Altec 416-8B Midwoofers: Recommended Subwoofers?

[ajant]

I sent my pair of GPA Altec 416-8B to Troy Crowe for testing.
https://josephcrowe.com/blogs/news/altec-416-8b-in-100l-sealed

As you can see, due to the sealed box size at around 70Hz they probably won't play at much above 80db, if that much, at 11 feet away.

I thought of getting a pair of these subs. https://www.rythmikaudio.com/F12SE.html

But until Troy Crowe builds the rest of the system-probably using this horn https://josephcrowe.com/products/3d-cad-files-horn-no-1994-es450-biradial-for-jbl-2446-2-throat -I will have no idea how well the Altec midwoofers and the Rythmik subs will sound together.

Would it be a mistake pairing the Altecs with these Rythmik subs?

 

[Three quid]

Yeah that cabinet is undersized for the 416. I think Altec recommends at least 8cu ft tuned to 25 Hz. I have 416's in vented 9 cuft cabs and get good bass to around 35 hz.

Can't comment on the Rhthmik sub, but you'll need something fast and tuneful to blend with the Altecs. Rhthmik has a 45 day trial period so plenty of time to try to dial it in.

 

[Kingrex]

Make your own subs. Best I have heard are 12 inch 4 ohms Daytons in a sealed box with a krell KSA 250 driving them. Owner made a stacked pair and wired each pair of 4 ohm to be 8 ohm to the amp. He is using ORC to control them. You could use an Ashly Protea to dial them in.

These are way better than the SVS and REL he has. Very fast and articulate.

 

[SlapEcho]

Agreed on making your own, especially since your trying to mate to Altec drivers that already have low Q params in a sealed box. The issue is that most sub manufacturers must make compromises on design between power handling, total acoustic output, and apparent speed. By making your own you can tune to what works best for you(you've already made custom midwoofer boxes), in your case I assume articulate and fast bass. I went with Dayton 10" drivers(preferred parameters) with a box Qb of ~.55. I'm using a Mark Levinson 332 amp(prefer class A - A/B over class D, H, etc, for low bass) and parametric Velodyne crossovers for each channel. With room gain, it extends to 18Hz with decent output at 16Hz. It is extremely articulate and surprisingly deep(more so than any commercial version i've heard). In going with that design I'm sacrificing more acoustic output, but then again, I'm not looking for 120dB output at 20Hz either.

 

[ajant]

I was well aware that the 416 was designed to work in ported cabinets, though as I recall from an Altec datasheet that bass down to ~ 35Hz was said to be attainable in a 7 cu ft sealed cabinet. But despite my limited knowledge and DIY skills, when these were built in 2016 I was following the lead of fellow diyaudio.com member Gary Dahl, who in pursuit of reducing distortion to very low levels (as shown in Crowe's test report) put the 416s in those sealed 3 cu ft boxes to limit their low end response, but then extend system response using Acoustic Elegance subs/passive radiators. His system as of 2018. https://galibierdesign.com/wp-content/uploads/wa-trip_gary-d.jpg

Gary shared his cabinet sketches and numerous photos of cabinet bracing and other details so Jim Salk could clone them. Jim also built my Rythmik subs.

Salk Sound

www.salksound.com

I recently heard that Gary 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.

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 (~86db?) SPLs from the Altecs at ~ 70Hz in my 2660 cu ft room, however likely that would be. https://en.wikipedia.org/wiki/Equal-loudness_contour

​

 

[SlapEcho]

The problem is the bass alignment you currently have with the midbass box/driver. Running box alignment software would be more telling, but just looking at the TS params is and box size is indicative of the "tight" bass you would get. I would surmise that this may be problematic with most conventional subwoofers in the market especially at higher crossover frequencies.

Sealed box Q's generally are low at higher frequencies, slope up as you approach the resonate frequency(fs) of the box/driver, and flatten out towards the lowest frequencies.
The subwoofer has its own Q profile. What is preferable is try to avoid integrating a sub with a much higher Q than your midbass at crossover frequency as to avoid the apparent mismatch between a speedy midbass and boomy subwoofer.

I can't speak to Rythmic either but my understanding is they have servo driven subs and I thought I had read somewhere they have true Q control, allowing change of the perceived driver speed. Assuming it allows you to drop the Q's to low enough values, this would be advantageous for your specific application. I would go sealed sub as well but the only way to find out for sure would be to try it out.

 

[ajant]

In going with that design I'm sacrificing more acoustic output, but then again, I'm not looking for 120dB output at 20Hz either.

Same here. And even with a triangular ceiling that peaks at 11 ft my room is only ~ 2660 cu ft.

What is preferable is try to avoid integrating a sub with a much higher Q than your midbass at crossover frequency as to avoid the apparent mismatch between a speedy midbass and boomy subwoofer.

I can't speak to Rythmic either but my understanding is they have servo driven subs and I thought I had read somewhere they have true Q control, allowing change of the perceived driver speed. Assuming it allows you to drop the Q's to low enough values, this would be advantageous for your specific application. I would go sealed sub as well but the only way to find out for sure would be to try it out.

Thank you for this studied analysis, and which gives me some cause for hope. Please see attached and T/S parameters vs. the 3 cu ft sealed box, which owing to my lack the DIY skills and the cost of making those cabinets I must use as is.

But the Rythmik F12 sealed sub's design seems to ensure that slow and boomy bass can't happen. https://www.rythmikaudio.com/technology.html

https://www.rythmikaudio.com/download/XLR2_sealed_quickguide.pdf