Morel MW144 deceitful specs

Hi everyone

I acquired a pair of Morel MW144 drivers 2 days ago, with the intention of building a small ported bookshelf. What attracted me about this driver was a very low Fs for its size (45Hz) and extended frequency response (flat up to around 7KHz) with nice off-axis response also. Well, the only strange thing was that the impedance plot from the spec displayed a peak at 70-80Hz, nowhere near 45 Hz, as the table stated. Well, I said, the graph must be wrong! What a perfect example of wishful thinking.

Just a few minutes ago I said to myself... why not run a Google search with "morel AND MW144" to see what other people have built with these? I did this I while ago but got bored quickly (too many distributors pages, too may in russian or chinese).

Well, imagine my surprise when I found these 2 pages:
http://www.snippets.org/pipermail/diyspeakers.new/2004-February/022494.html

And I quote "For what it's worth: last October I bought a pair of MW144's, and I was disappointed to find that my units do not meet the published specs. Fs is way high, Bl is way low..............."

Huh, Fs way too high the guy says? Well, he must be wrong, after all he doesn't quote figures! Well, at a price of over $100 for a 12 cm "midbass" one does not give up hope easily.

But... http://www.audiocad.de/u/bauvor/hathor2/hathor2.html

Omigod! Just give the impedance plot a look... Typical for a closed box, with a driver resonance peak at... 75Hz :( Wow, and initially I was afraid that a F3 of 55 Hz won't do. And it's obvious that those are the guy's measurements.

Has anybody here measured this driver? Maybe it's not too late for a refund.
 
Hello PP

Have a look at, www.iplacoustics.co.uk, he has several models using the 144, including a " TLine ". I built an early version of the latter several years ago and they are still going strong and sounding good, amazing bass for their size. Ivan Leslie the man behind IPL is very knowledgable and helpful, I am sure he can help. His range of TLines kits are excellant, I have built two, M3tl and S3tl, in the past and are superb

Roy
 
mr_push_pull said:
Hi everyone
But... http://www.audiocad.de/u/bauvor/hathor2/hathor2.html

Omigod! Just give the impedance plot a look... Typical for a closed box, with a driver resonance peak at... 75Hz :( Wow, and initially I was afraid that a F3 of 55 Hz won't do. And it's obvious that those are the guy's measurements.

Has anybody here measured this driver? Maybe it's not too late for a refund.

Keep in mind that the response shown in that page is in-box; placing an MW144 in ~4 liters sealed will yield an in-box resonance of 75 Hz. That appears to be the case at the Hathor site. The in-box resonant peak is not representative of the actual Fs of the driver; the resonant frequency of the system is adjusted upwards based upon the ratio of Vb to Vas. And the peak impedance of the sealed box system will occur at the resonant frequency of the box.

Dan Wiggins
Adire Audio®
 
Hi Roy

I've been knowing about IPL for some time and also read the TNT review for Ivan's TL that uses MW144.

Don't know, maybe Ivan has his drivers going though some serious quality control? We all know that this one of the difference between drivers for the DIY market and those for OEM customers.
Anyway, if I'll find my suspicions confirmed I'll build a TL with it. Maybe Ivan sells plans for his enclosures?
 
Re: Re: Morel MW144 deceitful specs

DanWiggins said:


Keep in mind that the response shown in that page is in-box; placing an MW144 in ~4 liters sealed will yield an in-box resonance of 75 Hz. That appears to be the case at the Hathor site. The in-box resonant peak is not representative of the actual Fs of the driver; the resonant frequency of the system is adjusted upwards based upon the ratio of Vb to Vas. And the peak impedance of the sealed box system will occur at the resonant frequency of the box.

Dan Wiggins
Adire Audio®
Hello Dan

Thanks for pointing that out. I guess I haven't done my homework :) Anyway, something is probably wrong with the Morel specs, but let's some that's in a positive way.
I'll get the chance to measure the real impedance in about a week.
 
Re: Re: Morel MW144 deceitful specs

DanWiggins said:


Keep in mind that the response shown in that page is in-box; placing an MW144 in ~4 liters sealed will yield an in-box resonance of 75 Hz. That appears to be the case at the Hathor site. The in-box resonant peak is not representative of the actual Fs of the driver; the resonant frequency of the system is adjusted upwards based upon the ratio of Vb to Vas. And the peak impedance of the sealed box system will occur at the resonant frequency of the box.

Dan Wiggins
Adire Audio®

I tested a few of these. Actually, the Fs was that high without a box. The following measurements were taken on an infinite baffle.

Performance was overall pretty disappointing. Bass extension is poor for a driver of that size, efficiency is low, Qts is too high and the response is ragged. Yuck.
 

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I think it's a bit harsh to use the term "deceitful specs".
We're talking about electomechanical devices which by their nature are difficult to produce with low tolerances. I don't think Morel is attempting to deceive, though they may be accused of showing better than average specs.
Applying the same term to Bose may be a different story, or those companies stating they produce the "worlds best speakers".
 

wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
my measured specs

Here are the measurements of 4 MW144's that I have... this was after a mild breakin...

The fs is a bit higher than published, but not incredibly so, they model about the same as the published specs, in my test box 6L they have a box resonance of about 84Hz which is also pretty much the 3db down point.

I modeled the drivers based on published specs before purchasing so I'm not at all suprised by the lack of bass response.... They actually have very nice sounding bass, it just doesn't go that low.

impedance plot of two units in parallel in 6L boxes is shown below

[IMGDEAD]http://home.people.net.au/~tonywww/impedance.GIF[/IMGDEAD]

Note that I discovered today I had stuffed up the modeling and should really be a 5 litre box per driver but at least it's only a prototype....

Tony.
 

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wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
nearfield response

and here is the nearfield response that I measured this afternoon....

disturbances around 500- 1Khz are box reflections/resonances I'm experimenting with different damping materials at the moment to tame them.... the 2Khz dip just happens to correspond with my baffle width (2Khz wavelenght is 175mm approx which is my baffle dimention).... not sure if it is what's causing it.... besides nearfiled is probably only any good up to about 500Hz anyway (according to dickason 200Hz)...

This is a completely unsmoothed as it was recorded freq response plot.

Tony.

edit: btw you aren't confusing in box resonant freq with free air resonance are you???
 

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wintermute

Administrator
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2003-08-03 11:43 am
Sydney
DONT PANIC!! ;)

since you said you wanted to do small vented boxes, I've modeled in speakerworkshop a quasi butterworth alignment (I'm not at home so don't have access to my preffered modling program unibox) based on my average parameters that I measured for my 4 drivers.

The -3db point is 50 Hz which I think is pretty reasonable for a 5" driver.... I'm sure if you played around with volume and tuning frequency you could get it lower than this...

here is the plot

I'd say do your own measurements and don't jump to conclusions, I think you will find you have a very nice little driver on your hands.... however my testing so far indicates it isn't flat out to 7K no where near it, but I'm also not 100% sure about my test setup for gated measurements.

Tony.
 

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wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
and just for completeness.....

Here is the free air impedance measurment for one of the four woofers...... it is higher than the published spec yes... I did (attempt) to break the drivers in but I didn't see any change in fs after doing so, so I may not have broken them in completely... note Vance Dickason says that there is no fundamental change in driver paramters after breakin, and that really all it serves as is a way of determining if there are any mechanical problems with the drivers..... (at least that's what I think he said) ;)

I think you have seen some impedance plots (like the one I posted earlier) of the driver installed in a sealed box (probably around 5L) and mistakenly thought that it was the free air resonance impedance plot...

Tony.
 

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Re: and just for completeness.....

Hi Tony and thanks for posting your measurements. Also thanks to Zaph.
I tried to email you though DIYAudio but you have disabled the feature. I'd like to have your measurement data for a bit of experimenting with UniBox before I make an impression. Would you be so kind to send me a private message if you don't want to enable it?

I think you have seen some impedance plots (like the one I posted earlier) of the driver installed in a sealed box (probably around 5L) and mistakenly thought that it was the free air resonance impedance plot...

Tony. [/B]
In fact I did, like I said in reply to Dan Wiggins' post.
 
Quick note:

Tony's measurement of Fs being ~10% high is actually within spec; it is VERY hard to guarantee compliance tighter than 15%, and that means the parameters that depend upon compliance (Vas, Fs, etc) will also have some variance in them. I'd say a claimed 45 Hz Fs, with a measured 50 Hz Fs is pretty darn close, especially if the Vas is slightly smaller than the claimed value. Simply spider tolerances.

Zaph's graph, though, is quite perplexing - not sure why it's so high!

Dan Wiggins
Adire Audio®
 

wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
DanWiggins said:
Quick note:

Zaph's graph, though, is quite perplexing - not sure why it's so high!

Dan Wiggins
Adire Audio?


I don't think it can possibly be the same driver, either that or something was horribly wrong with the sample he had or something went horribly wrong with his testing (no offence zaph... I know I have had some doozies at times ;) )..... It's not just the FS that is so far out, look at the Vas less than half (closer to 1/3rd) my measurement, the le (more than three times my measurement) and the qes which is at least half as much again..... about the only parameter that bears any resemblance is the re....

My drivers are from Isreal btw....

I've enabled the email feature.... maybe I shouldn't have had 2 pints at the pub tonight ;) the wording always put me off... it implies that if you enable it then anyone viewing your public profile can see your email address....

Which measurements are you most interested in? free air impeadance?? I could export some FRD files, the current speakerworkshop file is about 180MB. :eek: (a lot of that is rubbish, I was having a few issues with my measurement mike..... hopefully all fixed now)

BTW here is a link to my other thread I started quite a while back.... http://www.diyaudio.com/forums/showthread.php?postid=563583#post563583 also has a lesson about how things aren't always as they seem, and how easy it is to make a mistake (Keltic was using the FS of someone elses driver in his modelling).... and looking at that nearfield measurement, I think I need to revisit my very first damping arangement!!!! much better than the latest one in the 500-1Khz region!

Tony's measurement of Fs being ~10% high is actually within spec; it is VERY hard to guarantee compliance tighter than 15%, and that means the parameters that depend upon compliance (Vas, Fs, etc) will also have some variance in them. I'd say a claimed 45 Hz Fs, with a measured 50 Hz Fs is pretty darn close, especially if the Vas is slightly smaller than the claimed value. Simply spider tolerances.

I must admit when I first measured them I was pretty disapointed, but after a few wise words from people here and reading some stuff in the loudspeaker design cookbook, I accepted that this was in fact pretty normal. Once I made my test box any previous reservations I had started to evapourate :)

I might re-measure the free air impeadance now that they have been tested to within an inch of their lives, and had miusic played on them quite a bit.... will be interesting to see if the FS has dropped.... they only dropped by about 1/2 Hz after my initial attempt at breaking them in!

Tony.
 

wintermute

Administrator
Paid Member
2003-08-03 11:43 am
Sydney
Hi madmike,

No I don't unfortunately.... I only have the mw144 and DMS37.....

I got a very nice gated measurement of the DMS37 the other day and then speaker workshop crashed on me, and I haven't been able to reproduce it :( It gave me hope that my mw144 measurements may improve too..... basically my gated measurements have been all over the place, and this one measurement of the tweeter was pretty close to the published spec, what I had been getting was huge variances of +- 6 db from published.... Oh well I'll hopefully get it sorted soon.

This is from LDSG [IMGHTTPDEAD]http://ldsg.snippets.org/graphics/morel/mw-166-senstivity.jpg[/IMGHTTPDEAD]

and if you trust spec sheets, then you could use this..... (actually I think it is where the above graph came from :)

http://www.eltimaudio.com/products/MW 166 datasheet.pdf

Tony.