disappointing lower midrange performance from woofers, why do people cross high?

[thadman]

I became aware of some testing Zaph did regarding the RSS315HF and RS270. I was surprised to say the least, the distortion looked pretty bad. The RSS315HFs 3rd harmonic levels reach .3% at 200hz (wasn't measured beyond this) and the RS270 maintained .3% 3rd harmonic levels from 200-500hz and ~.4% 2nd harmonic levels from 350hz-->500hz. It doesn't look like they (although possessing a much greater amount of displacement) can swing with the the midranges Zaph measured. Although appearing bad, I'm not sure what to make of it since Zaph, other than leaving us some context clues, doesnt appear to list the SPL he measured them at. Are they measured at the 96dB @ 1/2m that the 6.5s were measured at or something else?

Zaph mentions that the RS270 was reaching ~2/3 xmax around 100hz, so I plugged the figures into spl_max1 (330cm^2, 4.4mm xmax, 100hz) and got 106dB. If we account for baffle step, thats roughly 100dB. Is this about right?

I'm not sure if Zaph likes people borrowing the pictures from his blog (so to be courteous I saved them on my computer and hosted them myself).

RSS315HF


RS270


(FYI I plan to use these drivers in a dipole alignment)
I have been under the impression that a high displacement midbass/lower midrange driver crossing to a midrange around 300hz was the way to go...have I been misled or interpreting information incorrectly? Would a multitude of RS225s (say 4/panel) crossed around 100hz to a deep h-frame/w-frame be a better option than taking the subwoofers (specifically RSS390HF) up to the midrange crossover point on a flat baffle? The RS270 doesnt seem to measure all that impressively either, is it truly one of the best midbass drivers when crossed ~500hz, or is it bested by its smaller brothers the RS225/RS180 when used in pairs costing the same $$$?

[cotdt]

I agree, but I think that the energy storage problem at higher frequencies is worse than the rising harmonic distortion.

[thadman]

I agree, but I think that the energy storage problem at higher frequencies is worse than the rising harmonic distortion.

How bad is the energy storage problem? I havent seen any charts that I could compare with other familiar drivers in this passband. How can people recommend these drivers if their performance is so poor compared to other drivers?

[Dennis H]

How can people recommend these drivers if their performance is so poor compared to other drivers?

Because it's not. If you go to Zaph's tidbits section, he compared the RS315 to a $700 Skanning and there wasn't much difference. He's measuring the small drivers at much lower SPL so they look better on paper. Apples and oranges.

[thadman]

Because it's not. If you go to Zaph's tidbits section, he compared the RS315 to a $700 Skanning and there wasn't much difference. He's measuring the small drivers at much lower SPL so they look better on paper. Apples and oranges.

I wasnt debating whether the RSS315HF was an excellent driver or not (indeed it is). My question was actually why do people recommend these "subwoofer drivers" up high when they produce higher levels of distortion than an 8".

[Chris7]

My question was actually why do people recommend these "subwoofer drivers" up high when they produce higher levels of distortion than an 8".

Because unless you're going to build a 4-way, it's very hard to cross an 8" driver over to a tweeter while still maintaining a reasonable power response.

[thadman]

Because unless you're going to build a 4-way, it's very hard to cross an 8" driver over to a tweeter while still maintaining a reasonable power response.

I'm sorry, I shouldn't be so ambiguous in my posts. I was talking about using >pair of 8s as dedicated midbasses to replace the subwoofer/woofers in that passband. A midrange would lie in between.

[Dennis H]

My question was actually why do people recommend these "subwoofer drivers" up high when they produce higher levels of distortion than an 8".

1. I don't recall anyone (other than you) recommending them "up high." Got a link?

2. You are ASSUMING they produce higher levels of distortion than an 8" at equal SPL levels. I've seen no evidence to support that assumption. Zaph tested the big drivers at a much higher SPL than his little driver tests.

[thadman]

1. I don't recall anyone (other than you) recommending them "up high." Got a link?

Yes, the RSS315HF was recommended up to 300hz and up to 1000hz if you weren't too picky. The RS270 was also highly recommended up to 600hz.

http://www.mfk-projects.com/rs_12_hi-fi.htm

Anyway, one amazing thing about this woofer is its ability to perform well up to several hundred Hz. This is a little unusual for this kind of heavy high excursion driver. I guess if you are not too critical you could use this driver to 1Khz but personally I wouldn't use any 12" driver that high except in certain pro-audio applications. I would feel very comfortable however using this driver to 300 Hz. In most of the applications I have planned for it I will not use it above about 140 Hz but that is more because this is what the application calls for rather than any concern with using this driver higher in frequency.

http://www.mfk-projects.com/dayton_rs.htm

This is a pretty nice 10" driver. Both the non-linear distortion and the stored energy are very reasonable as long as you use it in an appropriate frequency range for a 10". Note that at 1200 Hz the stored energy is pretty bad. At 1400 Hz I included the data so you can see the tone burst continuing to ring. I really would not suggest using this driver even close to this frequency. I would say about 600 Hz is more than high enough to cross-over to what ever midrange you would use with this. This is definitely not a driver you would use in a two way but then what 10" would you use. For 600 Hz down this should be a great performer.

The Ciare 18.00NdW1 was also recommended up to 300hz on a flat baffle, along with the Aurasound drivers.

2. You are ASSUMING they produce higher levels of distortion than an 8" at equal SPL levels. I've seen no evidence to support that assumption. Zaph tested the big drivers at a much higher SPL than his little driver tests.

I specifically stated I wasn't sure what specific SPL/specific parameters the drivers were measured at. I was also suggesting using multiple smaller drivers to make up for the difference in surface area (2 RS225s vs 1 RS270), not an outright swap.

[AJINFLA]

So have you built your first loudspeaker yet? How long will this whole virgin anxiety thing last?
C'mon man, just get it over with. Build one. Trust all of us here, it won't be your last.

cheers,

AJ

[cjd]

I'm curious, what are you comparing to?

[JonP]

For Zaph's graphs (hey, new site name suggestion! Shades of "Blue's News") or anyone's graphs for that matter to compare with one another is a difficult thing.

As has been pointed out, you really need to have the same levels and as much of the other conditions the same as possible, for a meaningful comparison. I'm not an expert, but I think it also gets much harder to get clean and decent measurements below 100Hz or so.

Either you or someone needs to do that dual 8" vs RSS 12" comparison. I'd be very interested in that and similar tests, because your question is a good one, and AFAIK, nobody's done anything like that comparing large woofer distortion performance.

I'd also like to see more power scaled testing, as in the same driver at 85, 95, 105dB... to see how the distortion products come up with increasing volume. Mark K has done these. It is a pain to have to do a huge panel of tests, and I don't blame our generous guys who publish all this test data for not spending weeks on each driver. But, on a few "high interest" drivers it would be nice to have a power/distortion run added to the body of knowledge out there.

[WillyD]

thad - First off, I believe Dennis was referring to anyone here recommending such, not MK.

Secondly, even in those quotes you provided MK says this:

I guess if you are not too critical you could use this driver to 1Khz but personally I wouldn't use any 12" driver that high except in certain pro-audio applications. I would feel very comfortable however using this driver to 300 Hz.

[thadman]

thad - First off, I believe Dennis was referring to anyone here recommending such, not MK.

Secondly, even in those quotes you provided MK says this:

Anyway, one amazing thing about this woofer is its ability to perform well up to several hundred Hz. This is a little unusual for this kind of heavy high excursion driver. I guess if you are not too critical you could use this driver to 1Khz but personally I wouldn't use any 12" driver that high except in certain pro-audio applications. I would feel very comfortable however using this driver to 300 Hz. In most of the applications I have planned for it I will not use it above about 140 Hz but that is more because this is what the application calls for rather than any concern with using this driver higher in frequency.

Whats your point? I've concluded from this statement that he believes most woofers should never be taken beyond the traditional passband, but that the Dayton RS is an exception. It can be taken comfortably up to 300hz.

[Dennis H]

Whats your point?

I've been wondering that about this whole thread. Thad, you seem to think .3% distortion at 100+ dB is bad. Seems pretty good to me for a single driver. Obviously distortion goes down if you play it quieter or use multiple drivers. Keep in mind that any driver driven to Xmax is likely to have 10% distortion.

[Rick Craig]

I've been wondering that about this whole thread. Thad, you seem to think .3% distortion at 100+ dB is bad. Seems pretty good to me for a single driver. Obviously distortion goes down if you play it quieter or use multiple drivers. Keep in mind that any driver driven to Xmax is likely to have 10% distortion.

Drivers can also be excursion-limited by motor and / or suspension issues. This was the case with some RS drivers recently tested in Voice Coil.

[joecarrow]

I believe this has been said, but all of this design work is an exercise in trade-offs. The graphs you show do indicate that there will be some audible distortion, but it's a rare and expensive thing indeed to play at 100 db without much distortion.

One advantage the RSS subwoofer has is that it has a fairly wide-open basket structure and low turbulence noise at high excursion. Compared to many drivers they're a good pick for dipole use.

Some comparison the the Linkwitz Orion is inevitable for a project such as the one you've set out on, and I think fairly healthy. To compare the woofers, the Peerless XLS woofer used in the Orion has nowhere near the performance of the Dayton Reference above 200 hz. They have higher inductance and less well behaved cones. They are successfully crossed to an 8" midrange at about 120 hz. This is a fairly large midrange, and it crosses to the tweeter at 1400 hz, 4th order.

The choice of Excel midrange drives the whole system. It can't play any higher because it runs into cone breakup. If a smaller mid was chosen to allow an easier crossover to the tweeter, then the woofer wouldn't be able to play cleanly high enough. It's a balancing act, and one of the tradeoffs is that the Excel mid operates high enough in frequency that distortion products excite cone resonances. This is measurable, and with the right signal it can probably be audibly demonstrated.

The bottom line is that all drivers have strengths and weaknesses, and the best thing you can really do is make sure that there's not an excessively weak link in the chain.

[cotdt]

for once i have to agree with AJINFLA

[Doug Lockwood]

I believe this has been said, but all of this design work is an exercise in trade-offs.

Very true, Joe.
I am running a pair of RS270 per side OB on a 46" by 18" flat baffle crossed at 200 to 500 Hz (depending on day of week) to a 14cm seas mid-range. The trade-off I see is a lower crossover point requires more excursion of the mid-range, and because of the pass-band, has higher IM in the critical mid-range.
On the other hand, I can't tell the difference, so I set the XO at 320 LR4 and called it a day.

The RS270 does work very well OB.

By the way, I agree with AJ as well. Pay your Money, and take your choice. :T

HTH

Doug

[joecarrow]

Seriously, unless a grievous error is made during setup, this is going to sound worlds better than the Modula MT (the one that I built), which IMO competes with and generally beats anything commercial that I've heard for $1000 or less.

This is already going to be "holy cow, this is great!" level of performance. If you want to get to "I can't honestly find anything better", then it by nature must become an iterative process, with incremental improvements through trial and error. Getting there won't be possible without your own measurements, your own trial and error, and your own ears to tell you which distortion and response measurements really matter to you. You trade one unfavorable artifact for another; if one annoys you and the other one is mostly is washed out by room interactions, you might not know which is which and what's more important until you get the whole system built in your room.

I'm glad I didn't build something far more expensive, like the Modula MTM, because I learned that my room layout just doesn't support hi-fi sound. I'm going to need to get a bigger room and lay it out properly before I can get any kind of imaging.

[thadman]

Although the response curve of this driver looks great (1st peak lies around 1700hz, placing the 3rd harmonic around 566hz) the impedance is pretty troubling. It looks pretty crazy, how bad should the energy storage be on this driver be?

[joecarrow]

I'm less worried by that sweep than I think you are. If you look, the blip at 1.5 khz in impedance matches the one in phase. This is a pretty strong indication that something is going on there. If you look at the small spiks from 20 hz to 100 hz, the impedance wiggles don't really line up with phase irregularities. This, to me, just looks like a high resolution, unsmoothed plot. Even a small amount of smoothing would even those bumps right out, and it would look more like the majority of published (by manufacturers) impedance curves.

[thadman]

The RSS315HF (the one measured by Mark K) doesnt exhibit such severe blips.

[JonMarsh]

If you're talking about the "noise" in the plots of the 390 below 100 Hz, that's probably just a lack of care in running the test as regards the CLIO signal level set in the generator, and the fact that a speaker is also a microphone and will pick up ambient disturbances. Look at the differences between Tangband's published 1337S curve and mine- the latter is much cleaner because of better measurement setup.

~Jon

[thadman]

How much performance am I sacrificing (300hz xo point) by going with the RSS390HFs over the aurasounds? The Daytons provide much more displacement (2)860(1.4)=2408cm^2 vs 2(503)(1)=1006 and are significantly less (I can get them for $125 shipped/each) vs $184+s/h for the aurasounds.

[JonMarsh]

You would really have to measure both drivers at a number of power/SPL levels to determine that (and it wouldn't be a bad idea to listen, either. BOTH are above average for this application due to their open rear baskets and vents, and lots of copper in the gap. Unquestionably the 390's are a bang for the buck champ- it's my recommendation for a lower cost Isiris, due to good distortion vs level behavior, good midrange distortion for a 15", and 4 ohms which helps the sensitivity in relation to the cone mass.

The NS12-513A is an exceptional "woofer" in my opinion, as the underhung motor has pretty good travel, and the distortion proudcts steadily fall above 100 Hz; at levels like 100 dB, 2nd order is 10 dB lower 700 Hz than 100 Hz, and 3rd order is 8 dB lower, which you'd expect if inductive impedance rise is well controlled and actual excursion was the main nonlinearity generator. But a single 15 like the 390 is giving very good performance for the money. Realistically, if you want low distortion at 100 dB+ levels, perhaps you should be thinking about more drivers - but do you really need 110 dB? I think that capability is good, but only because the drivers are more in a coasting mode at normal 90-100 dB playback- which is still loud by usual home playback standards. If you need more, and need it clean up to severeal hundred Hz, there's always the NRT18-8. I wouldn't normally recommend an 18" to 300 Hz, but these will do it with 96 dB sensitivity for 2.83V, with ~14 mm linear Xmax. Depending on how the testing on the Ciare's turn out, I may pop for a pair in mid June after I get back from my overseas business travel. Limiting factor on these may be the pole vent, whether it's noisy or not.

BTW, something to consider, the Neo based drivers generally weigh a lot less, though this one isn't light at 29 lb - about the same as an RS390, though obviously quite a bit less than two of them.

Jon

[JonP]

How much performance am I sacrificing (300hz xo point) by going with the RSS390HFs over the aurasounds? The Daytons provide much more displacement (2)860(1.4)=2408cm^2 vs 2(503)(1)=1006 and are significantly less (I can get them for $125 shipped/each) vs $184+s/h for the aurasounds.

Another minor point which may be obvious, but I thought I'd mention it... a larger Xmax / greater displacement, should mean the driver will have less work to make the same volume. And, if other things are equal, (which probably isn't the case) that should result in lower distortion.

I agree about these drivers are very good for subs... kind of wonder what more "normal" subs would look like in comparison to the RS line. Probably a lot worse.

[joecarrow]

"Normal" subs, such as the Dayton Titanic MKIII, the Peerless XLS 83500 are definitely not usable as high as the Reference series subs. Check out the response for the Peerless:

http://www.partsexpress.com/pdf/297-608.pdf

It completely falls apart by 500 hz. This is the sub used in the Orion, and even if cavity resonances from the H-frame weren't an issue then I don't think you'd want to take this thing up very much past the 120 hz crossover used.

Sure, as you pass 200 hz the performance of the sub isn't as good as the performance of a smaller midwoofer, but the point is that the output to 200 to 400 hz is quite usable and gives you some flexibility to cross to something that doesn't need to reach down below 100 hz. You sacrifice amazing performance from 200-400 hz, but gain the ability to use a mid that gives outstanding performance across the majority of the vocal range.

There are a million ways to go about it, but I think that they fill a good niche. Ask Kingpin what he thinks; he's got the RSS315s in a cabinet with RS270s. He has an active crossover that lets him pick where they cross, letting the subs run really high if he wants. I don't know if he's experimented with it as much as I would (I love to play), but he's got the stuff to tell you if the subs have noticeably bad sound at a certain frequency crossover.

[mikec]

http://www.partsexpress.com/pdf/297-608.pdf

It completely falls apart by 500 hz. This is the sub used in the Orion, and even if cavity resonances from the H-frame weren't an issue then I don't think you'd want to take this thing up very much past the 120 hz crossover used.

Last time I checked the Orion used 10" woofers. http://www.partsexpress.com/pdf/297-604.pdf

Some comparison the the Linkwitz Orion is inevitable...

Perhaps you should become more familiar with SL's designs before critiquing them. :roll:

[Davey]

for once i have to agree with AJINFLA

That's ok, you know.

Davey.

[joecarrow]

Last time I checked the Orion used 10" woofers. http://www.partsexpress.com/pdf/297-604.pdf


Perhaps you should become more familiar with SL's designs before critiquing them. :roll:

I think I'm fairly familiar with them. Yes, the "standard" orion uses the 830452, but I believe that somewhere on his site he mentions that you're free, with a few minor tweaks, to use the 830500 as an alternative for increased bass output. He definitely lists that woofer as an alternate for the Phoenix:

http://www.linkwitzlab.com/woofer3.htm

I'm definitely feeling a bit sheepish at saying the 12" version was the default. Really though, does that change much for the topic at hand? I really don't think I was critiquing any of Linkwitz's designs in any of this.

[mikec]

I think I'm fairly familiar with them. Yes, the "standard" orion uses the 830452, but I believe that somewhere on his site he mentions that you're free, with a few minor tweaks, to use the 830500 as an alternative for increased bass output. He definitely lists that woofer as an alternate for the Phoenix:

http://www.linkwitzlab.com/woofer3.htm

I'm definitely feeling a bit sheepish at saying the 12" version was the default. Really though, does that change much for the topic at hand? I really don't think I was critiquing any of Linkwitz's designs in any of this.

There is only one woofer "recommendation" for the Orion and it's the 10" XLS that I linked to. SL does recommend the 830500 for the (Phoenix) W-frame woofer since the original Gefco is no longer available. He also uses it in the Thor subwoofers, which are a sealed box design.

As to SL choice of drivers used in the Orion; here is that link: http://www.linkwitzlab.com/orion-faq.htm#Q6

[joecarrow]

Thanks for setting me straight- it had been a couple of years since I spent a considerable amount time at his site. I'll try to be more careful describing specific designs in the future so that I do not mislead people.

[kingpin]

Thanks for setting me straight- it had been a couple of years since I spent a considerable amount time at his site. I'll try to be more careful describing specific designs in the future so that I do not mislead people.

It's o.k. Joe.
We all mess up sometimes. At least you can man up to it. :T

There are a million ways to go about it, but I think that they fill a good niche. Ask Kingpin what he thinks; he's got the RSS315s in a cabinet with RS270s. He has an active crossover that lets him pick where they cross, letting the subs run really high if he wants. I don't know if he's experimented with it as much as I would (I love to play), but he's got the stuff to tell you if the subs have noticeably bad sound at a certain frequency crossover.

I have 2 of these in each tower(top 2 drivers in my avatar).
I have played around with the crossover settings on the cx2310 and usually have the subs crossed over anywhere between 60- 90hz depending on what I am playing. I am constantly playing around with the crossover trying different things.

I asked Chris(cjd) about the crossover settings and he made sense when he mentioned that crossing them over higher than 80-90hz would be taking too much away from the rs270's. I seem to agree with this conclusion.

Mike

BTW. The RS12" subs are a pleasure to listen to.
BTWW. Sarah McLaughlin's song "Back Door Man" from her album Solace has some heavy bass at the beginning of the song. First time I played it I thought the cone was gonna fly across the room.

[AJINFLA]

Actually it was me who recommended using the XLS12 when building "Orions". I can see where I could easily be confused for SL.

cheers,

AJ

[joecarrow]

You're not the one with the orion-like dipole built with a waveguide on an acrylic baffle, are you? I never got to read about that particular design in detail, but it seemed like a good idea from what I could tell.

[AJINFLA]

Yes, that was me. There is no tongue in cheek emoticon, or else I would have included it in my last post for those who might not see the obvious.

cheers,

AJ