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drboar

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Posts posted by drboar


  1. I have been playing around witha LS type bass horn. The throat extends into the dog house and the driver is a 12" But it is still a short bass horn with the same mouth area as a LS. In my horn at least the basic response is set by horn lenght and mouth area. Different flares and chamber sizes does not make a big difference. These things can be used to change the knee above the high pass drop off.


  2. That is cool looking horns, :)

    I have some plans to build curved La Scala type horns, I do not know if the sound will differ but as modeled in HornResponse, the actual horn shape (within reason) have minor effects on the modeled response. So with a set lengths mouth size and throat then changing the curvature and chamber size mostly change the roundness of the knee at the high pass frequeny.

     

    BTW, do you have any ideas why 4 x 8" sounds cleaner than one 15"?


  3. Regarding corner reflectors. I did some experiments on vintage horn "Kuben" very similar to but not inspired by the LaScala. I tested a slew of drivers and adding corner reflectors (attached by double sided tape) was beneficial to some driver, harmful for some and, did nothing for others. Above 300Hz cone breakup causes different effective pathdifferences for different drivers (I assume) and the complex bouncing around can either add up or substract with or without those reflectors. An optical reflector like a mirror is easy to grasp but accoustic reflectors does not behave in quite the same manner.

    Vibrations in the sidewalls is a problem If I was to build them with no braces I would work with laminating two different materials rather than doing brute force things like 30mm MDF.


  4. Calculate

    1.the chamber volume

    2. Horn lengh

    3. Mouth area

    4. Throat area

    Play around in horn response and you will discover that flare does little to change the bass. Parabolic section, conical, exponential or hyperbolic change some few dB and the roundness of the high pass knee. The chamber volume changes that roundness to. The low pass frequency is determined mainly by lenght of the horn and the unevenness/"peakyness" of the response is set by mouth area and radiation angle. Curvature and implementations of slots and bends will affect the real life low pass response but will do little in the bass response.

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  5. I tried out corner reflectors (Kuben in diyaudio forum) and the result varied with different drivers. I expeced the reflectors to allways improve things but it did not. My guess is that there was different breakup pattern in different drivers so different phase shift was introduced already on the way into the horn. The shift in phase beaviour with the added reflectors could then be benefial or harmful interference.


  6. I have seen other horns (Jericho 08) that use a small internal helmholtz resonance chamber to flatten the horn response. Outside the first flare section between the dog house and the back wall there are two unused closed spaces. Have anyone tried to use them as IHR and reduce the LS peak at about 150 Hz?

    In a PA setting it would make more sense to EQ it and keep the radiation resistance but in a domestic setting, why not trying to tame the peak?


  7. I have been playing around with various flares of a LaScala type horn. That is a horn about 1 m long and a mouth area close to 0.36 m2 Different flare shapes like exponential, hyperbolic and of different flare rates as well as chamber volumes from 30 to 80 liters. At least to HornResponse the differences seems small. The overalll horn response is set by mouth area and length not the exact flare (within reason) The chamber volume can be reduced to produce a sharper knee at the low pass and also reduce cone motion below the bandpass of the horn. I have my own ideas about making a La Scala light version with a curves and a twist added to it. LaScala does not have bass below 50 Hz but there is something about the slam of a large mouth horn...


  8. I had my DIY Klipsch Corner Horns in solid concrete corners and had good bass down to about 40 Hz. In my next home the side walls was still was concrete but the wall behind the horns were drywall. I lost about 8 db below 100 Hz, I was thinking about bracing the wall but then other factors came into play and I had to scrap the horns. If you corner load the K-horn with flimsy walls you will get nowere near the bass the horns offer.


  9. In a high Q closed box the bass can be extended and the peak tamed with addition of a serial cap

    Posted Image

    The cap increase the impedance above the resonanse frequency (reducing ht ehigh Q hump) and lowers impedanse below resonanse (increasing output)

    Posted Image

    This is a KEF B200 with a Q of 1.0 to 1.1 in this box

    A horn similar to the La Scala also is a closed box with a high Q. Adding caps do increase and decrease the impedance as they should using a Eminence PA driver

    Posted Image

    And then the proof of the pudding

    Posted Image

    What the heck? Is it the higher Q or is it something intrinsic in hornloaded boxes that precludes the use of serial caps to extend the bass?


  10. I had the impression that the lower the Q the better for a horn driver

    I have "Kuben" something that looks simlar to a La Scala but with in my case 12" drivers.

    Posted Image

    The drivers were measured using Omnimic at 50 cm distance with the horn on a chair in the middle of the room. Same voltage in all measurements

    Black trace is a Beyma G320. A real horn driver with a Q of below 0.25 and Fr of about 60 Hz

    Red trace is a Eminence driver Q of 0.5 and Fr about 50 Hz

    Brown trace is vintage Gamma LA1232. Fr 25-30 Hz Q 0.4 and Vas = 300 liter it should be unsuitable as a horn driver and have a mass rollof above 150 Hz or so.

    In a PA setting the Beyma is vastly superior to the Gamma with 10 dB higher sensitivity and better power handling as well. Hower, if we compare the -10 dB point relative to the averege 200-1000 Hz output the Beyma reach -10 dB at 90 Hz while tha Gamma has this point at 55 Hz.

    Posted Image

    It does appear that suitable Q in horn is a matter of application and that mass roll off and bass horns not allways match up


  11. I agree with the previous post. A timedomain EQ can not fix everything in a passive loudspeaker. In the ranges were only one speaker contribute or at least much more than the other ones say 20 dB it is possible to time EQ. For example 10-20 kHz were only the tweeter is working.The problem is in the crossover region were two drivers are working perhaps around 5 kHz were both midrange and tweeter is contrributing. what every delay you will have at 5 kHz will only fit one of them.

    I have built speakers with passive crossovers since the late 70s and recently bought some second hand active crossovers. It such a joy to be able to adjust xover and level by turning a knob. I might use som passive crossovers but my guess in going forward to miniDSP is more likely than back to passive.


  12. Real corners are important. I had DIY Klipsch corner horns in solid concrete corners and then moved and then had the side walls still in concrete but the back wall fof the horns in plaster board I lost something like 6 dB below 80 Hz, so true corners and sturdy corners is a must for decent bass.


  13. I realised if I do the talk I better walk as well[H]

    This is the setup with the horn set against a back wall. XTZ Room Analyser II connected to my macbook (with WinXP in Bootcamp). Microphone is center line about 70 cm in front of horn opening.

    The driver in the back is the Beyma G320 (Fr= 52 Hz and Qes= 0.2) built to be a horn driver. The other is a Fane Crescendo 80W Silmilar Fr but a Qes of about 0.5

    Posted Image

    Starting with the Beyma horn driver With no reflector(green) and then adding the bisector in front of the driver (blue),not much happens below 1 kHz

    Posted Image

    Adding corner reflectos add some dB jsute below 1 kHz and a huge bump around 2 kHz

    Posted Image

    Adding both the bisecting reflector and the corner reflectors, brings us back at square one!

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    Here we have the impedance plot Dayton Woofer Tester 3. System resonance at 77 Hz and medium Q value of 0.8 Note the gently sloping response below 200 Hz

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    Turning to the Fane driver with a higher Q adding a bisector. Note the hump in the bass just above the HP. Here there is about 4 dB added both at 400 and 900 Hz by the reflectors

    Posted Image

    Then adding both (I missed measuring just the corner reflector) Either some few dB added 200-800 Hz by te reflectors (blue) or back to square one

    Posted Image

    Impedance plot show a Fr 10 Hz lower and higher Q of 1.4

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    Tossing in a Vintage driver with a Fr of 30 Hz Qes of 0.4 and Vas of 300 Liters! The setup is different the green line is tha Beyma and the green is the vintage driver that is a theoretical mass rollof of 150 Hz but a practial one is this case of 1200 Hz

    Posted Image

    The images are cropped for some reason.

    The system with this driver has a Fr of 67 Hz and a Q of 1.4 suggesting having a low Fr higher Q driver might be better than adding ports and stuff. I also note that Klipsh original driver is far from the classical horn driver of say 50 Hz an a Qes of 0.2


  14. Modeling vs measurement.

    I have a horn similar to the LS and to my surprise the low pass is way higher than calculated byt the mass rolloff.

    See my blogg at "http://drboar.blogspot.se/"

    Do note that a classical horn driver like the Beyma falls below 100 Hz using "worse" drivers with lower Fr and higher Q gives more bass output but also a hump at the high pass band

    Corner reflectors:

    I added both corner reflectors as well as a reflector in front of the driver. Attached by double sided tape

    I tried no 1. No reflector 2. Just in front of driver 3. Just corner reflectors 4. Both infront and corner

    I expected the effect to be additative 1 worst 2&3 better and 4. Best. Not so, it varied with the driver what combinations that worked best!

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