Welcome to the board ! Hope you get the answers you need and curious as to why no one has chimed in here yet ?
As a new A7-500 owner, this is my first post on the Altec board. I just got a pair of A7s with 803a (one Heathkit and one Altec, otherwise identical late '50s) LF and Emilar EA175 drivers on 511b Horns for HF. All of the drivers are 16ohm. The LF drivers have been re-coned at some point with Waldon cones
There were some home-made crossovers which I haven't determined what values are represented. In the meantime, I've spoken with Bill at GPA who suggested crossing over at 800 not 500, despite having 511b horns.
Right now, I'm bi-amping them and using an Ashly XR1001 running to McIntosh MC60s on the HF and a MC250 on the LF.
My overall impression is that that the mid are great and they're way more forward and efficient than my Bozak Symphonies, but the Bozaks are more detailed and wider. The A7s are, as expected, rolling off the bass pretty soon and a sub seems to help. I could also use some sparkle on top and I'm contemplating adding some super tweeters.
I will be refurbishing the cabinets and doing what I can to extend the bass (smaller opening, better damping etc.).
OK here's my question: can anyone point me to the best crossover schematic that matches the drivers I have? Would everyone agree that crossing at 800 is better than 500? I'll want to have an L-pad in circuit to tame the HF. And I'd like the option of adding a super tweeter. Would I let the LF roll off naturally or should I somehow account for a sub crossing at 100 hz or so?
Here are photos of everything for reference:
A7_Cab1_rotate.jpg
A7_HomemadeXover_scale.jpg
HF_EmilarEA175_scale.jpg
Attachment 3571
All being equal the 511 is louder than the 811. 800 hz is safer than 500 hz. Play around and see what you prefer depending on amps, music and loudness.
Greets!
Just now seeing this..........
FYI: Emilar Ea 175-16 driver for 511-b horn
I use/prefer 500 Hz with the 802, though requires various tweaks to smooth them out, so not for everyone and over time I've noticed that many folks have switched to 650-700 Hz as a good compromise. According to the above though, looks like Bill's 800 Hz suggested be the minimum to consider and all things considered assuming this is a HIFI/HT app, believe that the M19's 1200 Hz XO will net the smoothest overall response once shelved/EQ'd flat in room from < 40 Hz out to 15-20 kHz. Final system efficiency will typically be around 93-94 dB/W/m.
GM
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
I prefer the 800 hz crossover point on my 828 system.
I am also running EA175's right now, except mine are mounted on EH800 horns. I really like the Emilar drivers. I switch between those and 802D's.
If you can build a xover that has some MF EQ shelving, the system will sound better.
You are on the right track with the port size. I reduced mine down to 7.5"x10".
Welcome to the hostboard!
Originally Posted by FriendlyVolcano
Welcome to the Forum !
There are " L/C" crossover calculators on line. You want a second order, 12 dB per octave, and a Butterworth. KISS. NO Zoebels.
2-Way Crossover Calculator / Designer
I own A7s, and my best friend, with decades of solid ALTEC experience, suggested 800 HZ also to me. He also prefers the 811 over the 511 horn, and an 802, for home use. He used A7-800s in quad sets, in ALL the medium-sized movie theaters he has owned...many !!
The following is ONLY "my " opinion, and I seldom am in consensus, so here we go :
Your Emilar EA175 will possibly be a nice driver, I am currently re-doing an ALTEC VALENCIA system for an old friend, and I ditched the 806 with a small body in April for a rebuilt pair of EA175s, the "A" for alnico, and a " C" means its a ceramic.
You need to SIMPLIFY your system, if you want to have something other than just another ordinary-sounding A7 system.
FIRST: Get RID of the active crossover. Its a whole other active audio stage, not really needed, which you are inserting in the chain.
SECOND : When you use two different amps to biamp, THAT is also a compromise, as each amp has a different time constant through it. BIAMP AMPS SHOULD BE IDENTICAL, top and bottom.
THIRD: Go to a custom DIY passive crossover, at 800 HZ, 12 dB Butterworth. Avoid a M19 type crossover, FOR TWO REASONS : (1) the loss of efficiency, ( which forces you to use poor sounding amps, and likewise - excludes the best-sounding ( for an ALTEC ) tube-type amplifiers ) and (2) the degrade of SOUND QUALITY by going through added circuits, zoebels, etc. "as though there is NO PRICE to pay" with this added complexity.
Seek to execute the A7 simpler..... and smarter.
FOURTH: Avoid a super tweeter. KISS rules. I can show you how to get "sparkle" on the top end, by use of modern industrially-priced capacitors. These are the newest state-of-the-art WIMA-brand film caps, for use in bypassing a passive crossover's existing film caps, to get THE HIGHS CORRECT. I have some superb new-type capacitor suggestions to make to you.
Use of speaker wire with SOME silver content, will also be necessary, to maintain wide bandwidth into the listening room.
FIFTH: The mono MAC 60 amps should be used, by themselves, to play your entire system !!! GREAT news !! The MC 60 IS probably their best sounding tube amp, of all they ever produced, in some knowledgeable people's experiences and opinion. So glad you have them.
SIXTH: I know of an experienced audio person who CONSERVATIVELY simplifies the Mac 60 circuit, stabilizes the power supply, and audio circuit ( beneficially eliminates an un-needed stage ), so you can consider doing that, perhaps, in the future.
SEVENTH: Wiring: The A7, in home use, can play well, on as little as 3 Watts, easily , but ONLY IF the speakers are properly (a) wired for maximum transfer efficiency, and (b) employ a wide bandwidth playback..... THROUGH well-thought-out wire-type selection AND implementation, .
Wiring optimization, in my opinion, to maintain transfer efficiency and wide bandwidth, must be done FIRST, as a matter of routine set up, be it a 3 Watt or a 60 Watt amp, to obtain highest sound quality in a ALTEC speaker.
EIGHTH : Reconed ALTEC woofers : When not an original cone - will be something you MAY want to re-do, to an OEM, GPA re-cone and a re-magnetization. My 3-2017 used Valencia purchase came with 416s, which were reconed horribly... NOT STOCK. 'Had them re-done by Bill, in April 2017. Lovely now...no worries at all.
Finally, I would NOT be in a rush to make non-reversible changes to the A7 box, bracing and change the porting, until you further optimized the basic system and whats running the speaker.. This post outlines it for you.
Ohh, I forgot, adding mass on top of the A7 enclosure greatly helps a stock box. Go to the Garden Department of any chain hardware store, or even Walmart, and buy a dozen or so " concrete stepping stones " which sell for about $1.50 each, weigh 16 pounds each, in a 12 by 12 by 1.7 inch size. I use them a lot, when I want to KEEP a box stock..... till all else is squared away.
Go slow on this project. Think !!!
Feel free to contact me, and we can chat about our A7s.
Good luck !!
Low Ohms......Jeff Medwin
One other comment, that passive crossover you pictured, thanks, is not good enough as I see it. But you MAY be able to use the Inductors, and DIY up a simple but HIGH QUALITY DIY crossover. I did. I can give you great ideas on crossover caps at 80% off, affordable AND as good as it gets !!
Last edited by LowOhms; June 27th, 2017 at 01:23 AM.
[QUOTE=FriendlyVolcano;1972731]As a new A7-500 owner, this is my first post on the Altec board. I just got a pair of A7s with 803a (one Heathkit and one Altec, otherwise identical late '50s) LF and Emilar EA175 drivers on 511b Horns for HF. All of the drivers are 16ohm. The LF drivers have been re-coned at some point with Waldon cones
There were some home-made crossovers which I haven't determined what values are represented. In the meantime, I've spoken with Bill at GPA who suggested crossing over at 800 not 500, despite having 511b horns.
Also have the A7-500s, agree with Bill, crossing over at 800hz just sound better than 500hz, although have the stock components so could not suggest a XO that would work with your setup. Pic of my XO as of this weekend.
SD-50.
This is very embarassing, but I am not sure if we have ever spoken.
Looking at the crossover's photo, with your 5 uF caps, I would THINK...... we have!!
Can you contact me, there are some things I want to find out, about your use, experience, and opinion of your 5 uF caps, plus, there is a WIMA cap series I'd like you to seriously consider, NOT overly expensive at all.
My email address is [email protected].
Thank you,
Jeff
Thanks Jeff and all for your detailed responses.
Since I was a new poster on Hostboard, this took a few days to appear, so I was surprised to see all the thread action.
These speakers will only likely live in my studio at work. They'll never cross the threshold at home (unless my wife decides to run off with the mailman!) My studio is fairly large at 22x60x18' high. Brick walls, wood floors, glass window wall, wood ceilings, city noises. So a lot to deal with (it was part of an old disco). The good part is that we're surrounded by a parking garage, so no neighbors to complain when things are cranked up!
I was wondering if it's worth trying to get an old Altec crossover with brightness knob (like a N801-8A) and gut it and rebuild the caps. I like the look of the Altec crossover plates/knobs. Is there a particular model that is suited to doing this?
Or just build one from the ground up. Would you recommend having an L-pad in the HF section as Altec did or just go with a single resistor (or none)?
Your idea of weighting the top is interesting. I'm wondering if I use sandbags, and then place the horns on top of the bags would kill two birds with one stone?
I'll be in touch with a PM...
fv, after reading your post again, run what ya' brung ! Since you already have what you described, blast it "till you blow it ! Especially in the room you have. Then we can talk about upgrading you system. You'll need proper Altec hf drivers and the appropriate lf woofers. You're power is way more than adequate.
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