Does a sloped baffle help with the breakup mode
I've read here in several posts that there may be problems with the 6db slope on the woofer because the woofer starts breaking up at the higher frequencies. Does this coincide with the woofer starting to beam? If so, does placing the listener off axis help? I'm wondering whether this is how manufacturers such as Meadowlark who use sloped baffles (ostensibly for time-alignment) minimize this problem. This is just a WAG (wild a** guess) in the hope that someone with more experience can provide the correct answer.
I've read here in several posts that there may be problems with the 6db slope on the woofer because the woofer starts breaking up at the higher frequencies. Does this coincide with the woofer starting to beam? If so, does placing the listener off axis help? I'm wondering whether this is how manufacturers such as Meadowlark who use sloped baffles (ostensibly for time-alignment) minimize this problem. This is just a WAG (wild a** guess) in the hope that someone with more experience can provide the correct answer.
interesting idea SRMC... i'm not sure how strong the beaming effect is for the average woofer at its breakup frequency, but as a general rule beaming becomes a factor when the diameter of the radiating surface is greater than the wavelength of the signal. if you figure sound travels about 13,000 inches/sec or so, then a 6" woofer begins beaming above 2.2khz or so.
p.s. frank he's saying that if the cone beams at breakup, and you're angling the cone up, then perhaps the beaming will attenuate the breakup somewhat...
p.s. frank he's saying that if the cone beams at breakup, and you're angling the cone up, then perhaps the beaming will attenuate the breakup somewhat...
beaming, breakup etc etc
beaming is related to all woofers depending on size. I can't remember exactly when this effects starts to happen on different sizes, but is one of the reasons for not crossing woofers too high. If I remember correctly, 8" drivers start to beam at about 2.5k, 6" at about 3k etc but it all depends on cone geometry too.
break-up is totally different, and is to do with the hardness, damping and other properties of the cone. Poly cones for eg are softish and generally very well damped, and tend to have very smooth roll-off (at the possible expense of upper mid detail) Hard cones (which usaully have better mid detail) tend to hang on to the resonances and release them at the upper end of their response. If you go to say the d-s-t site and look at different curves for different types of drivers you will see that hard cones generally have a large spike in the 4-5k region, which makes them basically impossible to use with shallow sloped x-os.
sloped baffles are again a different issue, and are generally used to bring the voice coil acoustic centres of the drivers into vertical alignment so that there is reduced phase difference between what is sent from the 2 drivers.
again, trying to keep things general in nature rather than getting too technical !
beaming is related to all woofers depending on size. I can't remember exactly when this effects starts to happen on different sizes, but is one of the reasons for not crossing woofers too high. If I remember correctly, 8" drivers start to beam at about 2.5k, 6" at about 3k etc but it all depends on cone geometry too.
break-up is totally different, and is to do with the hardness, damping and other properties of the cone. Poly cones for eg are softish and generally very well damped, and tend to have very smooth roll-off (at the possible expense of upper mid detail) Hard cones (which usaully have better mid detail) tend to hang on to the resonances and release them at the upper end of their response. If you go to say the d-s-t site and look at different curves for different types of drivers you will see that hard cones generally have a large spike in the 4-5k region, which makes them basically impossible to use with shallow sloped x-os.
sloped baffles are again a different issue, and are generally used to bring the voice coil acoustic centres of the drivers into vertical alignment so that there is reduced phase difference between what is sent from the 2 drivers.
again, trying to keep things general in nature rather than getting too technical !
BEAM ME UP SCOTTY.
Hi there,
Beaming is a change in polar behaviour with respect to rising frequency.
It is not something I would loose sleep over though except perhaps for some really odd designs.
Break up is dependant on the physical properties of the materials in use: paper,polyprops,kevlar and so on all have different mechanical properties with respect to thickness,cone diameter,stiffness.
And this may come unespected : will also change their mechanical behaviour depending on the load they see.
Closed sealed box,open baffles,bass reflexes,transmission lines will all give different break up modes.
Again this is not of a major importance since you will probably use filters that cross below and as such dampen any subsequent break up.
Yes,provided you know the acoustic center and that is not at the membrane surface as so many seem to think.
The theoretical surface is much nearer the voicecoil.
And this too will change with different filter types causing phaseshift.
As you can see it ain't that simple.
Cheers,
Hi there,
Beaming is a change in polar behaviour with respect to rising frequency.
It is not something I would loose sleep over though except perhaps for some really odd designs.
Break up is dependant on the physical properties of the materials in use: paper,polyprops,kevlar and so on all have different mechanical properties with respect to thickness,cone diameter,stiffness.
And this may come unespected : will also change their mechanical behaviour depending on the load they see.
Closed sealed box,open baffles,bass reflexes,transmission lines will all give different break up modes.
Again this is not of a major importance since you will probably use filters that cross below and as such dampen any subsequent break up.
Yes,provided you know the acoustic center and that is not at the membrane surface as so many seem to think.
The theoretical surface is much nearer the voicecoil.
And this too will change with different filter types causing phaseshift.
As you can see it ain't that simple.
Cheers,
Have any of you guys had much luck getting a 1st order non-time aligned speaker to sum anywhere near flat with the drivers in-phase?
A mate and me are designing a mmtmm with a vifa H26TG-35-06 hornloaded dome and 4 HM130CO carbon 5 1/4" audax woofers.
The drivers *look* like the voice coils would be fairly close to being aligned, due to the depth of the tweeter and small size woofer.
But when we measured using speaker workshop and simulated a 1st order crossover, we couldn't avoid a huge hole at the crossover point when the drivers are in-phase (out-of-phase is nearly perfect, but that sort of defeats the purpose).
We are now investigating time alignment, but this creates other diffraction problems.
When we simulate a time aligned design (about 30mm I think) we are also getting a fair bit of destructive inference either side of the crossover point. Not very nice IMO.
(All my other crossovers have been 4th order acoustic, so these problems didn't occur).
Any tips?
Mark
A mate and me are designing a mmtmm with a vifa H26TG-35-06 hornloaded dome and 4 HM130CO carbon 5 1/4" audax woofers.
The drivers *look* like the voice coils would be fairly close to being aligned, due to the depth of the tweeter and small size woofer.
But when we measured using speaker workshop and simulated a 1st order crossover, we couldn't avoid a huge hole at the crossover point when the drivers are in-phase (out-of-phase is nearly perfect, but that sort of defeats the purpose).
We are now investigating time alignment, but this creates other diffraction problems.
When we simulate a time aligned design (about 30mm I think) we are also getting a fair bit of destructive inference either side of the crossover point. Not very nice IMO.
(All my other crossovers have been 4th order acoustic, so these problems didn't occur).
Any tips?
Mark
Re: TIOXID DIOXINE
Real ribbons tend not to be cheap thou. The Decca London ribbons are probably the finest tweeters i've ever heard -- haven't heard any of the modern ones, i'd need a set of Raven 3s to be able to XO 1st order at 8-10k -- kinda pricy for super tweeters
dave
fdegrove said:
Real ribbons tend not to be cheap thou. The Decca London ribbons are probably the finest tweeters i've ever heard -- haven't heard any of the modern ones, i'd need a set of Raven 3s to be able to XO 1st order at 8-10k -- kinda pricy for super tweeters
dave
Re: Re: CHOICE
Looks like a polycone -- has pretty smooth response. Another to consider are any of the P13s, the midrange or the midbass if you need to go lower. The latter is often run out full range with a cap XOed tweeter.
I like to get the XO up above 5 k (right now it is at 10k with the 4" FRs)
dave
massive said:
Looks like a polycone -- has pretty smooth response. Another to consider are any of the P13s, the midrange or the midbass if you need to go lower. The latter is often run out full range with a cap XOed tweeter.
I like to get the XO up above 5 k (right now it is at 10k with the 4" FRs)
dave
Re: beaming, breakup etc etc
Cone geometries, phase plugs, and designed in cone flexure can all aid in decreasing the beaming at the top end. Jordan is probably the master of flexure (took him some 40 years to get where he is now) and the diatones with their flexible cones are another example. I see a lot of old alnico FRs with either steeply curved profiles or annular rings to get their response up and less beamy. A phase plug essentially havles the diameter of the driver and if done right can get another octave out of the driver.
dave
Andy Graddon said:
Cone geometries, phase plugs, and designed in cone flexure can all aid in decreasing the beaming at the top end. Jordan is probably the master of flexure (took him some 40 years to get where he is now) and the diatones with their flexible cones are another example. I see a lot of old alnico FRs with either steeply curved profiles or annular rings to get their response up and less beamy. A phase plug essentially havles the diameter of the driver and if done right can get another octave out of the driver.
dave
andy g wrote...
For instance, if a 6ohm tweeter has a 12 ohm resistor parallel to it, it will only draw 2/3 of the hi-freq signal through it, so you can lower the x-o point etc
And since in a lot of cases the tweet will have a higher sensitivity than the woofer and need padding anyway, the right L-pad can allow you to cross significantly lower than indicated in my previous statement......
A parallel resistor can also have quite a large effect on the res freq impedance value of the tweeter as seen by the crossover. Suppose a tweeter has an Fs impedance of 30 ohms (some non ferro tweets go this high!) and you pad it with a 10 ohm parallel resistor, then the most the x-o "sees" is about 9 ohms, and the resistor takes a "large amount" of the signal, at that point (so you gotta use high power resistors). nearly as good as using an LRC !!!
sorry for includng such a large portion of you post andy but i wanted ot get everyone on the same page.
1. yes using a low value (10ohms and such) parallel resistor is a very useful technique to drain power of teh tweeter and to avoid using a LRC. I have used this technique on my 9900 they have a large peak at 500hz or so and an LRC was too expensive (1.7mh and 64uf).
2. What I am trying to do is to get adequate protection for a very valuable tweeter (I cant get replacements in India) - a Vifa TC series tweeter. it not not expensive but if i blow one I cant get a replacement. giving my limitaions i am looking at building a 2nd order series XO as described on your website.
L1= 0.5mh, C1 = 4.7uf, C2 = 3.3uf or 4.7uf, L2 = 1mh.
The tweeter will have an Lpad using Rs=4ohms and Rp=10ohms.
the woofer will have impedance compesation using 20uf and 6ohms.
I will run this XO bypassing C2 and L2 and compare the sound. I expect L2 to offer difraction step compensation and C2 to offer additional protection to the tweeter. I have also noticed that on the spreadsheet on your website C2 < C1 hence I am thinking of 3.3uf. otherwise I guess 4.7uf will offer enough protection.
what do you think.
For instance, if a 6ohm tweeter has a 12 ohm resistor parallel to it, it will only draw 2/3 of the hi-freq signal through it, so you can lower the x-o point etc
And since in a lot of cases the tweet will have a higher sensitivity than the woofer and need padding anyway, the right L-pad can allow you to cross significantly lower than indicated in my previous statement......
A parallel resistor can also have quite a large effect on the res freq impedance value of the tweeter as seen by the crossover. Suppose a tweeter has an Fs impedance of 30 ohms (some non ferro tweets go this high!) and you pad it with a 10 ohm parallel resistor, then the most the x-o "sees" is about 9 ohms, and the resistor takes a "large amount" of the signal, at that point (so you gotta use high power resistors). nearly as good as using an LRC !!!
sorry for includng such a large portion of you post andy but i wanted ot get everyone on the same page.
1. yes using a low value (10ohms and such) parallel resistor is a very useful technique to drain power of teh tweeter and to avoid using a LRC. I have used this technique on my 9900 they have a large peak at 500hz or so and an LRC was too expensive (1.7mh and 64uf).
2. What I am trying to do is to get adequate protection for a very valuable tweeter (I cant get replacements in India) - a Vifa TC series tweeter. it not not expensive but if i blow one I cant get a replacement. giving my limitaions i am looking at building a 2nd order series XO as described on your website.
L1= 0.5mh, C1 = 4.7uf, C2 = 3.3uf or 4.7uf, L2 = 1mh.
The tweeter will have an Lpad using Rs=4ohms and Rp=10ohms.
the woofer will have impedance compesation using 20uf and 6ohms.
I will run this XO bypassing C2 and L2 and compare the sound. I expect L2 to offer difraction step compensation and C2 to offer additional protection to the tweeter. I have also noticed that on the spreadsheet on your website C2 < C1 hence I am thinking of 3.3uf. otherwise I guess 4.7uf will offer enough protection.
what do you think.
BLUE RIBBON
Hi,
While I certainly agree with that ,you sometimes find some decent ones at very competive prices.
An example:
http://www.visaton.de/deutsch/highend.htm
This is the newer version,the one I have in the older SD1 speaker was a tad more efficient with its 92dB.
Noteworthy is also the nominal 8 Ohm impedance which I prefer.
At the time I payed about 100USD/ea and the spare membranes were only about 25USD.
I also remember Philips making something similar.
One of the most expensive but most impressive ones is made by a Dutch company called Stage Acompany:
http://www.stageaccompany.com/
Cheers,
Hi,
While I certainly agree with that ,you sometimes find some decent ones at very competive prices.
An example:
http://www.visaton.de/deutsch/highend.htm
This is the newer version,the one I have in the older SD1 speaker was a tad more efficient with its 92dB.
Noteworthy is also the nominal 8 Ohm impedance which I prefer.
At the time I payed about 100USD/ea and the spare membranes were only about 25USD.
I also remember Philips making something similar.
One of the most expensive but most impressive ones is made by a Dutch company called Stage Acompany:
http://www.stageaccompany.com/
Cheers,
I'm, again, upping very old thread if we could have more discussion about this subject.
---
2-way with single cap! How do we make it? Many people listen to music with 5-8" fullranger, how on earth there are so less 2-ways with minimal XO? (good tweeter costs so much?)
Rules here:
* Listening level must low. Tweeter with 1st order (electrical) does not handle much power.
* Tweeter must be very good, very low Fs and with low impedance rise at Fs
* woofer must be soft coned so it has no break up
* woofer should have little "natural BSC" (they exist but not often) OR enclosure must be wide
* woofer should 6,5"-8", I think. Smaller aren't enough capable producing bass and bigger are too beaming
----
Which driver do you think is harder to find for this? Tweeter or woofer?
I've had Epos ES14's (one cap XO) for 3 years now and I know it is possible to enjoy music through them. Something playing LOUD! Never burned tweeter.
---
2-way with single cap! How do we make it? Many people listen to music with 5-8" fullranger, how on earth there are so less 2-ways with minimal XO? (good tweeter costs so much?)
Rules here:
* Listening level must low. Tweeter with 1st order (electrical) does not handle much power.
* Tweeter must be very good, very low Fs and with low impedance rise at Fs
* woofer must be soft coned so it has no break up
* woofer should have little "natural BSC" (they exist but not often) OR enclosure must be wide
* woofer should 6,5"-8", I think. Smaller aren't enough capable producing bass and bigger are too beaming
----
Which driver do you think is harder to find for this? Tweeter or woofer?
I've had Epos ES14's (one cap XO) for 3 years now and I know it is possible to enjoy music through them. Something playing LOUD! Never burned tweeter.
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That hasn't been my experience - my DIY one-cap-one-inductor equipped Dynaudio two-ways play very loudly without breaking up.
So have I (I wrote bit wrong). I meant that it is obvious that the more you have protection for drivers the more loud you can play. And 1st order slopes must be enough at least if you listen at moderate levels in smallish room. (distortion stays low also)
----
things came to my mind.
* should tweeter be hard dome because it is working at its low end, more excursion? Hard cone woofers are better (more pistonic) at bass. Analogy to tweeters?
* tweeter should not be too efficient. Usually they are more efficient than proper woofer.
* it is hard to find woofer that has natural roll off at 2,5-4,0 kHz. Seas A26RE seems to be the one.
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Use ferrofluid tweeter with low resonance.
There are fanatic in France of 2 ways with only 3 components.
My experience is to say, the sound is not the clearest. I experimented the Njord from SEAS
The original crossover : 3kHz LR2 ?
The final crossover we done, 1.8kHz LR4:
With 3 components it could work but we need a lot of good conditions.
There are fanatic in France of 2 ways with only 3 components.
My experience is to say, the sound is not the clearest. I experimented the Njord from SEAS
The original crossover : 3kHz LR2 ?
An externally hosted image should be here but it was not working when we last tested it.
The final crossover we done, 1.8kHz LR4:
An externally hosted image should be here but it was not working when we last tested it.
With 3 components it could work but we need a lot of good conditions.
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