Questions regarding 80 Hz and below for music

[Paul Ebert]

I've been rethinking my approach to bass in the speaker I am designing. For above 80 Hz or so, I'm planning on a three-way using the ubiquitous D26NC55, RS52, and dual RS180S-8s. For bass duties, I was planning on something like a TC-1000 15" or the RS390. The crossover between the RS180s and the (sub)woofer would be active.

After reading John Krutke's article on lower xmax sounds better, I started reconsidering. Maybe I should go with dual RS270s. This would be for a music only system. I'm not a bass or loudness freak, but I do listen to classical music and want a solid orchestral foundation. I'd like a F3 no higher than 35 hz or so.

So, here are the questions...

Should I, in fact, go with a woofer rather than a sub? If so, are there any others I should consider besides the RS270?

If I go with a woofer, it seems that sealed is out. What about a passive radiator system? We don't seem to talk about them much. Is there a reason for this? If using a PR is viable, what is a good one, and how much does it matter?

Lastly (for now), I've been modeling various ported and PR systems in Unibox and I find that it is often hard to make the driver stay within its xmax. Is this a problem if the driver only exceeds its xmax for output levels above what I would listen to?

Thanks!

[cjd]

If you go with the RS270 you're almost talking about the 3-ways I designed. Highly recommended for orchestral works (and ideal for crossing to a sub at ~40-60Hz - say, a nice 4x15 or 4x18 driver IB sub). Most of my collection is classical. I listen without a sub - they'll actually hit 30Hz nicely in-room, but that octave down to 15Hz...

I've pondered whether I should do a 4-way with the RS52 in there. But were I re-working things I would seriously consider going with a pair of 12" like the RS315HF (a pair sealed still fit in the same box).

PR has worse group delay than a bandpass system with similar results otherwise.

C

[ted4412wilt]

The RS270 would be better than the RS180 but I would suggest the Peerless SLS 12" http://www.madisound.com/catalog/PDF...ess/830669.pdf
One will give you 84dB at 25Hz with 90dB straight line response from 65Hz to 1700Hz. Two would add 6dB. They are not really that expensive and will cost less than a quality sub.

[TacoD]

The Peerless SLS is a paper cone with a cheap basket. I would not used that woofer, if you don't need the SPL.

[cjd]

The RS270 would be better than the RS180 but I would suggest the Peerless SLS 12" http://www.madisound.com/catalog/PDF...ess/830669.pdf
One will give you 84dB at 25Hz with 90dB straight line response from 65Hz to 1700Hz. Two would add 6dB. They are not really that expensive and will cost less than a quality sub.

The RS270 + RS52 is a very tight fit. RS225 would be a better match in this case.

I agree with Taco on the Peerless...

[ted4412wilt]

Do you have a test showing higher distortion from the SLS 12" than some comparable driver with cast frame? When I was first looking at drivers I was impressed by things like Kevlar-carbon fiber cones but soon noticed that the results were not any better than paper. Aluminum cones are used because they are cheap but must be crossed well below their breakup. Peerless seems to get flatter frequency response than other companies. I am interested in the best sound per dollar. I have observed that larger cones have less distortion in the low frequencies. Small ones are fine for 1000Hz but not 40Hz.

[JonMarsh]

I've been rethinking my approach to bass in the speaker I am designing. For above 80 Hz or so, I'm planning on a three-way using the ubiquitous D26NC55, RS52, and dual RS180S-8s. For bass duties, I was planning on something like a TC-1000 15" or the RS390. The crossover between the RS180s and the (sub)woofer would be active.

After reading John Krutke's article on lower xmax sounds better, I started reconsidering. Maybe I should go with dual RS270s. This would be for a music only system. I'm not a bass or loudness freak, but I do listen to classical music and want a solid orchestral foundation. I'd like a F3 no higher than 35 hz or so.

So, here are the questions...

Should I, in fact, go with a woofer rather than a sub? If so, are there any others I should consider besides the RS270?

If I go with a woofer, it seems that sealed is out. What about a passive radiator system? We don't seem to talk about them much. Is there a reason for this? If using a PR is viable, what is a good one, and how much does it matter?

Lastly (for now), I've been modeling various ported and PR systems in Unibox and I find that it is often hard to make the driver stay within its xmax. Is this a problem if the driver only exceeds its xmax for output levels above what I would listen to?

Thanks!

Paul- this phrase/comparison about long throw versus short throw is coming up a lot this week- the problem with generalizations is that they lose a lot of the specifics and paint with a rather broad brush.

Is the RS390 or RS315 a long throw driver? Not compared with the big TC-Sounds guys. I think the real problem with many so called "long throw" drivers is Le, rising inductivity and distortion with frequency. Drivers engineered to circumvent that issue, like the RS subs, or the Aurasound NS10 and NS12, with a lot of copper in the gap, or underhung motor designs with copper in the gap (Aurasound), don't have the huge Le and Z min in the 70-80 Hz range like the "big dog" long throw subwoofers.

So, in conclusion, I wouldn't paint the RS subs or Aurasound "subwoofers" with the same brush as other woofers with more conventional designs or units like the long throw TC Sounds/Splinter sound drivers.

Just my 0.02.

~Jon

[Lazz]

So John do you think these woofers on a open baffle ala' BD Design Quasar wont work very well for sound quality wise.I listen to large orchestral to rock.

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'We want more' was the feedback from DIYers and Mach 5 listened. 'I Excel' was delivered and sums up the newest addition to the Mach 5 lineup ushering in a new beginning in high performance, high excursion drivers. The IXL-18.4 features a single 4 Ohm high temperature voice coil, heavy cast basket and massive bottomless motor. It has been designed to provide effortless bass in large enclosures and Infinite Baffle systems. Use the IXL-18.4 in a sealed configuration for you car, or a large Bass Reflex system for home theatre. Either way, the IXL will make you excel!
Power Handling: 800 watts RMS

Sensitivity: 89db (2.83 volts)

Impedance: 4 Ohm Nominal (SVC)

Dimensions

Outside Diameter: 46.2cm (18 3/16")

Mounting Diameter: 42.4cm (16 11/16")

Depth: 24.8cm (9 3/4")

Recommended Box Sizes

Sealed: 130 litres (4.6 cu. ft.)

Ported: 200 litres (7 cu. ft.) 19Hz tuning

EBS: 350 litres (12.4 cu. ft.) 15Hz tuning




T/S Parameters

Fs = 17.7 Hz

Re = 3.4 Ohms

Qes = 0.39

Qms = 5.59

Qts = 0.37

Mms = 434.3 grams

Rms = 8.69 kg/s

Cms = 0.184 mm/N

VAS = 274.1 litres

Sd = 1029.2 cm2

Xmax = 22 mm

Cone Diameter = 36.2 cm





or Fi Car Audio SSD18

DUAL 1 | DUAL 2

Fs: 24.7 Hz | 24.3 Hz
Re: 0.75 Ohms/coil | 1.5 Ohms/coil
Qms: 4.88 | 4.96
Qes: .75 | .69
Qts: .65 | .61
Mms: 296g | 308g
Cms: 0.14mm/N | 0.14mm/N
Sd: 1210cm^2 | 1210cm^2
Vas: 285 l | 285 l
Spl: 89.4dB 1W/1m | 89.6dB 1W/1m
Bl: 9.3 N/A | 14.1 N/A
Xmax: 21mm
Rms: 800W
Sealed box: N/A cuft
Ported box: 6-10 cuft @ 33Hz
Sub OD: 18.500”
Cut ID: 16.750”
Mounting depth: 9.500”
Displacement: 0.22cuft


Product code: 01918


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Configure Speaker: Ohm: dual 1 dual 2
FlatwindCoil: no yes +$20
CopperCoil: no yes $5
BP Power: no yes +$40

Image not available

[JonMarsh]

If you're cloning the BD Design Quasar, how low do you think you can take the full range, (they don't have much Xmax, so SPL in a dipole is limited below the baffle transistion)? The Quasar has a large baffle, which helps extend the range of the "full range" driver.

The IXL 18 is a great driver, especially for the buck, for it's intended purpose- IB subs. This usually means an 80 Hz crossover point. Or lower.

This is what I would call a middle range excursion driver (22 mm Xmax). Le isn't posted on Mach 5's web site, nor are motor design details. (not that I can find). I've heard from sources that the Le is about 5 mH, don't know how accurate that is. This would qualify it as a midrange Le value, not as high as the monster travel TC Sounds (and not nearly as expensive).

If that Le value is correct, it probably isn't using a Faraday ring, and would tend to have rising distortion with frequency due to inductivity modulation from the pole piece with increasing excursion. The inductance would seem to be higher than drivers like the TC2+ or the RS sub series, like the RS390 HF, which are about 1 mH.

So, unless the full range unit in a system like the Quasar can operate down to about 100 Hz in the open baffle, I'd be cautious about teaming it up with the IXL-18. Dual RS390HF might be a more feasible choice. Or something like a Cirare 18.00NDW1.

[Lazz]

Thx Jon the Ciare you mentioned looks nice-100.5db spl,fs 29hz is this low enough for open baffle to play deep bass,xmax 7mm is this enough?$210good.These are the specs for the 15" TC 1000's are they simmilar to the 12's you tested from Oz Audio for the Arvo but bigger.Which are the ones to get 4ohm svc or dvc.I should have mentioned I'm thinking of possibly using a 12 or 15" coaxial-something like a Radian or Tannoy DC ,or Cantare 12" havent fully decided yet.


Qts 0.346
Qes 0.381
Qms 3.82
Fs 15.6Hz
Res 3.66Ω
Ls 2.64mH
Lp 3.58mH
Rp 3.16Ω
Dia 320mm
Vas 393l
mms 238g
cms 433um/N
bl 15.0T*m
Spl 87.8dB

[69Stingray]

I have been wondering this. How would a true subwoofer, like the RS315 work in a three-way, crossover over to the midrange at around 100 Hz? Any issue with the woofer receiving *only* a couple watts (assuming normal music listening is in the 80-90 dB range).

[ThomasW]

I have been wondering this. How would a true subwoofer, like the RS315 work in a three-way, crossover over to the midrange at around 100 Hz? Any issue with the woofer receiving *only* a couple watts (assuming normal music listening is in the 80-90 dB range).

A driver that goes down to 100Hz is more typically called a midwoofer not a midrange.

[dlneubec]

I have been wondering this. How would a true subwoofer, like the RS315 work in a three-way, crossover over to the midrange at around 100 Hz? Any issue with the woofer receiving *only* a couple watts (assuming normal music listening is in the 80-90 dB range).

I have done this in a couple of projects, though they are not all passive 3ways. They are a hybrid with a passive MTM section and an active sub section. The first one is here:Mentor Omni Thread
It has a downfiring 12" sealed and powered sub crossed at 100hz.

The second one is underway and is here:HOSS project
It uses a 10" powered sub crossed over at 180hz.

I'm very very happy with the results.

[69Stingray]

A driver that goes down to 100Hz is more typically called a midwoofer not a midrange.

Valid. I just think of 3-ways as Woofer-Midrange-Tweeter.

DLNEUBEC- nice looking projects! I guess I was curious to a passive setup. I have seen project with powered subs, but not passive subs, I assume there is a reason. I would think with a passive sub, you could prevent the bass from being overpowering. The larger magnets are a nice touch and they have plenty of power handling.

Sorry to hijack the thread!

[dlneubec]

Valid. I just think of 3-ways as Woofer-Midrange-Tweeter.

DLNEUBEC- nice looking projects! I guess I was curious to a passive setup. I have seen project with powered subs, but not passive subs, I assume there is a reason. I would think with a passive sub, you could prevent the bass from being overpowering. The larger magnets are a nice touch and they have plenty of power handling.

Sorry to hijack the thread!

I find it to be just the opposite. The active crossover and separate amp allows you to adjust the sub driver to the appropriate level to match your MTM based upon the room you have it in. I find that in smaller rooms I need much less bass volume, so I adjust the gain until I get the appropriate balance.

For example, on the HOSS project. the gain in my upstairs family room was set to probably set between 1/3 and 1/2 of the full gain for the ideal balance (at least by ear). In the main listneing room downstairs, which is much larger and open to several other rooms, the gain is set between 1/2 and 2/3 of the full gain. One day I want to add active EQ that would allow even better room to room integration.

I would imagine that an all passive with a sub driver would have to be designed for a specific room, since a subs bass is so room dependent. I guess its trade-offs you have to decide on to get a fuller range FR.

[69Stingray]

Good point in the tuning and adjustng to the actual room.

[Lazz]

Thx Jon the Ciare you mentioned looks nice-100.5db spl,fs 29hz is this low enough for open baffle to play deep bass,xmax 7mm is this enough?$210good.These are the specs for the 15" TC 1000's are they simmilar to the 12's you tested from Oz Audio for the Arvo but bigger.Which are the ones to get 4ohm svc or dvc.I should have mentioned I'm thinking of possibly using a 12 or 15" coaxial-something like a Radian or Tannoy DC ,or Cantare 12" havent fully decided yet.


Qts 0.346
Qes 0.381
Qms 3.82
Fs 15.6Hz
Res 3.66Ω
Ls 2.64mH
Lp 3.58mH
Rp 3.16Ω
Dia 320mm
Vas 393l
mms 238g
cms 433um/N
bl 15.0T*m
Spl 87.8dB

Do you guys think the coaxials will have any problems operating open baffle xover at @100hz to use with the Mach 5 woofers.Would the bass from this type of driver have big accurate sound or would they be boomy like in a car type situation.I'm after a deep but accurate sound for listening to a variety of music from modern to Mussorgsky.Perhaps if anyone who's used the TC's or Daytons can chime in.I've noticed some people that have experimented with ob have used cheap bass drivers and reported good results but obviously one doesn't know what level of sq makes them happy.I always believe you must at least start with good drivers to have any chance of quality{I know there's exceptions}.I'm coming from diy Dynaudio wmtmw.But after hearing some Tannoy coaxials was very impressed with the way they had a huge life like potrayal to the music,like being in the auditorium at the time of the performance.I know my Dynaudio's are more accurate in imaging etc but I've listened to many box speakers B&W ,Duntechs etc but they dont have that emotion! I'm looking for.I'm hoping the open baffle will get closer to what i"m looking for.I've heard ob only in the midrange on some commercially available speakers here in Australia and loved the sound.

[Paul Ebert]

Um, Guys...

This is all interesting, but the thread's been hijacked just a bit .

I'd really like an answer to my question about if it's a problem if the response exceeds the xmax. I've attached a graph for the RS270 showing what I'm concerned about.

So, to restate the concern, will this response be a problem if I do not intend to play above 90 dB at 20 Hz?

Thanks.

[JonMarsh]

Probably not, Paul. There will be some IM into the midrange of course, how high will you run the RS270? It's too bad it takes such a big enclosure to go ported - the RS270 can get down to 20 Hz with with more output with a port, but the T/S params responsible for it's highish sensitivity also dictate a large box- Hoffman's iron law.

[ThomasW]

So, to restate the concern, will this response be a problem if I do not intend to play above 90 dB at 20 Hz?

Problem is how do you intend to limit the output?

The dynamic range of modern digital recordings is very high. This means if you want to use low Xmax drivers, you should probably buy them by the dozen.

Personally I'd rather live with the consequences of under-working higher Xmax drivers than over-working low Xmax ones.

Just my $0.02...

[Lazz]

Sorry about that Paul I'll throw away t :The gun and hide my mask and start a new thread. :T

[Paul Ebert]

Problem is how do you intend to limit the output?

The dynamic range of modern digital recordings is very high. This means if you want to use low Xmax drivers, you should probably buy them by the dozen.

Personally I'd rather live with the consequences of under-working higher Xmax drivers than over-working low Xmax ones.

Just my $0.02...

Limit the output? Volume control?

Your point is well taken. Seems like I should go with the RSS315HF or the NS12 and be done with it.

So, should I adjust the Vb or Qtc to bring the response under the xmax limit?

[ThomasW]

Limit the output? Volume control?

Doesn't effectively limit high amplitude transient peaks, unless it's turned WAY down.

[JonMarsh]

A single NS12 anehoic at 1 meter will do a pretty credible job ported down to 20 Hz, with significant output below that, considering room boundary reinforcement. Presuming a stereo speaker system, another + 3dB. So, at 1 meter, single cab anechoic is ~104 dB, with three wall boundary reinforcement (floor, side wall, rear wall) it's over 110 dB/cabinet. Two cabs = 113 dB. Double the distance and you're back down to 106 dB. For music, that's pretty credible.



For those needing more, the dual 12 per side like Colorado Tom is planning should work OK. :B

I don't think you'd need to be too concerned ab out limting per se. This is at 100W per channel, a pretty "noisy" playback level. This tuning should work nicely in room, with very LF levels matching up well to midbass.

[Paul Ebert]

Doesn't effectively limit high amplitude transient peaks, unless it's turned WAY down.

Yes, Thomas. I was joking.

[Paul Ebert]

Jon,

Thanks for the NS12 tuning suggestion. Which brings me to a really stupid question:

What, exactly, is meant by a ported design being 'tuned' to a particular frequency? My guess is that it refers to the Fb setting. Is that correct?

A related question: Dickason talks alot about alignments (SBB4, SC4, QB3, etc.) for ported designs, implying that not designing closely to an alignment causes transient degradation. This rarely seems to come up in our discussions. Why?

I've been leaning toward a sealed design, in part because of my lack of understanding. So, any elucidation would be appreciated.

[JonMarsh]

Different alignments are equivalent to tuning above, at, or below Fs of the driver-

My normal "target" doesn't even worry about "classic" alignment categories; I'm looking for an alignment and driver Q combination that produces a slow roll off starting up around 100 Hz that is around 6 dB down at the corner frequency (which is made up by room boundary gain), and drops as slowly as possible after that- for a ported alignment, this more nearly resembles a flat delay Bessel than a Butterworth or higher Q alignment. This Q factor is directly related to the step response settling time, aka transient response.

You can discern some good hints about how damped it is at Fb by how "soft" the corner in frequency response. If you see an alignment this is flat out to a certain frequency and then has a sharp transition to a near straightline roll off, this is much higher Q and will exhibit more smearing in transient response (slow settling time). A quick look at the NS12 shows which category it falls into, compared to some "classic" sub ported alignments. And of course, it's probably quite wise, if you have these goals, to stay away from a driver + cabinet combination that produces peaking at Fb before dropping off... this is quite common in commercial speakers, though.

So, while in the interests of being an open minded moderator I shouldn't say things like "my way or the highway", an alignment like I published above really does sound (IMO) the best of all ported alignments. In fact, it will sound better (IMO) than a classic sealed Butter worth alignment with Q of 0.707, because of the increased extension and comparable or faster settling time. For a sealed alignment, I think a Q of 0.5 is ideal, but that of course makes driver selection and Fb somewhat inflexible. A Q of 0.5 is critically damped with no overshoot, and is 6 dB down at Fb. Most current midwoofers, with their lowish Qts to get good sensitivity, would have a sealed Fb up pretty high in frequency to get a sealed box Q of 0.5 to 0.6. This is where evaluations of whether a driver is better intended for sealed or ported come into play- anything with a free air Q of 0.3 or less is really designed with electrical Q for a ported system, and a driver with a Q of over 0.4 free air is more difficult to optimize for reflex unless you want a boom box.

Just my nickel (I think I want over the 0.02 limit). :W

Consider that the IB subs everyone seems to love when they hear them typically have a