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Old 10th October 2009, 09:30 AM   #11
AndrewT is offline AndrewT  Scotland
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I liked the HM130co as fitted to the KLS3gold.
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Old 10th October 2009, 12:40 PM   #12
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Originally Posted by mondogenerator View Post
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.
I agree the AP series did represent decent value for money. I've got a pair of speakers with the AP100Z0s and a vifa tweeter that are in the kitchen and they sound great. This was when Maplin were selling the AP100Z0s at around 5, at that price you can't go far wrong!

The HM series were a bit different, these fetched much higher prices and were Audax's 'high end' range of drivers.

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I liked the HM130co as fitted to the KLS3gold.
This is my experience of the Aerogels as well. They do sound good and have a very appealing type of sound to them. It's only when you get quite critical of the sound that you realise you can do better. However once you've switched to 'better' it's clearly better.
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Old 12th October 2009, 12:04 PM   #13
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Default although i DID have some (?)HM130MO(?)

i think i had some HM130MO as my first audax speaker....paper cone???

Anyway i swapped from these to the hDA series....HDA sounded FAR FAR less breakuppy and clean as well as more detailed...frankly i think the old paper HM's were budget sounding, despite having a steel frame, rather than the polymer one use on AP series. In the end i doped them with pva till the Fs was about 48Hz(from 59Hz or somewwhere like thart!) and put them in a closed box but they were always a cheap experimant. I was sad to see Audax go, but in all honesty, im JUST about happy with my HDA 130mm, as the visatons kick their *** about the place. besides i dont think audax made a really good tweeter in donkeys years....its a pity really
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Old 15th October 2009, 01:14 AM   #14
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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.
Good evening Matt,

Thank you for taking the time to share your insight into this matter. I would have liked to write back sooner, but we just survived Canadian Thanksgiving over on my side of the pond, for which I was out of town.

I must admit, I've been giving this some thought for a while now and what you've said makes a lot of sense. You've convinced me that the ZA14 is the way to go! I would have liked to mess with the ER15RLY, but having compared Zaph's own distortion plots once more, and then the price, it's tough to argue against the cheaper driver being more suited for my goal of an accurate near-field. And to top it off, the ZA14 is beautiful!

Arta looks like it could be the ticket, and I will certainly give it a look when I have a little time ahead of me. To this point I have no serious test gear. Previously I have used nothing more than a PC based signal generator, multi-meter, and hand-held (cheap) SPL meter for the few systems that I've cobbled together. They've worked reasonably well, but their performance requirement was less than critical.

If I do manage to get rolling with this, I'd like to use the Scan-Speak Discovery HDS tweeter. A decrease in value over the Vifa DQ25SC05-04 used in the ZA5 kits it's true, but at just under 80 USD it still seems like a lot of tweeter for the money, and it can't hurt to spoil the ZA14's a little! Compared to the Vifa's, I may be able to cross-over a little lower, as long as I stay away from the Discovery's rise in distortion below 1600 Hz. Who knows, maybe I could even employ a more shallow LR2 slope, as this will not be a high SPL application. This is all just imagination at the moment, I'll have to sit down and take a good look at the distortion profiles Mr. Krutke has so generously provided to the DIY community. I understand it's advisable to crossover more steeply with a metal-cone!

Thanks again for all your input,

Jim


edit: The Scan-Speak Discovery HDS! Mmmmmm!

Last edited by J.R.Freeman; 15th October 2009 at 01:19 AM.
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Old 15th October 2009, 03:08 AM   #15
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Hmm, it seems I can't edit the last post I've made?

Anyhow, I wanted to add that I appreciate that one of things that makes this mid-woofer (the ZA14) a great value driver is that it's extended bandwidth allows for the use of a cheaper tweeter, in conjunction with it's own excellent price tag. And I suppose paying double for a tweeter is a little crazy, but I wonder if there are any gains to be made in doing so. I just wanted to state that I am somewhat aware of my lunacy, just perhaps not of it's full extent!
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Old 15th October 2009, 01:32 PM   #16
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Hmm, it seems I can't edit the last post I've made?
I think you have 30 mins with which to edit your posts. I don't understand why, a day would seem better.

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And I suppose paying double for a tweeter is a little crazy, but I wonder if there are any gains to be made in doing so.
That's a very good question. However the HDS tweeter is cleaner then the DQ. So which ever way you look at it, you are getting more performance for your money.

I see the HDS tweeter as similar to the ZA14, that is high value. First and foremost you're getting a metal face plate which is always nice. Second you're getting very low distortion. Third, you can pretty much cross this tweeter as low as you want with as shallow a slope as you'd like. The limiting factor is its excursion, as long it's not exceeded, it's going to sound good.

All of the above gives you tremendous flexibility and is something worth paying for, if it's needed. In your situation I wouldn't see it as wasted. You're going to be experimenting with xover design and anything that gives you more room to succeed is a benefit in my opinion. After all the HDS tweeter isn't tremendously expensive itself.
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Old 24th October 2009, 07:17 PM   #17
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Good afternoon Matt,

It's reassuring to hear that you agree with my interest in the Discovery tweeter! I wonder if this tweeters low end response would allow for a 2nd order electrical slope? I suppose there is no harm in experimenting, once I have the drivers (as long as I don't over-drive the tweeter in the process).

Might I ask you something regarding cone materials? I've read more of people who are concerned with using a metallic cone for mid-range applications. You mentioned before that the break-up of a metallic cone driver like the ZA14 is not difficult to tame in the crossover. My question then, is could input frequencies much lower than the break-up node, excite this resonance? As a follow-up question: a notch filter deals with input frequencies of concern, but does it also serve to dampen the motion of the cone at this frequency? So, does the presence of the notch effectively raise Qes at that center frequency of interest? If that's the case, then I suppose we wouldn't have to worry about say a kick-drum exciting the natural ring of the cone, because the notch would deaden it. Is that somewhat correct?

Jim

Edit: I should add that my guess of the notch raising Qes at the center frequency is based on the observation that a speaker can work as a microphone. That is to say, if a driver is fed a signal of 2 kHz (and supposing this is in the usable band of the driver and all that) the cone will attempt to oscillate at 2 kHz. Conversely, if the cone is mechanically driven at 2 kHz, then it will produce that signal at its terminals. A notch filter centered at this frequency connected to the voice coil would sink this signal to ground, and I am guessing as the energy is converted to heat, the mechanical component of the energy (the moving of the cone) would be consumed in the production of this heat, would it not?

Last edited by J.R.Freeman; 24th October 2009 at 07:27 PM.
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Old 24th October 2009, 11:55 PM   #18
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Originally Posted by J.R.Freeman View Post
Good afternoon Matt,

It's reassuring to hear that you agree with my interest in the Discovery tweeter! I wonder if this tweeters low end response would allow for a 2nd order electrical slope? I suppose there is no harm in experimenting, once I have the drivers (as long as I don't over-drive the tweeter in the process).
Yes 2nd order electrical will be fine. As you've read a lot of Zaphs stuff I'm sure you'll be aware that the 2nd order electrical could sum to 4th order acoustic, depending on what xover frequency you choose.

Depending on your design goals and how the tweeter responds in the cabinet, you might have to go 3rd order electrical to allow for some additional response shaping.

Quote:
Originally Posted by J.R.Freeman View Post
Might I ask you something regarding cone materials? I've read more of people who are concerned with using a metallic cone for mid-range applications. You mentioned before that the break-up of a metallic cone driver like the ZA14 is not difficult to tame in the crossover. My question then, is could input frequencies much lower than the break-up node, excite this resonance?
Yes, this is what cone resonance amplification is Think of it another way.

You've got a driver with a nasty resonance peak at 8000hz and as a result exhibits cone resonance amplification, like that of the SEAS metal and the Zaph Audio driver.

Lets feed this a 2khz signal.

Naturally there are distortion products produced.

The second order products land at 4khz, the third, 6khz and the fourth 8khz - bang on our cone resonance.

The result of this is that the cone, because it rings at this frequency, amplifies the distortion product and you see a peak in the distortion plot.

So if you feed the driver a 2.66khz frequency the third order products will be created and then amplified by the cones bell like quality at 8khz.

As far as I understand it, Qms and Qes describe the loudspeakers properties at the natural resonance of the entire system. Therefore they are not appropriate to consider for anything other then this point, especially something like 8khz.

A change in the electrical properties at 8khz, due to the crossover, wouldn't affect the overall Qes. Changing the series resistance however, such as adding a resister in series with the loudspeaker would. This is why you can alter the Q of a system by placing resistors in series with the voice coil. Effectively you raise Qes and as a result raise Qts (you also lose sensitivity).

Having said all that, I do understand what you're trying to get at. You place some sort of electrical system at the drivers terminals, such that when you feed the driver a 2khz signal, the 4th order harmonic excites the driver at 8khz. The electrical circuit presents a short to ground at this frequency and directly opposes the additional motion created by the cones ringing.

Sadly this isn't the way that it ends up working. A series notch filter connected in parallel with the driver will lower the input impedance at the tuned frequency. In addition it's effect also lowers the overall impedance both above and below the frequency it was tuned to. This unfortunately would make the loudspaker a veritable amplifier killer. However when paired with an inductor, as shown in Zaphs L18 two way, this removes that issue and you see the standard rising impedance with increasing frequency.

A Parallel notch filter connected in series with the driver works in the opposite way and increases the impedance that it is tuned to. This reduces the power the amplifier delivers at that frequency and thus reduces the output. These filters are widely seen when used with full range drivers to tame response peaks etc.

It might be interesting in terms of motion feedback. As far as I understand MF the second coil, used as a microphone, shows the input of the amplifier the difference between its output, created by the non linearities of the driver unit. As a result of this it tries to compensate and reduces distortion. You'd figure this could work for cone resonance too, but this is something I know extremely little about so you'd have to ask someone else.

Simply speaking the only thing you can do is crossover low enough, such that the distortion products created by the cone resonance amplification, are off the audible radar. This of course should be easy with the HDS tweeter as it can cross over so low.
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Old 4th December 2011, 05:29 PM   #19
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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.
I know this is a old thread- but IMHO is gives a bit of misinformation.
If you first look at the plots for each driver-they have quite a bit of difference-so assuming the areogel and carbon fibre drivers are similiar is a bad assumption. Different cones materials usually sound different-even from the same manufactor-just look at the plots.
The HM130CO has a exceptionally flat frequency, and impedence curve in it's intended frequency range, ulike the other drivers you were comparing it to-plus a excellent waterfall response. In addition the Audax HM130Co actually has some effieiceny, and is no where near the 'ballless' driver you have compared to.
I'm not sure what you mean by fake detail, as I don't hear that, especially after the proper breakin.
Lot's of advantages to stiff cones- most manufactors use these for a number of reasons-including better piston action and sonic accuracy coupled with low distortion.
The drivers size limit's it's best use as a midwoofer-coupling a larger woofer and tweeter-not in a 2 way design.
Perhaps you prefer over damped lifeless 'soft' speakers-and that's fine-the Audax wouldn't be for you-perhaps a old driver with a soft cone might please your ears.
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Old 4th December 2011, 08:44 PM   #20
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I know this is a old thread- but IMHO is gives a bit of misinformation.
If you first look at the plots for each driver-they have quite a bit of difference-so assuming the areogel and carbon fibre drivers are similiar is a bad assumption. Different cones materials usually sound different-even from the same manufactor-just look at the plots.
The HM130CO has a exceptionally flat frequency, and impedence curve in it's intended frequency range, unlike the other drivers you were comparing it to-plus a excellent waterfall response. In addition the Audax HM130Co actually has some effieiceny, and is no where near the 'ballless' drivers you have compared it to.
I think many mistake highly efficient drivers as being horn like, or pro adui types. Not so. Many current designs are relizing the benifits of high efficiency designs. Not merley to play loud-but to acheive and better overall balance in the freqeuncy extremes, and this more importantly and low to medium levels, where the majority of home audio listening takes place. A proper balance at this levels negates the need for varoius tweeks and tricks to acheive balance at these levels.
The problem with many modern midline speakers, despite the high efficiency, is that they stop short of being true full range, and cut off in the 50-55hz range, thus needing a subwoofer and all the added problems that entails. Not they they can't do it-but they choose to price point, and this is probaly whta many consumers want -double duty-and a home shaking sub.
I'm not sure what you mean by fake detail, as I don't hear that, especially after the proper breakin. Superbly clean and detailed and a razor flat frequency repsonse as well.
Lot's of advantages to stiff cones- most manufactors use these for a number of reasons-including better piston action and sonic accuracy coupled with low distortion.
This isn't meant to be a soft dome tweeter
The drivers size limit's, and overall frequecny respone, it's best used as a midwoofer-coupling a larger woofer and tweeter-not in a 2 way design.
And this is were it excells.
Perhaps you prefer over damped lifeless 'soft' speakers-and that's fine-the Audax wouldn't be for you-or most modern drivers
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