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Care to critique my customized Voxel design w/slot port?
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Old 11th August 2020, 01:48 PM   #11
wolf_teeth is offline wolf_teeth  United States
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Look up my Triumph design. 9.5" cube with 2 PRs. F3 of 40Hz, and lower room loaded. You can use whatever amp you like.
Wolf
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Old 11th August 2020, 02:23 PM   #12
hv6478 is offline hv6478  Canada
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Originally Posted by wolf_teeth View Post
Look up my Triumph design. 9.5" cube with 2 PRs. F3 of 40Hz, and lower room loaded. You can use whatever amp you like.
Wolf
Hey Wolf, thanks for chiming in, and for sharing your designs and wisdom.

Your Triumph (or Biumph) was one of the first ones I found actually. Really love the design and the "cube-ness" of it. The f3 is what ultimately deterred me -- that at the fact that the Dayton SA25 plate amp does not have an auto-on feature which is a deal breaker for me. Though perhaps with the SA70 or a different outboard power amp that would be a non-issue.

I also noticed the TB driver in your design is not available to me (I have to shop on solen.ca fyi). I wonder if the SMF version would do well in your design. The other tough part is that it's nearly impossible to predict what the in-room extension would be. I definitely "need" it to go to 30-32Hz f3 to satisfy this system and to make this whole project worth doing in my case. I like a variety of music, but especially with certain bass guitar, piano, double bass and other low instrument parts, the low 30s are very important.

That said, I can't help but wonder if the Triumph would dig down deep enough in-room and sound better overall with music, even though it doesn't have as low of a modeled f3.
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Old 11th August 2020, 02:44 PM   #13
hv6478 is offline hv6478  Canada
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Originally Posted by chris661 View Post
Add mass to the PRs to drop the tuning frequency.

Chris
Totally missed this response -- great point and thank you. I will dive a bit deeper into PRs and their mass and do some more research. I've see mixed opinions on PR performance, not sure what to expect as I've never heard one.
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Old 12th August 2020, 08:16 AM   #14
chris661 is offline chris661  United Kingdom
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A good PR system will sound like a good ported box, but with subtle differences:

- So long as you have enough PR cone area, they won't compress at high levels
- A PR box tends to be smaller because you're not trying to fit a 1m+ port in there
- PRs will add a little harmonic distortion as excursion increases, just as the main driver will. That will probably lead to a more even distortion profile.

When I say "distortion", we're talking a couple of percent THD, but it will be level-dependent. I've pushed drivers to >100% THD before now, but it doesn't sound pretty.

Chris
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Old 13th August 2020, 02:53 AM   #15
Brian Steele is online now Brian Steele  Grenada
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Quote:
Originally Posted by chris661 View Post
PRs will add a little harmonic distortion as excursion increases, just as the main driver will. That will probably lead to a more even distortion profile.
I hadn't thought of the distortion again, but yes, seems to be correct based on measurements of my current build. Luckily we're not very sensitive to distortion at low frequencies, particularly when it involves music rather than sine waves.

BTW, that driver seems to have quite a bit of excursion potential. I wonder if a passively-assisted design for it might work? I'm actually about to try just that sort of alignment with two 12" drivers that I have lying about. Lots of decent Xmax and they will be used nearfield, so I will likely not be running them anywhere near max linear output anyway.
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Old 13th August 2020, 04:39 AM   #16
GM is offline GM  United States
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Quote:
Originally Posted by hv6478 View Post
Thanks very much for the greetings and reply!

I imagine you mean a steeper roll off on the low end?

Would something more like 1x4 combat those bends enough?

Perhaps a modest outboard power amp would work if I could figure out a good way to hide it in the setup.
You're welcome!

No, a higher F3, slower roll-off; the bend's cumulative friction adds a resistive component.

A 1.273:1 rectangular ratio is the optimum with up to a [1.273*9]^0.5 = 3.3848:1 not much worse, so 4:1 is fine and one I often used in the 8 - 30 ft^3 towers I use to build, still recommend for Altec, et al low tuned HE vented alignments [aka MLTL in recent decades].

It won't be a 'Voxel' anymore, but this type alignment tends to perform better overall morphed into an inverse tapered TQWT and if needing fine tuning can add a 'stub' vent [ML-TQWT].

Definitely recommend a separate dedicated amp.

GM
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Old 13th August 2020, 06:01 PM   #17
hv6478 is offline hv6478  Canada
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Quote:
Originally Posted by chris661 View Post
A good PR system will sound like a good ported box, but with subtle differences:

- So long as you have enough PR cone area, they won't compress at high levels
- A PR box tends to be smaller because you're not trying to fit a 1m+ port in there
- PRs will add a little harmonic distortion as excursion increases, just as the main driver will. That will probably lead to a more even distortion profile.

When I say "distortion", we're talking a couple of percent THD, but it will be level-dependent. I've pushed drivers to >100% THD before now, but it doesn't sound pretty.

Chris
Great info here and I'm going to consider those options. Maybe start with one due to the cost.

Quote:
Originally Posted by Brian Steele View Post
I hadn't thought of the distortion again, but yes, seems to be correct based on measurements of my current build. Luckily we're not very sensitive to distortion at low frequencies, particularly when it involves music rather than sine waves.

BTW, that driver seems to have quite a bit of excursion potential. I wonder if a passively-assisted design for it might work? I'm actually about to try just that sort of alignment with two 12" drivers that I have lying about. Lots of decent Xmax and they will be used nearfield, so I will likely not be running them anywhere near max linear output anyway.
Seems to be quite a lot of love for PR and other builds have successfully used this driver for them as well, so definitely going to consider this an option. Would shrink the footprint a bit as well. Are you doing dual 12" passives with a single driver in your setup? And is it mostly for music as well?

Quote:
Originally Posted by GM View Post
You're welcome!

No, a higher F3, slower roll-off; the bend's cumulative friction adds a resistive component.

A 1.273:1 rectangular ratio is the optimum with up to a [1.273*9]^0.5 = 3.3848:1 not much worse, so 4:1 is fine and one I often used in the 8 - 30 ft^3 towers I use to build, still recommend for Altec, et al low tuned HE vented alignments [aka MLTL in recent decades].

It won't be a 'Voxel' anymore, but this type alignment tends to perform better overall morphed into an inverse tapered TQWT and if needing fine tuning can add a 'stub' vent [ML-TQWT].

Definitely recommend a separate dedicated amp.

GM
This is awesome, and before some research I didn't understand it all. Makes a whole lot of sense and I'm glad that a 4:1 is an option, if I stay with a slotted design I will go for that ratio at most.

This design and modeling it though, is difficult for me to grasp. Not sure how I would determine the correct angle and length, positioning, need for a port, etc. I can't seem to find that option in WinISD but I apologize in advance for my potential ignorance. A bit of a start on some guidance on this would be awesome and I'm curious!

For the dedicated amp, I'm running into one snag trying to figure out a subsonic / high pass filter for the driver to protect it from xmax especially at the lower frequencies. It seems the DSP-integrated ones all have this feature as standard, but that would take this project a bit beyond its original scope of pricing and also have a LOT of extra power. I know it's good, but it would be extreme amounts of headroom that seems unnecessary for this system. Any insight on this would be greatly appreciated.

Great to see some action in this thread and I really appreciate it. Can't wait to get them (or it) built. Will be posting some new revisions with a 4:1 vent port without an internal amp, as well as maybe a PR version.

Last edited by hv6478; 13th August 2020 at 06:17 PM.
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Old 13th August 2020, 08:46 PM   #18
Brian Steele is online now Brian Steele  Grenada
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Quote:
Originally Posted by hv6478 View Post
Are you doing dual 12" passives with a single driver in your setup? And is it mostly for music as well?
"Passively-assisted" doesn't involve the use of passive radiators. Basically you add a whole bunch of capacitance in series with the driver mounted in a sealed box. Get the amount right, and the result is an extended response (the graph I provided is one such alignment). It also seems to knock down the inductance hump a bit. The graph is a sim of 12" drivers in a 1 cu.ft. (!) box. Basically the speaker baffle for the box will be just slightly bigger than the speaker itself.

It's the first time that I'll be trying it out. But the sims look good. The plan, if it comes to fruition, is to mount each 12" passively-assisted subwoofer on each side of the couch in the living room, for some nearfield subwoofer goodness.
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Old 14th August 2020, 02:46 PM   #19
hv6478 is offline hv6478  Canada
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Quote:
Originally Posted by Brian Steele View Post
"Passively-assisted" doesn't involve the use of passive radiators. Basically you add a whole bunch of capacitance in series with the driver mounted in a sealed box. Get the amount right, and the result is an extended response (the graph I provided is one such alignment). It also seems to knock down the inductance hump a bit. The graph is a sim of 12" drivers in a 1 cu.ft. (!) box. Basically the speaker baffle for the box will be just slightly bigger than the speaker itself.

It's the first time that I'll be trying it out. But the sims look good. The plan, if it comes to fruition, is to mount each 12" passively-assisted subwoofer on each side of the couch in the living room, for some nearfield subwoofer goodness.
Were I a bit more brave I'd love to try this myself but I will patiently await your outcome (if it happens) and maybe use it for a future project. The world of audio/speakers is extremely fascinating.

Have been a bit busier than usual with work (no complaints!) but will get some new drawings out soon. For simplicity and given that this is my first build, I'm leaning towards sticking with a 4:1 ratio slot port and finding the right external amplifier for it. The Monoprice 100W simple one seems like it would fit the bill quite nicely (65 WPC at 4 ohms) though I don't think it has a high pass / subsonic filter built in.
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Old 18th August 2020, 10:14 AM   #20
Booger weldz is offline Booger weldz  United States
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I did this(yellow pic) with that little tangband and it simmed as the red response curve in the bare cabinet using horn response. The blue was what I got from the RTA in REW(with smoothing drawn). I considered redoing it with a smaller throat chamber and without the expansion, but it’s all broken in now and is pretty fun for a 5.25”. Pretty sure you’ll enjoy it. If I see one @ parts express restock or on sale I’ll be jumping for another.

I used a plate amp on it... yuck. Try the 100w t3116 Chip amp?
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