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You can't ignore nothing!
What about stability of the baffle? How much is thick? You're going to see the bolts, anyway. And, speaking of thickness, how is your perception exposed to the "cavity effect"? Usually you do the chamfering and leave the full piece near the hole for maximum strenght. Do you think venting is not needed? Oh well, when mounted from the back surely this won't happen.
So, don't ignore anything!
I did that in a two way - a derivative of Econowave - back in 2012/2013. Since the project uses JBL PT waveguide that moves the acoustic center of the tweeter way back, the mounting of the midwoofer was arguably beneficial for getting the acoustic centers of the tweeter and midwoofer closer at the Z axis.
It didn't measure too shabby given restraints i had at the moment. Disregard everything bellow 450Hz. Blue is in phase, and bordeaux is with tweeter out of phase.
Front baffle is 28mm thick and for mounting i used regular wood screws that are 25mm long. Given the thickness of the midwoofer frame, it worked quite well. Good thing with mounting from the back side (looks aside because some of my friends didn't like the looks) is that even if you unscrew them a milion times and the screw holes become loose, you just rotate the midwoofer 2cm and you get fresh place for screws to go into. Pulling force of only one screw that is 12mm inside the wood is enormous, let alone eight of them.
back-mounting woofer
ZVU; I really like the look of your back-mounted woofer. Very clean. I'm toying with a vintage speaker now that has original back-mounted drivers, and I'm considering beefing up the baffle board and using back-mounted stainless inserts for threaded screws.
As a comment about baffles in general, I'm surprised more people do not get aluminum plate and take it to a machine shop and have it cnc'ed. I have a stack of it from .75" up to 1.25" thick that I purchased years ago dirt cheap, just waiting for an application.
ZVU; I really like the look of your back-mounted woofer. Very clean. I'm toying with a vintage speaker now that has original back-mounted drivers, and I'm considering beefing up the baffle board and using back-mounted stainless inserts for threaded screws.
As a comment about baffles in general, I'm surprised more people do not get aluminum plate and take it to a machine shop and have it cnc'ed. I have a stack of it from .75" up to 1.25" thick that I purchased years ago dirt cheap, just waiting for an application.
I asked because you did the calculation for my project that was built from scratch by me and i've designed the crossover to work with drivers mounted the way they are.
What post no 41 is referring to is finished kit project with crossover that is already determined. In that regard it does make sense to follow what designer did and not change the position of drivers, since phase relation between the drivers is determined by it and by the crossover from the kit. Midrange and tweeter are more sensitive but there is some degree of freedom with the woofer, as you already stated.
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I would rebate the front baffle for the midrange driver, and put it above the woofer where it belongs.
Then mount the tweeter in a wave-guide keeping it's depth relative to the mid.IMHO it looks wrong with the mid on top.
jeff
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I believe Troels wanted the mid driver at ear level, so he put it on top. However, the large distance between the woofer and the midrange affects the vertical dispersion at the woofer/midrange x-over range in a negative way. I think this could be a relevant issue since the filter slopes are rather flat, resulting in a wide woofer/midrange overlap. Keeping the midrange close to the woofer would have been better in my opinion.
I would rebate the front baffle for the midrange driver, and put it above the woofer where it belongs.
Be aware that this would be a very different speaker. You'd need to redesign the x-over filters.
Also, the main purpose of a waveguide is to modify the dispersion of the driver. It's best to match the dispersion of the midrange and tweeter at their x-over frequency. Since Troels does not show any dispersion diagrams, we don't know much about their dispersion and hence we can't tell if a waveguide might make sense in this system. Don't use a waveguide only to implement time alignment between midrange and tweeter.
Yes, easier said than done.
Oh yes!
It works like this:
(1) Measure the on-axis and off-axis SPL curves of all three raw drivers on the baffle (+/- 90° or further out, in all four directions, at 10° intervals)
(2) Import these raw data to a speaker CAD software tool and design the x-over filters for linear SPL response and smooth dispersion (horizontal and vertical)
(4) Is dispersion as nice and smooth as it can be? Is a waveguide necessary?
(5) Maybe add a waveguide to the tweeter and start over at step 1
(6) Build the xover filter and make sure the acoustics work out as predicted by the CAD tool (good luck!)
That's A LOT of work. Been there, done that. It was totally worth it!
Troels has designed quite a few speakers with the tweeter mounted between the midrange and woofer.There must be a good reason for it.They have also had the midrange mounted forward of the woofer.
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he posts a horizontal dispersion plot which looks more than acceptable to me. perhaps this is why he kept the tweeter on the centreline.
i don’t expect the vertical to be so pretty but i tend to listed whilst sitting at various places around a room such that my ears are mostly at a constant height so this is less important to me
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