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What do you think of this tweeter response?

While clearing out a cupboard I stumbled upon a couple of Goodmans tweeters I completely forgot I had! One is a blue-label DT3, the other just has a narrow white paper sticker on the back with a hand-written serial number beginning with 9xxxxxxxx. From the front it looks just like a DT3 or DT4.

I took the opportunity to measure them on the weekend. The measurements were made in free-space (tweeters plonked on top of a piece of acoustic foam on the floor and pointing straight up towards the ceiling), the mic was positioned 1m above and with a horizontal offset of about 0.4m, because I have found that some tweeters (e.g. Audax TW025A0) exhibit peculiar responses when measured perfectly on-axis if they aren't mounted on a baffle.

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Tweeter 9xxxxx clearly exhibits the same response anomaly found in two of the three pairs of Achromats measured in post #1. So too does the DT3, but to a much lesser extent. This weekend I'll attempt to dismantle the 9xxxxx unit and see if it reveals anything.

During my clear out I also discovered a pair of Philips AD 0160 / T8 tweeters, which Goodmans used in several of their models, including entry level offerings such as the Minister, Havant, etc, as well as their better respected ones, such as the Double Maxim, which is a cracking little speaker IMO. I'm a bit confused about the chronology, as I have seen the aforementioned models fitted with both the Philips AD 0160 and Goodmans own dome tweeter (DT2/DT3/DT4) so I'm not sure if they started off with the Philips then moved to their own tweeter, or if they were using both simultaneously to keep up with demand. Do you know about this, Adam (@Beobloke) ?

Troels Gravesen has some interesting comments about the AD 0160. The sample he measured exhibits quite an uneven and upward-tilting response, which is interesting because the pair I measured are surprisingly flat and don't tilt upwards until they get to beyond 10kHz, and even then it's only a 2dB-3dB lift. Some of this difference above 10kHz is probably explained by my measuring off-axis, but as for the response below 10kHz I can only assume that's being caused by baffle diffraction. I'd speculate the best way to mount this tweeter is from the rear (ooh, err, Missus!), so that the baffle is flush with the dome with no gapping).

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I recently took a punt on another pair of Goodmans tweeters. They were both advertised as '571071A' but one has a blue DT3 label on the back and the other has no label, just some faintly printed digits that bear no resemblance to '571071A'. Viewed from the front they are identical in appearance.

In terms of measurements, the unlabelled unit has an excellent off-axis response, probably the best I've measured from a Goodmans Dome Radiator. The DT3 labelled unit is horrendous by comparison and resembles the Himalayas! I think this is a prime candidate for disassembly as I've nothing to lose by damaging it further in the process!

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Other than conjuring with your own observations I must say that's a very interesting cupboard of goodies you've got!
That's just the tip of the iceberg! I really do need to get my act together and start to move some more of my kit on, but when you're only left with good stuff it's very difficult to decide what to part with...

On the positive, it's nowhere near as bad as it was about 10 years ago, I think there was a point in time I had in excess of 40 pairs of speakers in the house! This was my Achromat stack in 2011 before I decided to part ways with the larger two models:
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Has anyone tried to disassemble one of these Goodmans tweeters? I've removed the three screws from the plastic faceplate but the faceplate isn't budging from the magnet assembly, even with a reasonable amount of force applied.

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Hi,

Just to ask if you could let me know the kit you used to test this and the general setup. All info gratefully received.

Ewen
 
Hi,

Just to ask if you could let me know the kit you used to test this and the general setup. All info gratefully received.

Ewen
Hi Ewen,

If this post is directed at me, the test equipment I use is as follows:
- miniDSP UMIK-1 USB microphone
- RoomEQWizard software

Learning how to use the software is the most complicated part, and you also have to be vary careful and consistent with your measurement conditions (mic and speaker placement etc) or it's easy to end up with variable and/or anomalous results. The more you do it, the more you'll get a feel for what works and what doesn't.

Hope this helps.
 


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