The Advent Loudspeaker

New Large Advent

NLA bullnose, factory stock as best I have determined, recently refoamed, with foam cabinet damping, on centerline axis at tweeter height, grille removed:


Nearfield low-frequency response and effect of grille:


Same data for unit #2, in which the factory foam has been removed and replaced with a lining of R-13 fiberglass. Lt. grey is unit #1 at "Normal" in all unit #2 measurements for comparison:


10° Polar Response:


Sinusoidal measurements comparing units #1 and #2 with grille, attenuation at Normal setting, and nearfield low-frequency response with the grilles removed:


Comments:

1) The grille levels a peaky high-frequency response somewhat, highest at 13.4 kHz. On-axis, the HF response rolls off steeply above 16 kHz.

2) Even with the grilles on, the "Decreased" attenuation setting provides the flattest on-axis response.

3) Toe-in is required for retention of limited HF response above 13.4 kHz.

4) As earlier found with OLA, the bass peaks at ~70 - 80 Hz

5) To the extent that the bass response is perceived as "boomy" with boundary reinforcement, this may be improved somewhat with fiberglass damping in lieu of the stock foam. Nearfield measurements reflect bass response in 2-Pi alignment, i.e., one boundary, wall or floor.

6) Bass response extends to ~35 Hz (-6 dB).

Here are my measurements of an OLA with original tweeter & woofer close miked. Note somewhat diminished highs compared to Zilch's horn mod.

Zilch said:

Here it is with New Advent woofer:

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That woofer with a paper dust cap rather than fabric looks to be a Jensen woofer used in the 5002/5012 not the NLA woofer. It has a significantly different motor and can be identified by the round magnet. All OLA and NLA woofers, and even some early Jensen 5002/12 systems have square magnets. It might be the replacement driver shown here which as I understand it is a clone of the Jensen, the question would be how good of a clone:
http://abtechservices.com/adventspeakers.html

I discuss the different woofer versions here:
http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2931&st=20

spkrdtr said:

Here are my measurements of an OLA with original tweeter & woofer close miked. Note somewhat diminished highs compared to Zilch's horn mod.

Click to expand...

Thanks, Carl!

I'm certainly pleased to see more objective data posting by fellow members here on AK for evaluation and comparison as there is precious little of this information available anywhere else.... ity:

Pete B said:

That woofer with a paper dust cap rather than fabric looks to be a Jensen woofer used in the 5002/5012 not the NLA woofer. It has a significantly different motor and can be identified by the round magnet. All OLA and NLA woofers, and even some early Jensen 5002/12 systems have square magnets.

Click to expand...

Thanks, Pete!

This pair of NLA woofers does indeed have round magnets.

This also explains the difference in opinion we were having in another thread regarding the porous character of large Advent dust caps.... :thmbsp:

It occurred to me that I meant to post the WT3 curves for my Advent woofs, but never did. Here they are, just in case they're any help. These are the real deal, with square magnets, stamped "1978", so they're definitely NLA's. Fs at around 19Hz.

I am finally getting some time to work on these again. I expect to wrap up my Advent rebuild this weekend and my new testing gear is scheduled to all have arrived by around next Tuesday. I should be posting test results soon. I note with interest Herr Bauhausler's recent comments regarding box stuffing vs boominess.

Both boxes are as identical as I can make them and you saw the woofer impedance sweeps above. Very close. I will do another set with the boxes sealed.

I have finally re-read all of what Dickason had to say about box stuffing, including the 10,000 graphs! I capitulate; R-19 fiberglass at 2 pounds per cubic foot is the way to go on a sealed box. Mine will be stuffed accordingly.

interlude at the building supply store
"I need some R-19, no facing. About 5 pounds." (Only need about 3.2 pounds; figured I'd get some extra.)
"You want WHAT? We don't sell that stuff by the f***ing POUND!"
"OK, I'll take the smallest quantity I can get. How much is that?"
"$34.95 plus tax."
"No, I mean, how much fiberglass is that?"
"Back your truck up over there. We'll load it for you. You can weigh it later."*
/interlude

I am mounting the crossovers externally to allow swappage (and eventual biamping, possibly). I have built one of each crossover flavor. Will report results when available.

*6.25" thick, 2 ft wide, 8 ft long, 8 pieces, in case you were interested. It's a lot of fiberglass. No, I haven't weighed it.

3.5 mH Woofer Inductor

I was surprised to see the 3.5 mH value suggested here for the woofer circuit, which from my experience is too large for a second order network. I'd expect 1.5 to 2.5 to be about right depending on how much BSC is required. While 1.6 mH was used in the original and it did provide some BSC, it was first order and combined with the tweeter in such a way that there is too much output in the XO region so that whatever BSC was there became ineffective.

Pete B said:

I was surprised to see the 3.5 mH value suggested here for the woofer circuit, which from my experience is too large for a second order network. I'd expect 1.5 to 2.5 to be about right depending on how much BSC is required. While 1.6 mH was used in the original and it did provide some BSC, it was first order and combined with the tweeter in such a way that there is too much output in the XO region so that whatever BSC was there became ineffective.

Click to expand...

Me too, Pete. I set it up for freespace. Let's see what Paratima says; we may have to reduce that, ultimately....

OLA Remeasure:

Responding to an issue raised here:

http://www.audiokarma.org/forums/showthread.php?p=2524772#post2524772

Original Large Advent vertical polar measurement in 3" increments from tweeter axis at 44" mic distance, grill on, "Normal" attenuation setting:


Cab is upside-down, so (+) is toward the woofer.

3" = 3.9°, 6" = 7.77°

skywave-rider said:

So from your new measurements linked above, forward axis is low (toward woofer) w/ grille. But BmWr75 shows different. Will you do same vertical w/o grille? Is there a possibility of crossover variation between the two test subjects causing differences? Perhaps shifting forward axis of one or the other?

Click to expand...

I've reviewed the data for about an hour now, first satisfying myself that I'm getting the same results today as I did eight months ago. The answer is, "Yes," once it's understood that virtually all of the earlier work was done with the attenuation switch in the "Extended" position.

Look at the crossover data:

http://www.audiokarma.org/forums/showthread.php?p=1937162#post1937162

The notch we're observing is not in the crossover region, and I am thus far concluding that it's the interference cancellations between the tweeter and the grille opening which the design employs to smooth the HF response, the effectiveness of which apparently varies with the vertical listening angle. :yes:

Edit: Same, no grille. Grey is on-axis with grille from above:


It's starting to look like the acoustic crossover IS at 2 kHz, and your analysis is correct. I'll invert the tweeter and nail it tomorrow. If the drivers are running out of phase, that's the likely reason they don't image worth a whit. But even without the woofer running, there's a 20 dB hole in the tweeter response there, perhaps from the two elements (donut and dome) themselves interfering with each other at that frequency.


Re-edit: Same, with tweeter polarity inverted:


Finally, (I hope,) on-axis, "Normal" attenuation, with grille, tweeter polarity standard, Grey, and inverted, Cyan:


Nope, the crossover's at 1+ kHz, the tweeter has interference issues with itself, and the two combine with each other in a festival of phasing complexity.

Compare the crossover curve from eight months ago:


I'm callin' it "Nailed...."

skywave-rider said:

Yeah, from your rev polarity curve, 1k xx does appear to be the acoustic x-o point.

2k sure posed as it though.

Festival of phasing complexity indeed.

Click to expand...

Hey zilch, how did this turn out in comparison to the E-wave version? I caught the bits above w/ reference to the bass response. How do they do in terms of imaging and breadth of "sweet spot"? I'm gathering ideas for a future build right now...when I have the time and expendable income. Did you ever come to a conclusion re: the woofer's inductor? In my new room, I'll have the room to have them out in free space (approx. 5' from the sides walls, and 8' from the front, on 15" stands), so I was naturally interested in your posting above. Any suggestions?

If you're going to use them in freespace, use the larger inductor and cap.

Normally, against the wall, the standard E'Wave filter.

EconoWaves image well, and you can also do the toe-in for enhanced image rendition zone thing with them.... :thmbsp:

Paratima said:

interlude at the building supply store
"I need some R-19, no facing. About 5 pounds." (Only need about 3.2 pounds; figured I'd get some extra.)
"You want WHAT? We don't sell that stuff by the f***ing POUND!"
"OK, I'll take the smallest quantity I can get. How much is that?"
"$34.95 plus tax."
"No, I mean, how much fiberglass is that?"
"Back your truck up over there. We'll load it for you. You can weigh it later."*
/interlude

.

Click to expand...

:lmao::thmbsp:

grateful said:

For all you folks that hate the Advent, What speakers sound good to you?

Click to expand...

I don't hate advents, but I prefer Kef or MartinLogan.

I had the original large Advents, but preferred the Dynaco A25's

I am really starting to appreciate the research that you do Zilch.:yes:

OLA Polars:

All measurements with attenuation switch set to "Extended."

Horizontal Inboard:


Horizontal Outboard:


Vertical Up:


Vertical Down:


Compare to The Smaller Advent here:

http://www.audiokarma.org/forums/showthread.php?p=2958290#post2958290

http://www.audiokarma.org/forums/showthread.php?p=2960402#post2960402

No wonder I don't like these things. Though the measurements only backup what I hear with my ears.

I don't think you know how to interpet the curve Damage. What you are seeing illustrates excellent performance. Speaker response curves look nothing like amplifiers.

lumpy said:

I don't think you know how to interpet the curve Damage. What you are seeing illustrates excellent performance. Speaker response curves look nothing like amplifiers.

Click to expand...

Seems they're rather more excellent, uhmmm, "amended:"


http://www.audiokarma.org/forums/showthread.php?p=2434268#post2434268

So just out of curiosity, which set of curves is most likely to be the Advents I decided not to buy back in the 70's...?