boom3 Posted September 21, 2012 Share Posted September 21, 2012 I've noticed that some bass horns have a throat that starts out smaller than the apeture of the woofer motorboard, then the expansion to the rest of the horn begins. This is of course a common feature of MF/HF horns-the "compression throat", but I have not encountered it in the literature as being desirable on bass horns. Comments? Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted September 21, 2012 Share Posted September 21, 2012 Don't ask me, I failed throat algebra. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted September 21, 2012 Share Posted September 21, 2012 This is of course a common feature of MF/HF horns-the "compression throat", but I have not encountered it in the literature as being desirable on bass horns. Comments? That's how the Lascala bass driver is mounted. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted September 21, 2012 Share Posted September 21, 2012 When you look at the THT, the driver is mounted in a different direction (90 degrees) to the horn throat, and the LaScala is mounted firing right at the horn throat. I imagine the start of the horn needs to be small, and get larger as it moves out. If the LaScala didn't have the slot, the horn would be starting larger than the beginning of the horn throat. I bet dimensionally, the slot is equal to what the horn would be if it did not have the airspace and the little triangular piece. Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted September 21, 2012 Moderators Share Posted September 21, 2012 Comments? Wish I knew some reasons why and what it really does. The back space is also interesting and how it would compare with the throat size, if it even does ? This is the MWM back space and throat which is 7" wide on a 15" driver. Quote Link to comment Share on other sites More sharing options...
boom3 Posted September 21, 2012 Author Share Posted September 21, 2012 THT? Quote Link to comment Share on other sites More sharing options...
tfoust Posted September 21, 2012 Share Posted September 21, 2012 Tuba Home Theater Quote Link to comment Share on other sites More sharing options...
Don Richard Posted September 21, 2012 Share Posted September 21, 2012 Simple explanation: the throat size of a conventional exponential horn depends on driver characteristics, operating frequency, back chamber volume, flare rate, and mouth size, among other things. The general idea is to load the front and rear of the driver diaphragm equally, or as close to that as possible. There are equations from PWK, Marshall Leach, D.B. Keele and others that give numerical answers relating to horn design. A quick Google will tell you all you need to know about horn design, and then some. Quote Link to comment Share on other sites More sharing options...
Guest " " Posted September 21, 2012 Share Posted September 21, 2012 the area of the throat slot changes the "point source" of the sound waves. No slot results in the wave propagation beginning right at the woofer cone......this is not a good thing since the waves will start bouncing around the horn very early an a lot of acoustical energy would be lost. By shrinking the area of the slot.....the point source moves forward...and the correct slot area will result in the wave propagation being uniform with the horns expansion rate ....minimizing wave cancellation due to less refraction of sound waves. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted September 21, 2012 Share Posted September 21, 2012 THT? Quote Link to comment Share on other sites More sharing options...
moray james Posted September 21, 2012 Share Posted September 21, 2012 Wow that's interesting but I don't get how using the knife helps to get the ketchup out of the bottle?All kidding aside I at least would very much appreciate more such discriptions of how and why things are the way they are. The more you have to share the better. This discription makes me think in terms of squeezing a baloon to manipulate its shape toget it to fill the horn, thanks. Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
moray james Posted September 21, 2012 Share Posted September 21, 2012 to mustang guy: no front loaded, a tapped horn has one side of the driver firing into the throat and the other side firing into the mouth (more or less). Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
mustang guy Posted September 21, 2012 Share Posted September 21, 2012 to mustang guy: no front loaded, a tapped horn has one side of the driver firing into the throat and the other side firing into the mouth (more or less). Best regards Moray James. This is true; however, in tapped horn arrangements I have seen, the throat is fed by a driver facing 90 degrees to the start of the horn, and the back of the driver is facing toward the mouth, which has a much higher area than the rear of the driver. In the transparent image above, you can see how the THT fires at 90 degrees into the throat. When horn loaded speakers I have seen fire directly at the throat, there is a slot. I don't know if this is always the case. I am only remembering it that way. Quote Link to comment Share on other sites More sharing options...
moray james Posted September 22, 2012 Share Posted September 22, 2012 here s an example of a tapped horn where the driver ends up being quite a ways into the mouth but as with all tapped horns one side of the driver loade the throat and the other side loads the mouth of the horn. Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
djk Posted September 22, 2012 Share Posted September 22, 2012 "This is of course a common feature of MF/HF horns-the "compression throat", but I have not encountered it in the literature as being desirable on bass horns. Comments? " Depends on what you're doing. In general, maximum efficiency in the bass comes with a 1:1 ratio, although this is seldom seen. Higher ratios are an attempt to get better bandwidth on the top end, and higher efficiency up there (we might be talking only 800hz for the high end here). Hornresp (McBean) allows you to model this with ease. I generally start with 2:1 ratios and go from there, higher ratios looking for more for more top end, lower ratios for bass (and trying to avoid the cone crushing seen with higher ratios). Formulas from DB Keele and WM Leach are the usual suspects: http://www.xlrtechs.com/dbkeele.com/PDF/Keele%20%281977-05%20AES%20Preprint%29%20-%20LF%20Horn%20Design%20Using%20TS%20Paras.pdf http://users.ece.gatech.edu/mleach/papers/HornPaper/HornPaper.pdf http://www.hornresp.net.ms/ (free program) Quote Link to comment Share on other sites More sharing options...
mustang guy Posted September 22, 2012 Share Posted September 22, 2012 here s an example of a tapped horn where the driver ends up being quite a ways into the mouth but as with all tapped horns one side of the driver loade the throat and the other side loads the mouth of the horn. Best regards Moray James. In your drawing, the back of the speaker is firing at 90 degrees to the horn just like the front. I'm not trying to reinvent the wheel here. I'm just saying that speakers with vertical firing drivers and having no slot does not neccesarily correlate to a driver firing directly into a horn with a slot. It seems like the idea is to not change the horn aspect from small to large. If a guy cut a 14" round hole on the motorboard of a Lascala, and did some measuring and listening, he could at least know if it's better or worse. Another reason PWK might have used a slot on the LS, it so sound waves coming from the speaker hit that wedge (Which is a sort of brace) and move away from the driver, whereas having a driver firing at the back wall caused some resonance problems. Who knows??? If that is the case, then why to Danley and Fitzmaurice and others fire drivers right at walls? I think I will post this question on BMF's forum, and see what he says about this. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted September 22, 2012 Share Posted September 22, 2012 The wedge in the throat improves the high frequency response of the horn. I believe the early Khorn and EV Georgian bass horns didn't use the throat splitter. Quote Link to comment Share on other sites More sharing options...
boom3 Posted September 22, 2012 Author Share Posted September 22, 2012 thanks for all the replies. I have seen examples of what I'm speaking of, but they're not coming to hand readily.......................................................................... Let me restate: I'm not talking about the slot in the motor board. I am asking about a throat that starts out the same size as the slot, then narrows somewhat before starting the expansion.............................. Safari does not do hard returns so I added padding dot leaders to set off my restatement. Thanks. Quote Link to comment Share on other sites More sharing options...
moray james Posted September 22, 2012 Share Posted September 22, 2012 a horn generally expands at a given rate and if that rate reverses they you are going to get reflections which is a bad thing. Perhaps you are thinking of horns which have a cavity (compliance) on either side of the driver prior to the throat of the horn? Best regards Moray James. Quote Link to comment Share on other sites More sharing options...
boom3 Posted September 23, 2012 Author Share Posted September 23, 2012 a horn generally expands at a given rate and if that rate reverses they you are going to get reflections which is a bad thing. Perhaps you are thinking of horns which have a cavity (compliance) on either side of the driver prior to the throat of the horn? Best regards Moray James. yes, this may be the answer. The Jensen Imperial (among others) has a cavity between the rear of the driver and the horn that acts as a low-pass filter. In a front loaded horn with a sealed back chamber for reactance annulling, a similar cavity (restriction) at the throat would act in the same way. However, why one would want to restrict the response when it is hard enough to get 4 octaves out of a folded bass horn is a mystery, to me at least. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.