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Please Critique - My 1st 2-way Bookshelf Design
Looking for input/critique on my proposed 2-way bookshelf design. Any input and/or help is greatly appreciated. Comments on drivers, crossover design, enclosure design, calculations and assumptions shown, etc. would be AWESOME! I'm planning on building the enclosures myself most likely with 3/4" thick plywood and internal reinforcement baffles. I haven't nailed down the exact design of the enclosure yet and will obviously allow for displaced volume from baffles. I just wanted to make sure the components, crossover and general design looked ok before finishing the enclosure design. My target volume is 0.53 cu. ft. with 2" diameter port at 4.4" long as shown in the attached.
Comments
"One of the few 6.5" woofers with a clear, extended midrange and no real cone break-up. Excellent bass - larger than normal cone area and long xmax. Easy to work with, a LR4 slope can be obtained with a simple 2nd or even 1st order xover. Very good efficiency for a long-throw midwoofer. Works well in the Dayton 0.5cuft cabinet with a 2" vent tuned to 45Hz."
"An Outstanding Woofer For This Price Range
Is this a bunch of BS?
Using the values you provided in your writeup, you could expect the woofer to look something close to this:
That filter does a decent job as it turns out at contouring the breakup, but if you look below 1K, there will be a substantial drop off in output - this is the infamous "baffle step loss" you will hear discussed. Changing the inductor to something like a 2mH will compensate for most of that loss:
This is where that damn HDS starts becoming less attractive and something of a pain in the ass to use. That noise around 1K is very real and needs to be tackled independently of the rest of the crossover if you want to cross somewhat lower than the ~2.3k shown in the second graph.
What happens is a wide depression between 300 and 800 that will really make a lot of vocals and the meaty parts of music sound recessed an tepid. Unpleasant. The alternative is crossing higher and not using as much baffle step loss compensation, which leads to a lean bass output and probably some issues integrating the woofer and tweeter since A: the HDS has high distortion above 2K and B: it is a large diameter driver that operates ideally below 2K anyways.
I have taken to using one or two notch filters on problem drivers like this, so this is what it can look like with a pair of notch filters and and a damped second order on the woofer:
Here is said schematic:
So long story short, reading online reviews of drivers at Parts Express should be taken with a couple huge grains of salt, preferably around the rim of a margarita glass. The HDS can sound fine, but it is not the silver bullet it is often claimed to be. It kicked my ass, and I like to think I know a thing or two about hammering drivers into submission.
The RS28A on a typical cabinet:
Here is the RS28 with the network from your write-up:
(Take this with a couple more grains of salt as the measurements were taken apart a few years)
Here is approximately what you could expect to discover using your proposed network:
That is very much an approximation above, since these were measured at different times under different levels. With some work, you can build a killer two-way out of those drivers.
Speaker design is very much an engineering discipline, so it does take some time and practical experience to become proficient at it. Don't use the values I show for your crossover, since the notches are pretty much baffle dependent, and they were meant for demonstration purposes.
I do believe Hong is in SoCal, and he has proven to be a very helpful individual. Learning crossover design is hands-on and an afternoon and a six pack is a helluva way to learn it.
Long story short: the drivers are fine, just not going to fall into a great sounding speaker with four components. It is worth taking the time to learn how to design a crossover, and we are always here to help if you get to a sticking point. DO NOT be discouraged by this post, rather approach it as a problem in need of a solution - which your engineering background has definitely equipped you to do.
On the other hand, it is a deep rabbit hole that we DIY'ers tumble down if we are not careful!
Also, how do I reach Hong? Is he a member in this group?
It can be daunting entering the hobby, and I normally do not advocate kits for the sake of kits - since they are rarely documented well enough to provide useful information to someone who is considering learning design work. It is part of the problem with the hobby - new guys are told they do not know how to do design work, and are then flooded with a barrage of kits and established designs to choose from but are rarely given the background information on how the design ended up the way it did. My post above is a good example of the type of information often lacking in the more popular offerings.
Feel free to PM me if you want more information on the design I have for sale or if you have any other questions/comments. We are here to make sure you succeed on your terms - and I would be willing to assist you in learning the ins and outs of this crazy hobby.