Benefits of sealed enclosure speakers?

[Electro]

Electro, those are indeed interesting! Especially this part:

Frequency response: 28 - 35000 Hz ±2dB

Sensitivity: 90 dB, re 2.83V @ 1m

Apparently the measurements were made in an anechoic chamber at Seas .

http://translate.google.co.uk/translate?hl=en&sl=da&u=http://www.lydogbillede.dk/test/electrocompaniet-the-nordic-tone-model-1/&prev=search

Interestingly, tested with Hegel amplification, including the H160.

I thought you might spot that *smile*

It does not surprise me at all Hegel amps are very good indeed , they also share a similar core design with Abrahamsen /Electrocompaniet .

 

[Electro]

Apparently the measurements were made in an anechoic chamber at Seas .

Some measurements may have been taken in the SEAS anechoic chamber but I see no reason to assume that is where the extension to 28 Hz has come from in a raw form (i.e. without some processing to simulate a room). A small anechoic chamber like that will start to suffer from significant reflections below about 100 Hz and so it would be a very poor sign if the very low frequency measurements came from a microphone placed a few metre in front of the speakers.

It is not difficult to measure the low frequencies by placing a microphone close to the woofer to minimise the influence of reflections and doing it outside to avoid issues like leaky room pressurisation. However, what is measured is not what would be heard at the listening position and what is heard at the listening position is strongly influenced by the room. Some assumptions need to be made to get a reasonable figure. The first is what is often called "baffle step correction" where the low bass stops radiating mainly forward like the high frequencies and progressively shifts to radiating equally in all directions. The second is the boundaries of the room taking that omni directional radiation and directing it towards the listener. The first effect could be fairly successfully measured in the SEAS anechoic chamber because most of it occurs at high enough frequencies. The second varies from room to room and placement within the room and so it is unreasonable to include it without stating what has been assumed. Since a speaker with a perfectly flat frequency response in an anechoic room would normally have too much low bass at the listening position in a real room it is not unreasonable to want to include the second effect for a speaker that has too little low bass in an anechoic room but is likely to sound about right in some rooms.

Stereophile take their low frequency measurements by measuring outside close to each woofer and port and then adding them up. They then join this measurement onto the gated (removes reflections) in room high frequency measurement at a few hundred Hz (I haven't looked up the exact figure and how/if they smooth the join). However, they make no attempt to correct for either the room or "baffle step correction" and so speakers that a have a reasonably flat frequency response at the listening position are shown with a rising bass response like this one from Sony which has a similar pair of 8" woofers in a tower. I suspect a fair few readers will fail to correctly interpret such plots particularly as boundary gain in most room locations tends to kick in and reduce the required amount of baffle step correction to less than the full 6 dB that Sony seem to have implemented.

I bow to your superior knowledge !

 

[hg]

I bow to your superior knowledge !

I am waffling on a bit because I am interested in what Electrocompaniet might have done in order to get their 28 Hz. This review on their website shows measurements, near field by looks but I have not checked, and quotes 51 Hz for the bass extension which is in line with my reasoning earlier.

I doubt Electrocompaniet have simply made up the numbers and would expect them to be able to put forward some form of measurement or possibly analysis to support the claim if challenged by the advertising authorities. Would like to know what though. Again, it looks a reasonable bass extension when used in a room and so it would be to an extent wrong to consider the bass extension to be 51 Hz as shown by the measurements. Interesting stuff.

 

[SteveR750]

I bow to your superior knowledge !

I am waffling on a bit because I am interested in what Electrocompaniet might have done in order to get their 28 Hz. This review on their website shows measurements, near field by looks but I have not checked, and quotes 51 Hz for the bass extension which is in line with my reasoning earlier.

I doubt Electrocompaniet have simply made up the numbers and would expect them to be able to put forward some form of measurement or possibly analysis to support the claim if challenged by the advertising authorities. Would like to know what though. Again, it looks a reasonable bass extension when used in a room and so it would be to an extent wrong to consider the bass extension to be 51 Hz as shown by the measurements. Interesting stuff.

Right, that is interesting. Given the ATCs are specced (I presume anechoically at 1 metre) at -6dB at 48Hz, what would their in-room response be closer to? The room size is approx 23' x 14' x 9' to a double door width archway that is open into the dining room which is around 14' x 14' x 9'?

I'm contemplating getting a subwoofer (separate thread to come), although I still suffer from the probably unfair stigma that they simply make the sound 'ponderous' so ostensibly for listening to movies rather than music, which means a more affordable model might suffice, as ATCs own subs are not cheap!

 

[matt49]

I'm contemplating getting a subwoofer (separate thread to come), although I still suffer from the probably unfair stigma that they simply make the sound 'ponderous' so ostensibly for listening to movies rather than music, which means a more affordable model might suffice, as ATCs own subs are not cheap!

Suck it and see, Steve. I'd have thought though that with a DSPeaker Anti-Mode in the chain it should be easy to get pretty good results.

I plan to go the sub route myself sometime next year. My speakers have 10" woofers and are 29–23,000 Hz ±3dB. I still reckon a sub might bring big benefits.

 

[hg]

Right, that is interesting. Given the ATCs are specced (I presume anechoically at 1 metre) at -6dB at 48Hz, what would their in-room response be closer to? The room size is approx 23' x 14' x 9' to a double door width archway that is open into the dining room which is around 14' x 14' x 9'?

That depends on the room dimensions, what the walls, floor and ceiling are made of, the main room features, how leaky the room is to pressurisation, where the speakers are located, where the listener is located, etc... It could be simulated accurately but that would need empirical information you are rather unlikely to know such as the acoustic impedance of all the different boundary surfaces and how they vary with frequency.

If you want to have an idea of the smoothly underlying gain due to the boundaries and room pressurisation a free program like this can help. This also includes "baffle step correction" which the measurements of your ATC speaker may or may not include depending on whether they are near field or taken in an anechoic chamber. The main page shows the separate contributions of baffle step correction, boundary reinforcement and room pressurisation. Now my suspicion is that Electrocompaniet might be using something like this to get their 28 Hz because the curves are smooth and they quote a +/- 2 dB variation. Although dependent on all the details the amount of gain is in the ball park of 10 dB which is around the amount we are looking for to get from 51 Hz to 28 Hz.

Of course what is missing from these smooth curves are the room modes which will remove any question of a +/- 2 dB variation in all but the most aggressively controlled acoustic spaces. To get an idea of what these might be doing in your room you could download the free REW program, click on the room simulation button and interactively change the room dimensions, boundary conditions, speaker number, speaker locations, listener location,... to see how the response changes, often quite dramatically, at the listening position.

 

[SteveR750]

Thanks, though it's all perhaps academic, I'm sure I posted this somewhere else previously...

I'll try the programmes out, as not owning a turntable any more means there is nothing to tinker with.

 

[SteveR750]

I'm contemplating getting a subwoofer (separate thread to come), although I still suffer from the probably unfair stigma that they simply make the sound 'ponderous' so ostensibly for listening to movies rather than music, which means a more affordable model might suffice, as ATCs own subs are not cheap!

Suck it and see, Steve. I'd have thought though that with a DSPeaker Anti-Mode in the chain it should be easy to get pretty good results.

I plan to go the sub route myself sometime next year. My speakers have 10" woofers and are 29–23,000 Hz ±3dB. I still reckon a sub might bring big benefits.

Matt I agree that the Antimode would be useful if adding a sub, so that its' output is controlled so that the troughs / nodes are "filled in" by the sub, without adding anything to frequencies where the room response is OK. But, J River can do this, but I'd need to buy and calibrate a mic, and find some software to analyse the sweep in order to determine the settings in the DSP. A whole lot cheaper than Antimode solution, but a lot more fiddly. It might be a lot easier to simply add a thumping (sorry) great sub and just bathe in the waves of unadulterated gut churning LF. A bit like a stadium rock gig then, which is perfect reproduction.

 

[hg]

Thanks, though it's all perhaps academic,

Not sure I would agree. I think it is more of an interest in understanding how and why things work. When I first started taking an interest in home audio many decades ago a fair few held such an interest but today it seems to be very rare. Most of the posters here are not averse to a sound bite version of what is going on but seem to have little interest in how or why. Which is fair enough. A hobby interest is a hobby interest and given the currently important role of audiophile nonsense an interest in how and why might be a bit counter productive.

 

[SteveR750]

Thanks, though it's all perhaps academic,

Not sure I would agree. I think it is more of an interest in understanding how and why things work. When I first started taking an interest in home audio many decades ago a fair few held such an interest but today it seems to be very rare. Most of the posters here are not averse to a sound bite version of what is going on but seem to have little interest in how or why. Which is fair enough. A hobby interest is a hobby interest and given the currently important role of audiophile nonsense an interest in how and why might be a bit counter productive.

Which is my definition of academic. I'm also interested massively how things "work", but sometimes too lazy to act upon the information. I have other hobbies that absorb more time, cost and data analysis because the outcomes are more important for me, so the prospect of really ironing out a slight bass deficit in my room is fantastic in theory....