The difference between 60hz and 80z?

At 80Hz, you're more or less safe to push almost any speaker to high volumes, but smaller speakers set to 60Hz will be more prone to damage.

 

Thanks David.

 

Would you advise against having my B&Ws set to 60Hz then?

 

- I do like films like Hulk and The Avengers etc!

50/50. Using a higher crossover point does need a more capable subwoofer. With a PV1, it's a shame you can't choose 70Hz and split the difference! I personally would select 80Hz.

Thanks David. I appreciate your expertise and advice as always. 

... About 20hz.

I think so too. Pushing small speaker to work with low frequency is not good idea. I don't think that you will kill speaker,

but sound will be worse for sure. It is better to use only subwoofer for low frequencies.

 

I prefer the sound of my system with the front speakers crossing over at 60Hz. My concern and question was purely around whether this is likely to damage them when playing high volume, deep bass, action films. 

 

Based on David's comments, I don't think I'll take the risk. Perhaps I should consider updating the 685s to 684s at some point in e future. Then perhaps I can get away with running a lower crossover more safely?

With large (just over a metre tall) front speakers, the automatic speaker calibration by the receivers designates the front speakers as full-range and so I don't have to worry about crossover frequencies at all (from a previous thread, I know that David at Frank Harvey would still choose a crossover frequency of 80 Hz even when using floorstanding speakers). It's a personal choice, but I certainly prefer having large front (and in my rooms, large rear speakers also) to having smaller speakers and having to consider crossover frequencies. Of course, restricted space in some households may force the choice of smaller speakers.

Just because a speaker is over a meter tall doesn't mean it isn't susceptible to damage surely? A loud, very deep bass note that over stretches a drive unit is bad news full stop. 

 

I know large speakers go deeper so have a greater ability to play deeper notes, but the sort of sub sonic bass that is on some blu-ray discs is beyond the majority.

 

I mentioned changing my B&W 685 bookshelves for the 684 floorstanders earlier. Although I fancy doing this, I cant see that the 684 would be any more resilient. I believe it uses the same drive units as mine, it just has two bass drives rather than one. How would this make them anymore resilient to a lower crossover?

 

I don't think your speakers will struggle or get damaged by 60Hz. By definition, sub sonic is below 20Hz. If your speaker isn't capable of handling it, you simply won't hear that lower frequencies. But the speakers won't get damaged.

 

That's a very good point. More specifically, if the crossover is set at 60Hz, the speakers wont be receiving bass any lower than 60Hz as those signals will be sent to the sub.

 

The specs of my speakers suggest that they go slightly lower than 60Hz so a setting of 60Hz should be well within their capabilities. I wonder why David at Frank Harvey was recommending 80Hz as safer?

 

Any ideas?

Only he can answer that! 

I wouldn't call your speakers small.

There's nothing wrong in setting the crossover point to the +/-3dB frequency response figures stated by most manufacturers - in this case, 49Hz. For the most part, a 60Hz setting will work fine, but bear in mind that the 685 mid/bass driver has to cover a range of almost 4000Hz. If that driver has to reproduce a number of frequencies at the same time, as well as producing some loudly, some quietly - this will put a lot of strain on the speaker, especially if it is nearing its maximum output, or some of those frequencies are lower than it can comfortably produce. If all speakers could do this, there'd be no market for high end ones.

Suffice to say, playing a full range signal from a Bluray - which can have very energetic content right down to 10Hz or lower, can damage a hi-fi speaker if it is set to large. A speaker will try and recreate what it is given. 

Upping the crossover point eases the workload on the mid/bass driver, and leaves much of the hard work to the subwoofer - which lets face it, has been designed to work up to at least 80Hz, with some having been designed to work right up to 150Hz or even 200Hz should it be needed. The result is that because the driver has less to do, it can do what it does more cleanly.

There are a few different ways you can set up a 5.1 system, and having been demonstrating and selling AV systems for over 20 years (yes, back to VHS and Laserdisc days and the birth of Dolby Surround), I feel that THX's guidelines generally produce a better sound, and produces a more predictable result in almost any room, regardless of the issues that awkward rooms can throw up.

There are instances when using floorstanders in a hi-fi based 5.1 system will produce better sounding results than what I would normally recommend, but this would rely on the room being acoustically good, and the floorstanders being particularly capable, which would normally mean higher end ranges.

Thanks again David.

 

Would you consider that changing my 685s for 684s would be an upgrade (in a system used exclusively for home cinema/ tv)?

 

Or, am I right in thinking that there would be no benefit whatsoever if the crossover is set to 80Hz or 60Hz. I assume with one of these crossovers set, I would get exacly the same out of either speaker (which I think use the same drivers anyway) and I would not benefit from the larger cabinet or additional drive unit in the 684 as all the lower frequencies on going to the sub?

 

Based on my rational above, why would anyone use floorstanders in an AV system if they wanted to follow THX's recommended 80Hz crossover?

That is right. But remember that crossover doesn't cut signal like on/off switch. It all depends on the crossover and its characteristicsThe best way is, to check speaker characteristics. If it shows that the speaker works well at 60hz, than everything should be fine.I prefer to use sub for low frequencies beacuse it was made specially ​​for it.