PinWoofer - Jersey Jack Audio Overview

Below is the account of what we did here at PinWoofer to our Jersey Jack Pinball (JJP) electronics in an attempt to improve the backbox sound field, and to address some of the constraints inherent in the platform.

First, the JJP backbox consists of a 4in mid-range driver and 1/2in dome tweeter on each side. The speaker components themselves are well aligned to what one will find in a high fidelity speaker system having a separate tweeter/mid-range/woofer arrangement enclosed in a cabinet. However, the tweeters deform at all volume intensities and the result is a "graininess" and very obvious distorted sound field. This condition keeps the player from exploring the track at higher volume levels because it is simply unbearable to most ears. It also serves to hide (cloak) most of the amazing audio mastery present in the JJP titles.  Simply put, clarity is sacrificed.

Next, the JJP backbox speaker enclosure is at / near ear-level which differs from most other pinball platforms (but honestly, it looks VERY cool). The JJP tweeters point directly at the player, so there is something critical to consider - the mid-range backbox speakers point vertically and the sound is reflected off of internal metal plates, angled towards the player position. This is a unique speaker implementation in pinball. So, does it matter? We think it does because the mid-range is reflected towards the player as opposed to facing the player. Energy is absorbed as it propagates and reflects towards the listener perspective. This of course is not ideal. The reflected mid-range spectrum emanating from the backbox changes as energy is lost due to the reflection, and the listener receives something that has been altered by the environment, easily described as a loss of mid-range.  This loss of mid-range can be described in audio terms as "gap". So, the conclusion is that the resulting audio from the listeners perspective is not at its full potential. Skilled listeners hear the effects of this placement and readily understand the problem; casual listeners have simply described the sound as "tinny".

JJP has also taken the approach of adding a sound bar on top of the CE backbox, possibly as an avenue to address the platform issues discussed above (that is, making up for reflected mid-range speakers). The CE sound bar uses the same tweeters as the backbox, and inferior mid-range drivers compared to the backbox, so our conclusion is that the CE sound bar should be disabled when adding the PinWoofer system. (The CE sound bar has the IDENTICAL speakers and tweeters as the early JJP titles The Hobbit and The Wizard of Oz backboxes.)

In an attempt to address / mitigate the above constraints, PinWoofer set out to add back in some of the high bass and mid-range to temper the "tinny" character of the platform by making changes to our Expander Board(TM), and to continue to utilize the 4in mid-range drivers. (We also upgrade the tweeters for the late JJP titles which is vital.) We feel that we were successful considering the constraints. Feedback has been excellent for these titles and we are finding that we have something that has improved the backbox field characteristics and of course, there is no question the bass emanating from the cabinet sub is improved with the PinWoofer GT amplifier and speaker upgrade.

The network analyzer curve from our JJP Expander Board shows in part, how we have addressed backbox response through targeted filtering of the signal presented to the pre-amp. Even with observed high-end roll-off there is an abundance of high end treble.

Another remark regarding the PinWoofer Tweeter Upgrade. We discovered that the replacement of the tweeters had the effect of making the signal shaping of the Expander Board unnecessary. If you would like to delete your PinWoofer GT JJP Expander Board, the following link shows how to do that:

https://pinwoofer.com/content/PW-GT-JJP-Expander-Board-Delete-Instructions.pdf