Hi, I have checked out Thorsten Loesch's Afterburner files, but I am kind of interested in building a Hammer Dynamics-style box for the Eminence Beta LTA, which I now have on an open baffle while I decide what box to build. My goal for this project is to have a fullrange speaker that has a little more crispness an detail than I am currently getting with the OB, but supplemented by a supertweeter around 7 - 8k and a subwoofer somewhere around 100Hz.
I am not a math person - I am a graphic designer and computer savvy but formulae leave me blinking. I have a table saw and router, and am game to try anything that's not too complex - for example a back-loaded horn is beyond my patience if not skills.
From what I have read the Hammer box is a sort of TL with a pipe tuned to 50Hz (I saw it written somewhere as 500Hz - I think it was Dick Olsher - but I figured that was a typo).
Does anyone have a diagram of the Hammer enclosure they are willing to share just for info purposes? Or would this be considered uncool because it is a proprietary design.
Anybody else explored any other interesting boxes for this driver?
The main reason I like the Hammer box is that it gets the driver up nice and high, unlike the Afterburner, which needs a stand. For WAF purposes, I like the pedestal look.
I am also wondering whether I need the Zobel circuit if I am actively EQing this thing and actively crossing it over for the sub and the tweeter. I am using the Behringer DEQ and DCX 2496es to do so, with Bottlehead Paramour for the mids and miscellaneous solid state amps for the subs and tweeter.
Thanks,
Than
I am not a math person - I am a graphic designer and computer savvy but formulae leave me blinking. I have a table saw and router, and am game to try anything that's not too complex - for example a back-loaded horn is beyond my patience if not skills.
From what I have read the Hammer box is a sort of TL with a pipe tuned to 50Hz (I saw it written somewhere as 500Hz - I think it was Dick Olsher - but I figured that was a typo).
Does anyone have a diagram of the Hammer enclosure they are willing to share just for info purposes? Or would this be considered uncool because it is a proprietary design.
Anybody else explored any other interesting boxes for this driver?
The main reason I like the Hammer box is that it gets the driver up nice and high, unlike the Afterburner, which needs a stand. For WAF purposes, I like the pedestal look.
I am also wondering whether I need the Zobel circuit if I am actively EQing this thing and actively crossing it over for the sub and the tweeter. I am using the Behringer DEQ and DCX 2496es to do so, with Bottlehead Paramour for the mids and miscellaneous solid state amps for the subs and tweeter.
Thanks,
Than
I think the Hammer is a 4 cubic foot box. I thought this pdf from Eminence was interesting re. the 12lta
http://www.parts-express.com/pdf/290-409c.pdf
I think the 2 cubic foot box is interesting if designing the system to include a sub.
Godzilla
http://www.parts-express.com/pdf/290-409c.pdf
I think the 2 cubic foot box is interesting if designing the system to include a sub.
Godzilla
Impressive
Wow, guess Labor Day was the right time to post this query!
Scottmoose, thanks for verifying the Hammer box as a MLTL. Initally, I was at a loss as to how the MLTL differs from a bass reflex box, but a Google search took me to Martin King's excellent explanations of the similarities and differences.
http://www.quarter-wave.com/Project03/Project03.html
http://www.quarter-wave.com/Project04/Enclosure_Design.html
To quote the most relevant of his observations:
"In my opinion, one of the negative attributes of a bass reflex enclosure is that any strong standing wave resonances in the enclosure will not be sufficiently damped. The lack of fiber in the center of the air volume allows energy from the back of the driver to potentially excite resonances and produce unwanted acoustic output that escapes through the port opening. . . . The ML TL enclosure can be thought of as a form of transmission line where quarter wavelength standing waves are used to provide the spring for the mass of air in the port."
Since I want to use this box as the center of of an augmented fullrange system, the MLTL philosophy feels right to me, but I have no idea how to begin calculating
a) The dimensions of the box
b) The dimensions of the port
c) any necessary correction circuits
Regarding the correction circuits, since I am using this speaker in a digitally EQ'd system (I am using a power Mac G4 Cube as a digital signal source, going digital right up to the amp inputs, DACT-style stepped attenuators for volume control) do I need to worry about correction circuits?
Thanks for everybody's input so far.
Than
Wow, guess Labor Day was the right time to post this query!
Scottmoose, thanks for verifying the Hammer box as a MLTL. Initally, I was at a loss as to how the MLTL differs from a bass reflex box, but a Google search took me to Martin King's excellent explanations of the similarities and differences.
http://www.quarter-wave.com/Project03/Project03.html
http://www.quarter-wave.com/Project04/Enclosure_Design.html
To quote the most relevant of his observations:
"In my opinion, one of the negative attributes of a bass reflex enclosure is that any strong standing wave resonances in the enclosure will not be sufficiently damped. The lack of fiber in the center of the air volume allows energy from the back of the driver to potentially excite resonances and produce unwanted acoustic output that escapes through the port opening. . . . The ML TL enclosure can be thought of as a form of transmission line where quarter wavelength standing waves are used to provide the spring for the mass of air in the port."
Since I want to use this box as the center of of an augmented fullrange system, the MLTL philosophy feels right to me, but I have no idea how to begin calculating
a) The dimensions of the box
b) The dimensions of the port
c) any necessary correction circuits
Regarding the correction circuits, since I am using this speaker in a digitally EQ'd system (I am using a power Mac G4 Cube as a digital signal source, going digital right up to the amp inputs, DACT-style stepped attenuators for volume control) do I need to worry about correction circuits?
Thanks for everybody's input so far.
Than
Actually, to be a 'real' BR / vented box requires a uniform air-particle density in the enclosure and no standing waves present. The transition from BR to MLTL /MLQWR occurs when standing waves present in the enclosure necessitate a change in vent tuning over what a pure helmholtz / reflex design states is needed.
Either way, I warned you it'd need to be big, right? Large mid-Q driver with a relatively high Vas = a big box.
Here's two; top = max-flat alignment; 48in, 400in^2 CSA, Zd = 21.375in, Zp 45in, vent = 6in diameter x 0.75in long. Line top, back & one sidewall 1in acoustic fibreglass or similar & adjust this & vent length to suit your own requirements. Bottom = borader-band PA style alignment tuned to Fs, Vp = Vas (rounded up slightly) 48in, Zd = 19.25in, CSA = 174in^2, Zp = 45in, vent 6in diameter x 4in long, same damping.
Either way, I warned you it'd need to be big, right? Large mid-Q driver with a relatively high Vas = a big box.
Here's two; top = max-flat alignment; 48in, 400in^2 CSA, Zd = 21.375in, Zp 45in, vent = 6in diameter x 0.75in long. Line top, back & one sidewall 1in acoustic fibreglass or similar & adjust this & vent length to suit your own requirements. Bottom = borader-band PA style alignment tuned to Fs, Vp = Vas (rounded up slightly) 48in, Zd = 19.25in, CSA = 174in^2, Zp = 45in, vent 6in diameter x 4in long, same damping.
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Scottmoose, I don't understand any of that!Sorry . . .
Translation:
For the upper FR trace, the box is 48" tall, and 400 square inches in cross section (20 x 20, or some other dimensions to make the same area). The driver is centered 21-3/8 in from the top. The port is centered 45 inches from the top, and is 6in diameter x 0.75in long (i.e. a 6" hole in the front of the box, the thickness of the plywood is the length of the port). Big box indeed!
For homework, translate the specs for the other version!
Let me rephrase that . . .
Scottmoose, thanks so much for running the 2 simulations. I understand the response curves, but your 2 box specs use terms I'm not familiar with:
Curve 1:
48in, -- I assume this is height
400in^2 CSA -- Not sure what this references - Cross section of something?
Zd = 21.375in -- Depth? Acoustic impedance of something?
Zp 45in -- ? Acoustic impedance of the port ? Not sure . . .
vent = 6in diameter x 0.75in long -- Got it
Curve 2:
PA style alignment tuned to Fs -- Okay, makes sense
Vp = Vas (rounded up slightly) 48in, -- Port volume = 48 inches? 48 cubic inches?
Zd = 19.25in, -- Not sure
CSA = 174in^2, -- ??
Zp = 45in,
vent 6in diameter x 4in long, same damping. -- Got it
Thanks for your effort - sorry I don't totally understand the result.
Scottmoose, thanks so much for running the 2 simulations. I understand the response curves, but your 2 box specs use terms I'm not familiar with:
Curve 1:
48in, -- I assume this is height
400in^2 CSA -- Not sure what this references - Cross section of something?
Zd = 21.375in -- Depth? Acoustic impedance of something?
Zp 45in -- ? Acoustic impedance of the port ? Not sure . . .
vent = 6in diameter x 0.75in long -- Got it
Curve 2:
PA style alignment tuned to Fs -- Okay, makes sense
Vp = Vas (rounded up slightly) 48in, -- Port volume = 48 inches? 48 cubic inches?
Zd = 19.25in, -- Not sure
CSA = 174in^2, -- ??
Zp = 45in,
vent 6in diameter x 4in long, same damping. -- Got it
Thanks for your effort - sorry I don't totally understand the result.
Already covered above, but, internal dimensions
48in = vertical height
CSA = Cross Sectional Area of the Line.
Zd = distance of driver centre from throat (closed end of the line)
Zp = distance of vent centre from throat
Jeff, yeah, top is a max-flat alignment & it'll need adjusting via damping or vent tuning to suit the room & system etc. in practice. I generally tend to give this alignment for forums as it's the theroretical 'ideal', albeit on that understanding. It's easier than trying to second guess the room & system characteristics, taste etc.
48in = vertical height
CSA = Cross Sectional Area of the Line.
Zd = distance of driver centre from throat (closed end of the line)
Zp = distance of vent centre from throat
Jeff, yeah, top is a max-flat alignment & it'll need adjusting via damping or vent tuning to suit the room & system etc. in practice. I generally tend to give this alignment for forums as it's the theroretical 'ideal', albeit on that understanding. It's easier than trying to second guess the room & system characteristics, taste etc.
Thanks!
Thanks for the replies. What an amazing knowledge resource people are, eh? Beats just reading. Wait . . . .
That is a big box! I am "downsizing" from a setup with Altec 416As in 614 clone enclosures, 291A drivers in 311 horns, to the fullrange setup. The Altec system was unparalleled in dynamics, and wonderful when it sounded good, but very difficult to tame in my small room (16 x 17 x 7').
So I think I will try the smaller box and see where that takes me.
Here's another question about this system - those measurements are close to a clone of the Hammer box EXCEPT the Hammer uses that wacky styrofoam packing peanut/bubble wrap stuffing/lining method.
What's up with that? My understanding of MLTL theory (such as it is) was that the stuffing in the top half of the line serves to attenuate the standing waves associated with the line's resonant frequency. Do the peanuts serve the purpose equally well? Do they do the same thing at the bottom of the line (just under the port opening)? Or do they serve some other purpose?
I am not trying to make a clone of the Hammer Dynamics speaker - if I wanted to do that I should just buy the kit, right? I am just really curious about it.
Thanks for the replies. What an amazing knowledge resource people are, eh? Beats just reading. Wait . . . .
That is a big box! I am "downsizing" from a setup with Altec 416As in 614 clone enclosures, 291A drivers in 311 horns, to the fullrange setup. The Altec system was unparalleled in dynamics, and wonderful when it sounded good, but very difficult to tame in my small room (16 x 17 x 7').
So I think I will try the smaller box and see where that takes me.
Here's another question about this system - those measurements are close to a clone of the Hammer box EXCEPT the Hammer uses that wacky styrofoam packing peanut/bubble wrap stuffing/lining method.
What's up with that? My understanding of MLTL theory (such as it is) was that the stuffing in the top half of the line serves to attenuate the standing waves associated with the line's resonant frequency. Do the peanuts serve the purpose equally well? Do they do the same thing at the bottom of the line (just under the port opening)? Or do they serve some other purpose?
I am not trying to make a clone of the Hammer Dynamics speaker - if I wanted to do that I should just buy the kit, right?
I am just really curious about it.Correction circuits
My other question remains . . . since I am using a digital EQ do I need to fuss with correction circuits to tame the Beta's rising response curve? Or is it in place to damp resonances arising from standing waves in the TL? Or to tame resonances inherent to driver itself?
That is something I _really_ don't understand, and any links to a "correction circuits for dummies" resource would be very very much appreciated. I can understand the concepts involved but there is a reason I went into design and not engineering.
My other question remains . . . since I am using a digital EQ do I need to fuss with correction circuits to tame the Beta's rising response curve? Or is it in place to damp resonances arising from standing waves in the TL? Or to tame resonances inherent to driver itself?
That is something I _really_ don't understand, and any links to a "correction circuits for dummies" resource would be very very much appreciated. I can understand the concepts involved but there is a reason I went into design and not engineering.
Several years ago I built the "Afterburner" project using the LTA 12's. I did all the suggested mods from the TL article, and additionally had planet 10 make a pair of phase plugs. They live in a cabinet that is 20w, 14 deep, and 44 high, which leaves (after bracing, driver, etc) about 5 cf. They are tuned to 45hz. I used the suggested correction network, and suppliment hf with a fostex ht17, crossed with a 1uf cap only. They sound very good for the money. If you put them next to another speaker, they may sound a little nasal/recessed in the upper midrange, but they have excellent dynamics and bass, and efficiency that opens them up to about any amp you wish. I am driving them with a "darling" amp, which only makes about 750mw per channel, but they will fill my office (12 x 14) easily.
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I could live with that box. It's tall but shallow, which would work great in my room. Is that shallowness what's causing the big midbass bump? Any ideas about stuffing this box? Scott, would you use the same damping method you proposed in your first model, at least as a start?
I just want to say that this forum is really, really amazing. This thread, with the input of all you smart people, is now the best source I know of for box designs for the Beta LT/A. I've learned more in three days than I have in about three months of Googling aimlessly. Thanks!
I just want to say that this forum is really, really amazing. This thread, with the input of all you smart people, is now the best source I know of for box designs for the Beta LT/A. I've learned more in three days than I have in about three months of Googling aimlessly. Thanks!
Hey Scott, when I was learning this stuff there was no 'prosound', it was all 'PA' (public address or professional audio) outside of a theater's 'cinema sound', so didn't give it a thought.
thansaffel,
The sim is minimally stuffed its entire length with 0.2 lbs/ft^3 polyfil, so any more will begin raising its F3 as it flattens the mid-bass 'bloom' out which is caused by the box having a too small a net Vb for the driver's specs. Normally though, it's adjusted by changing Fb, so you can increase it with a larger vent or a longer one to lower it, i.e it's a common way to dial in acoustic BSC as well as a lower Q roll off for near wall or corner locations.
GM
thansaffel,
The sim is minimally stuffed its entire length with 0.2 lbs/ft^3 polyfil, so any more will begin raising its F3 as it flattens the mid-bass 'bloom' out which is caused by the box having a too small a net Vb for the driver's specs. Normally though, it's adjusted by changing Fb, so you can increase it with a larger vent or a longer one to lower it, i.e it's a common way to dial in acoustic BSC as well as a lower Q roll off for near wall or corner locations.
GM
>>> The sim is minimally stuffed its entire length with 0.2 lbs/ft^3 polyfil, so any more will begin raising its F3 as it flattens the mid-bass 'bloom' out which is caused by the box having a too small a net Vb for the driver's specs.
Wow! The beginnings of understanding why stuffing a box makes it appear larger to the driver.
Thanks,
Godzilla
Wow! The beginnings of understanding why stuffing a box makes it appear larger to the driver.
Thanks,
Godzilla
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