SB17CAC burned in : any T&S .frd .zma please?

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#23
Scottmoose said:
Re DATS v.3 it can put out up to a maximum stated 11.4dBu (open the oscilloscope & adjust the Z sweep amplitude at the bottom left -it applies to the Impedance Analyser mode also; why they had to bury it there I don't know). 11.4dBu, if my maths is correct, equates to a nominal 2.878v RMS. Standard level is set to 10dBu. Since to the best of my knowledge there is only one way of converting dBu to vRMS, either it's got a higher output than often noted, or some form of unstated 'equivalent' extrapolation is going on. I wouldn't like to say which, I haven't tried physically measuring the output level myself, although out of interest I'll try at some point as I have one on the shelf.

Either way, I've measured a number of the CAC units at 8 & 4ohm persuasions & obtained relatively similar results to Audioexcite etc. in T/S terms with the aluminium cone models. Pair matching is typically good, Fs usually within target production tolerance, Q usually higher, Vas lower than published. I'm not in a position to upload the data as it was not done in a DIY context; however, I'm impressed with the quality of the CAC drivers.

T/S data is not fixed -it varies a little, even after break in with VC and ambient temperature, so expect some differences in the same drive units measured on different days or in slightly different conditions.
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Interesting choice of voltage, that roughly corresponds to 1W on a 8 ohm load (2.83V). Would be quite decent loudness especially in bass.

I have thoughts of rigging up my vector analyser to an amplifier and add a 0.1 ohm resistor to ground to measure impedance via a voltage sweep. Haven't tried that yet, but it will give a true representation of things in box tuning at real listening levels.

Oon
 
#24
I have been working with my DATSv3 this afternoon... I see the menu option to adjust the output up to a max of 11.4 dBu. When I measure the output into on open load, it does generate more than 2 V RMS. However when it is driving a 4 ohm woofer, it only gets to about 0.19 V RMS.

Regardless, I don't see this as much of a problem. This small piece of equipment is really slick for what it does and what it costs. I am quite pleased with how it measures drivers, inductors, caps, and complete systems.
 
#25
I have been working with my DATSv3 this afternoon... I see the menu option to adjust the output up to a max of 11.4 dBu. When I measure the output into on open load, it does generate more than 2 V RMS. However when it is driving a 4 ohm woofer, it only gets to about 0.19 V RMS.

Regardless, I don't see this as much of a problem. This small piece of equipment is really slick for what it does and what it costs. I am quite pleased with how it measures drivers, inductors, caps, and complete systems.
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i think it is of interest if a package is worth its price, i would like to think that dats should be a lot more powerfull and accurate then a low cost soundcard combined with arta or rew and one 10ohm resistor, but this do not seem to be the case. since the dats package lacks basic hardware specifications there will always pop up questions regarding this
 
#27
i do see the benefit for a product like this, i have thought many times of buying one for myself, but each time i have looked it up i miss some specifications and then wondering if it is going to give me better results then rew or arta

have you done some comparsions to rew or arta or maybe clio pocket with a driver like sb17cac?
 
#28
Hi,


as it's an open discussion, wanted to ask you if one should avoid to putt a 4 ohms tweeter above a 8 ohms in a passive loudspeaker mono amplified, please ?


Does it impact phase much in a 3 k hz crossover or I just have t care from the slope order for phase ?
 
#30
No I'm working on a little casual compact three way for small room and relative low listening spl. (which mid bass will be 90% the sb17cac and the mid is already on shelves: ScanSpeak 10F/8ohms)


the mid will handle something like 700 hz to 3000/3500 hz and is 8 ohms. Question is should I glue to 6 or 8 ohms tweeter for the 3500 hz and above or will a 4 ohms tweeter will not affect too much a second order slope with the 8 ohms mid ? (passive XO-second order planned)


I now people use for instance a 8 ohms tweeter driver with a 4 ohms mid sometimes, but if I will stay nearer from a good job, must I pick up a 8 ohms tweeter here ?
 
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#32
diyiggy said:
No I'm working on a little casual compact three way for small room and relative low listening spl. (which mid bass will be 90% the sb17cac and the mid is already on shelves: ScanSpeak 10F/8ohms)


the mid will handle something like 700 hz to 3000/3500 hz and is 8 ohms. Question is should I glue to 6 or 8 ohms tweeter for the 3500 hz and above or will a 4 ohms tweeter will not affect too much a second order slope with the 8 ohms mid ? (passive XO-second order planned)


I now people use for instance a 8 ohms tweeter driver with a 4 ohms mid sometimes, but if I will stay nearer from a good job, must I pick up a 8 ohms tweeter here ?
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yes it is very common to use drivers of different ohms in a loudspeaker, and i do not see any problem with that, you just deal with it in the crossover like you deal with different sensitivities and different frequency responses
 
#33
Many thanks.
I believe I am mixing up phase alignment and electrical impedance in the context of a passive crossover loudspeaker monowirered... Well I assume at the end the phase is so much angled in the crossover cut-off than it doesn't matter too much...


Well, I believe I pull the trigger on the cac17-8 ohms hopping it can outputt at least 86 db spl at 700 hz ! Hopping the bafle step will not drop 6 db at 100 hz with a 20 cm width front bafle !


Thanks again gentlemen for the answered question.
 
#34
For an approximate nominal -3dB baffle step frequency, take 4560 / baffle width in inches. Baffle Diffraction Step So for a 200mm [7.87in] wide baffle, you could expect the F3 of about 579Hz. This is an empirical formula, but it gives a rough guide.

The SB17CAC35-8 is officially rated at 86.5dB 1m/2.83v under anechoic conditions on an infinite baffle without step loss. So you may [may] just about have 86dB at 700Hz, notwithstanding any other diffraction effects etc. You can do the maths for yourself regarding 100Hz from the above; it's an approximately 1st order effect to -6dB. Put it this way -you'll be very lucky with such a narrow baffle, although boundary gain may help a bit.
 
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#39
diyiggy said:
Many thanks.


Yes, important as I would work with the -8. and want a small enclosure for a very compact 3 ways where the unit will handle the low it is able to till 650/800 hz. My understanding is there is much more bafle step in the 600 hz area than 800 hz in the surface I want to work with (20 width and up to 40 height)... I have a doubt of the spl at 2.8V the driver can exhibit in the cabinet at the cut-off frequency I plan (ideally 87 db/2.8V for the mid it will work with).



Which datas should I simulate from Goran please, right or left window ? (horizontal or vertical added mass method).


greetings once again DIYIGGY!

I still haven't gotten the hang of REW or ARTA but have been slowed down by recent events. I do have the SB17CAC35-4 pair back in test boxes again. I have sold my Satori MW16 pair and am playing with new 17CAC ideas. The 4 Ohm seems to do well in 7 liters or larger closed and 16 to 18 liters vented (or larger).

Has anyone done extensive testing on the 4 Ohm version? Please point me to that data if available.

Thanks,

[PS, these 17 CAC's are also up for sale; I will pay shipping but only the continental USA, see the SWAP shop for more details]


I saw Madisson advised 0.5 cf>3 for a 45 hz f3 which is great but I believe this is from the Vas, Fs & Qts of the datasheet... Am I correct to doubt of such datas after few months of use ?
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#40
Hi Oldspeakersguy,

How fine those days 🙂

Looks like the sb17cac/4 is 91 db 2.83V able... but wow so low volume...

The few I simulated with Jeff Bagbys's Excel : gave me something nice, even as bass driver for a small room. The fun is it seems it can be loaded in a vented which can be sealed by a cork to make the -f3 + 10 db circa... -without the room gain and all of course-

Problem for me is the 4 ohms seems a little too high to meet my mid driver at 700 hz which is 87 to 88 db 2.83V and the CAC 8 ohms too low with its 86 db...

According Scottmoose input and The Edge, the baffle step around 700 hz should be not bigger than -0.5 to 1 db in the baffle size of a classic monitor.

I could choose the 4 ohms and put a L//R for BSC and lowisch 2 db around 88 db the 700 hz planned cut-off. but values seems huge with a coil at circa 2 mH and a resistor at more than 8 ohms... I fear it kills all the dynamic behavior of the bass driver which has already not a big Sd for bass... whatever it's planned for a 10 square meters to 15 square meters room !

I hesitated with the Audax HM170ZO which is a 91 db 2.3 spl but its Vas is a little big on the datasheet and I have no real life datas for it. Simulated with the flater BR response, cabinet is 15L -which is eventually ok- with a -F3 @ 57 HZ... -f10 at 42 hz (without room gain I assume)... It's a little short, as I surmise not having more than 5 dB at 40 hz and also the BSC will have huge L and R ! a 20 l enclosure gives a little better low end below 40 hz... but here the room will rule the loudspeaker, so...

So the unknown factor is how the bafle step will react in real life and in room as I believe the behavior in a small room with all the close surfaces shows not a 4Pi... Perhaps I shoul bet on a -3 to -4 db shielving only... dunno ! Zero experience there 😀 !

The Audax will be a faster transcient and drier driver I think while I have no doubt the SB is more versatile but its highest break-ups that can bother and has lower HD by far I surmise vs the Audax. Audax has a stronger motor, a one layer voice coil, an interresting reversed surround but at the end exhibit even more break-ups in the mid where I plan to cut-off and has a poor low end as I think it is more a mid driver than a mid-bass driver ! So the choice is a little like a Bidrump or a Trumden at the end 😀 as I have to do something with the 8 ohms ScanSpeak 10F/8424G00 (budget doesn't allow some cool Wavecors that has very low HD but poor efficienty or cool expensive other ScanSpeak !)

SB made a great driver with the NBAC and CAC series, for the price...it can not be beaten ! 🙂..and permit small cabinet. There is a guy from NYC I believe that made a cool Monitor with it a flat mid and a tweeter from Raal... it had very good reviews : Philharmonic Audio
I plan a simplier sort of (no square wave load) with cheaper cost on the tweeter (and lower size for nearer c2c) and I like the mid of the ScanSpeak 10F : very neutral and a lot of details according my ears/tastes.

I'm sure the Rohacell from SB is good as well but seems too much hard to work with for a beginner as I...

I'm sure it will end with the CAC ! Because the Vas constraint.
 
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