Ha! That’s some cheesy 80s music 😝 I tripped and fell over trying to breakdance to it, lol
A beat frequency occurs at the difference in frequency of two tones, the repeating beat (louder sound) between 20 and 210Hz would be 190 cycles per second (too fast to hear), nothing like IMD.
You can hear what IMD (or beat frequencies..) sound like in a single loudspeaker using your sine wave mixer.
Lol! Perfect Beat came out after Planet Rock.
It shows up in my "Bring The Beat Back" algorithm by Steady B on Pandora Radio.
@mark100 @BP1Fanatic
Well I respect your thoughts, I have to point out that you are neglecting the details. Taking a driver from 20-200hz is a major task. I use my lowers from 20-200hz but what does that even mean? At what spl level, what was the actual signal content? Playing heavy, low bass, music with a 808 note in the low 30's at high volume, was successful. Not theoretically but judging by my ears. Still doesn't equate to being successful from 20hz-200hz, so this is something that I have yet to achieve. 30hz-200hz check, 20hz-200hz, not yet. If I thought that my one sub passes from 30hz-200hz then when used as intended, in stereo, equating to 4 18"s, passing will turn into.... still passing. I invite you all to experiment. Its as simple as playing a dual tone signal, one at 200hz and one at 20hz, and playing with the volume and/or top frequency. Thats one of the things I did. Once your woofer starts reaching the limits of Xmax don't expect there to not be distortion, thats just silly.
Just as I think taking a single CD down to reach the sub is a bad idea." - If you look at Arts comment you will notice he is specific. His focus in on the 15mm of excursion.
So lets get the ducks lined up
With my 4 18"s, if I limit play back to about 85db rms at one meter. My 18's can cover 20hz to its upper roll off, no problem.
or 8 - 18's for ~91db rms.
This might be shy some, but for another, this might be plenty. More Music and a 30hz roll off, things get more serious
Still, I am being very conservative on excursion because honestly, how bad will distortion be at 4mm on a driver with 14mm xmax? My point is, its a numbers game, theres no need for guessing. Within 2mm excursion, As long as you have high BL and low Le, 20hz to whatever the drivers FHM is, should be fine.
The beauty is that the PPSML takes up no more space than a single woofer cabinet. So if can you fit a large MTM, you can fit a large PPSML MTM in the same space.
Dispersion won't match any more, at XO. If your Horn has directionality at XO it will simply lose it down spectrum, which is not a problem either.... I mean, it all depends on your goals I guess. Also, I have not delve into the topic of slot directivity.
Well I respect your thoughts, I have to point out that you are neglecting the details. Taking a driver from 20-200hz is a major task. I use my lowers from 20-200hz but what does that even mean? At what spl level, what was the actual signal content? Playing heavy, low bass, music with a 808 note in the low 30's at high volume, was successful. Not theoretically but judging by my ears. Still doesn't equate to being successful from 20hz-200hz, so this is something that I have yet to achieve. 30hz-200hz check, 20hz-200hz, not yet. If I thought that my one sub passes from 30hz-200hz then when used as intended, in stereo, equating to 4 18"s, passing will turn into.... still passing. I invite you all to experiment. Its as simple as playing a dual tone signal, one at 200hz and one at 20hz, and playing with the volume and/or top frequency. Thats one of the things I did. Once your woofer starts reaching the limits of Xmax don't expect there to not be distortion, thats just silly.
"I think the idea of a sub going from 20-200Hz is a bad idea for the intermodulation reason Art spoke of above.
Just as I think taking a single CD down to reach the sub is a bad idea." - If you look at Arts comment you will notice he is specific. His focus in on the 15mm of excursion.
So lets get the ducks lined up
What does this tell us? Remove, excursion, remove the non linear behavior. Reaching down to 20hz while maintaining high accuracy is just a matter of removing excursion, nothing less. If once can produce desired true peak levels at 2mm or less... this idea of IMD/THD is already a nulled issue. Thats all I am saying, unless someone as some other metric to talk about.... within a couple of millimeters of movement, the cone is Dominated by BL and Le and the conditions that lead to THD/IMD are not there. Now its just a matter of headroom, as in, yeah we can cover the whole spectrum if the drivers frequency response, as long as its done so within 2mm of excursion.
With my 4 18"s, if I limit play back to about 85db rms at one meter. My 18's can cover 20hz to its upper roll off, no problem.
or 8 - 18's for ~91db rms.
This might be shy some, but for another, this might be plenty. More Music and a 30hz roll off, things get more serious
Still, I am being very conservative on excursion because honestly, how bad will distortion be at 4mm on a driver with 14mm xmax? My point is, its a numbers game, theres no need for guessing. Within 2mm excursion, As long as you have high BL and low Le, 20hz to whatever the drivers FHM is, should be fine.
Problems where?
The beauty is that the PPSML takes up no more space than a single woofer cabinet. So if can you fit a large MTM, you can fit a large PPSML MTM in the same space.
Dispersion won't match any more, at XO. If your Horn has directionality at XO it will simply lose it down spectrum, which is not a problem either.... I mean, it all depends on your goals I guess. Also, I have not delve into the topic of slot directivity.
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Are those pm90's on steroids ??
See post #180
https://soundforums.net/community/threads/new-diy-mid-high-90deg-aka-pm90.11601/page-9
See post #180
https://soundforums.net/community/threads/new-diy-mid-high-90deg-aka-pm90.11601/page-9
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For me, the difficulty is getting to f-3 @ 20Hz, because I want whatever f-3 the design goal is to be achieved without boost.
So the f-3 corner becomes relative to flat response all the way up to the subs low-pass.
20Hz ...getting that low, is the problem.
25Hz to 200Hz is no problem. That is a 3 octave span, which is generally doable for any driver section until pushed past linearity.
Doesn't everyone use there ears to make final judgements with? Through all the thick and thin ways playing music?
For me, listening rules; measurements help me build & tune the box. I loose patience with theory; try to leave that to armchair DIY.
Keeping a speaker's SPL easily within it's range of linearity works.
I try to maintain linearity for as high a SPL as possible, including having about +18dB headroom for transient peaks.
And maintain that linearity across the entire spectrum, from f-3 low corner up.
This high SPL linearity goal is a big factor in the increased multi-way count I use.
I can only comment on regular slot loaded designs as I know them....like the PPSL I posted years back and used up until my new V twin.
I do not know exactly what you are doing, and can't muster the curiosity to look into it. Because I'm convinced there are only 3 types of subs I want to devote time/interest in....sealed, reflex, and FLH (which I view as sealed with a horn attached). Can't see the need for others.
Slot loaded is simply an opposed driver arrangement for use with any of those 3 types....and again, a pain in the butt, but a blessing for vibration reduction when cranking (part of the max linear SPL equation).
What I don't like about your Acoustic Power sim above, is the degree of low end roll-off.
Appox 89dB at 25 Hz doesn't look that good to me, as I know it will limit linear SPL as I turn it up.
Upper end response looks fine.
Hey, maybe you should use the box with another sub? 😉 I had to do that with syn11..
Not sure what you're pointing out..???
The PM90 and PM60 are super boxes. Peter Morris gave the community a fantastic design. Hi-fi PA.!! 😀
They are what started me seriously into DIY multi-ways, almost 10 years ago..
I'd go to soundforums and ask for the latest plans. https://soundforums.net/community/forums/diy-audio.28/
Mine were built right at the beginning, from the first set of plans put together.
I've been out of touch since then, because my hope to get involved in live-sound didn't pan out. So I don't know how, or if, the plans have evolved.
I imagine they have, maybe to accommodate the B&C DCX464, which is a bit larger than the bms CD the box was originally designed around.
Very helpful folks over there....🙂
GREAT speakers!
Mine were built right at the beginning, from the first set of plans put together.
I've been out of touch since then, because my hope to get involved in live-sound didn't pan out. So I don't know how, or if, the plans have evolved.
I imagine they have, maybe to accommodate the B&C DCX464, which is a bit larger than the bms CD the box was originally designed around.
Very helpful folks over there....🙂
GREAT speakers!
I take it this Hmmm refers to me not wanting to use any low-end boost to be flat down to f-3 ??
Very true and for good reason.
For the purpose of obtaining max linear SPL though the full spectrum, whatever dB boost is applied effectively reduces max linear SPL by that amount.
The gedlee post you quoted from was talking about the high-end.
The first sentence opens with being clear about an acoustic low-pass.
You appear to be mixing up which end of the barrel you're referring to.......can get a fellow hurt shooting like that. lol.
I agree with his post. I see little need for acoustic low-passes given DSP.
Out of band resonances are easily handled by IIR PEQ's or steep complementary linear-phase xovers, or a combo or both.
Plus the value of a slot's 'acoustic low pass' is nil ime.
It's not really a low-pass, it's more like a big notch, with response rising again past the notch.
Did I say slots are a pain ?? for a particular vibration-reducing worthwhile gain 🙂
Thank you but I don't have user for that forum, do you mind to download and post those PDF plans here?
He definitely meant that literally as it was written, with regards to, passive anything. He did not encourage bass reflex/TL nor resonant waveguides known has horns. In regards to the slot he said it would just complicate things, and even though we did not talk much about the slots directivity, he wasn't wrong. Hornresp doesn't even attempt to figure directivity of the offset horn of the shortest variety that is PPSL and what I see in the ripple tank has me wondering whats really going on.... anyone know how to make sense of the frequency spec on the ripple tank simulator?
Regarding the slot, the proposed PPMSL version removes the low pass or at least most of it. With some development I see the potential to fix potential vertical off axis issues.
You are interested in increasing headroom, and so am I. @weltersys How come you are schooling me on PPSL directivity, I know you know and do you know how to decipher the ripple tank simulator?
I tried to use a slot once - for dual 12", inspired by ripoles. It had a nasty resonance above 200 Hz, that I had to tune down. No slots for me since then unless they are small enough - have you seen XRK's SLOB with multiple woofers? The slots are small (depth, height) and at the same time wide enough to play relatively high (crossover around 400 Hz IIRC).
Hi LORDSANSUI, registration is free using real name
(which I find refreshing and wish I used on all audio forums ..I'm Mark Wilkinson that pops up in the start of the DIY90 thread.
It will take some searching through the thread to find latest plans, or earlier ones, depending on what drivers you want to use, and what weight goal you have in mind...my guess is there are several versions by now. I really think it would be best to register, and ask the guys for some direction. Good luck !