Agreed. Unfortinately, it seems that the most popular QA / QC tolerance used by manufacturers at the moment is 10% to Fs, and quite literally nothing else.
I was doing some commercial work recently and had sample pairs from 'a certain manufacturer' (well regarded) of a number of their units. As it turns out, that's exactly how they production test. None of the units received were impressively close to advertised, but one in particular was so far out, both to tolerance and as a pair-match that I asked for another set to be sent. To their credit, said manufacturer did just that, and even included an impedance sweep showing they were within roughly 3Hz of each other. Unfortunately, it was the only thing that was -poor pair matching, with a difference in Qt between units of about 9% and an average over 40% higher than claimed.
I was doing some commercial work recently and had sample pairs from 'a certain manufacturer' (well regarded) of a number of their units. As it turns out, that's exactly how they production test. None of the units received were impressively close to advertised, but one in particular was so far out, both to tolerance and as a pair-match that I asked for another set to be sent. To their credit, said manufacturer did just that, and even included an impedance sweep showing they were within roughly 3Hz of each other. Unfortunately, it was the only thing that was -poor pair matching, with a difference in Qt between units of about 9% and an average over 40% higher than claimed.
Please excuse my ignorance but I am on this site to learn and to learn one must ask questions. I do not doubt Scott's and Dave's assessment on the 2 boxes I presented but how will these poor designs affect sound? I have read many times that measurements don't always tell the truth.
The "optimal" volume for the 12p in a bookshelve seems to be IIRC, 16-20L. My question is: Can the dimensions be changed as long as the internal volume stays at 16-20L? Will any configurations work? If we take another proven design, the Pensil 12p at 67L internal volume, and change the dimensions while keeping the same volume, what will happen?
I have seen on a commercial site a Mark Audio 12p DIY kit, enclosure dimensions are 50cm X 25cm X 35cm = 32L roughly the same as my 2nd box.
I'm assuming that they ran the same type of tests as Scott and Dave did before commercializing it. Again, I am not questioning Scott or Dave but why does this 32L box work? Is it because the dimensions are different therefore a different alignment? Or maybe it just does not work and they don't care.
This is getting too confusing. I think I'll just go out and buy a commercial speaker and call it a day LOL (just kidding).
Thanks for your help and patience.
The "optimal" volume for the 12p in a bookshelve seems to be IIRC, 16-20L. My question is: Can the dimensions be changed as long as the internal volume stays at 16-20L? Will any configurations work? If we take another proven design, the Pensil 12p at 67L internal volume, and change the dimensions while keeping the same volume, what will happen?
I have seen on a commercial site a Mark Audio 12p DIY kit, enclosure dimensions are 50cm X 25cm X 35cm = 32L roughly the same as my 2nd box.
I'm assuming that they ran the same type of tests as Scott and Dave did before commercializing it. Again, I am not questioning Scott or Dave but why does this 32L box work? Is it because the dimensions are different therefore a different alignment? Or maybe it just does not work and they don't care.
This is getting too confusing. I think I'll just go out and buy a commercial speaker and call it a day LOL (just kidding).
Thanks for your help and patience.
The 'bare bones' answer is they are under-damped alignments as previously noted, which means they are more resonant than optimal, i.e. 'ring' [tail wagging the dog, so to speak], so more internal damping required, rolling off the bass, defeating the purpose for having a lower tuned, bigger cab to get more bass down low.
That said, the room dominates down low, so this type of alignment [aka extended bass shelf [EBS]] can work well when stuck in a corner to boost the low end.
In short, there's a plethora of ifs, ands, and buts in speaker design, so takes awhile to 'get a handle' on it all.
Yes, up to a point and with such small cabs you reach it pretty quick since ideally you need a ~1.5x driver depth surrounding it ['breathing' room] if you don't want the cab to present an obviously irregular acoustic loading.
A typical cab is presumed to have a ~uniform particle density, so driver, vent location can be anywhere they will fit, but when the cab ratio reaches a high enough aspect ratio it begins to form 1/4 WL TL pipe action which impacts both driver and vent location for optimal performance, so like most things in audio, it depends.......
I'll leave the 32 L Q for others to respond.
That said, the room dominates down low, so this type of alignment [aka extended bass shelf [EBS]] can work well when stuck in a corner to boost the low end.
In short, there's a plethora of ifs, ands, and buts in speaker design, so takes awhile to 'get a handle' on it all.
Yes, up to a point and with such small cabs you reach it pretty quick since ideally you need a ~1.5x driver depth surrounding it ['breathing' room] if you don't want the cab to present an obviously irregular acoustic loading.
A typical cab is presumed to have a ~uniform particle density, so driver, vent location can be anywhere they will fit, but when the cab ratio reaches a high enough aspect ratio it begins to form 1/4 WL TL pipe action which impacts both driver and vent location for optimal performance, so like most things in audio, it depends.......
I'll leave the 32 L Q for others to respond.
Again, those bigger ones are no reflex but TL type of speakers that use an other way to get low, that is why they are bigger. If you don't understand how a TL works, that is fine, but they work as is tested many times. But you can't change the dimensions as then the tuning won't work anymore.
For a reflex, the 32L is too big and won't work, they need a smaller cabinet, and this driver won't go that low in a reflex. 20L tuned to 55Hz is what looks for me the best reflex box. Bigger will give a very resonant one note bass. If you want a bigger cabinet, choose an other driver. If you want this driver, use the right cabinet. For the reflex you can change the form a bit, there it's less important. But the internal volume and the port needs to stay the same and if you change the front panel, the diffraction (and baffle step) may be different.
binachi,
What the other members have been trying to tell you is that for a bass-reflex cabinet, the 32L does not yield a good result from modeling. Increasing the size of the cabinet for a reflex cabinet is not likely to give you good results. The members do understand that you want to have a bigger cabinet vs 16-20L, and I think you want that from an aesthetic point of view and also you are assuming that the larger cabinet will give you some additional bass performance. But the bass-reflex modelling does not show much additional low frequency performance without compromising on other aspects. For example you can design a cabinet to make the driver go lower, but the performance in the 100-200 Hz area can then fall a few dB down and give you an uneven frequency response. With a speaker like that you will probably get thin and less lively bass.
On the other hand, the Pensil is not a bass reflex cabinet, rather it is an MLTL variant; and for it to operate properly it will need to be a floor-standing speaker. The math behind a design like that is very different from bass reflex modeling and it is not a apples to apples comparison.
What the other members have been trying to tell you is that for a bass-reflex cabinet, the 32L does not yield a good result from modeling. Increasing the size of the cabinet for a reflex cabinet is not likely to give you good results. The members do understand that you want to have a bigger cabinet vs 16-20L, and I think you want that from an aesthetic point of view and also you are assuming that the larger cabinet will give you some additional bass performance. But the bass-reflex modelling does not show much additional low frequency performance without compromising on other aspects. For example you can design a cabinet to make the driver go lower, but the performance in the 100-200 Hz area can then fall a few dB down and give you an uneven frequency response. With a speaker like that you will probably get thin and less lively bass.
On the other hand, the Pensil is not a bass reflex cabinet, rather it is an MLTL variant; and for it to operate properly it will need to be a floor-standing speaker. The math behind a design like that is very different from bass reflex modeling and it is not a apples to apples comparison.
Hello Zman01,
I have been given some great advise on this forum and I value the wealth of knowledge of the members.
Yes, I am looking for a smaller cabinet but not necessarily for aesthetic reason. My listening area is small and I don't want the speakers taking up a lot of space.
The compact MLTL that was mentioned by Dave sounded interesting but still a little bigger than what I wanted. So, in the end, I will build the Simple Reflex in a nice 18L version that I saw and perhaps later use the 12p to build a Pensil. Options are endless with this driver.
I have been given some great advise on this forum and I value the wealth of knowledge of the members.
Yes, I am looking for a smaller cabinet but not necessarily for aesthetic reason. My listening area is small and I don't want the speakers taking up a lot of space.
The compact MLTL that was mentioned by Dave sounded interesting but still a little bigger than what I wanted. So, in the end, I will build the Simple Reflex in a nice 18L version that I saw and perhaps later use the 12p to build a Pensil. Options are endless with this driver.
bianchi,
Sounds like a plan. However, please note that the "standard" Pensil12P (not the Super Pensil 12P) has a similar footprint to that of a bookshelf speaker, but taller. With bookshelf units you will need some sort of a stand, with a floor-stander, no stand required.
I am assuming that you already have some sort of furniture /stands in place that can support the bookshelf units?
Sounds like a plan. However, please note that the "standard" Pensil12P (not the Super Pensil 12P) has a similar footprint to that of a bookshelf speaker, but taller. With bookshelf units you will need some sort of a stand, with a floor-stander, no stand required.
I am assuming that you already have some sort of furniture /stands in place that can support the bookshelf units?
Hmm, loaded up the 12P specs and [Sd] is way too big at 177.41 cm^2, but all the specs line up with 147.41: Alpair 12P | Markaudio
A basic T/S max flat BR with 0.5 ohms [Rs] = 0.3 Qts': 16.2 L, 56.2 Hz Fb, 2.5" dia. x 5.4" vent [1.75" dia. x 2.28" vent / 6 W]
A Pi Align BR is 14.96 L, 35.35 Hz Fb, 2.5"dia. x 17.48" vent [1.75" dia. x 2.28" vent / 6 W]
The T/S BR is better for vintage R&R or similar deep bass shy recordings, but if needing any output below ~45 Hz, the Pi Align is preferred down to ~30 Hz, also better if stuck in corners.
Ok, what's your max outside [o.d.] W x D x H?
Seated ear height or whatever height you want the driver/floor height to be?
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I think Stefan (UK distributor) does, mostly as a favour to them. Don't quote me on that.
PI Align looks good, otherwise the 17 litre box I did when it originally came out http://www.madisound.com/pdf/SmallReflexA122p-191012.pdf I know works well.
PI Align looks good, otherwise the 17 litre box I did when it originally came out http://www.madisound.com/pdf/SmallReflexA122p-191012.pdf I know works well.
Hello DIYer's,
I finally completed my second build and satisfied with the result.
Here's a brief description:
* Mark Audio Alpair 12.2p drivers
* 19L Baltic Birch rear ported box.
* bracing side to side and back to front.
* 1 inch felt covers the inside wall.
* walnut veneer on front and top, the rest is stained.
* the stands are also DIY and stained black.
I only have about 40 hours in them. They sound OK and I'm hopping that things get better. They are detailed but lack bass, which I expected and I accept it.
I finally completed my second build and satisfied with the result.
Here's a brief description:
* Mark Audio Alpair 12.2p drivers
* 19L Baltic Birch rear ported box.
* bracing side to side and back to front.
* 1 inch felt covers the inside wall.
* walnut veneer on front and top, the rest is stained.
* the stands are also DIY and stained black.
I only have about 40 hours in them. They sound OK and I'm hopping that things get better. They are detailed but lack bass, which I expected and I accept it.
