[roscoe65]

All of the Omega driver models are available in a variety of enclosure volumes, from desktop small enclosures to largish floorstanders.  This speaks to the versatility of the drivers themselves in that they succeed in so many different configurations.

We generally assume that the larger enclosures offer better [deeper] bass.  This begs a couple of questions:

1.  Does the deeper bass from the larger enclosure come at the price of some other attribute that we would experience in a smaller enclosure?
2.  For a driver such as the RD5, which is in several different enclosure volumes, is there an "optimum" enclosure volume?  Is the 18l volume of the Super 3 XRS the optimum volume and tuning for the RS5?
3.  Do we need additional enclosure volume for RS5 1.5 way speakers?  The 1.5 floorstander is of greater volume than the Super 3 XRS while the new 1.5 monitor is of similar volume to the old Super 3U and current Super 3 XRS.

Any insight would be much appreciated.

R

[seikosha]

Hi Roscoe65,

I can only answer your first question.  I've got the RS5 in a monitor sized and also XRS cabinets.  Going to the XRS from the smaller cabinet, one doesn't lose anything.  The sound is very similar just with a little more foundation and also a slightly warmer midrange (which could be due to the wider cabinet).  For me, nothing is lost by going to the larger cabinet.  The difference between the two is tangible, but not a drastic change.

I do know that years ago, Louis made a "Stick" version of the RS5 which was a larger (taller, but skinnier) cabinet than the XRS.  I believe he advertised it as the time as having a bit lower bass than the XRS.  It's been discontinued for awhile, I don't think it sold very well compared to the XRS.  The new Decware speaker's cabinet looks very much like the older stick design.

[Canada Rob]

I can only answer your first question.  I've got the RS5 in a monitor sized and also XRS cabinets.  Going to the XRS from the smaller cabinet, one doesn't lose anything.  The sound is very similar just with a little more foundation and also a slightly warmer midrange (which could be due to the wider cabinet).  For me, nothing is lost by going to the larger cabinet.  The difference between the two is tangible, but not a drastic change.

+1

[Ultralight]

If you want more 'body' with the smaller enclosures, move it closer to the floor and point up. You may be surprised at how much you gain.  I do wonder how much of the floor standers' increased bass and mids came from the driver being closer to the ground, and how much due to the enclosure size. 

[FullRangeMan]

Any cone speaker driver has a box volume range, min, optimum and max.
Seems the max range will delivery more bass.
Over the max litrage there is a risk of increasing the cone excursion beyond the Xmax.
In extreme cases of large boxes it may occur the VC beat up with the motor bottom or magnet plate.

[roscoe65]

If you want more 'body' with the smaller enclosures, move it closer to the floor and point up. You may be surprised at how much you gain.  I do wonder how much of the floor standers' increased bass and mids came from the driver being closer to the ground, and how much due to the enclosure size.

That is a good point UL.

There should be no logical difference in bass output between the Super 3U and the Super 3XRS based solely on cabinet volume with identical tuning.  However, we intuitively assume bass gain for the XRS for a number of reasons:  wider baffle extending to the floor, which changes the radiation pattern closer half and even quarter space (in contrast to the full space radiation pattern of a stand-mounted monitor), and the wider baffle which shifts the baffle step frequency a bit lower.  I'm not sure how much real world difference the shift from a 8" wide baffle to a 11" baffle makes in that context.  With the narrower baffle we would expect to see the baffle step at 570Hz, while with the wider one we would expect it to occur at 414Hz.  That difference alone would imply a fairly significant effect in the vocal range, especially in male vocals.  I would expect it to be more full-bodied.

Additionally, in the XRS the port is located close to the floor.  We are again radiating into quarter space and taking advantage of coupling to the floor and to a greater or lesser extent the front wall depending on positioning.

With the renewed interest in Louis' 1.5 way models, it has made me begin to think more deeply about the different configurations possible.  In looking at his "sold" Outlaw models, I note that more have the two drivers located physically very close (about 5.5" CTC or so), with one exception:  an older, larger 1.5 RS5 model with a Super Alnico Monitor sized cabinet.  This speaker had the drivers about 10" CTC.  At a 500hz cutoff frequency, conventional wisdom dictates that we locate drivers with 1/4 wavelength, or no more than 6.5".  The greater distance is closer to 1/2 wavelength.

Is there an opinion about the maximum distance between the drivers where they will still present as a point source?  Our listening distance will almost always be much greater than this distance (l) and a rule of thumb asserts that at distances greater than 1/2 the radiation pattern will behave like a point source.  At higher frequencies (>1khz) , we are concerned about comb filtering but at the frequencies below 500hz ripple from baffle diffraction and/or room effects would likely overshadow any comb filtering.  It could be that locating the second RS5 driver closer to the floor could further reinforce the bass while still maintaining the effect of a point source.

[JLM]

Any cone speaker driver has a box volume range, min, optimum and max.
Seems the max range will delivery more bass.
Over the max litrage there is a risk of increasing the cone excursion beyond the Xmax.
In extreme cases of large boxes it may occur the VC beat up with the motor bottom or magnet plate.

Agreed.  This thread reminds me of the famous E. J. Jordan JX92S (in production for 50 years) extended range driver.  It reported was successfully used in sealed designs, ported designs, open baffle designs, and more.  It's reputation as the "be all" driver was exceeded only by the company's claims.

[Louis O]

That is a good point UL.

There should be no logical difference in bass output between the Super 3U and the Super 3XRS based solely on cabinet volume with identical tuning.  However, we intuitively assume bass gain for the XRS for a number of reasons:  wider baffle extending to the floor, which changes the radiation pattern closer half and even quarter space (in contrast to the full space radiation pattern of a stand-mounted monitor), and the wider baffle which shifts the baffle step frequency a bit lower.  I'm not sure how much real world difference the shift from a 8" wide baffle to a 11" baffle makes in that context.  With the narrower baffle we would expect to see the baffle step at 570Hz, while with the wider one we would expect it to occur at 414Hz.  That difference alone would imply a fairly significant effect in the vocal range, especially in male vocals.  I would expect it to be more full-bodied.

Additionally, in the XRS the port is located close to the floor.  We are again radiating into quarter space and taking advantage of coupling to the floor and to a greater or lesser extent the front wall depending on positioning.

With the renewed interest in Louis' 1.5 way models, it has made me begin to think more deeply about the different configurations possible.  In looking at his "sold" Outlaw models, I note that more have the two drivers located physically very close (about 5.5" CTC or so), with one exception:  an older, larger 1.5 RS5 model with a Super Alnico Monitor sized cabinet.  This speaker had the drivers about 10" CTC.  At a 500hz cutoff frequency, conventional wisdom dictates that we locate drivers with 1/4 wavelength, or no more than 6.5".  The greater distance is closer to 1/2 wavelength.

Is there an opinion about the maximum distance between the drivers where they will still present as a point source?  Our listening distance will almost always be much greater than this distance (l) and a rule of thumb asserts that at distances greater than 1/2 the radiation pattern will behave like a point source.  At higher frequencies (>1khz) , we are concerned about comb filtering but at the frequencies below 500hz ripple from baffle diffraction and/or room effects would likely overshadow any comb filtering.  It could be that locating the second RS5 driver closer to the floor could further reinforce the bass while still maintaining the effect of a point source.

Hi roscoe65,

Thanks for all the great posts everyone and great point roscoe65. Your 3 XRS findings are totally correct. The 3U and the XRS are the same volume. The lower port, wider baffle and being closer to the floor makes a pretty big difference. Originally the XRS stood for eXtended Room System.

Your correct in regard to the spacing of the 1.5 way Outlaws on the site. The model with the larger spacing is my original and that speakers is over 11 years old now. As the concept developed and I refined it I went with closer spacing as it played and sound-staged better to my ears. Also to me looked better too. The cutoff of the lower driver in the original was a bit lower too.

The RS5's are very versatile and although I haven't tried all the possibilities I have been in the range of 10 to 28 liters in single driver configuration. Hard to say what is best and it's always a give and take. The super 3 XRS has been the most popular though.

I'll post a picture if the new Super 3 High Output that shows the depth of the cabinet. It's pretty large at 35" tall x 8" wide x 14 deep. The picture is in my shop computer so I will post it when I return to the shop.

I'm very happy you like the 1.5 way concept and I have to say that I did make a mistake about the sensitivity. It's should be 97.5 dB. I also made the Alnico High Output cut off at 200Hz permanent.

In 2017 I will be prototyping some more versions with more lower drivers and will look into the possibility of 16 Ohm Alnico's and RS5's.

Thanks again,
Louis

[roscoe65]

It sounds like the Super 3 HO tower will more or less 40 liters after we reduce the volume of internal bracing.  That's not that far off from the volume (per driver) of the Super 3U or Super 3 XRS, which strikes me as what has apparently settled out as the "optimum" volume for the RS5.

I re-read some old posts and noted that the original 1.5 way monitor was low passed at 300hz.  I think you are onto something in that the main driver will dictate the helper woofer crossover point.  With the rising response of single drivers, we would expect to need low frequency assistance at a higher frequency with a 4.5" driver than a 6.5" one.  As I have noted in another post, typical 4.5" drivers of reasonable efficiency will begin rolling off at 1-2 dbB/octave below 1khz.  Your practice of bringing a second one at 6dB/octave at 500hz would appear to perfectly balance that rolloff.

500hz also is typically cited as the point of equal power distribution, require 50% of amplifier power below this frequency and 50% above.  This, combined with the RS5 FR being 3dB down below 1khz strongly implies the "need" for twice the efficiency below 500hz.  The 1.5 way configuration appears to simple add twice the surface area (and twice the efficiency) below this point in a seemingly innocuous way.

We still can't escape the realities of physics, and the deepest bass - if it is important to us - may still require supplementation below 50 hz or so.  That being said, we would no longer need to extend this bass reinforcement into the mid or upper bass.

I'm not 100% convinced that 16 ohm speakers are necessary.  When paralleling driver below 200-500hz only, it does not appear that we are actually creating  4 ohm speaker.  Speaker impedance is nominal at best, and in the case of full range drivers we generally expect to see a rising impedance both at high and low frequencies.  The 500hz inductor applies a higher impedance at the lowest impedance region of 500-1,000 hz.  I would expect the region of 100-700 hz to be about 6 ohms or so, with frequencies both above and below presenting a higher impedance of 8-12 ohms.  I think that this nominal 6 ohm impedance is ideal for the Decware 6 ohm output transformer.  Other amps may be happier with higher impedances however.  The EL84 of the Decware Super Zen has a 8khz primary, which gives a very good turns ratio into 6 ohms.  Other amps, especially DHT amps, may prefer to see a higher impedance load.  The 2.5k primary of a 2A3 comes to mind.