I bought a pair of Alpair 7 drivers, searching for a good enclosure, now.
Since, the Alpair 7 is the newest driver of the Alpair family, I didn't find any pracitcal recommendations for an enclosure.
There's a modification of the Pensil ML TL by WoddenDesign which is attractive to me, but the port seems to be tuned a bit high (only 19 mm long ?).
Sorry, I don't have any mathcad sheets for calculation.
Other choice could be Needle Deluxe design by oaudio.de
But the line of this TQWT seems to be too long (as many builders say, Needle was tuned to low, gain in bass wasn't effective).
So any recommondations for application (ML TL design would be prefered by me). Maybe anybody has got some practical information about enclosure for Alpair 7, he has already tried out.
Since, the Alpair 7 is the newest driver of the Alpair family, I didn't find any pracitcal recommendations for an enclosure.
There's a modification of the Pensil ML TL by WoddenDesign which is attractive to me, but the port seems to be tuned a bit high (only 19 mm long ?).
Sorry, I don't have any mathcad sheets for calculation.
Other choice could be Needle Deluxe design by oaudio.de
But the line of this TQWT seems to be too long (as many builders say, Needle was tuned to low, gain in bass wasn't effective).
So any recommondations for application (ML TL design would be prefered by me). Maybe anybody has got some practical information about enclosure for Alpair 7, he has already tried out.
The Pencil 7 is not a modification of anything, it's a dedicated design for the Alpair 7. Fp is 64Hz, anechoic F10 ~42Hz. The Pencil alignment is very specific; designed for a very flat impedance & a slightly raised plateau between Fp & 200Hz which, with the lift engineered into the driver's midband & typical room gain, self-corrects for step-loss. That's why I ended up calling that range of boxes damped air couplers, rather than MLTLs, to reflect their design brief / behaviour.
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Thank you Scottmoose. What makes me wonder about the tuning is that the port opening is 15,2 cm x 3,5 cm (53,2 qcm) when converted to circular port this would be 8,23 cm port diameter. Port length in Pensil series is only 19 mm (right ?). With a port length of only 19 mm you get a 8 db peak at 80 Hz falling down very strong in lower bass.
(sorry, I only filled in these data in bassreflex calculator to get a comparison, maybe mathcad ML TL calculation comes to different solutions here)
(sorry, I only filled in these data in bassreflex calculator to get a comparison, maybe mathcad ML TL calculation comes to different solutions here)
Your BR calculator is assuming an empty cavity, with a uniform internal air particle density, no standing waves, and no damping. The exact opposite of the Pencil in other words, where the cabinet dimensions and transmission-line stuffing is critical to how it functions. The Pencil 7 is not a bass reflex enclosure, so trying to model it as such will give completely inaccurate results. As I mentioned, I even decided not to call them MLTLs, because they're such a specific alignment / have a specific design criteria.
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Hi,
Imageshack - chr70istmasbox02text
The Alpair runs very well in that enclosure too, as one may see in the sim's .
(sorry, text in german, pics and sim's and plan will speak for themself).
In the moment I run the Alpair seven in a 5-Liter BR enclosure tuned to 55-56Hz. Nice as a small monitor positiones near the wall, but I feel, a little bit of air would make him "rounder".
The 8L-enclosure isn't ready by now... hope to finish it soon.
Try it, very nice sounding speaker !
in the CHR-70 application thread i shared a 8L BR-enclosure-plan for the CHR70.
Imageshack - chr70istmasbox02text
The Alpair runs very well in that enclosure too, as one may see in the sim's .
(sorry, text in german, pics and sim's and plan will speak for themself).
In the moment I run the Alpair seven in a 5-Liter BR enclosure tuned to 55-56Hz. Nice as a small monitor positiones near the wall, but I feel, a little bit of air would make him "rounder".
The 8L-enclosure isn't ready by now... hope to finish it soon.
Try it, very nice sounding speaker !
Any chance you might have some FR and impedance graphs to share with us ?
(I have searched)
Svein_B.
Thank you for the simulation, Scottmoose.
The sims show the rising plateau in upper bass area, you mentioned.
On the other hand the enclosure design doesn't support the lower bass area.
I wonder if there's enough lower bass hearable.
Maybe, someone already has build the Pensil and can post his practical experience ?
There's another interesting design called "Torretta" by RumoH Zelfbouw Luidsprekers, postet in the CHR-70 application thread.
The CHR-70 doesn't need LCR correction in this design (the enclosure disigner says)
this is the plan: http://www.diyaudio.com/forums/atta...o-chr-70-application-thread-torretta-tqwt.jpg
Torretta is a TQWT design like the needle. A bit smaller (shorter line) than the Needle and the port is on the backside of the cabinet.
It's tuned to 50 Hz and should give fine bass response with CHR-70.
My question: What should be changed on the Torretta design when ALPAIR 7 is used?
(Comparing the Pensil series for CHR-70 and ALPAIR 7, the ALPAIR 7 has a smaller enclosure).
The sims show the rising plateau in upper bass area, you mentioned.
On the other hand the enclosure design doesn't support the lower bass area.
I wonder if there's enough lower bass hearable.
Maybe, someone already has build the Pensil and can post his practical experience ?
There's another interesting design called "Torretta" by RumoH Zelfbouw Luidsprekers, postet in the CHR-70 application thread.
The CHR-70 doesn't need LCR correction in this design (the enclosure disigner says)
this is the plan: http://www.diyaudio.com/forums/atta...o-chr-70-application-thread-torretta-tqwt.jpg
Torretta is a TQWT design like the needle. A bit smaller (shorter line) than the Needle and the port is on the backside of the cabinet.
It's tuned to 50 Hz and should give fine bass response with CHR-70.
My question: What should be changed on the Torretta design when ALPAIR 7 is used?
(Comparing the Pensil series for CHR-70 and ALPAIR 7, the ALPAIR 7 has a smaller enclosure).
45 Hz F10 isn't bad for such a compact enclosure... if you want more you need to use a bigger box.
dave
My 1st look at that leads to the question of how come they say the EL70 will work with the same tuning.
And if you want bass heft, the smaller microTower goes lower (tuned to 42 Hz)
dave
No thanks necessary, it was made some months ago.
Basically what Dave said. Maximum LF extension was not the prioirity with the Pencils; the design-goal with the Pencil 7 was to produce something that is a doddle to make & tune, that is solid to 60Hz with useable output to the high 40s in-room, with reasonable power handling, well-controlled displacement & a TL-style impedance load. This is why I gave up posting graphs: without considering the specific design critera, there is a tendency to compare apples with oranges (& forget to factor other things into the equation, such as room-gain below Fp).
Basically what Dave said. Maximum LF extension was not the prioirity with the Pencils; the design-goal with the Pencil 7 was to produce something that is a doddle to make & tune, that is solid to 60Hz with useable output to the high 40s in-room, with reasonable power handling, well-controlled displacement & a TL-style impedance load. This is why I gave up posting graphs: without considering the specific design critera, there is a tendency to compare apples with oranges (& forget to factor other things into the equation, such as room-gain below Fp).
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Scottmoose, I think that I've understand your aims for designing the Pensil series. I think (in theorie, regarding the sims) you did a professional job and bass enforcement in upper bass area is well done with your tuning.
Other designs (like the Needle) try to push a small speakers tuning down to the limits with the disadvantage of leaving a hole in upper bass area.
Otherwise. the ALPAIR 7 has an extraordinary xmax (4mm) that enables the driver to play even in bass area at higher levels (compared to other speakers).
So my idea is the following:
Instead of using a rectangular port - switching to a round port at the ground of the enclosure. Diameter of port around 6 cm (-> opening at all around 30 qcm). Length of port at first try 10 cm.
Advantage of round port is, I can change it by cutting it, later.
Other designs (like the Needle) try to push a small speakers tuning down to the limits with the disadvantage of leaving a hole in upper bass area.
Otherwise. the ALPAIR 7 has an extraordinary xmax (4mm) that enables the driver to play even in bass area at higher levels (compared to other speakers).
So my idea is the following:
Instead of using a rectangular port - switching to a round port at the ground of the enclosure. Diameter of port around 6 cm (-> opening at all around 30 qcm). Length of port at first try 10 cm.
Advantage of round port is, I can change it by cutting it, later.
How kind of you to say that in theory you think I did a professional job.
Re the above, it'd no longer be a Pencil, & throws all of my design goals & alignment straight out the window, so you're on your own. I did not design the Pencils for maximum extension, so if that is your priority, why not use a box designed for it? Tuning substantially below Fo might look pretty on a basic FR graph, but it tends to have consequences elsewhere -you do understand what these are, correct?
Re the above, it'd no longer be a Pencil, & throws all of my design goals & alignment straight out the window, so you're on your own. I did not design the Pencils for maximum extension, so if that is your priority, why not use a box designed for it? Tuning substantially below Fo might look pretty on a basic FR graph, but it tends to have consequences elsewhere -you do understand what these are, correct?
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First of all, sorry for my remark about "theoretical" professional job.
This wasn't ment to doubt about your practical experience - more I'd like
to get some impressions of someone who had built the Pensil speakers.
As you said, everything's a compromise when implementing such small drivers for fullrange usage. If I had to choose between a deeper tuned enclosure which lacks in upper bass with LCR correction needed and a slightly higher tuned enclosure with a rising plateau between 64 Hz and 200 Hz to compensate baffle step effect I'd go for your Pensil design.
To explain, where I'm coming from. Up to now, I listened to a pair of ML TL speakers with Tangband W3-315 (link: http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf)
These enclosures are tuned to around 50 Hz (but lacking in upper bass, indeed).
On page 7 of the linked pdf-file, the author compares the Needle design to the TABAQ design, which prooves, that Needle design is tuned to low for this driver.
Some days ago, a friend of mine and me compared my TABAQ speakers to a JORDAN JX92 (in 35 Liter bassreflex) and I got a strong impression about difference between both fullrange units. While the TABAQ's (with this nice little Tangband 3'' driver) played amazingly open in middle-hightone area, the JX92 has it's strength in overall performance. Chorus Voices and instruments had more body with JX92.
In the end I couldn't decide which of the both projects I'd prefer.
This leaded me to the ALPAIR 7 which should have the advantages of both speaker projects. Now, I read a lot of enclosure examples for CHR-70, that are much different and I'm asking myself which enclosure design to go for to get best results (compared to our W3-315 SC vs. JX92 listening impressions)
This wasn't ment to doubt about your practical experience - more I'd like
to get some impressions of someone who had built the Pensil speakers.
As you said, everything's a compromise when implementing such small drivers for fullrange usage. If I had to choose between a deeper tuned enclosure which lacks in upper bass with LCR correction needed and a slightly higher tuned enclosure with a rising plateau between 64 Hz and 200 Hz to compensate baffle step effect I'd go for your Pensil design.
To explain, where I'm coming from. Up to now, I listened to a pair of ML TL speakers with Tangband W3-315 (link: http://coolcat.dk/bjoern/TABAQ_TL_for_TB.pdf)
These enclosures are tuned to around 50 Hz (but lacking in upper bass, indeed).
On page 7 of the linked pdf-file, the author compares the Needle design to the TABAQ design, which prooves, that Needle design is tuned to low for this driver.
Some days ago, a friend of mine and me compared my TABAQ speakers to a JORDAN JX92 (in 35 Liter bassreflex) and I got a strong impression about difference between both fullrange units. While the TABAQ's (with this nice little Tangband 3'' driver) played amazingly open in middle-hightone area, the JX92 has it's strength in overall performance. Chorus Voices and instruments had more body with JX92.
In the end I couldn't decide which of the both projects I'd prefer.
This leaded me to the ALPAIR 7 which should have the advantages of both speaker projects. Now, I read a lot of enclosure examples for CHR-70, that are much different and I'm asking myself which enclosure design to go for to get best results (compared to our W3-315 SC vs. JX92 listening impressions)
IMHO the 'damped air coupler' design seems like another term for an aperiodically tuned TL, or or maybe an aperiodic MLTL if, in fact it is mass loaded(or a true, in an electrical sense, TL), and i agree that it is NOT an MLTL, of the convetional variety.
However no offence, but i dont believe its anything new either
Of course it's not new. I never said it was. I'm one of the people that keeps pointing out that in fact there was very little the pioneers of audio back in the 1920s - '40s didn't do. The air coupler name, implying a QW enclosure with a terminus CSA = the pistonic area of the driver dates back to at least the 1950s. This particular variation happens to have a very specific design criteria as partly above, and the Vb alignment to achieve it is of my own devising (that is new, although hardly something to write home about). Voila! a damped air coupler. Describes the function of this specific alignment almost perfectly, so that's what I called it.
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No apology needed, I've got a root-canal playing up so I'm probably a little on the irritable side today.
The A7 is still very new, so there hasn't been much feedback yet. I believe a substantial number also ended up in Japan, which has futher limited the feedback we get in the West. That'll change, but still early days. Would that life were easy & no compromises. I suppose that'd take half the fun away though, right? We all have different solutions to design challenges; few are really better than others, it's just a case of selecting which suits your requirements as far as possible.
It is a little, although I'm not sure there's all that much difference in practice in terms of Fp.
I know that feeling. The Jordan is one of the better drivers around; of course it's rather larger than the little TB & has a far lower Fo, so it should have more LF weight. The little 'uns do tend to be very nice in the upper mids & HF though don't they?
Hmm. It's probably a good compromise, falling between the two as it does, & I can certainly say it's a very nice driver indeed. I really like mine.
How big a box can you handle?
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Of course i have to agree with this.. i would be as fool not to.
What exactly do you mean by the Vb alignment? Vb as in box volume? or as in the Vb/Vas ratio...i say this only as i would think it wouldnt be difficult to obtain a certain Vb/Vas ratio with a constant CSA=Sd tube, unless it was merely stumbled across, or drivers picked which suit a target Sd and Vas perfectly(or near as)... THAT is if i am getting the gist of what you are saying correctly. if not please do correct me, i dont build speakers as a pro so i may be slightly slow on the uptake!
actually hang on ill have a go!!!!!!!!!
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my take on it scott
eg for a woofer qts 0.35, Sd 90cm² Vas 20litres
target Qcb of 0.7:
THus: Qcb/Qts = 2
Vas/Vb would be = about 3
thus 20/3 = 6.66litres
Vb/Sd :
6660cm³/90cm² = 74cm pipe length
342/0.74 = F3 of around 115Hz
Clearly for this type of alignment, either Vas has to be huge, or Vas/Vb much nearer = 1
ie my 'perfect' TS version....(if it is lol)
Qcb/Qts = 1.5 = 0.7/0.46
giving Vas/Vb = 1(ish)
then Vb=Vas and
20000/90 = 222cm
then 342/2.22 = ¼wavelength of 38.5Hz
so ts required are then:
Qts 0.46, Vas 20litres, Sd 90cm², Fs 38Hz
clearly, my example needs tweaking but is this the general gist of your approach Scott?
And if it is not and i have stumbled across something here, then half the royalties are mine...MUAHAHAHAHA
eg for a woofer qts 0.35, Sd 90cm² Vas 20litres
target Qcb of 0.7:
THus: Qcb/Qts = 2
Vas/Vb would be = about 3
thus 20/3 = 6.66litres
Vb/Sd :
6660cm³/90cm² = 74cm pipe length
342/0.74 = F3 of around 115Hz
Clearly for this type of alignment, either Vas has to be huge, or Vas/Vb much nearer = 1
ie my 'perfect' TS version....(if it is lol)
Qcb/Qts = 1.5 = 0.7/0.46
giving Vas/Vb = 1(ish)
then Vb=Vas and
20000/90 = 222cm
then 342/2.22 = ¼wavelength of 38.5Hz
so ts required are then:
Qts 0.46, Vas 20litres, Sd 90cm², Fs 38Hz
clearly, my example needs tweaking but is this the general gist of your approach Scott?
And if it is not and i have stumbled across something here, then half the royalties are mine...MUAHAHAHAHA
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