Anyone know anything about Transmission line(speakers)

[strangeandbouncy]

Hi PRR,



  Pardon me. You misread my poor English, not the Fostex, the Lowther is VERY efficient - @3% - up to  106dB-1W-1m depending on cabinet. Lowther doesnt run that low according to Interweb(cant find any plots anywhere), but Audio Nivana Alnico plots look pretty amazing in both the 8 inch and 6.5 inch.

 actually, the fostex is <4 times as efficient as the Monacor 5 inch I was looking at (0.3%)!!!

 vv distortion and efficiency, I am not well read. In my (studio monitor) experience, higher efficiency has always meant higher distortion . . . Urei, Eastlake, JBL etc. Me-No-Likey. Always come home with an earache even at moderate levels.

 I totally agree that plots are ponypants. In my consideration, most driver manufacturers at best fudge results, and at worst lie. However, I have been looking at them for more years than I care to remember, and the Audio Nirvana plots look like there is cone breakup in large amounts above 3kHz. This has never been a pleasant experience thus far. I look forward to hearing them for real!

 Fostex is asking for a good run around the block as well.


   Kindest regards as ever,


   ANdyP

 

[abbey road d enfer]

vv distortion and efficiency, I am not well read. In my (studio monitor) experience, higher efficiency has always meant higher distortion . . . Urei, Eastlake, JBL etc. Me-No-Likey. Always come home with an earache even at moderate levels.

I would tend to think that high efficiency in itself is not the primary cause of earache. The three you mention are all x-over'd at about 800 Hz, where the woofer cone breaks up and the HF driver has significant THD.

 

[strangeandbouncy]

Hi Abbey Rd D


    True, but I do remember reading a long long time ago that nice compliant, rubber roll surrounds and low efficiency contributed heavily to ATC type Studio Bass drivers having lower distortion, at the expense of efficiency. And pa cabs often go three or four way, not reaching too high for the bass driver or too low for a horn. And lets not pretend that pa rigs have low distortion, although they are much better now than a few years ago. Id love to find out more if anyone can point me at some literature!



    Thank you all for your input, Guys!


  Kindest regards,


      ANdyP

 

[abbey road d enfer]

Hi Abbey Rd D


    True, but I do remember reading a long long time ago that nice compliant, rubber roll surrounds and low efficiency contributed heavily to ATC type Studio Bass drivers having lower distortion, at the expense of efficiency.

Distortion in LF loudspeakers comes mainly from two factors: non-linearities in the suspension (surround and spider) and variation of induction when the voice-coil moves.
The two common solutions to these problems are the use of particular geometry for the surround (single and multiple roll) and largely overhung voice-coil. Creating a profile that is stiff enough radially to support the cone assembly and linearly supple enough to allow large displacement is a challenge that designers are trying everyday to conquer. Using a largely overhung voice-coil has the immediate consequence that a larger portion of the voice-coil is inactive, just dissipating power, reducing the sensitivity by 6-10dB. It also has the side benefit of of allowing the extension of LF response (increasing Rvc reduces Qts, which allows the use of lower TS alignments), that's why HiFi manufacturers love them.

And pa cabs often go three or four way, not reaching too high for the bass driver or too low for a horn. And lets not pretend that pa rigs have low distortion, although they are much better now than a few years ago.

PA loudspeakers operate at acoustic levels that have almost nothing in common with studio monitors. A typical LF speaker operates at an average power of 500Wrms/2kWpeak and is expected to have a sensitivity of 98+dB/1w/1m and operate at least 3-4 hours in a row, 7 days. It is obvious that largely overhung VC is not an option. Loudspeakers designers today are requested to produce more LF spl out of the same cone surface, because the size of the rigs cannot be increased but the production wants louder. The only way is to improve the suspension. Increasing VC overhang is not an option because it is less efficient. Any increase in excursion is tainted with loss of efficiency. Some loudspaeker designers are experimenting with clever multiple gap and coil arrangements but today there is not a single commercial product using that.
The loudspeakers used in the UREI, JBL and Eastlake monitors were not the type used in PA. The JBL2231 used in the 43xx series had a longer VC and 93dB sensitivity, 4dB less than the 2205 destined for PA.

 

[strangeandbouncy]

Hi Abbey Rd,


  thank you very much for that. All good stuff. I though they were pa drivers, since they have linen folded surrounds, not rubber, and were not very compliant, but quite stiff. ( and efficient). Thanks for filling me in.


    Kindest regards,


      ANdyP

 

[abbey road d enfer]

Yes, JBL, having its roots in movie sound, always advocated efficiency. The models used in their studio monitors (or the domestic derived speakers) never got the full audiophile treatment. I think they had a butyl foam suspension, but the flat profile made them seriously non-linear.

 

[PRR]

> pa cabs often go three or four way

As has been said, PA systems have HUGE acoustic output in limited area, HUGE pressure.

As I calculated decades ago, IM distortion is related to acoustic power density, HF limit, and square of LF limit. From this I computed that the usual domestic 2-way was borderline acceptable, the classic A7 was perhaps acceptable (many A7s had specific problems), that higher levels led to a need for 3-way and 4-way systems for clarity even before the limits of horn-loaded drivers were reached. Around the same time Meyer was cleaning-up the driver problems and producing high-level systems which just about fit my envelopes. Every once in a while I look-up the current state of the art. Much has changed.... we can now compute SPL across the stadium floor across the audio band, and optimize arrays for even coverage. Community developed that 6"-coil mid driver, which vanished, but other cone drivers have made happy BIG mids possible (if rare). But good systems don't violate my envelopes, just fill them better.

Is there a lesson? Don't make your air-paddle too small for the lows it must carry. But OTOH if too big for the HF it must carry, it won't spew around a small room same-as the lows, which is "wrong" for small rooms.

> Lowther is VERY efficient - @3%...  Lowther doesnt run that low

In direct-radiators, low-frequency efficiency is strictly about cone area (and box volume, but that's more-free than cone size). A Fifteen can do 2%(?) at 50Hz. The smaller cones won't be 2% at 100Hz. If midband efficiency is 3%, then below 150Hz is sure to droop at least 6dB/oct (0.3% at 50Hz). You can get a 6+dB bump over a narrow band, not a lot. And not a big deal; that's what EQ is for.

But the real problem with a single wide-range driver is the IM distortion. It's so pervasive that many of us don't hear "loud" unless we hear IM. But of course a monitor should not be doing that.

Juan Ponce de Leon tromped ALL over Florida looking for that fountain (well, for gold). Building your own speaker may be such a journey.

 

[PRR]

I tried to spell Ponce's name correct, with the accent on the 'o', and the forum throws an odd error.

 

[strangeandbouncy]

Hi,


    We Brits cannot use our venerable Pound sign either! Had real trouble posting til I worked out what it was.

    In my quest, I have a fantastic model to try to AB against and try to emulate - The BBC LS3 5a. With an active crossover, or a digital crossover(with eq), a bunch of 5 inch drivers and tweeters, I must be able to build something that works. It does not have to go that low, and definitely doesnt need to go very loud. I even have a new pair of the same tweeters(Kef T27). I will probably end up using a sealed box pretty much the same size as the original, but look forward to playing around with some transmission line, - because I can and I wanna!

  I am only going to try good old fashioned no nonsense, (and low cost!) 1 inch voicecoil drivers. All the 3 inch voicecoil ones have considerable rising responses, and some wierd lumps and bumps, especially up near where I want to crossover. I know that the original B110 needed some serious eqing in the midrange to tame a hump, but it was a nice, smooth hump.


    Thank you all gentlemen for your fabulous input. I am just a tad wiser . . . . . . Yay!



      Kindest regards,



          ANdyP