416B or 515C for front loaded horns?

[thewings]

Planning to do a straight front loaded horn from either 70 or 80 hz up to 400 Hz. This is a non-vented horn.

I'm wondering which would be the better choice a 416B or 515C? Great Plains sell both versions and T/S for both look suitable. Thanks

[berga12]

I've experience with both, IMHO 416 it's better if you use him till 500-800hz range, this driver have a wonderful midrange response, I would use 515 for better bass and "cupe" sound below 400hz

if you see Altec project they use if I remember well longer front loaded horn with 515.

where you would like to tune your horn? and cross with a 10/12" or a 2" driver?

[thewings]

I've experience with both, IMHO 416 it's better if you use him till 500-800hz range, this driver have a wonderful midrange response, I would use 515 for better bass and "cupe" sound below 400hz

if you see Altec project they use if I remember well longer front loaded horn with 515.

where you would like to tune your horn? and cross with a 10/12" or a 2" driver?

I don't need the Altec driver to cover more than 400-450 Hz, I would be crossing with a large format compression driver above it, 2" or 3" exit.

[Horn Fanatic]

Planning to do a straight front loaded horn from either 70 or 80 hz up to 400 Hz. This is a non-vented horn.

I'm wondering which would be the better choice a 416B or 515C? Great Plains sell both versions and T/S for both look suitable. Thanks

The 416 by no means is suitable for horn loading for a number of reasons. The 515 was specifically designed for horn loading, but keep in mind it requires a minimum of 5 to 6 cubic feet of enclosure volume.

Those who believe the 416 is fit for horn loading know little of horn design. The 416 is best suited to be loaded into a 9 to 12 cubic foot bass reflex enclosure for the best bass response.

"Planning to do a straight front loaded horn from either 70 or 80 hz"

Then your horn should have a flare rate of .0324 to .0370 if you plan to limit it to 70 or 80 Hz. Proper horns are designed for a flare rate of one octave below the lowest operational frequency.
If you design the horn for high efficiency rather than bandwidth, the larger throat area will result in a short horn with a large mouth area on the order of an A7 for example.

For example:

The throat area for the 816 horn is 102.372 square inches.
The throat area for the A7 is 99.237 square inches.
The single throat area for the 210 horn is 114.115 square inches.

HF

[Horn Fanatic]

I've experience with both, IMHO 416 it's better if you use him till 500-800hz range, this driver have a wonderful midrange response, I would use 515 for better bass and "cupe" sound below 400hz

if you see Altec project they use if I remember well longer front loaded horn with 515.

where you would like to tune your horn? and cross with a 10/12" or a 2" driver?

What do you mean by, "tune your horn" ? This is not the first time I have read this term on the forum, and I have a good idea who originated it.

[Earl K]

Here's a decent thread (http://www.hostboard.com/forums/f700/137724-515-gpa.html) from the Altec Forum ( for some inspiration ).

Steve Mac ( a participant of that thread ) built some ( largish ) front loaded horns that utilized dual GPA 515-16G's (http://www.greatplainsaudio.com/downloads/515_G.pdf) within each horn.

Click the pic ( to go to the Hostboard thread chronicling his build thread / you'll find the thread in some digital disarray since the web-master there seems to be clueless about migrating older forum versions into the newer releases. Still the embedded info is of use to many ) .

http://www.superbadcat.com/midBassDesign/pics/horn01.jpg (http://www.hostboard.com/forums/showthread.php?t=95289)


Here's what his finished design looked like ( click the pic to walk through some of his web-site ) ;

That's a Fostex Tweeter sitting on top of the Altec 511E horn ( mated with a GPA 288H driver )

http://www.steevee.com/images/stereo/stereo_01.jpg (http://www.steevee.com/)

I have zero idea if he reactance-annulled the twin drivers in those back boxes.

No matter, he's still pleased as punch with this setup ( from 8-plus years ago ).

:)

[Horn Fanatic]

Here's a decent thread (http://www.hostboard.com/forums/f700/137724-515-gpa.html) from the Altec Forum ( for some inspiration ).

Steve Mac ( a participant of that thread ) built some ( largish ) front loaded horns that utilized dual GPA 515-16G's within each horn.

Click the pic ( to go to the Hostboard thread chronicling his build thread / you'll find the thread in some digital disarray since the web-master there seems to be clueless about migrating older forum versions into the newer releases. Still the embedded info is of use to many ) .

http://www.superbadcat.com/midBassDesign/pics/horn01.jpg (http://www.hostboard.com/forums/showthread.php?t=95289)


Here's what his finished design looked like ( click the pic to walk through some of his web-site ) ;

That's a Fostex Tweeter sitting on top of the Altec 511E horn ( mated with a GPA 288H driver )

http://www.steevee.com/images/stereo/stereo_01.jpg (http://www.steevee.com/)

I have zero idea if he reactance-annulled the twin drivers in those back boxes.

No matter, he's still pleased as punch with this setup ( from 8-plus years ago ).

:)


I have always admired that system. Hats off to the designer.

[berga12]

What do you mean by, "tune your horn" ? This is not the first time I have read this term on the forum, and I have a good idea who originated it.


I mean, which Fc he would like to chose for his horn, that's change the horn lenght (and throat-mouth dimension).

Maybe "tune horn" is not the right wording, sorry for my english :) :banghead:

[Horn Fanatic]

I mean, which Fc he would like to chose for his horn, that's change the horn lenght (and throat-mouth dimension).

Maybe "tune horn" is not the right wording, sorry for my english :) :banghead:

Understood. No problem.

I will suggest to the OP that the 515C is not the best choice for a domestic horn driver, as the fc is too low. The 515-8G with an fc of 37 Hz would be the better choice.
The horn cut-off frequency for that model would be approximately 33 to 35 Hz. The fc is based on the driver parameters, not an arbitrary decision. The same holds true for the throat area and chamber volume. The throat area and chamber volume are inter-related, and must be so to insure proper reactance annulling. To change one, changes the requirements for other.

I use a very convoluted equation to determine a horn fc. From that I calculate a throat area for bandwidth that provides 50% efficiency, then calculate the chamber volume.
With those figures calculated properly, the acoustical resistance of the throat and acoustical reactance of the chamber are at unity, resulting in a phase angle of 45 degrees.
If the throat area is increased for greater efficiency, the chamber volume will increase also, resulting in an increase in the degree of phase angle, typically toward the
reactive element, rather than resistive at cut-off.

Sadly enough, ALTEC never published complete Thiele-Small parameters on the 515-8G in order for me to provide enough design information to the OP. Too much vital information missing.

However, an easy way to determine the proper chamber volume can be found by this simple calculation;

V = St x c x (18.1 x (2 x Pi x c)) x L

V = Volume in cubic inches
St = Throat area in square inches
c = Velocity in inches @ 13,560.92
L = Length of horn where the throat area approximately doubles

Or: St = V/(2.9xL)

Keep in mind, a small horn throat area will provide increased bandwidth, a larger throat area will provide greater efficiency. Small throat, small chamber. Large throat, large chamber.

The standard exponential equation will suffice, but I prefer Vincent Salmon's Hyperbolic equation. With that, one is able to maintain the horn length,
but manipulate the mouth area within reasonable parameters. The 'T' number would be approximately .6 to .8. As the number approaches 1, the horn
flare begins to look more exponential, rather than hyperbolic. If the number exceeds less than .5, the horn would behave more like a resonant tube. Yuk!



HF

[thewings]

Terrific info, thanks everyone.

Horn Fanatic- which ever Altec 515 I go with needs to be available from GPA since I prefer to buy new. I am still thinking about a single driver config since it will cut down on vertical space which for me is more important to try and get as close to point source as possible. The depth of the horn isn't as big an issue.

[Horn Fanatic]

Terrific info, thanks everyone.

Horn Fanatic- which ever Altec 515 I go with needs to be available from GPA since I prefer to buy new. I am still thinking about a single driver config since it will cut down on vertical space which for me is more important to try and get as close to point source as possible. The depth of the horn isn't as big an issue.

I hope the information I have given you will be helpful. I have been using my method which is part of a greater horn design program I wrote over 20 years ago,
and it hasn't failed me yet. Just remember, your horn cut-off frequency should be slightly lower than fs by no more than 5 cycles.

Good luck, and please keep us posted on your progress.

HF