RSS315HF-8 - Is Passive Worth Trying?

[villastrangiato]

I'm building a three way using the RS180's and a pair of NEO 3's, and an RSS315HF-8 in a modified D'Appolito array. This is for my parents - my father is a total bass nut .....Anyhooo....I haven't seen any projects on here that go passive with the Dayton sub - just wondering if it's really worth the effort or if a plate amp is the only way to go. I realize all the inherent advantages of going active with the 315 - but it would be nice to avoid the extra $500 or so in plate amps... We have a beefy power amp for him to use - so that's not an issue if the sensitivity and dynamics are workable. Any thoughts?

[JonMarsh]

Well, I'm probably the resident nut case for passive crossovers, so not the best person to query on this- the 315 has pretty fair HD out to 300 Hz+, so a passive crossover at a reaonable frequency is not a problem- but- considering the likely frequencies for going passive, a more midrange oriented driver with a more extended, cleaner top, might be worthwhile.

Don't move the lower crossover frequency down too low, or you may need to spend more money than you want on LF zobels to get the crossover to behave properly.

[villastrangiato]

Well, I'm probably the resident nut case for passive crossovers, so not the best person to query on this- the 315 has pretty fair HD out to 300 Hz+, so a passive crossover at a reaonable frequency is not a problem- but- considering the likely frequencies for going passive, a more midrange oriented driver with a more extended, cleaner top, might be worthwhile.

Don't move the lower crossover frequency down too low, or you may need to spend more money than you want on LF zobels to get the crossover to behave properly.

"Resident nut case" - yeah, right Jon - your modesty is only matched by your crossover wizardry....This is actually a very different perspective than what I had expected you'd present. I know the 315 with it's 'Dark Side' looking aluminum cone is really clean way up beyond where anyone should think it has a right to be - but my plans were to run the RS180's down "full range" - possibly with fairly short TL's - partly to satisfy my own curiosity as to what they're capable of with that kind of loading and partly for flexibility in what I'd want to get out of the sub. I also wanted to build in the maximum flexibility for adjusting baffle width to suit the planars - as we all know how sensitive they can be in that regard (Dan's experience with a little peak at around 1.8khz comes to mind). So right from the get go, I was planning on a low cross to the sub - placing it on the side of the enclosure ala Andy Payor's Arrakis. The thing that most intrigues me about turning this into a little test bed however is the orientation of the planars. I was thinking of getting them exactly half way between the sitting and standing height - with the lower planar/RS 180 pairing pointed upward at a 6 foot position at an approximately 10 foot listening distance and the upper driver pair pointed downward at the 38 inch level. I figured if I get the NEO's as close as possible to one another - the modest angle between them should not present any serious issues - they would effectively have very little interference in the "mixing region" between 36 inches and 72 inches in target height. And theoretically, because of their highly limited vertical dispersion, the angling should serve to mitigate interference at listening positions in close proximity to the baffle either well above 54 inch center height distance or well below it. Do you know if anyone has done anything like this - or am I really playing with polar response fire here?

And, I already have four RS180's kicking around, hence with a steep cross at around 1200hz - I might have effectively the same performance as I'd get with a more midrange oriented driver - with the added bonus of a closer approximation to a point source integration given the low crossover point. Let's face it, Jon - I'm sure I'm not the only one who's "seen the light" as a result of your Modula project. People should start to place a value on tweeters and mids that cross low - the benefits are many. Trust me, I'd rather be using that nifty 18Sound midrange Krutke tested - but I already have the RS180's and I'm trying to keep the budget overall in the "obtanium" category.

[Undefinition]

I was considering that as a bass in a large 3-way at one time. It models very well. If I remember correctly, it has an F3 in the 30 Hz range, sealed. Vented, the sky's the limit (or the subterranean depths, depending on your tastes).

Mating the RS180 with the Neo3 requires some real crossover finesse.
Not sure why you'd use a pair of Neo3. The round flange on those things is HUGE, by the way.
Why a TL on the mids?

[villastrangiato]

I was considering that as a bass in a large 3-way at one time. It models very well. If I remember correctly, it has an F3 in the 30 Hz range, sealed. Vented, the sky's the limit (or the subterranean depths, depending on your tastes).

Mating the RS180 with the Neo3 requires some real crossover finesse.
Not sure why you'd use a pair of Neo3. The round flange on those things is HUGE, by the way.
Why a TL on the mids?

The reasons for using the NEO 3's as a pair are two fold (aayyyy - no pun intended). Firstly, I have a bunch of them....lol.... Second, the goal is to run them down fairly low - lower than Jon crossed the RS180's to the Seas 27 or Dayton Rs28 ( 1400hz). There are very, very few inexpensive tweeters that run clean in the range of 1 - 1.5khz - the NEO 3's do well in that regard. However, they are not recommended for operation in that frequency range as single units. If run as a pair, and with a shallow damped enclosure, the rolloff from 2khz can be dealt with and the power/distortion issue at around 1100 - 1200 hz should, in theory anyway, be tamable. There are other implications as well - they have a very easy to work with 3.5 ohm load - so a series pair should be a crossover designer's dream - if you can avoid low end response raggedness. The high vertical directivity of a single NEO 3 would represent a significant disadvantage versus a SEAS 27TDFC or Millenium or the Dayton. But two of them could potentially represent a low frequency power handling improvement (emphasis on could). Plus, it might establish new ways of using these "line array" drivers for folks who want to use them in a "point source" implementation. Do I sound like a BG radia salesman ? ....ugh....

And I wouldn't be using the round flange - they would be flush mounted from outside ( with slight recess) and the area around them would be covered in felt that's velcro'd into a slight recess - thus managing the transition from driver to baffle acoustically while keeping things "clean" where the ugly BG mounting situation is concerned. Someone should tell them they need to improve the mounting flange - PITA! :smackbutt:

[JonMarsh]

"Resident nut case" - yeah, right Jon - your modesty is only matched by your crossover wizardry....This is actually a very different perspective than what I had expected you'd present. I know the 315 with it's 'Dark Side' looking aluminum cone is really clean way up beyond where anyone should think it has a right to be - but my plans were to run the RS180's down "full range" - possibly with fairly short TL's - partly to satisfy my own curiosity as to what they're capable of with that kind of loading and partly for flexibility in what I'd want to get out of the sub. I also wanted to build in the maximum flexibility for adjusting baffle width to suit the planars - as we all know how sensitive they can be in that regard (Dan's experience with a little peak at around 1.8khz comes to mind). So right from the get go, I was planning on a low cross to the sub - placing it on the side of the enclosure ala Andy Payor's Arrakis. The thing that most intrigues me about turning this into a little test bed however is the orientation of the planars. I was thinking of getting them exactly half way between the sitting and standing height - with the lower planar/RS 180 pairing pointed upward at a 6 foot position at an approximately 10 foot listening distance and the upper driver pair pointed downward at the 38 inch level. I figured if I get the NEO's as close as possible to one another - the modest angle between them should not present any serious issues - they would effectively have very little interference in the "mixing region" between 36 inches and 72 inches in target height. And theoretically, because of their highly limited vertical dispersion, the angling should serve to mitigate interference at listening positions in close proximity to the baffle either well above 54 inch center height distance or well below it. Do you know if anyone has done anything like this - or am I really playing with polar response fire here?

And, I already have four RS180's kicking around, hence with a steep cross at around 1200hz - I might have effectively the same performance as I'd get with a more midrange oriented driver - with the added bonus of a closer approximation to a point source integration given the low crossover point. Let's face it, Jon - I'm sure I'm not the only one who's "seen the light" as a result of your Modula project. People should start to place a value on tweeters and mids that cross low - the benefits are many. Trust me, I'd rather be using that nifty 18Sound midrange Krutke tested - but I already have the RS180's and I'm trying to keep the budget overall in the "obtanium" category.

I understand that budget issues can dictate drivers to use and operating range- in that case, if the system resembles a two way with a built in sub, with regards to LF crossover, I'd recommend going active. If you think you'll be happy crossing at 250 or so, then passive might be OK- I'd suggest doing a design study after you finish measurmenets, see what it would cost you in passive crossover parts versus all active. I've been doing some lower frequency crossover points, but have been spending ~$45 per inductor at that point, and sometimes needed to do woofer zobles to control mid bass bump on the low pass (typically in the 150 Hz region) due to interaction with the woofer's changing impedance. With a 12" sub driver instead of 7" midbass, it may not be as pronounced, but I would suggest design study before making a decision.

[villastrangiato]

Right now, leaning in the direction of a plate amp - lazy, I guess. I haven't made a final decision on the TL loading of the RS180's - I know simple vented will do the job especially in conjunction with an active sub - but I have to have something to play around with beyond jamming a couple flat tweeters together..... :W

The 500W Dayton and Bash Amps look like an incredible buy. I expected there was a good reason very few people were posting passive Dayton 315HF projects on here - your point about the zobels is well taken - inductors would probably rival the cost of the amps in the final analysis.

[Undefinition]

The 500W Dayton and Bash Amps look like an incredible buy. I expected there was a good reason very few people were posting passive Dayton 315HF projects on here - your point about the zobels is well taken - inductors would probably rival the cost of the amps in the final analysis.

I still don't understand why you're doing a TL on mids. For that matter, venting them or sealing them, it doesn't matter because the frequencies affected by the enclosure are out of the passband.

Also, most zobels are just a resistor and a capacitor. not sure where inductors come into play.

[villastrangiato]

I still don't understand why you're doing a TL on mids. For that matter, venting them or sealing them, it doesn't matter because the frequencies affected by the enclosure are out of the passband.

Also, most zobels are just a resistor and a capacitor. not sure where inductors come into play.

I'm a bit of a TL purist - maybe even a "TL snob"....lol.....

Check out Deward Hastings posts on a pretty heated thread between myself and Martin King. Deward said it better than I could - probably because he speaks from a longer held experience than I do. I've only been researching transmission line loading since 2003-2004. But to quickly summarize - it's not just improved frequency response that TL designs seek to achieve - it's a host of other improvements:

1) critical damping of driver resonances
2) improved power handling and transient response as a result of #1
3) improved efficiency - again a byproduct of #1
4) reduced backwave interference


A lot of newbies have invaded the TL space since 2000 - many of them appearing to cast aside lessons learned over literally decades of development in the previous half century. Linearity, proper effective damping over a wide range of frequencies, better dynamic accuracy - there are a lot of benefits to incorporating the time and resources to improve low frequency driver loading - low frequency extension is only one of them - and according to Deward - that wasn't even really a primary goal of the early designs - a very significant indication of how views have changed.

[dlneubec]

I can see the benefit of the TL on the woofers for things other than low end extention. Pete S. over at PE is considering doing that on his WWMT project with a closed end tapered TL on the mid.

I've been very happy with the inexpensive Dayton SA240 plate amp. I'm only using it at less than half gain and it goes plenty loud with just a single RSS265HF in a tapered TL. It has a built in high pass, BW2, IIRC, centered at 18hz for some low end protection. BTW, you can model this HP as well as the low pass, parametric EQ, etc. in Jeff B.'s Woofer Box and Circuit Designer. The variable active crossover on the Sa240 goes from 40-180hz and is 4th order, which it atypical for a plate amp. It also has a sealed back, though I still put mine in a sealed off section. It's also on special for $109 right now, which is great bang for the buck.

You might try testing the Neo3 in a shallow waeguide, perhaps 1/2" to 3/4" deep with a 1/2" or 3/4" roundover and a rear mounting. I think that could help fill in the response between 1.8khz and 8khz and also give it 4-5db boost probably centered around 3khz or so, but extending lower as well. This could give you more low end capability. I agree that using this tweeter, even in pairs, with that low a crossover will be a major challenge. Good luck!

[cjd]

Few things:

The main reason to avoid this: sensitivity mismatch. i think.

My big towers would house the old 12" RS subs, sealed, perfectly. And they'd cross just fine if I hit the same target slopes. (currently RS270S-8x2 in parallel, RS180S-8x2 in series, RS28A-4) But sensitivity didn't allow for it (4ohm meant no parllel, series not enough sensitivity...) - if you can get the sensitivity matching, go full 3-way and enjoy. Should be a great combo. I didn't know they had an 8ohm version of the sub... or is my memory just gone already?

TL on the RS180 gets big.

I swear half the reason so many TL's are given such high marks have nothing so much to do with them being TL as with the designer actually giving the driver as much box volume as it wants. Almost every ported or sealed design out there goes too small.

[JonMarsh]

Few things:

The main reason to avoid this: sensitivity mismatch. i think.



I swear half the reason so many TL's are given such high marks have nothing so much to do with them being TL as with the designer actually giving the driver as much box volume as it wants. Almost every ported or sealed design out there goes too small.

Hear hear!!

Many routes to nirvana, though....

[villastrangiato]

Really good, insightful suggestions guys. The RSS315HF is the 8 ohm version - I bought those with the anticipation of having low impedance issues in the crossover region between RS180 and the sub. Most folks are smarter and go with the 4 ohm version - active. Me thinking I had all the answers, decided to sacrifice with higher LE and lower sensitivity in going with the 8 ohm version to show myself I could hammer out a passive version - but with the more attractive plate amp solution (which all the normal smart people seem to have figured out already) the 4 ohm choice becomes the no brainer.

Glad to hear about the Dayton 240 Dan. Looking at PE's site, it didn't look like it came with crossover adjustabiility like the more expensive 500W version. And it fits in the budget really well- will definitely put the order in tomorrow. :T

Yeah Dan, crossing the Neos 3 down around 1khz is going to be a challenge - not sure if being able to alter baffle width will be a powerful tool in heading off peaks like the one you experienced. You find a frequency that's causing trouble - tone down or up the baffle width to compensate - and wind up with another dip somewhere else. Maybe the shallow guide idea will bear some fruit. Thanks.


Either way, as far as the tweeters are concerned, I'm looking at this as more of a test mule. If the polar response winds up totally cluster&^%$'d - no big deal - I doubt my dad would ever no the difference - his hearing isn't what it used to be. :B This is sort of the ideal fun project - absolutely no PRESSHA!!

And thanks for the inspiring words on the TL aspect Cj - I think with the total budget now on this thing hovering around a grand - it makes sense to go the extra mile and see just what these little 7's are capable of. I have to say, when I first heard them out of the box, they really impressed me against the usher's and revelators I've used over the years.

[cjd]

They go deep better than they go high. Not my favorite for upper midrange. (damn, that's what I use as a mid in my mains...)

You can still make up some of the sensitivity difference bi-amping. But I'd not use a plate amp if you want to cross particularly high.

I'd build them as separate projects in all honesty. I think you'll be tickled with the RS180 in a TL, and I suppose if you want to run a sub you can, just have it... well.... separate. Or go 4-way. Snag a couple Neo8's...

[villastrangiato]

These four RS180's are the first set I've bought - they've been sitting around for a while and so I really want to use them - they aren't doing any good on the shelf. A few months back I hooked them up to an old Bryston - also collecting dust - slapped one of my kids' CD's with a super maxxed out ridiculous bass line (I think it was Gwen Stefani's 'Fifth Gear") into the changer. I was really shocked at how well they stood up to some larger Ushers I'm using for a new TL bass module I'm building. In looking at distortion numbers, I think I'll probably cross to the 315's at around 75 hz with the plate amp - the external level control should come in really handy in matching levels if I decide to run further down or closer to 120 hz - but I don't see a reason for going that high. Looking closely at Krutke's comparison of 7 inch drivers - the RS180's are an amazing value - really giving nothing up to the Scans, Seas, or Audio Tech's from 75hz up to 1500hz. And I'm itching to get an opportunity to try my hand at my first elliptical crossover. :B

I have plenty of NEO 8 's btw, but they're for my "top secret Death Star" project 8) . That project is going to require a lot of machining work on my father's lathe and Bridgeport - so this current speaker is kind of an important stage in the "buttering up" process. I have very little lathe experience so I need to drag out the old man to show me how its done....