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Do Treble Units need to burn-in?

Brian

Brian

Eating fat, staying slim
I'm not convinced generally about components requiring a run-in period but I think it does apply to loudspeakers. However, I'm referring there to bass and midrange drivers, I'm not sure about treble units, I suspect they shouldn't require any run-in period.

I've recently changed the treble units in my loudspeakers, modifying the crossover according to the kit design for that unit, but the sound is far too bright. I've been farting around with resistors and such but I'm not making much progress.

The kit design is from the 90's but these are brand new treble units.
Q. Could the parameters have changed and so the crossover need modification, or might it be possible they need to run-in?

Any other ideas? If I have to resort to changing the speakers I'll probably go back to something from the likes of Linn, as I've used their speakers before and find I get on with them quite well.
 
Well, tweeters also have a roll-surround so there is no reason why they shouldn't run-in the same way that a mid or bass driver does. In fact, a tweeter physically moves a lot less than other moving coil drive units, so they may well take longer to run-in.
 
Yers, but IME the sensitivity increases with use, which wouldn't be helpful in your situation.

If resistors aren't doing it, could be that the crossover point is wrong, and there's too much overlap.
 
Probably, very slightly, but to a degree way below the point where you should be concerned about the effect.

IMO.
 
In my experience, (having built a few diy speakers myself), tweeters tend to be bright when new and smooth out during the burn-in period.
 
Brian said:
Here is the crossover design, I found the pic in google docs.

Any suggestions? I've so far increased the value of the series resistor on the treble unit to 12R and it's still too much 'in yer face'.
Click to expand...

Might not just be a case of padding the tweeter. Other things affect the balance of the speaker. A touch less damping internally to the cabinet can "bring up" the mid bass overall and help the tweeter be less "obvious". Also either raising the cross-over point or order of the cross over on the tweeter section of the cross over can help with integration and balance through the cross over region. Especially if the excess you're hearing is in the "shouty" rather than "spitty/tizzy" range, (i.e. upper mids/lower treble rather than mid/upper treble).

Also in answer to your other question. yes it's quite likely that the tweeter manufacturer has tweaked the drive units parameters. Especially if the original units design dates from the 90's.
 
Thanks to everyone for the replies so far.

James said:
What's the tweeter (new) and original specification?
Click to expand...

James,

Here is a link to the unit I bought Audax TW025M1

There is a link on the page to a fuzzy looking image of what looks like the orirginal spec published by Audax. A better pic from the Audax site is here

I'm using it to replace the HD3P.

The speakers were designed by HIFI World, first with the TW025M1 and then later with the HD3P. I've been using mine with the HD3P for 8 years now but have had a few problems with one of them losing pressure, so the plan is/was to revert to the original design because overall I really like these speakers.

Brian
 
Have you looked at the mid filter to see whether changes have been made to accommodate the HD3P change relative to the one specified for the TW025M1?

James
 
Don't know about the M1 but the TW025A1 is a non--fero tweeter, with a undamped resonant peak just above 1K, which could possibly be causing problems with your XO.

Have you read Peter Comeau's article in HFW re replacing the HD3P? He used a Seas Excel substitute, but there might still be something useful there.
 
That tweeter is 92dB output [datasheet]. The bass is about 5 dB down [91dB datasheet] by the time you add a xover and move the box away from walls. After the 3.3 ohm I would put a 12 ohm resistor across [parallel] the treble driver. This gives you the same 7 ohm impedance as the raw driver but loses about 5 dB treble, which is what they wanted, I suspect, in the original design.

7\\12 = 4.42

4.42+3.3 = 7.72 ohms

20 x log 4.42/7.72

= -4.8dB
 
James said:
Have you looked at the mid filter to see whether changes have been made to accommodate the HD3P change relative to the one specified for the TW025M1?

James
Click to expand...
There were two different KLS3 designs using the HD3P and one design using the TW025M1. There were differences but I have them all built up.

With the TW025M1 I'm using the design I showed earlier so I can confirm it's as it's supposed to be.

I'm wondering if it's my ears given the quality of the HD3P, but my wife has also stopped using the hifi and is right now using an ipod with headphones.
 
demotivated said:
That tweeter is 92dB output [datasheet]. The bass is about 5 dB down [91dB datasheet] by the time you add a xover and move the box away from walls. After the 3.3 ohm I would put a 12 ohm resistor across [parallel] the treble driver. This gives you the same 7 ohm impedance as the raw driver but loses about 5 dB treble, which is what they wanted, I suspect, in the original design.

7\\12 = 4.42

4.42+3.3 = 7.72 ohms

20 x log 4.42/7.72

= -4.8dB
Click to expand...
Thanks. I'll give that a whirl. I have a 12R.

Will report back tomorrow.
 
I would guess the mid output is too high as well, but try one thing at a time. You would probably be better with designing a x-over from scratch, but since you have a lot of xpensive parts already, it might well be OK.
 
demotivated said:
That tweeter is 92dB output [datasheet]. The bass is about 5 dB down [91dB datasheet] by the time you add a xover and move the box away from walls. After the 3.3 ohm I would put a 12 ohm resistor across [parallel] the treble driver. This gives you the same 7 ohm impedance as the raw driver but loses about 5 dB treble, which is what they wanted, I suspect, in the original design.

7\\12 = 4.42

4.42+3.3 = 7.72 ohms

20 x log 4.42/7.72

= -4.8dB
Click to expand...
Hi

I slotted the 12R into the circuit about an hour ago and I can't keep the daft grin off my face. :)

First impression is .... much, much better. Not harsh at all, the bass has returned. My wife and son are listening right now and we're all relieved by what we're hearing.

I'll leave it as is for a couple of weeks now and go through my music as normal to see how it works out over time but I'm very optimistic that you've fixed my speakers.

Thanks very much to everybody who replied, I appreciate it a lot.

Brian
 
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