Hi, I wanted to know the same...
As I am not a technical person so I searched the net and found below comparison, don't know if they are the truth.
I want to DIY a pair as well for a long long time but didn't and still don't know how to start.
(1) Sealed Cabinet or Closed Box, CB VS (2) Bass Reflexed or Ported, BR
(1) CB
Pro
(2) BR
Pro
(2) CB & BR VS (3) Transmission line, TL
(2) CB & BR
Pro
(3) TL (if it is a good pair)
Pro
Good evening!
As I am not a technical person so I searched the net and found below comparison, don't know if they are the truth.
I want to DIY a pair as well for a long long time but didn't and still don't know how to start.
(1) Sealed Cabinet or Closed Box, CB VS (2) Bass Reflexed or Ported, BR
(1) CB
Pro
- relatively simpler construction
- relatively smooth 12dB/oct low-frequency roll-off
- even distortion across frequency band
- lower efficiency
- relatively poor in bass punch subjective feeling
- relatively lower in power handling capability
- relatively easier of non-linear clipping of membrane at high power input level
(2) BR
Pro
- relatively higher in efficiency
- relatively higher in power handling capability
- relatively higher sound pressure output at low frequency
- less easier of non-linear clipping of membrane at high power
- higher low-frequency roll-off rate of 24dB/oct
- breathing noise at port
- subjectively, for some people, more colors of sound produced ("coloration", some kind of unknown (for me) distortion)
(2) CB & BR VS (3) Transmission line, TL
(2) CB & BR
Pro
- relatively simpler construction
- relatively small in size
- relatively cheaper to buy
- a lot of product providers, more available
- relatively easier to share the fun of HiFi with friends (usually they have the same kind of box)
- relatively lower in efficiency
- subjectively less natural in bass range
- relatively higher "coloration"
- relatively lower in power handling capability
(3) TL (if it is a good pair)
Pro
- relatively higher in efficiency
- subjectively sounded more naturally
- more richer and puncher in bass regenerated
- lower "coloration"
- relatively higher in power handling capability
- relatively lower in phase distortion across full range
- need to be a genius to understand how it work
- tedious process to make, need to be a talented carpenter
- relatively bigger in size
- need a big house
- need a big wallet
- need a wife who shares the same hobby
- need to be alone without friends admiring your achievements
- a lot of more cons than pros one might be thinking of but you still love them
- ... limitless
Good evening!
I don't agree, my MLTL's (mass loaded transmission line) are made with a total budget of 300€, and are used in a relative small room (3.5x6.5x2.5m). They are complex to design, but the woodwork is not different than a big reflex. They are not so much in fashion but sound better for me than a reflex because of the smaller air velocity in the port (that is not working like a reflex port) and mainly, a smaller group delay on the lower frequencies.
Sensivity (what you call efficiency, but isn't that) is the same as reflex, distortion is smaller (so also colouration as that is the good part of the distortion) and the excursion of the driver is slightly less for the same basss volume. But the main difference is the group delay that is closer to a sealed cabinet (so way less than a reflex) and that makes the bass tighter and more dynamic and less distorted.
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There are so many things in that list that are misleading or outright wrong.
There is so much design space across these boxes that they have to be looked at much more closely to say how and how they do not perform. As one moves from Sealed, to vented, to TL the number of degrees of freedom for the design grow considerably. As complexity grows the number of potential results dramatically increases with a wide range of possibilities.
The only one i am going to comment on is the efficiency. None of thes eboxes affect efficiency, they are all the same if they use the same driver.
A BR (and in much more complex ways a TL), will trade an increase in output near the lower cutoff for less output below a certain point.
dave
a paste job of posts from the late and great DJK:
Low Qts
Posted by djk (R.I.P.) on September 29, 2007 at 03:03:05
In Reply to: RE: JBL Scoop posted by Hornlover on September 28, 2007 at 08:33:11:
The optimum Qts for minimum box size and maximum bass extension is 0.312
Qts in the range of 0.25~0.40 is OK.
If much higher than 0.40 a sealed box is indicated, if much lower than 0.25 a horn is indicated.
************************************************** *********************
A little known fact is you can 'burn' Qts if it is lower than what you need(no more than 20%). Another tactic would be to use the low Qts to reduce the box size and raise the Fb to keep it flat.
The optimum Qts for an equalized 6th order Butterworth design(not to be confused with a bandpass design)is .312 .The formula for box size is Qts*Qts*4.1*Vas=Vb.The formula for Fb is (Fs/Qts)*.312 .For a Qts of .312 the Faux(eq frequency)=Fb with a Q of 2 .
************************************************** *********************
Box size is roughly proportional to the square of the Qts, so the lower the Q the smaller the box. Also the lower the Q, the higher the efficiency. Bass rolls off though if the Q is too low, the magnet can be too big for its own good.
For a vented box, the optimum Qts is 0.312
0.312 gives the best bass extension, minimum box size, and highest efficiency.
Posted by djk ( M ) on July 25, 2005 at 00:55:59
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
The correct box size for a Qts=0.312 woofer for the 6th order vented design is Vas4.1, Fb=Fs=Faux, Q=2 for Faux.
Without the Q=2 filter the box is an SBB4 (Super Boom Box 4th order), with the best transient response of all the standard vented alignments, with the filter it is a B6(maximally flat).
( there's a typo mistake above with the line:
"The correct box size for a Qts=0.312 woofer for the 6th order vented design is Vas*4.1"
That should read "The correct box size for a Qts=0.312 woofer is ~0.4X Vas"
as Qts^2 (0.312x0.312) * 4.1 = 0.3991104)
The underdamped 2nd order highpass filter will pretty much eliminate wasted cone movement below cutoff and since the peaking is at or near fb, thermal limits are generally more concern than excursion.
I'd imagine the technique really isn't used much in the word of fullrange drivers. Electro-Voice seemed to be the earliest using it with their Interface series and it worked pretty well with an 8 inch woofer plus 12 inch passive radiator. Cerwin Vega used it with two bookshelf speakers.
Hornresp is useful for designing 6th order bass reflex.
DCR and Double BR may offer possibilities. I don't know how to do Clement's "H-PAS" - is there a straighforwards design approach for the H-PAS ?
Low Qts
Posted by djk (R.I.P.) on September 29, 2007 at 03:03:05
In Reply to: RE: JBL Scoop posted by Hornlover on September 28, 2007 at 08:33:11:
The optimum Qts for minimum box size and maximum bass extension is 0.312
Qts in the range of 0.25~0.40 is OK.
If much higher than 0.40 a sealed box is indicated, if much lower than 0.25 a horn is indicated.
************************************************** *********************
A little known fact is you can 'burn' Qts if it is lower than what you need(no more than 20%). Another tactic would be to use the low Qts to reduce the box size and raise the Fb to keep it flat.
The optimum Qts for an equalized 6th order Butterworth design(not to be confused with a bandpass design)is .312 .The formula for box size is Qts*Qts*4.1*Vas=Vb.The formula for Fb is (Fs/Qts)*.312 .For a Qts of .312 the Faux(eq frequency)=Fb with a Q of 2 .
************************************************** *********************
Box size is roughly proportional to the square of the Qts, so the lower the Q the smaller the box. Also the lower the Q, the higher the efficiency. Bass rolls off though if the Q is too low, the magnet can be too big for its own good.
For a vented box, the optimum Qts is 0.312
0.312 gives the best bass extension, minimum box size, and highest efficiency.
Posted by djk ( M ) on July 25, 2005 at 00:55:59
A 2 cu ft 2nd order sealed box with an F3 of 30hz can only be 0.18% efficient (84.55dB).
A 2 cu ft 4th order vented box with an F3 of 30hz can only be 0.36% efficient (87.56dB).
A 2 cu ft 6th order vented box with an F3 of 30hz can only be 0.90% efficient (91.54dB).
The correct box size for a Qts=0.312 woofer for the 6th order vented design is Vas4.1, Fb=Fs=Faux, Q=2 for Faux.
Without the Q=2 filter the box is an SBB4 (Super Boom Box 4th order), with the best transient response of all the standard vented alignments, with the filter it is a B6(maximally flat).
( there's a typo mistake above with the line:
"The correct box size for a Qts=0.312 woofer for the 6th order vented design is Vas*4.1"
That should read "The correct box size for a Qts=0.312 woofer is ~0.4X Vas"
as Qts^2 (0.312x0.312) * 4.1 = 0.3991104)
The underdamped 2nd order highpass filter will pretty much eliminate wasted cone movement below cutoff and since the peaking is at or near fb, thermal limits are generally more concern than excursion.
I'd imagine the technique really isn't used much in the word of fullrange drivers. Electro-Voice seemed to be the earliest using it with their Interface series and it worked pretty well with an 8 inch woofer plus 12 inch passive radiator. Cerwin Vega used it with two bookshelf speakers.
Hornresp is useful for designing 6th order bass reflex.
DCR and Double BR may offer possibilities. I don't know how to do Clement's "H-PAS" - is there a straighforwards design approach for the H-PAS ?
Mmm, I think we have been through this before, and with much of the same misleading rubbish. I must be a genius according to the second post since I have modelled hundreds of LT's and built probably around a dozen. So that comment is ridiculous. I have also built BR with the same driver and done A/B comparisons. Subjectively the TL sound cleaner in the mids and the bass deeper and more effortless. I definately prefer TL's, but not all drivers will give you a great result. The only disadvantage is the larger cabinet which increases the labour and material costs of the cabinet, and also decreases WAF. A MLTL is not complex nor difficult to build, and LT's are more forgiving if you get the tuning off a bit. However, 2 way MLTL's made with smaller drivers in tall slim cabinets nicely finished, mostly takes care of the WAF, and they can work well in small rooms in my experience. It is all bound up in how you design them. and that is the fun part.
In your experience, which technical parameters of the controller are important for suitability for the TL cabinet? is it low Qts? Which specific controller models are suitable for TL? Thanks
I looks like a BR but is in fact a TL
Compilation of MJK ANSYS simulation of BR vrs ML-Voigt (an ML-TL variant).
dave
Let me add: The math/physics of a BR assumes that the shape of the box is relatively cubic. No dimension is significantly larger than teh other. As one dimensions increases (and the others decrease) a quarter-wave can start to occur over the longer axis. So the physics start to change.
The shape of the box makes a difference.
dave
The shape of the box makes a difference.
dave