Speaker Asylum

The Sound Lab ESL are 'full range' yet they use a crossover.

75.168.141.235

Ralph

M

In Reply to: RE: Do you consider certain large panel speakers to be "full range drivers" ? (nt posted by Presto on December 10, 2024 at 15:21:11

The Sound Lab Majestic is arguably one of the more full range drivers made.

There is a crossover in it to manage the two matching transformers which interface between the amplifier input and the driver; one is for bass and the other is for the mids and highs. Their outputs are in parallel driving the same load.

Quite a different beast from cone drivers which simply can't manage the same things! The Sound Labs aren't beamy and have bandwidth well past 20KHz, and bass response to 22Hz IIRC (might be lower).

Follow Ups:

Actually what you find - E-Stat 16:13:51 12/11/24 (2)
with either Acoustat or Sound Lab products is a blender where the output of the frequency optimized transformers is combined and sent to the full range panel.

The result is a pretty tame impedance curve vs. a "Scream Machine roller coaster" curve found on single transformer models from Sanders, Quad, etc.

Here is Dr. West's explanation:

"The requirement to have both low and high frequency transformers has to do with lower frequency transformers requiring more coil turns than higher frequency transformers to provide a suitable input impedance for an audio amplifier, and vice-versa. The reason for this is that a transformer is basically an inductance, and the impedance of an inductor is proportional to frequency. Thus, a given inductor has a lower impedance at lower frequencies than at higher frequencies and therefore requires a higher inductance (more turns on the primary and secondary coils) than a high-frequency transformer. Also, another factor needs to be considered, as the number of turns is increased the internal shunt capacitance of the coils increases and also the coil resistance is higher due to more windings. The coil resistance and the shunt capacitance act as a single-pole low-pass filter which lowers the high-frequency cut-off frequency.

In brief:

1. A low-frequency transformer with a higher number of coil windings is necessary to have an acceptable input impedance. However, the higher number of turns reduces the high frequency response and therefore the transformer cannot be used for high-frequencies.

2. A high-frequency transformer requires fewer turns to achieve an adequate input impedance and therefore cannot reproduce lower frequencies since the impedance would be too low for an amplifier to drive.

3. Without going into details, the toroid core is just one continuous metal strip that is wound into a doughnut-like core and provides better reproduction at higher frequencies.

4. The audio spectrum is essentially 20 Hz to 20,000 Hz, thus the ratio of HF to LF is 1000. This makes it nearly impossible, if not impossible, to have one transformer provide the proper input impedance for all frequencies since lower frequencies require more coil turns than higher frequencies. The only choice would be to have very low (unacceptable) impedance at low frequencies and acceptable impedance at higher frequencies, or acceptable impedance at lower frequencies (many coil turns) which would restrict the higher frequencies. Thus, we use two transformers, one that is optimized for lower frequencies and one that is optimized for higher frequencies."
- FWIW - Ralph 08:30:30 12/12/24 (1)
  One of the people on that email thread I mentioned had a matching transformer wound for him on an enormous toroid core that had full bandwidth and no need of a crossover. He seemed to think it worked a lot better than the Toroidal One backplate, but I don't know anyone that heard it since he was in Australia.
  - Can't say but - E-Stat 08:52:02 12/12/24 (0)
    "enormous transformers" are not ideal for HF reproduction or else the resulting impedance curve is not amplifier friendly like production.
    
    No roller coaster found in the speaker's range.
RE: The Sound Lab ESL are 'full range' yet they use a crossover. - Presto 11:24:59 12/11/24 (0)
Wow, I'd love to hear those!
Crossovers are not "all things evil" per se. Large coils on low-pass filters have insertion loss and cost a lot - lots of copper in the windings. Some folks prefer to minimize caps in the tweeter signal path (shunt caps a lesser evil than series ones, according to most).
Impedance bump and rise compensation and equalization for flatter response are usually good things. A 2-way 90db SPL speaker with 90db SPL tweeter is a red flag - no baffle step compensation there, which can make a 2-way design sound very lean especially if it's out in the room where stand-mounts image best. (85/86db speakers are commonly the result of equalization and baffle step compensation...)
Some might abhor the use of transformers, but, they'd then need to abhor the output stage of a single ended tube amp!
In any case, I will definitely be looking into those specific speakers if only to better understand how they work. :-)
Cheers,
Presto

Edits: 12/11/24 12/11/24

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