I have noticed that tapered TL’s (similar to PMC ATL) seem to provide a very dynamic, clear and articulate bass while at the same time improving midrange clarity. Examples of this with my own builds also seems to show that minimal stuffing is typically used and tuning the amount of stuffing by looking at the measured double peak impedance sweep such that the two peaks are relatively squashed into what resembles a horned “owl’s head” (a bump with two small peaks) seems to give the best optimization in response. Too much stuffing or stuffing in the wrong place kills the bass and not enough and it is boomy. But at least this is measurable and and a quantifiable diagnostic is available. I learned this through a combination of simulation of varying the stuffing using Akabak and real listening tests and mic measurements. These are examples of my builds using this type of TL’s:
10F/8424 & RS225-8 FAST / WAW Ref Monitor
Simple Passive Harsch XO Using PTT6.5 and RS28F in a Waveguide
Low-Cost PMC-inspired TL Monitor with DC130A and DC28F
TLs are extremly difficult to make right and ask time with iterative try and error... and the bump...the bass bump 🙂.
So datas are even more difficult with TL.
So datas are even more difficult with TL.
Last edited:
Hence the need to simulate accurately before building. Then building a pathfinder in foam core or XPS foam. Then if all measures well and sounds good, proceed with BB plywood build. Then fine tune with measurements of impedance and listening tests.
This was the path taken on both the RS225 and PTT6.5 TLs. They can’t be built effectively with trial and error alone. A good simulation is critical.
This was the path taken on both the RS225 and PTT6.5 TLs. They can’t be built effectively with trial and error alone. A good simulation is critical.
There is a simple experiment to try: put a midrange driver onto a box ( wathever the shape) then stuff the box as much as you can.
Listen to white noise through it and through headphone*. Is there a difference? Play a song do you spot a difference too? Repeat taking some of the stuffing out progressively.
I found this to be interesting.
*reproducing the box behavior through filters.
I've had an answer from Scottmose about stuffing and driver interactions but can't find it atm. I found it very interesting, will try to find it and repost the link.
wesayso wrote:
When striving for the highest level of performance, we often incorporate many features which might result in better sound. I certainly do that. Yours was a truly epic, heroic build by the way...
When striving for the highest level of performance, we often incorporate many features which might result in better sound. I certainly do that. Yours was a truly epic, heroic build by the way...
^ you want me to spoil the fun?!
Ok, i found a point at which there is an equilibrium.
Too much stuffing and transient suffers. Too low there is too much resonance.
Both white noise and a track are interesting in spoting things as you'll hear different conditions ( steady/transient modes).
Tbh i was looking for 'no box sound': my own conclusions are that stuffing alone won't bring that, shape have to be taken into account too imho.
Ok, i found a point at which there is an equilibrium.
Too much stuffing and transient suffers. Too low there is too much resonance.
Both white noise and a track are interesting in spoting things as you'll hear different conditions ( steady/transient modes).
Tbh i was looking for 'no box sound': my own conclusions are that stuffing alone won't bring that, shape have to be taken into account too imho.
... breaking the main modes by deleting them into multiple littlier modes.
So how to'predict ? Are there formulas to beginn with with the length, width, heigth of the load to know the main frequencies to break or is it about to measure like Stereophile the internal box with a piezo stuff to capture the vibration ?
So how to'predict ? Are there formulas to beginn with with the length, width, heigth of the load to know the main frequencies to break or is it about to measure like Stereophile the internal box with a piezo stuff to capture the vibration ?
Transient (oscillation) - Wikipedia
Transient (acoustics - Wikipedia)
If you want a value lets say first milliseconds of a sound ( where the information about the familly of instruments are, so it vary with the kind of instrument but let's say between 2/5ms as average).
Transient (acoustics - Wikipedia)
If you want a value lets say first milliseconds of a sound ( where the information about the familly of instruments are, so it vary with the kind of instrument but let's say between 2/5ms as average).
Last edited:
OK, so we agree on that. Now throw a bandpass filter into the equation. Think of transient again. What defines the way a transient is reproduced?
Depend the kind of filter you use, the design choice you made for the whole loudspeaker layout choice...
To be short i use for almost ten years now a Dolby Lake and most of the time with FIR.
The test i made were with a MA Alpair 7 ( which is a fullrange in a closed box of aprox 8l for qtc 0.707) then with my main's mid which is here again a closedbox design with a 4" too and is overstuffed standard (Technics SB-M2).
Being a Technics design from early 80's/90's it feature the legacy of their 'linear phase' philosophy ( the flat membrane drivers are aligned verticaly for the mid and tweet, i discovered the woofer was not from some mm when i swtiched them to multi amp active). So is it capable to reproduce a squarewave? Tbh i just don't care and don't think it is relevant here.
So are the transient mangled by a (or multiple) filter(s)? Yes most of the time.
Does it make the effect on stuffing we talk about not audible? No from what i heard with either a fullrange or my multiway.
Try it. It is easy to reproduce (if you want more details about what i did exactly i think i could find them as i usually keep records of experiments i make) and to listen by yourself and conclude if it is placebo effect from my side or something you can hear.
To be short i use for almost ten years now a Dolby Lake and most of the time with FIR.
The test i made were with a MA Alpair 7 ( which is a fullrange in a closed box of aprox 8l for qtc 0.707) then with my main's mid which is here again a closedbox design with a 4" too and is overstuffed standard (Technics SB-M2).
Being a Technics design from early 80's/90's it feature the legacy of their 'linear phase' philosophy ( the flat membrane drivers are aligned verticaly for the mid and tweet, i discovered the woofer was not from some mm when i swtiched them to multi amp active). So is it capable to reproduce a squarewave? Tbh i just don't care and don't think it is relevant here.
So are the transient mangled by a (or multiple) filter(s)? Yes most of the time.
Does it make the effect on stuffing we talk about not audible? No from what i heard with either a fullrange or my multiway.
Try it. It is easy to reproduce (if you want more details about what i did exactly i think i could find them as i usually keep records of experiments i make) and to listen by yourself and conclude if it is placebo effect from my side or something you can hear.
Last edited:
Well, my hypothesis is that you hear 'ringing' from resonances in the enclosure and that you actually enjoy them as representants of transients. People like studio effects doing this, people like the harmonics distortion of tube amps and people like the distortion of playing vinyl records. So I don't think it is a placebo.
Edit: nothing sounds as boring as a Dirac pulse.
Edit: nothing sounds as boring as a Dirac pulse.
Last edited:
Well maybe but to tell you the truth i'm a former studio engineer and i'm used to listen to live instruments played in front of me as well as through differents monitors.
I think i can identify ringing when i meet them ( i tracked a lot of metal and rock and had the reputation from my clients to be obsessed by the resonance a guitar cabinet produce... to the point to be an annoyance to them in some case).
But well maybe you are right and i trust to much my own capacity ( i'm not to the point to think i have 'golden ears' but i'm well into the 'trained' listener category. Maybe i'm a bit arrogant about this though. )
That said i'm sure i can identify a smeared transient on percussive instrument or a frequency enhanced or subdued in white noise ( even more when i have a reference through headphone).
Diyiggy:
Your mention of plastic bubble sheet and the experiment i've done yesterday made me think about another material i mentioned that could be used to greater effect around the same idea you have: neoprene.
I put my wetsuit off my closet and been astounded by how much the neoprene used was efficient at absorbtion ( relative to bubble plastic sheet).
Could be interesting to test it too ( it is more resilient than plastic bubble too): it exist in different thickness from 1mm to 5mm or more. Should be cheap too.
I think i can identify ringing when i meet them ( i tracked a lot of metal and rock and had the reputation from my clients to be obsessed by the resonance a guitar cabinet produce... to the point to be an annoyance to them in some case).
But well maybe you are right and i trust to much my own capacity ( i'm not to the point to think i have 'golden ears' but i'm well into the 'trained' listener category. Maybe i'm a bit arrogant about this though. )
That said i'm sure i can identify a smeared transient on percussive instrument or a frequency enhanced or subdued in white noise ( even more when i have a reference through headphone).
Diyiggy:
Your mention of plastic bubble sheet and the experiment i've done yesterday made me think about another material i mentioned that could be used to greater effect around the same idea you have: neoprene.
I put my wetsuit off my closet and been astounded by how much the neoprene used was efficient at absorbtion ( relative to bubble plastic sheet).
Could be interesting to test it too ( it is more resilient than plastic bubble too): it exist in different thickness from 1mm to 5mm or more. Should be cheap too.
Last edited:
Thanks,
I followed the bubbles plastic sheets cause it is free and finish its life in garbadges. Some said at diyaudio that it is forgiving as a damper, i.e. doesn't kill the sound...maybe the iregular shape, maybe the air inside the plastic as a mass spring mass...?
Also one think I thinked about Jim's question, doesnthe irregular shape of the mide enclosure helps also as a better brace than regular cubes for the bass driver if in a same enclosure ?
As I diy for the pleasure morenthan the result I will show later with picture what I plan as a mid enclosure with pictures as xrk971 did... maybe it will feed the thread a little waiting for something more on the topic, i.e datas, i.e. rules to reproduce the same behavior one plans.
I followed the bubbles plastic sheets cause it is free and finish its life in garbadges. Some said at diyaudio that it is forgiving as a damper, i.e. doesn't kill the sound...maybe the iregular shape, maybe the air inside the plastic as a mass spring mass...?
Also one think I thinked about Jim's question, doesnthe irregular shape of the mide enclosure helps also as a better brace than regular cubes for the bass driver if in a same enclosure ?
As I diy for the pleasure morenthan the result I will show later with picture what I plan as a mid enclosure with pictures as xrk971 did... maybe it will feed the thread a little waiting for something more on the topic, i.e datas, i.e. rules to reproduce the same behavior one plans.
@krivium
Well, there's a truth in that too much stuffing isn't right either, like you said. I do however not plead for using one's ears to find the 'equilibrium'. CSD and BD plots are far easier and far more reliable. Close range plots can easily have noise floors down 45-50dB. That gives you an impressive tool to find resonances. Not that I think every resonance is audible, but avoiding/reducing them seems the right path to me.
Well, there's a truth in that too much stuffing isn't right either, like you said. I do however not plead for using one's ears to find the 'equilibrium'. CSD and BD plots are far easier and far more reliable. Close range plots can easily have noise floors down 45-50dB. That gives you an impressive tool to find resonances. Not that I think every resonance is audible, but avoiding/reducing them seems the right path to me.
Perhaps yes, but there is no certainty that an irregular shape will have more stiffness than a box shape. It depends on how tightly the panels and internal bracing fit together. I think it is obvious that making a truncated pyramid shape, or an odd-polyhedron, with tight fitting joints and tight fitting braces is much more challenging than with a box shape.
So Mark - you have had good results by doing near field CSD? I have never tried it but I am intrigued...
It should be sealed... But stifness does not matter inside the main cabinet for the mid box ?
Look at the Arbeth 40.x model...the mid has a truncated box load to free some space for the bass ports...the top of this mid box is screwed with a plastic seal....very stuffed inside as often.
I thought about a load as an air balloon but given up because of the pistonic feedback behavior...
Look at the Arbeth 40.x model...the mid has a truncated box load to free some space for the bass ports...the top of this mid box is screwed with a plastic seal....very stuffed inside as often.
I thought about a load as an air balloon but given up because of the pistonic feedback behavior...
Only old files on device I’m at now, but this BD plot (made with a cheap Yamaha 48k audio interface) near field to a ZA14 clearly shows quite successful damping of a mid enclosure by means of acoustic foam. The enclosure was triangular, with only two parallel boundaries, which caused a resonance at about 1,7kHz. The level was way down and adequately damped, but measurable all the same. Like the cone resonance at 9k and a few other anomalies high up the frequency range.
