AR 3 toe in or not?

[tysontom]

4 hours ago, Carlspeak said:

BOOKSHELF VS FREE STANDING BASS BOOST

The in-ground test AR did is called a 2 pi (180 deg.) test by audio techs. The recorded FR shows roll off at the low end at about 50 hz which is about 10 hz above box resonance. My FR tests are done with the speaker on a stand, out away from walls in a room and thus those results are called 4 pi. (360 deg). I've generally found the roll off to start at a higher level, around 80 hz. with the 3a's I've restored. In fact, most speakers I've meas. this way have roll offs approx. twice cabinet resonance. Consequently, that bookshelf (i.e. flush in-wall mounting) 30 hz bass boost is certainly significant.

What I've written above is pretty common knowledge now-a-days (i.e. placing a speaker close to a wall extends bass response). Allison took advantage of this in many of his designs that employed smaller woofers (mostly 8 inches) to help boost the bass from those relatively smaller drivers.

So, kudos to those AR engineers and marketers for promoting bookshelf applications. Even their AR4x literature depicts them on a book shelf behind Judy Collins sitting at a desk, IIRC.

Hi Carl,

Thanks for your comments on the 180˚ solid-angle method of testing speakers.  Good message.

If you look closely at the AR woofer 2π frequency response, there is a slight rise (1.5 dB) just above resonance (43 Hz), but the response crosses the 0 dB point almost exactly at resonance, precisely as it is supposed to do.  You noted the "50 Hz" point, at which the overall response begins to fall off, but that is the point 1.5 dB above the 0 reference level.  Also, the woofer is almost exactly 12 dB down at 20 Hz, also exactly as it is supposed to do.  It has nothing to do with it being 10 Hz above box resonance. 

The Q  of 1.0 means that the speaker—when measured facing into a solid angle of 180˚—will  be flat down to the point of resonance with the 1.0-1.5 dB rise at a point just above resonance, and the AR woofer responds precisely and predictably in this manner, one of the great attributes of this remarkable woofer.  Also important is that there is no ringing or "overhang" in the response at resonance with the AR woofer with a Q of 1.0 but only a very very slight rise just above the resonance frequency (fc).

The mistake that is commonly made, that of measuring a woofer facing into a 360˚ solid angle (technically, suspending the speaker in the middle of a room away from all boundaries), means that a speaker has poorer coupling to the air and will begin to roll off in frequency at a point below the frequency of ultimate-radiation impedance (air-load resistance) , around 600-800 Hz for the 12-inch woofer in the AR-3a, down to resonance, but not below that point.  In other words, by increasing the solid angle from 180 to 360, the response is cut in half below the air-load resistance frequency.

Since no one listens to a speaker looking into 360˚, but rather at solid angles of 180˚, more or less, it is appropriate that the speaker's performance is quantified at 180˚.  Therefore, at 180˚, the AR woofer response is essentially flat down to resonance.  However, the room itself increases bass down at and below resonance through the effect of the so-called "room gain," so the effect is a slight increase in bass down to below 40 Hz, sometime "room gain" will increase bass down to 30 Hz and below without equalization.  When you pull the speaker out from the wall to measure it in a room, you are getting the solid-angle reinforcement of the floor, thus accounting for some increase in output from a purely 360˚ measurement.

1. An AR-3 measured at a solid angle of 360˚ in Harvard University's huge anechoic chamber.  Note the gradual decline in output below air-load resistance down to resonance.

 

By the way, mounting an AR-3a on a stand above the floor, back against the front wall, will give at least as flat a bass output (probably more room gain) than mounting in a bookshelf.  So the bookshelf-mounting of the speaker does not increase or enhance bass output, but it tends to eliminate the unevenness associated with the boundary "dip" described by Roy Allison.

—Tom Tyson

[Carlspeak]

Thanks Tom. Of course, everything you wrote about the in-ground FR test is true. We just look at the FR's differently. I see a roll off beginning at 50 hz in the AR test and typically saw 3a roll offs beginning at 80 hz in my living room.

[tysontom]

16 hours ago, Carlspeak said:

Thanks Tom. Of course, everything you wrote about the in-ground FR test is true. We just look at the FR's differently. I see a roll off beginning at 50 hz in the AR test and typically saw 3a roll offs beginning at 80 hz in my living room.

Thanks, Carl.  It is an academic discussion, but there are any number of explanations for the response rolling off earlier in your measurements, but it's mostly related to the radiation angle, bass reinforcement in the listening room, and method in which the speaker was tested.  The speaker's actual Q could be off somewhat; the compliance of the newly rebuilt woofer might have changed from the original, and so forth.  Also, If your speaker is pulled out into the room, as you explained, it is to be expected that the response will be attenuated sooner due to the larger radiation angle as I discussed in my message above showing the, so your tests are certainly valid when measured in that method.  Any direct-radiator speaker will actually begin to roll off at a frequency just above the resonance frequency, so when you see the AR-3a woofer beginning to roll off around 50 Hz, that is  correct even for the perfect, flush-with-the-ground 2π measurement technique.

It might be interesting -- if not a total pain in the tail -- for you to actually calibrate your test setup by measuring an AR woofer flush with the ground with the microphone at about 1 meter to see if you can replicate the standard measurements.  This way, you have quantified your measurement technique for a different position, and you will know that if your measurements are close to the original ones done.

--Tom  

[der]

Well, I appreciate all the great technical info and historical data.  I lived through those times and owned AR speakers and never heard any of it.  There's little doubt that communication is a lot easier now.  I read High Fidelity and Audio magazines back then - that was about it.

But, I did re-position my 3a's and after several days I must say I like the sound of music better.  Better bass, wider sound stage!  Didn't cost me a dime. Thanks guys!

der

[samberger0357]

2 hours ago, der said:

Well, I appreciate all the great technical info and historical data.  I lived through those times and owned AR speakers and never heard any of it.  There's little doubt that communication is a lot easier now.  I read High Fidelity and Audio magazines back then - that was about it.

But, I did re-position my 3a's and after several days I must say I like the sound of music better.  Better bass, wider sound stage!  Didn't cost me a dime. Thanks guys!

der

My feelings exactly. 

[Steve F]

 

-- Didn't cost me a dime.

-- My feelings exactly. 

The world-renowned acoustic consulting firm of Tyson/Steve F/Carlspeak, Esq. will be sending out its bill shortly. Nothing is free. 3% discount for invoices paid within 30 days. Remittance must be in U.S. funds. Thank you for your cooperation. We appreciate your business and look forward to serving you again.

Steve F.

[djcheung]

At the moment I have the Ar3a sitting on some speaker stands backed up against the back wall and firing straight out - no toe in.

I am connected them to the small Pioneer sa-508. They sound wonderful if you don't need to turn them up too loud. But then again, they are loud enough.I can really hear/feel the rumbles !

[der]

41 minutes ago, Steve F said:

 

-- Didn't cost me a dime.

-- My feelings exactly. 

The world-renowned acoustic consulting firm of Tyson/Steve F/Carlspeak, Esq. will be sending out its bill shortly. Nothing is free. 3% discount for invoices paid within 30 days. Remittance must be in U.S. funds. Thank you for your cooperation. We appreciate your business and look forward to serving you again.

Steve F.

Not a problem. You are reminded my pay terms are net never though.

der

[tysontom]

2 hours ago, djcheung said:

At the moment I have the Ar3a sitting on some speaker stands backed up against the back wall and firing straight out - no toe in.

I am connected them to the small Pioneer sa-508. They sound wonderful if you don't need to turn them up too loud. But then again, they are loud enough.I can really hear/feel the rumbles !

Now there's a setup!  I am amazed that sound actually comes out of the AR-3a system being driven by the Pioneer SA-508 (the American version was the 5800), as that amp was designed to produce 25 watts/ch into 8-ohm loads!  The 3a will tax any 25-watt amp, and the speaker's impedance runs solidly in the 4-ohm territory across the board!  Low in sensitivity, big in current-draw and hard on amps is the AR-3a's credo.  It is therefore a testimony to the Pioneer's excellent design that it even drives the AR-3a at all!

Otherwise, I'll bet the sound in good in that room!   (No additional charge for this message).

--Tom Tyson

[Carlspeak]

2 hours ago, tysontom said:

Now there's a setup!  I am amazed that sound actually comes out of the AR-3a system being driven by the Pioneer SA-508 (the American version was the 5800), as that amp was designed to produce 25 watts/ch into 8-ohm loads!  The 3a will tax any 25-watt amp, and the speaker's impedance runs solidly in the 4-ohm territory across the board!  Low in sensitivity, big in current-draw and hard on amps is the AR-3a's credo.  It is therefore a testimony to the Pioneer's excellent design that it even drives the AR-3a at all!

Otherwise, I'll bet the sound in good in that room!   (No additional charge for this message).

--Tom Tyson

Tax is an understatement unless for a pillow speaker. DJ said he doesn't turn the amp up too loud and really shouldn't because damage causing clipping from the amp could occur. The 3/4 in dome tweeters are highly sensitive to clipping. 

[der]

I toasted my midranges once when my AR amp blew up.  Not sure why it didn't affect the tweeters. Luckily, this was back when you could still buy factory replacements directly from AR cheap.

der

[djcheung]

I am actually surprised myself how this Pionerr is driving the 3a in such a way that is comparable t my Yamaha Z11.

When I say not too loud, I mean I have the volume dial only a quarter way up, but it produces really, really solid deep, deep bass that rattling picture frames.

i have double checked that I do not have a subwoofer connected to them!

 

 

[der]

I rarely rattle anything with my 3a.  Maybe I don't listen to the right kind of music? And, I have 150W per channel at my disposal.

der

[Liangshan Marsh]

 

 

Just place the speakers a little toe in for the video mic close up captures both speakers sound at once.

 

[frankmarsi]

Dude,,,,,dude,,,,,,,,,,DUDE!

This is almost an insult to any/every self respecting hi-fi fan!

How do they say?   Get with the program!

Please!

 

On another note in the last five or so years there seems to be this influx of 'newbee' peeps who don't have clue about speaker placement or anything

to be encouraging for the future of owning classic AR speakers.

Come-on now, let's call a spade a spade, a wheel barrel, a wheel barrel!

Is this the end of vintage AR speaker reality?

Yes these  are very old speakers, and yes the newer generations never heard of them and when they do they don't like them ,but give 'ole Eddie V and old Henry K. and Roy A. a break. At least understand these great men and learn some respect, please! 

 

Please get me a pill or a drink or a disconnect button from the 'NWO'. And they're all condoning one another, that's whats so sad.

The ship has sunk, we're all under water now! Probably because these new recruits never made it through 'boot'!

 

When you have heavy hitters on this thread like "T.T."  and "Carl the curator", and "steveF the wise

one", and genek the administrator, posts like this is such an affront to my last few hopes!

What am I to think? Even worse, I feel violated, assaulted. They tore my brain and heart out and danced all over it.

I won't even sign my initials at the bottom, what does it matter, with shit like this, I've already drowned!

[ra.ra]

There are plenty of "hi-fi fans" participating on this fine site who possess oodles of self-respect and buckets full of knowledge and experience, but there are not very many disrespectful know-it-alls tossing venemous spears from behind the bushes toward other participants. Let me be the first to say that I really abhor reading this type of smug, self-righteous rant. Are we really supposed to bow down and believe that there are only four current members (the"heavy hitters") that have anything of meaning to say within the boundaries of this forum?  

Inarticulate syntax, veiled insults, and crude language always fail to impress me in any forum of intelligent discussion. This member welcomes all "newbee peeps" to this (normally) friendly site, and if my reactive comments make this thread headed for the Kitchen or result in having me banned, I'll be happy to exit stage-left and still be proud of having this final word.

Signing off proudly, with initials,

RA

Administrators......intervene, please?

[samberger0357]

I took the post as sarcasm and wit. Perhaps I was wrong, but then I haven't a clue as to whom it's being pointed at. My experience on this forum is quite short, but closing in on 60 years of age and having done audio on a fairly serious level since I was 15, I guess I have some experience in the matter, at least enough not be classified as a "newbie". 

 

In any event, I've found this thread to be helpful and enlightening, and value being able to ask simple questions and get expert answers from the experts. Exactly what I'm after in an audio forum. 

[genek]

All I can say is...um, what?

[der]

6 hours ago, genek said:

All I can say is...um, what?

Is that an XA I see as your avatar?

der

[stupidhead]

I consider myself a newbie, no shame in it.

As for placement of the 3s above, sometimes there are space limitations in a room and you have to do what you have to do. Kudos to anybody that owns a set (or single) of these classics. It occurs to me that when original they were sold as singles (mono) and were quite enjoyable. Two side by each would just add a richer sound and I as a newbie would not see the above placement as blasphemy.

I echo Robert et al concern over the tone of the above entry.

[stan461]

Because of this thread, I actually placed my AR2AX pair against the front wall.
Need more time to decide which position is more satisfying.
However, I must say that the "front wall" positioning yields more and better bass .
In fact, the whole presentation is more "solid" and realistic in the sense that
it more convincingly recreates the hall or recording studio.

Unfortunately, I don't have a room with traditional bookshelves.
I'll have to get a little creative if I want to replicate that scenario more faithfully.

Back in the day when I was in my 20's, I frequented Harvey's, Stereo Exchange, Lafayette
and others which I can't recall at the moment.
All of these stores had the speakers up against the wall. Mostly on shelves.
So, in effect, they were creating a "bookshelf" environment.

At that time, I was paricularly interested in Advents (couldn't afford the AR3a).
Wow, they sounded so good! And of course, bought 'em.
Never got them to sound as good as I remember them in those listening rooms.
Could have been any number of factors/variables but maybe one of them might be
some of the speakers of that era were designed to be placed on a bookshelf.

Always thought of bookshelf as referring to size and not placement.

Anyway, good food for thought and plenty of incentive for experimentation.

 

[genek]

4 hours ago, der said:

Is that an XA I see as your avatar?

der

No, it's a TT, the original first version.

[der]

4 hours ago, genek said:

No, it's a TT, the original first version.

Thanks!  Two motor. One of my XA's is a converted 2 motor.

der

Oh, and by the way, I am definitely enjoying my new speaker placement!  Actually, I think I had them flush against the wall with no toe in back in the 1970's.  I must have lost the brain cells that contained that info.

[samberger0357]

Doing the same with my 3's. Hard to believe, but they have really opened up while firming up the bass. Very pleased.