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cubo15 vs tham15, measured

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Tonskulus View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2019 at 8:17pm
Ok, going to try some more serious drivers for cubo asab.  15lw2400 has very nice specs indeed and should work in extended cubo. 

I just spent an hour or so trying to get better sound from cubo for my taste (DSP and EQ work) and now its much better / flatter. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2019 at 8:27pm
Please bear in mind these graphs need adjusting if one of the drivers is 4 ohm nominal and the other 8 ohm.

Also measuring this close to the mouth gives false results, ideally you want to be at least 3-4x the longest cabinet edge away to try and avoid being ‘in the horn’ or having the baffle size influence the results.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 15 October 2019 at 8:42pm
Originally posted by toastyghost toastyghost wrote:

Please bear in mind these graphs need adjusting if one of the drivers is 4 ohm nominal and the other 8 ohm.

Also measuring this close to the mouth gives false results, ideally you want to be at least 3-4x the longest cabinet edge away to try and avoid being ‘in the horn’ or having the baffle size influence the results.

I know, going to make open field outdoor measurements soon (10meters / 28.3volts) which is my standard method.
I usually dont care if the driver is 4 or 8 ohms especially if comparing different drivers (except the load for amp or when designing passive crossovers), overall pass band sensitivity is the thing to look for.  Thats why I never adjust curves for drivers having different impedances or DC resistance but I do mention it if necessary. So just add 3dB for 4ohm driver if you want to :)







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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 16 October 2019 at 7:04pm
Further investigations.  
I have two versions of L15P540, old and new (almost brand new actually). Old version has smaller vent hole and less ribbed cone (4 vs 5 ribs) but they work. 

I measured thiele small parameters and frequency response in Tham 15, and there seems to be differences - actually quite a lot! Check this out.


Left: old used one, Right: new.  New one has good match with manufacrurer specs. 





Impedance curvers, bare drivers, blue is new and red is old version):




Freq. Response (green new, orange old):



I'm not sure what's going on there, why old version has much lower Qts?  New version has anyway better performance in Tham as can be seen. 




Edited by Tonskulus - 16 October 2019 at 7:12pm
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 17 October 2019 at 1:06am
You are comparing an old driver versus a new driver. The older driver has been used more and broken in thus, the differential in the Qts & fs. Its like buying a brand new pair of shoes of the exact brand in addition to model number and wondering why the older shoes feel more comfortable.

Your limiting factor is not the speaker but, more so the enclosure. The loudspeaker cannot give you more for the cabinet does not meet the requirements needed for the loudspeaker to deliver an extended frequency response.

This is why TS Parameters of Loudspeakers are measured in Free Air as the loudspeaker is not restricted  by enclosure limitations. The vast majority build cabinets too small for the loudspeaker. This is why every large loudspeaker placed in a small enclosure requires a lot of equalisation and use a lot of excursion to deliver those lower notes at a significant sound pressure level.

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Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 17 October 2019 at 5:41am
Yes, it is known phenomenon that parameters will shift over time - more or less. 
Some manufacturers actually gives parameters for "broken in" drivers and it makes sense - depending how long does the driver take to mostly "break in".


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 17 October 2019 at 7:56am
Just remember the fs, Qts and, VAS are the most important figures when designing a box. Nothing has changed in 50 years. Get a good understanding on how those symbols dictate the overall response of a loudspeaker in an enclosure and, you will be far ahead of the majority of Do It Yourself builders on the Internet.

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Elliot Thompson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 17 October 2019 at 8:52pm
Yes I do know those things pretty well but you never know how much parameters will shift over time..more or less and this makes some confusion for design progress and simulation. Thats why I measure parameters after break in progress to be used with sim software. 

Anyway I need to look for more 15" drivers to be measured with different cabs like Tham.  15TBX100 seems to be a good candidate, or cheaper alternative 15PS100.

Short video, tham in action, low power but there was good amount of bass!












Edited by Tonskulus - 17 October 2019 at 8:55pm
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Elliot Thompson View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Elliot Thompson Quote  Post ReplyReply Direct Link To This Post Posted: 17 October 2019 at 10:02pm
A Speaker will only loosen up based on its environment. If you are swapping a speaker in different boxes on a constant basis, that speaker will break in according to the box that gave the loudspeaker enough room to move freely.

If you are looking for a speaker that offers minuet deviation from it's published TS Parameters look to wards Eminence or the old Made in England Celestion.

B&C, Faital Pro, Electro-voice, Beyma, Fane, in addition to, RCF drivers will offer significant changes on their Parameters once measured in free air based on my experience.

You should also focus on one design and disregard the one(s) that do not meet up to your requirements. If the tham 15 gives you what you are looking for from a tonal standpoint, you do not need to focus on the cubo 15. Get rid of the cubo boxes and build more tham bins. Don't get caught up spending a lot of money on drivers to band aid a box design in which, all in all you really do not like the tone it projects when, you have a next design that satisfies your tonal requirements.

Best Regards,
 


Edited by Elliot Thompson - 17 October 2019 at 10:04pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 18 October 2019 at 6:09am
Yep. Overall Tham15 is one of the best for my needs. Cubo might be louder but its also bigger and tonal characteristics are not so good to my taste. 
I have designed two ml-tqwt enclosures for 4 and 6" full range drivers and they are amazing.  The openness and good integration of bass frequencies with upper band is so good.   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bob4 Quote  Post ReplyReply Direct Link To This Post Posted: 18 October 2019 at 9:53am
Big up for sharing your findings Tonskulus, the forum has become awfully quiet nowadays.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tonskulus Quote  Post ReplyReply Direct Link To This Post Posted: 18 October 2019 at 4:43pm
Yes, I have noticed the same. 

Just punished my tham15 @ 1kW of power, oh my.. it slams hard!  And it has much better cone load compared to cubo. P540 was not happy in cubo (over excursion and flapping etc) but no problems in tham.  Brutal thing being so small but requires careful EQ settings.


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