Maplins close-out on AP100Z0

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#201
hi, just a quick question here, if I want to drop the sensitivity of the tweeter down so that it matches the mids, can I just string a resistor of the appropriate value in series with the driver?

What I want to do here is to drop the tweeter down four dB, so I figure, for a four ohm driver I will need a 2.34 (2.22) ohm resistor in series with the driver (as 20log(4/6.22) = -3.8dB), right?
 
#202
bigparsnip said:
hi, just a quick question here, if I want to drop the sensitivity of the tweeter down so that it matches the mids, can I just string a resistor of the appropriate value in series with the driver?

What I want to do here is to drop the tweeter down four dB, so I figure, for a four ohm driver I will need a 2.34 (2.22) ohm resistor in series with the driver (as 20log(4/6.22) = -3.8dB), right?
Click to expand...
Hey there!

Impressive that some people actually do the maths of this stuff, when there are plenty of online calculators and examples. I'm lazy, nuff said 😀

Anyway, that sounds about right to me, but I'd just like to add, the 'correct' tweeter attenuation might not be to your liking. Depending on many factors, you may prefer more or less top end coming through, so try a smaller one and a larger one too when listening. Sorry if I'm stating the obvious, I don't mean to patronise.

Your alternative is to use one in parallel too (the commonly used 'L-pad' circuit), but as some claim this dulls the sound why bother with an extra resistor? (Mine only has one in series)

Anyway, I just wanna say experiment, muck around, who cares what's 'right' or 'wrong' 😀
 
#203
bigparsnip said:
hi, just a quick question here, if I want to drop the sensitivity of the tweeter down so that it matches the mids, can I just string a resistor of the appropriate value in series with the driver?

What I want to do here is to drop the tweeter down four dB, so I figure, for a four ohm driver I will need a 2.34 (2.22) ohm resistor in series with the driver (as 20log(4/6.22) = -3.8dB), right?
Click to expand...

If the tweeter does not have a Fs impedance rise yes.

If it does a series / parallel resistor combination is better.

🙂 sreten.
 
#204
right, well in that case I'll get a few in and give it a bash next week (I may even see if i can find another cardboard box 😀 ) with the crossover components I ordered today (only first order at about 3200Hz, but I thought I would start simple for my first try, and I can alwas change it if I don't like the sound)
 
#206
Well I've now done 50 hours break-in for all drivers, and they still need more. The second batch were run-in at mechanical excursion (or what I thought to be) and the first batch was run-in at a more conservative level (xmax-ish). There is a measured difference between batches, so I will run them all in some more (at mechanical exc.), something I was afraid to do considering the 30W rating.

This just shows me how much run-in time speakers need (or maybe just these ones). I think it would take a long time to completely break these drivers in with music content.

Seems that your measurements could be ok pinkmouse, depending on how long and how hard you ran these little things in for.
 

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#209
SimontY said:
Highly cool! 😎 😎
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I agree!

I remember some1 doing a similar thing with an XLS driver as you can imagine lots of movement.

I wouldnt worry to much about exceeding the power ratings with low frequency sine waves. Typicallly you will require less then 1 watt at about 20-30hz to exceed xmax in free air.
 
#210
These are the final measured specs after 70 hours break-in.

Fs: 79.6
Vas: 2.85
Qms: 2.63
Qes: 0.81
Qts: 0.62
Le: 0.16

The parameters are acceptably in spec (within 30% of Audax specs except for Vas), but more importantly they are quite consistent with each other. Nevertheless, accept them at your own risk. :dodgy:

The specs are derived from the average over six drivers. For those interested, I've put the individual driver measurements from each break-in period on my site. This was a little project in itself, and quite interesting to see how parameters change.

Time to start designing...
 
#214
I think its better to do at low frequency. The aim is to stretch out and settle the suspension and surround and this is done with big movements. The lower the frequency used, the less power required and more movement you get. I'd prefer not to run the drivers at a higher frequency for long periods at high levels of excursion, although I guess they would run in quicker.

Look forward to your results PM.
 
#215
Vikash

I would be interested in your thoughts as to what tweeters you are considering.

I have pretty much given up trying to obtain the "F1" from Audax.

And thank-you for carrying out the tests and sharing your findings with us all.

I really like the look and feel of your website by the way, very nice....

m
 
#216
I have no idea what tweeter I'm going to use. My criteria is simply that it should keep in line with the awesome saving on the AP100Z0 (so cheep then 😀 ). I was considering the TM025F1 too, but I can only find 1 in the three branches I've tried.

After speaking with someone at the local Maplins, he said that they're phasing out all the Audax line (which we aleady know) and they will be replaced with Macs Power (or somthing like that). No, I haven't heard of them either, and was informed they will be of lesser class.

Also, they apparently know when and what drivers are on close-out special but he can't divulge that information to the public.

Anyway, I've set myself a max budget of £15 per tweeter, so if anyone has any suggestions...
 
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