Pass SLOB Build Discussion

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#562
Nelson Pass said:
curves for the Moth version of the SLOB.
Click to expand...

I've read and re-read the 2022 Speaker Camp pdf file, When I look at the Moth curves, I don't imagine the xover curves in this pdf. I would have selected filters to reduce the 5 - 10K hump with a center point of 7K, obviously I would have been so far off point. For me as a DIY'er, this always intimidates me and makes me very reluctant to experiment.

Any suggestions?
 
#563
Here are some measurements that I took with a UMIK1 in REW with 1/6 smoothing. First is just the Moth in the SLOB with and without EQ measured at 1 foot on axis. Pretty much looks like Papa's to me.
mothInSlob1footOnAxis.jpg

One thing I noticed, but didn't capture was that the highs drop off dramatically when measured off axis...as expected.

Then I measured one SLOB from the listening position with the woofer. I realize that this is too much bass, but I wasn't as concerned about the bass as I was the mids.
SLOBinRoom.jpg



I haven't had a chance to try the resistor is series with the speaker yet. I will also try putting cotton in between the whizzer and the cone. There is really only one thing that bothers me...Sometimes everything sounds great and then the vocals come in and it sounds harsh/distorted. Some vocals are fine...CSN is not so great.
 
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#564
You have in effect an inverse BBC dip, so not strange your vocals sound harsh. If the resistor trick doesn’t work, Nelson has both made the circuit he just posted that will probably fix your issues. Or you could try his FR EQ circuit available for pennies in the store.
 
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#576
wwschaff said:
I've tried a few different sources, CD's, two different turntables with MM cartridges.
-Main one is Pro-Ject Debut Carbon Espirit SB with 2M red Ortofon
-Schitt Mani and pearl 2 phono pre's.
-ACA-pre+, B1K, and Whammy as a pre
-ACA mini, ACA, Aleph J

I'll try to take some measurements this weekend, but it'll be my first time so we'll see if I can figure it out. I'll also try the resistor trick...the moth's are 12 ohms.

To state the obvious... there are two possible problems:
#1. there may be something wrong with @No 4 and my SLOB's/setups or...
#2. we just have a different personal taste and find full ranges difficult to listen to.

I wish I could verify #2 before spending all the time and money trying to figure out #1. Luckily I also have Klipsch Hersey III's which I can enjoy in the meantime.🙂
Click to expand...
There’s nothing wrong with the installation, it’s the inherent issue with full range drivers and physics……..the larger the cone, the more beaming and the breakup mode is lower in frequency, often right in the passband of most fundamentals. A 3-4” fullrange would sound MUCH better……but won’t extend low enough to work with the SLOB.

Your best alternative would be a dedicated midwoofer and tweeter………..an 8” mid to be precise and a an open back AMT.
I‘ve been doing my best to recommend the B&C 8pe21 midrange driver…….they added a circular profile close the dust cap that kills all breakup modes…….this driver is within +/- 2db from 1-4khz and the rolloff is buttery smooth…….proper tweeter choice and high pass filter , you could likely for go a low pass to this mid entirely. That, and it’s nearly 97db efficient on a baffle
 
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#580
nitsk said:
The point of having that slot is to make sure the front and rear waves don’t cancel out. How are you ensuring that for the front-facing woofer?
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This is why I’m asking. I’m not exactly an audio engineer 😂😉.

Not being glib:
I believe that’s the whole point of a baffle isn’t it?

But I guess given the competing angles of the backwave they’d cancel each other out in comparison to two woofers both being mounted on the same plane?
 
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