Hi crew!
I am at the beginning stages of planning my next build for Burning Amp 2025 (and maybe the Parts Express speaker competition if I can find a way to transport them there.)
The concept I'm exploring is a SLOB (slot-loaded open baffle) with the catch that ALL drivers will fire through the same slot. The slot width will be around the size of the smallest driver, so its impact will be greatest at low frequencies. It is not a MEH (multi-entry horn) but a MES (multi-entry slot) (pronounced "mess" 😛).
I am considering a WWMTMWW arrangement because I really like that in my Aura speakers. Using a wideband driver for the "T" makes it dipole across the whole frequency spectrum. I'm hoping for more bass, higher sensitivity and higher max SPL than the Aura speakers, and considering these drivers:
For the mid & tweet crossover, I am considering running T->M->M in series with a bypass cap across the mids. This means the Wib70_vHP runs fullrange with frequencies below ~640hz being shared equally by all three drivers. My motivation is to get a coherent sound (C-to-C distance < 1/4 wavelength), kinda like Perry Marshall's Bitches Brew, but with a wideband driver instead of a coax (I've yet to find a coax that I like). If the Wib70 can't handle this, I may upgrade to the Wib120 or Wib140 instead, as long as the high frequencies sound good enough.
The top view will look something like this:
For the waveguide and the mounting plate, I will use SendCutSend, with the waveguide looking something like this:
I'll keep everyone posted as the project progresses. The Kartesian drivers are supposed to arrive tonight (finger's crossed!).
Some questions:
I hope this turns into a big MES!
Cheers,
Greg
I am at the beginning stages of planning my next build for Burning Amp 2025 (and maybe the Parts Express speaker competition if I can find a way to transport them there.)
The concept I'm exploring is a SLOB (slot-loaded open baffle) with the catch that ALL drivers will fire through the same slot. The slot width will be around the size of the smallest driver, so its impact will be greatest at low frequencies. It is not a MEH (multi-entry horn) but a MES (multi-entry slot) (pronounced "mess" 😛).
I am considering a WWMTMWW arrangement because I really like that in my Aura speakers. Using a wideband driver for the "T" makes it dipole across the whole frequency spectrum. I'm hoping for more bass, higher sensitivity and higher max SPL than the Aura speakers, and considering these drivers:
- Tweeter: Kartesian Wib70_vHP
- Mids: 2 x Kartesian Wom165_vHE-e2
- Bass: 4 x Peerless XXLS-P835016 10"
For the mid & tweet crossover, I am considering running T->M->M in series with a bypass cap across the mids. This means the Wib70_vHP runs fullrange with frequencies below ~640hz being shared equally by all three drivers. My motivation is to get a coherent sound (C-to-C distance < 1/4 wavelength), kinda like Perry Marshall's Bitches Brew, but with a wideband driver instead of a coax (I've yet to find a coax that I like). If the Wib70 can't handle this, I may upgrade to the Wib120 or Wib140 instead, as long as the high frequencies sound good enough.
The top view will look something like this:
For the waveguide and the mounting plate, I will use SendCutSend, with the waveguide looking something like this:
I'll keep everyone posted as the project progresses. The Kartesian drivers are supposed to arrive tonight (finger's crossed!).
Some questions:
- Has anyone done a build like this?
- What do you think/what would you change?
- For the slot-loading part: How wide should the slot be and how much volume in the compression chamber should there be?
I hope this turns into a big MES!
Cheers,
Greg
Excellent! You've probably modelled the effects of the slot already, and there are some sophisticaed ways of doing that. But if you haven't, and want a quick'n'easy sim, see my thread here: https://www.diyaudio.com/community/...baffle-and-other-woofers.426580/#post-8004549
Oh yes! I saw that thread and it seems very apropos. I will read it more carefully and try to model the slot that way. Thanks! I haven't done any modeling yet, but I have been doing some rudimentary plywood prototyping.
I was up late prototyping in my garage with some pine boards I got from Lowe’s. I don’t have the Peerless drivers yet so I used a pair of 15” SB 15OB350 I had lying around.
Keeping in mind this is a first, unoptimized pass, the initial impressions are encouraging. The Wib70_vHP is a killer little driver that sounds great in the “midtweet + some bass” role. Highs are tweeter-like, and it can handle an impressive amount of power while still sounding smooth/effortless for such a little driver. For the mids I went with the Wib145_vHE to keep c-to-c smaller. They are very nice drivers that stay clean as I push the volume (I maxed the volume on my stereo receiver, wore ear protection, and it still sounded good). The SB 15OB350 is great for the price and works well here, but I want to keep exploring other options for the bass. I may stick with 2x15” for bass instead of 4x10” because it is a bit more compact.
The slot definitely boosts the bass, and the slot-loaded OB concept works really well here. I don’t need any attenuation of the mid or treble for bass to sound balanced, which is impressive for an OB speaker. I’m used to applying a TON of attenuation with dipole speakers, so this is a pleasant surprise.
The biggest downside to this initial design I’ve noticed is that the sweetspot is very narrow horizontally. The treble falls off quickly as I move left or right away from the slot. Listening on-axis is glorious though. I’m curious how a stereo pair would image but that would require building a second prototype (with kids and a full time job progress is slow). I think reducing the chamber depth may help with the horizontal dispersion.
The crossover right now is just a Zobel on the 15” drivers with a big series inductor (the label fell off so I’m not sure how big, but >=12mH). Plus a single cap in parallel with the mids, with a .75ohm resistor in series with the T-M-M chain. The resistor helps tame the high frequencies a little bit. The zobel helps a lot with the 15” drivers to reduce their mids.
More updates to come as I keep working on this.
Keeping in mind this is a first, unoptimized pass, the initial impressions are encouraging. The Wib70_vHP is a killer little driver that sounds great in the “midtweet + some bass” role. Highs are tweeter-like, and it can handle an impressive amount of power while still sounding smooth/effortless for such a little driver. For the mids I went with the Wib145_vHE to keep c-to-c smaller. They are very nice drivers that stay clean as I push the volume (I maxed the volume on my stereo receiver, wore ear protection, and it still sounded good). The SB 15OB350 is great for the price and works well here, but I want to keep exploring other options for the bass. I may stick with 2x15” for bass instead of 4x10” because it is a bit more compact.
The slot definitely boosts the bass, and the slot-loaded OB concept works really well here. I don’t need any attenuation of the mid or treble for bass to sound balanced, which is impressive for an OB speaker. I’m used to applying a TON of attenuation with dipole speakers, so this is a pleasant surprise.
The biggest downside to this initial design I’ve noticed is that the sweetspot is very narrow horizontally. The treble falls off quickly as I move left or right away from the slot. Listening on-axis is glorious though. I’m curious how a stereo pair would image but that would require building a second prototype (with kids and a full time job progress is slow). I think reducing the chamber depth may help with the horizontal dispersion.
The crossover right now is just a Zobel on the 15” drivers with a big series inductor (the label fell off so I’m not sure how big, but >=12mH). Plus a single cap in parallel with the mids, with a .75ohm resistor in series with the T-M-M chain. The resistor helps tame the high frequencies a little bit. The zobel helps a lot with the 15” drivers to reduce their mids.
More updates to come as I keep working on this.
Attachments
I modeled the current setup's crossover in VituixCAD. This doesn't take into account the baffle or slot, so the frequency response (particular below 100hz) is much flatter than this makes it seem. Also the peak in the high frequencies isn't as bad as it seems because it is very directional and the slot seems to absorb some of the high frequency energy. Still I might try an LPAD or shelf on the midtweet to see if I like it more than the .75mohm resistor.
I'm gonna need to read that other thread to see if I can model the baffle & slot.
I'm gonna need to read that other thread to see if I can model the baffle & slot.
What are the dimensions of the baffle and slot?
Have you seen other speakers that fire mid and treble through a slot, like this? I'm not sure I have. Isn't the slot going to do strange things to the mid and treble?
Have you seen other speakers that fire mid and treble through a slot, like this? I'm not sure I have. Isn't the slot going to do strange things to the mid and treble?
This could be because the slot mouth is effectively the radiating surface - it's like have a three-inch wide tweeter (or however wide your slot is).
OK, I noticed the dimensions above - 2.5 inches slot width. I don't see the slot depth though - maybe 8 inches? I ran a quick sim in Basta, but I'm not going to post it - it's not pretty. 😆
The sim assumes that the slot acts like a vent, basically. For the dimensions I entered, there's quite a strong resonance just above 100 Hz, and then the slot tends to suppress the mid and treble output a bit. Is that really what happens? I have no idea. Maybe it's more like a huge compression driver? (I wouldn't have thought so, to be honest, as the slot mouth has a much larger area than the mid and treble radiating surfaces.)
It would be good to see measurements, if you have any.
The sim assumes that the slot acts like a vent, basically. For the dimensions I entered, there's quite a strong resonance just above 100 Hz, and then the slot tends to suppress the mid and treble output a bit. Is that really what happens? I have no idea. Maybe it's more like a huge compression driver? (I wouldn't have thought so, to be honest, as the slot mouth has a much larger area than the mid and treble radiating surfaces.)
It would be good to see measurements, if you have any.
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Hi there,
some years ago i was thinking about a combination of slot load and front horn with 8 3.5 inch fullrange chassis , i did not make it to test it, no idea what kind of simulation could give the first idea of the outcome
- Stefano
some years ago i was thinking about a combination of slot load and front horn with 8 3.5 inch fullrange chassis , i did not make it to test it, no idea what kind of simulation could give the first idea of the outcome
- Stefano
I'm playing around with those by moving where I clamp the front baffle/waveguides to the backplane. For example:
First photo:
- Chamber Depth: 7”
- Slot width 2.5”
- Total front width: 20.5”
Second photo:
- 4.5” chamber depth
- 5” slot width
- 22.5 total baffle
I have not seen other speakers like this, which is why I'm excited to try it and share my findings.
Depends on what you mean by "strange things". With the deeper chamber I found it sounds pretty good directly on-axis, but off-axis the treble falls off very quickly and it sounds a little bit muffled (as if behind a closed door). With the more shallow chamber and wider slot mouth, these effects are mitigated substantially and it starts sounding really good. The sound is definitely not as open and airy as a simple flat-baffle dipole, but it is not overly "boxy" either. The bass is noticeable deeper and more impactful than a similar-sensitivity flat-baffle , which is a big benefit.
I've also been playing with a more "1-D horn-like" front and from initial listening impressions it seems to improve the sound and directivity (I don't like the look as much though).
I like that explanation.
I'd believe that - Those dimensions are similar to what I have in the first photo. The shallower chamber & wider slot mouth definitely sounded better. I just learned VituixCAD and guess I need to download/learn Basta next.
I don't have a good measurement setup right now - last time I tried REW with my AT-2020 I didn't believe the results at all. Maybe I should invest in an OmniMic 40k?
Sweet! From my initial experiments I think the idea can be made to work. Like everything in speaker building, the design has tradeoffs.