brianw
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Posts posted by brianw
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Interesting read about xover's and various capacitors.
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HI David
Thanks for the explanation. I realize in general what the circuit does, I was just curious what would happen if the 6 ohm resistor is removed. I suspect it would change the response curve and output level. I am curious so presently playing with xSim to see what it actually does to the curve and the output. Just thought maybe someone else might have a idea already.
Thanks in advance
Brian
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After all the xover rebuilds and other refurbishing both of my AR 9 sets are spectacular.
Not being someone who understands xover design, what roll does the UMR 6 ohm 22watt capacitor perform ? Is it to lower the output of the UMR ?
Thanks in advance.
Brian
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15 hours ago, Pete B said:
My opinion is that if a product was originally designed with a .75" tweeter you should
stick to it when trying to stay as close as possible so that leaves you with the SB. I just
measured my AR-9 tweeter and there is an issue, I'll post the results later tonight or ASAP.
What type of shop are you going to use?
Have you noticed that ring radiators, even .75" have inferior dispersion as compared to
normal dome tweeters?
The AR-9 tweeter has a very high Fc which is part of the electro-acoustical response and,
don't laugh, but this tweeter with a 10 ohm resistor across it would probably work fine:
They would probably fail, even with the high crossover point, if you run over 200W/ch into
them at party levels. The SB is better but the Fc is way off and will require crossover mods
or compensation.
This is the 3D printer that I have on order: http://www.classicspeakerpages.net/IP.Board/index.php?/topic/10492-3d-printer-for-mods/
I would agree that sticking to same dome type would be good although although the materials and characteristics of the dome will still cause many differences. The shop is is a metal fabricator, the bonus is they have a CNC machine, so I will have to supply and original plate for them to scan, should be interesting, found them through a friend who owns a custom granite kitchen counter top business.
I did notice the of axis graphs and my first choice was the SB Accoustics with the XT 25 second. I have never actually seen specs on the original AR 9 tweeter so have kind of been doing some educated guessing.
I wont be running any party levels so I should be good with lower power units. My decibel meter say we average 70 to 80 db listen levels. We may have the odd evening and run it up a bit but to us it is loud. We only tested the AR 9's once to see what hey could do and yes concert levels they can hit, we also were wearing some musician earplugs when we tested which knock off a lot of decibels and protect our ears. I have always noticed with good audio you don't realize how loud it is until you try to talk to someone.
Will be interested to see what the issue is when you tested the AR 9 tweeter.
And thanks for the 3D printer info.
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On 1/29/2019 at 4:10 PM, Pete B said:
@brianw I find it odd that you point out that there are modern tweeters with very flat
response such as this .75" tweeter from SB Acoustics - note the very flat response:
And you're told that will change the sound of an AR speaker, rather you are told to use
a tweeter that _looks_ exactly like an AR .75" tweeter but does not perform electro-acoustically
anything like the AR original .75" tweeters.
Drink the coolaid!
HI Pete
Point well taken, coolaid swallowed. So for my own curiosity I have come down to a few possible tweeters I would like to experiment with on a sound level even though specs make require adjustment to the upper frequency cross over. I have also sourced a fabricator locally who can produce an adapter plate quite reasonably to prevent making any alterations to the actual cabinets.
Should be a good experiment for myself to sit a modifed AR 9 next to one of my original AR 9's to do an A/B comparison. Before I do any ordering of tweeters I thought it best to get your professional opinions, like and dislikes.
Also I am interested in the 3D printer that you have ordered Pete, that would make sense for prototyping and playing with alternate drivers, I may to some quick research and follow in your footsteps.So so far these are the tweeters I am thinking of including the SB Acoustics SB19ST-C000-4 you mentioned.
https://www.madisoundspeakerstore.com/soft-dome-tweeters-sb-acoustics/sb-acoustics-sb19st-c000-4-3/4-dome-tweeter-4-ohms/
SB Acoustics SB29RDC-C000-4 (4 ohm )
https://www.madisoundspeakerstore.com/ring-radiator-tweeters/sb-acoustics-sb29rdc-c000-4-ring-dome-tweeter/
Peerless XT25TG30 1" Dual Ring Radiator (4ohm)
https://www.parts-express.com/peerless-by-tymphany-xt25tg30-04-1-dual-ring-radiator-tweeter--264-1016
SEAS Prestige 25TFFC (H0519) Textile Dome Tweeter ( 6 ohm )
https://www.madisoundspeakerstore.com/soft-dome-tweeters-seas/seas-prestige-25tffc-h0519-textile-dome-tweeter/#tab-1Brian
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2 hours ago, RoyC said:
Not exactly...I'm saying the AR-11 tweeter can be made to sound like the AR-9 tweeter by modifying the faceplate. The AR-9 tweeter is the AR-11 tweeter with a recessed dome. The recessed dome, however, does not make it ideal for the AR-11. On the other hand, some people may actually prefer the AR-11 tweeter's greater dispersion when used for the AR-9.
Roy
HI RoyC
Would better dispersion not be a desirable thing, and would it not provide better clarity and range at different listening angles. Was there a particular reason for the recessed tweeter in the AR 9 ?
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1 hour ago, DavidR said:
So what if they extend out to 25 and 40kHz. I bet at 50 something you can't her above 15kHz if that high. I'm more than 10 years beyond you and I top out at 14kHz. More than that there just isn't much music above 15kHz anyway. And I'm with RoyC on 2 points: Midwest has a great drop in replacement and good luck with re-engineering the 9 for a new and different tweeter.
I suspect someone will be along soon who has repeated, successful experience in rebuilding/restoring the 9-series tweeter #200029.
Good point, from my younger days I probably cut off 14K or so as well, maybe its actually time for an ear test also. My concern was difficulty getting good components.
Brian
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2 hours ago, RoyC said:
AB Tech went out of business awhile ago and quickly re-opened as CM Tech by a former employee to sell remaining "new" inventory. All of the original AR parts were acquired by "Vintage_AR" (Larry Lagace) at that time. Apparently it is doing business as AB Tech again...same phone number. AB/CM Tech's AR replacement parts are sold to retailers like Simply Speakers. The drivers usually fit the cabinet holes, but original performance specs seldom match original.
If originality is the goal , there is currently nothing better than the excellent Midwest 3/4" tweeter as a replacement for the later 3/4" dome tweeters used in the AR-11/10pi and AR-9 series.
Plopping various drivers into an existing successful design seldom results in improvement, and is usually counterproductive. Essentially you are suggesting a thread on re-designing the AR-9. Good luck with that.
Anyway, this thread should be moved to the "Mods and Tweaks" section of the forum.
Roy
Hi Roy
Not suggesting redesigning the AR 9, I love my fully working pair, my first set. The second set is getting final touches, this third set is more of a problem so thought I would see if other drivers are out there that were very close in performance to the original AR 9 before trying to do a ferro fluid cleanup and replacement or find someone who can do a repair on the tweeters or UMR But from what you said, I think I will order a couple of the Mid West tweeter and keep an eye for some UMR in good shape.
Brian
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I know its been talked about on this forum before, and I have red a lot of discussions on tweeters and replacement tweeters. But I decided after acquiring another set of AR 9's that have some failed and aged or weak drivers it was time to resurrect this subject as the spare parts do get harder to find and when you do find originals you often have the problems associated with age and what you actually get when buying such an old component. I recently found my second pair of AR 9's had a very veiled sound, after swapping tweeters from a pair of AR 91 speakers I discovered it was a tweeter problem probably related to ferro fluid that has either hardened or gotten gummy after 40 years, i am told.
I am no Mr. sound engineer although I have been playing with sound since about the age of 12, ( now let's just say above 50 now), Have built a few speakers from scratch back around 22 using kef drivers, EV drivers, isophone etc., and just tinkered with crossovers. Have a electronics degree, ( but getting rusty), alng with a few other papers, built and sold several Technology companies except the last two that I currently own. So my passion I have finally had the time to play with, sound.
The last pair of AR 9's have now had new Mundorf Aluminum oil Capacitors, upgraded wiring and some minor refinishing. NOW the big question and hoping to get some solid suggestions from those with more experience in audio. I have read some old post, 2005, newer and older as to substitute drivers. So I have found two of the obvious tweeter replacements. ABtech, Simply speakers and Midwest Speakers.
ABtech
http://www.abtechservices.com/index.htmlThese guys were helpful and at least spoke to me. Also explained it was the same speaker that Simply Speakers sold.
Simply Speakers
https://www.simplyspeakers.com/acoustic-research-replacement-tweeter-12000840.htmlThe fellow I spoke to at simply was essentially rude and emailed they only have the info that was on the site. I phoned and got the remark "well it is an old speaker and that's what they have, so take it or leave it. They implied I would not notice any sound difference as the old speaker was probably so bad this would improve"
Midwest Speakers
https://www.midwestspeakerrepair.com/shop/home-audio/mw-audio-mt-4121-75-inch-dome-tweeter/The guys at Mid West and actually sent out a full spec sheet on their tweeter, something else no one else could seem to offer.
And then the question crossed my mind why not upgrade, Dayton Audio, Scanspeak, Seas, they all offer some amazing dome tweets that have extended range to 25k or 40k and UMR units that are cleaner and smoother, and why not tinker with improving if at all possible. So now the question of trying to figure out how we can improve on a couple or three drivers and get even a cleaner natural sound.So I am looking to the pro's, hobbyist and the experienced for ideas, discussions and suggestions. And why not it's a hobby that I totally enjoy and enjoy the results of..
Brian
My AR-9 Capacitor Recap/Upgrade Project
in Acoustic Research
Posted
Rtally
Thanks for the explanation, made total sense. As well the link to speaker makers journey! Great explanation. I believe somewhere in my past I recall a Zobel network in the rusty old brain. Again thank you.
Brian