[Ultralight]

Sorry about this basic question.  If I had a full range single driver speaker with a front port, doesn't the front port let air in and out, and act almost like a 2nd driver in terms of imaging - meaning imaging is not as precise compared to a sealed unit?

Thanks in advance for any comments.

[sts9fan]

Not exactly
http://en.wikipedia.org/wiki/Bass_reflex

[planet10]

Not a bad article. It doesn't directly address the question, so let me extend it.

An ideal port acts as a bandpass filter (not the Wiki comment about midrange leakage). Ut has a barrow bandwidth and is at a low frequency. At the frequencies in question the wavelengths are usually quite a bit longer than the size of the cabinet -- ie you can't get the port far-enuff away from the driver for it to act as a 2nd radiator. If you do get a box large enuff for the distance to be significant, then the box is likely no longer a BR (ie it could be an ML-TL).  Given the context of your other thread you would not have such an issue.

As a sidenote, the Martin King software will model the effect of port placement. Most people would use this modeler to design ML-TLs thou.

dave

[JLM]

Many neglect what happens to higher frequencies of the back wave.  They are out of phase (so IME dipoles don't make sense).  Most cabinets have some sort of absorption material, but with the much higher spls inside the cabinet, can't be highly effective.  And the driver cone material is no where close to acoustically opaque.  So much of the out of phase backwave (especially with small cabinets) gets reflected and a muffled version comes through to smear the sound.  Tapered cabinet designs (pipes, transmission lines, rear loaded horns) can reflect much of the sound away from the driver, avoiding the issue and providing a noticably clearer midrange.

Out of those three cabinet types, transmission lines (by definition) are designed not reflect the backwaves and extend bass with a frequency roll off that compliments room gain.

[speakerman19422]

What is the exact definition of a transmission line?  Is a tapered pipe a t-line? Is a stuffef pipe a t-line. What does it have to be stuffed with? Is it more heavily stuffed ar the beginning or end of line terminus? Is the line length equal to cutoff frequency of a 1/4 wavelength?

[planet10]

What is the exact definition of a transmission line?  Is a tapered pipe a t-line? Is a stuffef pipe a t-line. What does it have to be stuffed with? Is it more heavily stuffed ar the beginning or end of line terminus? Is the line length equal to cutoff frequency of a 1/4 wavelength?

In audio it depends on context and who you are talking too.

In its widest use, any 1/4 or 1/2 wave resonator.

And in its narrowest sense, there is a school that takes the title from Bailey's seminal article and says that it is a quarter wave resonator stuffed until aperiodic. Funny thing is that the example Bailey shows in the same article would not qualify in that stricktest sense as a TL.

dave

[speakerman19422]

If Bailey's Radford lines are not considered t-lines, The IMF,TDL and Fried designs would not be either.

[planet10]

If Bailey's Radford lines are not considered t-lines, The IMF,TDL and Fried designs would not be either.

Indeed. I have had arguments with these guys, it seems silly to me to restrict a class of speakers to a poorly choosen article title.

dave

[speakerman19422]

I would never discount Dr. Bailey,s proven designs. I think Fried and Wright learned a lot form the Bailey designs. Many of the computer designed t-line designs have the driver placment at 1/3 of the line length. I would consider them to be a stuffed pipe. One designer I know uses driver Vas=Vb. The lines using foam are different then the Acousta Stuf  lines even if the results are similiar. If I had not been a long time customer of Fried and lived near where he assembled his speakers I never would have gotten into this hobby. Planet 10 it is nice to trade info and share opinions. . Some forums are full of people who want to put other people down. Some people buy a computer program to design encloures and crossovers and they think they are experts. You know how time consuming it is to settle on the most optimum design by testing and changing be it stuffing or crossover values. By the way I saw that Celestion has produced some new runs of the Kef B110 drivers.

[planet10]

I would never discount Dr. Bailey,s proven designs. I think Fried and Wright learned a lot form the Bailey designs.

Radford, IMF, TDL are all direct descendents of the Bailey.

Many of the computer designed t-line designs have the driver placment at 1/3 of the line length.

One-third is only approximate. Fine tuning can be done with cms making a difference. some of the classic lines ended up with an "accidental" driver offset. The TLS80s i had certainly did.

I would consider them to be a stuffed pipe.

Pretty much a good definition of the original Bailey. Well except that Bailey (and Radford et al) had a prechamber.

One designer I know uses driver Vas=Vb.

That suggests to me an overly small box for a TL

The lines using foam are different then the Acousta Stuf  lines even if the results are similiar.

The results are only close when the amount of attenuation of the line harmonics are the same. Geometry also plays a big role. Foam is often used because it allows more consistent results when manufacturing many.

If I had not been a long time customer of Fried and lived near where he assembled his speakers I never would have gotten into this hobby.

We were a Fried dealer. The designs definitely influenced me. And i may have influenced his. 6 months or soafter designing a truncated pyramid for customers building H kits, and showing it to Fried, something similar started showing up in his.

Some forums are full of people who want to put other people down.

Indeed.

Some people buy a computer program to design encloures and crossovers and they think they are experts.

The computer program is only a basic tool, some of them quite good, but you still need to know what you are doing. And experience goes a long way.

crossover values.

I avoid XOs if at all possible, and prefer simple Line Level XOs if i can't (and place them where they are least objectionable)

By the way I saw that Celestion has produced some new runs of the Kef B110 drivers.

I do hope they improved it. By today's standards B110 is only a midlling good driver (much as i loved them in their day). I have a pair here that look new, if anyone is interested.

dave

[speakerman19422]

Driver Vas does vary a lot. I have always preferred drivers with large Vas and low qts. Have used some low priced high qts. drivers in t-lines just to experiment. These were meant for closed box not bass reflex.  High qts. do have their limitations but still sound more natural in t-lines. .

[planet10]

There are more variables than those, but a driver with too low a Vas, and too low (or high) a Qt often has issues with being put in a TL. A high Qt driver, can thou take advantage of a stuffed till aperiodic T-line.

dave

[JLM]

It was a "forced" audition of Fried model H (LS3/5A satellites with the coffin stereo TL woofer) by a salesman at a local stereo shop in 1976 that exposed me to the magic of stereo imaging, deep/fast/musical bass, and introduced me to the serious side of high end audio.  Have managed to own Frieds almost ever since.

Thanks Bud, et al.

[speakerman19422]

One really informative article on t-line theory was Works in Progress by  by Kevin Blair from Speaker Builder 2-1994. There were not any formulas given but the insight on theory is really well written. One of the best cut to the chase articles that give the novice insight to the many design aspects.

[planet10]

Fried model H (LS3/5A satellites...

Other than using the same drivers & a similar size box, they bore little resemblance to the LS3/5A.

http://www.t-linespeakers.org/classics/friedH/fried_H.html

dave

[speakerman19422]

Back when the Model C were released they were the upgrade to the B2. The Ls3/5a had a bump in the bass .The complicated crossover sounded like one compared to the simple 6db crossover used in the B-2   I preferred the B-2 over the Ls3/5a. The old Dynaudio D-28H had limited high end response compared to what is now available but could handle high spl. Thought I would mention the Kef B110 since so may people are looking for replacement drivers.

http://www.hi-fidelity.com/RogersParts.html

[JLM]

Yes, the Fried satellites were LS3/5a "clones" of some sort.  I upgraded to the B2 (from sealed to aperiodic with new midrange drivers). 

A friend built (and then did several mods to them) Fried Model C5's (truncated pyramid with TL midrange).  Amazing amount of bass, I loved those speakers, but he moved onto a SET/Lowther route.  Yet he wouldn't sell them to me.   

(Dang, I just realized that if he'd sold them to me I would now have 4 complete audio systems.)

Sorry for getting off topic.   

[speakerman19422]

The B-2 had the Dalesford 5". The Fried literautre states this. I was told they were oem units not stock drivers.  I never saw  the 5" driver outside of the box to compare.  They would sound better having the crossover rewired from parallel to series. The Dalesford drivers custom made for Fried were far different then the stock units. The 6.5" and 10" I have use larger magnets and longer voice coils. That is one of the reasons why they could play so much louder then the Kef ,Audax and stock Dalesford units.