Aerius Bass Driver - What is it?

Hello all, Newbie from Uk here.

I have been a little unimpressed with the bass on my Aerius (not i version) and stripped them down over the weekend to see if/where any upgrades can be made. The bass unit looks to be a budget unit with thin pressed steel basket and the cabinet has little bracing and no internal damping aplied to cabinet walls. The ESL panels have just been replaced and they are truely singing up top but the bass is all woofly!

The speakers already have been improved substantially by a full upgraded cross-over so I am looking at the following tweaks.
1) replacement bass driver of higher quality
2) machined 10mm thick steel baseplates with damping to stop them ringing. (I have a wooden suspended floor in the listening room)
3) internal damping/lining of bass cabinet to add stiffness and deaden the resonant cabinet panels
4) possible rebuild of entire cabinets from better materials. Double skinned bass cabinet or maybe even slate!

I should say before you all start with "that will require X-over to be rebuilt/designed & the box modelling with the new driver parameters" that I am aware of all this.

What I really would like to know is...

Does anyone know what the standard bass driver is? Manufacturer or model? Or is this a Martin Logan manufactured unit?

Any help appreciated

Try contacting Martin Logan, get a hold of Jim Power if you can. I think M/L makes their own bass drivers.

I had to replace one of my woofers in 1994 (purchased new in 1992). I recently cut the old driver apart after being in a box for 16 years. I thought it was built like a tank compared to any other dead driver I've examined.

Be sure to use spikes with these speakers or the bass will be flat and muddy.

I would not over dampen/deaden the cabinets as it may lead to unexpected results.

I think that on a sprung wood floor the bass energy not only resonates the cabinet but energizes the floor system and gets fed back into the cabinet a second time. I built my own sandboxes to solve this problem, see my system link below.

What amp are you using and what does the rest of your system look like?

Hi Dice,

I had the "original" Aerius for several years. Although it's been a number of years, I don't recall the bass unit being amusical.

In fact, it was quite the opposite and blended quite well with the panel. Better than the SL3's that I replaced it with.

George has some good ideas you may want to consider.

Good luck.

GG

I had no bass at all in my listening room until I installed bass traps. What a difference.

Hi,
Thanks for your comments.
The rest of the system is..
Power amps - Krell KSA50 or LFD PA2 or World Audio Designs WD88VA (mainly the krell)
Pre-amps - Kinshaw Perception or Musical fidelity F22
DAC - Kinshaw perception
CD - Sony CDP555es (1986 vintage)
Turntable - Garrard 401/RB300/Ortofon MC15 super/Michell Iso

My first stage upgrade has been to get some steel base plates made up. These are being made from 10mm thick steel and 60mm wider and longer than the speaker base, drilled to accept spikes and to bolt to the threaded inserts in the base of the speaker. These should provide mass to stabilise (circa 10KG per base plate), provide more adjustment of vertical tilt angle (so I can angle them forward a bit over std) and will be lined with a bituminous type damping sheet to deaden them. The steel plates should be here over the weekend.

My second stage intended mod is to trial fit some 10KG/M2 foam/lead/foam (nominally 50mm thick) acoustic absorption internally in the bass chamber. I am also going to try this over the outside of the cabinet first.

I was then hoping to trial a few different type materials (all that can be removed if they don't work out) such as bituminous damping sheets to the inside of the cabinet and additional bracing. I would like to try a form of squeezefilm damping by making a box within a box sandwiching a nonsetting viscous liquid or sand. This would have to be a whole new box.

At that point it makes sense to trial better bass/mid drivers and possible seperate out the cross-over and locate near the amplifier.

The cross-overs have already been upgraded substantially.

Ideally I would like the ESL panels to go lower than the std 500Hz but that will cause a whole world of pain trying to reverse engineer teh speakers to see if it is possible.

If my room were big enough I would just buy Quad ESL57s or ML CLS but it isn't going to happen soon.

I have built quite a few speakers in my time so may end up starting with a fresh bass cabinet & driver. I also have the advantage that I work as an acoustic consultant/noise & vibration control consultant so have a load of test equipment and sample materials.

My main gripe with the Aerius bass is that is sounds slow and woolley in comparison to the panels. I was hoping to use a magnesium type bass driver with lighter cone mass to improve things. The standard unit looks like doped paper with a reasonable magnet but a thin pressed steel basket. IMHO having looked inside the martin logans they use low-ish quality components but manage to sound bloody good considering. I am looking for more of the same but better if that makes sense

diceman said:

...

FirstIdeally I would like the ESL panels to go lower than the std 500Hz but that will cause a whole world of pain trying to reverse engineer teh speakers to see if it is possible.

If my room were big enough I would just buy Quad ESL57s or ML CLS but it isn't going to happen soon.

I have built quite a few speakers in my time so may end up starting with a fresh bass cabinet & driver. I also have the advantage that I work as an acoustic consultant/noise & vibration control consultant so have a load of test equipment and sample materials.

My main gripe with the Aerius bass is that is sounds slow and woolley in comparison to the panels. I was hoping to use a magnesium type bass driver with lighter cone mass to improve things. The standard unit looks like doped paper with a reasonable magnet but a thin pressed steel basket. IMHO having looked inside the martin logans they use low-ish quality components but manage to sound bloody good considering. I am looking for more of the same but better if that makes sense

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Sounds like a great project. Please keep us appraised of your progress.

I would suggest that given your access to tools and what seems appropriate expertise, that you seriously consider using a speaker processor on your speakers. This will have a much larger impact than most of the other items you outline and it opens the options on replacement drivers.

Secondly, lowering the ESL crossover on that model would not be recommended. Matter of fact, most of the time, I find benefits in raising the crossover point, such that even on very large panels, like my Monoliths, I actually run them at 315Hz (vs 120Hz for factory default).

If your room is small, then keeping the 500Hz crossover is fine, especially if used with a steeper fourth-order crossover in a speaker processor.

The woofer update should probably focus on the 80 to 500hz range performance, as that's what will impart the most tonal character to the speaker overall. this means low mass cone, and good mid-bass to mid-range performance in the type of enclosure.
There are quite a few European models that might be good candidates. What models have you considered (both in terms of availability and price)?

Bass performance should be deferred to a sub (which a speaker processor makes a cinch to integrate, even with your 2ch preamps), as the Aerius (or any ESL) placement is never going to be conducive to good bass in a room.

Thanks for your interesting comments.
I still have a Behringer DCX2496 that I used on a pair of active speakers I built some back. With the collection of power amps I have, I have considered going active (I do have 2 off the KT88 valve power amps). I also have kicking about a REL storm 3 sub, 4 off Volt B250.8 bass drivers with active sub bass modules from previous projects. These I found were not great at upper bass/lower mid frequencies when trying to match them to Dynaudio D76AF mids and D260 Esotec tweeters.

My room is only 15 ft x 12ft and we are attached to the neighbours so deep rumbling bass is out of the question until we move house.

I have been looking at bass drivers (only briefly and as a prelim guide).
Volt B250.8 - IMHO these will be pushed to get up smoothly to 500Hz and will provide too much bass in my room. They are also 10" so will require seperate cabinets. I already have some 70 litre ported enclosures for them and Intend to use them as subs when/if I move house.

ATC 234mm - closer but IMHO they are still too big and will require cabinet work to make fit.

Scanspeak 22W - nice drivers but require some buggeration to fit.

Seas excel W22 - as above but magnesium which I fancy.

I have however started looking at smaller drivers - which may sound odd to most of you especially considering your lounge is typically much larger in USA. This I hope will integrate better with the ESL panels and be faster sounding (possible with loosing a little low end rumble/woofly wobble).

As such I am considering using magnesium/carbon/kevlar cones from either scanspeak or seas between 150mm and 180mm (6-7"). An oversized infinite baffle cabinet should also provide a smooth but early roll off. This can be added to later in a larger room with the Volt based subs which will be fine up to 80-100Hz (and will be a pair of subs).

To give you some insight in to my thoughts. I dont want bass unless it is fast, tight & accurate. I have a few pairs of speakers, some of which are too small, some too big and either dont provide enough bass or too much for the room to cope with.

ProAc Minitower - 2 off 4" seas bass/mids in D'Appolito config - not enough to fill room when away from walls.
JM LAB PS5.1 - 2 off 5K413 Focal bass/mids in D'Appolito config - about right for the room IMHO.
Celestion Ditton 25 - 1 off 12" bass & ABR - quite well damped bass but too much low end which farts & wobbles the floor boards - overwhelms the room.
DIY 3 way active speakers - 2 off Volt B250.8 in 70 litre ported enclosure - well damped but really overwhelms the room with bass.

I may well try a little active EQ before I set sail and spend some money. I would like to play with my DIY 3 way speakers and swap the Volt bass driver for something 4-8" anyway to fill in the upper bass/low mid and use the Volts in dedicated sub cabinets.

My ideal solution would be a vertical line array of 4" drivers to the side of the ESL panels with a Volt based sub at the bottom. This would also stop the instruments moving up and down in the soundstage as they swap between esl panel and current woofer.

Sorry I have rambled - I am still very early on in the thoughts/concept stage and hence really just trying to thrash out a cunning plan of attack!

You may want to verify that you indeed have the original M/L bass drivers installed and not something aftermarket. My driver has inked stamped numbers "2531" and "71923" on the magnet side. Gutted out the assembly weighs 3.5lbs, convert that to metric if you need to.

Photos:
http://s184.photobucket.com/albums/x295/kach22i/Stereo/

diceman said:

My ideal solution would be a vertical line array of 4" drivers to the side of the ESL panels with a Volt based sub at the bottom. This would also stop the instruments moving up and down in the soundstage as they swap between esl panel and current woofer.

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And stop any tendency to sound thin. Hope Rich isn't reading this:devil:

For MLOC members - diceman's up/down point has been quite an issue with MLs on a UK forum.

With all the effort / money you are expending to make a $800 +/- (US) speaker sound better, why don't you just buy another ML product with better panel / bass integration?

GG

Gordon Gray said:

With all the effort / money you are expending to make a $800 +/- (US) speaker sound better, why don't you just buy another ML product with better panel / bass integration?

GG

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I think he likes the challenge.

With the high crossover of the original Aerius it is the less airy of the upper end hybrid stats, and I think the better balanced for it.

Taking cover now.

George,

As I previously stated, I have fond memories of this speaker. No issues with the bass driver and integration with the stat panel.

My only issue was its inability, because of its size, to play demanding / dynamic material. Within its comfort range, they were quite musical.

GG

kach22i said:

I think he likes the challenge.
Taking cover now.

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i love your perspective. its almost scientific in its experimental attempts...or maybe your just a instigator...i really dont know.

Jimna said:

i love your perspective. its almost scientific in its experimental attempts...or maybe your just a instigator...i really dont know.

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I mean it in good fun, I sort of know where you are coming at. For the last seven years I've been cutting up and rebuilding my hovercraft. The experimental skirt is always close to working, but never as good as the factory setup. Somehow it is more fun to learn and tinker than to skim over flat surfaces without incident.

Link to project:
http://www.boatdesign.net/forums/boat-design/hovercraft-experimental-skirt-project-11973.html

From my perspective all the Aerius really needs is something under it including spikes, good room acoustic treatments, Nordost wires/interconnects and a big tube amp to drive it.

However, if you want to experiment and improve a speaker the Aerius could be a good starting point. I've added super tweeters and a subwoofer so I know there is room for improvement. I am just not that adventurous with something not already broken. If it were broken as Jimna describes then I understand his desire to go beyond a minimal restoration.

FYI; of interest might be this center speaker DIY design by JonFo:
http://www.martinloganowners.com/forum/showthread.php?t=2018

Can you take photos of the front and rear of the current woofer, so we might be abe to tell what it is? What is the outer diameter?

And can you expand on "The cross-overs have already been upgraded substantially."

greenipsum said:

I have replaced the woofer and modify the bass cabinet

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Could you show more of the room layout?

I'm confused about what your overall look of the speaker is now like.

Looks like you had fun tinkering with it.