Ohm Model H impedance

[harpsm]

I recently snagged a pair of Ohm Model H speakers at a thrift shop and I need to know nominal impedance to make sure it will get along with my relatively wimpy receiver.

Here's the confusion: Ohm's website says the Model H has 4 ohm "typical" impedance, but the serial number plate on my pair says IEEE impedance is 8/6 ohms, and I'm not sure what this pair of numbers means. Adding to my confusion, I found a picture of a Model H online that shows 8/4 ohms on its serial number plate (the speaker in the pic has a higher serial number and different color plate than mine).

Any advice would be greatly appreciated. I emailed this question to Ohm last week and have not received a response.

Jeremy

 

[mikte15]

Wow, Nice Find. I've seen posts of folks looking for those.

Ohm has quite a following (probably due to the F model). I like the older conventional speakers like the H's, C2's, I's, B2's, and the Ls which I'm waiting delivery on. I'd like see a picture of what you found with the grills removed.

As to your question, this is purely my guess. I believe the H's with their passive radiators can use quite a bit of power. The Ohm site lists 20-100 watts. How much power do you have? If I had them I would want a 50+ watt amp.

Good luck with them.

 

[Cosmos]

Jeremy,

As I recall, the figure of 8/6 (which means 8 ohm nominal 6 ohms when checking with an ohmeter DCR) is about right. All speakers have changing resistance across a frequency band and therefore resistance that your amplifier sees is not a fixed value.

We never had any issues driving them in the showroom with any amplifier. However, they are great bookshelf speakers and it would be nice to power them with a healthy high quality amplifier. In essence, power them carefully with what you have, but try to upgrade as soon as possible.

You should love those speakers. They were, by far, my favorite Ohm bookshelf speaker. I'd love to find a pair myself.

 

[harpsm]

Thanks for the replies! Cosmos, I appreciate the info. I wonder why a later production of the H has a different nominal impedance, and why Ohm's website would list 4 ohm impedance for this speaker. Curiosities aside, it sounds like these speakers should get along with my Onkyo TX-SR501 receiver (a thrift store find itself) rated at 65 wpc into 8 ohms. I also have a 70s vintage Sony 6036 receiver that might have a power supply better able to handle low impedance, though with a rating of 15 or 20 wpc it might not have enough wattage to drive the H's.

I get just about all of my gear from thrifts, so I was pretty excited about finding these speakers. I can't wait to hear how they sound! I'm hoping they'll be good enough to replace my Cerwin Vega RE 25s as fronts.

Mikte - I'm in the process of refoaming the woofers, but I'll try to remember to post a pic when they're finished. Cabs are a bit scratched and the low tweeter grills are dented in a bit, but all the drivers work.

 

[harpsm]

Well, I've spent some time A/B comparing the Ohms to my Cerwin Vega RE 25s and I can say that while it's not a blowout, the Ohms are the clear winner. Overall, they have a cleaner and warmer sound, with a much more balanced midrange compared to the CVs' rock-oriented bass and treble emphasis. Actually, I found the Ohms to be a bit too reserved with rock music, but EQ'ing the bass and treble up on the receiver gave them more presence. The CVs, with their 10" woofers are the clear winner in bass extension and volume, but using a BIC F12 subwoofer crossed at 60 Hz eliminates that advantage. Overall, a very well spent $12 for the speakers and new surround foam!