Ohm Acoustics Model i (Sub Bass Activator Install (w/ pictures))

[MetalDaze]

Part 1: A bit of history of these awesome speakers & how I came to own them.

Part 2: SBA Install with pictures

Part 1-
I was the lucky purchaser of these speakers off of a well known auction site. I've owned them now for around 18 months and have had them in use for about 3 months. I bought them from a very nice gentleman in North NJ. If memory serves me correct his name was Steve (by chance you're reading this, send me a message if you want to come hear these speakers again!)

He was downsizing, and I got them for a fair price being that they are 40 years old and several of the tweeters were blown at the time. None the less Steve was the original owner and bought them from Tech-HiFi ~1981. We were both very happy to learn about our shared passion for Ohm speakers. Me for finding an original pair from the first owner, and him for knowing his long time pair of speakers was going to someone who would provide them the attention they needed and deserved.

A back breaking trip into my car and then back out into my flat it was. But driven by excitement and some anxiety I hooked them up. Knowing a few of the tweeters were DOA, I swapped them for some non OEM replacements I had. Trying to back track and see if any problems in the crossovers also existed. I got them all working and began evaluating what upgrades I would score from Ohm once my report card was mentally filled out.

They produce a huge, room filling, floor shaking sound. So, of course, their upgrades would not come quietly. Only wanting to load them into my car once (which was too much already), worrying about both my back and the veneers. I opted to mail order my upgrades and install them myself. Unfortunately fitment issues plagued this first attempt as well as a broken connector from what I can only assume was rough handling during shipping. Covid already had things in lockdown so when Ohm said "Oh no! Send them back and we'll cover the shipping!" I thought to myself, what customer service

Cost providing (or prohibiting) what upgrades I could assume all at once, I decided instead to haul them in to the factory in Brooklyn to be evaluated by the man who incepted the design himself with Marty Gersten's teachings - John Strohbeen.

One high tweeter per cabinet was functioning perfectly, as were the crossovers. So John and Evan upgraded the mid-woofers and added SBA's, upgraded the low tweeters, and installed a set of new high tweeters which we placed on the fronts of the cabinets.

The subwoofers themselves are still original, hence the rotated "Ohm logo". I queried Evan on the phone to remind me how long I should leave the woofers inverted. He said since the voice coil was so heavy, over time gravity causes the spider to sag. A 1/4 of a turn every few months if the woofer was new would be recommended, but since this woofer is 40 years old. Its fairly safe to assume it will take a good number of years for the spider to sag equidistant, and in the opposite direction, once rotated.

Part 2-
Having them fully functioning in my treated listening room was revelatory. A completely different approach to the way the sound occupies the room. Knowing what other updated Ohm conventional speakers sound like in my room & system - as well as the Walsh style - this was still something totally different. The last missing piece aside from totally rebuilt subwoofers, were the SBA's.

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Removing a woofer with a 4.5lb magnet not counting the basket structure or cone, without scratching the 40 year old veneer was fun. I left them upright because I am too lazy to remove them from the iso pucks which I so anally set up. And fixed the distance and positioning of, to my listening position

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A picture of the label from subwoofer #1

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Subwoofer #1 with the SBA attached. I like the look of these, which has changed since I last bought them.

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Red to Red - Black to Black

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Again, Red to Red - Black to Black

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I have an extra i subwoofer in storage so I thought It'd be funny to use it as weight while the glue cures

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Extra sub label

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Extra sub label close

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Subwoofer weight

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Subwoofer #2 label

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Cabinet #2 Subwoofer/System switch was giving me distortion and drop outs, even after working the self cleaning tap over two dozen times. While I had the woofer out I pulled back the insulation. Cleaned and sprayed the contacts with contact cleaner, an then a little deoxit. After that I used a paper towel to soak any extra cleaner making its way out of the switch, while working it back and fourth. The end result is a switch which feels, sounds and functions like new. Feels = clean unabated movement. Sounds = a clean 'snap' as the switch locks into the desired position. Functions = distortion free bass and no more drop outs!

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The insulation positioned back before the final step of reinstalling the subwoofer.

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The last two pictures are part of my set up for driving these beasts. An RME ADI 2 DAC fs balanced connections into a Parasound P5 balanced out into a Parasound A21+.

I am still waiting on the subwoofer port adapters to arrive but I can say that the addition of the SBA's for the subwoofers made a noticeable difference, and improvement.

The speakers and their sound presentation as a whole, appears more interwoven and complete. Not that this was a performance issue prior. However now with the added electrical dampening and better control of the woofer cone, the bass which before was awesome! but lacked in some definition. Is for lack of a better way to put it, "lighter on its feet". The speaker was delicate when necessary, but a brute when pushed and you FEEL IT. That still remains, but when you push the power delivery to brute level, the subwoofers now have boots with tap dance plates on them.


Questions, comments concerns all welcome.

I'm just here for the beer

Cheers!

 

[tubed]

"the Ayes have it!"

 

[LinderK]

I bet those sound great!

 

[nolasally]

Your I’s look great. That said I’m not a fan of John and the shell of a company that ohm Acoustics now consists of. Nothing against the man per se. but he’s trying to run a business and sell upgrade products that imho are downgrade products like looking at the massive magnet structure of original midrange vs the upgraded driver. My I’s are all original other than rebuilt crossover. I have no interest in altering them whatsoever as they sound stellar to me. Also my ohm F’s will never see any upgrades from ohm acoustics.

 

[tubed]

Your I’s look great. That said I’m not a fan of John and the shell of a company that ohm Acoustics now consists of. Nothing against the man per se. but he’s trying to run a business and sell upgrade products that imho are downgrade products like looking at the massive magnet structure of original midrange vs the upgraded driver. My I’s are all original other than rebuilt crossover. I have no interest in altering them whatsoever as they sound stellar to me. Also my ohm F’s will never see any upgrades from ohm acoustics.

Mine sound great in their original form.
Did you notice an improvement when you recapped?
Also, I wish I we could talk the OP to look into the SBA box to see what's there

 

[nolasally]

@tubed Yes I recapped because HF sounded muted. Tested values and were quite off. Likely abundant amounts of smoke & mirrors in SBA box. Lol.

 

[tubed]

@tubed Yes I recapped because HF sounded muted. Tested values and were quite off. Likely abundant amounts of smoke & mirrors in SBA box. Lol.

Could be, lol.
One of these days I'll change out the electrolytics with some polys, though the speakers do sound so good as is.
I'd probably be wise to some day purchase a cap meter.

 

[MetalDaze]

Sorry I was trying to respond last night but the website went down.

I bet those sound great!

Indeed! To my ear they do!

Your I’s look great. That said I’m not a fan of John and the shell of a company that ohm Acoustics now consists of. Nothing against the man per se. but he’s trying to run a business and sell upgrade products that imho are downgrade products like looking at the massive magnet structure of original midrange vs the upgraded driver. My I’s are all original other than rebuilt crossover. I have no interest in altering them whatsoever as they sound stellar to me. Also my ohm F’s will never see any upgrades from ohm acoustics.

Thanks! No skin off my nose every one is entitled to their opinion. I've always had great interactions with both John and Evan. On the phone and in the factory. I have a tendency to talk a lot, and they were always happy to sit and chat with me, entertain questions about their technology, history and just the breeze.

John is getting older and despite what some may say about him or his 'business practices', he deserves respect. He has been the president of the company since the early 1980's? He's kept Ohm afloat through harsh economic times more than once and harbors a wealth of knowledge. Him, not unlike Tim De Paravicini who recently passed away. Are a hold over from another time in the past when Hi-Fi was still a new idea. And once their gone so does a lot of their knowledge & expertise. It's up to us and people like Evan to keep the history and music alive (through their speakers).

I understand your view of their updates to the speakers being anything but. However I respectfully disagree.

The first real pair of Ohm's I bought were my H's. I had C2's already, but they needed work. In the meantime I scored the pair of H's and was happy. To my delight, when I pulled the 8'' woofer just for fun, I found they already had SBA's installed. Fast forward a year or so and I bought another pair of H's with the intent to use one as a center channel. This pair was all original. No SBA, and a different, heavier passive radiator. When I tested it, it sounded okay. Pretty good actually. But it was missing something. Extra deep bass wasn't really there and where it was present, it was sort of fat, and slow. I used one to trade in, and the other I updated with a new 8'' driver and SBA. I also sourced another passive radiator with the accordion surround to match the others for L and R. These changes made that H sing just like the other 2. Deep, clean low bass. Wonderful lifelike mids and open highs.

The upgrades do not completely change the sound of the speaker. They enhance the already awesome sound they produce. In my experience when you bring them something to be updated. You have 2 choices depending on availability. You may choose to have a poly cone woofer installed on which ever speaker you are updating. Or you can have your original driver rebuilt. With or without poly cone I am not sure. I've bought one poly pair of woofers for my Dad. All the rest I have had rebuilt by them in Brooklyn. They use the original magnets and baskets and replace the cones, surrounds and dust caps. As well as adding ferro fluid around the voice coil for enhanced cooling and compliance with more modern standards.

I have not seen any change in the magnets. But again if a driver is totally failed or overdriven and degaussed. Then a new magnet would have to be used. The original magnets were gigantic because of the material they are made from. Newer compound magnets (neodymium for example) has a much greater magnetic strength per unit area than the older FeO2 style. So a smaller sized one may be used to achieve the same strength of magnetic field.

I also can't see your F's getting any service from the factory, because they don't service them anymore!
They will update the driver to the latest and greatest. But yeah, only 2 or 3 people I am aware of in the USA that actually still service those original F drivers. That is one instance where I believe business and profit took the front seat. But that's the way it goes. (Just guessing but - Could it be you're the gentleman with those G's for sale? A rare unicorn those are regardless! And no I can't afford them )

@tubed the older SBA's were open on 3 sides so you could see inside them. These newer ones I got for the i's were closed up as you saw. However I like the cleaner look of the newer ones. Not as much smoke and mirrors, just an inductor, some resistors and I believe a capacitor. To roll the bass off ( or low pass) instead of how they were just 'open' all the way to sub bass frequency. They also increase the output a bit and lower distortion in the regions where the driver is most linear.
They usually spray the guts of the activator with some adhesive and what looks like speaker dope. So it's hard to get a clear look at any values on the parts. But I can pull one and try to get a good picture.

 

[Diamond Blue]

Metaldaze did you happen to get the original manual for the I's? I have a set and have been trying to find a manual. The speakers sound fantastic. I had a low tweeter go out and got a new set from John. He is great to deal with.

 

[ouimetnick]

Your I’s look great. That said I’m not a fan of John and the shell of a company that ohm Acoustics now consists of. Nothing against the man per se. but he’s trying to run a business and sell upgrade products that imho are downgrade products like looking at the massive magnet structure of original midrange vs the upgraded driver. My I’s are all original other than rebuilt crossover. I have no interest in altering them whatsoever as they sound stellar to me. Also my ohm F’s will never see any upgrades from ohm acoustics.

In Ohm/John's defense, the original tweeter used a big ferrite magnet and the newer Wavecor unit uses a neodymium magnet. Neodymium is more expensive but can provide similar performance at lighter weight. It would be nice if they actually rebuild the old heavy Ohm made ferrite magnet version rather than substituting it with a Wavecor driver.

 

[MetalDaze]

Metaldaze did you happen to get the original manual for the I's? I have a set and have been trying to find a manual. The speakers sound fantastic. I had a low tweeter go out and got a new set from John. He is great to deal with.

The speakers did not come with any documents. I was able to buy sales booklets from auction sites. I uploaded a few pictures from one of the catalogues I have. The second is a later edition from 1979? And has quite a bit of info about the 'ayes' in it.

I will upload the scans of that catalogue soon when I have the chance.

 

[MetalDaze]

The sun has been shining nicely so instead of digging out my scanner I just took photos instead. I did the best I could realizing the upload sizing limit of 800x800.

There was a lot of really good information in the booklet about vented speaker design, and the wave transmission line transducer AKA "Ohm A" & "Ohm F".

Hopefully archiving it here will help keep the information in circulation, and can be a reference. I uploaded the full booklet which held up well over the years. And photographed nicely with still great color.

https://audiokarma.org/forums/index.php?media/albums/ohms-law-9.1716/

@Diamond Blue here are parts of the catalogue which pertain to the "aye" and may be of interest to you:

That's all I've got for now. Hope yourself & others find it helpful.

Cheers.

 

[ouimetnick]

Thanks for the upload. Find it funny that they said the Ohm I is small enough to fit comfortably in your home... It was the largest speaker I every owned. I was doing some reading up on Marty Gersten, and this caught my eye

1971 – 1978
Company founder and President. Under his direction, Ohm grew from a hole-in-the-wall to a worldwide hi-fi equipment business employing over a hundred people and grossing over $7,000,000 per year.

Ohm today has almost nothing in common with the Ohm that Gersten founded except the name, logo, and well I guess they still make speakers What a shell of a company. I think if John wasn't so arrogant and explored other speaker designs besides his "Walsh" design, they could have a better lineup. It would be cool if they still made C2, H, I, etc.

 

[MetalDaze]

Thanks for the upload. Find it funny that they said the Ohm I is small enough to fit comfortably in your home... It was the largest speaker I every owned. I was doing some reading up on Marty Gersten, and this caught my eye



Ohm today has almost nothing in common with the Ohm that Gersten founded except the name, logo, and well I guess they still make speakers What a shell of a company. I think if John wasn't so arrogant and explored other speaker designs besides his "Walsh" design, they could have a better lineup. It would be cool if they still made C2, H, I, etc.

Being that the 'i' was marketed to replace the 'F' (and an attempt at taking on a semi-omnidirectional dispersion pattern using conventional drivers) - that statement does ring with some truth in context. Considering the size of the 'F' cabinet, which is a fair big larger than the 'i' - not including the large "Wave Transmission Line" transducer. The 'F's' also had very demanding placement in a given room for their best sound.

A difficulty which was overcome to a large degree with the 'i', and an almost non issue into present day once the "Walsh 1, 2, 3" etc. came into existence.

However, speaker/listener placement is paramount. And will always be bound by the laws of physics.

Now that's out of the way, the "I's" are the largest speaker I currently own as well. Lol.

Though with their clean 'concert level' output, by design they sort of have to be.

I think it'd be sweet if they brought back making speakers like the L's, C2's, C3's, H's and the I's. They still create the mid-woofers and subwoofer drivers in house. So they kept the knowledge and enhanced it a bit.

All this conjecture is nice. But thinking realistically - If Ohm went the way some of us would appreciate. Who's to say the prices wouldn't be that of the JBL Legacy Line. Where they have been revisiting classic designs like the L100, 4312 and the L82. All great speakers. But charging up to $4,000 a pair for them. Which I find laughable.

Especially when my 40+ year old (albeit updated) Ohm's can do all the same, but with deeper bass and a more coherent midrange. For a fraction of the asking price of the revisited heritage line from JBL.

It pains me to say it, as I would like to see New Old Style speakers from Brooklyn. I don't think it will ever happen. And by some chance it does, I'm almost positive the MSRP would be something else for us to scoff about.

 

[MetalDaze]

Also just as an addendum to my previous post. The "I" was John's first brain child as it were. Incepted by himself and Marty. It was poised and marketed to be a replacement for the F's which kept blowing out their drivers from abuse. Or customers who just loved the sound and wanted more even when the speaker had no more to give.

According to Evan:

The F's had too little (none) serviceable parts.

The I's had too many (serviceable/breakable). One of which, namely, is the 24 element crossover.
I was at the factory at one point talking with John about this. And he showed me a customer's crossover from an 'I'. Or what was left of one. I have no idea how, but said customer had exploded. And I mean blew the ends completely off, almost every single capacitor in the network.

So they never quite got to the sweet spot with their big speakers beyond the bookshelves, before moving completely to the Walsh design.

 

[Diamond Blue]

Metaldaze Thank you. I found the original owners manual from my Ohm N & M's. The woofers for the N are being redone by Ohm now. And I will post the scans of the manual. Pretty much covers the "I" as well. Also have the sales brochure just before the I and M and N came out. I will get them posted. Sound quality is perfect in my room. Using Mac Mc-30's to power them. Working on Bi-amping them with a Mac 2105 for the woofers. The sound of the speaker is amazing.

 

[nolasally]

As long as your happy with them, but pretty sure just about any person with some refoaming experience could have refoamed those woofers at a fraction of ohms costs and possible even local to you!

 

[Ohming]

Hey Metaldaze, a fellow i owner here. Great to see the enthusiasm for these great speakers. I find that mine give plenty of clear deep bass without the need for the activator, but I think that is because of my room, but you have gotten my curiosity up now.

I just want to add one thing, I have a lot of respect for Ohm acoustics. John and Evan have picked up the phone when I called, and answered my questions with genuine interest and sincerity. I even got some troubleshooting advice for free. Those that don't want to take on a repair themselves, I applaud you for sending the speaker to Brooklyn for repair, or ordering replacement items and keeping these guys going.
I have never tried calling JBL and asking to speak with their resident audio engineer to discuss some aspects of my L7's. But if I did, I doubt that any conversation happen, but i could be wrong.

 

[Diamond Blue]

They needed complete rebuilding. I priced out buying the parts and doing it myself. $30 more per woofer to have them do it. I would have done it if it was just foam. I re-foamed the passive radiators. This is what they looked like when i sent them in

 

[MetalDaze]

Metaldaze Thank you. I found the original owners manual from my Ohm N & M's. The woofers for the N are being redone by Ohm now. And I will post the scans of the manual. Pretty much covers the "I" as well. Also have the sales brochure just before the I and M and N came out. I will get them posted. Sound quality is perfect in my room. Using Mac Mc-30's to power them. Working on Bi-amping them with a Mac 2105 for the woofers. The sound of the speaker is amazing.

I bet they sound super sweet in the presence being powered by those Mc-30's.

Bi-amping them certainly makes them move into another realm. I have tried it before, but in my room it was just too much. My A21+ is more than enough for them given the size of the space I'm in. I instead added a Rythmik subwoofer to extend my low end out to ~10Hz (umik-1 & REW measured). The SPL was already capable of going beyond where I need it for my current living situation.

Evan told me when you hook up the subwoofer of the "aye's" in 'bi-amp' mode - the impedance of the subwoofer itself is actually around 16 ohms. Similar to that of the larger Electro Voice, Eminence and Altec Lansing speakers with 12 & 15 inch woofers. So if your amp has taps for 4, 8 and 16 ohms. It may be beneficial to try the subwoofers on a higher impedance tap. Either way, the speaker sounds great and I'm sure they'll sing just as sweet, with more control and impact on the low end.

I've also always kept my eyes peeled for an N or N2 subwoofer. They are very rare as far as I can tell. That is super cool you have one and I'm sure it'll be better than ever after coming back from it's factory refresh.