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Multi-Way Conventional loudspeakers with crossovers

Driver for JBL 708-ish dimensioned 2-way
Driver for JBL 708-ish dimensioned 2-way
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Old 2nd December 2021, 05:15 AM   #51
fluid is offline fluid  Australia
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Quote:
Originally Posted by Zvu View Post
lower Mms midwoofers (if other parameters are satisfactory) sounded livelier in midrange.
Two things to consider out of this that is relevant.

"If all other parameters are satisfactory", this is why I think concentrating solely on the weight of the cone is a bad idea.

What is the frequency response, the impedance response, the Sd, the xmax, Le, the motor design, CSD etc. etc.

"Sounded Livelier" descriptions of sound are notoriously difficult to interpret and this is not meant as any criticism, but what happens if Zvu's livelier is not an attribute you prefer?

If you have not tried a lot of different things yourself or have found a person in whose opinion of sound quality you seem to share significant agreement how are you to know whose opinion to trust?
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Old 2nd December 2021, 07:30 AM   #52
mjvbl is offline mjvbl  Europe
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Originally Posted by sheeple View Post
The Beyma 10G40 has actually a bit lower Mms at 52g and a reasonably controlled cone break up and a flat-enough response to work with:

...

Its distortion seems to rise quite fast below 100 Hz, though:
fb = 25

The THD % comparison graph is from the 10" mid-bass thread by member OscarS. The 10G40 sticks out as being the worst, but I remember he said that might have been rattling inside his test box, so it's possibly a measurement error. (I haven't gone back now to find the post again.)


By eyeballing the FR of the 10G40 in the datasheet it may look fine, I've traced it in Vituix, then it looks much worse, but then again eyeballing the FR and comparing it to other woofers in Oscar's thread I think it actually looked one of the best to me. So I wonder.

Last edited by mjvbl; 2nd December 2021 at 07:33 AM.
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Old 2nd December 2021, 08:54 AM   #53
Zvu is offline Zvu  Serbia
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Quote:
Originally Posted by fluid View Post
Two things to consider out of this that is relevant...
I couldn't agree more...
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Old 2nd December 2021, 12:44 PM   #54
sheeple is offline sheeple
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Originally Posted by Zvu View Post
Attachment 1001862

I think that we can safely conclude that Peerless HDS is dead while B&C 10PLB76 is in linear excursion down to 35Hz.
To what frequency do you guys usually keep the woofer within linear excursion (xmax)? This morning, I made some SPL tests at my LP (2.7 meters from the speakers). I measured with Z weighting and peaks would reach 95 to 98 dB, while maximum was usually around 80 dB only. Depending on music, naturally.
Miles Davis 'So What' was very loud at this levels, while for equivalent loudness impression, Drum & Bass would need higher levels, as there is more information in the bass spectrum. When mid and high frequncies matched instrumental music, the meter would easily exceed the mentioned peak levels. Same goes for amplified music with bass guitar, like Fugazi (i.e. 'Closed Caption' on Instrument Soundtrack).

But RTA says below bass, <80 Hz, there is much less energy. For the aforementioned Fugazi song, i.e. the sub bass is 20 dB lower than bass. This got me thinking to which frequency I should think about keeping within xmax, and where xdam should be the limit. Until now, I always used 20 Hz as my lower limit, but to keep within peaks to 20 Hz, a high pass that introduces group delay becomes necessary.
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Old Yesterday, 12:06 AM   #55
fluid is offline fluid  Australia
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It is very hard to know what values to use for xmax as many manufacturers specify them differently. xdamage xmech should never be a target.

Klippel results for drivers are good because they show how the motor force, compliance of suspension and inductance change with coil position. Many drivers are quite nonlinear well below their rated xmax often due to the suspension used. B&C and 18Sound in particular have some incredibly linear drivers.

This is from B&C's FAQ on their website

"Thiele – Small parameters have become the universal language for describing loudspeaker behavior in the small signal domain. Nevertheless, they comment little on the working limits of loudspeakers in the large signal regime.

These limits are customarily indicated by Xmax, the maximum linear excursion. This value is typically measured according to the AES2-1984 standard, corresponding to a maximum of 10% total harmonic distortion (THD) with a sinusoidal signal (though most manufacturers, including B&C, now typically provide data for Linear Mathematical Xmax, not measured Xmax). Recent research shows that this method can yield ambiguous results, and even different numerical values for the same loudspeaker. The main limit of this measurement is that it looks at the output signal instead of the physical features of the driver itself. On the contrary, the most up-to-date instruments for distortion analysis can measure the variations in loudspeaker parameters when they are fed with high-level signals. In this way, an excursion limit can be fixed, beyond which the parameter’s variation becomes excessive.

The “X var” value reported in our data (generally after the traditional “Xmax” value) is measured this way. Beyond this excursion limit, the magnetic field seen by the voice coil, or the total suspension compliance, or both, drops to less than 50% of their small signal value, producing high distortion levels, strong variations from small signal behavior and power compression. The new technique yields different results from the standard measurement based on THD. B&C Speakers believes that this added information gives a more accurate and reliable description on loudspeakers behavior in actual operating conditions."


Jeff Bagby's Woofer Designer program is still a really good way to look at different drivers if you have a version of excel that it works with. It is still on Charlie Laub's site.

That has a section for Linkwitz Transform and a lot of other basic EQ functions that can be switched in and out to see the effect they have on excursion etc. It requires input of the parameters but that really only takes a minute or so and can then be saved in the database for later recall.

Lots of music has no content below 30Hz and I had a 30Hz switch on my old Orion crossover, on a lot of music I could not tell the difference between positions.

More and more music is being made with very low frequency content whether it is intentional or by accident using monitors that don't allow it to be heard. Now I have speakers that can reproduce it I like it and would not want to be without it.

Because of this vented systems that you intend to play loud often need a highpass to prevent this very low frequency content from causing wild excursions.

As far as group delay is concerned you might want to compare it to this set of graphs to determine if the group delay stands much chance of being audible.

https://research.aalto.fi/en/publica...haracteristics
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Old Yesterday, 09:46 AM   #56
sheeple is offline sheeple
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Thank you for the detailed response. I will just try it out, as I do have the impression that I have never hit any high excursions in my home listening, yet. Admittedly, I cannot see what the voice coil does. And while I strive for performance, in the case I'd use the speakers in another setting, I can still change DSP for this role.
I know the graph that you showed, and have always been wondering that it is in conflict with some other rules, like the max. half-cycle even below 100 Hz. But it does seem easy to conform to the limits which graph b imply: Most pro woofers have no problems in the 300-1000k area, even with a vented-assisted enclosure.
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Old Yesterday, 10:52 AM   #57
Zvu is offline Zvu  Serbia
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I like to know what is Xmech/Xlim/Xdamage in a woofer i'm using. It is virtually impossible to keep the cone movement in linear mode all the time down to 20Hz and some music and movies have sudden impulses very low in frequency and high in level. I can simulate in Winisd what is maximum volume achiavable without any damage to the woofer.

That baing said, i'd make hipass filter at 20Hz a mandatory option for all amplifiers because of modern music and movies production. Ironically, amplifiers of 70's up to 90's had that in form of subsonic filter (used when listening vinyl records). I'm making passive crossovers in loudspeakers but would always dile in woofer protection in software since i'm using computer as a source 100% of time.
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