Thanks and yes I need to do some more reading.i have 2 very old but good books at current.#1 Elements of Radio , #2 Audio Encyclopidia.The Variable Resistor is a 25ohm , 3watt , 20% tolerance.This is where I am getting lost in sretens discription : " One end of the track is the input, the wiper is connected to
the tweeter, the other end of the wiper connected to the other
terminal of the tweeter, this is the other input.
Maintain the phasing of the tweeter" I take it the left and right ends are the inputs and middle is the output.The middle should go to the + of the speaker.Either the left or right should be connected to the crossover + for the tweeter.The other one goes where?.Sretens says "the other end of the wiper connected to the other
terminal of the tweeter"Does he mean the (-) post of the tweeter?So that it would be connected with (-) ground lead from the crossover.?Sorry if I am confused...
the tweeter, the other end of the wiper connected to the other
terminal of the tweeter, this is the other input.
Maintain the phasing of the tweeter" I take it the left and right ends are the inputs and middle is the output.The middle should go to the + of the speaker.Either the left or right should be connected to the crossover + for the tweeter.The other one goes where?.Sretens says "the other end of the wiper connected to the other
terminal of the tweeter"Does he mean the (-) post of the tweeter?So that it would be connected with (-) ground lead from the crossover.?Sorry if I am confused...
see above edit 🙂
edit: Note that as the you turn the pot the series resistance will get bigger and the parallel resistance smaller, which won't necessarily vary in the same way as a purpose built variable L-PAD. I think 25 ohms is probably too high but Sreten is probably better able to advise on that.
edit: Note that as the you turn the pot the series resistance will get bigger and the parallel resistance smaller, which won't necessarily vary in the same way as a purpose built variable L-PAD. I think 25 ohms is probably too high but Sreten is probably better able to advise on that.
Thanks wintermute.That is what I was taking it as but was unsure.I will await sreten to reply to see if 25 ohms is to high.I am going to order a couple of L-pads from parts express tomorrow but it will take awhile for then to reach me.Thanks again for the patience and the help.
WM is correct that it only approximates an L-pad, and the best
value resistor depends on the amount of attenuation you using.
E.g. a 12R pot is perfect for 8 ohm with 4R in series and 8R in parallel.
However its not so good at lower attenuations, higher values are
better (16R) for more subtle reductions in level.
Wiring the other part of the pot in parallel is extremely beneficial
for tweeters with a strong impedance rise at fundamental resonance,
it can easily half the variation in impedance.
It always works better than the simple series connection
as long as the volume control resistance is not too low.
For an 8 ohm tweeter 25R is only a little high, I use 20R as thats
whats available.
A proper L-pad is a better solution but of course costs more money.
I'd only ever use one on a midrange for domestic use, for a
tweeter I think the 'volume control' would be fine.
WM diagram is correct. The only change you need to make is
connect the third terminal of the volume control to the other
terminal of the tweeter.
If the L-pads are already on order I tentatively suggest they should be used on the midrange.
But the pioneer midrange would need to be more efficient the Eminence bass unit for this to work.
🙂 sreten.
value resistor depends on the amount of attenuation you using.
E.g. a 12R pot is perfect for 8 ohm with 4R in series and 8R in parallel.
However its not so good at lower attenuations, higher values are
better (16R) for more subtle reductions in level.
Wiring the other part of the pot in parallel is extremely beneficial
for tweeters with a strong impedance rise at fundamental resonance,
it can easily half the variation in impedance.
It always works better than the simple series connection
as long as the volume control resistance is not too low.
For an 8 ohm tweeter 25R is only a little high, I use 20R as thats
whats available.
A proper L-pad is a better solution but of course costs more money.
I'd only ever use one on a midrange for domestic use, for a
tweeter I think the 'volume control' would be fine.
WM diagram is correct. The only change you need to make is
connect the third terminal of the volume control to the other
terminal of the tweeter.
If the L-pads are already on order I tentatively suggest they should be used on the midrange.
But the pioneer midrange would need to be more efficient the Eminence bass unit for this to work.
🙂 sreten.
Thanks to both of you for the lesson.I tried it the way sreten discribed and I was unhappy with the results.It seemed to lower the mid somehow and made the bass extremly bassy.it took the punch completly out of everything and muddled it.Maybe the variable resistor was just to high in ohms ...?anyway i took off the one to the (-) and am back to being happy with the sound and hope i do not damage anything this way until I get the L-PADS.Thanks again!
No worries. I find that by trying to help solve other peoples problems it usually results in me learning something too 🙂, and maybe someone else will have read the thread and learned something too!
I'd say that the ratio wasn't right and the impeadance seen by the crossover changed shifting the xover point higher (leaving a gap in the upper midrange).
Here is a scan from Vance Dickasons The Loudspeaker Design Cookbook 6th ed pp 142. It shows the effect of simply puting a resistor between the crossover and the driver (as you did). Notice how the attenuation is not uniform, and especially how the attenuation is minimal between about 3.5K and 5K.
Thought I'd show you that so you know what the real effect is )of course it depeds a lot on the individual drivers impeadance curve and the crossover but you get the idea).
When you use an lpad, the attenuation will be pretty much equal across the freq range. This is actually why I originally said you might prefer it with just the resistor, It's possible (although unlikely) that you were lucky and the resistor actually reshapes the response curve to be flatter but based on your description I'd say what I said first was much more likely (no way of knowing though without measuring equipment).
You shouldn't damage anything, especially if you don't crank the volume up too much.
edit: did you try turning the pot backwards and forwards once you had it wired up differenty? It would almost certainly have needed adjusting.
Regards,
Tony.
I'd say that the ratio wasn't right and the impeadance seen by the crossover changed shifting the xover point higher (leaving a gap in the upper midrange).
Here is a scan from Vance Dickasons The Loudspeaker Design Cookbook 6th ed pp 142. It shows the effect of simply puting a resistor between the crossover and the driver (as you did). Notice how the attenuation is not uniform, and especially how the attenuation is minimal between about 3.5K and 5K.
Thought I'd show you that so you know what the real effect is )of course it depeds a lot on the individual drivers impeadance curve and the crossover but you get the idea).
When you use an lpad, the attenuation will be pretty much equal across the freq range. This is actually why I originally said you might prefer it with just the resistor, It's possible (although unlikely) that you were lucky and the resistor actually reshapes the response curve to be flatter but based on your description I'd say what I said first was much more likely (no way of knowing though without measuring equipment).
You shouldn't damage anything, especially if you don't crank the volume up too much.
edit: did you try turning the pot backwards and forwards once you had it wired up differenty? It would almost certainly have needed adjusting.
Regards,
Tony.
Attachments
Well guys I can't argue with some-ones ears.
I don't understand how the sound could be made 'bassy'.
I'll just note that the real L-pad will have a lower parallel resistance
than the 25R circuit and will affect the sound even more than my
suggested connection.
Note that when adding the connection the 'volume control' must
be re-adjusted to a higher position for the same level cut.
If you simply add the connection it will sound worse.
Its always possible the crossover capacitor is too high in value
and the series resistance is helping this as well as reducing level.
(The part of the control above the arrow is in series
with the tweeter, the part below the arrow in parallel.)
🙂 sreten.
I don't understand how the sound could be made 'bassy'.
I'll just note that the real L-pad will have a lower parallel resistance
than the 25R circuit and will affect the sound even more than my
suggested connection.
Note that when adding the connection the 'volume control' must
be re-adjusted to a higher position for the same level cut.
If you simply add the connection it will sound worse.
Its always possible the crossover capacitor is too high in value
and the series resistance is helping this as well as reducing level.
(The part of the control above the arrow is in series
with the tweeter, the part below the arrow in parallel.)
🙂 sreten.
Attachments
sreten said:
Yeah I was a bit surprised too! the only thing I can think of is that the attenuation was quite high (around 6 or 7 db perhaps) in which case a proper L-pad would be around 4.5 ohms series 6.5 ohms parallel (assuming the site I linked to is calculating correctly), but with a 20 Ohm pot it would be 4.5 ohms series 20 ohms parallel!! Not sure what that would do to the impeadance the crossover would see but I'm sure it would mess with it!
It's funny there is a lot more going on here than I first thought. If I do a simple resistance calculation then I end up with about 7.5 ohms with the 4.5 in series and 20 Ohm in parallel, but 4.27 Ohms with the L-Pad values. I just looked at the LPAD formula and its a tad more complex than that 🙂
If you plug in values (on the lpad calculator) for 3db cut then the values are 2.34 series 19.39 parallel which is quite close to what you would get with the pot, so I guess there is a small range where the pot will be simillar but at higher attenuation levels I'm guessing it won't work so well.
It would be interesting to know the values on the pot both series and parallel, have you got a multimeter opus? only problem would be you'd 1) have to hook it up again, and 2) once you set it you'd have to disconect the tweeter to be able to measure the resistance on the two sides of the pot (center to each side).
Regards,
Tony.
opus007 said:
Well the above implies he's got ~ 12R in series with the tweeter.
Which will drop the crossover frequency over an octave.
(For a simple first order crossover)
I'm sure if my connection doesn't work well, the L-pad won't.
🙂 sreten.
sreten said:
Yep that makes sense. Not only was he attenuatiing the tweeter but also dropping the crossover point substantially, could be that the mid is crossed too high, and doing this fills it in nicely.
Without the attenuation and using a 1st order crossover the tweeter would still be filling in quite a bit where the mid was lacking, although the highs would be way too prominent. So if you are right then yeah the lpad will probably also sound lousy.
could be a case of inadvertantly fixing another problem in an unconventional manner.
Regards,
Tony.
So we agree I think,
(though I'm sure you meant mid crossed too low 😉,
I've also a suspicion the midrange sensitivity isn't up to much )
If the radio shack 25R volume control connected as I suggested
sounds lousy, then the Parts Express L-pad is not a good idea.
🙂 sreten.
(though I'm sure you meant mid crossed too low 😉,
I've also a suspicion the midrange sensitivity isn't up to much )
If the radio shack 25R volume control connected as I suggested
sounds lousy, then the Parts Express L-pad is not a good idea.
🙂 sreten.
Nah I meant too high, in the context of the mid may for instance only go up to say 3Khz and it is crossed at say 4Khz leaving a gap 🙂
Surely the xover wouldn't have the mid crossed at say 2Khz and the tweeter at 3Khz! but I guess you never know!!
Tony.
Surely the xover wouldn't have the mid crossed at say 2Khz and the tweeter at 3Khz! but I guess you never know!!
Tony.
I have the dubious honor of being able to say I have experience with such things as inappropriate crossover points 😉 But they do say you learn from mistakes!!!!
Tony.
Tony.
Looks like you guys have been busy while I have been at work.let me explain a little further what my observation was with the Variable Resistor set up the way you recommended.I would have to give it almost a half turn before I noticed any decrese in the tweeter.The mid...especcially voices seemed to decrese in volume to where voices sounded as though they where in the back ground.The bass from the woofer seemed stronger but that could of been due to the decrese in the tweeter and mid.I was able to get the specs on the tweeter and woofer and am going to guess the db of the mid is somewhere around 87db.The tweeter :3 5/8" Titanium Dome
Freq. Response 3.5k-25khz
94db@1w/1m
The woofer:
Following are all the T/S parameters for that unit.
Thiele/Small Parameters
01-SPEC 151420A
02-PART # 1540SF
05-RE OHMS 5.15 13-FS HZ 23.09
06-LE MH 1.20 14-MMS GMS 75.40
07-QM 11.66 15-CMS mm/N .6297
08-QE .580 16-RMS NS/M .9387
09-QT .550 17-VAS LTRS 648.55
10-XMAX MM 5.60 18-SD SCM 856.34
11-BL TM 9.90 19-EBP 40.1
12-EFF % 1.34 20-SPL dB 93.3
And here is the crossover specs:
Style 3-Way
Crossover Frequency 800 Hz & 5kHz
Slope Per Octave 12dB
Impedance 8 Ohms
Power Handling 150W RMS / 300W Peak
I hope this helps and I really appreciate any more help that can be given.i am thinking I may need to get a mid that will fit in with the tweeter and woofer?
Freq. Response 3.5k-25khz
94db@1w/1m
The woofer:
Following are all the T/S parameters for that unit.
Thiele/Small Parameters
01-SPEC 151420A
02-PART # 1540SF
05-RE OHMS 5.15 13-FS HZ 23.09
06-LE MH 1.20 14-MMS GMS 75.40
07-QM 11.66 15-CMS mm/N .6297
08-QE .580 16-RMS NS/M .9387
09-QT .550 17-VAS LTRS 648.55
10-XMAX MM 5.60 18-SD SCM 856.34
11-BL TM 9.90 19-EBP 40.1
12-EFF % 1.34 20-SPL dB 93.3
And here is the crossover specs:
Style 3-Way
Crossover Frequency 800 Hz & 5kHz
Slope Per Octave 12dB
Impedance 8 Ohms
Power Handling 150W RMS / 300W Peak
I hope this helps and I really appreciate any more help that can be given.i am thinking I may need to get a mid that will fit in with the tweeter and woofer?
Let me also say that all the drivers and crossovers I bought new from a local area Speaker Repair Shop who deals in repairs and sales of new drivers.In the past I bought a pair of Infinity Mids from them that they rated at 8ohms on there site but where actually 4ohms.I contacted Eminece and got the specs for the woofer.When i contacted the retailer they gave me conflicting info.They said it was 8ohms and 91db and Eminece says its 5.15ohm and 93.3db.I could not get the specs on the tweeter from the shop I bought it at as they say they do not sell it anymore but I was able to get what info i did from somewhere else.i am just mentioniing this because when i bought all these drivers I bought them under stupidity and was trusting the people I was dealing with to give me good quality ,matching drivers.What do you guys recommend>Thanks
Hi Opus,
One thing you seem to be confused about is that the impeadance (generally 8 ohms) and Re resistance are not the same thing. Impeadance takes into consideration the reactance and resistance of the voice coil whereas Re is purely the resistance. So I wouldn't worry too much about that.
I really think that if you are happy with the way the speakers sound with the series resistor just leave it that way! don't worry whether it's correct or not, if it sounds good what does it matter!
This is getting really complicated, and I suspect nothing short of a full crossover redesign would help, but I'm sure that is beyond my ability and yours. Crossover changes would be more sensible I think that changing drivers to match the crossovers (provided the existing drivers match reasonably well) But I say don't stress and enjoy your new better sounding speakers 🙂
If you have ordered the l-pads, try putting them in, it can't hurt, there seems to be something really strange going on, and my theory is not so valid with a second order crossover (which is what you have)...... Sreten and I are speculating on what the situation may be, there may be something we don't realise which is causing the strange behaviour!
Tony.
One thing you seem to be confused about is that the impeadance (generally 8 ohms) and Re resistance are not the same thing. Impeadance takes into consideration the reactance and resistance of the voice coil whereas Re is purely the resistance. So I wouldn't worry too much about that.
I really think that if you are happy with the way the speakers sound with the series resistor just leave it that way! don't worry whether it's correct or not, if it sounds good what does it matter!
This is getting really complicated, and I suspect nothing short of a full crossover redesign would help, but I'm sure that is beyond my ability and yours. Crossover changes would be more sensible I think that changing drivers to match the crossovers (provided the existing drivers match reasonably well) But I say don't stress and enjoy your new better sounding speakers 🙂
If you have ordered the l-pads, try putting them in, it can't hurt, there seems to be something really strange going on, and my theory is not so valid with a second order crossover (which is what you have)...... Sreten and I are speculating on what the situation may be, there may be something we don't realise which is causing the strange behaviour!
Tony.
Well you said with two connections you set it about half-way.
Correctly wired up the series/parallel connection will give more
tweeter attenuation for all settings compared to the series connection.
Correctly wired what you say is extremely unlikely, half a
turn will give give roughly - 11dB attenuation which is loads !
I suspect you inadvertently wired the pot in parallel only.
🙂 sreten.
I may of had it wired incorrectly(but I do not think so).Let me explain further as I did not make it clear on what I meant when I would turn it halfway.It sounded as though when I turned it a 1/4 of the way I noticed no difference than no turn at all(no attenuation) By turning it halfway is when I noticed the attenuation...but it almost completly attenuated the tweeter to where it was not audiable.And also it sounded as though the tweeter was attenuated to a certian degree (wired the way you described)with out applying any attenuation to it or in another words with out turning the the dial to decrees it.Actually this sounded ok this way. .I will say I did not give it a listen this way for long and maybe should of but thought something was wrong this way.My thinking was that since I hooked it up this way and had applied no attenuation and it was sounding that it was decreesed that something was wrong.Does this make sense?Would wiring it the described way automatically attenuate the tweeter to a certain degree?I am going to redo it the way you guys recommend this weekend when I have time to give it a good trial run.Thanks.
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