come to think of it, that 15" woofer horn had an offset driver with an offset (from the center of the cone) port, so maybe the thread will be of interest
Companion Woofers for my Synergy Horns
Companion Woofers for my Synergy Horns
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Yes I agree. That is my plan too. I'm planning on using an Othorn below my synergy for a point source from 20-20 000hz. My horn has directivity down to ~200hz, and I'll crossover from 120hz so they stay within 1/4h WL. In room you only need directivity down to ~200hz so I'm good. Below are the measured polars (not the best environment for such a measurement, but definetely better than the K402 measured in the same circumstances)
Note: Attachments removed at the request of the member.This is a great thread...thx to all contributors !
It is helping to clarify things nicely..
FWIW, at infocomm several weeks ago, I was able to ask Tom D a few questions about synergy's in general, and the build I hope to make in particular.
When I told him I planned to use a 4594 CD down to 500Hz, he said that with care, I should probably be able to use a 12".
It is helping to clarify things nicely..
FWIW, at infocomm several weeks ago, I was able to ask Tom D a few questions about synergy's in general, and the build I hope to make in particular.
When I told him I planned to use a 4594 CD down to 500Hz, he said that with care, I should probably be able to use a 12".
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ok, I have had a look at my horn again, and if I make some room (aka increase the height/size of the box) I can place the woofers on the other (lower and upper instead of side) walls, and make an corner located elongated slot that runs through the center of the 15" woofer. Using a 500hz crossover will allow using the 15" as 528hz is 1/4th WL of actual cone radius of a 15"er.
That begs the question if I do need this. Considering I didnt actually consider the lowered SPL of the compression driver.
A JBL 2446 (the one I'm using now) has a RMS SPL of ~135dB, and I was hoping to match that down to at least 100hz. Using 4 woofers (reason why I'm asking the cone vs port offset) would only require 123dB/woofer considering they would couple. Using only 2 requires 129, something which is considerably harder.. Of course, if the compression driver loses 10Db I'd only need to match down to 125dB which I would already achieve with 2x 15" woofers.
That begs the question if I do need this. Considering I didnt actually consider the lowered SPL of the compression driver.
A JBL 2446 (the one I'm using now) has a RMS SPL of ~135dB, and I was hoping to match that down to at least 100hz. Using 4 woofers (reason why I'm asking the cone vs port offset) would only require 123dB/woofer considering they would couple. Using only 2 requires 129, something which is considerably harder.. Of course, if the compression driver loses 10Db I'd only need to match down to 125dB which I would already achieve with 2x 15" woofers.
Interesting.. THe 4594 has a lot of power. How much 12" woofers were you talking about? And down how low? And were you aiming for a 0dB difference between the 4594 and the total of the 12" or..?
Its always better to have more woofers. At Xmax, they have considerable THD and its audible. So if you are going to operate at those levels, go with 4 woofers independent of the CD sensitivity.
Reinforcing that point, CD distortion at HF is less audible. At some point, the harmonics are ultrasonic and can't be heard. With constant directivity roll off, you have to drive the CD harder, the higher you go in frequency to maintain a flat response. But that isn't as much of an issue since the harmonics are too high in frequency to be heard. (of course you would still be vulnerable to IM)
Also, you shouldn't expect fundamental music content all the way up to 20 Khz. The response needs to be there to support the harmonics produced by the instruments which will be at reduced amplitude.
I would recommend measuring the CD on the horn to know its sensitivity and need for EQ instead of guessing and then only matching sensitivity up to 10 Khz or so.
This rationalization falls apart if you are going to be operating in very large venues where the air itself acts as a low pass filter.
I'm planning on using two 12"s crossing over to separate subs at 100Hz.
RCF mb12n351's or 405's. I've used a pair of both of these drivers with the 4594, and maximum output matches up well. But they are pretty ballzy as far as 12"s go.
Ime, once past low-mid 130's spl, the pristine clarity starts to give way...despite the specs....for both the CD and the 12"s.
As far as sensitivity, with a 16 ohm 4594, and two 8 ohm 12"s in parallel, the CD needs about a 5-6dB pad (on both sections) for flat tuning.
I'm modelling it for outside use, so.. the lowpass cancels out the lesser noticeable distortion?
Thanks man. Love the straight to the point and problemsolving answers! I'm not audio educated so I try to teach myself everything. People like you are exactly what I'm looking for.
Pretty cool! They match out indoors (1pi or even 2pi)? Or rather 0,5 pi? Also, you mean pristine up to 135dB?
What kind of crossover did you use between woofers and CD?
That's very consistent with the 1/4 WL recommendation.
Nice to have another data point.
Best wishes
David
It's a large "bi-radial" horn based on the K402, designed by Omholt and Don Keele. I have the first pair ever build (the actual prototype).
They will not be sale to the DIY community, as they will be sold as a complete unit together with a brand new midbass horn.
The sales pitch for the K402 emphasises that it's not bi-radial, so it's not clear to me what you mean.
A bi-radial horn based on more-or-less the opposite?
Can you post a picture?
If no picture then could you describe it compared to a JBL 2360?
That's more what I had in mind, bi-radial, about the same size, and in the Don Keele tradition.
Best wishes
David
Yeah, I must admit I'm not really able to describe the horn, as Omholt (whom I bought it from) doesnt want to share it. I just know he himself did call it a bi-radial, inspired and designed to improve on some of the weaker points of the K402.
Figuring out hornresp specs
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Cant figure out if I'm doing this right, and is it is very relevant to this thread: a 12" driver has an Sd of around 540cm², so a with a 10:1 ratio I need a port area of 54cm². Using a 1" wide rectangular port, I would need a port of 20cm.. Or 2x 10cm slots. This does sound very long.. am I doing something wrong?
Also, would it be a dumb idea to use a slot that is wider, lets say 1,5"?
Also, would it be a dumb idea to use a slot that is wider, lets say 1,5"?
Thanks to some of the good recommendations and rules of thumb I'm going to "settle" on a design with a 650hz acoustic crossover, keep it sealed and make the ports to be able to 1: be used with a single 15"er (with each its own symmetricaly placed 2 ports) AND 2: 2x 12"ers (with 1 centraly located port each). Those ports would be identical for both single 15" or double 12". This would mean a 1:10 ratio for the 2x12" setup, and 1:12 ratio for the single 15" setup.
For 15"'er I'm thinking about using the Em Kappa 15C I have now, although it's not perfect. Probably gonna upgrade to a Em Delta PRO 15 which will result in 122,5dB @100hz (at Xmax value). Double woofers results in 128,5dB. This is definitely not as much as I'd hoped, but it's still one of the best woofers I can find. There are some RCF and Beyma (and other brands probably too) midbas s15"'ers that model better, (125dB at 100hz, Xmax) but they are already rolling of at 150hz, and their response below 100hz is abominable. I will have to relook at all those woofers, cause when coupling to my subs directly below it (for example, an Othorn that is within 1/4WL of 120hz) I can go for a 120hz -6dB point, instead of 100hz 0dB. 120 -6dB which will be very favourable to the RCF midbass woofers.
In home I'll have corner loading and adjusted PEQ/lower crossover due to way lower SPL necessity, so the MIDbass woofers with their higher rolloff might just do the trick in home too.
When using 4x 12" (so 2 on each side) woofers I can definitely achieve way more high SPL due to the +6dB of coupling vs 2x 15". They will roll-off way sooner than the 15" , but as stated above, this is not necessarily I thing I need to really worry about.
The Eminence Delta PRO 12A can achieve 117dB (100hz, Xmax limited), and has decent response below, the RCF MB12N405 one you guys recommended earlier here rolls of way sooner, but has a 118,5dB (100hz, Xmax limited). I think if I look at some more 12" woofers I can definitely find some ideal mid-bass woofers that can do even better (definitely if I specifically look for 120hz -6dB responses).
For 15"'er I'm thinking about using the Em Kappa 15C I have now, although it's not perfect. Probably gonna upgrade to a Em Delta PRO 15 which will result in 122,5dB @100hz (at Xmax value). Double woofers results in 128,5dB. This is definitely not as much as I'd hoped, but it's still one of the best woofers I can find. There are some RCF and Beyma (and other brands probably too) midbas s15"'ers that model better, (125dB at 100hz, Xmax) but they are already rolling of at 150hz, and their response below 100hz is abominable. I will have to relook at all those woofers, cause when coupling to my subs directly below it (for example, an Othorn that is within 1/4WL of 120hz) I can go for a 120hz -6dB point, instead of 100hz 0dB. 120 -6dB which will be very favourable to the RCF midbass woofers.
In home I'll have corner loading and adjusted PEQ/lower crossover due to way lower SPL necessity, so the MIDbass woofers with their higher rolloff might just do the trick in home too.
When using 4x 12" (so 2 on each side) woofers I can definitely achieve way more high SPL due to the +6dB of coupling vs 2x 15". They will roll-off way sooner than the 15" , but as stated above, this is not necessarily I thing I need to really worry about.
The Eminence Delta PRO 12A can achieve 117dB (100hz, Xmax limited), and has decent response below, the RCF MB12N405 one you guys recommended earlier here rolls of way sooner, but has a 118,5dB (100hz, Xmax limited). I think if I look at some more 12" woofers I can definitely find some ideal mid-bass woofers that can do even better (definitely if I specifically look for 120hz -6dB responses).
Interesting horn pictures. Can't tell how flat the inner sides are. I guess we can credit the slot at the apex for the exemplary polars but the depth of the round to rectangular adapter in back concerns me. It seems it would consume a large part of the 1/4 wave reflection distance budget.
Re' 54 cm2 yes that sounds reasonable. area matters, shape doesn't or not so much. Use whatever works best in the physical design.
Look at the Acoustic Elegance website for very smooth, linear 12" and 15" woofers with 14 mm of Xmax. They probably cost 2x what Eminence costs but they are worth it if you have the budget.
Re' 54 cm2 yes that sounds reasonable. area matters, shape doesn't or not so much. Use whatever works best in the physical design.
Look at the Acoustic Elegance website for very smooth, linear 12" and 15" woofers with 14 mm of Xmax. They probably cost 2x what Eminence costs but they are worth it if you have the budget.
Main design problem is actually the curve.. I have around1-2cm of curve in the middle. Only the first 28cm of wall space are actually flat. A 12"er will have almost no curve, but 15 and 18" some more. I will be filling this up with something (probably some Epoxy) and round out out an area of 1" around the port). I will try to keep the room between the cone and the port as little as possible, and the port length as shallow as possible. My own horn is only 6mm thick so I can achieve a very very shallow port.
I do have the "advantage" of starting with what I have, and upgrading later. Money isnt an issue as I will just have to wait a bit longer, as I will not be cutting costs anywhere on this project (for example, I'm looking for a TAD or other Be driver). AE looks to be the best around but I didnt find any good pics, although that was when I wasnt looking at the Xmax limited SPL yet, so thanks for reminding me!
I do have the "advantage" of starting with what I have, and upgrading later. Money isnt an issue as I will just have to wait a bit longer, as I will not be cutting costs anywhere on this project (for example, I'm looking for a TAD or other Be driver). AE looks to be the best around but I didnt find any good pics, although that was when I wasnt looking at the Xmax limited SPL yet, so thanks for reminding me!
Hopefully I can clear things up a bit. It's bi-radial in the sense that it has a diffraction slot, a description that was also used for several JBL horns. Actually JBL never had a true bi-radial horn. Their so-called bi-radial horns were either only radial or curved sides and top-bottom extruded. But they had a diffraction slot.
The correct description for this "Keele & Omholt Tech." horn would be flat front horn; extruded sides and top-bottom with a diffraction slot.
Droco's horns were the first prototypes. The next pair had some modifications with better build, stiffer and a slightly more gradual exit. It measured a tiny bit better on-axis.
The goal was to build a horn that was better than the Klipsch K402 which were used for reference. I believe we achieved that goal after hours of AB testing besides some directivity measurements. The horizontal polars Droco showed (which he wasn't allowed to publish by the way 😉) were indoor measurement where the room contributed. The beam width of the polar of both our horn and the K402 is wider than it actually is. Other than that, they might be quite accurate.
Droco mentioned that the horn would be used in a complete horn system. That may or may not happen. We're working on a second horn now that will be a true bi-radial horn by the strict definition. Or we're calling it a dual radial horn to avoid any confusion. The drawing below isn't the final product by any means but it gives an idea.
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