Beyond the Ariel - Page 97 - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th June 2007, 06:37 AM   #961
diyAudio Member
 
Graham Maynard's Avatar
 
Join Date: Dec 2003
Location: UK
Hi Zene,

Surely, adding a series R decreases electrical Q, thereby limiting the back-EMF induced current peaks which could trouble lesser amplifiers ?

Adding series R also impairs *dynamic* transduction capabilities and electro-mechanical damping, thereby allowing a cabinet air-spring to have much greater effect upon response - if - this is prefered instead of accurate transduction.

Thus any change in *steady sine* measured F3 can only be due to an enclosure modifying (= distortiing) *music* waveform transduction.

Cheers ......... Graham.
  Reply With Quote
Old 6th June 2007, 06:51 AM   #962
diyAudio Member
 
Lynn Olson's Avatar
 
Join Date: Jul 2004
Location: Northern Colorado
Default Re: Inline resistors

Quote:
Originally posted by Zene Gillette
Lynn ... You may have missed my question when your computer went nuts. May I ask again?

"Would you be kind enough to give the good and bad points of adding inline resistors to gain Q when it is seems necessary to bring the F3 lower?
If already mentioned will you link to post?"
Zene
The motherboard and power supply swap will happen tomorrow, thank goodness, so I can get away from the laptop and the sometimes shaky WiFi connection.

Your question is a good one, and I've been thinking of an answer. I don't have a good one right now.

From an engineering standpoint, the power amplifier source impedance, voice coil resistance, wire resistance, and any intentionally added resistance are all in series. Of all these resistors, the intentionally added one is probably the best!

The source Z of the power amp is intermingled with the amplifier's distortion, since it is a virtual resistor comprised of the nonlinear gain elements of the amplifier and its feedback loop. The VC resistance is slowly modulated by the heating of the voice coil, with a time constant of several seconds. The speaker-wire resistance is slightly affected by corrosion on the surface of the copper wire.

So in theory, intentionally adding resistance should be quite benign sonically, and a simple way to raise Qes and Qts. It does seem a shame to throw away expensive amplifier watts in a resistor, though. This is where twiddling with the feedback of the amplifier to synthesize a higher output resistance has a certain appeal - at least all of the watts get used.

In practice - well - I remember the time Gary Pimm and I were twiddling with his speaker system, measuring and listening. He's using one of those Chinese ribbon tweeters with about 95 dB/metre efficiency, and like other ribbons, the thing is a flat-impedance resistive load, greatly simplifying the crossover design.

As it was, the speaker was quite close to flat, with the ribbon tweeter needing no more than 1 dB of attenuation to make the system almost totally flat. It sounded the way it measured, just a little bright, but a good design overall, and very lively and sparkly sounding. So we added a 0.5 ohm series resistor - not much at all, really - and measured. Ah, perfectly smooth, wonderful.

But the dynamics in the treble - and only in the treble - were obviously flattened, with a noticeable shut-in quality. Gary Pimm and I just looked at each other. This was an unexpected result - the resistor was a top-quality Ohmite wirewound power resistor - and in terms of spectral balance, the sound was more pleasant and better-balanced.

But the loss of dynamics was no illusion. When the resistor was bypassed with cliplead, the dynamics came right back again, along with just a slight amount of brightness. Now with a compression driver, this wouldn't be surprising - the multiple back-EMF resonances of compression drivers are quite touchy about any series resistance between the CD and the amplifier, with a low-Z source being greatly preferable.

But the ribbon tweeter basically didn't have any back-EMF resonances, at least any we could measure. Maybe they were lurking down in the noise somewhere, and were touchy about any series R between them and the amplifier.

Gary and I don't like tipped-up speakers, preferring a warm tonal balance. But we both agreed that choosing between a trace of brightness and vivid dynamics, versus even response and flattened dynamics, was easy. No series resistance in the Pimm loudspeakers. This was something I'd noticed about the Ariel some years back - that no series R sounded best, regardless of balance. Even something as marginal as bi-wiring opened up the sound - and bi-wiring is pretty small potatoes in my book.

So intentionally adding series R is something that should be benign, but in sonic terms, has a subtle, and maybe not-so-subtle, flattening effect. I am a bit suspicious of CD horn shelf equalization for a similar reason - series R does something to the sound that isn't good, but I'm not too sure why, except for interactions with low-level back-EMF resonances.

I guess this comes down to getting burned with the complex crossovers I used to design in the late Seventies. The systems were flat, coloration was very low, considering the dreadful drivers of the day, but the sound was undynamic and tone colors were muted. Not much sparkle or liveliness, in other words.

12 years later, when I was designing the Ariel and its 5 dB greater sensitivity, I discovered that the crossover was exquisitely sensitive to parts quality, especially the capacitors in the HF section. The Sprague 730P and Hovland were the only ones of the day that seemed transparent enough, and the Hovland irritatingly enough required a crossover adjustment to maintain the same subjective balance. I was not happy to make this discovery - parts tweaking is one of my most annoying and least rewarding hifi activities, something I'd rather not do at all.

Nowadays we have many more choices but cap coloration is still an awkward business in a high-resolution speaker - and I found out the hard way that the higher the efficiency, the less forgiving the speaker is of mediocre crossover parts. You can throw junk at a 86 dB/metre speaker and it isn't that audible. 92 dB/metre and up is a different ballgame. I'm expecting 97~100 dB/metre to be completely unforgiving of crossover parts quality - a severe incentive to keep complexity down. These drivers are expensive - the idea of wasting that much money on crossover parts isn't attractive at all.
  Reply With Quote
Old 6th June 2007, 07:30 AM   #963
mige0 is offline mige0  Austria
diyAudio Member
 
mige0's Avatar
 
Join Date: Jan 2005
Location: Austria, at a beautiful place right in the heart of the Alps.
Hi

I made basically the same observations on passive crossover parts sensitivity and the impact of series resistance between amp and speaker. This is also the reason why I go with active designs when ever possible.

Interesting enough that the relatively high impedance resistance of output transformers does not seem to affect the quality of a chain in the same way.

Adding an Ohm or so to the output of a solide state is not really a good possibility to mimic a tube amp sound wise.


Greetings
Michael
  Reply With Quote
Old 6th June 2007, 02:17 PM   #964
JohnL is offline JohnL  United States
diyAudio Member
 
JohnL's Avatar
 
Join Date: Apr 2004
Location: Tampa, FL
Hey Lynn, I know you were looking at AMT's originally as a possiblity for a tweeter for this. I guess I'm the cheerleader for these things, so I thought you might want to see this. Evidently Beyma is in the process of releasing a pro audio AMT tweeter. It doesn't look like a dipole (Should I say it looks like it has a cup on the back), but it looks like a pretty potent unit. I hope their pricing is a little more favorable than Mundorf's.

Beyma TPL-150

Click the image to open in full size.
  Reply With Quote
Old 6th June 2007, 03:16 PM   #965
el`Ol is offline el`Ol  Germany
diyAudio Member
 
Join Date: May 2005
Location: Bavarian Forest
Sorry for coming so late, but I have to correct the statement about the dynamic capabilities of ESLs made at the beginning of the thread.
http://www.sonus.de/php/p_produkte.php?produkt_id=15
I have not listened to that beast, but the 123dB at 4 meters is impressive.
  Reply With Quote
Old 6th June 2007, 05:05 PM   #966
Few is offline Few  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Maine, USA
Thanks, el`Ol, for the link and for the welcome reality check.
  Reply With Quote
Old 6th June 2007, 05:07 PM   #967
diyAudio Member
 
slowmotion's Avatar
 
Join Date: Nov 2002
Location: Norge
I like using amps with highish output impedance for compression drivers.
I use single ended amps with unbypassed cathode resistors in the output stage.
This only works with active crossovers, of course, and no passive components
between amps and drivers.
  Reply With Quote
Old 6th June 2007, 06:41 PM   #968
diyAudio Member
 
Lynn Olson's Avatar
 
Join Date: Jul 2004
Location: Northern Colorado
Quote:
Originally posted by JohnL
Hey Lynn, I know you were looking at AMT's originally as a possiblity for a tweeter for this. I guess I'm the cheerleader for these things, so I thought you might want to see this. Evidently Beyma is in the process of releasing a pro audio AMT tweeter. It doesn't look like a dipole (Should I say it looks like it has a cup on the back), but it looks like a pretty potent unit. I hope their pricing is a little more favorable than Mundorf's.

Beyma TPL-150
Hmmm ... thanks for the link. Looks very interesting. So now we have three candidates - large-format compression drivers & low-diffraction horns, the twin-RAAL ribbons, and the new Beyma AMT driver. Somehow I doubt it has the insane pricing of the Mundorf. The comprehensive specs, including distortion and vertical directivity, are a welcome change.

Close reading of the specs makes it fairly evident that crossing below 1.5 kHz would be unwise - distortion is rapidly increasing, and the response is starting to go up and down, never a good sign in what should be a piston-response region. The dispersion specs shows that the vertical directivity narrowing starts above 3.5~3.8 kHz.

This prompts the thought that if you stacked two of these things, the upper one could be 1st-order lowpassed at 4 kHz, so there would two working in parallel in the 1.5~4 kHz region, and gradually transitioning to a single driver above that. With a declining magnitude, a 45~90 degree phase relationship between the upper driver and the lower driver, and tipping the upper driver backward by 10~20 degrees, that would prevent directivity nulls from getting too deep.

A series-shunt crossover might be interesting here. To implement the transition between one and two AMT (or ribbon) drivers, both are connected in series, with the upper driver bypassed by a capacitor selected to give a 4 kHz rolloff. This shunts the upper driver above 4 kHz, diverting its energy to the lower driver. The whole array has a 12~24 dB/octave crossover filter between 1.5~1.8 kHz.

(For a 3-driver array, the upper and lower drivers are connected in parallel, and both are shunted with a 3~4 kHz value capacitor. This group is connected in series with the center driver. As before, all drivers work together at the lowest frequencies, and narrow to one at the highest frequencies. You can see the similarity to the LF driver array.)

Most interesting. We have have some fun choices here, well outside the conventional wisdom on how to build loudspeakers.
  Reply With Quote
Old 6th June 2007, 07:04 PM   #969
mige0 is offline mige0  Austria
diyAudio Member
 
mige0's Avatar
 
Join Date: Jan 2005
Location: Austria, at a beautiful place right in the heart of the Alps.
Hi


Wow even 2 new interesting speakers
Tanks JohnL and thanks el`Ol !

BTW, the Beyma link does not work.

My heart is with the AMT's having some of the vivid attributes described by Lynn for the CD's / horn's.
Though I also have some nice memories for the Shackman DIY ELS as I managed to get the schematic of the electronic magazine straight that time. There was a severe fault in the PSU bootstrapping circuit for the supply and polarisation voltage that affected the whole transformerless (transisor-) amp.

I also tried this ESL with a horn but I think I didn't know enough about horn theory to make it work, roughly two decades ago.

The max-SPL plot of the Sonus Novason ESL

http://www.sonus.de/download/pdf/dat...9a75128b83408e

is something that was published by pro-manufacturers like EV regularly many years ago but unfortunately became unpopular in the days where simulation software is assessable for anyone .
110 dB / 4m down at 200 Hz is really impressive. Is this ESL really available? The plots are measurements of a prototype as far as I can see.


Greetings
Michael
  Reply With Quote
Old 6th June 2007, 07:06 PM   #970
Joey B is offline Joey B  United States
diyAudio Member
 
Joey B's Avatar
 
Join Date: Dec 2005
Location: Des Moines , Iowa
Hi Lynn

The Duelund resistors are designed for crossovers in that as current increases the extra heat generated does not raise the resistance of the resistor thus preserving dynamics .

They come at quite a price , $20.00usd last time I looked . They are used in Peak Consult and a few other highend speakers . Available at Parts Connexion . Maybe this would be an answer to a more neutral but still dynamic speaker ???

Joey B
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 12:24 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2