Hello all, I'm wanting to create a portable boombox and want to use this oppertunity to expand my scope of builds into my first Transmission Line. I've been doing some cinsiderable reading on the subject and I *think* I'm getting the hang of most of it.
Before I continue further I thought I'd ask your advice... I don't have access to MathCad /sketch up at school, but I wanted to post a mockup of the t-line and dimensions so that you guys could yay or nay my current design...
I'm building the enclosure around the Tang band 5 1/4" speaker (fs 55hz).
Tang Band W5-704D 5-1/4" Woofer
crossed with a 3" fountek driver:
https://www.parts-express.com/fountek-fe85-3-full-range-speaker-driver--296-717
After reading MJK's work and tables I've concluded that the line needs to be aprox. 49" in length with a cross section of 14.57^2" (94cm^2... the reduction from a 61.1" to 49" line is due to the .8 fudge factor- if I'm understanding that right?)
My concern is how close the woofer(s) will be to the mouth of the line and if this is feasible?
The enclosure is already nearly 25" wide, 14" high and 10" deep... I feel if it get's any larger it will no longer be considered in the realm of a "portable boombox."
Any suggestions?
Before I continue further I thought I'd ask your advice... I don't have access to MathCad /sketch up at school, but I wanted to post a mockup of the t-line and dimensions so that you guys could yay or nay my current design...
I'm building the enclosure around the Tang band 5 1/4" speaker (fs 55hz).
Tang Band W5-704D 5-1/4" Woofer
crossed with a 3" fountek driver:
https://www.parts-express.com/fountek-fe85-3-full-range-speaker-driver--296-717
After reading MJK's work and tables I've concluded that the line needs to be aprox. 49" in length with a cross section of 14.57^2" (94cm^2... the reduction from a 61.1" to 49" line is due to the .8 fudge factor- if I'm understanding that right?)
My concern is how close the woofer(s) will be to the mouth of the line and if this is feasible?
The enclosure is already nearly 25" wide, 14" high and 10" deep... I feel if it get's any larger it will no longer be considered in the realm of a "portable boombox."
Any suggestions?
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You might try the Accidental Mass Loaded Transmission Line (AMLTL) technique to size your TL and port based on a bass reflex assumption. Search for thread with that name. If the driver is moderate (0.45) to higher Qts it can work well. Does not work as well for low Qts drivers.
No need to operate in stereo. Speakers are simply too close together to have much effect. Better to sum mono. Can look at it like this, it's now half the size or has better bass extension when maintaining same internal overal volume as is.
I've been considering mono, and it seems more and more likely if i want to do a portable T-Line that gets into the 50s Hz range, however I'd really like to go stereo (I'm getting back into my Zepplin albums and would miss the cross-fades).
I'm planning on making the xo around 150hz for the Tang Band's and the full ranges handling everything above.
Is this a lost cause (without going bass reflex/ported)?
I'm planning on making the xo around 150hz for the Tang Band's and the full ranges handling everything above.
Is this a lost cause (without going bass reflex/ported)?
Perhaps this amp would allow you to cross active and sum bass too
Lepai LP-168HA 2.1 2x40W Mini Amplifier + 1x68W Sub Output (amazon has it too)?
I've been considering something like this for a deep but low profile sound bar to work with our TV table, The wireless soundbar we use has horribly flabby bass and too high a crossover
Lepai LP-168HA 2.1 2x40W Mini Amplifier + 1x68W Sub Output (amazon has it too)?
I've been considering something like this for a deep but low profile sound bar to work with our TV table, The wireless soundbar we use has horribly flabby bass and too high a crossover
You won't hear those cross fades unless you are centered and close. So unless it's sitting on a shelf above a work bench, stereo goal is pointless.
I like my Zep too. When designing speakers I always test in mono. Stereo just makes it sound fancier. I wonder how many people listen to that new pair of speakes with only one hooked up and run mono would feel about their purchase 😉
I like my Zep too. When designing speakers I always test in mono. Stereo just makes it sound fancier. I wonder how many people listen to that new pair of speakes with only one hooked up and run mono would feel about their purchase 😉
Zobsky:
I looked into the Lepai amp... but I have a friend aboard now on the project that wants to use the opportunity to build the amp/ switchboard/ fm tuner/LCD display etc. himself while I do the woodwork and cabinet design.
I plan on having the sides/front/back made of wood (maybe pecan since we have a lot of dead trees here), but the top made of plexiglass so the 'guts' are visible - considering all the effort and thought being put into this I'd like to showcase it's innards.
Greebster:
You make good points. I guess I'm just reticent of losing the 'fancy' sound/look of stereo. 😱 The trade off of Summing to mono should increase the db/spl levels, yes?
my initial inspiration was Paul Carmody's Sprite:
I looked into the Lepai amp... but I have a friend aboard now on the project that wants to use the opportunity to build the amp/ switchboard/ fm tuner/LCD display etc. himself while I do the woodwork and cabinet design.
I plan on having the sides/front/back made of wood (maybe pecan since we have a lot of dead trees here), but the top made of plexiglass so the 'guts' are visible - considering all the effort and thought being put into this I'd like to showcase it's innards.
Greebster:
You make good points. I guess I'm just reticent of losing the 'fancy' sound/look of stereo. 😱 The trade off of Summing to mono should increase the db/spl levels, yes?
my initial inspiration was Paul Carmody's Sprite:
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Hi,
TL is not the way to go for portable full stop, bloated and oversized.
Go sealed, outdoors bass is a joke without room gain, or bass vented.
i'd go one bass, L+R mid treble, strereo amplifier with one
channel inverted, one L or R wired out of phase and the
bass unit across L+R positive for bridging mono output.
Simple series L for bass and C for L and R.
rgds, sreten.
TL is not the way to go for portable full stop, bloated and oversized.
Go sealed, outdoors bass is a joke without room gain, or bass vented.
i'd go one bass, L+R mid treble, strereo amplifier with one
channel inverted, one L or R wired out of phase and the
bass unit across L+R positive for bridging mono output.
Simple series L for bass and C for L and R.
rgds, sreten.
I'd be inclined to keep it simple. Two fullrange speakers, and a highpass active filter so you don't waste headroom on bass they can't handle. Try prototyping using junk particleboard if you want to try anything fancy.
🙁 I didn't realize a transmission line was that dependent on room gain... I've made several ported and sealed enclosures and was looking to push myself - while extending the bass, and have a visual "cool" factor when viewed from top down (plexiglass clear top).
*edit*
I know placement / wall boundaries helps with bass, I didn't think it was a must for T-Lines, though...
I know placement / wall boundaries helps with bass, I didn't think it was a must for T-Lines, though...
I was just reading a post where MJK said he was sick of building big boxes, and that an MLTL would give you the same tuning in a shorter line or lower tuning in the same length. Or it may have been planet10.. Hmmm
Also i believe this is based on MJK's work and has just had a some major upgrades. Its free and easy.
Transmission Line | Leonard Audio
Also i believe this is based on MJK's work and has just had a some major upgrades. Its free and easy.
Transmission Line | Leonard Audio
It appears the discussion missed the point of "mono". The thrust of the original recommendation was to go mono is for the bass. Mono Bass provides you double the enclosure volume from which you will be trying to squeeze low end.
Stay stereo for your full-ranges above 150Hz. This is a very practical compromise.
Remember that your ears have >>NO<< ability to localise bass below about 80Hz, and stuff all ability until well into the 100s of Hz, so this will have no meaningful impact on the stereo imaging of the system.
On the specific question of the TL - I will leave that to the experts.
Stay stereo for your full-ranges above 150Hz. This is a very practical compromise.
Remember that your ears have >>NO<< ability to localise bass below about 80Hz, and stuff all ability until well into the 100s of Hz, so this will have no meaningful impact on the stereo imaging of the system.
On the specific question of the TL - I will leave that to the experts.
You can also do something like this - a matrixed triple speaker approach. From this thread: http://www.diyaudio.com/forums/full-range/257110-master-nagaoka-tetsuo-explorations-matrixed-single-stereo-speakers.html
The central channel has the HF's bypassed and handles the mids and bass. All three channels handle the bass so that you get less cone excursion and lower distortion for the bass production in a small portable that doesn't use big woofers.
There is also the Nagaoka matrix:
My implementation with three drivers in one box with one reflex vent ended up looking like this:
Measurement looked like this:
An externally hosted image should be here but it was not working when we last tested it.
The central channel has the HF's bypassed and handles the mids and bass. All three channels handle the bass so that you get less cone excursion and lower distortion for the bass production in a small portable that doesn't use big woofers.
There is also the Nagaoka matrix:
My implementation with three drivers in one box with one reflex vent ended up looking like this:
Measurement looked like this:
A single eg 8" mounted on the bottom into 1 volume would also allow some flexibility in positioning also. So you could sit the box on the ground with small legs and get some boundry gain or stand it up next to a car with MIDs pointing up omni style and get boundry gain from the car.
Just thinking out loud. 😉
Just thinking out loud. 😉
Huh, very interesting stuff guys. Keep spitballing, I'm loving the ideas (and learning a lot)!
XRK971:
the matrix speakers are very intriguing... I'll have to read through those threads more, though very cool stuff! That would certainly help with a wider dispersion of in phase listening... hmm. This seems to overlap with Thunk303's concepts.
Thunk303
If you can find me a link to where MJK talks about how to make a reduction in cab size, I'd love to take a look at it.
Googlyone:
If I'm reading you correctly, you are suggesting a single dedicated woofer for "sub" work, and then L+R speakers for stereo (creating a separate compartment for the woofer- maybe even putting this in the t-line to fulfill my inclinations...)? OR are you suggesting sum/mono the woofers in this arrangement while keeping the full ranges stereo?
Also, at what point does spl level become too low to contribute to the listening experience? I've been trying to devise ways to utilize the t-line and keep the f3 in the 50s hz range at 80db before it drops off significantly.
edit**not to take the thread off track, but I'll just throw up a subwoofer I'm finishing for my SO to show my enjoyment of tackling projects with a twist/creativity (and to show I'm receptive to alternative / unique ideas...)
XRK971:
the matrix speakers are very intriguing... I'll have to read through those threads more, though very cool stuff! That would certainly help with a wider dispersion of in phase listening... hmm. This seems to overlap with Thunk303's concepts.
Thunk303
If you can find me a link to where MJK talks about how to make a reduction in cab size, I'd love to take a look at it.
Googlyone:
If I'm reading you correctly, you are suggesting a single dedicated woofer for "sub" work, and then L+R speakers for stereo (creating a separate compartment for the woofer- maybe even putting this in the t-line to fulfill my inclinations...)? OR are you suggesting sum/mono the woofers in this arrangement while keeping the full ranges stereo?
Also, at what point does spl level become too low to contribute to the listening experience? I've been trying to devise ways to utilize the t-line and keep the f3 in the 50s hz range at 80db before it drops off significantly.
edit**not to take the thread off track, but I'll just throw up a subwoofer I'm finishing for my SO to show my enjoyment of tackling projects with a twist/creativity (and to show I'm receptive to alternative / unique ideas...)
Attachments
Last edited:
Maybe it's about tapering the line..🙄
About mono/stereo and the realization of the "skinned" sub+sats, I'd suggest to keep 'em ( the sats) aligned, isolated, and about 1 m divide. It's the sub that may stay hidden...
Nice PIC man. Sometimes it gets too constraining just trying to achieve the nth degree of performance.
Hobbies should be fun!
I can't find the thread I was reading yesterday where MJK & P10 had the discussion but I'll keep looking.
I'm sure it was a full range thread.
Seriously have a go with that Leonard audio link I shared. Its very easy to use, but yes a tapered mass loaded TL would be the first choice if you want the smallest possible TL.
I also think its very wise to trade some low end extension for SPL capability in these circumstances. Protects the driver by using the cab as an acoustic high pass filter and let's you have a handy outdoor upper bass boost. Tune to taste with stuffing the line.
Hobbies should be fun!
I can't find the thread I was reading yesterday where MJK & P10 had the discussion but I'll keep looking.
I'm sure it was a full range thread.
Seriously have a go with that Leonard audio link I shared. Its very easy to use, but yes a tapered mass loaded TL would be the first choice if you want the smallest possible TL.
I also think its very wise to trade some low end extension for SPL capability in these circumstances. Protects the driver by using the cab as an acoustic high pass filter and let's you have a handy outdoor upper bass boost. Tune to taste with stuffing the line.
..but a cab IS a highpass device, together with the driver. Well, the cab is also a lowpass device. So what's a cab ?
[bandpass] 😛
I've seen Ifearfractals in another thread about "backhornloading"
but both speakers end always in the same enclosure, same aim to be a
"portable boombox".
So we should limit the thing...or make the goal a step higher ( or lower 😛 )
If /when plaiyng bi-channel recordings, as it's the norm ( but don't confuse with the " joint stereo" mark on the Mp3 encodings 😕 )
we should keep focusing on the (phisical) separation of the two sound sources.
Sooo, same things: better focusing on the power/Spl to be achieved, thermal limits, in-environment considerations, etc etc.
[bandpass] 😛
I've seen Ifearfractals in another thread about "backhornloading"
but both speakers end always in the same enclosure, same aim to be a
"portable boombox".
So we should limit the thing...or make the goal a step higher ( or lower 😛 )
If /when plaiyng bi-channel recordings, as it's the norm ( but don't confuse with the " joint stereo" mark on the Mp3 encodings 😕 )
we should keep focusing on the (phisical) separation of the two sound sources.
Sooo, same things: better focusing on the power/Spl to be achieved, thermal limits, in-environment considerations, etc etc.
Exactly Pico. Most cabinets are aiming for maximum flat low end extension. With a single driver in a boom box size played outdoors that would a big ask. So the 50hz limit seems smart 😉
Has anybody tried Transmission Line | Leonard Audio yet? Any feedback?
Has anybody tried Transmission Line | Leonard Audio yet? Any feedback?
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