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Smaller Advent Tweeter Replacement


Guest Robert M

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Guest Robert M

I really liked the sound of the Smaller Advents when I first hooked them up, particularly the low end. But the more I listened to them, the harsher the tweeter became until it was all I could hear and I then put them away. Well, I finally got around to dropping in a substitute for the tweeter and the results are very good. The substitute in question is the Tang Band 852SF, a small 2" full ranger. The specifications for it are at the Tang Band site. Note that the curves provided on the www.partsexpress.com site, where I obtained the units, are for the SC model, the SF model has improved performance above 10KHz (no peak in the 10-15KHz range). This full ranger has a 2" paper cone and dust cap attached to the voice coil. It is also is a 4 ohm unit like the SA tweeter. It goes much lower than the crossover point (1800 Hz?) and has a decent looking response curve up to 15KHz or so. I found its output to be a bit shy of the SA's, but not by much. I installed them on a replacement face plate and enclosed the rear of the speaker to isolate it, otherwise it would surely be damaged.

The harshness of the SA may very well be due to a peak in the vicinity of 13KHz, as reported in the recent Stereophile article on the SA and shown on various frequency response curves that float around regarding the SA. The SF model of this full ranger appears to have a trough in that area and I can say that these full rangers are not bitterly harsh at the high end (as I perceive the SA tweeter to be), but neither are they silky smooth, in fact they are a bit "shouty" and match very well in timbre with the original SA tweeter. So much so, that I was able to listen for a few hours with only one of the full rangers installed. I'm waiting on some foam for my second pair of Smaller Advents to due a proper "A-B" comparison, but a single pair evaluation reveals the full ranger to be a bit more detailed and also more accurate, I noticed this in particular on some female vocals which sounded more natural with the TB unit than with the SA. I know not everyone perceives these orignal tweeters to be harsh, but if you do or have a set with bad tweeters, this sub is worth a try. In addition, these speakers are now available at a bargain price of $5.25 shipped (yes, you are reading this right, the drivers are $13 each w/o shipping at PE) from an ebay seller (no relationship) named worm-o. The auction may have ended by the time you read this, do a search on completed items, he claimed to have many left.

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With regard to your second attached photo, the block of wood you used to mount the new tweeter looks pretty thick. My guess, around 3/4 inch?

If so, you have altered the time alignment (group delay) characteristics of the speaker by shifting the tweeter's VC even further away from the woofer's. Thus the tweeter's output will be slightly further ahead of the woofer's than it originally was.

If you can, try tilting the speaker back so the center of the tweeter's VC is vertically aligned somewhat with the woofer's and give a listen. This will be particularly advantageous if your speakers are on the floor and you sit on a chair or couch.

Let us know what you find.

Regards,

It's all about the music

Carl

Carl's Custom Loudspeakers

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Guest Robert M

>With regard to your second attached photo, the block of wood

>you used to mount the new tweeter looks pretty thick. My

>guess, around 3/4 inch?

>If so, you have altered the time alignment (group delay)

>characteristics of the speaker by shifting the tweeter's VC

>even further away from the woofer's. Thus the tweeter's output

>will be slightly further ahead of the woofer's than it

>originally was.

>If you can, try tilting the speaker back so the center of the

>tweeter's VC is vertically aligned somewhat with the woofer's

>and give a listen. This will be particularly advantageous if

>your speakers are on the floor and you sit on a chair or

>couch.

>Let us know what you find.

>Regards,

>

>It's all about the music

>

>Carl

>Carl's Custom Loudspeakers

You are correct, the backplate is quite thick, it is all I had around at the time. If I were to do it with more care, I would have gone for 3/8" plywood or OSB which would have allowed placement of the grilles, as the tweeter sticks out too much with the way I have it. Fact is, I have a moldy smelling pair of SA I picked up curbside with no front grilles and missing tweeters, that pair got the full rangers, I'll probably keep them in there. Hell, they were only $11 for the pair!

When I initially installed the backplate, I did not provide a gasket, it was wood on wood, but still quite tight, or so I thought. When I fired the unit it up, I got a puff of sawdust from the backplate, there is quite a bit of pressure buildup within the speaker during operation ("acoustic suspension"). This surely would have destroyed the tweeter had it not been perfectly sealed, this is key.

I see the seller has these units listed again, if anyone wants to give them a try. I am guessing the 3" Tang Band full rangers that got alot of press lately would also work well, but I was unsure as to what to do about the fact that they were 8 ohm and I think they would also look a bit out of place, space age look and all.

The bass in the Smaller Advent is excellent, very tight and accurate. This is the best quality of this classic speaker.

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"Specifications: Power Handling: 10 watts RMS/20 watts max "

I'd be really cautious about that

Also--a newbie question: Is it really necessary to seal the backs of mids and tweeters??

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>"Specifications: Power Handling: 10 watts RMS/20 watts

>max "

>

>I'd be really cautious about that

>Also--a newbie question: Is it really necessary to seal the

>backs of mids and tweeters??

Hi Kent;

If by sealing you are referring to the driver flange to cabinet seal, yes.

Early drivers used a putty type sealer and later ones used stamped foam seals.

I've seen Advents with no woofer seals at all.

If there is an air leak around a driver, the bass may be boosted or weakened by the leak, depending on how large it is.

Either way a sealed cabinet performs best sealed, at least for operational use.

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Hi Vern

No, I was referring to this comment:

"I installed them on a replacement face plate and enclosed the rear of the speaker to isolate it, otherwise it would surely be damaged"

His photo shows a clear plastic box enclosing the back of the mid/tweet, to protect it from being torn up by the air pressure inside the sealed AS box. Didn't seem necessary to me.

Kent

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Guest Robert M

In both closed and ported boxes, the rear of midranges and tweeters must be protected. Most if not all drivers called tweeters are already sealed on the back, so it is not an issue. This particular driver is a "full ranger" and the cone is open to the rear. If you want to get a feel for the pressures generated, slip a 30Hz tone CD into your stereo and feel the flow going in and out of a ported enclosure. Don't try this at high volumes! That pressure will damage this driver and other drivers that are open from the rear.

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  • 4 months later...

Robert,

Nice work, please let us know how this sounds.

I considered the Tang Band W2-852SH 2" some time ago since it

is similar to the early Advent tweeter in many ways but I have

not tried it yet:

http://www.partsexpress.com/pe/showdetl.cf...tnumber=264-808

However, the unsmoothed response measured by PE looks a bit

rough above 13Khz, still it could have been partly a measurement

issue, and in fact the Advent tweeter has also has some

resonance in that range as was reported by Stereophile.

You are actually correct in mounting it forward since that is how

the LA/SA tweeter was mounted by design. This was necessary to

have the front of the tweeter flush with the opening in the grille,

to minimize diffraction.

These speakers were not time aligned and moving the tweeter a bit

forward or back simply tilts the optimum listening axis.

It would help to flush mount the driver in a piece of wood that meets

and just touches the grille when in place. You might also use some

felt around the tweeter if flush mounting is too much trouble.

You are also correct about the rear chamber, and in fact the best way

to do it is to reduce the chamber size until the Fc of the driver is

as close as possible to the LA/SA tweeter's value of about 650 Hz.

I believe that this driver is probably somewhat less efficient than

the original LA/SA tweeter and therefore may not be a perfect match.

However, it might be fine for those who agree that the tweeter level

was high in the original models.

Any more reports on the sound?

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