This sim was for a rectangular flat open baffle. Might be fun to see what an H-frame does. Generally I prefer the flat baffle to get away from the cavity resonances and have move flexibility in the x-o point.
@jhollander said:
This sim was for a rectangular flat open baffle. Might be fun to see what an H-frame does. Generally I prefer the flat baffle to get away from the cavity resonances and have move flexibility in the x-o point.
Would a U frame be a sufficient compromise between the Flat baffle and H-Baffle, goes lower than flat with hopefully lower cavity resonances?
Thanks Craig and John. When I am comparing for resonance in the graphs, its the blue squiggles? What is the yellow squiggle - did not understand Equiv circular baffle with omni source.
The cavity resonance must be calculated based on the cavity dimensions. It is not shown on any of those graphs. The blue trace is the predicted dipole response. You add that to the driver's IEC response, like you would add a diffraction response model.
John's models are top to bottom: 24" H frame, 12" U frame, 24" U frame.
Notice how the response of the 24" H frame and the 12" U frame are identical? Both show 100 dB at 30 Hz at xmax. Their dipole peak is at 200 Hz, so you can low pass them at 200 Hz and maintain constant directivity.
The 24" U frame, by contrast, can hit 100 dB at 25 Hz at xmax. However its dipole peak is only at 100 Hz meaning a lower crossover point.
In John's first sim a few posts up, the 24" wide flat baffle can has an even higher dipole peak (~300 Hz) but gives up another 5 Hz of bass extension.
None of this takes into account the cavity resonance which may or may not force an even lower crossover point.
Horn response will calculate the cavity resonances or you can do the math. Math is determine the cross sectional area of the H or U frame. Convert the cross sectional area to an equivalent circle radius R. Find the depth of the cavity D. Find the Effective Length=EL= D + 0.6 x R. Convert to meters. Calculate the quarter wave frequency = 344m/s divided by 4 x EL
Cross below the quarter wave frequency or stuff (Cardioid) to avoid peaking FR.
I must admit that it seems odd/funny to me that there has been literally no mention whatsoever of this buyout Foster planar tweeter. Aside from looking like they'd be a pain to mount, what are some of the reasons nobody cares? https://www.parts-express.com/Foster-E100T10-Ribbon-Tweeter-8-Ohm-279-468
@dcibel said:
It starts to roll off at 6kHz. Recommended crossover at 6.5kHz really limits it's usability.
I'm not seeing the rolloff at 6k (if Fostex's specs are to be believed) but crossing at 6.5k leaves a pretty big hole to fill from a standard midrange up to that 6.5k number. Hello 4-way?
Might be a good tweeter on top of the Dayton Planar, but that puts you North of $80 all-in, and you have to ask yourself what kind of tweeters can be had for North of $80, that also do not result in increased complexity and cost at a crossover level.
I'm not seeing the value in it, to be honest. I mean, it is a cool option - but PE in the last several years has made a habit out of pricing buyout tweeters at ridiculously stupid levels and advertising them more as replacement parts and not DIY stuff. I mean, look at the pricing on those Jensen and Advent tweeters that they are never going to sell out of. Even the Ariel buyout tweeters are priced at $40 - you can buy some pretty badass tweeters for $40! No need for 20 year old NOS stuff. This little planar is a $12 tweeter, lets be honest here. For just a couple bucks more than the $25 Foster you can buy the GRS 3-1/2" planar, and odds are the Foster doesn't measure any better or more consistent between units.
Anyways, rant over. Modern tweeters from Tymphany are priced at such an attractive point that I don't see the need to wish for better buyout options. I sure miss the great buyouts, but I don't expect PE to continue the "buy a metric fuckton from a distressed company and price them to sell out in two weeks" approach any time soon.
@jr@mac said:
I sure miss the great buyouts, but I don't expect PE to continue the "buy a metric fuckton from a distressed company and price them to sell out in two weeks" approach any time soon.
Man I miss those deals too
Regarding the Foster planar... I know my alternate suggested tweeter is another $10 higher, and we DIY guys tend to be tight wads, but the RT1.3WE bests it in every way other than price. The RT1.3WE can be crossed an entire octave lower, it has a nice DIY friendly round faceplate (nice looking too), and it measures extremely well and sounds fantastic.
The more I think about it, the more I am starting to believe the Dayton DMA 4" might be the killer budget midrange of all time. I wish it had a round frame, but that is really the only thing (on paper) I can fault. On the plus side, it shares dimensions with one of the Beston ribbons.
@jr@mac said:
The more I think about it, the more I am starting to believe the Dayton DMA 4" might be the killer budget midrange of all time. I wish it had a round frame, but that is really the only thing (on paper) I can fault. On the plus side, it shares dimensions with one of the Beston ribbons.
I thought I had a pair of the DMAs, but can't find them now. Has anyone run a THD measurement on them?
But Chahly - Stahkist don't want speakers that look good, Stahkist wants speakers that sound good!
Comments
It doesn't have the prettiest backside, does it?
Not bad 100 dB 2pi at 35 Hz.
U Frame? H Frame? Does ABC baffle calculate for OB?
Super tempting for OB design, but jeez, my shelves are overflowing as it is....
This sim was for a rectangular flat open baffle. Might be fun to see what an H-frame does. Generally I prefer the flat baffle to get away from the cavity resonances and have move flexibility in the x-o point.
Would a U frame be a sufficient compromise between the Flat baffle and H-Baffle, goes lower than flat with hopefully lower cavity resonances?
H frame would have less cavity resonance as half the wing depth is in front and the other half is in back.
I had good results with a pair of beyma 12BR70's in a modified H frame (3 way with coaxial)
Craig's right the H frame is a better compromise. U frame gives the best bass loading in the same depth at the sacrifice of the cavity resonance.
H frame with 24 inch depth, U frame with 24 inch depth and 12 inch depth
Thanks Craig and John. When I am comparing for resonance in the graphs, its the blue squiggles? What is the yellow squiggle - did not understand Equiv circular baffle with omni source.
The cavity resonance must be calculated based on the cavity dimensions. It is not shown on any of those graphs. The blue trace is the predicted dipole response. You add that to the driver's IEC response, like you would add a diffraction response model.
John's models are top to bottom: 24" H frame, 12" U frame, 24" U frame.
Notice how the response of the 24" H frame and the 12" U frame are identical? Both show 100 dB at 30 Hz at xmax. Their dipole peak is at 200 Hz, so you can low pass them at 200 Hz and maintain constant directivity.
The 24" U frame, by contrast, can hit 100 dB at 25 Hz at xmax. However its dipole peak is only at 100 Hz meaning a lower crossover point.
In John's first sim a few posts up, the 24" wide flat baffle can has an even higher dipole peak (~300 Hz) but gives up another 5 Hz of bass extension.
None of this takes into account the cavity resonance which may or may not force an even lower crossover point.
Thanks Craig - found the dipole peak frequencies and the 100 DB points.
For the cavity resonance, is it measurable or how do you find it and fix it?
Horn response will calculate the cavity resonances or you can do the math. Math is determine the cross sectional area of the H or U frame. Convert the cross sectional area to an equivalent circle radius R. Find the depth of the cavity D. Find the Effective Length=EL= D + 0.6 x R. Convert to meters. Calculate the quarter wave frequency = 344m/s divided by 4 x EL
Cross below the quarter wave frequency or stuff (Cardioid) to avoid peaking FR.
Newark if doing 15% off online orders again.
It's your lucky week!
To celebrate St Patrick's Day we're giving you up to 15% off online orders*
Use Voucher Code: GREEN15
Ron
Can't believe I almost missed it - another lighting apparatus on PE!
Finally something decent.
C'mon, man! Just admit it's another $6 flashlight.
There must be really good money to be made selling flashlights. Wonder what their markup is?
@Tom_S said:
Check the prices for the same items on Aliexpress. Probably also large discounts for ordering in bulk.
This is starting to look more like a flashlight deal thread than a speaker deal thread
illuminating!
I must admit that it seems odd/funny to me that there has been literally no mention whatsoever of this buyout Foster planar tweeter. Aside from looking like they'd be a pain to mount, what are some of the reasons nobody cares?
https://www.parts-express.com/Foster-E100T10-Ribbon-Tweeter-8-Ohm-279-468
It starts to roll off at 6kHz. Recommended crossover at 6.5kHz really limits it's usability.
I'm not seeing the rolloff at 6k (if Fostex's specs are to be believed) but crossing at 6.5k leaves a pretty big hole to fill from a standard midrange up to that 6.5k number. Hello 4-way?
Might be a good tweeter on top of the Dayton Planar, but that puts you North of $80 all-in, and you have to ask yourself what kind of tweeters can be had for North of $80, that also do not result in increased complexity and cost at a crossover level.
I'm not seeing the value in it, to be honest. I mean, it is a cool option - but PE in the last several years has made a habit out of pricing buyout tweeters at ridiculously stupid levels and advertising them more as replacement parts and not DIY stuff. I mean, look at the pricing on those Jensen and Advent tweeters that they are never going to sell out of. Even the Ariel buyout tweeters are priced at $40 - you can buy some pretty badass tweeters for $40! No need for 20 year old NOS stuff. This little planar is a $12 tweeter, lets be honest here. For just a couple bucks more than the $25 Foster you can buy the GRS 3-1/2" planar, and odds are the Foster doesn't measure any better or more consistent between units.
Anyways, rant over. Modern tweeters from Tymphany are priced at such an attractive point that I don't see the need to wish for better buyout options. I sure miss the great buyouts, but I don't expect PE to continue the "buy a metric fuckton from a distressed company and price them to sell out in two weeks" approach any time soon.
Man I miss those deals too
Regarding the Foster planar... I know my alternate suggested tweeter is another $10 higher, and we DIY guys tend to be tight wads, but the RT1.3WE bests it in every way other than price. The RT1.3WE can be crossed an entire octave lower, it has a nice DIY friendly round faceplate (nice looking too), and it measures extremely well and sounds fantastic.
How about that $60 Acoustic Research 1" dome with an Fs of 1.5K?
The more I think about it, the more I am starting to believe the Dayton DMA 4" might be the killer budget midrange of all time. I wish it had a round frame, but that is really the only thing (on paper) I can fault. On the plus side, it shares dimensions with one of the Beston ribbons.
I thought I had a pair of the DMAs, but can't find them now. Has anyone run a THD measurement on them?