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Jean Hiraga Altec A5 Crossover modification
Jean Hiraga Altec A5 Crossover modification
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Old 20th January 2021, 11:32 PM   #141
puppet is offline puppet  United States
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Jean Hiraga Altec A5 Crossover modification
The 124a owners manual makes no mention of that at all.

APHEX 124A OWNER'S MANUAL Pdf Download | ManualsLib
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Old 20th January 2021, 11:58 PM   #142
tizman is offline tizman  Canada
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I compared the 124A and 124B manuals, and they are identical. No mention is made of being able to use both input/output sets at the same time in either one. I would have tried this already if I had enough cables to do it, but I don't at the moment. If you look at the block diagram of the 124A/B circuit included in the manual, it appears that the two in/out circuits are not connected. The volume pot is only used when the signal goes from RCA to XLR. When the signal goes from XLR to RCA, there is no potentiometer in that circuit, but there is a +4/+8 DB adjustment internally, and a 600 Ohm out switch on the front panel.

Last edited by tizman; 21st January 2021 at 12:01 AM.
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Old 21st January 2021, 12:05 AM   #143
tizman is offline tizman  Canada
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Quote:
Originally Posted by puppet View Post
The 124a owners manual makes no mention of that at all.
I sent another question to the support person from Aphex in order to clarify that the 124A and 124B are identical with respect to their function, as I have a 124A as well, and to ask how the volume pot works.
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Old 21st January 2021, 01:59 AM   #144
Pano is offline Pano  United States
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Jean Hiraga Altec A5 Crossover modification
There isn't analog gain at the head end of the XTA DP200 is there? I have never used that unit, so don't know. If there is not, you'll need it and the 124B can provide it.
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Old 22nd January 2021, 12:09 AM   #145
tizman is offline tizman  Canada
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Quote:
Originally Posted by puppet View Post
The 124a owners manual makes no mention of that at all.

APHEX 124A OWNER'S MANUAL Pdf Download | ManualsLib
This is the reply to my second round of questions about the 124A. While it might be implied that the 124A works with both circuits running separately but at the same time, I don't see that clearly stated in the manual. At any rate, the reply does confirm the volume pots only work for one of the two circuits, and that they both work at the same time with separate signals. I will confirm that when my XLR cables arrive.
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Old 22nd January 2021, 01:03 AM   #146
tizman is offline tizman  Canada
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Originally Posted by Pano View Post
There isn't analog gain at the head end of the XTA DP200 is there? I have never used that unit, so don't know. If there is not, you'll need it and the 124B can provide it.
Having had the opportunity to play around with the unit a bit, the XTA is able to do most of what the 124A does except for converting cables. The 124A converts RCA to XLR, and XLR to RCA at the same time, for two different signals, while also matching levels between pro and home components. I have a few pairs of XLR cables on order, as I want to see if using the 124A for this function, along with the XTA DP200 for crossover and EQ duties, will allow me to further reduce noise through the speakers.

One problem I am having is that the XTA DP200 is louder in the right channel than the left by 5 DB. I measured with a fixed microphone and REW, by switching the inputs from the DP200 to the amp from right to left channel. I sort of solved this problem by reducing the gain of the right channel by 5 DB, but I am concerned that this imbalance issue may be due to some other problem with the unit.

I have not entirely dialed in the setup using just the DP200 and without the 124A, but I do have some early observations....

-So far, no matter what gain settings I use, the active setup is not as completely noise free as the passive setup. I can get it quiet enough with the active setup though.

-I tried using several PEQs to even out the response I was getting with REW. I tried this with the microphone set up 5 feet in front of the speaker, and then tried it with the microphone set up at the listening position. The response curve I ended up with in both cases was much flatter, but both sounded absolutely terrible. Apparently, I don't like the sound of multiple PEQs. I only used PEQs to flatten peaks, with the exception of a mild HF shelf to bring up the high end, and an attempt to flatten the 400 HZ dip. I eliminated the 400 HZ PEQ first, as that was obviously a bad idea, but kept the rest and still disliked it. Right now, I am using the DP200 as a crossover, a way to create a quieter gain structure, and to add a HF shelf to lightly equalize the HF.

-The ability to quickly change between Bessel, Butterworth and LR, jump between 12, 18 anb 24 DB/octave slopes, and change the frequency of the crossover really helps you figure out what crossover works best with your setup. I was pleased to discover that my 630 HZ choice for the passive crossover I built was one of the better ones when using a 12 DB/octave slope.

-The current DP200 setup, with a LR 24 DB/octave crossover at 630 HZ, and a 5 DB shelf starting at just over 4000 HZ sounds very good. From memory (whatever that's worth) it sounds cleaner than the passive crossover, but not as "real". I haven't made any attempt to A/B them as that is complicated to do quickly, but I'll try doing a REW measurement to compare them.

-I would also like to try the active setup with no HF shelf, and using the passive crossover's HF shaping portion to hear how that sounds.
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Old 22nd January 2021, 02:05 AM   #147
Pano is offline Pano  United States
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Jean Hiraga Altec A5 Crossover modification
Thanks for the updates. Too bad you can't get the active quieter, might still be a gain problem.

As for EQ, I often found that I end up using about half of what the computer tells me I need. That's been true for many speakers and headphones. I also like lower Q filters than REW does by automation. Just something you might try.
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Old 22nd January 2021, 02:19 AM   #148
tizman is offline tizman  Canada
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Pano: I didn't use REW to automatically generate the filters. I just fiddled. I will try it though.

I really don't understand the huge dip at 400 HZ in all my REW measurements. Other than that, there isn't anything anomalous in the measurements. Also, trying to fix the 400 HZ dip makes things sound much worse. I should probably open them up and make sure my Kappa 15Cs are properly installed. I may also try reducing the doghouse volume by a third as recommended by a few folks on the Klipsch forums. This is supposed to even out the response.

Before trying to get REW to generate the PEQs, I will try to lower the Qs of all the ones I used to see if it sounds better. Thanks for your suggestion!
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