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Multi-Way Conventional loudspeakers with crossovers

GPA 604 adventures
GPA 604 adventures
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Old 29th December 2017, 08:32 PM   #11
wesayso is offline wesayso  Netherlands
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Did you look at the Hiraga 604?
Click the image to open in full size.
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Old 30th December 2017, 08:37 AM   #12
c_door is offline c_door  Italy
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The Onken concept for sure gives strenght to the structure.
Hiraga's are very styilish, so bad he's not giving away the plans
A Hiraga-like cabinet with wider baffle and more internal volume should be both handsome and good sounding.
The slot port on the base can be made highly tunable by building it as a round of small ports.
Closing/stuffing some of the ports would allow to "tune" the bass emission with the room.
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Old 30th December 2017, 09:02 PM   #13
c_door is offline c_door  Italy
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I found this page on Jeff Markwart's Corner
Phase Correction for Altec Ferrite Duplexes - Great Plains Audio
As explained there, I've decided to get rid of the MF-LF attenuators and ordered the parts for the plain filter here:
Great Plains Audio 604-8H-III - Great Plains Audio

Let's see how much better it sounds when compared to the stock crossover..

About the above Hiraga's product, I can see the reason why he's using laminated hardwood instead of birch ply.
Compared to the Bison made of two layers of ply, this cabinet looks more straightforward to build and finish.

Last edited by c_door; 30th December 2017 at 09:09 PM.
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Old 30th December 2017, 09:42 PM   #14
Pano is offline Pano  United States
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GPA 604 adventures
As mentioned earlier, the Markwart crossovers are not suitable for open baffle, they are meant for a large box.
The 604 and 605 will work nicely on open baffle down to about 100Hz, with the proper crossover. A helper woofer can fill in the low end.
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Old 30th December 2017, 09:58 PM   #15
c_door is offline c_door  Italy
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Thanks Pano.
My open baffle is only a quick temporary arrangement.
A final enclosure will be possibly a Hiraga style, I like how it looks.
About OB plus helper woofer, how do you rate it ? Is it worth the cost, size an complexity ?
I'm not after strong bass for electronic music, more interested in smooth reproduction of the bass frequencies as you can hear from a live orchestra, or jazz combo.
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Old 30th December 2017, 10:24 PM   #16
freddi is offline freddi  United States
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you knew I'd say:

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Old 30th December 2017, 10:29 PM   #17
Pano is offline Pano  United States
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Ha ha, of course!
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Old 30th December 2017, 11:59 PM   #18
LineSource is offline LineSource  United States
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Quote:
Originally Posted by c_door View Post
Hiraga's are very styilish, so bad he's not giving away the plans
Jean Hiraga's personal explanation of his Altec 604-alnico cabinet construction draws-out like putting large Onken style ports on the bottom of the cabinet.

====SUMMARY: MLTL for GPA 604 using 48" x 96" plywood 11.5cuft empty, ~10cuft net
Internal length = 46"
Internal width = 24"
Internal depth = 17"
Center GPA 604 at 14.9" below the internal top
Center 1.5" long, 4" diameter port 4.2" above internal bottom
=============

====SUMMARY: MLTL for GPA 604 using 60"x60" Baltic Birch Plywood 14.5cuft empty, ~12.5cuft net
Internal length = 58"
Internal width = 24"
Internal depth = 17"
Center GPA 604 at 18.7" below the internal top
Center 3" long, 4" diameter port 5.3" above internal bottom
===========
====Basic TL math.
1) Using the TL calculator, the T/S parameters for the GPA 604-8H-III recommend a transmission line cross section area of 405sqin.
2) The W*D aspect ratio is selected to both reduce line resonances and balance (wide= low baffle-step frequency) and (deep = attenuate rear cone reflections)
...2a) Using an irregular X*Y ratio like 1: 1.414 produces internal dimensions of W=23.9" D=16.9". ==> reasonable balance.
...2b) Using golden ratio of 1: 1.618 produces internal dimensions of W=26.6" D=15.8". ==> too shallow.
3) Baltic Birch plywood comes in 60" x 60" sheets, which favors a 58" maximum internal line length. ==> 3-sheets for 2-cabinets
4) MLTL math: If the driver is offset at 0.324x (slightly less than 1/3 the length of the straight transmission line), the 3/4 wavelength standing wave can be totally suppressed, and in addition the impact from every other quarter wavelength mode (3/4, 7/4, 11/4, …) will also be essentially removed from the system SPL response.
...58" - 0.323*58" = 18.7" down from the line top(internal)
...58" - 18.7" puts the GPA 604 center at 39.3" above line bottom(internal)
5) Check: Locating the GPA 604 horn at ear level = 36" - 39" is recommended for best seated and standing soundstage.
6) Port: 3" long 4" internal diameter port centered at the 11th harmonic =5.3" above the line bottom.
7) Bracing: one top-to-bottom center brace and one side-to-side center brace.
8) Stuffing: 0.5 lb/cuft in top 60% of line
8b) option for extra high frequency absorption: staple 1" thick Owens 705 fiberglass panels onto top panel plus back and sides of upper 40% of cabinet panels.
Attached Images
File Type: jpg hiraga bottom Onken.jpg (181.5 KB, 232 views)
File Type: jpg hiraga quote.jpg (225.8 KB, 237 views)

Last edited by LineSource; 31st December 2017 at 12:04 AM.
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Old 31st December 2017, 03:22 AM   #19
GM is offline GM  United States
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Quote:
Originally Posted by freddi View Post
you knew I'd say:
Ever auditioned any?

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Old 31st December 2017, 06:29 AM   #20
freddi is offline freddi  United States
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I ran my alnico motor 604B with "E" cone in K15 - best I ever heard Gary Karr's "Spirit of Koussevitzky" album or Hans Hotter (early performance of Schubert's "Winterreise") K15 must be braced better than stock - easy with the "shelf" and 3/4" dowel struts for the wings, and on-edge braces plus a strut to the shelf for the rear panel.
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