly go dipole and I would be interested in doing so.

All true here.

That is, if I also got the 3 dB boost of the 2 paralleled drivers.

If you have one front firing and one back firing RS52 out of phase and parallelled, you will not get 3 dB nor 6 dB boost. Depending on the damping on the back wall and amount of reflections you will get very little or no efficiency boost, but you will in theory get a dipole radiation pattern.

With in phase wiring you will neither gain in efficiency exept under the baffle step frequency (+6dB) which in this case is probably a lot less than 1000Hz.

[Paul Ebert]

A pair or trio of ZV9s a side will keep you nice and warm in the winter.

This is true. Winters can be quite harsh here in central NY.

If you have one front firing and one back firing RS52 out of phase and parallelled, you will not get 3 dB nor 6 dB boost. Depending on the damping on the back wall and amount of reflections you will get very little or no efficiency boost, but you will in theory get a dipole radiation pattern.

With in phase wiring you will neither gain in efficiency exept under the baffle step frequency (+6dB) which in this case is probably a lot less than 1000Hz.

In that case, it seems I'm back to the drawing board as I will not reach my SPL target for any of the drivers but the tweeter. So, are you saying that the only way to get the boost is to have the drivers facing forward, in phase, and monopole?

The ND20 does seem quite nice with a pocket change price. Definitely worth giving them a try.

I do not think I want to cross over to the mid at 1K. If that is really what the RS52 needs, I think I need to consider something else. A shame. I'm not sure what I think about the Neo8.

[jdybnis]

What about using a pair of RS52's? That should let you cross at about 700Hz. You might have to go a bit lower with the tweeter though, say 2.5k to avoid lobing.

[Landroval]

Two dome midranges could work, but I would then go with two Morels because of center to center issues. Also you could try this "93dB" Hi-Vi dome:

http://www.madisound.com/cgi-bin/index.cgi?cart_id=1466463.24799&pid=1826

Or a fostex fullrange (there's many options in 90-100dB league):

http://www.madisound.com/cgi-bin/index.cgi?cart_id=1466463.24799&pid=326

Or of course two RS150 or similar midranges.

[Paul Ebert]

OK, here's my current thinking (this is per speaker, btw):

Vifa DX25TG05-04 ,Vifa D26NC55 or Dayton Neo tweeter
4 Dayton RS52s with two rear-firing for dipole configuration
2 Dayton RS225-04s (in series) dipole
2 Dayton RSS390s in dipole (w frame or 'ripole')

I'm not sure where the crossover frequencies will fall out at this point, but that's OK - as long as good ones can be attained with the drivers.

Efficiency may be below my target, but perhaps not by much.

I also think I'll get another higher power amp for the subs, use the Stax on the RS225s and the ZV9s for the RS52s and the tweeters. Maybe I should go digital on the sub amp to make up for the inefficiency of the class A amps.

It will be more money than I expected, but that should be OK. It will just take longer to save up the delta.

Thanks, everyone.

[Mazeroth]

Seas 27TDFC (1.6khz & up)
1 Dayton RS150 (450-1.6khz)
2 Dayton RS225s (100-450hz)
2 Dayton RSS390s in dipole (w frame or 'ripole') (80-100 hz)

Call it a day.

Something else you're forgetting is the enormous amount of EQ you're going to need and what that's going to do to your low-powered amps. Your high-efficiency requirement is KILLING the speaker you're designing.

[Landroval]

OK, here's my current thinking (this is per speaker, btw):

Vifa DX25TG05-04 ,Vifa D26NC55 or Dayton Neo tweeter
4 Dayton RS52s with two rear-firing for dipole configuration
2 Dayton RS225-04s (in series) dipole
2 Dayton RSS390s in dipole (w frame or 'ripole')

I dont see the point in using 4 RS52. You will be limited to the same efficiency as you would be with only one front firing RS52, because I doubt you can wire all in parallel. If you want dipole upper midrange and lower treble just go with a cone instead of a dome.

And the RS225-4 is more like 88-90dB, so I would say you're better off with two RS225-8 in parallel.

[Paul Ebert]

Yeah, after I wrote that I started thinking that I should just go with a cone - one can buy a pretty good midrange for the cost of 4 RS52s. For some reason, I like the idea of a dome midrange. Not sure why.

Perhaps the Audax PR170M0?

I'll check the graphs for the RS225-8 and the -4 over the range of interest. You may very well be correct.

Thanks.

[cjd]

It really seems like you're taking infinite baffle SPL response and assuming that's going to be exactly what you get when you go dipole.

It isn't so. It isn't even what you get monopole. Only infinite baffle.

C

[Paul Ebert]

You're probably right. Can you educate me, please?

[Landroval]

Umm, yes.. For the RS225 or whatever is taking care of the lower midrange the efficiency is much less if you have to use some of it for dipole bass roll-off compensation. This of course depends on the baffle size and form. E.g. with a 20" wide baffle you can go as low as 300-400Hz and not lose any efficiency because of OB roll-off.

[Paul Ebert]

I do understand about the dipole roll-off. Is there anything else?

Still researching midrange options...