High Efficiency Speaker Asylum

RE: Altec 416-8B Midwoofers: Recommended Subwoofers?

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tomservo

In Reply to: RE: Altec 416-8B Midwoofers: Recommended Subwoofers? posted by cin5 on September 28, 2024 at 10:28:04

Well, it will make sound but it is a low mass driver and best used in a large cabinet so in a 3 cu/ft sealed box, the -3dB low end would be around 175-200Hz. A vented box that small is less suitable for that driver.
Can you use a different driver to get down to the sub (like down to say 80Hz)?

Follow Ups:

RE: Altec 416-8B Midwoofers: Recommended Subwoofers? - cin5 22:12:18 09/29/24 (0)
Thanks tomservo and Paul Joppa for chiming in. No, I can't use another driver. My DIY skills are very limited and with my day job and other commitments no time to improve upon them. Back in 2015, the cabinets were designed by DIYaudio.com member Gary Dahl for his two-way system plus
subs. Gary gave me the sketches and two dozen photos for Jim Salk to clone them. I ordered the 416s from GPA and had them shipped to Jim. Back then they sold for 1/4 of what they do now. https://greatplainsacoustics.com/products/416-8b-alnico-16-in-low-frecuency-loudspeaker-each?srsltid=AfmBOooJNHFXcc30wFxcfNjHrTE-0Fi4hG0JufbYqJIHDmDRHDuEgzsG
Scroll down and see specs and T/S parameters.
AFAIK, Gary uses vintage Yamaha JA6681B drivers in JMLC AH425 horns atop the Altecs. See his last posts on this page. https://www.diyaudio.com/community/threads/beyond-the-ariel.100392/page-761#post-7412544
Gary seems elated by the sound of the Yamahas; lets hope he doesn't lose a diaphragm as there are no replacements to be found anywhere. And he has long been equally pleased by the Altecs, which, so as to minimize IM distortion, he deliberately designed those small sealed boxes to limit usable response down to 70Hz. However, Gary never specified what SPLs vs. distortion he gets at that frequency, vs. the 73db distortion from the ~ 95db test at 100Hz Troy Crowe measured. But checking the last three plots here attests to this driver's very low distortion numbers.
https://josephcrowe.com/blogs/news/altec-416-8b-in-100l-sealed
One of Gary's very last posts said that he only uses the subs for home theater. For music, he claims to get ample bass response from room gain due to fortuitous speaker placement. I doubt if I will get that lucky in my room, hence my questions about using the Rythmik subs. I don't know quite how to interpret the 416's T/S numbers to go about proving this, but Tom Brennan at audiokarma.com member said that "I don't know but whatever subs you get should be able to track the dynamics of the 416s, no easy task." That got me wondering if Gary's subs ((16" Acoustic Elegance drivers + passive radiators) were too slow for the Altecs. If so, from what I've read of the Rythmik subs there will be no such issues.
Therefore, my main concern is if there will be any big tonality differences between the 416s and these subs if I'd have to cross at around 80Hz. I suppose the only way I could cross lower would be if I was satisfied with SPLs from the Altecs at ~ 70Hz in my 2660 cu ft room, however likely that would be. Equal-loudness contour - Wikipedia

Edits: 09/29/24
RE: Altec 416-8B Midwoofers: Recommended Subwoofers? - Paul Joppa 12:56:26 09/29/24 (1)
It's a light cone, but a very floppy suspension.

FS = 24

QE = 0.24

Vas = 22.9 ft^3

Unless I'm missing something, I get 70.5Hz for f0 in a 3 ft^3 box, at QE=0.705; very close to Butterworth. (I'm ignoring QM which is pretty large). If I'm right, it would be a pretty good match for the Rythmik F12.
- RE: Altec 416-8B Midwoofers: Recommended Subwoofers? - tomservo 17:30:43 09/29/24 (0)
  It's low mass for sure, I got a 0dB point at 160Hz and -3 at 74Hz in 3cu/ft. The 2.5mH L gives the response a built in low pass crossover. Parameters "as if made for a large low compression bass horn" haha
  
  But with twice the box volume and tuned to 40Hz a vented system could give a -3 at 40Hz, with 3 times the volume, you get a small bump and -3 at 36Hz.
  
  The right bass horn is where that one would be happy.

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