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pk2carlos 5th May 2012 03:16 PM

Problem in response
 
5 Attachment(s)
I have made a vented box for Visaton driver HX 10 Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories , but there is a problem. I get a "hole" in response with low point at 147 Hz which is more than 5 dB deep and it was clear that something is wrong even before measurement. I tried closed version and sound is somewhat better but still not good and measurement shows even bigger hole in response. Inner dimensions of the box are 28,1 x 17,3 x 22,2 cm (HxWxD) and outer dimensions are 31,7 x 22,2 x 25,8 cm (HxWxD) and volume is a bit more than 10 liters.

Any idea what is the PROBLEM?

First picture is vented box mesurment, second closed box and the rest are pictures of box itself :-)

Inductor 5th May 2012 04:18 PM

If anybody else answers you, I would say it's reflections and other room related. Try mic close "inserted" to the driver.

jim1961 5th May 2012 04:26 PM

Quote:

Originally Posted by Inductor (Post 3012779)
If anybody else answers you, I would say it's reflections and other room related. Try mic close "inserted" to the driver.

My first feeling is similar. Might try measuring them outside where you can be sure the measurements are free of room effects.

WaVeInFoRm 5th May 2012 04:54 PM

because of the nature of sound and its high speed, even with the mic a mm from the cone peeks and trougths that are ariving in and out of phase with the cone will still be recorded. so that wont work

best try outside. i agree it is likely room related

one things for sure its probubly not that horrid mesh you have over the speaker. a mesh that i would remove if i where you. just my preferance

boris81 5th May 2012 05:16 PM

Probably nothing wrong with your speakers! It looks like a "natural" room interaction. Indoor measurements are only accurate until the first room reflection reaches the microphone. For my room that's about >800Hz. You can see the reflection in the Impulse Response plot. Use an option for a Gated view on your software if you have it.

You can do a near-field measurement for your low-end. Place the microphone as close to the woofer as possible without touching. This will be only accurate below about 200Hz. Note that the port output will not be included.

pk2carlos 6th May 2012 05:15 AM

Thanks for your answers :-)

Room could be the problem, since I noticed the sam thing in other loudspeaker, it wasn't that noticable but the frequency was the same.

Will try near-field mesurment. Out door isn't an option, since I don't have laptop and mesurment box is conected with USB cable.

In the first picture which is bassreflex mesurment it is possible to see also the peak in response but the impedance curve is close to perfection. Do you think I should try lower frequency tuning?

Quote:

Originally Posted by WaVeInFoRm (Post 3012816)
one things for sure its probubly not that horrid mesh you have over the speaker. a mesh that i would remove if i where you. just my preferance

The mesh is instaled in a way that would leave holes in a basket if I removed it.

giralfino 6th May 2012 08:03 AM

Quote:

Room could be the problem, since I noticed the sam thing in other loudspeaker, it wasn't that noticable but the frequency was the same.
Move the speaker around in the room, try different height. If the problem is in the room, moving the speaker will make differences in the FR. I have a similar problem, quite evident when playing George Michael's "My Baby Just Cares For Me" with a sequence from a double bass. If I move in the room there is a place where the sequence has a dip, in other places or outside the sequence plays fine at the same level.

Quote:

In the first picture which is bassreflex mesurment it is possible to see also the peak in response but the impedance curve is close to perfection. Do you think I should try lower frequency tuning?
Your tuning is way too high, there is a high peak in the measured response. For a maximally flat response the tuning should be around 55Hz, for a mild peak try around 65Hz. I suspect you used a too large reflex tube, see what you can do to obtain 55-65Hz tuning. IMHO the driver is really optimized for a satellite+sub combination: a closed box of 2-5L switched to the sub at 100-150Hz.
(Note: I didn't simulate for excursion limit, the tuning has also influence on this)

Ralf

mdocod 6th May 2012 08:35 AM

2 Attachment(s)
As others have said, the room seems to be to blame... Hornresp closely follows your charted response for the box less the dip at ~150hz, but no resonance issues show up in the range you are having problems.... See attached simulations... [I estimated the port dimensions very roughly, but close enough IMO]...


What I can't figure out, is the purpose of the port in this design. If the speaker is being used as a mid-bass with a sub, then the port is just an opportunity for undesirable resonances, If this is being used full range, a smaller diameter port would create a much more useful tuning to get some useful flat bass response with minimised resonance issues.

pk2carlos 6th May 2012 05:14 PM

Quote:

Originally Posted by giralfino (Post 3013375)
Move the speaker around in the room, try different height. If the problem is in the room, moving the speaker will make differences in the FR. I have a similar problem, quite evident when playing George Michael's "My Baby Just Cares For Me" with a sequence from a double bass. If I move in the room there is a place where the sequence has a dip, in other places or outside the sequence plays fine at the same level.

Will try this and see what will happen.


Quote:

Your tuning is way too high, there is a high peak in the measured response. For a maximally flat response the tuning should be around 55Hz, for a mild peak try around 65Hz. I suspect you used a too large reflex tube, see what you can do to obtain 55-65Hz tuning. IMHO the driver is really optimized for a satellite+sub combination: a closed box of 2-5L switched to the sub at 100-150Hz.
(Note: I didn't simulate for excursion limit, the tuning has also influence on this)
I'm a bit woried about excursion, thats why I would like to have tuning at Fs of driver, and use it as a single unit, without sub. Also vil try to put something in the box to get a smaller volumen. Do you think quick sand in plastik bag will be ok, since it is easy to mesure the volumen?

pk2carlos 6th May 2012 05:25 PM

Quote:

Originally Posted by mdocod (Post 3013392)
What I can't figure out, is the purpose of the port in this design. If the speaker is being used as a mid-bass with a sub, then the port is just an opportunity for undesirable resonances, If this is being used full range, a smaller diameter port would create a much more useful tuning to get some useful flat bass response with minimised resonance issues.

Idea is to be used as a full range. In theory the port should be as big as loudspeaker and since there is enought space I decided to use this one. I don't think that smaller diameter would make any differenc or would it?
Wouldn't it be only shorter for the same tuning?


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