How to use the Xmax Guarantee 

Getting the most from your Ridge driver.

Knowing where the limit of the driver and/or the amp is is challenging. I am here to help. First lets discuss design and set up.

Speakers have areas of high efficiency and areas of low efficiency. This follows the impedance curve of the driver.

At a given power level set on your amp the driver will use a lot of the amps power (volts or amperes) to produce certain frequencies, while other areas of the bandwidth will use very little power. Those parts that have an easy time (more efficient zones of operation) can be eq'ed more aggressively if they are not at the limits of stroke, but we need to know where the driver is in relation to its maximum excursion threshold. So this need is best served by getting a full picture of what the amp can do when paired with the driver in question.

This is how to go from native response to eq'ed response, aka EQ profiles. After you have reflection free eq'ing done, then you can go to room corrected response. This does a few things: 1) it allows you to drive the sub based on your taste before the room becomes a factor, 2) the room can be dealt with separately while knowing where the real limits of the driver are, thereby assuring you that your room correction will not go past the limit of the subwoofer. However, you can't get to that point without knowing what your amp can actually do when combined with its very particular load (impedance curve, aka the sub). This is the design work. Knowing where the limits are means getting ground plane measurements outside (reflection free) and finding the limits of the sub and amplifier using measuring tools.

The workaround would be to verify using the Xmax guarantee (which is the biggest difference with Ridge LDLC subs) with your simmed power at Xmax, then find the power level that fits and allows for the best tuning. This would side step going outside for ground plane measurements and get you closer to Xmax operation. But you have to trust your meters, they have to be on point. And this is why doing both outside ground plane measures while verifying with a meter is the best way to know 100% what is going on. You can test this by simming the tested data-bass units and then stacking those sims against data-bass results. This is the verification process that the Xmax guarantee actually works.

Here's a simplified step by step.

  1. Sim at Xmax.

  2. Record sim power at frequency intervals, such as CEA 2010 intervals.

  3. Run the amp and check volts and amps with meters (don't use cheap meters, you need to trust the reading) using waves, not sweeps.

  4. Go up to highest simmed point on output power running the amp loaded (sub hooked up) and record amp settings as you move up the bandwidth. CEA 2010 frequency steps work good for this.                                                                                                                                                                     Example:  At Xhz the sim says 20 amps and 55 volts. But your amp hits 20 amps at 40 volts at that frequency. Stick to 20 amps as the max, as that would be the amperage limit of the driver and pushing further has risks. This is also an indication of how far your sim power deviates from the ability of the amplifier.

  5. Use the amp setting that gives the best tuning abilities (best headroom) to achieve the EQ profile you wish to have.

  6. Tune system for allowable amp output response (what the amp can do at the limit of the sub or vise-versa). This is math where you calculate tuning based on the amp settings and running waves at frequency points at that amp setting.

  7. Then tune based on calculated available power and calculated headroom based on close mic (approx. 2 inches around 70 dB measured driver output or you'll pop your mic). Create and save your EQ profile/s. Remember this is void of room gain.

  8. Set your limiters, if you have them. These can be voltage, amperage, or a protection lockout mode when the amp clips or thinks it sees DC voltage. This is your system protection. If you do not have a limiter on the output side of your amp, then the only protection it has is your EQ work and gain setting.

  9. Set the amp output level to the calculated level found in step 4. You can set your headroom level at this point by adjusting the gain up or down.

  10. Run response sweeps and correct for room response at MLP. Try to not EQ too much. Over EQing can result in overlap of frequencies fighting each other and sounding stressed. This is noticed by localization, lack of clarity, or a stressed audio sound.

  11. And your done, you're getting the most from your sub. If you are apprehensive of your work, cut the gain or get more aggressive with your limiter.


If you are not experienced in extreme subwoofers and DIY subwoofers, there is a chance that damage may occur to the driver or the amplifier. Harbottle is not responsible for any damage that may occur in the testing, implementation, or use of a Harbottle DIY product.