REGISTER NEW USERLOST PASSWORD? WELCOME, Logout

Overkill

Paul's Posts — 24 June 2012

By

Overkill

When a trumpet or trombone plays loudly – or a bass drum or gong is hit hard –  the sound that is produced by the instrument is dynamically linear with the softer sounds that instrument can make.  The same cannot generally be said about a loudspeaker that is reproducing those sounds.

Imagine for a moment the difference we might hear of an orchestra playing loudly in a small room vs. that same orchestra playing loudly outside – the differences between loud and soft in the first example would not be linear because the small room the orchestra is playing in would overload and compress those dynamics.  This is fundamentally the same thing as what most loudspeakers will do when they try and reproduce large dynamic range swings.

What’s interesting is that we don’t have a means of measuring and calling attention to this form of compression in loudspeakers.  Why?  Because technically most loudspeakers are capable of reproducing without compression the full dynamic range found on most recorded music – and that IS something we can measure.  What we don’t measure is the strained sound or the ‘apparent” compression one hears in such loudspeakers.

I don’t know enough about all this to give you any hard facts.  What I can share with you is my experience listening to many a loudspeakers system – and on most this change in character of the sound between the loudest and the softest passages is almost always evident on all but the biggest systems I know of.

Listen on yours to see what I mean.  Note how the character of the instrument or voice changes when the presentation gets really loud vs. really soft.  Some of this is most certainly your room but much of it is your loudspeaker – because on the biggest systems I know of (like the IRS and Gen 1′s) this problem doesn’t exist – even in a smaller room.

email Overkill Forward to a friend and help us engage more readers

Get new and fresh stories like this each morning by joining the folks reading Paul's Posts. Click here

Related Articles

Serving it up Rolling it off What’s all the fuss about? Young turks

Share

About Author

Paul McGowan

Paul McGowan is the CEO and co-founder of PS Audio Inc. a Boulder Colorado design and manufacturing company of high-end audio products and services. McGowan has been designing and building high-end products for nearly 40 years. Hobbies include skiing, music, hiking, artisan bread baking, kick boxing and cooking. He lives in Boulder Colorado with his wife Terri and his 4 sons.

(11) Readers Comments

  1. mitch352

    June 24, 2012 at 7:07 am

    Paul, I have been reading your post since you started them and I always enjoy them a lot. On the overkill
    post, since most of your readers don’t have the room or money to own IRS or Gen 1s speakers wouldn’t it make more sense to discuss ways to achieve the best sound with more real life speakers? Thanks

  2. Terry Franklin

    June 24, 2012 at 11:18 am

    Perhaps your speakers need to be thoroughly isolated from room vibrations. Obviously the louder the music the more acoustical feedback is available to degrade the sound. This may not be the entire problem but it has to be part of the equation.

  3. Countach

    June 24, 2012 at 11:20 am

    30-35 Years ago JBL started to investigate why the sound, sounded more compressed at higher levels. They measured at an average level of 80 db and 90 db. They compared the levels of the peaks at the two average levels and found out that the peaks at the higher level was only 6 db higher. They found out that the heat built up in the magnetic system and voice coil was the reason (“heat compression”). JBL started to improve the heat dissipation on their speaker elements, but still the problem are to get out the heat from inside the box. Speaker element Volt has solved the problem with “cooling fins” in front of the woofer and I have seen demonstration how effective this is. I have only seen these elements used in rather huge speakers like 70 to 150 litres (by different speaker manufacturers).

    • June 24, 2012 at 3:33 pm

      Heat compression of the voice coils certainly can be a contributing factor and is probably one of the reasons the big systems don’t suffer it so much because they have so many drivers that none ever work hard – but while i understand heat compression – having worked with active means to eliminate that with servo controller woofers – I remain unconvinced that’s all there is to the story.

  4. Steve Parry

    June 24, 2012 at 11:58 am

    I know what you mean. Years ago I owned the Infinity RS-1s, which were the baby IRS. They had two towers with six eight inch woofers a side. They reproduced low bass, such as Reference Recording’s Dafos, like nothing I have heard since (I was lucky to have them in an ideal room too).

    I wonder if there is a way to assess this compression. Pulse full range tone of varying duration and spacing. Record this impulse response, across the frequencies. Then do the same with successive increases in volume. Maybe this is already done…I am no speaker designer. The measurements would vary if performed anechoically versus various room sizes.

  5. oliver T. Finch

    June 24, 2012 at 9:34 pm

    Every driver has a comfort zone and if made to make excursions out of this zone strain will result and the sound will be compressed. To keep the driver in its comfort zone and increase the volume just increase the number of drivers. Now you have a line source with its big. effortless and dynamic sound which also plays very very loud and the drivers are still moving within their comfort zones. As for the size of the room it becomes an issue the moment it is over driven.

  6. alan

    June 25, 2012 at 8:00 am

    Paul, I believe I understand what you’re saying. A student protégé of mine (age 19) just completed (he hasn’t begun tweaking) a line array dipolar speaker that consists of 8 six inch woofers and twelve 1 inch tweeters per side, all purchased on clearance from Parts Express (a relatively simple, inexpensive project). He hasn’t developed a golden ear, yet read what he has to say after his first listen to his new speakers:
    I spent all day listening to the speakers. Surprisingly, they seem to play at about the same level as my klipsch speakers on the same volume setting, which are extremely efficient. They sound pretty amazing (especially for the cost). Easily beats out the speakers I bought for about the same price and the $650 B&W bookshelves I listened to at Best Buy. In my room it actually doesn’t need any boost in the lower end. I think it might be the concrete walls and the smaller area…

    • June 25, 2012 at 4:35 pm

      Makes me happy to read people of his age are tweaking still and building projects. Nice! it’s amazing what one can accomplish on his own.

Leave a Reply