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Isobaric 8" expectations?!
Isobaric 8" expectations?!
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Old 9th September 2002, 08:22 AM   #1
Rarkov is offline Rarkov  England
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Question Isobaric 8" expectations?!

Hi,
I am making a tapered pipe pair of speakers using a 16.5cm driver. I really like the description of them...we'll have to see what they're really like! The problem is, I envisage virtually no bass. My speakers I have at the moment use Audax AP210G6 8" drivers. Obviously I have two, and me being me (a cheapskate), would like to utilise these in a sub. I thought about an Isobaric sub. The room is medium size and the size of the enclosure is not a problem.

Could anyone tell me how low I could hope to reach with these speakers? Any other suggestions. FYI the 16.5cm drivers I am using in the TP speakers are Audax AP170Z0 and Audax TW025M0. (They're easily available!)

Thanks
Gareth
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Old 9th September 2002, 10:21 AM   #2
navin is offline navin  India
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why isobarilk if you dont need to worrry about box size?

you can try bandpass to get max vol of bass out fo these.
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Old 9th September 2002, 10:33 AM   #3
Rarkov is offline Rarkov  England
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Hi,
Thanks, I'll look into this configuration. Will the bass from these still be 'punchy'. I love bass to add depth to music, but in moderation. It is of utmost importance that the bass notes hit when they are supposed to.

Will band pass provide this, because I've only been looking at sealed so far. I had thought about Isobarik because I had two 8" subs going spare, and I knew that this would reduce the box size by two and increase the power handling. That's all!

Gareth
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Old 9th September 2002, 11:17 AM   #4
navin is offline navin  India
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bandpass has its advantages and problems

1. the bass volume is good
2. the bass quality is not

i am not so sure about punchy bass (it depends on teh room, driver and design) but it will add a lot of foundation to the lower octave.

one reason I have used bandpass is to get bass out of a small box. also in places where the user does not want to see the driver.

a band pass sub can be hidden behind a sofa with min. difference to the sound.

regards
navin
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Old 9th September 2002, 02:13 PM   #5
Andy G is offline Andy G  Australia
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Default I would wait......

.... until you get the tapered pipes done. If you get them right, you might surprise yourself.

What 16.5cm driver are you planning on using btw !?
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Old 9th September 2002, 02:20 PM   #6
Andy G is offline Andy G  Australia
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Default I should read more closely, sorry !!

Audax AP170ZO ..... doh !!
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Old 9th September 2002, 02:58 PM   #7
mrfeedback is offline mrfeedback  Australia
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Gareth,
I recently had a good look and listen to isobaric subs with each having two Vifa (or Scanspeak or something Danish) 8" long throw polypropylene cone woofers as the low end for some large ES panels.

The cabinets were about 22" square and 12" high or so.
These isobaric subs were crossed out at 150 Hz (? dB/Oct) and and tried with several high power tube, icepower and pro amps (600W/4 Ohm) in a very large room/volume.
Because of the sensitivity and power handling (flashover) of the ES panels max sustained power was around 300W on each of the bass amp Led VU meters.
The bass was utterly clean and powerful non boomy or resonant, and did not give a hint of bass nasties even when pushed hard (real hard).

On the downside perhaps are that they need horsepower and perhaps a little lack of attacking in the bass, but this may be a product of very dead polyprop cones or the product of usage with ES panels or the product of just plain clean response.
Either way they worked rather well and avoid totally the characteristically boomy/resonant/droning bass of commercial standard ported sub cabinets.

I suggest that since you have the drivers already, it is worth the investment in research, fabricating and tweaking.
I have seen designs where the cones are facing each other with minimal volume between them, and the rear of one cone radiating into the room, but I dont have any performance comparisons.

You have only time and particle board to lose.

Eric.
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Old 9th September 2002, 05:08 PM   #8
Rarkov is offline Rarkov  England
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Hi,
Thanks for all of your great input! Does anyone know what I could expect from my tapered pipes? They have internal dimensions of 16.5cmx20.3cmx91.7cm or there abouts, and a 71cm tapered board that goes from the top of the 8.1cm opening.
I know this isn't very clear...For a rough idea of the shape, I did a quick render of my concept...

http://ena.brinkster.net/db/diyhifi

Any idea what this Audax combo will be like? (AP170Z0, TW025M0)?

Thanks
Gaz
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Old 9th September 2002, 06:10 PM   #9
sapito is offline sapito
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I don't know if I arrived in time, but I like this bandpass configuration.
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Old 9th September 2002, 08:08 PM   #10
Rarkov is offline Rarkov  England
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Hi,
You're never too late to join in a conversation...Especially when I started it and like as much input as possible!

Can you tell me why you like that design? It looks like a design in LspCAD Bandpass 4 with the middle compartment missing.
What are it's features?

Thanks
Gaz
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