Audax HM130C0: Opinions?

[J.R.Freeman]

Good afternoon all,

This driver seems interesting, do any of you have experience with it?

http://madisound.com/catalog/product...oducts_id=1764


I wonder how it would perform in a near-field monitor 2-way application? It's lower roll-off might limit its use as a mid-woofer, but perhaps in a ported enclosure it could reach the high 60's. On the plus, it is fairly sensitive, and Qts is rather low with most of that damping resulting from the large motor. The inverted surround is kind of a neat look too, and I suppose should prevent some edge reflections. That basket type is a long-time DIY detractor however, but I don't entirely mind the look of such drivers should one figure out how to mount them correctly.

Jim

[critofur]

I would expect that woofer to be used in a 3-way. Probably not the easiest to design a crossover for, but I believe it was used in a highly regarded Von Schweikert Research model? I googled some and found that its used in several such as the VR-3, VR-4, etc...

Here's a review... http://www.soundstage.com/das_vr3.htm


I have a pair of the 6.5" version of these woofers. It's a very nice high quality construction. I did not flush mount mine yet, though it wouldn't be too hard using a method similar to how I made my template in this thread:

Epoxy putty for odd driver shapes

Just make a circular cutout to flush mount it, then put the driver in place with a few layers of "scotch" tape around it and fill in the gaps with some appropriate filler such as epoxy putty, bondo, etc, sand smooth, then finish as you usually would.

If you wanted to use a nice solid wood baffle, then it might be a little trickier to get nice asthetics - might be an interesting look depending on what color filler you use?

EDIT: They seem to be out of stock at Madisound now.

[Salas]

Originally Posted by J.R.Freeman

Good afternoon all,

This driver seems interesting, do any of you have experience with it?

http://madisound.com/catalog/product...oducts_id=1764


I wonder how it would perform in a near-field monitor 2-way application? It's lower roll-off might limit its use as a mid-woofer, but perhaps in a ported enclosure it could reach the high 60's. On the plus, it is fairly sensitive, and Qts is rather low with most of that damping resulting from the large motor. The inverted surround is kind of a neat look too, and I suppose should prevent some edge reflections. That basket type is a long-time DIY detractor however, but I don't entirely mind the look of such drivers should one figure out how to mount them correctly.

Jim

Performs well. Had 4 of them, 2 per side per channel, bass reflex, with a long planar along their edges. Went to 50Hz with room aid. Give it a try.

[5th element]

If it performs anything like the Aerogel series then you can do better when it comes to non linear distortion.

The Aerogels suffer from 'cone resonance amplification' in their HD plots, both the third and fifth harmonics show this. Just like you can see the frequency response mirrored in the distortion plots of hard cone drivers at 1/3 and 1/5 of the fundamental frequency.

Attached are two pictures, the first is of the Seas Excel W15CY001. This is a distortion plot I made and as you can see the third and fifth harmonics mirror the frequency response.

The second picture is from Jon Marsh over at HTguide and is of an Accuton ceramic mid. As you can see in the third order plot (dashed line) it again mirrors the frequency response.

Fifth order harmonics are usually low enough down as to be off the audible radar so can be ignored.

In both the Seas and Accuton the effect happens high enough up so that you can cross over before it becomes a concern. My implementation of the W15 crosses it 4th order at 2.2khz, like this you see a slight peak in 3rd order above the rest of the HD plot, but its very low down and for all intents and purposes off the audible radar.

The Accuton is extremely well behaved and has a great motor as the HD plot shows, even with 'cone resonance amplification' happening the third harmonic remains better then 50dB down over the fundamental.

The Audax motor isn't anywhere near as well done and unfortunately the third order is at around 40-45dB down over the fundamental. The fifth order is off the audible radar however.

This in itself wouldn't be a problem if it occurred past a certain frequency, but sadly this isn't the case. Cone resonance amplification appears as low as 500hz in the 3rd harmonic iirc and keeps on going.

This is easily audible when listening to the sine sweeps when the driver is under test. The W15 sounding subjectively a lot cleaner - which is no surprise when you see how clean the distortion plot is.

The Audax HM130Z0 and HM210Z12 that I tested both showed the same problem. Although measuring 'badly' (the third order in both drivers was worse then almost all drivers Zaph has tested.) they do sound 'very lively' and 'fast' which is an extremely appealing sound - it's what attracted me to them in the first place.

However when compared to the W15CY001 and RS225 in the same application they are notably coloured in comparision. The W15 and RS225 being FAR cleaner and smoother sounding.

This isn't discussing the carbon fibre of the C0 version mind you. But C0 is very stiff and would most likely have similar results.

If it were my pennies I'd buy the Zaph Audio ZA14 driver. It hasn't got a lot of coverage yet as its very new, but on the whole it measures as good as a W15CY.

Audax do have a habit of updating models without changing the model number and these are new drivers put together by AAC. It's possible they've updated the motor, but without seeing measurements I'd rather put my money elsewhere.

[J.R.Freeman]

Good evening all,

Thank you all for your comments. It's fun to have a sounding board such as diyAudio to bounce ideas off of, and I'm always interested to hear the opinions of folks around here. I've learned a lot already!

Critofur, thanks for the links and the suggestion on how to deal with such a flange. That's an interesting trick, that I might just have to try. I would likely be finishing with a veneer anyways so the filler would be covered.

Salas that's impressive that you could get down to the 50's with room gain, though I suppose twice the Sd over a normal 2-way helps! I've been toying with the idea of a near-field monitor for a while, with the goal of accuracy in mind. Unfortunately I have to think of budget too, but that's interesting.

5th Element, thank you for your extensive write-up! Thank you especially for those graphics to go along with what you are saying. Having read through Zaph's page I am familiar to some extent with fractional harmonics of the fundamental break-up, but I didn't know this 'cone resonance amplification' was a hard-cone disease. The Excel is a beautiful driver, and I would love a pair to death! But they are out of my price range, as are the Accuton drivers.

It's true this Audax driver doesn't stand up on paper to those mentioned above, but they are a little on the exotic side and I would say the comparison is a little unfair! But those drivers do showcase your points regarding hard cones. For the price of these Audax drivers, however, (if they are ever in stock again!) they look pretty reasonable. You mentioned their motor structure to be lacking, but I was rather impressed to read that they use edge-wound flat copper windings, and produce pretty decent efficiency.

Do you suppose their performance is similar to the HDA series of drivers? I heard a few Aerogel Audax systems and found them to lack detail to some extent, but perhaps this was implementation in part to blame. They reminded me of soft polypropylene cones, that made kick drums sound loose and flabby. But carbon fiber is quite different. Looking at the response curve quickly at Madisound (http://www.madisound.com/catalog/PDF/hm130c0.pdf), there appears to be a break-up node at 4600 Hz. Now, magnesium cones for example would show more of a peak in terms of magnitude at this point, but this one is only 3 dB up. That is still significant, however, but not as severe as what is seen in other cone materials (is it +6 dB in acoustic output = double?). So the 3rd harmonic down would be around 1533 Hz, and the fifth at 920 Hz. As you said the 1/3 and 1/5 seem to mirror the fundamental, is it true then that the magnitude of these subsequent break-up induced peaks are derived from that of the fundamental break-up? If so, (all speculation!) this cone resonance amplification may not be as much of an issue as the fundamental breakup seems relatively benign, to my eyes anyhow.

Maybe it's worth searching around for some distortion plots, do you think? I'd love to get a pair for fun, but most of this is window shopping as I don't have the cash to play around with many different sets of drivers. This is interesting though, thanks for all your input (to all)!

Jim

[5th element]

Originally Posted by J.R.Freeman

Having read through Zaph's page I am familiar to some extent with fractional harmonics of the fundamental break-up, but I didn't know this 'cone resonance amplification' was a hard-cone disease.

I was surprised to see it present so badly (very hd) in the aerogel cone. I know they are somewhat stiff (they are also brittle, unlike a paper cone they will crack rather then crease) and do have slightly peaky breakup, but no worse then some paper cones. I'm not entirely sure what governs whether or not the breakup will be present in the HD plots.

Originally Posted by J.R.Freeman

For the price of these Audax drivers, however, (if they are ever in stock again!) they look pretty reasonable. You mentioned their motor structure to be lacking, but I was rather impressed to read that they use edge-wound flat copper windings, and produce pretty decent efficiency.

They've also got reasonably low inductance too, hinting that there's a decent amount of stuff going on in the motor. I was surprised to see how bad the third harmonic was. I think the High HD of the Aerogel drivers is basically down to an average motor, but because the aerogel cone has some problems of its own, it makes the performance that much worse.

Originally Posted by J.R.Freeman

Do you suppose their performance is similar to the HDA series of drivers?

I don't really know, but I'd expect the carbon fibre cone to exhibit some cone resonance amplification, carbon fibre is after all very stiff. It would be interesting to measure the paper and carbon fibre versions of the 130 series in the prestige range and see how they compare.

Originally Posted by J.R.Freeman

I heard a few Aerogel Audax systems and found them to lack detail to some extent, but perhaps this was implementation in part to blame. They reminded me of soft polypropylene cones, that made kick drums sound loose and flabby.

Implementation is very important and can easily hide/expose flaws inherent to the drivers. Compared to the W15/RS225 implementation they do lack detail, but it's not immediately apparent as a problem when you're listening to the aerogels in isolation. What I could hear was a thickening of the sound, like massed voices would blur together a little - this can be a fault of the tonal balance too. The more you increase the bafflestep compensation the 'warmer' a loudspeaker will sound. But an increase in distortion can also sound similar.

The trick would be to balance the two, turn down the bafflestep to help compensate for the higher distortion. This would give you a pleasing tonal balance and not thrust the blurring of voices in your face, but you'd still be able to hear it. So if you think its a tonal balance problem you try turning down baffle step even more to compensate, but now you've got a thinner sounding loudspeaker then you want. What you really want to do is replace the driver.

Originally Posted by J.R.Freeman

(is it +6 dB in acoustic output = double?).

A 3dB increase in output level will require twice the number of watts (power). 10log(p2/p1)

90dB = 10 watts.
93dB = 20 watts.
96dB = 40 watts.

If we're talking in terms of distortion (the difference between two voltages). 20log(v1/v2)

-40dB = 1%
-46dB = 0.5%
-52dB = 0.25%
-60dB = 0.1%

If we're talking in terms of perception you need a 10dB gain for something to sound twice as loud.

Then there's distortion perception too, as we're far more sensitive to certain types of distortion then others.

Originally Posted by J.R.Freeman

Maybe it's worth searching around for some distortion plots, do you think? I'd love to get a pair for fun, but most of this is window shopping as I don't have the cash to play around with many different sets of drivers. This is interesting though, thanks for all your input (to all)!

I tried searching for distortion plots of the aerogel drivers and came up with nothing It would certainly be nice to find HD plots for the C0s.

Attached are two images showing HD for the HM210Z12 and the HM130Z0. This was measured at just over 3 volts RMS, so a little over 1 watt into an 8 ohm load.

As you can see the second and third are quite high. Second I half dismissed as its fairly benign sounding. The third I was not impressed with at all.

The peak in HD at around 400hz directly corresponds to a wiggle in the impedance plot as shown in the impedance plot, so something's definitely going on there.
My problem with the Z12 is that I needed to push it quite hard within this range on the open baffle and this gave a parge peak in HD in the range where it was used.

It's the same with the Z0, something is going on, as there's a slight impedance wiggle as well. Note that I have applied some cone treatment to the Z0 and that did reduce the HD by a little bit and smoothed out the breakup considerably.

Whether or not the C0 will show similar traits is unknown, but if the motor is similar, which is likely, then I'd rather buy something else. Of course I'd be open to trying them out, if it wasn't my money!

Yes the Accuton and W15 are expensive, but the ZA14 is not expensive at all and has performance equal to that of the W15.

Maybe I'm being slightly too critical of the Audax drivers, but when there are better performers for the same or less money, they just don't make much sense.

[J.R.Freeman]

Good afternoon 5th,

Thank you once more for your input, it is much appreciated! Yes, that's interesting about the stiffness of the HDA cones - having heard a few systems I thought they would be rather soft but it turns out (having read a bit on wikipedia!) that Aerogel is a rather stiff compound. It's too bad Audax couldn't get the HDA cones under control, as I remember finding them interesting looking.

You've made a good case that the Audax HM130C0 is not a great pick for that price point. It's too bad, it looks like a nice driver, and I must admit, I'd like to do something a little different. But in the end it is accuracy I am after, and if there is a better option out there for less money, there's no sense in passing it up.

The ZA14 is an impressive looking driver, that's for sure. It's even a pretty driver! Strangely, I found Mr. Krutke's report of his driver via Google, and not a direct link on his page.

http://www.zaphaudio.com/ZA14W08/

Along the way I also found a review by Mark K. on his page:

http://www.audioheuristics.org/measu.../ZA14/ZA14.htm

Anyway, it sure looks like a great little driver. At that price it is surely a heck of a deal. My only concern is that when I first heard about it on this site, someone mentioned they had a unit with an off-centered phase plug (reference to come - I'll search around on the site a little more later). For such a low price, I would be concerned with build consistency, though I'm sure someone as meticulous as Mr. Krutke would have quality control measures in place. Perhaps the off-centered unit was damaged in shipping.

Before I run out and buy a set of ZA14's (as I am close!) I was wondering if we might expand this discussion to include any nice, small mid-woofers (around 5.5"). 5th Element, you've already been more than helpful so don't worry about writing further if you are busy. This is an open invitation to anyone who'd like to discuss a similar driver however!

http://madisound.com/catalog/product...oducts_id=8180

Another driver I find interesting is the Seas ER15RLY. As a fairly rigid cone, it has a significant break-up node, however it is at nearly 6 kHz. I wonder if this is far enough out of range that a 2nd order electrical slope could be used at the crossover point? If so, that would certainly be an attractive point as the ZA14's would likely need a more aggressive LR4 slope to stay away from the 3rd and 5th harmonic of the fundamental breakup. The distortion performance of the ZA14 is likely superior (I haven't had a chance to look at all the data yet) but if the ER15RLY requires less components in the signal path and perhaps a more shallow crossover slope, I wonder how the final system would compare. I must admit I am a little apprehensive about using a metal cone, with neutrality in mind, but perhaps that is fear of the unknown!

Jim

[5th element]

Originally Posted by J.R.Freeman

Good afternoon 5th

Please, call me Matt.

Originally Posted by J.R.Freeman

My only concern is that when I first heard about it on this site, someone mentioned they had a unit with an off-centered phase plug (reference to come - I'll search around on the site a little more later). For such a low price, I would be concerned with build consistency, though I'm sure someone as meticulous as Mr. Krutke would have quality control measures in place. Perhaps the off-centered unit was damaged in shipping.

Quality control and consistency between batches is one thing John is very concerned with. He has mentioned that he is taking a very active role in making sure that the drivers don't fall too far from spec.

Originally Posted by J.R.Freeman

Another driver I find interesting is the Seas ER15RLY

John's already one step ahead of you and by the time you get to reading this, you'll probably have noticed that he's measured it already.

It's a decent driver, my only problem with it is the 3rd order products it produces, they are not bad, but you can do better and I think this is where my problem lies.

From the measurements the ZA14 beats anything anywhere near that price point. It then goes on to give the boutique drivers from the best manufactures a good run for their money, coming up equal and better then some.

Of course others better it in certain areas, bass being one of them. However I don't see this as a disadvantage. Anyone building a loudspeaker system around a 5.5" driver isn't looking for floor shaking levels of bass. They are more then likely attracted to them for their midrange performance, which is exactly what I see small drivers for.

The ZA14 has a slightly smaller cone then other 5.5"s meaning it beams less for a given frequency, this also pushes its resonance peak higher. It's cone is kept lighter, increasing it's sensitivity. These things all = better as a midrange driver and as a result you lose some bass. However if anyone really wants bass they can add a sub in my opinion.

It's for these reasons I find it hard to recommend anything other then the ZA14 for anyone remotely interested in a high value 5" driver - I'd use it over the W15CY001s in my application. (And that they are in the USA I'd have bought a pair of I was).

Originally Posted by J.R.Freeman

I must admit I am a little apprehensive about using a metal cone, with neutrality in mind, but perhaps that is fear of the unknown!

It's exactly that. Metal cone drivers are not hard to work with and can, in a lot of circumstances, be easier to work with then some of their 'soft' cone counterparts.

Metal cone drivers usually have very flat frequency responses with no sign of resonance/breakup before their primary peak, which you hope is high up. This means they generally require very basic filters to arrive at a target acoustic slope.

Go and check out John's designs using metal cones -

http://www.zaphaudio.com/ZMV5.html
http://www.zaphaudio.com/ZBM4.html
http://www.zaphaudio.com/audio-speaker17.html

You'll notice that they don't need anything elaborate at all to work well.

This nicely brings us to this page

http://www.zaphaudio.com/ZA5/

Loads of projects for the ZA14.

If you're intimidated at designing your own crossover, the least you could do is ensure that your baffle width is 8" and use John's crossover for the mid/bass. Then you'd have a firm starting point for designing your own tweeter crossover for your own chosen tweeter.

That said the vifa tweeter John uses in his designs is hardly expensive, you could just build a kit and experiment with that. That way you'd get the cost reduction from buying a kit and you'd be safe knowing that you've got a good design to fall back on.

At the very basic level, if you're serious about wanting to learn how to design your own crossovers I strongly suggest you investigate acquiring a way to measure frequency response and impedance. (Having said that you may already have the ability to do this )

There are a few (free) programs that will allow you to simulate reasonably accurately, without needing to spend a penny. But you can get very decent measuring equipment for relatively, very little money. Because of this I really don't see the point in faffing about with semi accurate simulations - Although having said that you will learn a heck of a lot following the theory behind why you're doing what it is you're asked to do whilst using the free simulators.

http://www.rjbaudio.com/Audiofiles/FRDtools.html

The Arta set of programs -

http://www.fesb.hr/~mateljan/arta/

Is a free and very easy to use (once you know what you're doing) set of programs that will measure a whole assortment of things and you don't even need to buy anything to start using it.

To learn how to use the program you can simply loop the output of your soundcard back into the input. This way you'd only be measuring your sound card, but it will show you lots of arta's functionality. For example you can play with Steps to measure distortion, then faff with Arta to measure the frequency response in several different ways, and you can also familiarise yourself with the spectrum analyser, where you can see the distortion + noise level amongst other things.

If you have any further questions you're more then welcome to ask.

[jupiterjune]

I have used the HM100CO's, which I had crossed over to the tweeters at around 3200 Hz. They had a noticeable sibilance with certain female vocalists. The detail was incredible, but I couldn't get past the sibilance which I attribute to cone breakup. I would expect the same for the HM130CO's. I believe this is in line with what Fifth element said to expect.

JJ

[mondogenerator]

i have a system built using (in part) the 'audax d'appolito' design using AP130ZO and the audax tweeter, but omitting the 8 inch driver...If your audax driver is anything like this then i would recommend them quite highly.

The HD driver s DO have their inherent problems, but when you consider that they are designed to not be HARD diaphrams and that they(WERE at least) somewhere around £18, they have good detail and response easily down to 55Hz in sbb4 alignment, and probably represent one of the best drivers for that price. I am now buiding a system using the visaton Al130 and gc20, and i find the sound cleaner(but then these drivers are 3 times the price), and bass extension significantly better. IMO the audax used with a good well designed crossover is actually a fairly good system..i actually have some of the AP100ZO also for my next mini monitors.
HOWEVER as Audax are now defunct, im not sure youll be able to source them.