DIY Amphion Bases Prject

[bigjacko]

Why is the four layer voicecoil l24roy only intended to use in free air. Is it because the Qts is tuned very high？ I wonder what will be the effect if we eq both drivers to the same frequency response, will there be any difference？

For the 10 inch sub there is another good one, wavecor sw275-01. https://audioxpress.com/article/test-bench-the-wavecor-sw275bd01-home-audio-subwoofer

Or if you want servo, rythmik servo sub with acompany plate anp.

 

[MAB]

Why is the four layer voicecoil l24roy only intended to use in free air. Is it because the Qts is tuned very high？ I wonder what will be the effect if we eq both drivers to the same frequency response, will there be any difference？

For the 10 inch sub there is another good one, wavecor sw275-01. https://audioxpress.com/article/test-bench-the-wavecor-sw275bd01-home-audio-subwoofer

Or if you want servo, rythmik servo sub with acompany plate anp.

It's not 'only' intended for use in free air. It was allegedly developed for Linkwitz' open baffle designs, but it is useful for a range of applications!
The L26RO4Y is actually low Qts, the two drivers are different in a number of areas:

http://www.seas.no/images/stories/design/pdf_datasheet/L26RO4Y-XM004-04_Datasheet.pdf

http://www.seas.no/images/stories/design/pdf_datasheet/L26RO4Y-D0004.pdf

Both are awesome. But, like you say there are lots of really great options.

 

[jhaider]

Thanks everybody for your knowledge !

So, lot to think about, I think the seas x2 drivers per box will go beyond my budget. I could do two SB per box.

it would be different from the amphion design which I heard and love (they do a stereo central base with two Seas, though)

The price of the amp will be a determining factor, what’s the consensus about power for this bases?

As much as you can get. FWIW, in one system we use a pair of "boundary subs," each with the 8 Ohm SB shallow 10s in about 6.5L cabinets (yes, that small), and power them with about 400W/8 Ohms (Crown XLS2502). There are other subs in the system, but the point is a small closed box needs some power.

 

[Pablo1980]

Great, so, Hypex 500w ncore o the Icepower 700as2 would be a good match...?

regarding size, 1020mm x 191mm x 355mm (40”x 7.5”x 14”) would be considered small?

 

[jhaider]

That's a large enclosure for those woofers. Are you sure you want your stands to be 40" tall?

 

[Pablo1980]

I am kind of replicating the amphion bases that were designed to work with my monitors (amphion one15) so I started from those measures.

- The baseone25 had 1 Seas driver and 1 radiator on one side
- The basetwo25 has 1 SB shallow and 1 SB radiator on each side

I work with the monitors at that height, slightly tilted down.

 

[MAB]

So I don't get things confused, the woofer is the SW26DBAC76, right?
If so, about 15 liters per driver.
40" does seem tall for listenning and does have a much larger volume, even after taking amplifier cutout and driver volume into account... Even a shorter sub is going to have internal volume larger than the ~30 liters two of those subs would like. But, no problem! Easy to reduce volume! I would consider the height carefully though.
I love your idea. And you should have no problem making a really capable sub out of those woofers in what you are attempting.

 

[Pablo1980]

Thanks! please remember that these subs are not for listening but music mixing a production, they are placed behind my work desk, also they are not meant for traditional subwoofer duties, but extending the smaller monitor speakers (also liberating the small 5" woofer)

These are the current model:

BaseTwo25 Bass Extension System | Amphion

BaseTwo25 is a state-of-the-art bass extension system elevating a two-way studio monitors into a full range, cohesive three-way system.

amphion.fi

How do you think it would work with two oposing drivers and no passive radiators? or should I go all in and use two drivers and two PR like amphion does?

 

[Zek]

PR is used instead of bass reflex and it is not easy to determine the true volume of the cabinet without measurements.
For DIY, it's easier to go for a classic bass reflex and suitable drivers for that purpose.

 

[MAB]

I think either sealed or passive radiator will be fantastic. And, same for if you built it with the SB Acoustics or the Seas L26's (for instance). Both passive and sealed have tradeoffs, but after you EQ the sealed to make up for the lack of extension, I think it ends up a tie. Four of any of those subs sealed with EQ in small boxes is just going to be awesome and you won't have to deal with passive radiator box alignments.

One other thing, to really do the passive radiator right, you actually want about double the passive to active cone area. This is because of the huge excursion of the radiator at resonance, force-cancelling and cabinet stability become an issue. Even more so since you typically need to add additional mass to multi-passive alignments. It occurs to me that four radiators and two actives on those 40" tall boxes you plan on making would look so dope. And would sound great with tons of extension. But you would have to mill out additional holes. Do lots of calculations that a passive radiator system requires, make extra weights, etc. It's all totally doable, I really question how much it gains over EQ'ing a sealed alignment. I have four subs each with 1 single Seas L26 and two SL26 passives per box. I spent tons of extra time over what it would take for the same build all sealed.

I am pretty sure you are going to be happy with four of those woofers built like you are thinking. You will want to make sure you get the internal volume correct for the woofer you choose.

 

[Pablo1980]

Thanks Mab, I don´t know how amphion does it, the boxes are passive, they have a separate amp that (I believe) holds two class D amps and the switchable crossover.

how do you think they achieve great performance with two drivers and two radiators per box (one of each on the previous version).

 

[MAB]

They seem to use force cancelling, which I think is important especially in a tall passive radiator sub. If I understand the design, the two passives in each box are opposed, and so are the two actives, so should be really resistant to rocking and crawling. I just can't find a picture of the innards or a drawing to say exactly what each driver is... As far as drivers in the slender cabinets, the two SB shallow woofers would work since they are ~70mm deep, and passives are shallow too.

Only having 1 radiator per woofer will limit the system a few dB of clean output because of you will run into maximum excursion of the radiator at resonance earlier than xmax of the woofer (assuming matched PR and woofer) 2 radiators per woofer fixes that limitation. But, for your application the 1x radiator per woofer you would still have a ton of clean extended bass. For home theater or party-mode or you just like higher volume, 2x radiators becomes important. Once the passive radiator starts fluttering, it does sound super-bad.

And, you can do everything and more than they have packaged in their commercial sub with either a DSP plate amp or an external DSP/Crossover and an amp plus a mic and software like REW.

 

[Pablo1980]

Thanks, I think I will go with one driver and one radiator, and probably can add the other next year. I will be working at 1,5mts from them so it could be overkill.

DSP is in the plans, too bad hypex fusionamps cannot connect to a powered speaker just to filter or delay them avoiding the amplification.

 

[sarumbear]

Just a few notes:
1. You're using woofers designed for open-baffle operation in Linkwitz's LX521 speakers. They aren't designed to be used in a tiny closed box... Although they are very good drivers and simulate nicely, I still wouldn't use them in a box like what you attached.

What parameter makes those drivers designed for open baffle and not suitable in a closed box? What is it missed in the simulation?

 

[MAB]

What parameter makes those drivers designed for open baffle and not suitable in a closed box? What is it missed in the simulation?

Good point.
Nothing prevents from using the L26RO4Y in a variety of box alignments. Maybe sealed is not naturally optimal, but you can do lots of great things with sealed plus EQ.

Here is the info from the Madisound website, which is apparently quoting Seas, with an odd quote from SL in the middle:
"The L26RO4Y subwoofer. Developed in cooperation with Linkwitz Laboratories in Corte Medera, California, the L26RO4Y saw its first application in the highly acclaimed Linkwitz ORION open baffle loudspeaker, and is currently used in the Linkwitz LX521. The L26RO4Y substantially improved the ORION's bass performance and dynamic capabilities, and has since been incorporated in all Linkwitz lab designs. We at SEAS are also very proud that the ORION, LX521, LXstudio and LXmini+2 loudspeakers use all SEAS drive units!

"There is more to a woofer than its published TS small signal parameters and X-max, derived from mechanical measurements. In an open baffle, a woofer operates in the large signal domain; and its distortion, dynamic stability and limiting behavior determine the sound. An open baffle is the most demanding and difficult environment for a long throw woofer." -- Siegfried Linkwitz

To meet these stringent demands, the L26RO4Y subwoofer builds upon the already excellent chassis, magnet system, cone, and surround of our L26ROY. An all new FEA designed spider and 4 layer voice coil wound on a stiff glass fibre former have been employed, resulting in a driver with ultra long throw, very low distortion, and extremely stable mechanical operation under all conditions; including open baffle systems. The low Qts and Fs are ideally suited for active open baffle bass systems, but the L26RO4Y can also produce excellent results in enclosure based subwoofer and multi-way systems."

More importantly, here are the datasheets with the TS parameters (despite what SL said!!!):

http://www.seas.no/images/stories/extreme/pdf_datasheet/L26ROY-XM001-04_Datasheet_v2.pdf

http://www.seas.no/images/stories/design/pdf_datasheet/L26RO4Y-XM004-04_Datasheet.pdf

Clearly, the L26RO4Y is going to work in a range of applications. I know little about open-baffle, it seems the key here is lower compliance and higher moving mass with the same resonance frequency as the L26ROY sibling, with slightly more linear excursion capability.

 

[sarumbear]

I know little about open-baffle, it seems the key here is lower compliance and higher moving mass with the same resonance frequency as the L26ROY sibling, with slightly more linear excursion capability.

"There is more to a woofer than its published TS small signal parameters and X-max, derived from mechanical measurements. In an open baffle, a woofer operates in the large signal domain; and its distortion, dynamic stability and limiting behavior determine the sound. An open baffle is the most demanding and difficult environment for a long throw woofer." -- Siegfried Linkwitz

The key according to the man himself was on the post, copied above. On an open baffle the driver will operate at the extremes of Xmax more than a enclosed speaker will, hence the need for a high linearity at extremes is important. In other words you need a higher linearity driver. This doesn't mean you can't use such a driver on an enclosed design. You are possibly over-killing and spending more than you should. Then again high linearity = low distortion, hence if you have the money go for it, I say.

 

[MAB]

The key according to the man himself was on the post, copied above. On an open baffle the driver will operate at the extremes of Xmax more than a enclosed speaker will, hence the need for a high linearity at extremes is important. In other words you need a higher linearity driver. This doesn't mean you can't use such a driver on an enclosed design. You are possibly over-killing and spending more than you should. Then again high linearity = low distortion, hence if you have the money go for it, I say.

Makes complete sense. Thanks.
I found SL's quote odd, since it seems that this is actually explicitly in the published TS parameters: 2mm of additional linear travel compared to the sibling driver, with a less compliant suspension. Perhaps it is the danger of quotes...

 

[sarumbear]

Makes complete sense. Thanks.
I found SL's quote odd, since it seems that this is actually explicitly in the published TS parameters: 2mm of additional linear travel compared to the sibling driver, with a less compliant suspension. Perhaps it is the danger of quotes...

It’s not odd really. TS parameters explains the low signal behaviour of a driver. At high current and high Xmax TS system no longer represents the driver well. You need to resort to actual values of the driver parts like cone weight, magnet power, etc.

 

[MAB]

It’s not odd really. TS parameters explains the low signal behaviour of a driver. At high current and high Xmax TS system no longer represents the driver well. You need to resort to actual values of the driver parts like cone weight, magnet power, etc.

Thanks, makes sense. I appreciate your explanation.

 

[Pablo1980]

hi everybody, I would like to thank all of you again for the help....will probably order the speakers soon

Regarding amps, do you think the Icepower 1200AS2 would be a good choice for this project or should I go for an hypex NC502MP or similar?
would I be losing sound quality with the 1200AS2?