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Romy the Cat

Boston, MA
Posts 9,676
Joined on 05-28-2004

Post #: 1
Post ID: 25709
Reply to: 25709
Some analysis of the Joe’s system.
I was pointed out to Steve Guttenberg’s video “Meet Joe, and his amazing DIY horn speakers” at https://www.youtube.com/watch?v=EFoCVw2AJRc


I would like to provide some commentary regarding what I observed in there.  Steve Guttenberg is an industry self-celebrated idiot who for years patronized and glorified pre-manufactured labels and I was a surprise that he suddenly dived into DIY swamp. I do not feel that DIY solution are necessary better than industry solution but that fact that industry pimps begin to fish in murky DIY water I find is …. strange and boring.
Anyhow, here are some thoughts, critiques and complements to Joel’s system, in no particular order. Under no circumstances I admire or criticize what Joe’s is doing. This is just an attempt to do an analysis, to share the knowledge about the terrain…
The lower MF horn.  The sera-brooks horns. This is perfectly fine tratrix horn but a word of warning, something that many people do not consider. Be careful with wooden horns made in Philippines and the countries alike. The average humidity in there well over 85% and as the horns sent to countries with house average humidity under of 50 it might be a problem to the horn integrity.  
The MF driver. The Classic Audio electromagnet. I know nothing about this driver but there is something that I right the way do not like here. I have written many time that I never heard any decently sounding current-driven field-coil drivers. This is actually a theory that was invented as a pure theoretical proposition right at this site. The field-coil drivers always strike me a transients lethargic drivers. A few years back a poster at this site was debating with me his experience and he did not share my observations. Upon further investigation we recognized that I dealt with current-driven field-coil drivers but he dealt with voltage-driven field-coil drivers. Upon observing the difference in sound between RCA’s 1443 and 1428 (12V vs 120V), sound of RCA 900 line and my own experiments with my Vitavox S2 conversion to electromagnet I proposed a notion that  high voltage field-coil do not has that transients lethargic sound that are very common in low voltage  electromagnet. The explanation why is self-evident. I did not have a change to confirm it and did not rebuild my S2 to high voltage, still I am very confident that my theory is accurate. Now. Joe is running his MD driver at 15V that should make it challenged in transients. This is just an allegation, below I will provide some evidence.
The tweeter TAD ET-703. The meticulously time-aligned, with is perfect of cause. The selection of the twitter in my view is perfect evidence of my proposal above about transient problems of the Joe MF channels. The ET-703 is reported to have 107dB sensitivity but as far as I remember when I experimented with this driver it was actually 100dB and sonically it sounded like it was sub 90dB. That was the slower sounding tweeter as I ever heard and it is no surprise that Joe chosen to us this tweet to compliment the his low-voltage powered MF channel. The Quad ESL-57 have wonderful sounding but why do we need to have horn-loading topology to imitate the wonderful electrostats sound?  Another point. The tweeters us set at 10K and shot to 40K region, explain me why we need a horn at the tweeter?  Do we need to EQ the bottom knew or cap out the upper knee? I never understood it…  
The base horns. Reported 60Hz roll-off by twins of Altec 515B with Fs of sub 24Hz. Joe is correct that the driver act as a compression driver but he is not correct that his 60Hz comes from 120Hz mouth. In my estimation the 60Hz in this horn is coming as a direct radiator. It is very easy to figure out by measuring the horn equalization. I absolutely insist that there is very little horn EQ in there at 60Hz.I also personally feel that any horn that do not used HIGH-pass filter under the horn rate is not a truly horn as it letting the LF sound to chock the mouth that very dramatically worsen the above the horn rate sound quality.  
The LF section, the twin’s double-pull sub with SS amps running DSP. It is what it is, we all cheat in one way of other with our LF. Frankly speaking, considering the Joe’s dedication to his project I was unanticipated more elegant cheating and I certainly would like to see the LF section to be posited outside of the main speakers. 
Joe’s claims that all filtration is 6dB, how about the tweeters? I do not think so… 
Another interesting factor. With all efforts and pride invested into organizing of the playback why he let one amp, and not particularly fancy amp to run the whole system? Why not multi-amping?
Another interesting observation and Mr Guttenberg’s is too stupid to ask it. What Joe’s does it what I call Japanize configuration.  The Japanize configuration implies that MF handled by split drives: Upper MF and lower MF and the spit happens at very high crossover point ~5K. It is not good or bad but I always wander why people chose to do it. Is it because the limitations of the chosen drivers or is it because any other reasons? I really would like to hear some metaphorical reasons that would be decoupled from specific drives limitations…  

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
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