# SVS Driver Size Definition



## Ed Mullen (Jul 28, 2006)

I received a notification via email that steve1616 had posted about concerns with how SVS defines its loudspeaker driver size. I tried to find that note here, and it has apparently been deleted. Anyway, I wanted to clarify how we define driver size anyway.

Industry standard has nominal woofer size being the largest dimension across the frame. Any deviation from this is typically to indicate the smallest dimension taken across a different direction on the frame. Please realize that the frame size and the actual cone diameter are never synonymous. A 12" woofer in a subwoofer does not have a 12" diameter cone - the cone is always smaller than the frame/basket size. And so it is with loudspeaker mid-bass woofers. 

For example, M-series woofers (any vintage) use 18cm round-frame woofers. This is close to 7". Peerless also makes truncated versions of the same frame, i.e. there are two flats cut into the frame on opposite sides. The distance between these two flats is 6.5". Same exact woofer, two different "sizes". 

So which diameter should be selected? Always select the larger of the two dimensions, because that remains constant regardless of whether any flats are cut into the frame. 

Another example is the typical 5.25" woofer. Such woofers are built on frames whose largest diameter is 6". But the frame is square-ish, and the smallest dimension is about 5.25". The SVS S-series uses square-ish basket woofers that - if they were truly round - would be called 6" diameter. 

The reason manufacturers publish the smaller frame dimension is for OEMs and designers who are interested in "packing in" the drivers closer together on the front baffle. But it is still the larger frame dimension that is a more reliable indicator of cone diameter. 

There are some inconsistencies on our website warranty/non-warranty parts pages vs. our website product pages where we have these drivers listed as 5.25" vs. 6" and 6.5" vs. 7". I'll make sure all the sizes are made consistent across all web pages.


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## steve1616 (Apr 6, 2009)

I also wanted to note that I never let anyone see your webpage that shows the dimensions or prices. I own my own company and would never want anyone to say harmful things about my business. It is also to note that not many companies would address this concern, especially this fast. Ed, do you ever sleep? Since my last thread was deleted, I wanted to re-post something that I said in the thread. I said, "regardless of woofer size, I have always been very impressed and their products have always exceeded my expectations by a considerable amount."


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## Ed Mullen (Jul 28, 2006)

Hi Steve:

Again, we define driver size by the largest dimension on the basket/frame. The S-series largest dim is 6" and the M-series largest dim is 7". 

Sometimes irregularly shaped frames make the job of defining woofer diameter a bit harder. The S-series frame is irregularly shaped, and is smaller than 6" in some locations, but if it was that size everywhere, there would be no locations for the screw holes. 

So we settled on the largest diameter on the frame to define driver size and we're being consistent with all loudspeaker and subwoofer drivers. The cone diameter will always be smaller than the basket/frame size of course. For example, our 12" NSD subwoofer driver has a 12" basket diameter, but the actual cone diameter is 9.5" to the center of the surround. But no one would classify this as a 9.5" woofer - it's a 12" woofer. 

I hope this helps, Steve. Thanks. 

PS - SVS really stands for Sleep Very Seldom :bigsmile:


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## steve1616 (Apr 6, 2009)

Ed, I didn't read your post closely the first time. I did remeasure the basket, and found that if I measure outside to outside at the widest points that I do come up with 6" on the STS series. I think the only reason I was confused is because most manufacturers call their mids a 6.5" even though the outside basket measures from 6.75" to just barely over 7". I guess their is really no set standard for how they are listed. 

On a side note, Ed or maybe Doc, can your MBS speaker put out as much bass or more than your STS-02 towers? If it can, how does it do that with just one 7" mid woofer?


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## Ed Mullen (Jul 28, 2006)

steve1616 said:


> Ed, I didn't read your post closely the first time. I did remeasure the basket, and found that if I measure outside to outside at the widest points that I do come up with 6" on the STS series. I think the only reason I was confused is because most manufacturers call their mids a 6.5" even though the outside basket measures from 6.75" to just barely over 7". I guess their is really no set standard for how they are listed.
> 
> On a side note, Ed or maybe Doc, can your MBS speaker put out as much bass or more than your STS-02 towers? If it can, how does it do that with just one 7" mid woofer?


Hi Steve:

You are right, there is no hard/fast standard to which every OEM strictly adheres. We selected the most commonly accepted standard for defining the size of subwoofer drivers, which is the OD of the basket/frame (if it is round), or the largest dimension across the frame (if it is irregularly shaped). If this standard is applied to the S-series and M-series, the result is 6" and 7", respectively. We are being consistent now for all woofers - subwoofer drivers, and loudspeaker drivers. 

The STS towers with 4 6" woofers can certainly play louder in the mid/upper bass regions than the MBS bookshelf speakers with a single 7" woofer. The S-series speakers are sealed and designed to comply with the spirit of the THX standard, which is a 2nd order acoustic roll-off @ 80 Hz combined with a 2nd order electronic roll-off (from the AVR) @ 80 Hz. 

The MBS can operate in either sealed or vented mode. In sealed mode it extends about as deeply as the STS. In vented mode, it extends deeper than the STS and acquits itself nicely down to 50 Hz for use in 2 channel rigs where a deeper crossover to the subwoofer might be desired to preserve as much directional bass as possible.


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