1st order ordinary passive network is and always will be a compromise!
Knowledge is often too vague, because it is mostly based on gathered information.
Experience is a different issue.
The 6681B was only made by Yamaha, as early as in the 70's. Possibly Meyer first got that driver from Japan, found a way to "tool" it themselves, applied for a patent, which was in 1978. A clever move. That happened a lot. Peter Qvortrup from Audionote UK patented the name Audionote. Who was there first: Audionote Japan or Audionote UK? Guess who! Kondo-san was not allowed to use the name Audionote anymore. Thats business, politics, but does not say anything about who designed what first. Now we have an Audionote Ongaku UK. Is it the real one? There is no question about who designed, built and invented the 6681B. Period!
WRONG! If you had many of those Meyer 1401's in you hands and you did not find at least those dampers on the diaphragm, maybe the latter was misused as a contraceptive and those dampers were "in the way"
Original ads in USA those are. Meaning when built for the USA, it was with ferrite.
And what if those had been back to Meyer, ferrofluid cleaned off?
The ones (Meyer Sound) which I received from Walt Bender all had ferrofluid.
When you clean the airgap, there might be particles left over. Remember, we are dealing with magnets. So to get any particles out you need a better method.
I use something similar to vaseline which I press into the airgap. Then I get it out with long toothpicks and then clean again thoroughly.
One must make sure that there is nothing in the way of the voicecoil.
But then... you show in your own webside, that you ad ferrofluid to those drivers!
That must sound terrible! I have listened to them with 1st. order passive network
at 500Hz. You have to attenuate them down to whatever SPL your woofersystem has. Ideally you have a woofersystem with 107dB but even 2 Altecs in the Onken-W will not reach that efficiency. Frontloaded horn with 1 x Altec like in a VOT close but not quite. And anyway the frontloaded horn only adds those 6dB's
more efficiency from 150Hz upwards, its a short horn. Below, -6dB less bass, so a bit thin. To weak there. I had a front-loaded horn with many 15" woofers and the huge Edgar basshorn with the 12" TAD. Even there, attenuation needed. So the resistors for attenuation will dampen the damping factor of ANY amplifier and thus you don't have -6dB but just -3dB and no damping of the critical resonance frequency. With 250Hz you are below the resonance frequency of the Yamaha. This will shout and scream if not dampened. A standard passive network 1st. order cannot dampen it.
The trick you use is that the Yamaha rolls off at 300Hz so this gives you a natural slope.. BUT... there is no real power between 250Hz and 500Hz! Remember, this is a full octave! A lot happens there. The sound is a bit like one of those ladies in old days with a corset. And this corset plus the shouting of the resonance frequency plus the added distortion by having to work to hard has a medicocre effect all the way upwards.
YAMAHA had a reason to recommend it (in AUDIO Systems) from 500Hz upwards.
See data of the 1984 catalogue, Stereo Guide Vol 19:
YAMAHA ƒz�[ƒ“ƒhƒ‰ƒCƒo�[ƒ†ƒjƒbƒgJA-6681/JA-6681B‚ÌŽd—l ƒ„ƒ}ƒn
(which was ferrite already)
So you say you had no problems. Maybe they did not smoke up, but ..
I would have a problem.... or better, my ears would have a problem.
The difference between such a passive 250Hz network and a passive-active network as I suggested is worlds.
But you have to give it a try, make the effort to find out, verify and listen.
Knowledge is often too vague, because it is mostly based on gathered information.
Experience is a different issue.
The 6681B was only made by Yamaha, as early as in the 70's. Possibly Meyer first got that driver from Japan, found a way to "tool" it themselves, applied for a patent, which was in 1978. A clever move. That happened a lot. Peter Qvortrup from Audionote UK patented the name Audionote. Who was there first: Audionote Japan or Audionote UK? Guess who! Kondo-san was not allowed to use the name Audionote anymore. Thats business, politics, but does not say anything about who designed what first. Now we have an Audionote Ongaku UK. Is it the real one? There is no question about who designed, built and invented the 6681B. Period!
WRONG! If you had many of those Meyer 1401's in you hands and you did not find at least those dampers on the diaphragm, maybe the latter was misused as a contraceptive and those dampers were "in the way"
Original ads in USA those are. Meaning when built for the USA, it was with ferrite.
And what if those had been back to Meyer, ferrofluid cleaned off?
The ones (Meyer Sound) which I received from Walt Bender all had ferrofluid.
When you clean the airgap, there might be particles left over. Remember, we are dealing with magnets. So to get any particles out you need a better method.
I use something similar to vaseline which I press into the airgap. Then I get it out with long toothpicks and then clean again thoroughly.
One must make sure that there is nothing in the way of the voicecoil.
But then... you show in your own webside, that you ad ferrofluid to those drivers!
That must sound terrible! I have listened to them with 1st. order passive network
at 500Hz. You have to attenuate them down to whatever SPL your woofersystem has. Ideally you have a woofersystem with 107dB but even 2 Altecs in the Onken-W will not reach that efficiency. Frontloaded horn with 1 x Altec like in a VOT close but not quite. And anyway the frontloaded horn only adds those 6dB's
more efficiency from 150Hz upwards, its a short horn. Below, -6dB less bass, so a bit thin. To weak there. I had a front-loaded horn with many 15" woofers and the huge Edgar basshorn with the 12" TAD. Even there, attenuation needed. So the resistors for attenuation will dampen the damping factor of ANY amplifier and thus you don't have -6dB but just -3dB and no damping of the critical resonance frequency. With 250Hz you are below the resonance frequency of the Yamaha. This will shout and scream if not dampened. A standard passive network 1st. order cannot dampen it.
The trick you use is that the Yamaha rolls off at 300Hz so this gives you a natural slope.. BUT... there is no real power between 250Hz and 500Hz! Remember, this is a full octave! A lot happens there. The sound is a bit like one of those ladies in old days with a corset. And this corset plus the shouting of the resonance frequency plus the added distortion by having to work to hard has a medicocre effect all the way upwards.
YAMAHA had a reason to recommend it (in AUDIO Systems) from 500Hz upwards.
See data of the 1984 catalogue, Stereo Guide Vol 19:
YAMAHA ƒz�[ƒ“ƒhƒ‰ƒCƒo�[ƒ†ƒjƒbƒgJA-6681/JA-6681B‚ÌŽd—l ƒ„ƒ}ƒn
(which was ferrite already)
So you say you had no problems. Maybe they did not smoke up, but ..
I would have a problem.... or better, my ears would have a problem.
The difference between such a passive 250Hz network and a passive-active network as I suggested is worlds.
But you have to give it a try, make the effort to find out, verify and listen.
Trouble is that it is not clear as springwater YET. I was intrigued by romys Melquidas amp that has a similar solution. I will order some books and an oscilloscope and in due time start fiddling with my tube amp.
As a midbass channel I know that a 800 watt amp is not optimal, but neither is a 2A3 amp. I will compare the TPA3116D2 amp, a DIY Krell KSA-100 that I will try to build, the Pass camp amp and a DIY 6L6 tube amp for this job. Another tube amp is probably a good idea IF it can move the 15" JBL with ease. The Bittner basic 800 amp will be used for subwoofer duty only. The midbass horn and the sub will probably need some eq so I will use the minidsp 4x10HD for those.
The JBL woofer sound muddy yes, and I prefer 2nd order lowpass at 400hz to keep the mud away. I would like to find something even better to put in my horn. You mentioned Altec Lansing. Are you referring to the 515 woofers?
You must have a big enough horn to cross the JA6681B at 330Hz. Try it!
As a midbass channel I know that a 800 watt amp is not optimal, but neither is a 2A3 amp. I will compare the TPA3116D2 amp, a DIY Krell KSA-100 that I will try to build, the Pass camp amp and a DIY 6L6 tube amp for this job. Another tube amp is probably a good idea IF it can move the 15" JBL with ease. The Bittner basic 800 amp will be used for subwoofer duty only. The midbass horn and the sub will probably need some eq so I will use the minidsp 4x10HD for those.
The JBL woofer sound muddy yes, and I prefer 2nd order lowpass at 400hz to keep the mud away. I would like to find something even better to put in my horn. You mentioned Altec Lansing. Are you referring to the 515 woofers?
You must have a big enough horn to cross the JA6681B at 330Hz. Try it!
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Bi-amping w. passive networks needs a very good preamp
little steps for little feet...
you need to give it time and make it right, understand it or get local help of somebody who understands.
Look, you thought that the input impedance of your Sun-Audio 2A3 amp is 100k
and that showed me that you are not that knowledged yet in this field. I'm not critising you for that, we all start and .. if we get on with it in the right way learn, also through our mistakes. That's part of the game, part of the joy as well!
A Single Ended Triode amp is quite perfect for that. I have not heard the Sun-Audio, but they use Tango outputs as far as I know, which probably are not the most expensive permalloys, nevertheless not just mainstream but of good quality.
A perfected 2 or 2 1/2-way system is imo the very best. 500Hz is an ideal crossoverfrequency if you have an Altec in an Onken. Either the 416 or the 414.
Excellent extended super dry and fast bass-response, from the very best ever.
A good straight horn (without compression, forget Klipsch) is of course also a great solution. But the Onken (and no MDF!) is great. A masterpiece.
don't know it.
Had the Krell KSA50 and 100: magic name with nothing behind. When I measure those, they show like many so-called high-end amps whats really behind: Lots of hot air and good marketing (TAS for me was not The Absolute Sound but The Absolut Shame)
Very good is to work with 2 identical amps which work perfect. 2 clean perfect SE Triode Watts will do it with ease. No more is needed. PX4 or 45 or Single-Plate 2A3
comes in mind.
You can run an Onken or Mini-Onken with 2W, thats enough. They breathe and
work with ease. Its not Watts =quantity
you need, but quality
No good idea. Equalising is only making things MUCH MUCH worse.
Very bad idea.
Flush it down the toilet and then listen to "Muddy Waters"...
Kind of filtering. Better to start with clean waters than to start with mud and
spend so much time in making it clear. When a meal is cooked wrong, you have
to start new again and use good quality ingredients and know how to cook.
If a good wine turned sour, you cannot filter it. You might be able to add lots of sugar to compensate... but it won't transform it into a Chateaux Margaux. It will be
red (or white) vinegar with alcohol and sirup.
I didn't like the 515's so much. The 416 or 414 are great. Or TAD's.
In an Onken cabinet. Made out of birchply and feltdamping.
I had enough good horns to try out. You don't get this yet:
It is the peak of the resonance frequency and that the driver has to work like an old
farm-horse in too rough conditions.
Also, to drive a poweramp correctly, you need a really good preamp, the heart of a good system. I have never heard even the best CD-player or DAC/CD-Drive which could really drive even one stereo-poweramp, forget two of them per channel (bi-amping). Of course, if you make super sensitive poweramps like Audio-Innovations once did (1000 poweramp with 4 x 2A3 parallel SE) it might work, but
those outputstages are not meant to drive 2 pairs of amps for bi-amping. Won't work. A good preamp is the control- or distribution centre, the heart. Let's not even start to talk about a good phono-system, that's another world.
Ah... and good quality cables are important as well. Many socalled Nirwana (price and voodoo) which maybe sound good in "normal audio" (whatever that might be) sound terrible with efficient speakers. Thats why those Hyperpower amps sound so terrible driving efficient high quality speakers: those amps are built to work with several Watts, but when they have to work with Mini-Watts, they show that there is no brain behind all those stuffed up muscles. Forget a soul. With good measuring equipment you can find out easely. Many famous (and super expensive) amps proove that they not worth what they aim for. Including by the way those Class-D amps. You can't cheat physics (nor experienced ears).
So, thats it.... I wrote a good deal in this, now it's up to you to make the best out of it. I am off now for holidays for 4 weeks.
Good luck
little steps for little feet...
you need to give it time and make it right, understand it or get local help of somebody who understands.
Look, you thought that the input impedance of your Sun-Audio 2A3 amp is 100k
and that showed me that you are not that knowledged yet in this field. I'm not critising you for that, we all start and .. if we get on with it in the right way learn, also through our mistakes. That's part of the game, part of the joy as well!
A Single Ended Triode amp is quite perfect for that. I have not heard the Sun-Audio, but they use Tango outputs as far as I know, which probably are not the most expensive permalloys, nevertheless not just mainstream but of good quality.
A perfected 2 or 2 1/2-way system is imo the very best. 500Hz is an ideal crossoverfrequency if you have an Altec in an Onken. Either the 416 or the 414.
Excellent extended super dry and fast bass-response, from the very best ever.
A good straight horn (without compression, forget Klipsch) is of course also a great solution. But the Onken (and no MDF!) is great. A masterpiece.
don't know it.
Had the Krell KSA50 and 100: magic name with nothing behind. When I measure those, they show like many so-called high-end amps whats really behind: Lots of hot air and good marketing (TAS for me was not The Absolute Sound but The Absolut Shame)
Very good is to work with 2 identical amps which work perfect. 2 clean perfect SE Triode Watts will do it with ease. No more is needed. PX4 or 45 or Single-Plate 2A3
comes in mind.
You can run an Onken or Mini-Onken with 2W, thats enough. They breathe and
work with ease. Its not Watts =quantity
you need, but qualityNo good idea. Equalising is only making things MUCH MUCH worse.
Very bad idea.
Flush it down the toilet and then listen to "Muddy Waters"...
Kind of filtering. Better to start with clean waters than to start with mud and
spend so much time in making it clear. When a meal is cooked wrong, you have
to start new again and use good quality ingredients and know how to cook.
If a good wine turned sour, you cannot filter it. You might be able to add lots of sugar to compensate... but it won't transform it into a Chateaux Margaux. It will be
red (or white) vinegar with alcohol and sirup.
I didn't like the 515's so much. The 416 or 414 are great. Or TAD's.
In an Onken cabinet. Made out of birchply and feltdamping.
I had enough good horns to try out. You don't get this yet:
It is the peak of the resonance frequency and that the driver has to work like an old
farm-horse in too rough conditions.
Also, to drive a poweramp correctly, you need a really good preamp, the heart of a good system. I have never heard even the best CD-player or DAC/CD-Drive which could really drive even one stereo-poweramp, forget two of them per channel (bi-amping). Of course, if you make super sensitive poweramps like Audio-Innovations once did (1000 poweramp with 4 x 2A3 parallel SE) it might work, but
those outputstages are not meant to drive 2 pairs of amps for bi-amping. Won't work. A good preamp is the control- or distribution centre, the heart. Let's not even start to talk about a good phono-system, that's another world.
Ah... and good quality cables are important as well. Many socalled Nirwana (price and voodoo) which maybe sound good in "normal audio" (whatever that might be) sound terrible with efficient speakers. Thats why those Hyperpower amps sound so terrible driving efficient high quality speakers: those amps are built to work with several Watts, but when they have to work with Mini-Watts, they show that there is no brain behind all those stuffed up muscles. Forget a soul. With good measuring equipment you can find out easely. Many famous (and super expensive) amps proove that they not worth what they aim for. Including by the way those Class-D amps. You can't cheat physics (nor experienced ears).
So, thats it.... I wrote a good deal in this, now it's up to you to make the best out of it. I am off now for holidays for 4 weeks.
Good luck
Thanks for the reply. Are you always this obnoxious or just on forums where you can get away with it? Civility reflects intellect.
Odeon: I haven't heard the Onken with Altecs, but I have heard the Klipsch Heresy recently. It might be heresy to say it but looking at an Onken design they look similar. Klipsch Heresy powered by modern expensive an Mcintosh solid state amp in the ~£5000 region could power a small concert. It was extremely impressive. Softer and more mellow sounding than my own frontloaded midbass horn with a 15" JBL, but obviously crossed too high, and not as snappy and detailed. The snappyness is to me more preferable, but I want it all so I will probably end up with both. My solution to get the mellow midbass is to use the Meyer Milo 120 12" drivers in a replica of the real thing. Good enough for Metallica, is good enough for me.
The Altecs you favoured has been tried by some people in frontloaded horns similar to mine, and the 515 were preferred. I should try them also.
The Altecs you favoured has been tried by some people in frontloaded horns similar to mine, and the 515 were preferred. I should try them also.
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things are not always what they appear to be?
Well you are entitled to believe what you wish.
I know Peter Q, there is zero doubt that Audio Note Japan came first.
John Meyer never built the 1401 driver.
Some have dampers, some do not.
Some have dope on part of the diaphragm
Some have dope on the whole diaphragm
Some have no dope at all
Some have have dope on the VC leads some don't
Some have foam blocks some don't.
None of 40+ drivers I have had in my hands, from various sources showed any signs of ferrofluid. Doesn't mean it was never used or should not be used. Ferrofluid can be a big benefit in some cases.
Sorry, I have japanese language ads.
Doubtful given the number I have checked.
How many have you checked?
I knew Walt. It is possible that he installed the ferrofluid.
The ferrofluid isn't "in the way".
If you reduce the ferrofuild in the gap by a great enough amount, it will not even touch the voicecoil. So this is a non issue.
The people who sell ferrofluid will explain the proper way to remove it. Adding in vaseline is not part of the proper plan. I'd never introduce a petroleum product into the gap unless I was 100% certain I could solvent wash it out completely.
I do not believe that is the case. I may have made reference to ferrofluid in other HF units, in specific the Focal T120 series. Link me the page - however I did have the intention of trying ferrofluid on the compression drivers, but never actually got to it.
Here you show a lack of understanding about the way compression drivers operate. In specific this one is not the same as something like an Altec 288 or anything similar to that.
You are making assumptions that are based only on your experiences, and in this instance they are not correct.
This seems right, but it is not right.
Fwiw, have you actually measured the "resonance"? I have.
There is no LF limit on this driver, except in terms of excursion and therefore power handling/SPL. This does set a practical limit, similar to the SOA of a tube or transistor. Stay inside that limit, no big problems.
I presume you know the WE555 driver? Now without looking and searching for the answer, what is the rated LF limit for this driver? And why?
Yes, of course they did. That was because if you use it to a full 40 watt input level and get out near 125dBSPL or more you have to limit the diaphragm excursion!! I'm not running at those levels. I'm running around 30dB LESS than that on average. At PA/SR levels, you'd best use a higher order slope too, while ur at it.
Again, an unwarranted assumption.
This is a super clean system, with ample headroom.
Also your assumption of how I handle the bass below 250Hz is not correct either.
The direct connection to the driver from the amplifier can sound better than if there is the imposition of any passive component. However a single high quality cap is pretty minimalist. The differential might just be in the quality of the amp itself. But I have no problem with the idea of including the required slope inside the circuitry of a dedicated amp for the compression driver. Fine way to go.
Not so good when friends want to bring their amps over for a listen... (makes for more work, and an apples and orange sort of comparision, but ok...)
Well you are entitled to believe what you wish.
I know Peter Q, there is zero doubt that Audio Note Japan came first.
John Meyer never built the 1401 driver.
WRONG! If you had many of those Meyer 1401's in you hands and you did not find at least those dampers on the diaphragm, maybe the latter was misused as a contraceptive and those dampers were "in the way"
Some have dampers, some do not.
Some have dope on part of the diaphragm
Some have dope on the whole diaphragm
Some have no dope at all
Some have have dope on the VC leads some don't
Some have foam blocks some don't.
None of 40+ drivers I have had in my hands, from various sources showed any signs of ferrofluid. Doesn't mean it was never used or should not be used. Ferrofluid can be a big benefit in some cases.
Sorry, I have japanese language ads.
Doubtful given the number I have checked.
How many have you checked?
I knew Walt. It is possible that he installed the ferrofluid.
The ferrofluid isn't "in the way".
If you reduce the ferrofuild in the gap by a great enough amount, it will not even touch the voicecoil. So this is a non issue.
The people who sell ferrofluid will explain the proper way to remove it. Adding in vaseline is not part of the proper plan. I'd never introduce a petroleum product into the gap unless I was 100% certain I could solvent wash it out completely.
I do not believe that is the case. I may have made reference to ferrofluid in other HF units, in specific the Focal T120 series. Link me the page - however I did have the intention of trying ferrofluid on the compression drivers, but never actually got to it.
Here you show a lack of understanding about the way compression drivers operate. In specific this one is not the same as something like an Altec 288 or anything similar to that.
You are making assumptions that are based only on your experiences, and in this instance they are not correct.
This seems right, but it is not right.
Fwiw, have you actually measured the "resonance"? I have.
There is no LF limit on this driver, except in terms of excursion and therefore power handling/SPL. This does set a practical limit, similar to the SOA of a tube or transistor. Stay inside that limit, no big problems.
I presume you know the WE555 driver? Now without looking and searching for the answer, what is the rated LF limit for this driver? And why?
Yes, of course they did. That was because if you use it to a full 40 watt input level and get out near 125dBSPL or more you have to limit the diaphragm excursion!! I'm not running at those levels. I'm running around 30dB LESS than that on average. At PA/SR levels, you'd best use a higher order slope too, while ur at it.
Again, an unwarranted assumption.
This is a super clean system, with ample headroom.
Also your assumption of how I handle the bass below 250Hz is not correct either.
The direct connection to the driver from the amplifier can sound better than if there is the imposition of any passive component. However a single high quality cap is pretty minimalist. The differential might just be in the quality of the amp itself. But I have no problem with the idea of including the required slope inside the circuitry of a dedicated amp for the compression driver. Fine way to go.
Not so good when friends want to bring their amps over for a listen...
(makes for more work, and an apples and orange sort of comparision, but ok...)
Thinner than paper cone speakers like the Fane Studio 8M that is much stronger around 400Hz. But the Fane is not as detailed.
No, I haven't got around to measure it yet, but I can control it pretty good with the 4x10HD minidsp so I can listen and know what frequency it is that I am listening to.
No, I haven't got around to measure it yet, but I can control it pretty good with the 4x10HD minidsp so I can listen and know what frequency it is that I am listening to.
That's an incorrect understanding of how a horn operates.
The relative sizes of the diaphragm are not relevant, assuming the horn is properly loading the compression driver.
You could think of it this way; the horn is an acoustic transformer, it takes the short strong motion of the compression driver and converts it to long weak acoustic output. Whereas a direct radiator is simply long weak motion and acoustic output.
You might say what horn you have the 6681B loaded into, or put up a pic or both... and as you say you have not measured it, so you may be hearing the effect of the horn losing loading.
Also are you judging this based on listening to sinewaves?
The sensation of a "stronger tone" can be due to hearing more 2nd and higher harmonics.
And as I inquired of the now silent odeon, are you familiar with the WE555 and how it was used in theaters, and what it is spec'd to run at??
I think if you know this you would have a different perspective on the usefulness of small diameter compression drivers at these seemingly low frequencies.
_-_-
The relative sizes of the diaphragm are not relevant, assuming the horn is properly loading the compression driver.
You could think of it this way; the horn is an acoustic transformer, it takes the short strong motion of the compression driver and converts it to long weak acoustic output. Whereas a direct radiator is simply long weak motion and acoustic output.
You might say what horn you have the 6681B loaded into, or put up a pic or both... and as you say you have not measured it, so you may be hearing the effect of the horn losing loading.
Also are you judging this based on listening to sinewaves?
The sensation of a "stronger tone" can be due to hearing more 2nd and higher harmonics.
And as I inquired of the now silent odeon, are you familiar with the WE555 and how it was used in theaters, and what it is spec'd to run at??
I think if you know this you would have a different perspective on the usefulness of small diameter compression drivers at these seemingly low frequencies.
_-_-
I think it has to do with the type of crossover I use. If the preferrable crossover was 8th order then I might not have noticed a difference, but it is not. I prefer a 1st or 2nd order on the JA6681B at 330Hz. The driver will have trouble producing anything below and the signal decreases fast below that point, not because of my crossover, but because it can't produce much below that. I think this is the why I think the JA6681B sound thinner in comparison with any kind of regular mid woofer, because it will not go as low beyond the crosssover point as e.g. a Fane Studio 8M. The Fane is very strong and clear at 400Hz and still has some juice below 330Hz which is evident with just a 1st order crossover.
It may also be due to the properties of aluminum as a material. For midbass I just like the sound of paper cone (or some kind of mix similar to paper).
I must have asked this before, but what horns are you using for the pair of JA6681B that reach 250Hz?
Pictures or it never happened!
It may also be due to the properties of aluminum as a material. For midbass I just like the sound of paper cone (or some kind of mix similar to paper).
I must have asked this before, but what horns are you using for the pair of JA6681B that reach 250Hz?
Pictures or it never happened!
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I have been using one of the Altecs, most recently a modified 203, but a 1003 or 803 will both reach 300Hz solidly. The 203 makes 250Hz.
You did not yet say which horns you are using?
I think what you said did not quite make sense... above the xover point, the xover has no effect on the amplitude. So assuming ur -3dB point was 300Hz, then at 400Hz. you ought to have "flat" level. Of course if the horn does not support that, it won't be flat.
It ought not reproduce anything below the mouth frequency/flare rate combined with the xover freq.
The benefit of a higher slope xover is in power handling. The limitation of a low slope xover for this sort of application is that the excursion *below* the xover point is reduced. Normally, with no xover the excursion increases as the frequency goes lower, limited by the surround/suspension mechanically. But in the case of compression driver that may be a problem since compression drivers have limited excursion capabilities. Thus one slaps the diaphragm or runs out of output unless something keeps the diaphragm from moving too much.
Acoustic output is limited first by the unloading of the horn, which is going to be at the mouth frequency, although the flare rate plays a role, but you won't get a flat response from too small a mouth as with a truncated horn. So the output drops like a stone at some frequency without a xover, but the excursion of the diaphragm continues (or increases). The xover kills the lower frequency electrical signal, permitting the diaphragm to operate within excursion limits. That's necessary if one intends to run the driver anywhere near the power limit of the driver/ at high SPL. This also keeps distortion lower especially in high SPL situations.
But these drivers are somewhat unique, most compression drivers have no chance of operating in a 300Hz. horn, and certainly not with a first order filter.
You can check Martin Seddon's Azura Horn site, he has graphs of the freq response on his larger horns, comparing the 6681B with things like the TAD... You'll see a scary flat unsmoothed graph. Simply stunning!
_-_-
You did not yet say which horns you are using?
I think what you said did not quite make sense... above the xover point, the xover has no effect on the amplitude. So assuming ur -3dB point was 300Hz, then at 400Hz. you ought to have "flat" level. Of course if the horn does not support that, it won't be flat.
It ought not reproduce anything below the mouth frequency/flare rate combined with the xover freq.
The benefit of a higher slope xover is in power handling. The limitation of a low slope xover for this sort of application is that the excursion *below* the xover point is reduced. Normally, with no xover the excursion increases as the frequency goes lower, limited by the surround/suspension mechanically. But in the case of compression driver that may be a problem since compression drivers have limited excursion capabilities. Thus one slaps the diaphragm or runs out of output unless something keeps the diaphragm from moving too much.
Acoustic output is limited first by the unloading of the horn, which is going to be at the mouth frequency, although the flare rate plays a role, but you won't get a flat response from too small a mouth as with a truncated horn. So the output drops like a stone at some frequency without a xover, but the excursion of the diaphragm continues (or increases). The xover kills the lower frequency electrical signal, permitting the diaphragm to operate within excursion limits. That's necessary if one intends to run the driver anywhere near the power limit of the driver/ at high SPL. This also keeps distortion lower especially in high SPL situations.
But these drivers are somewhat unique, most compression drivers have no chance of operating in a 300Hz. horn, and certainly not with a first order filter.
You can check Martin Seddon's Azura Horn site, he has graphs of the freq response on his larger horns, comparing the 6681B with things like the TAD... You'll see a scary flat unsmoothed graph. Simply stunning!
_-_-
I am saying 400Hz because around 400Hz is where it matters in the range we are discussing. The benefit of using the Minidsp is that I can experiment with a lot of channels at the same time and the Fane S 8M in a 150Hz horn filled up the lower mids range nicely. I almost want to add it as a channel, but then can't have all the horns on a vertical line unless I raise the ceiling to 4 meters.
The Altec 203 horns looks small! You should try an even bigger horn and see what happens. I made a replica of the Avantgarde Acoustics Trio midbass horn, didn't like it, and made it slightly more narrow and longer to fit the JA6681B. I won't need to go bigger than that I think. I might have overdone it and should try a smaller horn, but these sound very nice.
The Altec 203 horns looks small! You should try an even bigger horn and see what happens. I made a replica of the Avantgarde Acoustics Trio midbass horn, didn't like it, and made it slightly more narrow and longer to fit the JA6681B. I won't need to go bigger than that I think.
I might have overdone it and should try a smaller horn, but these sound very nice.
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Well you are comparing a 150Hz horn to a 250-300Hz horn... not sure that works exactly.
But if you did not follow the earlier things that I mentioned, then we don't have a common basis for discussion.
The Altec 203 horns are not "small" they are close to 3ft across the face. Not quite, and about that deep.
You may not realize from just looking casually that I'm covering from ~250Hz up to >10kHz. with one driver and one horn. Hard to beat.
But if you did not follow the earlier things that I mentioned, then we don't have a common basis for discussion.
The Altec 203 horns are not "small" they are close to 3ft across the face. Not quite, and about that deep.
You may not realize from just looking casually that I'm covering from ~250Hz up to >10kHz. with one driver and one horn. Hard to beat.
I have a midhorn also, a replica of the mefore mentioned trio speakers kugelwellen midhorn (500/600-12000Hz) as well and I think they compliment each other very well with different strengths. Without the big horn the sound is more normal but dull. With only the big horn I lose some detail (not output) around 1000-2000hz.
I think my biggest JA6681B horn is very similar to the azura 200 horn.
Is it not a good rule not to use a horn down to its limit but to cross a few octaves up? My output drops like a stone below 200Hz, but starts to decrease slightly before that. The output is not why I think it sound thinner. Paper woofers seem to carry lower mids better and are warmer to listen to - probably because of the harmonics that you mentioned.
So since I am only using 1-2W I can run my JA6681B fullrange, is that what you said? I get nervous when I know I prefer 1st or 2nd order slopes while I am so close delivering bass frequencies to the driver. Especially with 1st order slopes I can hear a disconcerning amount of bass. But higher than 3rd order just don't sound right in a mid horn.
I think my biggest JA6681B horn is very similar to the azura 200 horn.
Is it not a good rule not to use a horn down to its limit but to cross a few octaves up? My output drops like a stone below 200Hz, but starts to decrease slightly before that. The output is not why I think it sound thinner. Paper woofers seem to carry lower mids better and are warmer to listen to - probably because of the harmonics that you mentioned.
So since I am only using 1-2W I can run my JA6681B fullrange, is that what you said? I get nervous when I know I prefer 1st or 2nd order slopes while I am so close delivering bass frequencies to the driver. Especially with 1st order slopes I can hear a disconcerning amount of bass. But higher than 3rd order just don't sound right in a mid horn.
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I'd have to look up that trio speakers kugelwellen midhorn to see what it is.
You say you have one similar to the Azura? Pretty sure, iirc, that is a tractrix expansion.
Yes, most horns will perform somewhat better up an octave from their cutoff, but I think this depends greatly upon the horn and driver. Two octaves up is too far, as many horns don't cover that many octaves!
Assuming ur 1-2watts is in a tube amp, and probably a SE triode, I'd expect plenty of "warmth".
You can likely get away with running ur 6681B with a first order slope using 1-2watts and have no problems at all. I do. However, I do have back up diaphragms and drivers, so my level of concern is low. Never had a problem yet, and I use an amp that is capable of pushing them to their power limit (although I am always careful with levels, and have yet to make a big mistake)
I doubt you can hear any bass using a 1st order slope on your large "200" horn.
I do use a much higher slope to get the driver that meets the horn up from the bottom OUT. Personally I don't want to hear the cone driver in the horn's working range at all.
4th order might sound much better than 2nd or third, IF you are going higher order. Worth considering. But once you go passive 4th, there are a wide range of xover design considerations where some minor details effect the performance and sound rather a lot.
I'd suggest putting the rolloff into your amp, and direct connecting to the driver. As mentioned by odeon, there is something "better" about this in many cases.
A first order would be so simple.
I would NOT run the driver without any LF rolloff - not run it "fullrange".
You say you have one similar to the Azura? Pretty sure, iirc, that is a tractrix expansion.
Yes, most horns will perform somewhat better up an octave from their cutoff, but I think this depends greatly upon the horn and driver. Two octaves up is too far, as many horns don't cover that many octaves!
Assuming ur 1-2watts is in a tube amp, and probably a SE triode, I'd expect plenty of "warmth".
You can likely get away with running ur 6681B with a first order slope using 1-2watts and have no problems at all. I do. However, I do have back up diaphragms and drivers, so my level of concern is low. Never had a problem yet, and I use an amp that is capable of pushing them to their power limit (although I am always careful with levels, and have yet to make a big mistake)
I doubt you can hear any bass using a 1st order slope on your large "200" horn.
I do use a much higher slope to get the driver that meets the horn up from the bottom OUT. Personally I don't want to hear the cone driver in the horn's working range at all.
4th order might sound much better than 2nd or third, IF you are going higher order. Worth considering. But once you go passive 4th, there are a wide range of xover design considerations where some minor details effect the performance and sound rather a lot.
I'd suggest putting the rolloff into your amp, and direct connecting to the driver. As mentioned by odeon, there is something "better" about this in many cases.
A first order would be so simple.
I would NOT run the driver without any LF rolloff - not run it "fullrange".
