Hi,
How do you guys justify the following 2 (in the midrange):
1. constant directivity
2. severe EQ under dipole peak
🙂
How do you guys justify the following 2 (in the midrange):
1. constant directivity
2. severe EQ under dipole peak
🙂
1) A number of people emphasize the primary importance of on and off axis frequency response, including Toole, Geddes and Linkwitz. Toole has done substantial research regarding this point of view. I've been finding that each time I improve these two things, and get closer to constant directivity, there is an easily audible improvement in the perceived quality of the music.
2) Without severe EQ, it would sound like garbage! My impression is that EQ is a lesser evil than no EQ, particularly if it is active and multiamped. One of the advantages of using increasing the number of 'ways' is that each driver needs less EQ, has higher power handling and SPL headroom, less distortion, and higher sensitivity. Each driver can have a baffle tailored to its needs, and the drivers can easily be physically time aligned. All for just a little EQ. Whats is not to like?
[Here are a couple counter questions - do any comparable systems use no EQ/XO? and what is more benign, passive or active XO?]
2) Without severe EQ, it would sound like garbage! My impression is that EQ is a lesser evil than no EQ, particularly if it is active and multiamped. One of the advantages of using increasing the number of 'ways' is that each driver needs less EQ, has higher power handling and SPL headroom, less distortion, and higher sensitivity. Each driver can have a baffle tailored to its needs, and the drivers can easily be physically time aligned. All for just a little EQ. Whats is not to like?
[Here are a couple counter questions - do any comparable systems use no EQ/XO? and what is more benign, passive or active XO?]
Yes.
I can (maybe only kind of) understand you by the viewpoint of the bass section. Dipole bass rarely got a 'big enough' baffle area to support a non-EQ'ed response and we almost always use it under the dipole peak with 'severe' EQ. And the small baffle of my dipole bass does not bother me at all 😀 Applying this to the midrange, then I think the EQ is no more 'severe'.
I can (maybe only kind of) understand you by the viewpoint of the bass section. Dipole bass rarely got a 'big enough' baffle area to support a non-EQ'ed response and we almost always use it under the dipole peak with 'severe' EQ. And the small baffle of my dipole bass does not bother me at all 😀 Applying this to the midrange, then I think the EQ is no more 'severe'.
Cuibono,
Thanks a lot for showing your measurements! They look very much like the ones I did on my 8" and 5" drivers yesterday.
It's a really interesting approach to use a lot of "ways", and only use the drivers below the dipole peak. This gets more and more difficult as the frequency increases.
I have managed to cross over below the dipole peak with the 5" and 8", but the 21" woofer is crossed over right at its dipole peak.... and that peak is 15 dB at 90 degrees! Guess I should try to cross over a bit lower... but the 8" mid simply cant handle it. Add an other driver? Maybe a 12" to cover 200 - 400 Hz? 🙂
Thanks a lot for showing your measurements! They look very much like the ones I did on my 8" and 5" drivers yesterday.
It's a really interesting approach to use a lot of "ways", and only use the drivers below the dipole peak. This gets more and more difficult as the frequency increases.
I have managed to cross over below the dipole peak with the 5" and 8", but the 21" woofer is crossed over right at its dipole peak.... and that peak is 15 dB at 90 degrees! Guess I should try to cross over a bit lower... but the 8" mid simply cant handle it. Add an other driver? Maybe a 12" to cover 200 - 400 Hz? 🙂
For the lower mid, I would use a 10" driver, but an 8" or 12" should be okay. I would use a modest baffle, making sure the peak was above 500Hz. I would do this to preserve the driver's sensitivity. A 12" with no baffle, and plenty of Xmax is likely to work just the same. You should be able to get down into the mid-100Hz that way.
If your lower mid driver is having difficulty with the room, something to consider is that the XO between woofer and lower mid will have a very long wavelength - it is possible to position the woofer separately from the rest of the system, making it possible to get the best in room response for both the upper and lower sections separately. Then correct the phase difference of the woofer.
If your lower mid driver is having difficulty with the room, something to consider is that the XO between woofer and lower mid will have a very long wavelength - it is possible to position the woofer separately from the rest of the system, making it possible to get the best in room response for both the upper and lower sections separately. Then correct the phase difference of the woofer.
After giving it some thought (and a good night's sleep), I think I should replace the 21" woofer with one or two 15" instead for lower mid/bass. This would move the woofer dipole peak well above the 350 Hz XO.
The main speaker will then become an array of 15"-8"-5"-AMT-5"-8"-15".
An other thing is that the unbaffled 21" requires too much EQ to go deep into the 30 Hz bass range. It has got enough excursion capacity , but the problem is that the harmonic distortion products are much higher than the fundamental because of the massive roll-off. The deep bass sounded a little too light.... I tried some sinewaves to check it out - 30 Hz didnt sound like 30 Hz at all, more like a defective Hammond organ... I solved it temporarily by crossing over to my 18" closed subs a bit higher, approx 35 Hz.
I think it might be better to build some dedicated H-baffle subwoofers, using a lot of 18" or 21" drivers, and let them run up to maybe 60-80 Hz, where two 15" take over the show.
Will work on a little drawing to visualize my thoughts for you.
The main speaker will then become an array of 15"-8"-5"-AMT-5"-8"-15".
An other thing is that the unbaffled 21" requires too much EQ to go deep into the 30 Hz bass range. It has got enough excursion capacity , but the problem is that the harmonic distortion products are much higher than the fundamental because of the massive roll-off. The deep bass sounded a little too light.... I tried some sinewaves to check it out - 30 Hz didnt sound like 30 Hz at all, more like a defective Hammond organ... I solved it temporarily by crossing over to my 18" closed subs a bit higher, approx 35 Hz.
I think it might be better to build some dedicated H-baffle subwoofers, using a lot of 18" or 21" drivers, and let them run up to maybe 60-80 Hz, where two 15" take over the show.
Will work on a little drawing to visualize my thoughts for you.
About the bass, I'm thinking of suspended driver with baffle -- driver is suspended behind the baffle (like rear mounted), and kept a small gap with the baffle.
The key is how the deal with the gap. I think of the hollow foam (or rubber) gasket used in windows, doors... etc. There're various shapes and sizes in the hardware stores. Yes, I know it somewhat affects the 'freedom' of the suspension, but can gain some dB back, so maybe a good compromise.
I've been thinking of it but not done anything yet.
StigErik, I think you are the no.1 fast builder here😀 Maybe you can give it a try well before me🙂
The key is how the deal with the gap. I think of the hollow foam (or rubber) gasket used in windows, doors... etc. There're various shapes and sizes in the hardware stores. Yes, I know it somewhat affects the 'freedom' of the suspension, but can gain some dB back, so maybe a good compromise.
I've been thinking of it but not done anything yet.
StigErik, I think you are the no.1 fast builder here😀 Maybe you can give it a try well before me🙂
I'll think about it... Window rubber seal is what I used for soft-mounting the 8" and AMT in my pyramid baffles. It worked will with tweeter and midrange. I'm not sure if it will work with much lower frequencies. The sheer weight of large woofers (15-20 kg) makes it difficult to softmount them to the baffle as well.
An interesting approach could be to build a H-baffle with the driver hard-mounted, but suspend the baffle - just hang it from the ceiling. That trick worked really well with the bare drivers.
An interesting approach could be to build a H-baffle with the driver hard-mounted, but suspend the baffle - just hang it from the ceiling. That trick worked really well with the bare drivers.
Below is a drawing of one possible solution here.
One main dipole, hung from the ceiling - 15" - 8" -5" -AMT - 5" - 8" - 15"
H-frame subwoofers with three 21" (could also be four 18").
I'm fairly confident that the main dipole will work well, but I'm more in doubt with the H-frame woofers. Guess I have to employ a rather deep frame to increase the effective baffle width.
I've seen that crazy W-baffle with oodles of 15" drivers. It makes me wonder if three 21" or four 18" per side is enough down to 20-25 Hz?
One main dipole, hung from the ceiling - 15" - 8" -5" -AMT - 5" - 8" - 15"
H-frame subwoofers with three 21" (could also be four 18").
I'm fairly confident that the main dipole will work well, but I'm more in doubt with the H-frame woofers. Guess I have to employ a rather deep frame to increase the effective baffle width.
I've seen that crazy W-baffle with oodles of 15" drivers. It makes me wonder if three 21" or four 18" per side is enough down to 20-25 Hz?
No!
I meant the woofer is still suspended, just make it close to the baffle. The soft gasket is used only for sealing the gap, not for support.
I doubt it.
I once tried 3 18" per side, severely EQ'ed, but the low 20's were not boosted effectively. The RTA readings barely changed when I made huge 20Hz boost on EQ. Some gain on 25Hz can be made. (I didn't use up the excusion of the woofers.)
Dipole bass is not good at pressurizing the room.
Yes - dipole bass does not pressurize the room like sealed subwoofers. I think that's one of the reasons dipoles sounds so good, and why I would like dipole bass down as low as possible. If that means 25 Hz at best, I'm happy with that.
I do remember that the baffled 21" was much better at 30 Hz than without baffle. With a large enough H-baffle and enough drivers, I hope 25 Hz will be possible? (please? 🙂 )
Guess I should build a really deep H-frame to check this out to begin with.
I do remember that the baffled 21" was much better at 30 Hz than without baffle. With a large enough H-baffle and enough drivers, I hope 25 Hz will be possible? (please? 🙂 )
Guess I should build a really deep H-frame to check this out to begin with.
I think you cannot make a deep H frame because you will catch quarter wave resonance. it depends on the crossover frequency ?
If you want the peak 2 octaves above 100Hz (400Hz), the total deep will be 0.42m (16.5")
If you want the peak 2 octaves above 100Hz (400Hz), the total deep will be 0.42m (16.5")
I wish to cross over the H-baffle subs around 50 Hz, so they could be rather deep without getting into resonance problems.
Yes ! If you consider resonance two octave higher (200Hz ) because more easy to suppress the peak, no phase problem 340/(2xdeep) 0.84m (33") total deep.
Dont think I can make them THAT deep, they have to fit in my room too, with enough free space behind them. Around 50 cm total depth is what I had in mind.
Alert by your findings, Cuibono and Stig Erik, I've (re)done some outdoor polar measurements of my 6" and 8" by myself.
Whoow freezing cold in the early dark....
I do have to repeat without the minimalistic baffle to gain confidence but there definitely *is* room for improvement – exactly like you said.
Interestingly (and as I remember) the 6" shows significant worse polar peaks than the 8". (OB being roughly 30cm wide)
I was ready to order these 4" Illuminator ScanSpeak's but the point is, excursion and thus intermodulation would go through the roof – or – bandwidth would be way less than even a single octave when I checked back
http://members.aon.at/kinotechnik/diyaudio/dipol/doppler_intermodulation_distortion.xls
All my design was started to keep IM at or below 1% at 120dB SPL.
No way to get this with such tiny 4" speakers nude.
So, for now I'm a little bit lost – either to skip my IM goal or to live with some polar wiggles in the upper OB department.
😱
Anyway – thanks a lot Stig Erik and Cuibono for pointing this out in full clarity!
Michael
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Here's the design ideas I'm thinking of right now.
Four 18" in H-baffle
The rest hung from the ceiling, or a very tall frame.
Four 18" in H-baffle
The rest hung from the ceiling, or a very tall frame.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Joined 2003
Here's another approach for your dipole woofers. (This is Monte Kay's system.) He uses 24x15" in two towers. Neat thing about this is the force cancellation achieved with opposing driver pairs.
Yet another would be a damped U-frame with heavy wool felt across the back of the U. ~6-12mm of F13 felt should substantially reduce the dipole peak.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Yet another would be a damped U-frame with heavy wool felt across the back of the U. ~6-12mm of F13 felt should substantially reduce the dipole peak.