Bud Fried Towers

[TLS Guy]

Could you maybe elaborate on what you mean by "better phase response"? Better than what? And are you referring to integration of the drivers, or something else?

Sorry Dennis! I should have been more specific. I'm referring to the phase angles between voltage and current. You will note the load is in fact very close to resistive, in that the maximum deviation is from -10 degrees to +ve 20 degrees. The graph line on the whole though is very flat.

Here is a three way ported enclosure, with my best efforts to keep the load as resistive as possible. Crossover points 400 Hz and 4 kHz.

There is a narrow dip of -40 degrees associated with the 400 Hz crossover and narrow variation of -10 degrees to + 45 degrees associated with the 4 KHz crossover. However it took a part count of 29 per crossover to get it to that point.

Of course a lot of parallel crossovers look pretty decent without much fuss. This is the two way crossover of the shorter lines in my mains. There is one peak of impedance form the line tuning, as there should be. Maximum phase angles - 20 degrees to + ve 20 degrees.

Of course drivers are inductive, so even with no crossover the plot is not resistive.

Here is the data for the long lines of the speakers. For the purpose of measurement the drivers were connected in parallel. However each driver has a separate amplifier, as both drivers are fed the same signal below 60 Hz, but the top driver is also fed the BSC correction for the speaker. These crossovers are active. There is a gentle swing form - ve 8 degrees to +ve 8 degrees around the pipe tuning point.

So there is no passive filter insertion here.

As per the late John Wright's recommendation for dual TL loudspeakers the lines are tuned a half octave apart, as you can see from the impedance peaks.

 

[gene]

That certainly tracks my experience. I ended up crossing the tweeter fairly high, and the slope transitions from a fairly gradual roll-off to a very steep slope by the time it hits 2 kHz. Like you, I can't see any point in straining the tweeter below its passband.

sounds like you and Jim are on the right path to building a better Fried speaker than Fried. You're applying real science instead of witchcraft or maybe a better mix of science and witchcraft since you need both when it comes to loudspeaker design.

 

[gene]

Well not like a resistor, but they do have a better phase response and their impedance curve is not generally wild.

Here are the phase angles and impedance curves of a passive series crossover for my rear backs, that used to be my studio monitors. Target crossover points, 900 Hz and 5 kHz. The impedance curve shows the TL response with one peak at 90 Hz. That is because it is a TL designed to fully loose the output of the mid range driver, and make a totally neutral enclosure to absorb the rear radiation.

This speaker is another dual TL, which is a four way design with the lower crossover electronic. So it is biamped, but with a three way crossover to the upper three drivers.

Note that the impedance curve is very flat and that the maximum impedance variation is five ohms.

I would not recommend series crossovers a first design choice, But for this speaker it turned out the best choice.

I played these speakers to Bob Carver when he was in Grand Forks, and he was totally blown away. A really funky design, but they work and were my reference speakers for over 20 years.

The scale of that measurement is too wide, you can't really see what is going on.

Here is a multi driver RBH speaker with a very flat impedance and pretty begin phase response. This speaker has 9 drivers so its quite a feat for such a complex design.

Impedance Full Screen Image — Reviews and News from Audioholics

 

[TLS Guy]

I think if you click the + icon to 150% you ca see what is going on very well.

 

[Dataman1]

Oh Boy Bud Fried was quite the myth perpetuator. I recall on a phone call with him, he once told me metal drivers are junk and any speaker that doesn't use a first order series crossover and a transmission line enclosure is also junk. He always claimed his speakers measured like a resistor but never furnished the measurements to prove it. He was an interesting character to say the least and he certainly didn't keep his opinions to himself

We did a little study of series vs parallel crossovers (1st order in accordance to Fried Gospel). Ironically you can make the response of either network look identical.

Series vs Parallel Networks - First Order Comparison — Reviews and News from Audioholics

That being said, I'd still love to hear the new line of Fried speakers.

"These simulations have revealed that first order series and parallel networks can be designed to exhibit very similar transfer functions as evident by their similar input impedance, frequency response, transient analysis, summed output impedance, and phase response. However, under a reactive load such as a loudspeaker, both parallel and series networks must be Zobel compensated to restore equivalent filter responses to their original responses during purely resistive loading. The series network is probably a better choice than parallel for a number of reasons. It retains a flat response even when the driver characteristics change, and is to an extent "self correcting". Implementation is no more difficult than for an equivalent parallel network, and the same component values are used. On the negative side, woofer back EMF suppression is significantly worse than with a parallel network - it is up to the designer to determine if this is likely to cause a problem.

Finally, it must be remembered that any first order network dictates that the drivers will have significant power applied at frequencies where their performance will be rapidly deteriorating, however for a system that will never be operated at high power, the performance can be very satisfying."

This is from the study mentioned above, yes?

Doesn't it in fact say: "The series network is probably a better choice than parallel for a number of reasons."

And isn't the point about the back EMF on the woofer reasonably dealt with by using a transmission line enclosure?

Hence: Series Crossover+ Transmission Line= Fried; and that's why they have a loyal following?

 

[Dennis Murphy]

I read all that when I started into the design. And if I were using a first order electrical crossover, I might opt for a series across the board. Things get much murkier when you compare higher order crossovers. A first order electrical circuit of any kind will produce poor results with most combinations of tweeters and woofers. I certainly couldn't get an acceptably flat response with the drivers used on the Fried towers, even though they are very high quality and smooth units.