Non-directional? Not until you get to about 60 hz.
This is where the big debate comes in. The home-theatre guys at Radio Shack want you to believe that everything below 200hz is nondirectional, so they can sell you a setup with 2" fullrange satellites and an 8" woofer for $300. Yuck!
Try it. Even in a small room, play a note at 100hz and pan it--it's directional. In my small room it stays directional until about 60hz, and as the room gets bigger, the directional frequency gets lower.
The reason the HT guys can get away with this is because, most of the time, basses aren't panned hard to one speaker so it doesn't make a *huge* difference most of the time. I've listened to setups like the one I describe, and if you're in the sweet spot, and you're not listening to demanding materials, it won't bother you to have nondirectional bass. I, of course, am picker than that
D) but hey, if a modded Basszilla works for you, do it.
This is where the big debate comes in. The home-theatre guys at Radio Shack want you to believe that everything below 200hz is nondirectional, so they can sell you a setup with 2" fullrange satellites and an 8" woofer for $300. Yuck!
Try it. Even in a small room, play a note at 100hz and pan it--it's directional. In my small room it stays directional until about 60hz, and as the room gets bigger, the directional frequency gets lower.
The reason the HT guys can get away with this is because, most of the time, basses aren't panned hard to one speaker so it doesn't make a *huge* difference most of the time. I've listened to setups like the one I describe, and if you're in the sweet spot, and you're not listening to demanding materials, it won't bother you to have nondirectional bass. I, of course, am picker than that
D) but hey, if a modded Basszilla works for you, do it.
Nappylady said:Non-directional? Not until you get to about 60 hz. In my small room it stays directional until about 60hz, and as the room gets bigger, the directional frequency gets lower...I, of course, am picker than that
I found I could localise bass even at 80Hz with teh music playing. wihtout the rest of teh music playing (only sub on) I could localise bass till much lower. I used a sterophile test CD and I cant remember how low it was but it was defnitely below 63Hz. the room was about 320 sq. ft. with a 9 ft ceiling. after this test i decided on only stereo bass.
Push-push bass boxes... how directional are they?
I get the point, and I too would like to go for stereo bass, unless I'm severely cash-constrained.
But what I was asking about was different (or was it?) I was asking whether a pair of push-push drivers placed carefully such that their dividing line is aligned with the listener will sound less accurate or "worse" in any other way, than a direct-radiating "normal" bass box with its driver directly facing the listener. Question applies to 200Hz or lower. In the former case, I'm 90-deg off-axis from both drivers. In the latter case, I'm on axis.
What do you feel? Or am I right in understanding that if bass is directional till 60Hz or whatever, then push-push bass drivers placed as I described will always lack in detail and immediacy?
Tarun
PS: Sorry if I'm slow on the uptake... I am, actually.
navin said:
I get the point, and I too would like to go for stereo bass, unless I'm severely cash-constrained.
But what I was asking about was different (or was it?) I was asking whether a pair of push-push drivers placed carefully such that their dividing line is aligned with the listener will sound less accurate or "worse" in any other way, than a direct-radiating "normal" bass box with its driver directly facing the listener. Question applies to 200Hz or lower. In the former case, I'm 90-deg off-axis from both drivers. In the latter case, I'm on axis.
What do you feel? Or am I right in understanding that if bass is directional till 60Hz or whatever, then push-push bass drivers placed as I described will always lack in detail and immediacy?
Tarun
PS: Sorry if I'm slow on the uptake... I am, actually.
Hi Tarun,
I think you are helping a lot of us organize our thoughts about open baffle,etc.
-Yes I think the open baffle for just the upper bass and above is a very practical way to get the benefits if OB with the great bass of other approaches,
- push push works fine with any bass driver. my point was that the Basszilla and other similar designs are usually trying to lower IM distortion. The efficient, low x-max drivers such as full range drivers and pro drivers combine to produce a speaker with low TM Distorton. And they both have a similar "fast" sound so blend well when crossed over. One problem people have with combining electrostats with cone bass drivers is that their sound characteristics are so different. This is a similar situation. If Lynn Olsen says that the Scan Speak drivers have low distortion, then they will be fine. I suspect that their efficiency is lower than the pro drivers, but with the Jordans, might be a great matchup. The Scanspeaks are probably expensive though!
- I also find bass to be directional lower than 200 hz. I have a theory that it is at least partially due to higher resonances of the actual bass notes. I suspect a very high quality sub that doesn't have a lot of higher frequency resonances of the note that they are trying to reproduce are a lot less directional. If this is correct, it doesn't matter if you are filtering out everything above say 80 hz. - the speakers are producing higher notes on their own!
So crummmy cheap subs are easier to localize.
The bipole (push push) approach could certainly work. but I think it is better to have one of the drivers facing the listener. Although it makes some sense that having the drivers perpindicular to the listener would balance out, I suspect that you would get some wierd nulls and peaks, because from the side, drivers have a much less flat response.
Linkwitz uses an open baffle dipole in his speakers. Claims that the OB bass is the best part of the OB approach- it is affected by the room less. His bass box is smaller than mine. of course to do it his way you need a carefully designed bass equalizing circuit.
Or the high Qts drivers might work from what I am reading here.
I think the high Qts gives you a less rolled off bass, so even at low volumes ,the low Qts driver is going to need equalization.
One advantage of the bipole is that it compensates for the baffle step. Well with the approach I used, we try to adjust the bass box width to get the baffle step right at the crossover also. That way you can compensate for the baffle step loss by having a more efficient bass driver than your full range mid driver, or use an L pad to reduce the mid output. No tricky addition baffle step circuitry required, so the bipole advantage is lessoned somewhat.
The bipole with smaller drivers would would allow you to have a narrower cabinet with a mid baffle about the same width on top. It would look more like a tower, with a smaller footprint. A big Spouse Acceptance Factor plus.
-To biamp my system, I will first just use the passive setup I now have. Crossovers are really 2 filters on (usually) one circuit board.
One cuts off the high notes from the woofer. One cuts the low notes off the mid driver.
So I have a passive filter cutting off all the high notes right before the woofer, but I run the midrange without a crossover- the driver naturally rolls off the bass- also the baffle width kills off lower bass. So at first I will run the full signal to both amps. the output from one I will run to the full range/mid driver (with the tweeter hooked to this too but with a cap inline to cut off low frequencies to the tweet)
The second amp output will pass through the crossover filter to lose the high frequencies, then go to the bass driver. Because the crossover is so simple I think it will work fine. Also the steel core induvtor probably doesn't saturate because the bass driver is so efficient, that there really isn't ever that much power passing through. Later, I will try the Pass active filter when it is done.
I think using the Jordan in an OB setup is REALLY interesting and I encourage you to try it. Probably no tweter needed. People use them full range all the time without consequences, so at normal volumes I don't see any problems. I needed efficient speakers, so that would be the only unappealing thing about the Jordans for me.
I think you are helping a lot of us organize our thoughts about open baffle,etc.
-Yes I think the open baffle for just the upper bass and above is a very practical way to get the benefits if OB with the great bass of other approaches,
- push push works fine with any bass driver. my point was that the Basszilla and other similar designs are usually trying to lower IM distortion. The efficient, low x-max drivers such as full range drivers and pro drivers combine to produce a speaker with low TM Distorton. And they both have a similar "fast" sound so blend well when crossed over. One problem people have with combining electrostats with cone bass drivers is that their sound characteristics are so different. This is a similar situation. If Lynn Olsen says that the Scan Speak drivers have low distortion, then they will be fine. I suspect that their efficiency is lower than the pro drivers, but with the Jordans, might be a great matchup. The Scanspeaks are probably expensive though!
- I also find bass to be directional lower than 200 hz. I have a theory that it is at least partially due to higher resonances of the actual bass notes. I suspect a very high quality sub that doesn't have a lot of higher frequency resonances of the note that they are trying to reproduce are a lot less directional. If this is correct, it doesn't matter if you are filtering out everything above say 80 hz. - the speakers are producing higher notes on their own!
So crummmy cheap subs are easier to localize.
The bipole (push push) approach could certainly work. but I think it is better to have one of the drivers facing the listener. Although it makes some sense that having the drivers perpindicular to the listener would balance out, I suspect that you would get some wierd nulls and peaks, because from the side, drivers have a much less flat response.
Linkwitz uses an open baffle dipole in his speakers. Claims that the OB bass is the best part of the OB approach- it is affected by the room less. His bass box is smaller than mine. of course to do it his way you need a carefully designed bass equalizing circuit.
Or the high Qts drivers might work from what I am reading here.
I think the high Qts gives you a less rolled off bass, so even at low volumes ,the low Qts driver is going to need equalization.
One advantage of the bipole is that it compensates for the baffle step. Well with the approach I used, we try to adjust the bass box width to get the baffle step right at the crossover also. That way you can compensate for the baffle step loss by having a more efficient bass driver than your full range mid driver, or use an L pad to reduce the mid output. No tricky addition baffle step circuitry required, so the bipole advantage is lessoned somewhat.
The bipole with smaller drivers would would allow you to have a narrower cabinet with a mid baffle about the same width on top. It would look more like a tower, with a smaller footprint. A big Spouse Acceptance Factor plus.
-To biamp my system, I will first just use the passive setup I now have. Crossovers are really 2 filters on (usually) one circuit board.
One cuts off the high notes from the woofer. One cuts the low notes off the mid driver.
So I have a passive filter cutting off all the high notes right before the woofer, but I run the midrange without a crossover- the driver naturally rolls off the bass- also the baffle width kills off lower bass. So at first I will run the full signal to both amps. the output from one I will run to the full range/mid driver (with the tweeter hooked to this too but with a cap inline to cut off low frequencies to the tweet)
The second amp output will pass through the crossover filter to lose the high frequencies, then go to the bass driver. Because the crossover is so simple I think it will work fine. Also the steel core induvtor probably doesn't saturate because the bass driver is so efficient, that there really isn't ever that much power passing through. Later, I will try the Pass active filter when it is done.
I think using the Jordan in an OB setup is REALLY interesting and I encourage you to try it. Probably no tweter needed. People use them full range all the time without consequences, so at normal volumes I don't see any problems. I needed efficient speakers, so that would be the only unappealing thing about the Jordans for me.
Re: Push-push bass boxes... how directional are they?
1. given that you have 2 woofers you have 2 options i would consider build 2 single driver direct radiating TLs (given teh driver T/S specs co-operate).
2. push - push is great for many applications but most of tehse are when you have extra drivers and a bigger budget :-(
2a) push push is very good for 2.5 ways it kills 2 birds BSC and the 90 deg phase shift whena large inductor is introduced. dave is the expert on this.
2b) dipole bass from what i have read sacrfices quantity over quality. if you have 2 small drivers (8"?) i would not suggest dipole (is that what you are siggesting with push push) as it would reduce bass.
lastly building 2 TLs is good when
a) you need speaker stands anyway; the TLs can be used as stands
b) your stereo pair is more likely to be near corners of a room (one on each side as stands for the main speakers). If you are using small drivers (think 8" or less) and your F3 is above 40-45Hz then the boost from the corner or near corner placement might help.
hope this helps.
BTW you aint slow. trust me. it takes me longer.
tcpip said:But what I was asking about was different (or was it?) I was asking whether a pair of push-push drivers placed carefully such that their dividing line is aligned with the listener will sound less accurate or "worse" in any other way, than a direct-radiating "normal" bass box with its driver directly facing the listener. PS: Sorry if I'm slow on the uptake... I am, actually.
1. given that you have 2 woofers you have 2 options i would consider build 2 single driver direct radiating TLs (given teh driver T/S specs co-operate).
2. push - push is great for many applications but most of tehse are when you have extra drivers and a bigger budget :-(
2a) push push is very good for 2.5 ways it kills 2 birds BSC and the 90 deg phase shift whena large inductor is introduced. dave is the expert on this.
2b) dipole bass from what i have read sacrfices quantity over quality. if you have 2 small drivers (8"?) i would not suggest dipole (is that what you are siggesting with push push) as it would reduce bass.
lastly building 2 TLs is good when
a) you need speaker stands anyway; the TLs can be used as stands
b) your stereo pair is more likely to be near corners of a room (one on each side as stands for the main speakers). If you are using small drivers (think 8" or less) and your F3 is above 40-45Hz then the boost from the corner or near corner placement might help.
hope this helps.
BTW you aint slow. trust me. it takes me longer.
Re: Re: Push-push bass boxes... how directional are they?
Guys... These are more kind words than I get to hear in the average year. Specially once I start asking my questions.
Beer is on me, whenever wherever.
Tarun
PS: Am still preparing my response to both your posts. Have done a bit of looking up of Linkwitz' website, and am now trying to trawl through diyaudio looking for discussions of Orion's bass handling. Bear with me... I'll Be Back.
Variac said:
navin said:
Guys... These are more kind words than I get to hear in the average year.
Specially once I start asking my questions.Beer is on me, whenever wherever.
Tarun
PS: Am still preparing my response to both your posts. Have done a bit of looking up of Linkwitz' website, and am now trying to trawl through diyaudio looking for discussions of Orion's bass handling. Bear with me... I'll Be Back.
In todays world you have to be careful of statements like this. Next week we will probably be in the same town!
That is a good point of Navin's- bipole doubles your cost- no small matter.
In addition to requiring equalization, the open baffle bass
requires huge excursion. Note that Linkwitz uses those super Peerless subwoofers for bass. They are a major expense, and make me wonder how much non linear response he is getting. By facing one forward and one back he cancels out a lot of this. Reports are that even with all the circuitry, high excursion, etc, his are outstanding speakers.
Navin, I believe that by push push he is referring to bipole not dipole. Dave Planet 10 uses the term push/push instead of bipole because we keep confusing the 2 terms. (maybe I just did) Drivers are facing opposite directions and are wired in phase so they both push out at the same time.
With the Jordan, it doesn't look like you really need to tilt the open baffle as it's response doesn't rise that much.
To answer one of your original questions and design ideas:
I think you were basically proposing something like this ( I have added a few details)
A push push, transmission line about 16" wide for a base(with the drivers facing to the front and back) then continue the front upwards as an open baffle the same width, about 20" more with Jordan pretty close to the bottom of the open baffle. Should be at about ear ht. Maybe add a tweeter crossed over with a cap later if the high end isn't enough for you. Run the Jordan full range at first, cross over the woofers around 200 hz.
I'll bet you end up with a spectacular speaker system!
JX92 dipole
I should have joined this forum sooner. Whenever I start wondering about a speaker idea, someone's there ahead of me. I'll be interested to hear how the JX92 dipole turns out.
btw, given that the speaker on an open baffle rolls off at 6dB, wouldn't it be possible to select a bass unit which is 6dB more efficient and gain an octave that way? (Assuming a crossover for the bass unit.)
Colin
I should have joined this forum sooner. Whenever I start wondering about a speaker idea, someone's there ahead of me. I'll be interested to hear how the JX92 dipole turns out.
btw, given that the speaker on an open baffle rolls off at 6dB, wouldn't it be possible to select a bass unit which is 6dB more efficient and gain an octave that way? (Assuming a crossover for the bass unit.)
Colin
Okay... here's what I understood so far
I've scratched holes into my head trying to figure out all the stuff I just read, and then I searched the site for Linkwitz' Orion discussions, but couldn't get any info to figure out whether the Orion's bass drivers are set up like the Thor subwoofer or not. Learned a lot else while pursuing the Orion, but didn't learn what I started the pursuit for.
So, here goes:
I've scratched holes into my head trying to figure out all the stuff I just read, and then I searched the site for Linkwitz' Orion discussions, but couldn't get any info to figure out whether the Orion's bass drivers are set up like the Thor subwoofer or not. Learned a lot else while pursuing the Orion, but didn't learn what I started the pursuit for.
So, here goes:
- Mounting on an OB makes most drivers feel strange, because most drivers are designed to work in the presence of some extra "stiffening" which comes from the box at the rear.
- A driver has a Qts, which (if I've understrood it right) is its compliance on an IB (infinite baffle). This is a measure of the inherent "stiffness" of the cone's movement; higher Qts implies stiffer movement. The same driver, when fitted on any other baffle, will give rise to an overall Qts which is a sum-total of the driver's properties plus baffle plus box. That overall "thing" will have its own Qts. And it is this Qts which decides the low-frequency roll-off, etc. If the IB becomes finite B, this roll-off happens faster, i.e. at a higher frequency.
- When the roll-off happens, you "crank up the volume" by applying equalisation, or Linkwitz Transforms, or whatever. All this equalisation seems to be of the nature of the "Turbo Bass control" in boomboxes... it boosts the low frequencies to unholy levels. That makes the driver's cone move even further with each crest+trough of the signal. This, coupled with the absence of the "stiffening" presence of a box, makes the driver max out very fast. Hence, a high Qts is a good idea --- it means the driver is stiff enough to not bottom out easily. That's why you look for both high Qts and high Xmax (distance of cone travel).
- A dipole is an open driver, with rear wave 180-deg out of phase, whereas a push-push config (or bipole) has rear wave in phase. Dipoles will have very low sound wave intensities in the sides, thus making for reduced room reflections and giving you clean bass (i.e. less reflected booming and bouncing of sound)
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Assuming that all this is right so far, the following thoughts come to mind, listed in a hodge-podge mix like a Virar fast local:- JX92S suitable for dipole? Many attributes are attractive... those absolutely lovely delicate mids, the very precise, delicate aluminium foil cone which may show distortions if back waves in a small enclosure hit it, etc. But I don't know whether the JX92S will have enough Xmax or stiffness to deliver high SPL in a dipole. The sound quality will probably be very lovely (in fact, near ideal for a mid-bass, I can imagine) but the levels... I don't know. You guys can judge better.
- How do people speak so blithely of combining a push-push woofer box with a dipole everything else? If I have a push-push dual-driver woofer box crossing over at, say, 150Hz to an OB mid-bass (like the Jordan, say), then what happens to the rear wave at 150Hz? Total cancellation, at least in theory, like having two drivers side by side on one baffle in opposite phase. This should lead to severe non-linear frequency response curve of the rear wave. What does this rear wave sharp dip do to the sound reaching the listener in front? I don't know the answer, but if you say "Nothing", I'll know you're bullshitting me.
So, guys, how does one mix a dipole mid with a bipolar woofer? - How does Variac's Basszilla work (hey, Variac, I don't doubt that it does ), given that the woofer is a front-facing direct radiator and the mid is a dipole? The front waves from the two probably match well, but what about the audible effect of the fact that the rear waves are totally mismatched? They are better than the earlier bipole+dipole config, agreed, but the difference is quite drastic, nevertheless.
In general, if there's one thing I have lots of doubts about in dipole speaker design, it's to do with this carefree combining of dipole and non-dipole radiation patterns that I see all around. - I have begun to understand the OB concept in terms of baffle dimension and driver characteristics. What is the baffle dimension of Linkwitz' Thor subwoofer? (If the Orion has a similar woofer, this applies to it too.) This woofer is a tiny (by bass OB standards) box, with a front and back almost entirely made of radiating area. There's no baffle to speak of. Does this qualify as a super-small baffle, then? Am I then to understand that the entire negation of the 6dB/oct OB rolloff is being counteracted with strong equalisation pumped into some very-heavy-Xmax drivers? Will something the Adire Tumult (the one with the 34mm Xmax) be the right driver for this woofer?
- Adire says the Tumult is tailor-made for dipoles, but its Qts is just 0.36 --- isn't this too low? Or do we just equalise the hell out of it, and depend on its Xmax to make it behave itself?
- Why do people consider bipole bass boxes a Good Thing? Dipole bass boxes and bipole boxes can't both be Good Things, since they are practically opposite to each other. Does this mean that reduction of room resonances for bass is not that important after all?
- Does a typical dome tweeter have a rear wave? I know this is a total newbie question, but that's the level of my ignorance... really. This question becomes important because I'm currently sweating it out on the issue of dipole + non-dipole radiation patterns for rear waves. Of course, the tweeter question may not be important at all, because I read somewhere that OB becomes IB at something like 2KHz... This seems believable, because at high frequencies, the wavelengths may be too short to wrap around the OB.
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This here Mister Linkwitz is a smart cookie, I thought. He's got the vibration cancellation of Dave's push-push design and still delivered a dipole woofer. sfdoddy's home-made OB speakers, which use a Driverack for response shaping, must be lovely in all other respects but his woofer design does not enjoy the benefits of vibration cancellation. If you're reading this, Steve, does this become troublesome ever?
And Variac, you're almost right about the kind of speaker I was trying to work towards... do you do mind-reading as a day job? I was not thinking TL though, basically because I know nothing of TL. I was so thrilled to read about your Basszilla that I was essentially thinking of a very similar design, with a sealed bass box, a Jordan for the mids, and a tweeter. (The Jordan does need a tweeter, BTW. I'd posted somewhere else on diyaudio that my Jordans roll off the highs so early that even tape hiss is markedly less pronounced on them than on my Wharfedales with dome tweeters.) I first thought sealed direct radiator (front-facing). Then thought I'd go with push-push, to get the vibration cancellation (and because it seems kewl-er than just one boring driver in a sealed box). Then got into deep trouble worrying about the rear wave of a push-push woofer talking to that of an OB dipole mid. So here I am. I read up all I could find about the Orion, wondering what Mister Linkwitz does with his design, but couldn't find details.
But about the mid and tweeter, you were absolutely right. I'd make only one change to your guesstimated design... I'd not run the Jordans full range. I don't think they have it in them to even keep the mids clean if they get pumped up with the bass thumps. So I would have planned to do active line-level XO, and actually sharply roll off the feed to the Jordans below about 150Hz. The tweeter-Jordan XO could be a single-cap thing... I'm not sure an extra channel of amp is justified. What do you say?
So, left to myself, I was heading for a three-way design, with a box (i.e. non-OB) woofer, and an OB mid+tweeter. The woofer-mid XO would be an active XO, perhaps at 150Hz. The mid driver would be my beloved Jordans. The mid-tweeter XO would be a passive output-level (i.e. not line-level) single-cap thing, at a fairly high frequency (perhaps 5Hz or higher). I hadn't decided on the drivers for the woofer or the tweeter, and I had begun to wonder about ribbons. That was when the rear radiation pattern issues of dipole versus non-dipole hit me and laid me low.
Yours confusedly,
Tarun
PS: When Adire says the Tumult has 34mm excursion one way, does this mean that peak-to-peak movement is twice this?
The idea came from a design article in Elektor Electronics a few years ago.
The main driver drops off at 6dB per octave as the sound cancels at the lower limit of the baffle. So to get back the next lowest octave, you can equalise the driver and boost the output 6dB or crossover to a 6dB more efficient driver which would have the same effect on the same baffle. Pick a 12dB more efficient driver and with a bit of crossover fiddling presumably we can go two octaves lower.
This seems a more elegant way of going about it than a lot of power and heavy equalisation.
I hope I'm making sense - I'm waving my hands about a lot here, you know.
Colin
The main driver drops off at 6dB per octave as the sound cancels at the lower limit of the baffle. So to get back the next lowest octave, you can equalise the driver and boost the output 6dB or crossover to a 6dB more efficient driver which would have the same effect on the same baffle. Pick a 12dB more efficient driver and with a bit of crossover fiddling presumably we can go two octaves lower.
This seems a more elegant way of going about it than a lot of power and heavy equalisation.
I hope I'm making sense - I'm waving my hands about a lot here, you know.
Colin
Well, you have so many questions I thought I'd answer some easy ones at first, then go back and get some more
Tweeters don't have any rear output, so the tweeter won't ever be OB, even if mounted in an OB. I would suggest crossing it over with a single cap as you mentioned but WAY higher like 10k or wherever the Jordans start rolling off at about a 6db slope. That way you get the advantages of a full range driver.
First, Linkwitz is a very smart guy with the technical knowlege to design filters being his speciality. Then he designs a speaker that is all about filters-he knows his stuff Linkwitz/Reilly crossovers-that's him!
The Linkwitz bass module has reallly pretty big sidewalls in front of and behind the drivers. If you opened them out flat, the baffle would be 3 or 4 feet wide. Sidewalls work just like a wider baffle because the front waves have to travel further to get to the back.
Yes, exactly as you said: because of the Qts, we just equalize the hell out of them and let the huge xmax take care of things. Those high xmax Adire or Eminence drivers are probably just the ticket for this approach - and a lot cheaper than the Peerless.
The higher Qts drivers mentioned is a way to avoid so much equalization/ xmax and multiple, expensive drivers.
If you crossover the mid at 150 hz, you will need a bigger baffle- I'm guessing here, about 24 inches wide.
Think about the full range issue this way: If your Jordan works now at full range with the volume you are using, it will of course work full range in your new speakers just as well as long as the midrange baffle is big enough.
As we discussed before it is possible to make the mid baffle the correct size because the requirements for these frewquencies are a lot smaller.If you are planning to play them a lot louder you might have a problem. I don't think the drivers care if they are in an open baffle, if it is the right size, no sound that you care about is being canceled, thus no need for equalization.
Apparently having excess midrange sound in the room is agood thing I don't know why. Keep in mind that the "midrange" Jordan is really covering 90% of the music. If the bass driver can't keep up, just set the level higher- with active crossover - no problem.
Big point for placement and SAF. To sound best the OB has to be about 5 feet from the rear wall, so your brain interprets the reflected sound as ambience. Otherwise it just smears the sound and ruins the imaging.
More later.....
Tweeters don't have any rear output, so the tweeter won't ever be OB, even if mounted in an OB. I would suggest crossing it over with a single cap as you mentioned but WAY higher like 10k or wherever the Jordans start rolling off at about a 6db slope. That way you get the advantages of a full range driver.
First, Linkwitz is a very smart guy with the technical knowlege to design filters being his speciality. Then he designs a speaker that is all about filters-he knows his stuff Linkwitz/Reilly crossovers-that's him!
The Linkwitz bass module has reallly pretty big sidewalls in front of and behind the drivers. If you opened them out flat, the baffle would be 3 or 4 feet wide. Sidewalls work just like a wider baffle because the front waves have to travel further to get to the back.
Yes, exactly as you said: because of the Qts, we just equalize the hell out of them and let the huge xmax take care of things. Those high xmax Adire or Eminence drivers are probably just the ticket for this approach - and a lot cheaper than the Peerless.
The higher Qts drivers mentioned is a way to avoid so much equalization/ xmax and multiple, expensive drivers.
If you crossover the mid at 150 hz, you will need a bigger baffle- I'm guessing here, about 24 inches wide.
Think about the full range issue this way: If your Jordan works now at full range with the volume you are using, it will of course work full range in your new speakers just as well as long as the midrange baffle is big enough.
As we discussed before it is possible to make the mid baffle the correct size because the requirements for these frewquencies are a lot smaller.If you are planning to play them a lot louder you might have a problem. I don't think the drivers care if they are in an open baffle, if it is the right size, no sound that you care about is being canceled, thus no need for equalization.
Apparently having excess midrange sound in the room is agood thing I don't know why. Keep in mind that the "midrange" Jordan is really covering 90% of the music. If the bass driver can't keep up, just set the level higher- with active crossover - no problem.
Big point for placement and SAF. To sound best the OB has to be about 5 feet from the rear wall, so your brain interprets the reflected sound as ambience. Otherwise it just smears the sound and ruins the imaging.
More later.....
Variac said:
Not always true... Heils, BG ribbons (the bigger ones anyway), and ESL tweeters are dipolar and radiate out-of-phase out the back. You can also find vintage cone tweeters that are open back -- one of my favorites is the 2" alnico isophon -- and one could always remove the back from a chambered dome.
dave
Hey... great to meet another Elektor reader!
Good to meet you, Colin. I feel so starved of fellow Elektor readers in these online fora.
I suspect it is because there are very few American readers of Elektor. It is strange that Elektor is such a major magazine that it is published in four languages and probably two dozen countries (most of which publish the English language version, e.g. India), but they don't have an office in the US. I often feel that many of the discussions in fora like diyaudio would have been more interesting if more readers here had also been Elektor subscribers. Today, an American subscriber has no choice but to order from Elektor UK and pay international shipping. (The UK subscription is about UKP 38/yr, the US figure is about UKP 60/yr. Such a strategy wouldn't have sold more than 10 copies in India... the only reason it sells here is because it is reprinted in India.) Conversely, I'm sure European readers would have liked to see more advertising from American companies. Ah, well...
Elektor was my first hobby electronics DIY magazine; I bought the first issue released in India. I think that was 1983. I recently re-subscribed after a gap of many years, and found that the original seriousness and thoroughness of lab-tested designs has remained. Wow!
Luckily, there are a lot of European participants in diyaudio.
Tarun
Colin said:
Good to meet you, Colin. I feel so starved of fellow Elektor readers in these online fora.
I suspect it is because there are very few American readers of Elektor. It is strange that Elektor is such a major magazine that it is published in four languages and probably two dozen countries (most of which publish the English language version, e.g. India), but they don't have an office in the US. I often feel that many of the discussions in fora like diyaudio would have been more interesting if more readers here had also been Elektor subscribers. Today, an American subscriber has no choice but to order from Elektor UK and pay international shipping. (The UK subscription is about UKP 38/yr, the US figure is about UKP 60/yr. Such a strategy wouldn't have sold more than 10 copies in India... the only reason it sells here is because it is reprinted in India.) Conversely, I'm sure European readers would have liked to see more advertising from American companies. Ah, well...
Elektor was my first hobby electronics DIY magazine; I bought the first issue released in India. I think that was 1983. I recently re-subscribed after a gap of many years, and found that the original seriousness and thoroughness of lab-tested designs has remained. Wow!
Luckily, there are a lot of European participants in diyaudio.
Tarun
planet10 said:
Can I take this to mean that almost all typical dome tweeters, good or bad, are sealed-back monopoles? I had actually asked this question in some other thread, and had received partial answers from a moderator.
If I'm right, then what is this hole I find at the centre of the thick metal plate at the rear of some dome tweeters? I have seen this in some tweeters made by Peerless India, available here on Lamington Road (the electronics bazaar of Bombay). In another (again Peerless India) tweeter, I can clearly feel the hole, but it's covered with a paper label stuck on, which gives the part number and make. Are these things to be found in other tweeters too?
Tarun
Re: summary of what I've figured so far
If I'm right that it's indeed a Thor design, then I wonder how far one can carry forward the idea of side-walls being just baffle in a different shape. (I know this is the argument even SL applies, but I still wonder... I'm weird that way, you must've seen. ) If I take this idea to the extreme, I'll fix one driver at one end of a 100metre-long tube, and claim that I have an infinite baffle (plus the internal transverse standing waves and echoes, etc, of course). But does this analogy really stretch this far? Small side wings a few inches long, or an H-frame box of modest dimensions, may be fine. But where does this stop?
I can't help feeling that there should be a fundamentally different way to analyse a design like the Thor woofer. If left to myself, I'd take the entire box as a "black box", and take its exposed frontal and back areas as plane (i.e. flat) radiating surfaces, and then try to model its behaviour. This approach seems intuitively more "true". That's when all my questions about "Who took my baffle?" come up.
Of course, it is possible that once you analyse the Thor like a black-box the way I described, you may arrive at values of Qts and other parameters which, when plugged into existing OB formulae, will give you precisely the same frequency response as the older approach of side wings as wrapped-around baffle. Physics is strangely consistent that way.
Five feet?? The entire front-to-back distance in our living room is about 11-12 feet. (It's wider than it's deep.) Does this mean that dipoles are out for people like me? I had thought even two or three feet from the rear wall would be fine.
And when you get the time, can you tell me about the changing rear radiation pattern issue? (It's in my previous post.)
Tarun
Thanks for the patience... what can I say?Variac said:Well, you have so many questions I thought I'd answer some easy ones at first, then go back and get some more
Well, this is settled then. I've asked a follow-up Q to Dave and you, but it's essentially settled.
I too would have done precisely that, but can you believe it? I actually hear a very clear roll-off with tape hiss. It is clear that tape hiss is less than 8KHz. What do they mean when they say JX92 is a full-range? I'm totally surprised, frankly. Anyway, be it 10K or 8K, we agree on the essential approach.
Are you referring to the Thor sub-woofer, or the bass box of the Orion? I couldn't find any details of the design/construction of the Orion's bass box. I just presume that he had arrived at a good design with the Thor and would retain it with the Orion.
If I'm right that it's indeed a Thor design, then I wonder how far one can carry forward the idea of side-walls being just baffle in a different shape. (I know this is the argument even SL applies, but I still wonder... I'm weird that way, you must've seen.
) If I take this idea to the extreme, I'll fix one driver at one end of a 100metre-long tube, and claim that I have an infinite baffle (plus the internal transverse standing waves and echoes, etc, of course). But does this analogy really stretch this far? Small side wings a few inches long, or an H-frame box of modest dimensions, may be fine. But where does this stop?I can't help feeling that there should be a fundamentally different way to analyse a design like the Thor woofer. If left to myself, I'd take the entire box as a "black box", and take its exposed frontal and back areas as plane (i.e. flat) radiating surfaces, and then try to model its behaviour. This approach seems intuitively more "true". That's when all my questions about "Who took my baffle?" come up.
Of course, it is possible that once you analyse the Thor like a black-box the way I described, you may arrive at values of Qts and other parameters which, when plugged into existing OB formulae, will give you precisely the same frequency response as the older approach of side wings as wrapped-around baffle.
Physics is strangely consistent that way. Great! This makes things simple, provided I am willing to build the crossovers and EQ circuits. BTW, what does Adire mean when they talk of 34mm excursion? Is it 34mm peak-to-peak or 68mm peak-to-peak?
What's the mid XO frequency for your Basszilla? Is it about 300?
Five feet?? The entire front-to-back distance in our living room is about 11-12 feet. (It's wider than it's deep.) Does this mean that dipoles are out for people like me? I had thought even two or three feet from the rear wall would be fine.
And when you get the time, can you tell me about the changing rear radiation pattern issue? (It's in my previous post.)
Tarun
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