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09-28-2016 Post does not mapped to Knowledge Tree
Posts 4
Joined on 09-28-2016

Post #: 1
Post ID: 22795
Reply to: 22795
Rare Onkyo HM-300 MK2 Horn...need info

I just logged myself in so first of all: Hi Everybody Wink

Few days ago I aquired a pair of very interesting 3way horn speakers which seem, as I imagine, to ba an ambitious DIY project from the past. These are basically the Altec Vott A7 replicas (made of 25mm plywood) loaded with 15" TAD TL-1601 8 ohm speakers, a completely new for me Onkyo HM-300MK2 horn tweeter/squawker/midrange/whatever, and last but not least the legendary german Corona plasma tweeters.
This system also contains a pair of active Sony SRP-F300 crossovers.
I know TAD but this Onkyo Horn is extremely rare and I only found some japanese websites which I completely didn´t undestand. I connected these drivers without any crossover and immediately was very suprised about the sound quality. They sound very very smooth. I had some experience with Altec horn which IIRC sounded more harsh and sharp. Not these Onkyos...they sound more like EV 1823 in Sentry 3. They also seem not to be extremely efficient like the others.
Anyone have some experience with HM300? maybe some fellow members from Japan could tell me something more about it? I´m not sure if I understood the translation correctly but it was told that the crossover point suppose to be at 300hz which I don´t really believe. I like them very much and I think these are keepers but I´d like to know more about them anyway...
I will try to connect the entire system within next few days as soon as I organise all amps (6 x mono) and xlr cables for both active crossovers.



edit: I just bumped into another japanese website and look what I´ve found: http://ameblo.jp/sp3/image-10019757868-10011792151.html
So 300Hz? really?
09-29-2016 Post does not mapped to Knowledge Tree
Romy the Cat

Boston, MA
Posts 9,989
Joined on 05-27-2004

Post #: 2
Post ID: 22796
Reply to: 22795
Onkyo HM-300MK2
Hello, Pawel. 
I never heard nether about Onkyo HM-300MK2 or about anybody who use it. It looks like it is one of many obscured Japanize drivers, and they made plenty of those. A simple googling said that it has 2 inches voice coil, duralumin diaphragm, 8Ω / 30W 111dB,cut off 300Hz, reproduction frequency band 500 ~ 12kHz, Alnico magnet about 13.7kg. Not a lot of information but it is what you get. The driver look like was used in Altec 811 like horn, not 511. The combination of narrow horn, smallish voice call suggest that a reasonable crossover would be around 750Hz but if course it need to be heard to make any further judgments.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-30-2016 Post does not mapped to Knowledge Tree
Posts 4
Joined on 09-28-2016

Post #: 3
Post ID: 22798
Reply to: 22796
Hi Romy,

thanks for your message. I wasn´t aware that Japan made so many different horn speakers back in the days. Looks like they knew what they did...I like these horns a lot Smile They are by far not that involving and musical like my Tannoy Monitor Gold but that might be a matter of a proper crossover and tuning. At the moment they sound rather transparent and analytical but not harsh.
I´m afraid these horns are way too large for my listening room Sad I´ll probably stick to my Tannoys...
02-25-2018 Post does not mapped to Knowledge Tree
Posts 4
Joined on 09-28-2016

Post #: 4
Post ID: 24709
Reply to: 22795
Onkyo Scepter 500 and others
So, two almost two years later and this contraption is still in my room and "ain´t goin nowhere" :-)

Guys, I became obsessed with horn speakers and specially with Onkyo product so I would like to share with you my latest experiences.

The speakers I talked about still stand in my listening room and turned out to be probably the best speakers I ever had. I don´t use the TAD tl1601 anymore, I bought mint Altec 416-8a with all original cones and coils. I damped the 828 enclosures and reduced the area of the reflex port to 75 square inches, than to 50 inches. Thast gave me THE BEST bass and midbass I have experienced in my system EVER. I mean the Altec 828 and 416-8a play easily to 30hz now and even a bit lower. Probably some of you will say that these enclosures weren´t build for that kind of bass reproduction but I sware they just kick ass. I don´t use my subwoofers anymore except for home theater. I was absolutely mesmerised the first time I have pluged the 416 into my system. The vocal reproduction in uncanny, none, absolutely none speaker I listened to was capable to reproduce the voices in such intimate manner as the VOTT. I was completely shocked. I sold my Tannoy Monitor Gold 15 and decided to buy Altec midrange horns, crossovers and drivers. Since 416 was so good, the rest must be equally good or even better right? I got the 808a with symbiotic diaphragmas and 511 horns. What a dissapointement. This horns comapred to Onkyo Hm300a literally look and sound like crap. The 511 horns are build from thin metal shit and ring like a bell. Onkyo is completely from cast iron. It weigt 15Kg and is much more neutral than altec which sounded edgy and sharp. I know the 808a isn´t the best Altec driver but it wasn´t even the same league as the Onkyo.
Let me tell you something about the hm300a. These horns/drivers are made in Japan in 1972 or so. This was the japanese answer for JBL, ALtec and other western brands that were very popular in Japan in 1970s. Onkyo called their flagship top of the line speakers "The Scepter". The produced a ton of different drivers and horns, all of them with spectacular quality. How do I know that you will ask. Well, I have a ton of them. I bought Onkyo drivers like crazy for last two years Smile the first series with alnico magnest like HM300a, HM450a, HM500 and tweeters like tw1500, tw7a, tw8s. Some of them I sold, other I kept.
One day I bought something very spectacular, a pair of later built d5020a drivers, not alnico and much newer than the old hm300a.
The d5020a are from 1978 and were a smaller brother of the d6540a drivers which were the midrange drivers of the most expensive speakers Onkyo ever built.
Ladies and gentlemen, meet hte Onkyo Scepter 500:


Would you believe Onkyo ever built such high end speakers? And now they mostly build some medicore surround receivers Sad
Anyway, these monster horns were about 600000 yen each, it was a fortune in 1978. And I became obsessed with them.
It is a 4 way system with 15" bass driver in bass reflex enclosure, 1.5" midrange driver, one tweeter and one super tweeter. By accident I bought the d3520a tweeters first and tw3001 super tweeters shortly after that. But the other parts were missing. I thought it would be impossible to find the rest but thankfully I was wrong Smile About two weeks ago a friend of my from Germany offered me a complete Scepter 500 speakers without enclosures. I mean EVERYTHING. I only miss the NT4a crossovers but I got very similar NT84a 4 way crossovers. He also sold me a lot of different Scepter parts like different drivers, horns and acoustical lenses.
I will post some pictures within next few days as soon as I´m going to get rid of that flu that keeps me in bed since 3 days.

I want to build a pair of Scepter 500 clones, a little bit modified and I hope you can help me a little bit with this project.

See you soon
02-25-2018 Post does not mapped to Knowledge Tree
Posts 4
Joined on 09-28-2016

Post #: 5
Post ID: 24711
Reply to: 24709
Just to share with you with my ideas about the Scepter 500 clones. I´m not sure if I will use the w3801 bass drivers. I felt in love with Altec 416 and quite frankly I very much doubt that Onkyo would sound better or equally good. It surely doesn´t sound as fast and responsive as the 416 but it might me the enclosure issue.
I don´t like the drivers positioning of the original Scepter 500. Proper time allignement is probably impossible. From my experience, the positioning of the bass drivers in such  manner is in the VOTT gives the best effects. I was able to align my bass and midrange coils to probably exact milimeter and it makes a huge difference, is almost sound like a coaxial driver, pretty much the same coherency as my Tannoy Monitor Golds.
I´m thinking about building speakers similar to Vox Olympian, I mean the physical part. All drivers above each other for proper time alignment. I think it will work just fine..

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