Juhazi was quoted as saying "Obviously a dipole bass doesn't benefit from "pressurizing" like sealed bass, which happens below lowest room mode. Remember that this is different from boundary reinforcement, which happens already higher in frequency, and differently with dipole/monopole."
With this thread wrestling with low freq, I think we need an airing of the "pressuring" question (AKA "cabin boost"). Is there any difference in bass propagation with OB (perhaps related to pressurizing) and if so, why?
I'd sure like a good reply.
(While Juhazi is correct in what he says about pressurizing, I think there isn't much debate that in real home rooms* the effect is less than trivial. There are substantial effects due to boundary reflections which is a different matter all together.)
B.
* assuming the room isn't air-tight and made of concrete on 6 sides
With this thread wrestling with low freq, I think we need an airing of the "pressuring" question (AKA "cabin boost"). Is there any difference in bass propagation with OB (perhaps related to pressurizing) and if so, why?
I'd sure like a good reply.
(While Juhazi is correct in what he says about pressurizing, I think there isn't much debate that in real home rooms* the effect is less than trivial. There are substantial effects due to boundary reflections which is a different matter all together.)
B.
* assuming the room isn't air-tight and made of concrete on 6 sides
I will try this. I imagine when adding the two curves their phase should be inverted.
Previously these DP-15's were mounted on a shallow H-frame and I made ground plane measurements. That would be a huge undertaking and probably will not happen now. I practically broke my back assembling them.
Linkwitz designed this baffle arrangement for his Phoenix system but I've not been able to find any info on how he modeled it.
Thanks Juhazi and Charlie
Just add the two curves (SPL only). The phase is already taken into account with the Edge model of the dipole.
This will be much easier than doing far-field measurements!
Slight correction to your math...
30 inches = 75 cm (1m is approximately 40")
90cm long would be good, too!
Remember, you want to try and have the width:depth ratio of the front and back "tunnels" of the H-frame around 2:1 to keep the Q of the line resonance relatively low. My dims don't quite make it... The longer you make it the wider it should be as well.
I happen to use this size because I can find cheap precut sheet goods (e.g. particle board, MDF, plywood, etc) that are 2x4 feet, or sometimes even 2x2 feet, and these are handy for experimenting, etc.
-you can also go with well-implemented Bass-shakers as an alternative (for bass and lower). (..dipole upper-bass lower-mid).
I just listened to Diana Krall's wonderful hifi-recordings, double bass is in big role. Even with modest neighbor-friendly spl bass sounds astonishingly right with just a 10"sealed+dsp, be upper parts dipole or not. Still, my partly dipole speakers sounded much better and natural than 3-way monopoles with similar 10" downfire bass. Of course one could use bigger speakers and nearfield etc. for dipole bass, but why make it so difficult? Room response, positioning is perhaps most important factor if the speaker is capable of going lower than 40Hz.
I understand and identify that certain amount of perfectionism is built-in in diy-hifi, like in mountain-climbing. No offense to Charlie, Nelson et.al. ! Now I try to keep sordino plugged in for a while.
ps. Synthetic bass like from Yello or Laurie Anderson are too easy to reproduce, you don't have reference to how it should sound! And I don't like them either. This is a nice pick for acid test, lots of power below 40Hz, even down to 10 (at least on European CD) - The Road To Escondido (U.S. Version) by J.J. Cale on Spotify
I understand and identify that certain amount of perfectionism is built-in in diy-hifi, like in mountain-climbing. No offense to Charlie, Nelson et.al. ! Now I try to keep sordino plugged in for a while.
ps. Synthetic bass like from Yello or Laurie Anderson are too easy to reproduce, you don't have reference to how it should sound! And I don't like them either. This is a nice pick for acid test, lots of power below 40Hz, even down to 10 (at least on European CD) - The Road To Escondido (U.S. Version) by J.J. Cale on Spotify
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You know, after all the comments, I think I will build an upcoming project with the option of a monopole sub. This was to be a 3-way nude speaker from 100Hz and up, and then H-frames below. But I realized I can easily place a closed box sub directly below the nude woofer of the 3-way and create a cardioid pattern in the crossover region, with monopole below, and dipole above. It might be that in smaller spaces the monopole low end would be better, and in larger spaces the dipole (H-frame) low end would be better. It would be an interesting experiment.
The real question is over what frequency range should I operate the system in cardioid. For practical reasons, it can't be below about 80Hz but it could be from 80-160Hz potentially.
I can still build the H-frame sub(s) and then I can switch them in and out easily (I use DSP crossovers) and see if I prefer one or the other.
The real question is over what frequency range should I operate the system in cardioid. For practical reasons, it can't be below about 80Hz but it could be from 80-160Hz potentially.
I can still build the H-frame sub(s) and then I can switch them in and out easily (I use DSP crossovers) and see if I prefer one or the other.
Still, one funny thing about bass. I have digitized many of my old vinyl LPs with EAC and Audacity. Sadly my gear is not high-end and has lots of rumble and cartridge resonance - I use highpass filters to cut it out, like 24dB/oct at 30Hz. But that easily removes the "vinyl sound" too, there is lots of ambience in low bass, even it is artefact for the most! That much low bass would be dangerous for typical BR 2-way hifi-speakers, but in old days most people had closed box speakers and all amplifiers had low-cut (rumble) filters.
Modern digital recording-producing process is often misused and bass below 40Hz is rare species. With speakers capable of sub-40Hz and without reflex will reveal these huge differences in distributed recodings easily.
Modern digital recording-producing process is often misused and bass below 40Hz is rare species. With speakers capable of sub-40Hz and without reflex will reveal these huge differences in distributed recodings easily.
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For sweet-spot-only duty in a small room a near-field OB mono-bass (15"...21" nude is nice for this) mounted behind the seat is also an option and if you couple it to the chair mechanically it doubles up as a shaker (but then maybe better float the chair on dampers). Should give serious impression of very deep bass even down below 20Hz.
Interesting
I do not know if it would work regarding distance and orientation (tilting), but a friend of mine has the Poäng with the footstool. The front opening (listeners side) is about 30x60cm: one could fit 2x 12"!Attachments
IIRC I used 100Hz linear phase 1st order Neville-Thiele as provided by the Acourate Toolbox for DSP XOver and room correction package. I actually happened to have an IKEA Poang and the 18" 30cm behind the stool was located at chest-height firing 20° or so upwards as simply established by suspending the driver from two adjacent mounting holes with ropes. From that angle our sensitivity to noise etc is lowest, it seems.
In spite of this, say rather crude, quick&dirty setup I found the result was stunning. Headphone-like bass... but that was a weak point long-term, for most of the music I listen to I prefer the "monopole slam" in the low bass. Plus form-factor and aesthetic reasons made me gave up this route.
In spite of this, say rather crude, quick&dirty setup I found the result was stunning. Headphone-like bass... but that was a weak point long-term, for most of the music I listen to I prefer the "monopole slam" in the low bass. Plus form-factor and aesthetic reasons made me gave up this route.