416-8B cabinet

[sidu]

Hello everyone!
I want to make cabinets for my GPA 416-8B woofers.
I found plans for Altec 620c wich is good for me because of its size and how it looks.
I want to put on top 511s with 802-8Gs and I also try 32C. Crossover N1201-8A wich I will be building soon when parts comes to me.
Do You Guys has try 416/620 cabinet combination? Any thoughts?
I also find in Altec "AN-5 Customizing Altec Loudspeaker Enclosures" document, to change the port size, but specs are for Altec 416-8C, so I don't know how it compares to 416-8B.


I will be greatfull for help
Lukasz

[Sootshe]

Hello everyone!
I want to make cabinets for my GPA 416-8B woofers.
I found plans for Altec 620c wich is good for me because of its size and how it looks.
I want to put on top 511s with 802-8Gs and I also try 32C. Crossover N1201-8A wich I will be building soon when parts comes to me.
Do You Guys has try 416/620 cabinet combination? Any thoughts?
I also find in Altec "AN-5 Customizing Altec Loudspeaker Enclosures" document, to change the port size, but specs are for Altec 416-8C, so I don't know how it compares to 416-8B.


I will be greatfull for help
Lukasz


Hi Lukasz,
You could also try the Model 19 cabinets if the dimensions suit you.
You have the same 802’s as the 19’s & the 511 horn will sound better than the 811.
Your crossover is also very similar.

This is will make a great sounding system. Good luck with your project.

[sidu]

Hi Lukasz,
You could also try the Model 19 cabinets if the dimensions suit you.
You have the same 802’s as the 19’s & the 511 horn will sound better than the 811.
Your crossover is also very similar.

This is will make a great sounding system. Good luck with your project.

Unfortunately Model 19 is too big for me, why I choose 620 cabinet. Max width is 70-75cm.

[RMC]

Hi Lukasz,

The Altec 416-8B or C may look similar but they were optimized for different purposes. The B for vented box bass and the C mostly for bass horn loading. Of the 5 cabinets specified by Altec for the C version 4 of them are bass horns, that gives an indication (815A, 816A, 825B, 828G). Plus the 416-8C is not mentioned for the 620 cab.

On the other hand, a LF driver's efficiency is also a clue as to its intended purpose, higher number for sound reinforcement woofer and lower one for home hi-fi or monitoring woofer. The B has lower (1.76%) and the C has higher efficiency (3.3%). Btw, the B's 1.76% is a bit tricky. Sensitivity given is 98 db/1W/1M (measured 100-1000 hz), however Eargle's Loudspeaker Handbook half-space efficiency/sensitivity table gives 1.6% (closest) corresponding to 94 db. So below 100 hz you're likely to get around 94 db...

Another difference between the two is their driver Qts value: 0.323 for B and 0.26 for C. Other things being comparable, the former will be more "at ease" with larger box volumes, whereas the latter will show earlier dropping bass response as cab size increases. Finally, low Qts drivers are more often than not specified for horn use, not exclusively though.

Note regarding the modeling done for you, GPA used 8.8 cu.ft (also 6 cu.ft.), i calculated 8.9 for the 620 box, and some mentioned 9 cu.ft. for the 620B/C, so i shot in the middle at 8.9 to model since you liked that size. I did see that previously 7.5 cu.ft. was also mentioned, this might help the situation mentioned below re power input vs cone travel. Moreover, i used 2X3" vents since they exceed the minimum area recommended by the software and also have an easy 2" length (no fractions), plus 3" tubes are easily found.

Your speakers may be new but they're a reissue of an older Altec design and those older ones didn't have a lot of cone travel capability. This partly explains why the driver will hit Xmax at only 60 watts, as shown, around 40-45 hz (red dotted line is 4 mm Xmax limit, and red solid line is actual driver excursion). The Winspeakerz software used to do this quick modeling uses the RMS excursion value method (say sustained) whereas another software, like Win ISD, uses the PEAK excursion value. With the latter the results would be somewhat less forgiving, i.e. look worst in terms of power vs Xmax reached.

The other part of the explanation is this box is large and tuned pretty low. The driver might do better, power wise, in a smaller box tuned higher for example, but then you sacrifice some lower bass... Hope the above will help you. Regards,

Richard

EDIT: Note SPL shown on the graph is based on driver sensitivity (98 db). In real life the response curve may not be that flat based on the 94 db mentioned (Eargle's table), so below 100 hz or so bass frequencies may actually be lower than shown on the graph, therefore SPL numbers too.

I'm surprised the 416-8B tech sheet from GPA doesn't provide a full set of TS parameters (e.g. Le missing) and no driver impedance curve supplied.

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