Got bored waiting for glue to dry today so turned my attention elsewhere; playing around with acoustic foam for the mid enclosure. I'm not really that sure that the tapered sections in the foam would offer any more effectiveness over not having them at all and maybe the Deflex panels will make the foam unnecessary anyway. Guess the only way I'll find out is just through listening, I can always pull the foam out quite easily if its effect is doing more harm than good.
Things are now being held up by waiting on the Deflex panels, without those I can't start sealing the enclosures up and adding the 9mm MDF outer layers.
RAAL tweeters will be here on Monday and I've been working to get one of the cabinets ready for listening/measuring just to make sure I'm headed in the right direction.
After more discussions with Per he's told me how he would do it: take an 8" C-Quenze, change the suspension compliance to suit a sealed enclosure(35ltr, Qtc=0.6)and go with the kapton former for more detail in the sound or Alu/Kapton if you plan to EQ the low end. Sensitivity of the driver will be around 91dB dropping as you go below 130hz.
I think originally I was looking for something different just for the sake of it and Per assured me that this was what he thought was best for my requests.
I asking about having one of the bigger magnets stuck on the back for extra BL and greater sensitivity. Unfortunately as BL goes up, Qes comes down and so does Qts. You can try to compensate by making the suspension stiffer(raising Qms) but you can quickly compromise the TS balance going that way apparently.
I've been a little naive about the amount of bass these will put out - its going to be disappointing considering the size of the speakers. I guess I figured Per could work miracles with the TS and build something for thats better than whats already on the market, sadly physics stands in our way
Looking at it now with a better perspective and understanding I sort of wish I'd made the cabinets with a pair of XLS10 or XXLS10 in mind now and gone with U frame dipoles with a dedicate sub covering the stuff below 40-50hz. I still haven't heard all this working yet and I may be pleasantly surprised but like Vik said earlier, a v2.0 maybe on the cards. I think its good to do something like that as you get to go back and correct all the short comings you missed the first time around but until you listen and measure then its difficult to assess the situation which is why I'm eager to get these going before I put too much work into them - don't fancy flogging a potential dead horse.
So I'm in the process of ordering a couple of the 8" C-Quenze Per has come up with and getting one of the speakers up and running as quickly as possible. From there I'll be able to see where I should be going.
Things are now being held up by waiting on the Deflex panels, without those I can't start sealing the enclosures up and adding the 9mm MDF outer layers.
RAAL tweeters will be here on Monday and I've been working to get one of the cabinets ready for listening/measuring just to make sure I'm headed in the right direction.
After more discussions with Per he's told me how he would do it: take an 8" C-Quenze, change the suspension compliance to suit a sealed enclosure(35ltr, Qtc=0.6)and go with the kapton former for more detail in the sound or Alu/Kapton if you plan to EQ the low end. Sensitivity of the driver will be around 91dB dropping as you go below 130hz.
I think originally I was looking for something different just for the sake of it and Per assured me that this was what he thought was best for my requests.
I asking about having one of the bigger magnets stuck on the back for extra BL and greater sensitivity. Unfortunately as BL goes up, Qes comes down and so does Qts. You can try to compensate by making the suspension stiffer(raising Qms) but you can quickly compromise the TS balance going that way apparently.
I've been a little naive about the amount of bass these will put out - its going to be disappointing considering the size of the speakers. I guess I figured Per could work miracles with the TS and build something for thats better than whats already on the market, sadly physics stands in our way
Looking at it now with a better perspective and understanding I sort of wish I'd made the cabinets with a pair of XLS10 or XXLS10 in mind now and gone with U frame dipoles with a dedicate sub covering the stuff below 40-50hz. I still haven't heard all this working yet and I may be pleasantly surprised but like Vik said earlier, a v2.0 maybe on the cards. I think its good to do something like that as you get to go back and correct all the short comings you missed the first time around but until you listen and measure then its difficult to assess the situation which is why I'm eager to get these going before I put too much work into them - don't fancy flogging a potential dead horse.
So I'm in the process of ordering a couple of the 8" C-Quenze Per has come up with and getting one of the speakers up and running as quickly as possible. From there I'll be able to see where I should be going.
I would not worry in your case. If its gonna reach 37 -3dB in room, its gonna be fast, strong and accurate sealed box premium bass. Its better to have a controlled LF non extra bulky speaker and and you can always augment it with an active monster sub with DSP so to even out room modes for the 10% of music that has pressure down below 35 only if you have the big room to really reproduce it. If you dont have over 50 SQM the 25-35 territory is looking for trouble IMHO.
I use double 6X9 woofs in my latest speaker (sealed) and I am very happy with the quality over quantity gain that affects the midrange positively too. No boom. Imagine that the Watt & Puppy system 7 does only 50! Its the SPL and quality over quantity.
I use double 6X9 woofs in my latest speaker (sealed) and I am very happy with the quality over quantity gain that affects the midrange positively too. No boom. Imagine that the Watt & Puppy system 7 does only 50! Its the SPL and quality over quantity.
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pinkmouse said:
That's not good then, I hadn't expected miracles but bitumen pads have... well, lets say they're maginally effective at best. During the a "knuckle knock on MDF" test I had to use 4x 2mm layers on the Perceives before I could tell a worthwhile damping effect was taking place.
I never believed the diffusion claims either. Mathmatics would state that the pit depth in the diffusor would only really be effective with an open back tweeter
Where I thought they might be effective was their lossy elastic nature, I hoped that might work positively for mid frequencies at least.
Well I've paid for them now and it can't hurt to try, shame that they don't do much else over bitumen.
I still think that the best way to cut down on resonances is just to ensure good bracing and construction.
salas said:
Nice work on those Salas, very tidy looking.
You've got a good point with the bass issue. I was mindful of that when designing them but I'd expect even with room gain these will need a sub to really satisfy on HT. They should do OK with music though. I do have EQ but it doesn't touch the decay issues smaller rooms have and only flattens the FR.
Dipole bass might be the best solution for a small room. On one hand you've got many of the room nodes being excited evenly giving more even qualities and on the other you only have a smallish volume to pressurise so they don't have to work too hard and maybe you get a few hz more.
I was reading an interesting article about how systems with a Q of 1 offer the most accurate bass that tracks the orignal waveform well. Unfortunately this was when the room was completely removed. It concluded that no alignment was perfect once a room was introduced and that its best to tailor for what you have and not try to come up with something that works universally because that doesn't exist. Can't remember where I read the article but it was interesting to say the least, I think it was from John K (of Nao fame not Zaph).
EDIT: What drivers are those that you used Salas? I can see a PHL mid and what looks to be Tangband 6x9's but the tweeter I'm not familiar with. I'm temped to say its a Vifa or maybe Peerless but thats just a guess.
salas said:
..neither the watt nor the puppy are sealed systems.
I keep going back to that Troels HES II article..
The article never mentions the rather poor group delay of the non-aligned venting - nor I suspect would anyone notice it as such (at least in a high eff. design), as perhaps gleaned from his subjective comments.
with a subjective response like this on higher eff. drivers in a ported cabinet:
"The bass is fast and transient and maybe lacking in some upper bass/lower midrange warmth."
and the trade-offs with a higher eff. driver:
"The Fs really went up from this foam surround. I had hoped for some 40 Hz, but 47 Hz is a bit on the high side. From the Supravox drivers I learned not to worry too much about the Fs as these drivers have an Fs around 65 Hz! Yet, they provide excellent bass from 80 litre cabinets."
of course 35 liters is no 80 liters
Still, I suspect Shin's AT drivers will be very good, but perhaps not quite as "dynamic" as they might otherwise be (..and hopefully that suspicion will be proven wrong).
''EDIT: What drivers are those that you used Salas? I can see a PHL mid and what looks to be Tangband 6x9's but the tweeter I'm not familiar with. I'm temped to say its a Vifa or maybe Peerless but thats just a guess.''
Tangbands till 200Hz just with a coil (they trail off mechanically a lot), PHL 1220 (1 pole & 2pole filter), Audax A20 (3 pole filter) Telar pole piece ND magnet, but with a 4 Ohm diaphragm from another model because the speaker is 94dB / 6 Ohm.
Tangbands till 200Hz just with a coil (they trail off mechanically a lot), PHL 1220 (1 pole & 2pole filter), Audax A20 (3 pole filter) Telar pole piece ND magnet, but with a 4 Ohm diaphragm from another model because the speaker is 94dB / 6 Ohm.
salas said:
True - both the puppy and watt are not aligned (..effectively what I've advocated for smaller cabinet designs).
I feel that your -3db point with room gain is optimistic at best, unless the partnering amplifier reacts to a rising impeadance, i.e. has a high output impeadance, or the loudspeaker is eq'ed (or you are getting some modal gain). Barring baffle step loss, while considering room gain and room construction in the UK (..and not modal issues) - the design should be flat to about 90 Hz.
Lets see then.. 2nd order butterworth with an effective cross point at 100 Hz basically means the system will be down -12db at 50 Hz. At BEST you will only have a gain of about +6 db at 50 Hz in such a home without considering modal gain - that still leaves -6db at 50 Hz. Its MUCH lower in sp-level as freq.s decrease and you would be lucky to achieve +9db to offset the -24 db at 20 Hz, leaving a net value of -15 db.
Also, because the driver spacing is so far apart - the system will not have a great deal of boundry reinforcement.
Additionally, beyond the subjective sense of higher eff. drivers (in ported or sealed systems), none of this broaches the subject of increased distortion due to increased excursion levels from the sealed system. To "compound" this there is the issue of baffle step loss which will almost certainly require additional eq, which again will increase distortion to some extent (..though I suspect a minor amount in the UK).
Its all "give and take", but a partnering sub should work rather well with this design and truly make it a full-range design while preserving the better qualities that this system might afford.
Really nice technical exsplanation, thanks
Exsperience and pure logic tells that an 8"/90db driver will never be a subdriver, it would be a revolution we wouldnt miss - but personally I also enjoy the music without subs
Some has claimed that its very important to get the bass rolloff match the midrange folloff - very light EQ could take care of that
Often when we dont perceive the lower bass, its related to phase issues - very low bass, if its phase coherent with the top, is very clearly heard, even if its rolled off and low in SPL - well, thats logical, isnt it
Exsperience and pure logic tells that an 8"/90db driver will never be a subdriver, it would be a revolution we wouldnt miss - but personally I also enjoy the music without subs
Some has claimed that its very important to get the bass rolloff match the midrange folloff - very light EQ could take care of that
Often when we dont perceive the lower bass, its related to phase issues - very low bass, if its phase coherent with the top, is very clearly heard, even if its rolled off and low in SPL - well, thats logical, isnt it
See what happened in my case. One speaker graphs, stereo pair couples further under 50Hz.
First graph is anechoic prediction, and small room gain without nodes prediction. 2 x 8inch equivalent 6x9 in 26litres sealed common volume.
Second graph is what I measured (single speaker 1.3m tweeter axis).
First graph is anechoic prediction, and small room gain without nodes prediction. 2 x 8inch equivalent 6x9 in 26litres sealed common volume.
Second graph is what I measured (single speaker 1.3m tweeter axis).
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ScottG said:
I was always impressed with the bass on the Perceives. Another sealed alignment that worked well within its range but output was limited. I think twin 8" will offer a little more but I know they aren't going to fully satisfy on some material. As much as I hate to say but to do that I need to start looking at larger drivers and I doubt you'll see my use a driver over 10" as wide baffles just look wrong to me. I have to sit in front of the speakers for many hours, its important to me that they look as good as they sound... audio suicide? No, just my preference.
I don't really discuss firm implementation details because I think it takes away from the build, a good reason why I title my threads "construction diary"
If I was publishing a design that I'd hope others might build then I'd take a different tact. I also design with an eye to allowing for experimentation and modularity where possible - the removable baffles for driver swapouts, seperated sections for mid and tweeter etc, powerful and flexible XO's/EQ. This way I'm better prepared to try out different things. When I hit a problem I can't solve then I start to open up and ask questions(as I did with the Perceive bass/mid integration issue) but I do see there's mounting confusion here and guesswork here so I'll elaborate a little on one option:I think it was others throwing the cutoff figures around, when I went to Per I asked for an F3 of 60hz and he thinks these will have an F10 at 30hz. I know from experience that my room has a bump between 30 and 40hz so this will likely be better. That's my reason for not porting - an 8" will almost certainly be tuned in that 30-40hz range. Most ported designs don't work well in my room, the B&C sub did because it was tuned to 19hz and didn't have to sit where the loudspeakers normally do.
There was always going to be compromise with using smallish 8" drivers to cover the bottom end and like I mention above, I also wasn't willing to stick a 50cm baffle in there and not have to worry about BSC being taken care of by the mids because it would have been shifted down to the the bass. So my ~25cm wide baffle means the BSC will be done on the 5" AT's at around 600-700hz. If I'm smart about this I'll be using that second 5" AT driver only upto 700hz thus not only cutting down on MTM lobing issues which someone was worried about earlier on but also at the same time cutting distortion caused by BSC because two 5" AT drivers will cover the 200hz-700hz range.
I mentioned I design with an eye toward changing things as the project moves on, well here's an example; I've had to change the tweeter mounting to a non recessed setup and at the same time also taken the liberty of physically time aligning the drivers on the tweeter axis at a distance of 2.8m.
tinitus said:
Thanks for the praise!
salas said:
To the model:
First - the room gain is off (+8db) at 50 Hz? Without a gain mode it will only do that in very small reflective spaces, and the lower freq.s will suffer.
Second - of course the model depends on system compliance (..more so nearing in-box resonance).
To the measurement:
First - note that the drivers are not separated, and that they are coupled fairly close to the floor.
Second - What kind of amplification are you using? How low in freq. do the PHL mids go (whats the crossover freq. and slope)? Where are the modes for your room located? The response at 20 Hz looks fairly correct, but everything else looks a little "hinky" without factoring in some of these issues. And note that some of these issues may be very different for Shin.
Third - nice!
salas said:
There's a history of modelled discrepancies. It just the complicated nature of bass within a room.
The most spectacular that I've seen is the XLS10 in an 18ltr sealed enclosure. Modelled it looks aweful, in room I've seen it flat down to 16hz in some cases and most often in the low 20's.
There's NO EQ applied to this response:
An externally hosted image should be here but it was not working when we last tested it.
I trust modelled bass predictions less than I do with the stuff over 200hz which are much more accurate.
Nice pictures, Shin - something that nice will sound good, I am sure
Some time ago, we laughed at a designer who proudly claimed that he could hear 20hz from a small speaker, when sitting under a table....ups, sorry Salas I was not thinking of you
Funny, sometimes when sitting at the computer, I hear very deep well defined tones coming from the other end of room opposite the speakers, but sitting in listening position, nothing of that
Shin, I think your measurement only show a ressonance below 20hz, nothing else and certainly not the woofer playing music
Some time ago, we laughed at a designer who proudly claimed that he could hear 20hz from a small speaker, when sitting under a table....ups, sorry Salas I was not thinking of you
Funny, sometimes when sitting at the computer, I hear very deep well defined tones coming from the other end of room opposite the speakers, but sitting in listening position, nothing of that
Shin, I think your measurement only show a ressonance below 20hz, nothing else and certainly not the woofer playing music
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