Hey guys, I've posted on here a few times about building some design s but never really got there, other then the little Zaph Mini Monitors that are basically built.
Basically what I have sitting here is what are called Mpyre Audio 65m midwoofers, they are essentially a car audio version of the Adire Extremis 6.4/8 in actual fact I think they share alot more similarities with the CSS SDX7, as it looks like they share the same frame and they use a Carbon Fibre cone which is coated on the backside with some kind of resin but they don't have a phase plug like the SDX7.
Anyway here are all the specs and those of the Extremis and SDX7 for comparison.
Mpyre Audio 65M
Fs: 35 Hz
Qms: 2.8
Qes: 0.48
Qts: 0.41
Vas: 23 liters
Re: 3.50 Ohms
Le: .005 mH
BL: 6.13
Mms: 23 grams
Cms: 0.5 mm/N
Sd: 140 cm^2
XMAX: 13mm
XMECH: 15mm
CSS SDX7
FS 34Hz
Qms 2.2
Qes 0.41
Qts 0.35
Vas 23.77 L
Re 6.4 ohms
Le 0.75 mH
BL 8.45 TM
Mms 21.91 g
Sd 127.5 sq cm
Cms 1.03 mn/N
Xmax 11.1 mm
SPL 85 dB/1W/1m
Extremis 6.4
Fs: 37 Hz,
Qms: 3.3,
Qes: 0.36,
Qts: 0.31,
Vas: 27 liters,
Re: 3.5 Ohms,
Le: 0.11 mH;
BL: 6.7 N/A,
Sd: 140 cm^2,
Cms: 1 mm/N,
Mms: 19 grams,
Xmax 13mm on way.
Extremis 6.8:
Fs 30 Hz
Qms 2.54
Qes .383
Qts 0.332
Vas 33.2 liters
Re 7.02 ohms
Le 0.13 mH
BL 9 N/A
Sd 140 cm^2
Cms 1.2 mm/N
Mms 23.3 grams
Xmax 13mm one way
SPL 86db 1w/1m
So I was going to use these in my car but have instead gone for a 8" Morel for midbass. So I now have 2 pairs of these drivers here doing nothing and I thought why not use them in a nice Home Audio design using two per cabinet, which should provide me with an abundance of low end response for good integration to a sub and also for movies. I went searching for designs and couldn't find anything other then 2 way designs using single drivers per cabinet, which isn't really what I'm looking for. I want to build a nice floorstander. So does anyone know of any nice designs using twin Extremis or SDX7's in either a 2.5 or I think a 3 way would be best as I doubt the ability of these things to actually play much over 1.5k cleanly as the one thing I hate is a heavy sounding midrange. Or any designs that you think could be easily adapted for my drivers.
If not, do you have any suggestions on what to read up on before I attempt my own design, I have started reading through all the information and links provided in the forums wiki which is great.
Thanks
Luke
Basically what I have sitting here is what are called Mpyre Audio 65m midwoofers, they are essentially a car audio version of the Adire Extremis 6.4/8 in actual fact I think they share alot more similarities with the CSS SDX7, as it looks like they share the same frame and they use a Carbon Fibre cone which is coated on the backside with some kind of resin but they don't have a phase plug like the SDX7.
Anyway here are all the specs and those of the Extremis and SDX7 for comparison.
Mpyre Audio 65M
Fs: 35 Hz
Qms: 2.8
Qes: 0.48
Qts: 0.41
Vas: 23 liters
Re: 3.50 Ohms
Le: .005 mH
BL: 6.13
Mms: 23 grams
Cms: 0.5 mm/N
Sd: 140 cm^2
XMAX: 13mm
XMECH: 15mm
CSS SDX7
FS 34Hz
Qms 2.2
Qes 0.41
Qts 0.35
Vas 23.77 L
Re 6.4 ohms
Le 0.75 mH
BL 8.45 TM
Mms 21.91 g
Sd 127.5 sq cm
Cms 1.03 mn/N
Xmax 11.1 mm
SPL 85 dB/1W/1m
Extremis 6.4
Fs: 37 Hz,
Qms: 3.3,
Qes: 0.36,
Qts: 0.31,
Vas: 27 liters,
Re: 3.5 Ohms,
Le: 0.11 mH;
BL: 6.7 N/A,
Sd: 140 cm^2,
Cms: 1 mm/N,
Mms: 19 grams,
Xmax 13mm on way.
Extremis 6.8:
Fs 30 Hz
Qms 2.54
Qes .383
Qts 0.332
Vas 33.2 liters
Re 7.02 ohms
Le 0.13 mH
BL 9 N/A
Sd 140 cm^2
Cms 1.2 mm/N
Mms 23.3 grams
Xmax 13mm one way
SPL 86db 1w/1m
So I was going to use these in my car but have instead gone for a 8" Morel for midbass. So I now have 2 pairs of these drivers here doing nothing and I thought why not use them in a nice Home Audio design using two per cabinet, which should provide me with an abundance of low end response for good integration to a sub and also for movies. I went searching for designs and couldn't find anything other then 2 way designs using single drivers per cabinet, which isn't really what I'm looking for. I want to build a nice floorstander. So does anyone know of any nice designs using twin Extremis or SDX7's in either a 2.5 or I think a 3 way would be best as I doubt the ability of these things to actually play much over 1.5k cleanly as the one thing I hate is a heavy sounding midrange. Or any designs that you think could be easily adapted for my drivers.
If not, do you have any suggestions on what to read up on before I attempt my own design, I have started reading through all the information and links provided in the forums wiki which is great.
Thanks
Luke
Last edited:
This site has a method for combining different drivers in a BR box; I've tried it, works very well.: http://www.fortunecity.com/rivendell/xentar/1179/theory/dddllqd/dddllqd.html
As you say, the limiting factor will be how high those drivers can play, unless you get a good tweeter that can play low(SEAS 27BFCG?)
As you say, the limiting factor will be how high those drivers can play, unless you get a good tweeter that can play low(SEAS 27BFCG?)
But I'm not combining different drivers, I have 4 drivers of the Mpyre's which aren't really a low Q driver, the only reason I posted the specs of the Extremis and SDX7 was for people to see the similarities.
Thankyou though as I still read through that page and it was quite interesting.
Luke
Thankyou though as I still read through that page and it was quite interesting.
Luke
Greets!
FWIW, when I loaded these specs in WinISD PRO the CSS and Adire driver's T/S specs line up close when inputting the preferred Mms, Cms, etc., specs, but the Mypre isn't even in the ballpark in comparison, though of course without measuring all these we no idea what they really are:
http://www.hometheatershack.com/for...loadable-winisd-pro-files-mpyre-audio-65m.wdr
Anyway, don't know of any designs, but a bipole tower (aka MLTL) seems a good choice, then mate it to a suitable Fostex or similar big tweeter ~3" 'FR' driver with a 1st order XO and acoustically roll off the rear driver as required for a nice minimalist 2.5 way.
GM
edit: Hmm, just 'ran the numbers' for a 32 Hz EBS and the vents are too long, so a TQWT is a better choice.
FWIW, when I loaded these specs in WinISD PRO the CSS and Adire driver's T/S specs line up close when inputting the preferred Mms, Cms, etc., specs, but the Mypre isn't even in the ballpark in comparison, though of course without measuring all these we no idea what they really are:
http://www.hometheatershack.com/for...loadable-winisd-pro-files-mpyre-audio-65m.wdr
Anyway, don't know of any designs, but a bipole tower (aka MLTL) seems a good choice, then mate it to a suitable Fostex or similar big tweeter ~3" 'FR' driver with a 1st order XO and acoustically roll off the rear driver as required for a nice minimalist 2.5 way.
GM
edit: Hmm, just 'ran the numbers' for a 32 Hz EBS and the vents are too long, so a TQWT is a better choice.
Last edited:
Interesting idea with the TQWT but I'm thinking i'll stick with a traditional vented chamber, until I get a chance to do some measurements to check the specs I think i'll go with 50L tuned to about 35hz which is what WINISD is telling me and what UNIbox is telling PeteMcK.
Now I've been looking at a few mids and tweeters, for tweeters I'm liking the Seas 27TDFC otherwise the 29TFFW and also the Vifa XT25 are looking good. Does anyone else have any other suggestions or reasons to take one of those listed over another.
Now mids I'm totally up in the air about, I can get Peerless 4" HDS mids and I know these are meant to be great but they don't seem as popular as there reputation seems. So I've been looking at drivers like the Vifa PL11MH09-08 and also the Seas MCA12RC and the MCA15RCY or even the CA15RLY, I've even considered drivers like the CSS CR/FR125 series.
I guess mids is where I'm having the biggest difficulty deciding as I'm not sure weather to go with a 4" or weather to try and keep up with the twin midwoofers am I going to need a 5" midrange. Also how large a frequency range I'm I going to need it to cover, I'm heavily involved in Car Audio and for that I follow the chain of thought that to try and get your midrange to go as high and low as practical 300hz -6/7khz for example, but is this really necessary or even recommended for a three way tower or can I play the midwoofers up higher and tweeter lower.
Thanks
Luke
Now I've been looking at a few mids and tweeters, for tweeters I'm liking the Seas 27TDFC otherwise the 29TFFW and also the Vifa XT25 are looking good. Does anyone else have any other suggestions or reasons to take one of those listed over another.
Now mids I'm totally up in the air about, I can get Peerless 4" HDS mids and I know these are meant to be great but they don't seem as popular as there reputation seems. So I've been looking at drivers like the Vifa PL11MH09-08 and also the Seas MCA12RC and the MCA15RCY or even the CA15RLY, I've even considered drivers like the CSS CR/FR125 series.
I guess mids is where I'm having the biggest difficulty deciding as I'm not sure weather to go with a 4" or weather to try and keep up with the twin midwoofers am I going to need a 5" midrange. Also how large a frequency range I'm I going to need it to cover, I'm heavily involved in Car Audio and for that I follow the chain of thought that to try and get your midrange to go as high and low as practical 300hz -6/7khz for example, but is this really necessary or even recommended for a three way tower or can I play the midwoofers up higher and tweeter lower.
Thanks
Luke
What do you guys think of using a pair of mid ranges? Something along the line of these > http://www.madisound.com/catalog/product_info.php?products_id=1616 Most likely in a MTMWW arrangement.
Ok, so I've decided I'll go with a TMWW design using the twin 65m's in a front vented 50L chamber tuned to 35hz, then i'll use a Seas MCA15RCY for midrange (most likely rear vented chamber) and the Seas 27TDFC for the tweeter.
My reasons for going with the larger 5" midrange was for better dynamics, plus I thought I should try and keep my sensitivity similar across all the drivers, since the tweeter is 90db the bass section will end up with a final sensitivity approaching 91db since each driver is 85db then +3 for two drivers and +3 again for the vented alignment. So I thought the smaller 4" Seas driver would struggle to keep up and matching them all through the xover would become quite difficult. So by going with the larger 5" unit I've kept sensitivity similar, allowing easier integration I thought.
Now before I go any further then basic enclosure outer shape etc... I'm looking to get some software to assist me with the design. Now I was thinking of getting the Dayton WT3 so that I can get actual true t/s parameters for all the drivers. But then I was looking at programs like BassBox Pro and Xover Pro and wondered weather I should look at these instead or can I do without those, are they really just nice to have items, whereas getting accurate t/s specs I imagine is alot more critical, especially when I consider by the time I get down to the finer details of xover design it's likely to be some time from now.
What do you think guys? Am I on the right path, or at least anywhere close to it?
My reasons for going with the larger 5" midrange was for better dynamics, plus I thought I should try and keep my sensitivity similar across all the drivers, since the tweeter is 90db the bass section will end up with a final sensitivity approaching 91db since each driver is 85db then +3 for two drivers and +3 again for the vented alignment. So I thought the smaller 4" Seas driver would struggle to keep up and matching them all through the xover would become quite difficult. So by going with the larger 5" unit I've kept sensitivity similar, allowing easier integration I thought.
Now before I go any further then basic enclosure outer shape etc... I'm looking to get some software to assist me with the design. Now I was thinking of getting the Dayton WT3 so that I can get actual true t/s parameters for all the drivers. But then I was looking at programs like BassBox Pro and Xover Pro and wondered weather I should look at these instead or can I do without those, are they really just nice to have items, whereas getting accurate t/s specs I imagine is alot more critical, especially when I consider by the time I get down to the finer details of xover design it's likely to be some time from now.
What do you think guys? Am I on the right path, or at least anywhere close to it?
Luke, you're on the right track (although I'd go sealed for the mid unit).
Don't forget to take Baffle Step compensation into account in your sensitivity calculations, a few dB extra in the bass is a good thing...
For Software, ARTA is good:
ARTA http://www.fesb.hr/~mateljan/arta/download.htm
ARTA Jig - http://zobsky.blogspot.com/2008/01/simple-loudspeaker-measurement-jig-for.html
Don't forget to take Baffle Step compensation into account in your sensitivity calculations, a few dB extra in the bass is a good thing...
For Software, ARTA is good:
ARTA http://www.fesb.hr/~mateljan/arta/download.htm
ARTA Jig - http://zobsky.blogspot.com/2008/01/simple-loudspeaker-measurement-jig-for.html
Thankyou for bringing up Baffle step, I'll do some reading into as I didn't realise it had a big effect on bass, I was going to read into it later down the path when I was looking at xover design as I thought I made need to compensate for it through the xover.
My next question is i've done a little reading on driver spacing, and from what i can tell I'm really only concerned about my mid to tweeter distance. Do I need to look at my spacing from the centre of my tweeter and mid to the cabinet edges upper and sides. Should I look at keeping my tweeter centre further then the distance of the lowest xover point (wave length) I may consider.
Thanks again
My next question is i've done a little reading on driver spacing, and from what i can tell I'm really only concerned about my mid to tweeter distance. Do I need to look at my spacing from the centre of my tweeter and mid to the cabinet edges upper and sides. Should I look at keeping my tweeter centre further then the distance of the lowest xover point (wave length) I may consider.
Thanks again
I had a read through the ARTA links and I think i'll go with that since it can do my driver measurements, plus my FR etc measurements once I further along in the design and construction.
Should I still invest in other software like BassBox Pro and or xover Pro or are there freeware programs that can do all I need?
Should I still invest in other software like BassBox Pro and or xover Pro or are there freeware programs that can do all I need?
Just reading and thinking about baffle step, and they talk about the width of the baffle, but by width of the baffle to they really mean in reference to the centre of the driver to the edge of the enclosure, since the wave is radiating out from any point of the driver, aren't we really concerned about the distance from the driver to the edge of the enclosure. Or is it the 1/2 wave length that is actually causing the baffle step issue, which explains why we are concerned about the full baffle width.
Ideally, you want to adhere to the < 1/4 WL driver spacing criteria between all drivers, but this is impractical unless done like a Unity horn concept, so up to 1 WL of the XO point is considered the max acceptable, though at long enough listening distances where the driver spacing acoustically appears as a point source it can be increased somewhat. Our hearing acuity affects it also, so up high and down low where it's pretty much non-existent there's a great deal of latitude. Good thing too, otherwise we wouldn't be able to tolerate wide BW performances in a typical size HIFI/HT app.
From what others have posted over time, I personally would pass on BBP6 and buy LspCad instead. That said, there's so many excellent free/inexpensive software available now that I only use the relatively high $$$ LspCad for the occasional in-room response of a typical sealed or vented speaker system, which is almost never these days.
Eigenmodes (standing wave) are 1/2 WL resonances, so baffle width plus its end correction is just that for its modes. Ditto between the driver and any baffle edge, so offsetting drivers relative to baffle edges is all about averaging out these eigenmodes only. Ideally, you'd use some form of damping to make its edges ~ acoustically transparent, i.e. acoustically large round overs, covering with damping material with the right physical properties for the BW or similar.
Baffle step has nothing to do with eigenmodes per se, it's all about WLs too long for the baffle to have any directivity control, so sound waves being spherical, they wrap around/fall away from it, ergo lose intensity (SPL) up to 6 dB every doubling of distance, though down low the WLs are so long that it shows up as one or more dips/boosts in the response due to various wall/floor/corner/large furniture, etc. boundary interactions that when combined with other speaker summed outputs can turn a flat signal response into something that looks more like a coarse saw blade profile up to where the various baffles finally starts to smooth it all out. Due to this, 3-4 dB of BSC is usually adequate in a typical HIFI/HT app where the speakers are well away from any boundaries rigid/massive enough to be reflective in this BW.
GM
From what others have posted over time, I personally would pass on BBP6 and buy LspCad instead. That said, there's so many excellent free/inexpensive software available now that I only use the relatively high $$$ LspCad for the occasional in-room response of a typical sealed or vented speaker system, which is almost never these days.
Eigenmodes (standing wave) are 1/2 WL resonances, so baffle width plus its end correction is just that for its modes. Ditto between the driver and any baffle edge, so offsetting drivers relative to baffle edges is all about averaging out these eigenmodes only. Ideally, you'd use some form of damping to make its edges ~ acoustically transparent, i.e. acoustically large round overs, covering with damping material with the right physical properties for the BW or similar.
Baffle step has nothing to do with eigenmodes per se, it's all about WLs too long for the baffle to have any directivity control, so sound waves being spherical, they wrap around/fall away from it, ergo lose intensity (SPL) up to 6 dB every doubling of distance, though down low the WLs are so long that it shows up as one or more dips/boosts in the response due to various wall/floor/corner/large furniture, etc. boundary interactions that when combined with other speaker summed outputs can turn a flat signal response into something that looks more like a coarse saw blade profile up to where the various baffles finally starts to smooth it all out. Due to this, 3-4 dB of BSC is usually adequate in a typical HIFI/HT app where the speakers are well away from any boundaries rigid/massive enough to be reflective in this BW.
GM
Thanks for all that GM, it's starting to make alot more sense now! You talk about reducing eigenmodes by using rounded edges, and acoustic damping material on edges.
I had planned on rounding off my edges to some degree, but I'm wondering now about wrapping the edges with something like felt or alcantra or even the entire front baffle. But in reality is a little bit of Alcantra really going to be of any noticable benefit.
I've attached a few rough mockups of the final design, I'm thinking I may have to make some changes regarding driver spacing, I might try and bring the mid and tweeter closer and I might lower the midfwoofers and seperate them more.
What you might notice is the port goes all the way back to the rear wall, so i've got a few options here, I can either put a bend in the port, but I'm not sure if this is a bit of a no-no for this kind of design, or I can make it a slot port instead which you don't seem to see for Home Audio stuff. Is there a reason for that?
Plus it was my first time using any kind of design software so it's alittle cluttered looking but I have to say the program I used which was Google Sketch-up was nice and simple to use.
I had planned on rounding off my edges to some degree, but I'm wondering now about wrapping the edges with something like felt or alcantra or even the entire front baffle. But in reality is a little bit of Alcantra really going to be of any noticable benefit.
I've attached a few rough mockups of the final design, I'm thinking I may have to make some changes regarding driver spacing, I might try and bring the mid and tweeter closer and I might lower the midfwoofers and seperate them more.
What you might notice is the port goes all the way back to the rear wall, so i've got a few options here, I can either put a bend in the port, but I'm not sure if this is a bit of a no-no for this kind of design, or I can make it a slot port instead which you don't seem to see for Home Audio stuff. Is there a reason for that?
Plus it was my first time using any kind of design software so it's alittle cluttered looking but I have to say the program I used which was Google Sketch-up was nice and simple to use.
Attachments
You're welcome!
Assuming you mean Alcantara, no, it won't make enough difference to matter. All it will do is slow the eigenmodes down in frequency a fractional amount due to friction. A good way to do it is mount the drivers in individual tubes, then fabricate an open cell foam 'box' to encapsulate them. Or layer them up in wood, then beginning at the driver's flanges, angle cut away as much as you can to make a ~truncated pyramid shape. Or do as B&W and shape them as individual teardrops.
Bends are OK and help to lower vent pipe harmonics output.
Tube vents are way cheaper in materials/labor and for the DIYer, much easier to change tuning.
Yeah, I need to spend a lot less time helping folks, so I can learn how to use all the nifty computer tools available these days..........
GM
Thanks again for all that! Yes I did mean Alcantara. Your suggestion of mounting the drivers in a tube end and then surrounding them with open cell foam sounds interesting, I actually have lots and lots of open cell foam here, but I don't think that would meet the WAF so I might leave it for this project but it's definitely got my interest for a future project. I'm thinking of a traditional cab but with the drivers mounted forward 2inches in spacer rings, and then have most of the front baffle covered with open cell foam so that it sits flush with the drivers.
You definitely had me seriously considering a truncated front panel though, but I think I'm already making this project hard enough for myself. I think I might try and implement that into a more modest two way design in the future.
Bends it is! I was just concerned as I couldn't remember seeing a DIY project that incorporated a bend in the tube port, other then in subs.
Too keep this simple for myself, I get the feeling my principle interest as far as driver positioning is simply to make sure my baffle width doesn't correlate with a frequency near my xover point. That way I only have to implement a BSC circuit for one driver.
Thanks again.
You definitely had me seriously considering a truncated front panel though, but I think I'm already making this project hard enough for myself. I think I might try and implement that into a more modest two way design in the future.
Bends it is! I was just concerned as I couldn't remember seeing a DIY project that incorporated a bend in the tube port, other then in subs.
Too keep this simple for myself, I get the feeling my principle interest as far as driver positioning is simply to make sure my baffle width doesn't correlate with a frequency near my xover point. That way I only have to implement a BSC circuit for one driver.
Thanks again.
Ok so here is what i'm pretty sure will be the final design, i've left the back panel off so you can see the bracing and internal structure better.
The lower chamber is 50-52litres once you take into account space taken by drivers, port, and bracing. The port (35hz tune) shown isn't to length it's just there for reference purposes. the upper midrange chamber won't be as deep as that as there will be another panel in it that reduces the depth to achieve a final volume of about 4.5-5L's and there will be a rear exiting port that will most likely be stuffed to make it like an acoustic vent, I stole the idea from this design, http://www.troelsgravesen.dk/PMS.htm and if it works for him I have no doubts it's a proven technique.
The small chamber at the base of the cab is for xover placement and I can also put some extra weight in the base if I feel it's necessary.
The actual depth of the whole cab once the rear panel is in place will be 35cm and it's 27cm wide, and the construction will be 25mm MDF, and the front edges will be rounded off.
Now I believe the next step is to order my drivers and take some t/s spec measurements free air as well as some FR measurements and then to build the cabs per this design (unless anyone can point out any flaws in the design, please do if you think I've made a big stuff up) and once I have the cabs built mount the drivers and start taking impedance measurements etc... so I can start work on the xover design, as if i'm thinking correctly impedance measurements should be taken with the drivers in there cab rather then free air, or have I got that mixed up?
Thanks again
Luke
Shot at 2009-09-01
Shot at 2009-09-01
Shot at 2009-09-01
The lower chamber is 50-52litres once you take into account space taken by drivers, port, and bracing. The port (35hz tune) shown isn't to length it's just there for reference purposes. the upper midrange chamber won't be as deep as that as there will be another panel in it that reduces the depth to achieve a final volume of about 4.5-5L's and there will be a rear exiting port that will most likely be stuffed to make it like an acoustic vent, I stole the idea from this design, http://www.troelsgravesen.dk/PMS.htm and if it works for him I have no doubts it's a proven technique.
The small chamber at the base of the cab is for xover placement and I can also put some extra weight in the base if I feel it's necessary.
The actual depth of the whole cab once the rear panel is in place will be 35cm and it's 27cm wide, and the construction will be 25mm MDF, and the front edges will be rounded off.
Now I believe the next step is to order my drivers and take some t/s spec measurements free air as well as some FR measurements and then to build the cabs per this design (unless anyone can point out any flaws in the design, please do if you think I've made a big stuff up) and once I have the cabs built mount the drivers and start taking impedance measurements etc... so I can start work on the xover design, as if i'm thinking correctly impedance measurements should be taken with the drivers in there cab rather then free air, or have I got that mixed up?
Thanks again
Luke
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Shot at 2009-09-01
An externally hosted image should be here but it was not working when we last tested it.
Shot at 2009-09-01
An externally hosted image should be here but it was not working when we last tested it.
Shot at 2009-09-01
At a glance:
The driver offset isn't an acceptable acoustic ratio and of course there's no such thing as too much corner round-over until it becomes hemispherical.
Unless the XO is very low, the woofers should be offset too if narrower than the flat portion of the baffle.
Woofers should be physically butted together and either as close as practical to the mid or down at floor level if the XO point/slope is low, high enough. Note that their acoustic center is centered between them if the lower one isn't rolled off enough to be inaudible through the upper bass/mids XO BW.
Woofer chamber is long enough for 1/4 WL vent loading, so restrictive window bracing should be avoided and vent location optimized for best performance. Note that if port damping is used it doesn't need to be as long.
XO chamber needs to be damped enough to not have any audible cavity resonances, so at minimum a 2-3x thickness woofer chamber bottom plate is required to keep it from potentially 'drumming'.
Note that rigidity is a key element in cab design and if made from MDF, then it takes a ~1.125" thickness to match the base rigidity (MOE) of 19 mm Baltic Birch or similar void free plywood, so look to Dave p10's various bracing schemes to raise the relatively thin MDF's rigidity. Braced as he shows and you can get by using 3/4", reducing toxic dust and wear n' tear on equipment.
GM
The driver offset isn't an acceptable acoustic ratio and of course there's no such thing as too much corner round-over until it becomes hemispherical.
Unless the XO is very low, the woofers should be offset too if narrower than the flat portion of the baffle.
Woofers should be physically butted together and either as close as practical to the mid or down at floor level if the XO point/slope is low, high enough. Note that their acoustic center is centered between them if the lower one isn't rolled off enough to be inaudible through the upper bass/mids XO BW.
Woofer chamber is long enough for 1/4 WL vent loading, so restrictive window bracing should be avoided and vent location optimized for best performance. Note that if port damping is used it doesn't need to be as long.
XO chamber needs to be damped enough to not have any audible cavity resonances, so at minimum a 2-3x thickness woofer chamber bottom plate is required to keep it from potentially 'drumming'.
Note that rigidity is a key element in cab design and if made from MDF, then it takes a ~1.125" thickness to match the base rigidity (MOE) of 19 mm Baltic Birch or similar void free plywood, so look to Dave p10's various bracing schemes to raise the relatively thin MDF's rigidity. Braced as he shows and you can get by using 3/4", reducing toxic dust and wear n' tear on equipment.
GM
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