Bill's Big JBL/Dynaco Rig

William Hardy from Vintage Amplifier Restoration was kind enough to invite us into his home for a quick listening session on his personal hifi system. You can see more of Bill's work at http://vintageamplifierrestoration.com/

Bill in his Friday afternoon best schooling some punk kids on what makes good sound.

Mike from Avanti Audio Video Plus, who invited me along on this little trip. Also, take note of the gigantic speaker, Mike's not a midget.

This is as close as I could get to a full shot of the rig.

A mix of prosound drivers and masses of tube amps run by a personally designed preamp/active crossover box along with a couple of bricks thrown in just for fun. This is DIY at it's finest. A life's work searching for his preferred sound has led to building something that makes Klipsch K-horns look small and can heat the house during the winter just off of the tubes.

Exceptional amplification is obviously a big part of this setup, using an all Dynaco tube setup that almost seems wasted because even the bass amps never blipped over one watt on the VU meters while we listened at exceptionally high levels that felt well north of 100dB. Because the tubes were hardly used they were staying very clean and I did not hear a hint of tube saturation. The amplification to me sounded more like a solid state class A than tube with very low noise floor. I actually did not notice the rolled off top end that showed up in the measurements although my ears are getting a little old so it's not much of a surprise.

The massive horn drivers are both JBL prosound parts, mounted onto custom teak veneered fiberglass bi-radial horns. These 2452 drivers are some of the best horn drivers available for producing broad range sound starting below 300Hz way up and clocking in at 110dB at 1 watt. Notice the brick for a stand holding up the $1300 drivers, I really like this guys style.

The elephants in the room are two massive bass cabinets that house 4 15 inch drivers each pointing at the back corners in an attempt to horn load them and integrate with the Big JBL horn. Based on the measurements and listening it seems to have worked very well.

Listening Impressions:

While I had to get used to the tonal balance and Wiliam's love for vinyl, everything sounded quite good out of the gate. I initially tried to listen for specifics, but I found that just relaxing and picking up on bits and pieces as they happened was the only way my mind would adjust to such a sea change from my own personal rig. After about 30 minutes I was able to work out the details and the horns just make for a great show with pinpoint imaging that does not sound small, it sounds as big as it looks, which is huge. Because of the height differential and downward tilt of the horn puts the music on a stage which i actually prefer to having what seems like the musicians have their legs cut off at the knees in some setups. I had trouble at times finding the center image, but I think that had more to do with the vinyl setup and wide placement than the speakers. Over all the wall of sound and clarity produced by such monster speakers with controlled dispersion really impressed me and I can definitely see what Bill loves about his setup. It really feels like the sound is attacking you, it's there full scale no compromise in sound stage or detail.

Measurements:

Frequency Response ended up being damn close to flat for a by ear custom crossover design, basically +-5dB from 100Hz to 15kHz at the listening position with a quick rise for some comfortable bass boost in the lower octaves. The roll off on the top above 13kHz I think is a combination of the tube amps and being off vertical axis from the top mounted horn tweeters(we were short on cables and mic stands).

First measurements using room eq wizard so how about a waterfall graph, just because it's there. This is the room response, and it looks like everything is hanging around for a little while, but it's at least consistent. traditionally if there was a big room problem it would show up here in the form of standing waves that just won't die. Nothing like that here from the measurement position, of course moving around the room standing waves are definitely there if you want to go looking for them..

The bright red line is the correction profile I put together for Bill, it's based on the Harman preferred room response paper they publish not too long ago. Took me about an hour or so work of eq work, and I'm pretty sure he will hate it as he has the sound he wants now, but it should be a good time to hear what the Harman room correction curve sounds like on some big JBL gear the next time I make it out to visit.

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