AudioTechnology + RAAL Ribbon = "Sequence Three – Grand Reference"

[gornir]

Hi everyone,


I’ve started the "Sequence Three – Grand Reference" enclosure construction and I will continue to report about the building progress as it proceeds.

Sequence Three – Grand Reference Construction!
Sequence Three – Grand Reference Construction Update1!

The "Sequence Three – Grand Reference" enclosure is made of two parts, one which contains the tweeter and the cross-over and one which contains the mid-woofer and the woofer. The top tweeter enclosure can slide back and forth in order to be able to adjust the acoustical off-set between the tweeter and mid-woofer, if needed in the design.

The loudspeaker enclosure uses a baffle replacement system in order to be able to swap drivers in and out as needed and at the same time make the enclosure somewhat future proof.

The overall enclosure dimension is (WxHxD) 33x105x43cm incl. feets + baffle thickness. The tweeter and mid-woofer replacement baffle is 19mm thick, while the woofer baffle is 38mm thick.

The tweeter + cross-over enclosure is 33x20x43cm + the tweeter baffle. The mid-woofer and woofer enclosure are 33x78x43cm + the baffles. The two bass-reflex ports are mounted in the bottom of the enclosure. The enclosure feet’s are 7cm high including the “Sonic Design” damping feet’s.

All internal walls are covered with 4mm bitumen pads as well as bracings for the mid-woofer and woofer section.

The woofer net volume is about 64 liter minus the volume for the bracing, bitumen pads, bass-reflex ports and driver, which gives approximately 55-56 liter for the woofer to work in. The mid-woofer and tweeter sections are about 18 liter volume each.


Picture 1: Mid-woofer and woofer enclosure.

Picture 2: Woofer section.

Picture 3: Mid-woofer section.

Picture 4: Tweeter and cross-over enclosure.

Picture 5: Round-over jig.

Picture 6: Mid-woofer chamfering.

Picture 7: Woofer routing and flush-mount cutout.

Picture 8: Milled groove to be filled with elastic filler for invisible MDF board joints.

Regards

/Göran

[gornir]

A brief update:

The work is proceeding as planned even though it has been delayed a bit by bad weather. Unfortunately the Swedish summer weather is a bit unpredictable.

Lately the work has mostly been – sand, fill, sand, fill, sand, fill, sand……… I almost forgot how boring I think sanding is.

Currently I’m working on the loudspeaker foot as well as attaching additional bracing and damping of the woofer section. I’m also planning for the spray painting of the baffles and some parts of the enclosure. The final finishing of the loudspeaker isn’t 100% decided yet.

Sequence Three – Grand Reference Construction!
Sequence Three – Grand Reference Construction Update1!
Sequence Three – Grand Reference Construction Update2!

Picture1: Mid-woofer and Tweeter baffles.
Picture2: Woofer baffles.
Picture3-6: The left loudspeaker shows the tweeter/cross-over enclosure and the baffles, excluding the loudspeaker foot. The right loudspeaker shows the mid/woofer enclosure without baffles.

Regards

/Göran

[Jozua]

Hi

Looks very impressive

Why not use the bass unit in a TL as Troels has done?

Regards

Jozua

[gornir]

Originally Posted by Jozua

Hi

Looks very impressive

Why not use the bass unit in a TL as Troels has done?

Regards

Jozua

Thank you!

Why would I build my speaker exactly as Troels?

Seriously, in fact a TL solution had required a larger enclosure than I wanted in my design. The bass-reflex solution will work well with this woofers and I think even Troels have used this woofer in a BR design. According to my measurements/simulations on the AT woofer, the Troels used and suggested enclosure volume for it in a BR solution seems optimal for it.

Regards

/Göran

[5th element]

I'm looking forwards to see how this progresses, especially if you give us detailed driver measurements as you have in the past. There is a distinct lack of good measurements on the RAAL and AT drivers so it would be very useful if you did

[R-Carpenter]

Originally Posted by 5th element

I'm looking forwards to see how this progresses, especially if you give us detailed driver measurements as you have in the past. There is a distinct lack of good measurements on the RAAL and AT drivers so it would be very useful if you did

Measuring Raal 140-15D
I didn't find that 140-15D all that great. Aside from high second order harmonic, it's very directional vertically (as any tall ribbons) even with the foam pads. Smaller Raal are better performers, less directional all tho pricing is insane.
With the name like "Grand Reference" I suppose, frequency response should be within 2-3db and that's not going to be so easy to do with 140-15d.

[gornir]

Originally Posted by 5th element

I'm looking forwards to see how this progresses, especially if you give us detailed driver measurements as you have in the past. There is a distinct lack of good measurements on the RAAL and AT drivers so it would be very useful if you did

Yes, of course. There will be a lot of measurements and probably more than usual.

[gornir]

Originally Posted by R-Carpenter

Measuring Raal 140-15D
I didn't find that 140-15D all that great. Aside from high second order harmonic, it's very directional vertically (as any tall ribbons) even with the foam pads. Smaller Raal are better performers, less directional all tho pricing is insane.
With the name like "Grand Reference" I suppose, frequency response should be within 2-3db and that's not going to be so easy to do with 140-15d.

Hi R-Carpenter,

Thank you for sharing your experience with the RAALs. I’ve read some of your comments before regarding the RAALs, but I don’t judge them before I myself have measured and listen to them in a loudspeaker design. Measurements is one thing, how it actually sounds is another…

Yes, I agree the RAALs are very expensive, but in my case I bought them second-hand and replaced the ribbons with new ones.

I’m not too worried about some elevated second-order harmonics, many domes have the same behavior. The vertical dispersion is another thing and the effect of the foam pads will be very interesting to measure.

Naming a speaker to something meaningful is always hard, but in this case the “Grand” stands for a large floor-stander and “Reference” stands for the use of more exclusive drivers and custom built cabinets (not pre-fab Dayton cabs).

The loudspeaker will first be setup in an active configuration with my DEQX HDP-3 pre-amp and the frequency linearity in this setup will probably be better than +/- 0.25db, if I so wishes.

Regards

Göran

[PandazYa]

interesting build i'll follow this project!

which kind of amplifier are you gonna use with such high end drivers and dsp since you're going active?

[gornir]

Originally Posted by PandazYa

interesting build i'll follow this project!

which kind of amplifier are you gonna use with such high end drivers and dsp since you're going active?

Usually when I go active with the DEQX HDP-3 I’m using 3x PopPulse T-150 class-T power amps. Don’t be discouraged by the low price of these amps. When used as pure power-amps with the volume control by-passed they sound very good, much better than the price suggests. Yes, they are a bit power limited, about 50W @ 8Ohms and 90W @ 4Ohms, but they sound more powerful than they should for the price and they have the bass in a firm grip and they do sound very musical and pleasant.

Definitely one of the best Hifi equipment bargains I’ve done.

I also have more powerful multi-channel class-AB amps from Kinergetics Research as well as tube-amps and other pre-amps. I have a wide variety of pre-amps, power-amps and DACs etc. in order to test and listen to my loudspeakers in different setups.

Regards

/Göran