Hello fellow diy'ers
I'm currently looking intobuilding a pair of fully hornloaded tops to match my ROAR15's, at my disposal I have a pair of Beyma liberty 8 (12E120) and a pair of FaitalPro HF206 converted to HF146 by removing the 2" adaptor housing, mounted on 18-sound XT1464.
Crossover to the ROAR15's will be between 120-150hz, so I'm aiming for a 130hz cutoff on the mid/bass horn for the 12", and I'm also aming to cross over to the 1,4" at around 1kHz, the higher the better, so the question is, is this possible? and what would be the best way to go about it while keeping it diy friendly?
My gut feeling tells me I should avoid any bends in the horn path, and something also feels right about not having a to narrow begining and go for no less than 1/2Sd, 2/3Sd or thereabouts.
Will be used mainly at home but should be able to keep up with the ROAR15's both in character and SPL if possible.
Any spontaneous suggestions?
I'm currently looking intobuilding a pair of fully hornloaded tops to match my ROAR15's, at my disposal I have a pair of Beyma liberty 8 (12E120) and a pair of FaitalPro HF206 converted to HF146 by removing the 2" adaptor housing, mounted on 18-sound XT1464.
Crossover to the ROAR15's will be between 120-150hz, so I'm aiming for a 130hz cutoff on the mid/bass horn for the 12", and I'm also aming to cross over to the 1,4" at around 1kHz, the higher the better, so the question is, is this possible? and what would be the best way to go about it while keeping it diy friendly?
My gut feeling tells me I should avoid any bends in the horn path, and something also feels right about not having a to narrow begining and go for no less than 1/2Sd, 2/3Sd or thereabouts.
Will be used mainly at home but should be able to keep up with the ROAR15's both in character and SPL if possible.
Any spontaneous suggestions?
seems like too large a range even with an exceptionally low Qes driver. Have you tried finding the upper and lower frequency limits from the T/S parameters?
AES Papers -- Official website of D.B.Keele
11. "Low-Frequency Horn Design Using Thiele/Small Driver Parameters," Presented at the 57th Convention of the Audio Engineering Society, Preprint No. 1250 (K-7), (May 1977).
AES Papers -- Official website of D.B.Keele
11. "Low-Frequency Horn Design Using Thiele/Small Driver Parameters," Presented at the 57th Convention of the Audio Engineering Society, Preprint No. 1250 (K-7), (May 1977).
Thanks for the tip, I'll have a look at where I end up using the formulas, I realize 1kHz may be asking to much, the 130Hz lower cutoff is a must though, and that will determine how low I need to cross over the HF146, for home use i guess down to around 800Hz would be ok.
I do have the option of using the 2" adapter housing and mount the HF206 (which they will then become) on a JBL2386 2" horn, not sure that would make any difference though, except in sound signature, both horns should be fine to use down to about 800Hz.
I do have the option of using the 2" adapter housing and mount the HF206 (which they will then become) on a JBL2386 2" horn, not sure that would make any difference though, except in sound signature, both horns should be fine to use down to about 800Hz.
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if a conventional reactance annulling rear chamber doesn't let you get low enough you can try porting the rear chamber. This usually results in less sensitivity in the reflex operating region compared to the front horn operating region so will need some EQ.
For extended HF you also need to consider the throat diameter (which may differ from that calculated for optimal efficiency from the Keele papers) and may also want to add a phase plug to reduce the compression chamber volume and perform path length equalization. There is some good practical info here:
Graeme's DIY pages
For extended HF you also need to consider the throat diameter (which may differ from that calculated for optimal efficiency from the Keele papers) and may also want to add a phase plug to reduce the compression chamber volume and perform path length equalization. There is some good practical info here:
Graeme's DIY pages
Really good information kipman725, thank you very much!
I'm trying to define all my rolloff corners as per below to see roughly where the Beyma 12E120 has its limits in use as horn driver.
Fhc - upper roll off corner (-3dB) frequency due to the effects of front cavity compliance acting alone.
Fhm – upper roll off corner (-3dB) frequency due to the effects of driver movlng mass acting alone.
Fhs – upper frequency bound of the driver’s resistance controlled region when operated In free air.
Fhvc – upper roll off corner (-3dB) frequency due to the effects of driver voice coil inductance acting alone.
Two of these are really easy to get, Fhs and Fhm, for the other two I need to dig a bit deeper and start to define some design constraints.
As for reactance annulling (air mass, driver suspension and rear cavity) it is mainly to increase the efficiency near the lower cutoff frequency, can this be applied even in my case seeing as I do not aim to design a traditional bass horn, my aim is 130Hz, even if the driver might allow me to go lower.
I was under the impression that porting the rear chamber just below the lower cut-off served to keep the excursion in check and as as you say, add a bit more below the cut off, however that contribution will be phase shifted which may act negatively in a cross over region.
I'm trying to define all my rolloff corners as per below to see roughly where the Beyma 12E120 has its limits in use as horn driver.
Fhc - upper roll off corner (-3dB) frequency due to the effects of front cavity compliance acting alone.
Fhm – upper roll off corner (-3dB) frequency due to the effects of driver movlng mass acting alone.
Fhs – upper frequency bound of the driver’s resistance controlled region when operated In free air.
Fhvc – upper roll off corner (-3dB) frequency due to the effects of driver voice coil inductance acting alone.
Two of these are really easy to get, Fhs and Fhm, for the other two I need to dig a bit deeper and start to define some design constraints.
As for reactance annulling (air mass, driver suspension and rear cavity) it is mainly to increase the efficiency near the lower cutoff frequency, can this be applied even in my case seeing as I do not aim to design a traditional bass horn, my aim is 130Hz, even if the driver might allow me to go lower.
I was under the impression that porting the rear chamber just below the lower cut-off served to keep the excursion in check and as as you say, add a bit more below the cut off, however that contribution will be phase shifted which may act negatively in a cross over region.
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Thanks freddi, I'm familliar with the design, it was one of the first ones I came across when having a look around prior to posting here, wery nicely documented incl. meassurements.
I'm sure it is a correct design execution, the results confirm it, yet I felt the rather narrow start area makes me think that you sort of strangle the driver, this lead to my inial atatement concerning the start area to be somwhere around 1/2 to 2/3 Sd or thereabout, but I'm not sure thos is correct.
What does the start area mean for the rest of the horn, and what does it mean for the performance if keeping it small or large compared to Sd?
Is it simply a matter of a start and end area ratio to be kept for a given length, and that a smaller start area means a smaller aperture, but at some cost for the overall smalller size of the horn? (there usually is).
I'm sure it is a correct design execution, the results confirm it, yet I felt the rather narrow start area makes me think that you sort of strangle the driver, this lead to my inial atatement concerning the start area to be somwhere around 1/2 to 2/3 Sd or thereabout, but I'm not sure thos is correct.
What does the start area mean for the rest of the horn, and what does it mean for the performance if keeping it small or large compared to Sd?
Is it simply a matter of a start and end area ratio to be kept for a given length, and that a smaller start area means a smaller aperture, but at some cost for the overall smalller size of the horn? (there usually is).
The Inlow horn was designed for an 8" driver. I would cut it short to get the same compression ratio for a 12" - since that is basically what was done with the horns I got at the beginning of this year from a member here (found out today🙂 ) for a 15" driver. I am planning an extension back to using 8PE21s in them. I also have a pair of Liberty 8 and I am putting a Paraflex type enclosure for them together just now, only the top needs to be glued on at the moment. It should be a quite good alternative to a horn. I will definitely try am adapter on the horns for Liberty 8 to find out which one sounds the best. Synergy horn above that. I had some homemade JBLclone midbass horns with bass reflex and that midbass kick was something to die for - they were only simply too large with 60 Hz low end limit.
Hmm, shorten a horn and while the Sd/St = 1, it's not the same compression ratio due to the changing flare frequency.
Not Sd/St = 1, but Sd/St = constant. I thought compression ratio was Sd/St. You are certainly right - cutting off at the throat is different from cutting off at the mouth. I need to see in Hornresp, how much difference it will make - I hope I can extend the throat somehow and still get some good results with the 8" and 12"
I'm sorry to say I gave up on this, instead I'm now trying my luck with a far more conventional approach of 15"1,4" sealed top using a 15NDL88, sorry.