Re: Yamaha DSR215 Anyone mixed on it yet?
So Phil, what would you recommend for a mid/hi that is powered, about a grand per box, not a constant-curve line array, and loud enough for R&R in a 200 cap venue?Because I'm not seeing a lot of choice here...edit; What I and my clients are used to using in this segment is one stack a side of JBL4719's and the 212 or 215 top. That's what I'm trying to replicate volume/coverage wise but with a foolproof powered option.
Tim,
I'm not much help on talking about a specific powered product that meets those criteria at that price point. I feel like with such constraints you probably have adversely pre-selected the Yorkville. Not that there's anything wrong with yorkville, as I don't hesitate to suggest their product. That said, let me put on my loudspeaker design hat and talk about the other notion in your post. The idea that a powered speaker is automatically going to provide the best limiting is not universally true.
The fact of the matter is that it is very difficult to put enough amplifier inside a powered speaker to overdrive a quality modern low frequency driver. The 'peak limiting' in a given powered speaker may be nothing more than the amp module's clip limiter. The important limiting then is the long term thermal limiting, and there is wide variability in the sophistication of such schemes.
An advanced picture of limiting should account for a number of effects, and i'll try to most of them here briefly:
- The voice coil of a loudspeaker heats up as energy is dumped into it. Metals increase their resistance with increasing temperature due to phonon scattering.
- This changes the dc resistance (Rdc) of the voice coil (increases it)
- The change in Rdc affects the current in the voice coil, for a given input voltage, by Ohms law (V=IR). The resistance goes up and the current goes down. This change in the resistive component of the voice coil is independent of the reactive component of the impedance.
- The motive force on the cone is proportional to B*l*I, where I is the current above. Less current means less motive force for given input voltage. Crudely this can be thought of less output for a given input voltage, which we commonly call power compression.
- Also affected is the Q of the driver's electrical dampening (it increases), as the more resistive voice coil provides less electrical dampening
- This in turn changes the Q of the driver/box combination (raises it), changing the frequency response near the vent tuning frequency, and making the overall bass response more underdamped.
- Once there is sufficient heat transfer from the coil to the driver's magnetics structure, the magnetic flux strength of the magnet will be affected (it will be reduced). This further reduces the B*l*I product, because you've now reduced B.
The voice coil resistance resistance of a driver that has experienced substantial heating can be nearly 2x the standard, cold Rdc.
Functionally that means that the amplifier in the system needs to provide nearly 2x the voltage swing to reach the same cold output level. Another way of thinking of this, is that the limiting voltage threshold of a hot driver needs to be raised relative to a cold driver to keep the output level consistent once the driver has heated up. Its not that the energy into the driver has increased, but rather a greater voltage is now needed to induce the same amount of current in the voice coil.
A sophisticated limiter would measure/calculate voice coil heating and tightly control it. Further this limiter would apply corrective equalization to account for the change in the low and low-mid response due to the voice coil heating. This limiter would also adjust threshold(s) based on the true peak excursion the "hot" driver would produce for a given input voltage, accounting for the heating. None of these things are easy to implement, especially for low frequency drivers where the potentially substantial magnitude of the cone movement affects many of the parameters involved.
