Vented box for GPA 416-8c

[allen mueller]

I've been thinking about building a set of vented boxes for my GPA 416-8c's. I would run the driver up to about 800-1.2K before crossing over to a 2" coax BMS driver on a Westlake style smith horn.

I have been doing allot reading about the Model 19 since it used the same woofer, but the GPA T/S parameters seem slightly different than the altec's parameters.

So far it looks like around 5 cu ft and a tuning of around 30 Hz might work well. This was using winisd. I have not probems going to a large box if needed.

Does any one have any suggestions?

The T/S parameters can be found here:
http://www.greatplainsaudio.com/downloads/416_8C.pdf

Thanks,


Allen

[grumpy]

Hi Allen,

suggestions? If possible, you might want to measure yours. I have some Altec
416-8C's I need to decide what to do with also, and modeling does seem to
indicate a smaller box (vs. 416-8B) -might- be a better match. I need to revisit
this with a WT-2 anyway... perhaps this weekend. GPA specs seem to indicate
an even further shift from the 416-8B (if one were to choose that as the "reference").

Sounds like an interesting combination you're cooking up -grumpy

[Zilch]

That's four of us, now, who have concluded that, at least according to the sims, the Model 19 box is too big.

[grumpy]

I'd rather say the Model 19 design implementation ended at a place that is
different than where I would start. No doubt they could have made the
effective bass enclosure smaller... and done so cheaply; so my assumption is
they achieved their intended response for who they viewed as the target consumer.

[allen mueller]

Thanks for the input guys. Unfortunately I don't have the luxury of testing to find the T/S parameters for my drivers, so at this point I will just have to go with the data from GPA.

At the moment I think that I’ll build a test box with a volume of 5.5 cu. ft. with a tuning of 35 Hz.

For starters I can use my Yamaha SP2060 to cross them over actively to get an idea of how the combo could sound.

Does any one else have recommendations as a starting point?

Thanks again,

Allen

[Zilch]

http://audioheritage.org/vbulletin/s...750#post200750

[ngccglp]

Hi,

If I use 511 horn instead of 811 for the the M19 cabinet, what should be the offset distance for the baffle that mounts the horn?

Thanks

[allen mueller]

http://audioheritage.org/vbulletin/s...750#post200750

Thanks Zilch, I had read that thread but missed the part about 7 cu ft volume, i think I'll give that a shot.

http://audioheritage.org/vbulletin/s...7&postcount=62

Winisd gives me a very simular plot, and port info, for 7 ft^3 and tuning listed in the post I linked above with the GPA driver.

Allen

[Zilch]

Hi,

If I use 511 horn instead of 811 for the the M19 cabinet, what should be the offset distance for the baffle that mounts the horn?

Thanks

The best way to make that determination is to measure with RTA. Find the location where the phase alignment notch at the crossover frequency is deepest, then reverse the phase of the HF driver.

Movements of the horn forward and back as little as 1/4" may be significant.

Given the wavelength at crossover and the depth of the horn, several optional locations will be apparent.

The measurement should be made with the mic at normal listening height and distance.

[Zilch]

Winisd gives me a very simular plot, and port info, for 7 ft^3 and tuning listed in the post I linked above with the GPA driver.

It's tough to know. Different tunings in different box sizes sound different, and who but a speaker manufacturer has the resources to determine what is "optimum" for a particular design objective.

Generally speaking, though, I believe experience has shown that what the box modeling programs suggest is a good starting point, independent of how they were used in the original designs.

Doing that, it would appear that M19's woofer would perform better than Valencia's in a Valencia box, and vice-versa, though I can't say good enough T/S parameters for 416A/Z are even available to make such a determination.

I'm not about to second-guess Altec's designs unequivocally, BUT....

[allen mueller]

Thanks for the help every one. Over the last week I've been working out different designs and layouts.

I have decided to abandon the idea of the GPA 416 in my project and have decided to go with JBL LE14H-3's. The first reason was box size, initially I didn't care, but when I came down to it, I didn't want a box that large. I am looking to scale down my current Altec VOTT setup. A 7 ft^3 box ends up rather large, compared to a 3.5 ft^3 box for the JBL. The second reason is there is lots of documentation on how to implement this driver in various designs, so I have a lot more to go on for the project.

I ordered them yesterday from JBL and they have a shipped today, can't wait. Once I get started I'll start a new thread.

Allen