I'm putting together an H-frame for a 15 inch vintage woofer.
And I need to learn how to filter out the higher frequencies from getting to the woofer.
I have an 8" full range speaker already, and want to set this 15" woofer in its own H-frame. But I need to filter out the high frequencies.
I've read about installing a capacitor, but don't know what voltage and uF, or where to place it.
Thanks for any help.
And I need to learn how to filter out the higher frequencies from getting to the woofer.
I have an 8" full range speaker already, and want to set this 15" woofer in its own H-frame. But I need to filter out the high frequencies.
I've read about installing a capacitor, but don't know what voltage and uF, or where to place it.
Thanks for any help.
This is a basic crossover issue. I suggest you search "loudspeaker crossovers" and read up on it for a bit. An hour or so will answer your question. The simplest way is an inductor (coil) in series with the 15" driver. There will almost always be charts/tables giving the appropriate value for the impedance of the driver and the frequency you require.
We can't be really helpful until a bit more is known. (Btw the capacitor is usually used to prevent low frequencies from entering mid and higher frequency units.)
But having said that, someone will immediately post after me and point out that I am only referring "series" connected
networks and not parallel networks which of course is true.......more fun.
And we have not even suggested the "order" of the network......that needs exploring. For various reasons a 2nd order network would have some attractive feature for your application.
It does tend to get complicated fairly quickly.
And we should at least mention driver sensitivity or efficiency. If the 15" is more sensitive than the 8" unit you are not going to be very happy with the result.
There are solutions but like everything it involves cash.
Speaker building is NOT the "black art" that it looks like at first but it does require a bit of application on our part to master things.
Press, on it is a rewarding exercise.
Good luck.
Cheers Jonathan
We can't be really helpful until a bit more is known. (Btw the capacitor is usually used to prevent low frequencies from entering mid and higher frequency units.)
But having said that, someone will immediately post after me and point out that I am only referring "series" connected
networks and not parallel networks which of course is true.......more fun.
And we have not even suggested the "order" of the network......that needs exploring. For various reasons a 2nd order network would have some attractive feature for your application.
It does tend to get complicated fairly quickly.
And we should at least mention driver sensitivity or efficiency. If the 15" is more sensitive than the 8" unit you are not going to be very happy with the result.
There are solutions but like everything it involves cash.
Speaker building is NOT the "black art" that it looks like at first but it does require a bit of application on our part to master things.
Press, on it is a rewarding exercise.
Good luck.
Cheers Jonathan
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Thanks, Jonathan, for your help.
OK I got the capacitor backwards... typically blocks lows from getting to the tweeter.
These speakers all came out of an organ likely from the 60s with low wattage tube amps, and they have similar sensitivities... high sensitivities.
I was hoping to avoid crossovers altogether, save for the insertion of a cap somewhere. Once we get into coils and all, I "lose interest." I'm a "full range" guy now and really am not up to messing with xovers. Guess I was just wrong about trying this... unless there's a simple way to do this.
I basically want to see/hear if a 15" high sensitivity vintage alnico woofer can supply enough bass mounted in an H-frame cabinet. I'm running the 8" full ranger in an open baffle setup with a 12" polk subwoofer. I want to hear this 15" woofer in the H-frame and how it compares to the polk sub.
But as mentioned, building a xover is not on my to-do list.
OK I got the capacitor backwards... typically blocks lows from getting to the tweeter.
These speakers all came out of an organ likely from the 60s with low wattage tube amps, and they have similar sensitivities... high sensitivities.
I was hoping to avoid crossovers altogether, save for the insertion of a cap somewhere. Once we get into coils and all, I "lose interest." I'm a "full range" guy now and really am not up to messing with xovers. Guess I was just wrong about trying this... unless there's a simple way to do this.
I basically want to see/hear if a 15" high sensitivity vintage alnico woofer can supply enough bass mounted in an H-frame cabinet. I'm running the 8" full ranger in an open baffle setup with a 12" polk subwoofer. I want to hear this 15" woofer in the H-frame and how it compares to the polk sub.
But as mentioned, building a xover is not on my to-do list.
OK. Another option than preventing high frequencies getting INTO the driver is to stop them getting out. Covering the front of the drive (and back?.....I am not sure what an H frame is) with some sort of absorbent material is a possibility.....not very elegant.
Sorry. A very low tech approach.
Or band limit the material prior to the amp.....i.e. a small signal filter.
Cheers, Jonathan
Sorry. A very low tech approach.
Or band limit the material prior to the amp.....i.e. a small signal filter.
Cheers, Jonathan
Just a coil... nothing more? Then which one? I will need some guidance on this.
These are rated at 8 ohm speakers but the sensitivity ratings are not available. But using a crude method, I estimated the sensitivity at 95dB or more... if that helps.
Any more help is appreciated... thanks!!
mmmhh....high sensitivity means high Fs > the cone is light, compared to the high mass ones you see in subwoofers.
So, no, the effort of putting the woofer in a H-frame and filtering it still won't produce any significant bass, not the one defined as hi-fi.
Yes, it'll help the 8". The same logic can be applied to the 8" but in reverse, referred to the treble > the cone is heavy, it'll fatigue to vibrate at higher frequencies
So, no, the effort of putting the woofer in a H-frame and filtering it still won't produce any significant bass, not the one defined as hi-fi.
Yes, it'll help the 8". The same logic can be applied to the 8" but in reverse, referred to the treble > the cone is heavy, it'll fatigue to vibrate at higher frequencies
This is news to me. OB advocates do this frequently with numerous reported good results. Many have taken old, vintage woofers, put them in H-frames along with some xover stuff and made adequate bass. In fact, some say after having done what I'm trying to do say that for the first time they've really heard natural bass.
What am I missing? Other forums show what I'm talking about frequently.
Well, what Mr Bright said is right. But that comes after the choice of the right components to perform their duty.
Being a "fullrange type of guy" doesn't mean that the drivers behave different; I just reported the very basics, same like mantra/repetition.
Being a "fullrange type of guy" doesn't mean that the drivers behave different; I just reported the very basics, same like mantra/repetition.
H frame = OB, cover both sides as required with an acoustic filter which of course can be covered with speaker grill cloth/whatever to suit the decor. Let the SO/SWMBO choose if an issue. IME the best overall way for a woofer is to mount them on a stand and fine tune them by adjusting how close they are to the woofer.
Yet the better way to do it, i.e. acoustic solutions for acoustic problems. The less components in the speaker's signal chain the better.
GM
I used the small motor Goildwood GW1858 18" woofer ($63 each back awhile) in an H-frame - worked well due to what I assume is a progressive suspension that limits excurion. In its case, I think relatively low moving mass was also helpfl. It did well and nearly flat to 30Hz. The fullrange was an old alnico JBL. 8 inch. I used a second order highpass with low dcr inductor across the fullrange to limit excursion with peaks. (250 watt per channel amp) - can't remember the lowpas inductor value --- had to put a series resitor pad "before" the highpass capacitor to have the fullrange the same level as the woofer. I used one section of an L-pad for that pad.
Hi hnash53. re: #6. The previous poster is correct. Just one coil will work (but a second order LC network is better). You have solved a couple of our problems.
We now know the impedance 8ohms and if they (the 15" and 8") came from the same unit then their sensitivities should be similar. That makes life easier.
So go to a Cross-over table and find your frequency. That will give you a number for the value of inductance of the coil. Easy. E.g. 150c/s needs 9mH I think.
Now the arguments for a second order filter are these. 1st order is a pretty shallow slope. If you are doing an A/B comparison a steeper slope will help. Secondly the cap across the voice coil tends to mitigate the rise in impedance of the driver and generally allows the network to function more closely to theory.
No big deal.
Cheers Jonathan
We now know the impedance 8ohms and if they (the 15" and 8") came from the same unit then their sensitivities should be similar. That makes life easier.
So go to a Cross-over table and find your frequency. That will give you a number for the value of inductance of the coil. Easy. E.g. 150c/s needs 9mH I think.
Now the arguments for a second order filter are these. 1st order is a pretty shallow slope. If you are doing an A/B comparison a steeper slope will help. Secondly the cap across the voice coil tends to mitigate the rise in impedance of the driver and generally allows the network to function more closely to theory.
No big deal.
Cheers Jonathan
Yes, a cap may be needed, but you can often get away with just a coil in rigs like these because the 1st order cross is so low. As per your 9mH coil. Doesn't seem like it would work, but it does.
Or, as GM suggests, you can try an acoustic filter. Use something thick in front and back that will absorb the highs more than the lows. A layer or two of upholstery fabric might do the trick. Or you might need something thicker.
Or, as GM suggests, you can try an acoustic filter. Use something thick in front and back that will absorb the highs more than the lows. A layer or two of upholstery fabric might do the trick. Or you might need something thicker.
hnash. Have you looked on Siegfried Linkwitz's OB web site? All the info you'll ever want and ideas for a simple H frame knock up to see if you like it........I bet you will!
Lots I don't understand here... I'm really just a paint-by-numbers guy. Just give me simple instructions with a pic here and there and I can probably do it. But a capacitor across the voice coil? I don't know what that means.
Linkwitz's website is huge but right now don't have the patience to sift through it all.
Linkwitz's website is huge but right now don't have the patience to sift through it all.
Gotcha, it is a very technical site. There are lots of people here who can and will help. A basic OB set up though can be very worth while. Are you planning to run the 8 inch full range, I mean without any kind of xover? Linkwitz's site can be very hard to navigate, I'm always coming across stuff and thinking,, where the hell did that come from!
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The 8" full range speaker will run just as is... no crossover. It and the 15" are from the same model organ... and both very efficient.
Without mounting the 15" and without any filtering at all, I played both today and they sound good... though the amount of bass from the 15 was minimal... but it was just in the open air. An H-frame should give it a bit more ummph.
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