DIY ?uestion

@sound22card, I sent you a PM so I can forward you the Fried D subwoofer plans.  This TL cabinet is 36H X 15.75X X 15D, and used an 8" driver.  Personally, I find it a much bigger step back from my O subs with their 10" driver than I or most would have expected, but I can't find the paperwork on that right now.  The benefit of the D subwoofer is that it mates perfectly (in width) with the C (pyramidal) Series satellites that sit on them to form the Valhalla System.  Think along the lines of the Wilson WATT/Puppy aesthetic.  But it will at least give you a look at one of the more highly regarded TL cabinets produced.  Fried sold a pretty good number of D subs, and very few O subs.  The IMF Electronics site used to carry a wealth of information on many of the IMF / Fried products, including these, but the content doesn't seem to come up right now.  Hopefully, it's not lost, as there is a treasure trove of documentation there.

@areed622 "I like 8" drivers that can handle at least 100W continuous and have SPLs at least 92dB and around 0.3 Qts."

You included an incredibly important detail when mentioning the Qts.  Bud Fried considered it critical importance to select a driver with as low a Qts specification as possible.  Over the years, I've learned that's exactly opposite of most opinions I find in the internet discussions, which recommend the opposite.  Bud even replaced the 10" drivers in his subs, and when he handed me a cardboard box, he explained these were the original drivers, but he was able to have Gefco make him a special pair with an even lower Qts, and those were the ones in the cabinets.  I can tell you from my Fried O subwoofers, they really bring the thunder, and apart from being a bit larger than most folks feel comfortable with, have no real weaknesses.  As I said, even when I know what's coming, for whatever reason my body will still (involuntarily) flinch when certain notes get played.

@audiokinesis, my hat's off to you, Duke.  You REALLY understand TL!

For TL theory that is backed up by measurements consider looking at the articles on my site.

www.quarter-wave.com

There is more bad information about TL's on the Internet than accurate information. The methods on my site have been used to design many TLs (100's probably) that have performed as predicted. The methods have been used by Salk Sound, Dennis Murphy, and a few other commercial TL manufacturers.

Thank you, Duke. Your experience with TL seems to mirror what I’ve read from most people apart from Bud.

Nothing proprietary at this point, most people don’t even remember who Bud Fried was. Anyway, I saw (Salk?) has been trying to resurrect the Fried name, but the products are far different than what Bud used to build. I can send you the plans for the C/6 satellites and D2 subwoofers. You can also have the crossover values from Bud’s C sats, if you want. I’m not sure if you feel comfortable with series crossovers, but even though most implement them as first order, you can alter a value called Zeta (ratio of cap to coil) to produce a steeper or more shallow rolloff than 6 dB/octave. 6 dB/octave has a Zeta value of 1.0, lower (say 0.8) values sound more forward and have a sharper rolloff, higher values (like 1.2) sound more relaxed and liquid and have a slower rolloff. Bud didn’t actually know Zeta per se, but it seemed he understood it from a practical means in terms of varying the cap to coil ratio. Bud’s crossovers are somewhat less than 1.0, and sound a bit more forward than I personally prefer.

I’ve met and received emails from more people over the years than I can remember, all with great stories about him. Most of them focus on either him writing 3 and 4 page handwritten letters to them multiple times in response to their letters or spending a couple of hours on the phone providing the same insight for those willing to pay for the call in the age of expensive long distance service. John Rutan of AudioConnection who often posts here loves to do a Bud Fried imitation that’s just like The Frog from Courageous Cat and Minute Mouse. Most don’t know Bud introduced Lowthers, Quads, Decca cartridges, Dynaudio / ScanSpeak, and other European products to America, quite impressive. I think there will never be another manufacturer like Bud.

Bud claimed to have had a real BAD experience with Focal. You may know he had a fondness for Europe coming out of his WWII service, and spent 1/4 - 1/3 of the year there. His side of the story is he went in pretty heavy with their impressive looking drivers in the early 90s, but told me the product received didn’t come close to what the product literature specified. They disagreed. While on one of his many travels through France, he claimed to have dropped in on them, and demanded a set of measurements be run in front of him to see who was right. Upon returning back home, no Fried ever used another Focal.

He wound up with Gefco for midrange and woofers, of Chicago, who are no longer in business. He claimed they produced the best drivers he ever used. They weren’t pretty (paper cones, stamped steel baskets) or seemingly advanced, but they made him happy. His own personal speakers use them, though a bit hot rodded. You can still find a few on eBay and the like. I have some, as well. For tweeters, he preferred the Hiquphon, and they’ve long featured him in their advertising. I agree they make good tweeters, but don’t think it’s wise in going with a tiny one man operation in Denmark that could ease to exist any day.

Obviously, Bud also believed in series crossovers, which he felt were the most important of the three things he believed in - the other two being TL and low Qts drivers. He didn’t develop the technology, and claimed to happen upon it during one of his meetings with Dynaudio. He was an intensely curious and outgoing person, and asked what the two sets of crossovers were, and what I’m certain was enough follow up questions to represent an actual conversation. Based on his account, they explained one set was a parallel network and the other series. He said, what’s the difference? Their answer, well, the series crossovers work and sound better (I realize that’s a subjective statement). Of course, next question, then why don’t you use them? Answer, everyone feels they’re too unusual. As for me, it took a while to get my head around them, as they seem exactly backwards with the coil seemingly on the tweeter leg and cap on the woofer leg. One day a light went off in my head, and they seemed simple and obvious. The signal either goes to the coil or the tweeter, and the cap or the woofer - ah, makes sense...

@trelja In addition to big, very LF TLs, I built a series of small TLs using 4" LF drivers. The first iteration used a higher Q driver that refused to deliver the calculated 56kHz roll-off until a bit of putty was added to the driver dust cap. The weight of the putty was calculated to drop the Q to be ≤ the .3 . This worked and effectively supported the benefits of a low Qts. That said, I am currently running a pair of big TLs that work down to 17Hz using Focal kevlar drivers with Qs around .55 but these are bi-amped and DSP controlled and never worked properly using passive second order x-overs without bottom-end compensation.