'reference' speakers idea (ribbons & sealed bass bins)

[lucpes]

I'm trying to get the best sound for <$4k total so I'm cooking for a while a simple yet effective (I think) design, using:

- RD75 ribbon from B&G, one per 'channel' ( http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=264-700&DID=7 ) in an open baffle, separated from the woofer enclosure, used as a full range driver

- NHT1259 woofer ( http://www.madisound.com/nht1259.html ), two per channel, separate enclosure (300l+stuffing), powered by one amp per woofer unit ( http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=300-794&DID=7 ) - planning of getting rid of all the controls this one has...

- DAC/crossover (around 170Hz)/equalizing/alignement using Behringer's DCX2496 (of course with capacitors/opamps upgrade): http://www.zzounds.com/item--BEHDCX2496

- ribbons powered with whatever good 200W+ amplifier I can get my hands on (I have Slone's OPTIMOS 200W units, should do the trick)

more on ribbons/linesources: http://t-3.cc/users/audioworx/page102B&G-Gallery&Links.html

http://www.snippets.org/alsr/index.php3

Any thoughts, ideas/bashing (like 'you also need two small (8")midbass (80Hz to 170Hz) drivers on the baffles to integrate the subwoofers with the main ribbon pannels')?

 

[lucpes]

2x NHT1259 response in 300l sealed box. Add some stuffing and all will get better

 

[sreten]

IMO for open baffle mounting of the ribbons you should be looking
at adding an Eq'd cone array to the necessarily reasonably wide
baffle for the ribbon.

2 8" are nowhere near whats required for smooth progression
from line source to sealed omnidirectional bass, I'd suggest 6
of these (with serious Eq) per side (6 for 5.3 ohm loading) :

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=299-431

and c/o frequencies ~ 75Hz and ~ 300Hz.

I can't see the ribbon handling 150Hz open baffle.

sreten.

 

[454Casull]

You can put together an Orion system for less than $4000 if you do all the crossover work yourself, I think.

 

[Pete Mazz]

I"ve been down this road. I tried several variations of bass box and ribbons. Never could get a coherent soundfield. Changed to a line of the Dayton aluminum 7" woofs, 6 per side, and the difference was astonishing. I still need to run my sub with them as the roll off starts ~50Hz, but that was my design goal all along. I don't EQ them. I would also cross the ribbons over at least 300Hz. I settled on 500 Hz 24dB LR and have been very pleased. You'll need a couple notch filters in the mix, as well. One ~5kHz for the ribbons and another ~300Hz for the dipole woofs.

Pete

 

[lucpes]

Ok, glad to see it's been done Noted the added midwoofer array - open baffled too I guess

Pete, I also have some concern regarding the ribbon's ability to go to 20kHz (I just had my hearing tested and I still can hear up to 19kHz). My guess is that it'll do it, with the right amount of eq. The Behringer unit should be able take care of the eq/notch and so on.

 

[Pete Mazz]

Yes they're dipoles. RD50's and Dayton 7" aluminum woofs.

An externally hosted image should be here but it was not working when we last tested it.

Here's a 2 meter freq resp. The very high end is definitely rolled off. I'm not sure if EQing will improve it much. To my old ears they are fine. I modified B&G's suggested notch filter to increase the cut ~5 kHz which rolled off the top end even more. I have parts to re-do it, but honestly have been too lazy (and pleased) with what I'm hearing.

An externally hosted image should be here but it was not working when we last tested it.

Note that the SPL axis is in 3 dB increments.


Pete

 

[Gregm]

Originally posted by Pete Mazz
Here's a 2 meter freq resp

Wow! That a beauty.
No lobing from the array at listening position? What's the trick ?

 

[lucpes]

Pete, some questions and this becomes my must-do-as-soon-as-possible-major-long-term project

- you have chosen the RD50 instead of the RD75 - I can't see any differences besides the height (spk length) (I have 10ft ceilings, I can afford 6ft+ speakers ) Listening distance would be around 6ft-9ft so RD50 is better for me?

- as these would be a pretty steep plunge for my (also young wallet - Does this type of speaker justify the effort? How does it fare compared to commercial offerings in the 10K range?

Many thanks for the details so far

 

[Pete Mazz]

My room has <8' ceiling ht so the 50s are fine. They still stand just over 6' high, as the bottom of the 50s start ~2' off the floor. Basically tho, sitting or standing the sound is uniform. My listening distance is 12'. With taller ceilings I may have gone with 75s and a longer line of woofs. B&G recommends a longer listening distance for the 75s than what you have tho.

Going to dipoles made a significant change in my room. Sidewall distances are not uniform and the dipoles helped the overall balance. Ceiling and floor reflections were also improved as the ribbons have less vertical radiation beyond the actual ht of the unit.

What the ribbons do, they do very well. Best midrange I've heard. They don't get extremely loud w/o distortion. The sensitivity is on the low side for some (88dB IIRC). Really tho, going to a dipole made the most difference. I actually had them in an enclosure at one point and it sucked the life out of them.

Greg, I had a freq resp from the list position but since my move to XP, I can't seem to find it. No strange anomolies as I remember tho. I generally only design and measure for sweet spot performance. Since I don't do any serious listening off axis, I really don't care how a speaker performs there.

Pete

 

[TNT]

Run the Behringer's DCX2496 in the digital doian instead if possible - it's (almost) transparent.

/

 

[Timn8ter]

Coincidently enough, Tom Perazella built a pair of dipole RD75s and added a dipole mid-bass of 6 Peerless 831727 10" woofs per side. He stated that this amount of displacement was necessary to match that of the RD75s. His low bass is handled by an IB sub.

 

[lucpes]

The mid-woofer array in addition to the ribbon for subwoofer transition makes perfect sense. Taking ito account that the RD75/RD50 have a nasty resonance at 140Hz (yes, it'll do that with the right amount of eq and at lower spls) one would want to get higher crossover frequencies (250Hz+ depending on taste/midwoof response & so on).

As per mr. Linkwitz:
---------------------------------------------------------------------------------
At 100 Hz a difference in acoustic path length of 1/8th wavelength, causing 45 degrees of phase shift, corresponds to 43 cm (17 inch). At 150 Hz crossover this decreases to 29 cm (11 inch) and makes the placement of a separate woofer relative to the midrange that much more critical. I like to keep offsets to less than 1/16th of a wavelength which makes it pretty much mandatory at 150 Hz crossover frequency to integrate the woofer with the midrange cabinet. This is not optimal for the woofer/room interaction which is minimized when the woofer is placed near the side walls.
--------------------------------------------------------------------------------

I'd choose the PEERLESS 850490 HDS 8" WOOFER http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=297-646, which should give low distortion figures (extrapolating from its smaller sibling Peerless 850439
tested here: http://www.linkwitzlab.com/x-mid_dist.htm )

However, the Dayton 7" Aluminum ( might fit the bill better (price/quality ratio) ), albeit with higher distortion figures:

http://mfk-projects.com/7_in_test.htm

Thanks for the suggestions so far!

 

[lucpes]

Run the Behringer's DCX2496 in the digital doian instead if possible - it's (almost) transparent.

/

That was exactly my intention, however a good passive 6ch attenuator would be needed as I don't want to do volume control in the digital domain, although sensitivity matching/tailoring would be taken care of in the Behringer unit.

The Behringer might not be the best solution, but it will save lots of soldering time , I may go with a custom analog active crossover after everything's in place.

 

[lucpes]

Coincidently enough, Tom Perazella built a pair of dipole RD75s and added a dipole mid-bass of 6 Peerless 831727 10" woofs per side. He stated that this amount of displacement was necessary to match that of the RD75s. His low bass is handled by an IB sub.

Here it is: http://www.snippets.org/alsr/csd07.html

 

[Timn8ter]

What I don't understand is why the ribbon and mid-bass would be two separate units. Why not integrate them like this?
http://www.glacieraudio.com/Manufac/gilmore-a.html

 

[planet10]

Why not integrate them like this?

Gilmore bringing the woBritish hifi advertising to America... personally i like my mamallian protruberances integrated like that, but of a more modest size...

And i do hope he does well with the speakers, the whole thing is like a bold move from left field. Simple, elegant (the speakers, not the ads), and they probably work well. I wonder who's ribbon he is using?

dave

 

[lucpes]

What I don't understand is why the ribbon and mid-bass would be two separate units. Why not integrate them like this?

Nope, that's Tom Perazella's design. He built the midwoofer array after (I guess?) realizing that OB ribbons and big woofers don't mix too well.

(When I start building this - for now I'm gathering data) I intend to go with the midwoofer array + ribbon on the same baffle.

http://www.glacieraudio.com/Manufac/gilmore-a.html

Hehe The babe sure looks nice but the poor ribbon doesn't feel too comfy with large woofers dangling like crazy on the same (too BIG!) baffle.

 

[Timn8ter]

I always like posting that link
The rep at T.H.E. Show only said that the ribbon and woofers were proprietary but I didn't think to ask who the manufacturer is. They were the best I heard there though I admit I didn't hear the VonSchweikert VR11. I lose interest after a certain price point.

the poor ribbon doesn't feel too comfy with large woofers dangling like crazy on the same (too BIG!) baffle.

Cone envy aside, the sound was spectacular!

 

[lucpes]

Okay, this might be an easier & cheaper alternative. What kind of woofer would one need for open baffle and ...let's say -3dB@26Hz?

I know... -3dB@26Hz where? Not in room of course - theoretical

edit: http://members.ozemail.com.au/~googong/dipole.html