Wow!!
Awesome drawings! I wish this work was easy, but that degree in Mechanical Engineering was meant for someone else. I loved the physics, but the Calculus was too painful.
I have a few tenets that I could contribute to this discussion. I have conveyed these things in various discussions in the past, but a cohesive blog seems appropriate. I will address crossover experimentation, general cabinet impact (structure, baffle and volume), and implementing a bass module. My comments come from personal experience and feedback from various peers & customers over the years.
Caveat - I would like to initially convey that my comments herein should not be taken as empirical fact based on exhaustive research using the scientific method. My comments are based on experience and exposure to audience of listeners, their comments, and whether those comments "fit" within a reasonable body of knowledge.
Crossover experimentation - I discourage this. However, I did have 1 customer who completely changed the crossover and went to a very shallow slope with the 1801 drivers. He was emphatic that his crossover sounded better, but was unwilling to provide any measurements of the new crossover. I will allow that some folks might like a "different" sound and certainly the sound of many commercial speakers with whacky crossovers ( example:
http://murphyblaster.com/content.php?f=marble.html ) illicit $$ from various customers, it is my belief that most folks (i.e. me @ 10 years ago) have relatively untrained ears.
I am going get slightly off topic on my soap-box a for a few paragraphs. It is my belief & experience that quality control among driver manufacturers and a lack of concern at the speaker factory are responsible for profound speaker problems that go largely unchecked. Unfortunately, those people able to check them and provide public feedback chose to avoid possible litigation. Dennis Murphy is a Gov't regulator in Washington D.C. and is able to publish these measurement graphs without fear of reprisal. I thought about publishing some defamatory remarks several years ago, but my wife told me "NO". She had business law and fully understands the reasons for litigation. I wish to avoid this.
Anyhow, quality control is PROFOUNDLY SIGNIFICANT! Driver parameters DO change - even with most of the very best (and most expensive) drivers.
I... hesitate to do this but... I am going to "toot my own horn" - mostly. About 8 years ago when I initially chatted with Oskar Wroending about his Hiquphon tweeters, I asked Oskar, "Why do your tweeters sound so good?? I fully expected that Oskar would convey some ?trick? about a fancy piece of copper in the motor of his speakers.
Instead, Oskar consumed @15 minutes addressing the importance of quality control in his tweeters and the very simple tedious processes that result in a well built product. Yes, 15 MINUTES! And, oh, yeah, then there is the multi hand-coated tweeter dome on all Hiquphon tweeters. For those who know and understand building a consistently great product is primarily rooted in quality control. There are certainly some engineering aspects present, but enduring high quality is rooted in quality control during manufacture.
I need to get back on task?Where was I?.oh yeah, please don?t mess with the crossover.
But please do mess with the cabinet. There are a variety of things that can be done in the realm of good experimentation with the cabinet.
Slightly bigger might be preferable ? perhaps 28-30 liters. The bass will be deeper but not as tight. Simply tune the port by ear. A shorter port will be appropriate with a larger cabinet. Shorter will provide more boom. Longer will be leaner.
A larger round over on the edge of the baffle over is better. The difference between ?? radius round over and a sharp corner is not audible. The impact of a 1 ?? radius is very audible and I highly recommend this. If you can go bigger - great!
Concrete will likely sound better. One of my customers built concrete 1801 cabinets using the Faraday sound concrete brew. Then he compared them in a good setting to a pair of wood 1801 speakers. There were two pair of 1801 speakers present. The consensus was that the concrete speakers sounded better. Unfortunately, the FaradaySound website is gone. Eventually I will expeiriment with concrete ? despite the fact that concrete has profoundly low WAF (Wife Acceptance Factor).
Keeping the baffle dimensions similar is a good idea, but they really don?t have to be exactly the same as the initial design.
I don?t have them, but some folks have implemented subwoofer modules under their 1801 speakers. They use 1 module under each speaker. This can work reasonably well. Unfortunately, I can?t comment on the specifics, but perhaps Tom is able.
Tom?
