Any interest in 8-3/4'' Aluminum Rivals?

Gowa

I may have an opportunity to snag some 8-3/4'' matte black aluminum Rivals. There's not many but I thought I'd see if there's anyone interested before I snag them.
They are priced $70 - $75 each (Below wholesale)
I will need to let him know on Monday.
  

rjj45

One pair for me, please.

BrannigansLaw

I'd take a pair or two of these I think... will we have a chance to see specs before pulling the trigger?

Gowa

I can't see them being too different than the last ones, although they are from a different company. He only has 3-4  pairs to let go.

BrannigansLaw

Gowa said:

I can't see them being too different than the last ones, although they are from a different company. He only has 3-4  pairs to let go.

Are there specs for the last one? I could only find an ACB ceramic/aluminum cone version

ani_101

this is one of the recent ones, but this is paper, the ones are here are aluminium - so the cone might be a bit heavier so probably lower FS, and higher breakup, but rivals are pretty well made for the price that Gowa is putting them here for and breakup is higher and more benign that comparably sized woofer.

https://diy.midwestaudio.club/discussion/1352/fs-8-3-4-drivers#latest

Gowa

I found this which may help. The specs may differ because of the OEM changes.

rjj45

Wow, those engineers and designers are awesome. Almost no breakup for an aluminum cone. 

Wolf

Read my mind, Don...

Gowa

I'm assuming that all things are equal that way. While the xmax is not large, I know this particular cone is quite light and preferred by the local companies that use them in their monitors.
There are some differences in specs from company to company. I'll measure one when I get them.
I just got confirmation that there's only 3 pairs available to me. Some other guy grabbed the balance.

BrannigansLaw

Count me in for 2 pairs, if there's 2 available

BrannigansLaw

Any luck getting one of these measured Leon? 

Gowa

There's nobody at their facility yet. Hopefully this week.

BrannigansLaw

Gowa said:

There's nobody at their facility yet. Hopefully this week.

gotcha, no rush, just checking in

BrannigansLaw

Any news on these?

Gowa

They are just getting back. I will head up there on Friday when things are quiet.

BrannigansLaw

Thanks Leon!

DaveFred

Yes, Interested.

Gowa

Well, it looks like he sold all the drivers to the guy who purchased his equipment. This makes me a little pissed because he said he would set aside 6 for me.
Sorry guys.

BrannigansLaw

Aww that's a bummer. Thanks for trying anyway Leon. 

Gowa

Are these 8-3/4'' black aluminums any good?

BrannigansLaw

what are we looking at there Leon? Is it the drivers we were talking about that got snatched up, or a different variant? 

I'm not confident in my ability  to draw conclusions from impedance plots alone so will leave that to the more experienced here..

Gowa

There are variations on this driver depending on the company I get them from. 

ani_101

I would suggest you plug in the T/S specs into unibox and see if the box alignment/size and tuning work for you. Usually the rivals have a very well behaved top end compared to some sized drivers and cone material and breakup well controlled leading to supporting higher XO, though since these are 8", 1800hz is about the best dude to bracing, so a robust tweet, best in a waveguide or 3 ways is good.

I can't read specs either, till I model it....

Gowa

There's a bit of disturbance at around 1.1k where the 2nd rises. Otherwise it looks pretty good. The company used the Morel EM1308 as it's mate.

ScottS

I like those parameters.  Sealed F3 of 53-54 Hz in about 1.5 cu. ft.  A variety of vented tunings also work.  I would think about taking the sealed box above and adding a low-tuned vent (around 29-30 Hz). 

BrannigansLaw

ani_101 said:

I would suggest you plug in the T/S specs into unibox and see if the box alignment/size and tuning work for you. Usually the rivals have a very well behaved top end compared to some sized drivers and cone material and breakup well controlled leading to supporting higher XO, though since these are 8", 1800hz is about the best dude to bracing, so a robust tweet, best in a waveguide or 3 ways is good.

I can't read specs either, till I model it....

Thanks Ani. I can model of course but that just tells me if it's useful in a box size I may want, how loud and low it can play with how much voltage, etc. All useful, but without FR and distortion I don't have a sense of what FR range I'd want to use it in... Not a complaint at all, just suspect there may be a way to glean this from impedance curve (aside from obvious glitches or kinks), but it's beyond me how. 

BrannigansLaw

So if I read that distortion graph right, it looks like it's <0.1% 2nd and 3rd order from 100-400ish? at 90db spl? Looks pretty damn good, little bit better than say this SB I have been looking at:

http://www.audioexcite.com/wp-content/uploads/2017/11/SB23NRXCS45-8-1-20cm-90db.jpg

That is, if I'm reading these right, and measurements conditions comparable. Trying to learn

ScottS

I'd be careful using the distortion data to compare this driver to the SB driver, as they may have been measured using different drive levels.  As Leon mentions, the 1.1 kHz distortion peak is 2nd order, which is going to be less objectionable than a higher order distortion peak.  As you've observed, the optimal operating range appears 500 Hz and down.  It's a little worse from 500-800 Hz, but likely still pretty good.  Whether it will work well in a two way would depend on how objectionable the distortion peak is. Once you get past that, the next issues are the dip at 3 kHz and breakup around 6 kHz.  That's pretty good behavior for a 8"+ Aluminum woofer. 

BrannigansLaw

ScottS said:

I'd be careful using the distortion data to compare this driver to the SB driver, as they may have been measured using different drive levels.  As Leon mentions, the 1.1 kHz distortion peak is 2nd order, which is going to be less objectionable than a higher order distortion peak.  As you've observed, the optimal operating range appears 500 Hz and down.  It's a little worse from 500-800 Hz, but likely still pretty good.  Whether it will work well in a two way would depend on how objectionable the distortion peak is. Once you get past that, the next issues are the dip at 3 kHz and breakup around 6 kHz.  That's pretty good behavior for a 8"+ Aluminum woofer. 

Thanks for the analysis! Helps me to know if I'm looking at things right. I've definitely noticed that the measurement conditions make a big difference - audioexcite (above) does distortion tests at 90 and 95db, but measures close to nearfield. Hificompass does distortion at 315mm and nearfield, and the results are often different. Can't recall if he does multiple levels too. But it's definitely hard to compare to other measurements because most people don't give their conditions. For tweeters it's even worse, sometimes there's a little footnote along the lines of *tweeter was highpassed at 1500hz 2nd order for distortion measurements*, which is all well and good, but then not every tweeter on the site gets that same treatment, so you can easily jump to wrong conclusions comparing to another that was run wide open.

Gowa

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