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Orange Tweeter Upgrades


Guest Namazu

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For a long time it has been virtually impossible to find a suitable replacement tweeter for the classic Large Advent Loudspeaker/ New Advent Loudspeaker due to the unusually low crossover frequencies of 1khz, and 1.5khz respectively.

That has changed!

Vifa/Peerless/Scan Speak now offer a couple of tweeters that can be crossed over below 1,000hz. Those companies have merged. Consequently the same tweeters are available from each but with differing part numbers (why do they do that?) I will offer up the Vifa #s.

First is the DX25TG05-04 with a fs=650hz

Second the XT25TG30-04 with a fs=530hz

Both are essentially flat to ~700hz and top end is beyond 20khz, the XT retails for a whopping $53 and change, the DX is about 1/2 that.

Can it be true? Do we finally have a tweeter that is a genuine replacement....even an upgrade, for our classic and beloved Orange fried egg? My mouth is watering as I type this.

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It is really tempting. I am working on a Bi-amp project with my trusty New Advents. No irreversible changes will be inflicted on this vintage pair, and a couple of small tweeter cabinets on top of the Walnut boxes would make phase corrections a simple matter.

Do I sound like I'm talking myself into it? Unless someone can report negatively on these tweeters I will probably go for it.}(

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Hi,

I'm always keeping an eye out for a replacement but one issue is that

it's not just a matter of matching Fs, the replacement must have enough displacement limited output to support the 1 kHz XO. Few 1" domes are designed or used down to 1 kHz. The original Advent tweeter was also more efficient than most, and it has a DC resistance of about 4 ohms and an Fs of 650 to 750 Hz, wouldn't hurt to go a bit higher for lower excursion, IMO.

Many designers like to push the XO frequency as low as possible and therefore pay a lot of attention to distortion in the 1 to 2 kHz range.

There are a few people with web sites offering measurements of driver distortion. Second and third harmonic distortion can be seen in green and blue here: Note the Scan Speak 9500 as a top performer and the XT or DX in comarision, note also the SEAS 27TDFC as a resonably priced top performer:

http://www.zaphaudio.com/tweetermishmash/hd.html

I recently noticed that the SEAS 27TFFC is higher than most in efficiency and this makes it a good choice for the Advent IMO, would have to investigate further.

It is also interesting to look at the distortion in the 3 to 10 kHz range since this is the main pass band of the tweeter.

I've been curious about the Vifa D26NC55 tweeter for some time, not for the Advents, look at the clean CSD plot for it:

http://www.zaphaudio.com/tweetermishmash/csd.html

More distortion tests:

http://206.13.113.199/ncdiyaudio/mark/Test...eter1_index.htm

http://206.13.113.199/ncdiyaudio/mark/whats_new.htm

Pete B.

> For a long time it has been virtually impossible to find a

>suitable replacement tweeter for the classic Large Advent

>Loudspeaker/ New Advent Loudspeaker due to the unusually low

>crossover frequencies of 1khz, and 1.5khz respectively.

> That has changed!

> Vifa/Peerless/Scan Speak now offer a couple of tweeters

>that can be crossed over below 1,000hz. Those companies have

>merged. Consequently the same tweeters are available from each

>but with differing part numbers (why do they do that?) I will

>offer up the Vifa #s.

> First is the DX25TG05-04 with a fs=650hz

> Second the XT25TG30-04 with a fs=530hz

>

> Both are essentially flat to ~700hz and top end is beyond

>20khz, the XT retails for a whopping $53 and change, the DX is

>about 1/2 that.

>

> Can it be true? Do we finally have a tweeter that is a

>genuine replacement....even an upgrade, for our classic and

>beloved Orange fried egg? My mouth is watering as I type

>this.

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I should probably mention that the authors of those sites suggest crossing the best of the drivers tested at a lowest freq of 1.2 kHz with a 4th order slope or better. There does not seem to be a simple solution with an off the shelf tweeter if the goal is to keep the original voicing and not change the crossover. The Advent had far too much output at 1 kHz IMO so there probably is a solution if we allow for some changes to improve the voicing.

I tend to use high crossover points to tweeters in my designs, 2 to 4 kHz because I'm aware of the distortion issues with dome tweeters. However, the better dome drivers might work "good enough" in the large Advent. I'd try the SEAS 27TFF or 27TDFC with a resistive shunt to match impedance.

I've been curious for many years to try a short horn, or waveguide loading with a top quality tweeter. Not a PA type compression horn but a low distortion design. This home brew waveguide is probably the best solution for the Advent when the goal is to retain the 1 kHz crossover, however a response shaping network would probably be required, the 3.3 uf that he uses is too small. Note the low distortion with the 3.3 uF:

http://www.zaphaudio.com/hornconversion.html

The Morel MDT-37 comes to mind as an off the shelf tweeter with a short horn but there is conflicting data about it, the older .pdf at Parts Express shows it as about -3 dB at 1kHz:

http://www.partsexpress.com/pdf/277-045s.pdf

Whereas the newer .pdf at Madisound shows it as -10 dB at 1 kHz:

http://www.madisound.com/pdf/mdt%2037.pdf

The difference could be measurement conditions or simply an error, it is worth looking into further as I think it would make a good substitute with a crossover shaping network if the older data is correct.

Pete B.

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So much brain food, so little time. This is going to take a while to digest, even after I dig out of the >12" of snow we got....are STILL getting here in NJ. I'll be back.

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>Has anyone performed these tests on the Advent tweeter?

Not that I know of, I've avoided detailed measurements because it is time consuming and I'd not planned to spend a lot of time on these old classics.

Pete B.

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A few comments about these distortions tests.

First I thank all who're good enough to share their data, and my comments reflect more on the developers of the test equipment and standards.

It is interesting that characteristics that we see as positive in linear measurements often hurt the non-linear or distortion measurements. This is not a trade-off rather it is a drawback of the measurement standards/methods.

Most see higher efficiency or voltage sensitivity, and extended low end response as positive characteristics, however, these indicate that for a given voltage drive level the driver will exhibit more excursion and therefore unfairly more distortion. Distortion tests are often performed at a given drive level, 2.83V, 5.6V, 1W, 5W, 10W etc. when a fair comparison would be to perform the test at equal SPL, even correcting for frequency response. Some test equipment will perform such tests, see for example Figures 9 and 10 which are equalized for constant sound pressure level in "Moving Coil Loudspeaker Topology as an Indicator of Linear Excursion Capability", by Mark R. Gander (JBL), JAES 1981 January/February.

Note that some of the tweeters with very flat response down to 1kHz have rising distortion at these frequencies, whereas some of the top rated tweeters are down 3dB-5dB or more at 1K giving them a significant advantage in reduced excursion at these frequencies. The Scan-Speak 9500 and SEAS 27TDFC are -5dB at 1k whereas the Vifa XT25

and Dayton RS28A4 are flat at 1k.

These issues must be considered when interpreting distortion data, still these tests are valuable to sort out the better drivers.

Pete B.

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