[Graham Maynard]

Hi Erling,

Your measurements show what looks like an approximate loss of 3dB from the same low measuring position when the U-frame is standing;  also there is no significant dip which would correspond to the simulation software generated 330Hz dip in Rudolph's Reply#10 above.

Last year I ran a novel cabinet capable of producing reasonably clean bass.  The cabinet was approx 4.5x1x1ft with two 6x9" drivers in push-push on opposite sides at one end of the long dimension; there was a U-line between the drivers which was resistively vented close to one driver only.
With the drivers at floor level it would powerfully excite room modes.
With the drivers 4ft above floor level the LF reproduction was firm, clean and much less tiring to listen to.

You could still hear the 'box', which I do not like, but this comparison showed me that whilst bass drivers at floor level can provide Home Theatre 'power', they also become noticeable in a way which detracts from enjoying music due to their increased effect upon the room.

Also, when sitting on the floor close to this monopole when the drivers were say 2ft above ear level, it was not possible to hear some low frequencies, say below 25Hz, even though you could see the cones shifting air (as David has observed with his Dipole), this being due to the the wavelength and the room, though the handle on the bathroom door at the end of the hall could be vibrating away.

Hence I want my bass drivers to be mounted vertically and not beside each other, so that room modes intrude less upon reproduction.

So I wonder if you did any laid-flat/standing listening comparisons when you took those measurements.  Any observations ?

Hi Rudolph,

A response dip around 300Hz (plus a lift around 400Hz) appear when you raise the driver.  Is the software accounting for dimensional effects due to U-frame dimensions, or floor bounce to the listening position ?

Cheers ........... Graham.

[scorpion]

Hi Rudolf and Graham,

Another measurement. I moved around a bit and this is at 3 m distancance and at 90 cm high, about earlevel. I think that your arguments are documented.
It is not the Venetian Blind units, I have to many 12" laying around. I played these together with Monacor 130X/8s with good results. However when you compare these quite cheap units to a very good construction like A&D 1524 (also very cheap) they simply don't match even if you can play lower with the BDRs. I sincerely hope that the Eminence Alpha 15s will prove better. The U is also a bit 'longer' than MJK suggested 26.5 cm vs suggested 20 cm. My only intention was here to prove MJK's case. You can go really low with suitable units. This last measurement also reveals the building up for the main resonance at about 230 Hz, the 50 Hz buildup is room dependent.



/Erling

[Rudolf]

... With the drivers at floor level it would powerfully excite room modes.
With the drivers 4ft above floor level the LF reproduction was firm, clean and much less tiring to listen to.

You could still hear the 'box', which I do not like, but this comparison showed me that whilst bass drivers at floor level can provide Home Theatre 'power', they also become noticeable in a way which detracts from enjoying music due to their increased effect upon the room.

A fine example of exciting the vertical room mode with a monopole.

Also, when sitting on the floor close to this monopole when the drivers were say 2ft above ear level, it was not possible to hear some low frequencies, say below 25Hz, even though you could see the cones shifting air (as David has observed with his Dipole), this being due to the the wavelength and the room, though the handle on the bathroom door at the end of the hall could be vibrating away.

If you are sitting right in a pressure node of a room mode you hardly hear it, regardless how much it is shaking the door in its pressure peak at the room wall. Did you check with moving to another position in the room?

Hi Rudolph,
A response dip around 300Hz (plus a lift around 400Hz) appear when you raise the driver.  Is the software accounting for dimensional effects due to U-frame dimensions, or floor bounce to the listening position ?

Cheers ........... Graham.

Yes, the simulation accounts for all U-frame dimensions and for the floor bounce with regard to a specific listening position. For both curves the listening position is 1 m in front of the baffle and at 80 cm heigth.
So it does not really reflect Erlings measurements, but is simply an exercise in lifting a driver in a U-frame.

[ttan98]

Rudolf,

Your website contains some very useful info I like to understand better, unfortunately I don't understand German.

If you have the time can you translate them in English, over time, ie section by section, I understand there are lots to translate.

Cheers.

[Graham Maynard]

Hi Rudolph,

I tend to not check on personal details, so did not know you had a Dipole Website,and so much experience behind your posts.  Excellent.

Hi Ttan,

I'm so glad you found that, and I look forwards to some interesting reading.

Open up this translation facility;-
http://uk.babelfish.yahoo.com/?fr=avbbf-uk

delete the 'http://' in the translation address window;  right click and paste in the address for Rudolph's Website;-
http://www.dipolplus.de/frameset.htm

select German to English, hit 'Translate' and wait;

you will get a reasonable translation, and, the other pages will then open within the translation window without having to do each separately.

Cheers ......... Graham.

[scorpion]

Like Swedish and French, German is very easy to read. It is pronounced exactly the way it is spelled.
It may be more difficult to understand though ! 

Sorry for the OT, but I couldn't resist.
And of course Rudolf is one of those very competent guys that is good to have around.

/Erling

[ttan98]

Hi Rudolph,

I tend to not check on personal details, so did not know you had a Dipole Website,and so much experience behind your posts.  Excellent.

Hi Ttan,

I'm so glad you found that, and I look forwards to some interesting reading.

Open up this translation facility;-
http://uk.babelfish.yahoo.com/?fr=avbbf-uk

delete the 'http://' in the translation address window;  right click and paste in the address for Rudolph's Website;-
http://www.dipolplus.de/frameset.htm

select German to English, hit 'Translate' and wait;

you will get a reasonable translation, and, the other pages will then open within the translation window without having to do each separately.

Cheers ......... Graham.

Thanks Graham,

Automatic translator can never come close to human translation(in some cases I find I only get the gist of what is said in the text ie after it has been translated), a good compromise is to use automatic translator and personally edited by Rudolf..that way the translated text would be more accurate, at the same time quicker.

If you are perfectionist you don't want to do that.

[Rudolf]

You guys are killing me! 

@Erling
While I would admit that swedish articulation is better to understand (at least for me) than danish - whenever I was in Sweden (just twice) I was very glad, that virtually every Swede is fluent in English and most Swedes still understand German in a good way.
Telling us that French is "pronounced exactly the way it is spelled" is funny. I always thought that almost a quarter of the letters in a french word are written, but never vocalised. (thinking of "beaujolais" ...)

@Graham
Thank you for your nice comment  .
I believe it was MJK himself who first introduced me to a babelfish translation of dipolplus. I was surprised how well (and understandable) short sentencies were translated. Unfortunately German lends itself to some tricky nesting of main and subordinate clauses. And I am prone to like such nestings in a way babelfish has trouble to follow.
But I can assure you: If babelfish doesn´t understand me, I might not have understood myself really.

@ttan98
after putting my dipole website online I have learned two things:
- how little I knew then about dipoles (honestly!)
- that people don´t need that much theoretical blurb, but practical considerations like "what are the benefits and downsides, when I make a baffle wider?" or "how can clever placement of an OB avoid divorce?".

So next time I would do dipolplus in a completely different way. May be that I have some more spare time later this year and can come up with a revamped version. Time will show ....

Rudolf

[scorpion]

It was a saying by my old French teacher, that French always was pronunciated like it was spelled.
He was of course right, once you know the written word you also have a very good hint of the pronunciation.
But as should always be the case and this was certainly a understatement, you do really have to know the language to understand ! 
But otherwise  French is no more difficult than Swedish or German.

As a general comment you are quite right, most Swedes understand and speak guite a bit of English probably because we are one of the most american influented countries in Europe. For good or worse. Also in television and in movies we never had any translations, only subtitles, and in fact I think this is only for good to
learn the other language. German has had an upswing because of the swedish EU membership. But it is a long way back to the dominance in the early 1900s.

/Erling