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What would be the ideal parameters for a high efficency open baffle 15" woofer? What are the tradeoffs as you go toward those ideal parameters? Finally, what aspects of the woofer's performance suffer the most as you go towards those parameters: damping, HF extension, efficiency?
Follow Ups:
Hi Folks,I've been following this thread with interest, for I'm pondering an OB setup myself.
I'm wondering about bass extension. Using Thorsten Loesch's Xlbaffle spreadsheet, and plugging in the Dayton 295-455 (15", Qts 0.65, Fs 20.8Hz) in a 40" baffle, I get +-1.5dB from 1000Hz to 30Hz, down 6dB at 20Hz, before equalization.
Comments? Is that believable? Am I overlooking something? That looks like fine bass response to me, but I've been wrong before.
As an aside, though "high efficiency open baffle bass" may be an oxmoron, it may still be a good match to a high efficiency OB mid-high setup. I'm pondering combining somthing like the Fostex FX120 open baffle with a 300B SET for say 200Hz up, and the Dayton open baffle with whatever sand boatanchor I can find for below 200Hz.
Thorsten's modelling is usually pretty accurate, as far as modeling goes as opposed to real life. The Dayton subs are designed for low frequencies and IB installations, ie highish Qts. The combination of near-floor positioning (effectively increasing baffle size and adding floor reflection) and various room effects (for example placement near rear walls where you're effectively going from half-space to quarter-space) can add quite a bit to the lower end. We don't mount open baffles twenty feet in the air in a cornfield. That's why people report decent results even with un-EQed highish-Qts woofers like Altec 515s, which "should" rolloff in the 100hz range but in practice go lower.There's another OB effect which might (I'm guessing wildly here) be significant. Of course there is a lot of rear-wave output from the midrange driver, which it somewhat omnidirectional in the 100hz-1000hz range. This may add an effective 2db or so of boost for these frequencies, which can be very welcome for fullrange drivers which tend to have a high-frequency lift.
Dr. DeVille,Where can one find Thorsten Loesch's spreadsheet?
Thanks,
Hi Joe,It seems to float around various places. I searched for Xlbaffle.xls in Google, and found it various places, like:
http://baseportal.de/cgi-bin/baseportal.pl?htx=/Data/exdreamaudio/download&cmd=list&range=0,20&cmd=all&Id=15
To my eyes it may actually present too much data, since it seems to calculate all the ripple effects from wall distances, driver height, etc.--pretty overwhelming for a novice like me. But it gives me an overall impression--whether my impression is accurate is another question. ;^)
Hope this helps,
Is that the IB Parts Express Speaker? If so, I'd say the 30hz on an OB is very achievable. I have a pair, each mounted on an 18" wide (+6" wings) baffle and measured in room to 30hz. I cross them at about 60hz (w/Line Level passive into a seperate amp) so they meet the falling response of the upper full range speakers, an EV SP-12B. Sounds great to me, and to others who have listed.
Yes, that's the one. It's good to hear you are happy with it. Like Russ, I'm curious--did you try crossing it over higher? (That may not be worthwhile with your EV s, dunno.)Thanks,
My mid range needs to be crossed over near 250. So my problem is finding a driver that will go down low on an open baffle but still run up that high cleanly.
Hi Russ,I have the same question, since I'd like to experiment, and crossover to the DAYTON IB385-8 somewhere between 200Hz and 500Hz. I'd like to crossover as high as possible (great sound being the first priority), to unburden the fullrange/SET that covers the higher frequencies.
Here's a link to the overview:
http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=295-455
and the spec sheet:
http://www.partsexpress.com/pdf/295-455.pdf
To my eyes, it looks like the response is smooth to about 700Hz, where it takes a dive. Whether it sounds good up there is another question. The response looks reasonable.
Would beaming be a problem? I know nothing but the broadest theory--that a speaker beams as the wavelength approaches its diameter. 500Hz has a wavelength of about 2', so that's getting close to the 15" diameter. So how severe would that be?
Has anyone used this speaker?
Best,
The dip at 750hz looks nasty,but its probably inaudible,the room will do that sort of thing too.Most people XO their high mass sub only woofers nearer 100hz so this is abit more difficult.Perhaps more prosound style woofer,with EQ will work.
Have you looked at Hawthorne Augies?I think they go ~500hz.Beaming wont be a problem,It isnt going to be beaming at something like 45* angle.
A slight amount of beaming eg 90* at 1.5 khz will help reduce room interference anyway.
Mike.e
There are three constants in life: death, taxes, and the inevitability of a (speaker)wire thread being closed -SY
Hey Mike,Thanks for the helpful thoughts! Good to hear that beaming might not be an issue.
"Most people XO their high mass sub only woofers nearer 100hz so this is abit more difficult.Perhaps more prosound style woofer,with EQ will work."
Is there a particular reason why a woofer like the Dayton or the Hawthorne wouldn't sound good above 100Hz, even if the frequency response looks good? (I'm hoping the typical 100Hz crossover has more to do with the higher frequency drivers typically used in boxed speakers, rather than an inherent limitation of the Dayton)
Yes, I am considering the Hawthorne Augie, though its website presents limited specs, and no frequency response graph. Plugging it into Thorsten Loesch's spreadsheet (and guessing at the missing parameters) gives higher efficiency than the Dayton, but much more rolloff below 40Hz.
Since I'm going to use a random solid state amp for bass, I don't particularly care about woofer efficiency, but I do care about low frequency extension.
That, combined with the fact that the Dayton shows a response graph, is cheaper ($110/ea for four), and has a Q of 0.69 versus 0.92 for the Augie, has me leaning towards the Dayton.
I'm thinking dual Daytons per side--sort of a knock-off of quarter-wave.com's Project 7:
http://www.quarter-wave.com/Project07/Project07.html
He crossed-over at 100Hz, but I'd like to experiment with higher frequencies, with 100Hz as a fallback.
All comments, insights, and suggestions appreciated.
Thanks!
Is there a particular reason why a woofer like the Dayton or the Hawthorne wouldn't sound good above 100Hz, even if the frequency response looks good? (I'm hoping the typical 100Hz crossover has more to do with the higher frequency drivers typically used in boxed speakers, rather than an inherent limitation of the Dayton)The problem is in the measurements themselves. Conditions such as boundarys,indoors or out,smoothing applied etc.
You probably already know about people measuring nice responses and not hearing a nice musical result.Interpreting graphs brings in psychoacoustics,low Q vs high Q resonances for example.
The alpha15 looks good according to that site.Xmax is a little low,but 4 total should be enough for sane volumes.
Can you post more detail about what the entire system eg why 250hz XO.
Regards
Mike.e
There are three constants in life: death, taxes, and the inevitability of a (speaker)wire thread being closed -SY
Mike Wrote:"Can you post more detail about what the entire system eg why 250hz XO."
Thanks Mike--Oh boy can I (grin).
The starting point is I'm building a 300B SET (my first SET experience), and want to hear that fabled SET goodness hooked to a driver with no passive elements.
I decided to start with a Fostex fullrange, as a good bang-for-the-buck starting place.
Reading up, I found a lot of issues in coaching simultaneous bass, volume and clarity from a FR Fostex, so I decided to bi-amp to take the burden off the Fostex.
I was originally going to go with something like Bottlehead/Paul Joppa's S.E.X.y speaker--FR Fostex in small sealed box, dual inexpensive bass reflex subwoofers. But my love for dipole systems (Magnepan, Dahlquist DQ10) pushed me towards open baffle, and my desire for well integrated bass led me towards open baffle bass.
Which leaves me at my current bogey: digital crossover/equalizer sending highs to a 300B SET wired straight to an open baffle Fostex fullrange, and lows to a random sand amp wired straight to open baffle woofers, probably two per channel.
Bottom line is, the 250Hz crossover point is far from set in stone, but I would like drivers, particularly bass ones, that would allow me to experiment with XO points between 100Hz and 500Hz.
If a relatively low crossover point, say in the 250 to 350Hz range, sounds good, it will unburden the SET/Fostex combo, allowing higher volumes. Vocals are my main priority, so if moving the transition up towards 300Hz hurts the vocals, I'd set it lower.
My current choices are the Fostex FX120 and the Dayton 15" OB Woofer.
My thinking is the high end of the FX120 looks flat and extended, it has no whizzer to resonate, and biamping will effectively raise its sensitivity 6dB to 95dB, which I'm hoping will be fine with the 8W 300B SET.
The Dayton IB Woofer (part number 295-455, 15", Qts 0.65, Fs 20.8Hz) has smooth response up to 700Hz and very extended bass. Using Thorsten Loesch's Xlbaffle spreadsheet and plugging in a 40" baffle, I get +-1.5dB down to 30Hz, -6dB at 20Hz, before equalization.
So I hoping those two would be good fodder for experimentation--I could mess around with the digital crossover until I get slopes, frequencies and equalizations that I like. Then I could hardwire a line-level crossover with analog components if I wanted.
Of course that's all theoretical, and I've don't have the components to audition, so I'm just winging it as best I can.
So there are the specifics and my rational/preferences. All comments, insights, suggestions greatly appreciated. Thanks for the help you've already given me.
Best,
George
The above is the 3rd version of the bass portion of my OB, LA, DIY speakers.The 1st used 4 of the 6-1/2" drivers while the 2nd used one of the Sonic Craft SCC300 bass drivers.
All of these were/are driven by a channel of an Outlaw 770 (200-Watts-into-8-times-7) poweramp driven by a Dahlquist DQLP-1 active-low-pass filter. Its bottom-octave-boost control was always flat with all 3 of these systems. (Raising that boost simply made the room nodes MUCH more audible.) I was advised that the quartet of 6-1/2-ers wouldn't reproduce good bottom-octave bass, but I had to try it myself. Jeff Glowacki of Sonic Craft was correct--the bottom 2 octaves of bass sounded OK but not great. Version 2 sounded MUCH more authoritative in the bottom octave than the quartet, but the sensitivity was low enough that I had to run the LP-1s level controls full up to try to match the output of the 97dB-sensitive main system. That sensitivity problem was solved by adding the 2nd bass driver in parallel, and the bass system's output increased exactly the 6dB it theoretically should have.
I was VERY pleased with the sound of this system including the bass--it was tuneful, extended, dynamic, tight, etc..
You may have noticed my use of the past tense. I still have this LA system, but it's now driven thru a dbx DriveRack PA digital Speaker-Management System, is triamped, and has NO passive parts in the speaker system. It now sounds even better, even with the tweeters driven temporarily by a 20-year-old Hafler 60WPC sand amp.
The wings are 30" (outside) and 25" (inside) deep at their bottoms, and when I build the next version of this dipole system, the wings will be shallower, maybe 24 and 20 inches deep. The front plate will have fairly narrow...maybe 8"...curving-back wings on it, and I'll use more of the the SMS's equalization capability to recover ('overpower'?) the lower-midrange and bass energy lost to wrap-around cancellation.
Open-baffle bass? I love it.
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Tin-eared audiofool and obsessed landscape fotografer.
http://community.webshots.com/user/jeffreybehr
Hey, Jeffrey,Interesting! Snkby says his 2 8" drivers are superior to his pair of 15" drivers. In your case the two 12s are superior to the 4 6.5" drivers. Even though ts parameters may not tell us the whole story, the fact that these woofers have a qts of .442 and the fact that their rated 90db efficiency is increased to 96 (I suspect that the actual efficiency is more like 88.5 and it is increased to 94.5) when run in parallel would seem to make these possible candidates to consider when trying to mate to a more efficient upper end. Where have you crossed over the woofers on top? And do you find there are any issues with them mounted right at the floor?
Thanks,
The bass LP filter points have been variously at 60 - 80Hz. Of course a lot depends on the slope; the LP-1's is 3rd order, and its last settings were both 65Hz. I just looked at the dbx DRPA; it's set on 60Hz and 4th-order Butterworth slope. (The B/MR drivers are run almost full range on the bottom.)I have no issues with the bass system, but I'm not an experienced and/or skillful speaker builder, I'm just a long-time audio hobbyist who got brave and lucky with this project. I do have a Hall SPL meter and noise generator and a Phonics AA2 RTA, and they help a bunch.
PS. There's a difference, albeit subtle, between 'sensitivity' and 'efficiency'. While we all understand the terms, generally, to address the speaker's ability to convert electrical energy into acoustical energy, when staing things like "...rated 90db efficiency is increased to 96 (I suspect that the actual efficiency is more like 88.5...', what you're actually discussing is sensitivity. Formally, efficiency is measured with 1 Watt of power (which is whatever Voltage is required into a resistor equal to the rated impedance or the speaker), while sensitivity is measured with 2.83Volts-RMS measured into an 8-Ohm resistor and using a solid-state amp. Of course, a speaker lower than 8 Ohms impedance will draw more power than 1 Watt. So...efficiency is measured with 1 Watt, and sensitivity is measured with 2.83V/8-Ohms. If this is incorrect, I hope someone will correct my understanding.
-------------------------------------------------------
Tin-eared audiofool and obsessed landscape fotografer.
http://community.webshots.com/user/jeffreybehr
as the ideal parameters go............its been my experience that what the driver sounds like and how it performs isnt really anything you will be able to derive from ts parameters.too many variables involved to discount any driver that is anywhere near the ballpark for the application.
for instance.........i just put a pair of 16ohm b&w 8"mid-bass drivers from the dm220 series on an ob and the sound is really really good with greater depth and presence than when the drivers were sealed in their box.
im sure many people would never have tried this because drivers designed for small sealed enclosures shouldnt be that good on ob but these sound really good.
i hate to say it but they seem to be putting out more bass than the pair of 15"drivers that are in the main speakers and those drivers are supposed to be great for ob.
come on over and hear what is going on. :)
i will shoot you an email for the address.
I need a pair. Damn cat destroyed them and I hate to toss the speakers. I think the ones from that speaker are the same.
both of them and the xovers if you like.i need to ship a bunch of stuff this week so shoot me an email with your address if you want them.
I'll pull mine out and take a look. I might only need one tweeter.But yes, if you have the same tweeter I could sure use it. I can't do asylum mail can you email me at Rbrunt(at)mercymiami(dot)org?
Here is a link to a pic of mine. Does your tweeter look the same?
http://www.bwspeakers.com/downloadFile/speakerModel/DONE_-product_info_DM330i.pdf
x
David,It would be nice to visit again, and, of course, I am very interested to hear your ob. I have heard from others as well that ts parameters do not necessarily tell you what is going on in this type of situation.
Interestingly, Dick Olsher says, "It seems to me that many listeners confuse bass weight with bass extension and opt for a subwoofer when bass weight is lacking. The problem typically lies in the upper bass, the octave from 120Hz to 240Hz where much of an orchestra's foundation and acoustic power resides. This is the octave that box woofers have a hard time coping with, basically managing to sound boxy through this range." I suspect that your 8" drivers are adding considerable weight. Have you measured their bottom end extension?
Many thanks,
real rta loaded on a laptop and hope to get some meaurements later this week after i build a real psu for the active xover.i go past the blackpoint exit a few times a week.
let me know when you want to get together either at my place (have to wait for family to be gone) or at your place.
In my experience:1) Biamping OB bass tends to work pretty well, so you can hook up a big earthmover amp (100W) and you don't have to worry about the efficiency too much. In general, OB is not a good way to go if you want high output in the bass, which is why you'll never see it with prosound gear.
2) You tend to get more help on the lower end than the equations say because the woofer is usually mounted near the floor. Also, there can be some room lift.
3) I haven't done too many experiments with it, but I'd say that super-high Qts drivers (higher than 0.8) may not be the way to go. High Qts usually means a small magnet, which means poor cone control, which means a resonance peak at F0 which is exactly the effect desired by the OB user. However, this resonance peak tends to sound like a resonance peak -- sort of like the port frequency on a bass-reflex enclosure. Is that what you want? That's fine up to a certain point but maybe you'll want more at some point. Thus, I'd consider lower-Qts (under 0.6) drivers with low (under 30hz) F0, and use active EQ.
4) With a big baffle you have less rolloff than a smaller baffle, which means less EQ, less excursion, and less power used.
5) I think multiple medium-excursion drivers are better than a single high-excursion one.
6) You might be able to live with 50hz but 35hz is better.
7) I bought a Behringer electronic crossover and two parametric equalizers on eBay for about $200 plus shipping. The fancy digital stuff is more.
8) After all that, if you have output/excursion/power limitations, ditch your OB and go get a sealed subwoofer. With my woofs EQ-ed up 12db at 35hz, I rarely use more than about 5 watts on peaks. Sometimes I crank it up to 50W peaks just to watch the cones move, but you wouldn't want to listen at those levels, in my room. I haven't clipped the 100W SS bass amp yet. Like fullrangers, OB bass is best when you are nowhere near their technical limitations. If that's not your gig then go get some basshorns.
9) I have used a 96db low-Qts (big honkin' alnico magnet) 15" woofer in a 4' OB without EQ and it sounded good, in a small room. I wouldn't recommend it, but I did it and lived with it for over year.
Thanks!
"High Qts usually means a small magnet, which means poor cone control, which means a resonance peak at F0 which is exactly the effect desired by the OB user. However, this resonance peak tends to sound like a resonance peak -- sort of like the port frequency on a bass-reflex enclosure."Yep.
But aren't BR's pretty popular for a good reason ?
Bang/Buck .....????
"But aren't BR's pretty popular for a good reason ?"Yeah, largely because that's the kind of use the best woofers are suited to; the characteristics that make them good woofers (not subwoofers mind you) also dictate they be used in vented boxes.
Check out what Lukasz Fikus is doing in Poland. He thinks 15-inch Altec woofers give the best results in either large OB or infinite baffle. One question you need to ask yourself is how low is deep enough. It makes a big difference if you're happy with "ample bass" at 30Hz or if you need to be real flat to below that.In addition to the clickable link shown, you might want to check out this too:
http://www.lampizator.eu/NIRVANA/nirvana.html
In fact, his whole website is very interesting and worth checking out.
There is a huge amount of useful information at Linkwitz's open baffle pages.
Here is a more useful link for Linkwitz -- that last one was just one DIYer's implementation of it.
MOMBig baffle + High Q * multiple drivers?
Can you post a link or run through the specifics
Dick Olsher discusses the trade offs here:
- http://www.enjoythemusic.com/magazine/equipment/0107/diy_loudspeaker_project.htm (Open in New Window)
Assuming no EQ (active or passive):Qts needs to be relatively high (depending on relationship of Fs to baffle cutoff frequency)
Fs needs to be high enough so that the baffle can reinforce the resonant frequency to some extent
I couldn't think of a reason other than you only wanted to use the driver as a upper bass/lower midrange driver.
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Richard BassNut Greene
Subjective Audiophile 2007
....
This also assumes a 'practicle' F3
Talking a woofer not a 'sub'
For F3 ~ Fs
needed baffle diameter ~ 360 feet / (Qts * Fs)
For instance:
with a 4' baffle and a driver with Qts~2 and Fs~50Hz
you're flat down to 50Hz sans EQ
Now I'm even more confused.Who wants to have a 16 square foot baffle x 2 ... and still need one or two more speakers for the bass under 50Hz.?
Who wants to use a 2.0 Qts. driver?
And would a 2.0 Qts driver on a 16 square foot open baffle really provide a flat frequency response down to 50Hz. without EQ?
If the answer is yes based on measurements of a real speaker, not theories, then I apologize for questioning the use of a 15" driver in a dipole configuration with no EQ.But then you'd still need to add a monopole speaker to fill in the bass under 50Hz. -- and that would make no sense because the greatest advantage of dipole speakers in most rooms is less excitation of bass standing waves (causing a more realistic reproduction of bass instruments). Why use a monopole speaker to reproduce those low frequencies when a dipole speaker would have the greatest inherent sound quality (including room effects) advantage over monopole speakers?
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RBNG - Who wants to have a 16 square foot baffle x 2?Someone who wants their baffle to contribute to the sound as much as the driver?
RBNG - Who wants to use a 2.0 Qts. driver?
Someone who appreciates high levels of driver distortion "enhancing" their "bass"? What if: "Yeah, but it sounds good"?
RBNG - But then you'd still need to add a monopole speaker to fill in the bass under 50Hz. -- and that would make no sense because the greatest advantage of dipole speakers in most rooms is less excitation of bass standing waves (causing a more realistic reproduction of bass instruments). Why use a monopole speaker to reproduce those low frequencies when a dipole speaker would have the greatest inherent sound quality (including room effects) advantage over monopole speakers?
Well here I must disagree with you. A monopole (placed beside/under) crossed at 50hz to a dipole will create a cardioid radiation pattern in the XO region. It will only radiate omni directionally at even lower frequencies where room modes are sparse and room gain from a pressure source is beneficial. Not a bad idea except there will be added GD from the XO, but I'll take a little phase distortion over grotesque IM from an over excursion driver.
cheers,
AJ
The threshold for disproving something is higher than the threshold for saying it, which is a recipe for the accumulation of bullshit - Softky
That's why they are so audible -- not dense enough!Probably three room modes under 50Hz. in a typical room.
Maybe four in a very large room.
These lowest frequency bass resonances are also the most powerful.
You control harmonic distortion by using mutiple high-XMAX drivers for a dipole. Not cheap. Not small. But subjectivelky better bass quality than monopole speakers in most rooms. Especially smaller rooms.
There is no room gain from a pressure source unless the room is unusually sell sealed (like a car with windows closed) which is very rare. You may ask Earl Geddes for details from his experiments.
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Richard BassNut Greene
Subjective Audiophile 2007
RBNG - That's why they are so audible -- not dense enough!
Probably three room modes under 50Hz. in a typical room.Once again, when you combine a dipole with a monopole xo'd @ 50hz, you have cardioid radiation @ 50hz. So yes, a monopole will have very few modes to excite in the below 40hz range. A cardioid will excite different modes than the dipole or monopole, but will maintain DI and still radiate -4.8db less power. An equalized monopole below 35hz is superior in every way a dipoles hopeless ineffeciency below these frequencies. I have linked a 2 part article for you below. Give it a read.
RBNG - You control harmonic distortion by using mutiple high-XMAX drivers for a dipole. Not cheap. Not small. But subjectivelky better bass quality than monopole speakers in most rooms. Especially smaller rooms.
Yes, I've known that for many years first hand. I practice what I preach :-).
RBNG - There is no room gain from a pressure source unless the room is unusually sell sealed (like a car with windows closed) which is very rare. You may ask Earl Geddes for details from his experiments.
.I was there when Earl caused a near riot over on the Mad board (when it was functional) with his own use of the term. Won't rehash that again.
cheers,
AJ
I contend that we are both atheists; I just believe in one fewer god than you. When you understand why you reject all other gods, you will understand why I reject yours
I wouldn't want you to get too excited by saying "You're right!"In a typical 20' x 15' x 8' listening room
Stereo bass speakers summary:
Most benefits from dipoles are likely to be above 50Hz.
But if there is a first-order width standing wave with a particular song (bass must be louder in one channel than in the other), then stereo dipoles are a better choice than stereo monopolesMono bass speaker summary:
If there is just one mono bass driver (let's say up to 80Hz.),
then dipole is the best choice
Supporting "armchair analysis" comparing three bass driver choices:
(1) using one mono monopole driver on left side of room, or on right side of room
(2) dual left-right monopole drivers,
(3) dual left-right dipole driversAxial room modes analysis
28.25Hz. first-order length
(1), (2) & (3) = all strongly excite this room mode37.7Hz. first-order width
(1) = strongly excited (a single dipole would be better)
(reduced excitation if woofer is placed halfway between the side walls in the partial null)
(2) & (3) no standing wave forms at all if bass output from both speakers is identical, because the speakers are located out of polarity for this standing wave. But if bass IS louder from one side, there will be at least a weak standing wave, and dipole speakers will excite the standing wave 4.8dB less than monopole56.5Hz. second-order length
(1), (2) or (3) = all strongly excite this room mode
71Hz. first-order height
(1)= strongly excited (a single dipole would be better)
(2)= strongly excited
(3)= 4.8dB less excitation from dipole woofer75.3Hz. second-order width
(1) strongly excited (a single dipole would be better)
(2) strongly excited
(3) 4.8dB less excitation
(but even less excitation can be achieved from either monopole or dipole if woofers can be located at 1/4 and 3/4 of the room's width, in the partial nulls for this room mode)
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Richard BassNut Greene
Subjective Audiophile 2007
> Someone who wants their baffle to contribute
> to the sound as much as the driver?For 'high efficiecy' one would probably want the
whole 'baffle' full of drivers> RBNG - Who wants to use a 2.0 Qts. driver?
What does "RBNG" mean?
> Someone who appreciates high levels of driver
> distortion "enhancing" their "bass"? What if:
> "Yeah, but it sounds good"?You think you would have much distortion with
(from the standpoint of a 4' x 4' baffle)
(only considering the low end)
say 16 8" drivers with a Q ~ 2
(at a moderate level) ???????
HW - For 'high efficiency' one would probably want the
whole 'baffle' full of driversWell, that would certainly be one way to do it. But your picture showed one driver on a very large baffle. That is what generated my comment.
What does "RBNG" mean?
My post was a response to R ichard B ass N ut G reen. Kinda like this response is to H its W are :-).
HW - You think you would have much distortion with
(from the standpoint of a 4' x 4' baffle)
(only considering the low end)
say 16 8" drivers with a Q ~ 2
(at a moderate level) ???????Carefully read what I said. "Someone who appreciates high levels of *driver* distortion."
I said a 2.0 Qts *driver* would have high distortion. Not 20 of them combined LOL. That would certainly help lower distortion! If you were going to take the multi driver approach, use several HE drivers in a vertical array on your sidewalls.cheers,
AJ
I contend that we are both atheists; I just believe in one fewer god than you. When you understand why you reject all other gods, you will understand why I reject yours
Richard---OBs are easier than boxes, often uses one for convenience and calls it's resulting vices virtues. However on a couple of occasions I've heard them sounding pretty decent, especially an EV Wolverine 12 I heard and a Madison 21. God knows what the things were doing but they sounded full and robust.Note that a fella who was once the foremost advocate of OBs around here used lots of EQ to get deep bass from a large OB array, which as you know means it was no longer high efficiency. He was also keen on using a low efficiency box subwoofer with OBs.
Recently I bought a couple of those old Yamaha "ear" speakers which used open backed boxes. They sounded OK. I'm gonna nail the drivers up on the wall in the garage as curiosities.
> Who wants to have a 16 square foot baffle x 2Yes. Pretty big. Options are foldback 'wings' or both
channels on 1 baffle.> Who wants to use a 2.0 Qts. driver?
Me. Any higher and ripple starts to manifest,
but for OB a Q of ~2 is optimum for bass/size> And would a 2.0 Qts driver on a 16 square foot
> open baffle really provide a flat frequency
> response down to 50Hz. without EQ?Yes. I've measured and listened.
Freddyi did a SPL graph of the same
system (big baffle in the pic)
that agrees.> But then you'd still need to add a monopole
> speaker to fill in the bass under 50Hz.
> -- and that would make no sense because the
> greatest advantage of dipole speakers in most
> rooms is less excitation of bass standing waves
> (causing a more realistic reproduction of bass instruments).
> Why use a monopole speaker to reproduce those low
> frequencies when a dipole speaker would have the
> greatest inherent sound quality (including room effects)
> advantage over monopole speakers?I can live with 50Hz myself. Even down to 100Hz OB with
a sealed 'helper woofer' is better than the box colorations
inherent with monopoles. (IMO).........:)
Open baffle means a 6dB/octave bass roll-off which is another way of saying low efficiency.Because of the front/back cancellations dipoles need a lot of displacement for deep bass output, so high XMAX drivers, which are rarely efficient, are the obvious design choice.
Some dipole builders may want drivers with a Qts of 0.70 (rare) which can be equalized passively with a single coil ... but you could use a lower Qts driver, such as the Sigfried Linkwitz designs using low Qts drivers + electronic circuits available at his website.
Using the words "efficient and speaker" in the same sentence could be thought of as an oxymoron, although "high efficiency open baffle" is the ultimate audio oxymoron.
All bass speakers are inefficient tools creating far more heat energy than sound energy!
With an open baffle bass drivers are ultra-low efficiency!
Because of the open baffle, low noise driver motors are mandatory.Anyone can use four large diameter low-XMAX high efficiency drivers to build a dipole subwoofer ... but two high-XMAX drivers will be roughly half the cost of four drivers, and require half the baffle surface area.
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Richard BassNut Greene
Subjective Audiophile 2007
Where have you been?
Extraordinary claims require much doubt!
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Richard BassNut Greene
Subjective Audiophile 2007
nt
vs a 12" in a k12 type box tuned ~58Hz - box had LC network to pull more current than normal (low Z-input) but 100Hz might be fair area to compare sensitivies. IIRC Qts on this 21 ~1.3 and fs ~30
"the words "efficient and speaker" in the same sentence could be thought of as an oxymoron,"Well you know what me mean, indulge us.
"With an open baffle bass drivers are ultra-low efficiency!"
"Anyone can use four large diameter low-XMAX high efficiency drivers to build a dipole subwoofer"
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