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Jean Hiraga Altec A5 Crossover modification
Jean Hiraga Altec A5 Crossover modification
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Old 19th July 2020, 12:20 AM   #1
tizman is offline tizman  Canada
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Default Jean Hiraga Altec A5 Crossover modification

Hello All.

I recently built this Jean Hiraga crossover for the Altec A5 in order to combine a 511B with a Renkus-Heinz SSD-1800-8 compression driver and a Peavey FH1 with an Eminence Kappa 15C. When I started my build the specs that I looked at for the original LF cabinet that came with the Altec VOTT A5 indicated that it would have a sensitivity close to what the FH-1 with a 15C would have. Apparently, I was mistaken, as the specs for Altecs 828 cabinet show it to be substantially less sensitive than the FH-1 with a 15C. Basically the FH-1 combo is 6-7 DB more sensitive than an 828 cab. I realized almost immediately that there was an issue, as there was obviously too much bass in the output.

I need to attenuate the bass by around 6-7 DB. I added an L-Pad on the output of the Hiraga, as per Pete Riggle's modification of the Hiraga crossover, in order to control the treble, but there is not enough treble even with the L-Pad set to let all the power through to the HF section. Looking at the schematic, there doesn't appear to be any mods that I can make to it that will increase the overall treble level while still maintaining the equalization that the horn/cd combo requires. Am I correct in thinking that my only solution is to add an additional L-Pad to the LF section? Should I move the existing L-Pad to the woofer section, as it is useless on the HF section? Or am I missing something? Any advice would be greatly appreciated.

This is the link for the Hiraga crossover as modified by Pete Riggle....
Altec A7 Voice Of Theatre Speakers - Vertical Tracking Angle on the Fly (VTAF)
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Old 19th July 2020, 02:42 AM   #2
ticknpop is offline ticknpop  Canada
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Jean Hiraga Altec A5 Crossover modification
Adding a level control or pad to the woofer circuit will destroy the amplifier damping, retune the bottom end alignment and just about every bad thing you can think of. Either biamp, or get a new woofer. I’m surprised any woofer would be more efficient than a HF horn and compression driver.

You copied the Riggle version Hiagra A - 5 crossover and changed all the drivers ? It isn’t a recipe for a good outcome....... your too far away from the original components to expect this to work well. Having the cabinet and the horn with different drivers Isn’t the same thing.

I copied the JBL 4350 studio monitor crossover, but I had 3 of the 4 original drivers. That worked out give or take some low end response. if your into horns you can hear the 4350 clones at a Toronto diy event (won’t be one until there is a covid vaccine).

Last edited by ticknpop; 19th July 2020 at 02:49 AM.
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Old 19th July 2020, 02:56 AM   #3
Pano is online now Pano  United States
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Jean Hiraga Altec A5 Crossover modification
Unfortunately it looks like you've gone down the wrong path. This published crossover is not at all suited to your speaker. You'll do best to start from scratch. Sorry for the bad news.

Since I was there for the original Hiraga A5 speaker and crossover (I used them for gigs) I know how they can sound. When I built my own A5 and tried to use the published crossover it was not at all satisfactory. I had to start from scratch. The A7-500 crossover was different from that, and the A7-800 a little different still.
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Old 19th July 2020, 03:09 AM   #4
AllenB is offline AllenB  Australia
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Jean Hiraga Altec A5 Crossover modification
As much as loud bass is often seen as an impossible challenge, some like challenges.

Do you have a schematic?
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Old 19th July 2020, 03:13 AM   #5
Pano is online now Pano  United States
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Jean Hiraga Altec A5 Crossover modification
About the too much bass, are you really getting 104dB @ 2.83V thru the bandwidth of the FH1? That's a heck of a lot for a woofer. The 511 horn will need attenuation at its bottom end to flatten the response. That's going to eat up a few DB, as you have found.
The best thing to do is measure what have, and start from there.
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Old 19th July 2020, 05:43 AM   #6
tizman is offline tizman  Canada
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Quote:
Originally Posted by AllenB View Post
As much as loud bass is often seen as an impossible challenge, some like challenges.

Do you have a schematic?
The schematic can he found in the link in my first post. It is down the page some...
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Old 19th July 2020, 05:58 AM   #7
tizman is offline tizman  Canada
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Quote:
Originally Posted by Pano View Post
About the too much bass, are you really getting 104dB @ 2.83V thru the bandwidth of the FH1? That's a heck of a lot for a woofer. The 511 horn will need attenuation at its bottom end to flatten the response. That's going to eat up a few DB, as you have found.
The best thing to do is measure what have, and start from there.
I just started doing measurements with REW. The preliminary results are that the FH1 with Eminence Kappa 15C is roughly 6-7 DB louder than the 511B with Renkus-Heinz SSD-1800. Iím relatively new at doing measurements but my ears tell me that what Iím seeing in REW is correct. Am I correct in saying that other than the L-Pad on the output, and the shaping LCR, there is nothing else attenuating the HF section in the Hiraga schematic? Iím new to crossovers, so I may be missing something. The published sensitivity of the Altec A5 is 97 DB/W/M for the entire speaker. I couldnít find the spec for the Altec 828 LF cabinet on its own. The FH-1 with its stock driver has a published spec of 104 DB/W/M. The FH-1 spec is in keeping with the LF portion of the La Scala that it greatly resembles.
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Old 19th July 2020, 06:14 AM   #8
AllenB is offline AllenB  Australia
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Jean Hiraga Altec A5 Crossover modification
You could use a 2:1 autotransformer instead of an L-pad on the woofer.
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Old 19th July 2020, 06:19 AM   #9
tizman is offline tizman  Canada
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Quote:
Originally Posted by ticknpop View Post
Adding a level control or pad to the woofer circuit will destroy the amplifier damping, retune the bottom end alignment and just about every bad thing you can think of. Either biamp, or get a new woofer. Iím surprised any woofer would be more efficient than a HF horn and compression driver.

You copied the Riggle version Hiagra A - 5 crossover and changed all the drivers ? It isnít a recipe for a good outcome....... your too far away from the original components to expect this to work well. Having the cabinet and the horn with different drivers Isnít the same thing.

I copied the JBL 4350 studio monitor crossover, but I had 3 of the 4 original drivers. That worked out give or take some low end response. if your into horns you can hear the 4350 clones at a Toronto diy event (wonít be one until there is a covid vaccine).
I had all the parts on hand, and have done some research on the combination. The Renkus-Heinz drivers are the only wild card with respect to my research. There is not a lot of information on them, but Renkus worked on the later Altec drivers before starting his own company, and the specs of the SSD-1800 are similar to the later Altecs. What I could find out implied a similarity with Altec drivers. A 511B with an Altec 8XX or 9XX combined with a La Scala bass bin or a FH-1 has been done by many people. I found a crossover designed by ALK specifically for this combo as well. I didnít expect there would be any issue with the bass bin being louder than the Horn and CD, and thought that the L-Pad that is at the output of the Riggle version would allow me to bring down the level of the HF if needed. As it is, the opposite is required. Is the LF section of an A5 really that much less sensitive than an FH-1 or La Scala?
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Old 19th July 2020, 06:42 AM   #10
tizman is offline tizman  Canada
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Quote:
Originally Posted by AllenB View Post
You could use a 2:1 autotransformer instead of an L-pad on the woofer.
I originally was going to build the ALK crossover for this combo, but didnít have autotransformers on hand other than the ones in speakers that are currently in use. Buying them from the US with exchange and shipping makes them very expensive. Also, the ALK schematic doesnít have a shaping section to equalize the HF response. If the LF section was about 6 DB quieter, Iím sure they would sound good. I may pull them out of the speakers they are in if there isnít an alternate solution. I have an electronic crossover and multiple amps, as building tube amps is my primary hobby, but tried the passive crossover to simplify things for other non-audiophile listeners in the house.
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