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T line \ bass reflex enclosure suggestions
T line \ bass reflex enclosure suggestions
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Old 18th July 2019, 05:58 PM   #21
planet10 is offline planet10  Canada
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T line \ bass reflex enclosure suggestions
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I'm not an authority in passive radiator designs but to my knowledge the air inside a passive radiator enclosure is separated (not communicating with the outside) from the outside... my thinking was that it's a lighter version of the sealed enclosure because one of the walls (a portion) is replaced with a passive radiator which is much lighter that the wall it replaces and gives better bass...
extra bas because the pasive radiator is a substitute for a vent. Useful when you have a small box tuned high and othrtwise the vent would require a very large vent. I am not a fan of PRs.

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Old 18th July 2019, 07:29 PM   #22
krakatoa is offline krakatoa  Romania
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Ok 3rutu5 ... I'm gonna reformulate my thought on the project based on your last post: you have 3 pictures there:
- first boombox is not really that small but not really TL worthy, I have never tried a TL shorter than 70 cm in any simulation, and have built one 70-75 cm long with 10:1 shrinking rate (cross section) with smaller than recommended internal volume and I don't think it's a very good idea, the output is modest; the TEBM65 is a poor choice for portable audio due to it's low sensitivity, 80 db in nothing compared to to the 91 you get from FaitalPRO 3FE22! I have one and it's really really loud in 8 ohms, much louder than anything in the same size category... and probably also lighter than TEBM65 and occupies less internal volume (of the enclosure), don't know how it does lows compared to other drivers but I would say the best thing out there for size/sensitivity ratio
- second picture - that TL has unnecessary thick walls I know from practice 8 mm plywood will be just fine (for that sort of size of panels) perhaps even less (5-6mm); what I would try to do here is perhaps make a "cooller than Robocop" enclosure, a retractable/elongatable TL... or collapsible might be the right word, to be easy to carry around but when you arrive at the destination you open it to the functional intended size... a "box in a box" comes in mind or something like camera zoom lens (that stretches out allot)... think of how Batman's car does with it's hidden shields (YouTube)... and add some lens shutter mechanisms over the drivers. Material of choice may not be wood in this case.
Yes isobaric configuration (one driver sits behind the first, not facing each other) should work fine since it was used when you need a small box (car subwoofer that needs to fit in small trunk).
The critical factor to the success of your project seems to be achieving the "thump"... consider using a dedicated midbass driver + tweeter (tweeters can be very light) as oposed to a fullrage driver, the midbass unit should deliver easier, from what I know this is how it's done in the commercial world. Again I would look at the sensitivity of the driver when choosing.
By the way - just in case you didn't know - driver parameters will influence how much of the "thump" you get... rather than the design of the enclosure, so don't go for the TL just for that, chose the right driver and it's much easier. Look at the Bose Soundlink mini drivers, hey are like car subweoofers just very small - YouTube , YouTube , notice the neodynium magnet (oversized).
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Old 20th July 2019, 06:00 AM   #23
3rutu5 is offline 3rutu5  Australia
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Cheers for the suggestions, I had another thought as I have a set of ND65-4's sitting there from a failed venture. They struggled a bit in the last application, but got me thinking if the Japanese man can get bass out of a $3 set of cheap speakers using a rear loaded horn, that maybe I could as well..

I had a quick sketch using my stylus and if tuned to 70hz it appears that a wave length of 1.2m is needed and two Chambers of 0.025cuft. I have cheated by sharing the length between the two. I would need 1.4 for 60hz, but I don't think the little things can actually go that low without distortion.

Reckon it would work and potentially hit a few lower notes? I have some 12 and 16mm MDF already in my garage and could grab a 6mm sheet for folds if it helps get a bit more length.
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Old 20th July 2019, 10:42 AM   #24
3rutu5 is offline 3rutu5  Australia
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Quote:
Originally Posted by krakatoa View Post
Ok 3rutu5 ... I'm gonna reformulate my thought on the project based on your last post: you have 3 pictures there:
- first boombox is not really that small but not really TL worthy, I have never tried a TL shorter than 70 cm in any simulation, and have built one 70-75 cm long with 10:1 shrinking rate (cross section) with smaller than recommended internal volume and I don't think it's a very good idea, the output is modest; the TEBM65 is a poor choice for portable audio due to it's low sensitivity, 80 db in nothing compared to to the 91 you get from FaitalPRO 3FE22! I have one and it's really really loud in 8 ohms, much louder than anything in the same size category... and probably also lighter than TEBM65 and occupies less internal volume (of the enclosure), don't know how it does lows compared to other drivers but I would say the best thing out there for size/sensitivity ratio
- second picture - that TL has unnecessary thick walls I know from practice 8 mm plywood will be just fine (for that sort of size of panels) perhaps even less (5-6mm); what I would try to do here is perhaps make a "cooller than Robocop" enclosure, a retractable/elongatable TL... or collapsible might be the right word, to be easy to carry around but when you arrive at the destination you open it to the functional intended size... a "box in a box" comes in mind or something like camera zoom lens (that stretches out allot)... think of how Batman's car does with it's hidden shields (YouTube)... and add some lens shutter mechanisms over the drivers. Material of choice may not be wood in this case.
Yes isobaric configuration (one driver sits behind the first, not facing each other) should work fine since it was used when you need a small box (car subwoofer that needs to fit in small trunk).
The critical factor to the success of your project seems to be achieving the "thump"... consider using a dedicated midbass driver + tweeter (tweeters can be very light) as oposed to a fullrage driver, the midbass unit should deliver easier, from what I know this is how it's done in the commercial world. Again I would look at the sensitivity of the driver when choosing.
By the way - just in case you didn't know - driver parameters will influence how much of the "thump" you get... rather than the design of the enclosure, so don't go for the TL just for that, chose the right driver and it's much easier. Look at the Bose Soundlink mini drivers, hey are like car subweoofers just very small - YouTube , YouTube , notice the neodynium magnet (oversized).
thanks for some inspiration

the boom box is about 500mm long, so yes, no way a compact thing. As for the TLine attempt, it was a direct copy off somebody else, but i completely agree that the internals could have been much thinner than the 19mm pine used, i may have even been able to throw an extra fold in using the smaller gear. That project was about 12months ago and my first go at speaker building, which as mentioned i've already upgraded the pc speakers to something much much better, but still was a good experience.

I did look at the bose a while back, but couldnt find genuine, but instead quite a few clones. I'm wanting to really just recycle parts that i have lying around, hence the TEBM's, i also have a DTA-2 (2*15 watt) amp board and a 2.1 channel parts express board i was going to use, plus the ND65's i mentioned above. I do have a few other ideas, but having a hard time getting passed the boss (wife), but she doesnt have an issue as long as i'm not buying anything got a bit of pine, MDF, 20mm electrical conduit lying around as well and a 100mm dia PVC pipe, which allows for some different design options.
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Old 20th July 2019, 07:26 PM   #25
krakatoa is offline krakatoa  Romania
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You might be a begginer, so you didn't understood my sensitivity argument - the Dayto nAudio ND65 is built the right way for good bass reproduction while keeping the size small (honestly you could make this high excursion design at any size) but at a sensitivity of 80 db... well you need to double your power to get to 83 db SPL... and 10 times the power to get to 90db... understand now why I mentioned the FaitalPRO 3FE22 with 91 db sensitivity? yes you can pump power in a 80 db speaker... but you need more than 10 times the power to get to the FaitalPRO 3FE22 (for example, but it's a larger speaker)... but the FaithalPro has only an extra 60 grams and it's ok for that sort of size of enclosure. Two DD65 s would weigh 1.5 times the weight and the second unit would add 3 db of sensitivity, that's only 83 db.
Anyway... you can always sell something to get some money to play with. Nothing wrong to use what you got, It always reminds me of how they made an air filter with a sock and stuff they had out there where there is no package delivery - in Apollo 13, at least in the movie never checked if it was historic reality.
Between ND65 and TEBM I would choose ND65... or just put them both in the same box because it's large enough.
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Old 20th July 2019, 09:10 PM   #26
3rutu5 is offline 3rutu5  Australia
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Yes, you are right I didn't pick up on the sensitivity argument.

I should of probably not used the term boom box either and more portable speaker. Yes I would like to hear a bass note in the low 60/50's ie F3 or lower, but it would really be a more put it on the kitchen island or outdoor table and have it playing. The problem I had with the ND65'S originally is I used the DTA 2 amp and used my PC as the source with an equaliser and having a enclosure of 0.07cuft each with a port, it struggled (distorted) to turn it up over half volume listening to some recent music. Turning off the EQ resulted in the same problems but got a little more volume. These things modelled down to FS 60 with no issue in WiniSD, so asking more questions on the PE forums found that people used these with different music and also put caps on them to limit the bass. These drivers are very small and are actually a lie by calling them 2.5inch drivers as that is the dimensions to the extents of the frame. I also got the impression that 15watts a channel was too much for them, albeit people saying it was not enough. I ran a few different scenarios for my use of the 8ohm TEBMs (boombox ran KAB230 30w and others used the DTA2 15w) and found that they performed best in the application at the 10w.

On a side note I did buy a Peerless PR to use with the ND65'S, but didn't actually see or hear it move.

Thanks for the patience, I'm quite the beginner, just sit there scratching bmy head seeing those little Bose speakers and other mass production BT setups that have these tiny drivers moving passive radiators, although I did make my parents Bose SoundLink mini fail in the same way I did the ND65'S
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Old 21st July 2019, 08:08 AM   #27
krakatoa is offline krakatoa  Romania
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Here are some other facts you may not be aware off: adding a second driver (per channel) immediately adds 3 db extra sensitivity and reduces excursion & distortion by 50%, and will take double the power handling! This is how I build my TABAQ's - 2 drivers/channel and it worked; in practice you also get better bass reproduction including bellow Fs.
The size of the drivers is the size of the frame, actual working size is given in the Sd parameter - the "working" surface of the membrane (as piston, cone+half surround).
Maximum power rating is an absolute maximum and I think it refers to heat dispersion and nothing to do with what happens as excursion gets out of control bellow Fs - this is where you want your attention as designer to be (that's why they filtered the deep bass).
The "some recent music" thing might be where your problems start, this is not acoustic guitar is it? It's more like wreckless deep bass electronic music... that requires extra attention, they are the hardest things to reproduce especially on small speakers, ideally you would have large speakers with good excursion and power handling... the oposite of what small speakers do; just double the number of drivers in such situations .... or more than double...
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Old 21st July 2019, 08:57 AM   #28
3rutu5 is offline 3rutu5  Australia
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Ok I didn't know that, is that why people tend to put lots of small drivers in an array?. This might be a dumb question, but assuming you run this in parallel to keep the ohms at 4? Or did I get that back to front....and the other silly question is, double the drivers double the enclosure size?
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Old 21st July 2019, 12:09 PM   #29
Scottmoose is offline Scottmoose  United Kingdom
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OK, the above is a mite more nuanced, shall we say, since it ignores impedance. Doubling Sd gives a nominal +3dB but if wired in series you halve the individual current draw so in practice SPL is largely unchanged. Wiring in parallel halves the impedance / doubles the current draw compared to a single unit so in practice you get a nominal +6dB (3 for the doubled emitting surface, another 3 for the extra current).

For a given alignment 2 identical drivers require twice the Vb a single unit requires whether series or parallel (isobaric designs aside).
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Old 21st July 2019, 03:42 PM   #30
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T line \ bass reflex enclosure suggestions
Quote:
Originally Posted by krakatoa View Post
and reduces excursion ... by 50%]
I believe you end up with one-worth the excursion.

dave
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