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Multi-Way Conventional loudspeakers with crossovers

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Old 20th November 2016, 09:11 AM   #21
Drummer 35 is offline Drummer 35  Spain
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I think I can go later with the damping material. I have to build the box first.

Yesterday went to visit the friend who will build the boxes. He has mdf, plywood, lots of kinds of solid wood and a cnc machine.

Will make first a proto using 19mm mdf or cheap solid wood, tunning it, following your recommendations, to drivers fs. Plan on putting some stringers inside to reinforce the box and help internal "damping"

I think we can make the box bigger and get 40-45 liters. Are there any drawbacks using a bigger box?. I want a "punchier" speaker, with attack and detailed sound, not a "boomy" thing. Dont know if building a bigger box will be good for that.

I can do it 25-45liters. Any thoughts?

Thanks again for all your help!

David
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Old 20th November 2016, 09:45 AM   #22
Juhazi is online now Juhazi  Finland
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Make a closed box! You will get good low bass with some eq.
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Old 20th November 2016, 11:28 AM   #23
Drummer 35 is offline Drummer 35  Spain
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Not sure if this driver will work on a closed box.

Thats what I got on winISD:

spl graphs.jpg

group delay graphs.jpg

Not sure if I will "feel" those extra 10 liters, and will be easier to make a small box, so, Im torn between the 30l/60hz and 30l/70hz graphs.

Wont be using a subwoofer, only those speakers.

What do you think?
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Old 20th November 2016, 12:02 PM   #24
Charles Darwin is offline Charles Darwin  United Kingdom
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Quote:
Originally Posted by academia50 View Post
I think the felt behaves better
I find acoustic foam to be almost ideal for ported boxes given its properties.

It absorbs almost everything above 250-500Hz (depending on density and thickness) while leaving frequencies below 125-250Hz almost completely unmolested which is what you want for the port to work as intended.

The purpose of damping in ported boxes is mainly to avoid reflections from inside the box getting out via the port or through the woofer cone.
Also helps to avoid standing waves.
That is to say that for example 500Hz has a wavelength of 68cm.
The OPs box will be smaller in every dimension but with foam lining absorption above 500Hz is pretty much 100%.


With that in mind it becomes clear why it is pointless to damp the baffle.
In fact the danger is overdamping (attenuating bass frequencies rather than just absorbing mids and highs) which impacts on the functioning of the port.
Extremely overdamped boxes behave like a sealed one.
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Old 20th November 2016, 08:53 PM   #25
academia50 is online now academia50  Argentina
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Charles Darwin :

Well, I appreciate the answer, but my own experience tells me that it is not something that greatly influences sound.
The JBL brochure I enclosed, in effect, says that absorbent material should be placed on all the walls of the box. But then he explains how to assemble the baffle. (Front panel) ie the latter wall is excluded.
So far it all coincides with the general recommendation, and I did so.
I listened to the boxes for many years. One day I found the booklet on the net and read it again and there I thought:
Have I misunderstood? (There was no internet or Google translator, OK? Haha) Is not recommending to put absorbent material in the baffle too? Then I did. First only in a box and I compared the sound between them. I placed them close together and in the center of the room, the sound source in mono and passing the balance from left to right.
To my surprise, the bass was more controlled, less resounding, and the voices softened.
So I also made the extra stuffing in the second baffle, and it will look like this.
I'm sorry for the off topic. I'm still waiting for some reliable documentation on this point, I can not find anything on the net.
*Greetings, and thanks again for your kind response.


Drummer 35, sorry OT and very luck for you built !!
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Old 20th November 2016, 08:59 PM   #26
academia50 is online now academia50  Argentina
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Quote:
Originally Posted by Drummer 35 View Post
Not sure if this driver will work on a closed box.
I think the same. You will lose efficiency (less SPL) and will not get very low on bass frequencies. The speakers for enclosed cabinets (I remember very well the famous AR) must have very loose compliances. )
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Old 20th November 2016, 09:25 PM   #27
academia50 is online now academia50  Argentina
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Two links that can be of great help in case of choosing a bass reflex system :

Bass reflex speaker design - easy explanation - Audio Judgement

Port Calculation
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Old 20th November 2016, 11:28 PM   #28
Charles Darwin is offline Charles Darwin  United Kingdom
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Quote:
Originally Posted by academia50 View Post
To my surprise, the bass was more controlled, less resounding, and the voices softened.
I had a very similar experience with my Tannoy LRMs but I just added acoustic foam to the back of the box as I found the original damping (1inch glassfibre) insufficient for the job.

Drummer 35 when you build your boxes make sure there is a clear path free from obstructions and damping material between the back of the woofer cone and the port tube!
30L looked good to me. I don't think there is any point in going bigger and 25L might be just as good.

Last edited by Charles Darwin; 20th November 2016 at 11:30 PM.
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Old 21st November 2016, 07:23 PM   #29
Drummer 35 is offline Drummer 35  Spain
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Will order an acoustic foam roll, some rear connectors and an sliding vent for testing.

The speakers will be next to the wall so the vent will be located on the front.

After I get a good box tune, I want to make the front with a slotted vent. I can make a big one with a long throat or a smaller one with shorter throat, correct?

Wich is the best solution to avoid the vent producing air sound?

Thanks
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Old 22nd November 2016, 01:43 PM   #30
Charles Darwin is offline Charles Darwin  United Kingdom
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ISDonline lets you calculate the likelihood of port chiuffing/whistling.

I assume you can do that on WinISD too but I'm on a Mac so I can't say for certain.
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