Francis, as I understand, that would in fact be a front loaded horn. Which way the driver faces is irrelevant to the definition of FLH or BLH. A FLH has a rear compression chamber to control excursion below fc, and it may have a front compression chamber to transition from the SD to the throat area which will be less. A BLH has the driver radiating directly, hence a FLH without the rear compression chamber is a contradiction in terms!
Horn experts: is this right?
Slowmotion,
You are right and I love you for backing me up.
Paul,
I'm not sure about your definition of a FLH; horns have a mouth, throat & compression chamber.
The comprsn. chamber compresses the driver area into the mouth literally.
Cut-off frequency is determined by the mouth area(low end) and throat area(high end).
Sure, if it's just a matter of naming the closed box, then you can call it as you say a compression chamber. In a lighter note I'd call it a prevention chamber.
For me, the closed box just prevents the back wave from meeting its frontal counterpart. It should only be not so small so as to hamper the cone excursion.
You're absolutely correct about the fact that the front or back of the driver should radiate sound identically; but I read info. about bandpass enclosures and there, the volumes of the back and front chambers are different for back-loaded and front-loaded. I've not yet found out why.
Any further insight is welcome.
Humbly,
Francis
You are right and I love you for backing me up.
Paul,
I'm not sure about your definition of a FLH; horns have a mouth, throat & compression chamber.
The comprsn. chamber compresses the driver area into the mouth literally.
Cut-off frequency is determined by the mouth area(low end) and throat area(high end).
Sure, if it's just a matter of naming the closed box, then you can call it as you say a compression chamber. In a lighter note I'd call it a prevention chamber.
For me, the closed box just prevents the back wave from meeting its frontal counterpart. It should only be not so small so as to hamper the cone excursion.
You're absolutely correct about the fact that the front or back of the driver should radiate sound identically; but I read info. about bandpass enclosures and there, the volumes of the back and front chambers are different for back-loaded and front-loaded. I've not yet found out why.
Any further insight is welcome.
Humbly,
Francis
It appears that different sources use slightly different terms here, and it can easily get confusing.
Horn response:
Rear compression chamber VRC is used for the rear chamber in a FLH (0 is entered for a FLH)
Throat chamber VTC is used from the chamber between driver and horn throat
However another source agrees with Jan, and calls the chamber behind the driver in a FLH the back chamber.
So the difference between a FLH and BLH is a rear chamber. Many FLHs don't have a front compression chamber, but if you remove the rear chamber from a FLH, it is by definition a BLH, as the direct radiator component is what distinguishes a FLH and BLH.
Based on my reading of horns so far, it seems that in a FLH, both chambers can be considered "compression chambers" although the two have a different function. I'm not attempting to make up my terms here. My understanding is that this is standard terminology.
Jan,
It seems to me that you have your "usually" and "always" the wrong way around.
That was not really my point, although in the range we are dealing with in a bass horn, that should be reasonably accurate.
The bandpass query is a totally different issue. The different volumes relate to two different chambers, each with a different purpose. In the case of a 4th order bandpass, one chamber is sealed, the other vented. The vented chamber essentially adds a LP filter to a sealed box. In a 6th order bandpass, each chamber is tuned to control the upper and lower end of the bandwidth to be covered, hence their volumes will be those that are required to achieve the necessary tuning point.
Hi Paul
Yes. But usually one understands the meaning anyway
Yes, you are right, Mcbean uses the term "rear compression chamber".
As far as I know it is usually called the back chamber.
? Do you mean BLH ?
McBean states:
"Enter zero for VRC and/or LRC if back-laded horn - or - no rear chamber".
Again, you are right, according to McBean.
However, as far as I know, most people uses the term "compression chamber" for the chamber between driver and throat.
Hmmm, I think that's a bit too simple...
A BLH is usually designed to use both the output from the driver as a direct radiator and the output of the horn, combined.
A typical example is the various backloaded Lowther-horns,
where the midrange from the driver as a direct radiator is combined with the bass-output from the horn. These typically use a compression chamber between the driver and the horn, by the way.
Another example is the JBL scoops.
A typical front loaded horn is designed to use the output of the driver through the horn only. The horn/driver combination may ,
or may not, use a back-chamber behind the driver, that's beside the point.
You also have combinations of front-loaded horns and vented box,
like the typical Altecs, and you have compound horns where you employ the same driver for both front-loaded and rear-loaded horns at the same time. But that's another matter.
True
Again, I think it's to simple to put it that way
I can certainly agree with that.
Huh?
cheers
paulspencer said:
Yes. But usually one understands the meaning anyway
Yes, you are right, Mcbean uses the term "rear compression chamber".
As far as I know it is usually called the back chamber.
? Do you mean BLH ?
McBean states:
"Enter zero for VRC and/or LRC if back-laded horn - or - no rear chamber".
Again, you are right, according to McBean.
However, as far as I know, most people uses the term "compression chamber" for the chamber between driver and throat.
Hmmm, I think that's a bit too simple...
A BLH is usually designed to use both the output from the driver as a direct radiator and the output of the horn, combined.
A typical example is the various backloaded Lowther-horns,
where the midrange from the driver as a direct radiator is combined with the bass-output from the horn. These typically use a compression chamber between the driver and the horn, by the way.
Another example is the JBL scoops.
A typical front loaded horn is designed to use the output of the driver through the horn only. The horn/driver combination may ,
or may not, use a back-chamber behind the driver, that's beside the point.
You also have combinations of front-loaded horns and vented box,
like the typical Altecs, and you have compound horns where you employ the same driver for both front-loaded and rear-loaded horns at the same time. But that's another matter.
True
Again, I think it's to simple to put it that way
I can certainly agree with that.
Huh?
cheers
Never mind that. We 90% agree here, I'm not worried about the other 10%.
I posted recently regarding a Rhino Acoustics Bassmax horn, which I presumed to be a FLH without a rear chamber. I think it was GM who said this is in fact a contradiction in terms, implying by this that a FLH will always have a rear chamber.
What you seem to be saying is that FLH vs BLH is defined by whether or not using the direct radiator component is part of the design. By this distinction, a horn with a fullranger like a Lowther would be a BLH and a wide bandwidth would be used, but a subwoofer driver without a rear chamber would be considered a FLH since the direct radiator component is negligable.
This seems equally valid as saying that BLH vs FLH is distinguished most by the presence or absence of a rear chamber.
Whether or not there is an industry standard definition here I don't know.
paulspencer said:
I was afraid someone would say that... I edited as opposed to adding comments to make the entire thing easier to read and more useful, so that makes it hard to point out all specifics. In general, I added some historical stuff to the intro from David McBean and qualified statements about Hornresp only being useful for basshorns (which I feel is false to some degree), clarified some technical typos in the ANG section, added information on compression ratios, revised some language about some of the following text entry boxes to make meanings clearer (I understood what Johan was saying, but some of his language might have been a bit confusing to a complete newbie), corrected / clarified some of the info on driver parameters and front and rear chamber entry boxes, and wrote something for the last section - how high you can go before results are inaccurate. I also tried to correct spelling and punctuation errors when I saw them to reduce distractions for readers.
John
Back Chamber and Front Loaded Horns
I just read an article "The Show Horn", by Bruce Edgar, in Speaker Builder 2/90 which discusses horn design. In his article he describes "throat reactance", which rises with decreasing frequency and peaks at the flare frequency, unfortunately reducing low frequency output. He goes on to describe the use of the sealed back chamber, developed and refined by the Names of acoustic horn science, to provide "reactance annulling" to cancel out or counteract this throat reactance and allow bass response to extend down toward the flare frequency.
Hope this helps.
I just read an article "The Show Horn", by Bruce Edgar, in Speaker Builder 2/90 which discusses horn design. In his article he describes "throat reactance", which rises with decreasing frequency and peaks at the flare frequency, unfortunately reducing low frequency output. He goes on to describe the use of the sealed back chamber, developed and refined by the Names of acoustic horn science, to provide "reactance annulling" to cancel out or counteract this throat reactance and allow bass response to extend down toward the flare frequency.
Hope this helps.
quote: The different volumes relate to two different chambers, each with a different purpose.
------------------------------------------------------
Paul,
Yes, vented chamber and sealed chamber each have different volumes due to their different functions.
What I was trying to elucidate - wouldn't there be a difference between a sealed rear chamber and sealed front chamber in a bandpass enclosure, if we choose to go against conventional "sealed rear & vented front".
I'm not going off-topic but there appears to be some difference between the radiation from the front and the back of a driver eventhough theoretically there shouldn't be any.
I happened to look up some old literature on horn design, W. Leach(if I remember correctly) also mentions, as you say, the rear "compression chamber" in a FLH. Actually it doesn't compress but only attempts to equalise loading on both sides of the driver.
I haven't tried Hornresponse or any other software oriented calculators yet. I have experience only in building a BLH and that too around 15 years ago.
Sorry if I've in any way offended your sensibilities.
Warm regards,
Francis
------------------------------------------------------
Paul,
Yes, vented chamber and sealed chamber each have different volumes due to their different functions.
What I was trying to elucidate - wouldn't there be a difference between a sealed rear chamber and sealed front chamber in a bandpass enclosure, if we choose to go against conventional "sealed rear & vented front".
I'm not going off-topic but there appears to be some difference between the radiation from the front and the back of a driver eventhough theoretically there shouldn't be any.
I happened to look up some old literature on horn design, W. Leach(if I remember correctly) also mentions, as you say, the rear "compression chamber" in a FLH. Actually it doesn't compress but only attempts to equalise loading on both sides of the driver.
I haven't tried Hornresponse or any other software oriented calculators yet. I have experience only in building a BLH and that too around 15 years ago.
Sorry if I've in any way offended your sensibilities.
Warm regards,
Francis
Thanks John. I don't want beginners to be misled by incorrect information which hasn't been checked! Much appreciated.
bzdang,
I'm still trying to grasp that "reactance annulling!"
francis,
no offence taken in any way; like you I'm here to both learn and contribute, and a little debate helps at times!
Actually, there is a difference between the rear and front radiation of a driver, it's just not relevant to bass. There is an acoustic shadow caused by the basket and motor, by this is in the midrange and above. The only difference that I know of in this case is that the basket and motor occupy volume in the rear chamber of a bandpass box. A bandpass won't have a high enough response to encounter significant differences in rear and front radiation.
bzdang,
I'm still trying to grasp that "reactance annulling!"
francis,
no offence taken in any way; like you I'm here to both learn and contribute, and a little debate helps at times!
Actually, there is a difference between the rear and front radiation of a driver, it's just not relevant to bass. There is an acoustic shadow caused by the basket and motor, by this is in the midrange and above. The only difference that I know of in this case is that the basket and motor occupy volume in the rear chamber of a bandpass box. A bandpass won't have a high enough response to encounter significant differences in rear and front radiation.
Hi
Going well guys
Could someone who knows the basic theory, experience etc post the parameters ideal/ priorities in choosing good drivers for:
- bass (flare 30-50 Hz) and midbass (flare 75-100 Hz) – are they the same
- midhorn (300-600 Hz), either compression or conventional
- tweeters
Some suggestions amongst drivers currently reasonably readily available would be very useful too.
Thanks
Going well guys
Could someone who knows the basic theory, experience etc post the parameters ideal/ priorities in choosing good drivers for:
- bass (flare 30-50 Hz) and midbass (flare 75-100 Hz) – are they the same
- midhorn (300-600 Hz), either compression or conventional
- tweeters
Some suggestions amongst drivers currently reasonably readily available would be very useful too.
Thanks
I've added some more pages and done some editing, still quite a bit more to be added as I hunt down more and learn more.
I've added a page with links to horn designs online which should be of interest. One interesting project is Wayne Parham's 12pi bass horn which is similar to the lab sub with some improvements - push pull mounting and an improvment to the driver's thermal power handling! Very impressive stuff.
I've added a page with links to horn designs online which should be of interest. One interesting project is Wayne Parham's 12pi bass horn which is similar to the lab sub with some improvements - push pull mounting and an improvment to the driver's thermal power handling! Very impressive stuff.
Under loudspeakers, the bass horn section ....
http://www.diyaudio.com/wiki/index.php?page=Loudspeaker
http://www.diyaudio.com/wiki/index.php?page=Loudspeaker
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.