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Old 26th March 2007, 05:15 AM   #111
GM is offline GM  United States
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Quote:
Originally posted by rick57
........if a vented box is tuned to eg 40 Hz but crossed one octave higher at 80 Hz, the transient response diffrence will be minimal.

I haven’t heard of 1/2 horn before, are they suitable for 80 – 350 Hz??

I thought OB was something like a Q of 0.7??
Greets!

If you use a digital XO, then how far above Fb you need to XO is slope order dependent.

Half horns or similar give you 'slam' at the expense of BW and while their impulse response are more resonant than a typical alignment, they're no worse than a typical horn's, which folks perceive as highly damped. If the driver is good to 350 Hz, then so is the half horn.

OB's roll off at 6 dB/octave, then at 18 dB/octave below Fs, so this will negate some/all of the SET's effect on increasing the driver's Qts, so yes, a driver's effective Qts can be lowered with an OB.

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Old 26th March 2007, 05:39 AM   #112
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Greets!

I don't see how a half/hit/whatever short horn is going to control as well as a BP. You're right, most BLHs are highly compromised designs.

It's been a long time since I dinked around with Hornresp, but in the HELP menu it tells you how to input a BLH, ergo any standard vented alignment can be done.

Getting a K to go lower and/or cover a wider BW is no different than any other BP, so the driver's specs will be key, and of course it will need to be bigger to go low.

One more time, 'high mass' doesn't by default mean rolled off mids, highs, it depends on the driver's construction and its inductance. That said, as a general rule, a manufacturer uses mass to help control a driver's break-up modes, so in this case it doesn't go as high, all else being equal. Bottom line, use the appropriate 'tool' (driver) for the job.

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Old 26th March 2007, 07:25 AM   #113
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Hi GM

> WRT to reflex alignments, their SQ is dependent on many variables and to be sure, few vintage and current ones are even remotely high SQ IMO, so again, using a 'broad stroke' to imply they all are too fundamentally flawed to perform well doesn't work for me.

If you were responding to me, no I don’t think reflex alignments are fundamentally flawed, just wondered if their may be better way (“good> better > best”) to optimise for fast transients & fast decay, than the normal use of sims & tuning
I share your reservations about Ks, but was intrigued by your comment
> You'll probably have to OB them to get the transients 'tight'.

Anything you could add on OBs?

Thanks Again
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Old 26th March 2007, 03:26 PM   #114
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Hi GM

(For some reason your posts hadn't come though to here when I last posted). You have some interesting perspectives and good logic.

> If you use a digital XO, then how far above Fb you need to XO is slope order dependent.
Wouldn't that also apply to passive XOs?

> Half horns or similar give you 'slam' at the expense of BW . . and while their impulse response are more resonant than a typical alignment, they're no worse than a typical horn's
Do half horns have a similar drawback to Karlsons - they can't be ~accurately simmed; how close is it to a back loaded conical?

The Fmh of a JBL 2035 is 267 Hz. I also have some JBL 2202's, which were destined for midbass horns before available build time killed it.
With Qes of only 0.17 their Fmh is about double - 588 Hz, but with Vas of 128 litres/ 4 5 cubic feet, would they work ok in a half horn?

> and while their impulse response are more resonant than a typical alignment
You are saying for impulse response, that the 'pecking order' is sealed eg Q = 0.7, typical vented, then half horns; but that many people don't hear a (significant) difference?

>OB's roll off at 6 dB/octave, then at 18 dB/octave below Fs, so this will negate some/all of the SET's effect on increasing the driver's Qts, so yes, a driver's effective Qts can be lowered with an OB.
With sealed & vented, I thought the steeper the rolloff, the less ideal (rapid) the impulse response. Amp aside, are you suggesting that mounting a driver in an OB somehow lowers Qts, and improves impulse response?

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Old 26th March 2007, 03:26 PM   #115
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hey guys - regarding mass and what can afford - seems like going to 125-140g B&C costs about 5-6dB in the midrange plus add another 3 for K for total loss of around 3-8 depending upon POV. A leaner balance K might be good - if that's possible with same or more LF --- some of their tone seems to do with vent placement - I think - like central vent K15 style having a diferent sound than side-gapped.

a K going a couple notes lower than K15 might be fun as an experiment - which woofer type? - when I tried 295-070 EM-Dayton in somewhat lower tuned K15 - didn't seem optimal.

what does height of a K's front pipe have to do with its lumped front tuning? (assuming tuning can be lujmped below a point to figure out steady-state response) - CN is emphactic about raising coupler-height. If this has some bearing, how should the front chamber be set aspect-wise vs Sd for most efficient use of bulk and least amount of interference dips on the plot? (I almost concur withi CN that transients can sneak past dips)

B&C 15PZB even if went "aperiodic" might not sound tight since it sounds "thick" running 2-way in reflex or with reflex port stuffed. (might be my old haring -lol) IIRC 15TRX (with its shorting rings) might sound a "tiny" bit different than 15PZB (?) - they model ~same

what kind of OB setup might mate to TH sub nice for a dynamic but affordable system with good midrange? (got 12" coax and 21" woofer as toy)

JBL M151-8 vs B&C 15TRXB - theres a tiny bit of room for voicing by narrowing the gap to rear wall
Click the image to open in full size.

btw--Don Bunce's T-H style sub looks good and driver available. How does that kluge in Hornresp?
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Old 26th March 2007, 04:49 PM   #116
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I have not posted here but have been reading all the posts. I really like the size, ease, and claimed sound of this sub. it seems that this might fit into the normal basement rafter system. I don't have a basement in this house but the house we are moving to has one. I'll have to take the measurements for the rafters. The normal rafter is 16" on center so that means inside to inside is 14 1/4 " wide, then the rafters would have to be extended down to get the deeper dimentions. So that means the slat board would be horizontal. The mouth would face up into the room where the rest of the system resides. Does this sound like I am babbling? Cheers.
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Old 26th March 2007, 08:28 PM   #117
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Here is a picture from a site that Freddiy turned me on to. Of course you would change position of the driver and add the baffle board or middle plate or whatever you want to call it. Cheers.

Click the image to open in full size.
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Old 26th March 2007, 09:58 PM   #118
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hey Don - how low is excursion and mouth air velocity on your TH when its doin' some work?
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Old 27th March 2007, 12:30 AM   #119
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Freddy,

I see you pulled your posts from the hi eff forum...sorry for the delay,had
to work today.

The TH doesn't put out the shock wave that the LAB does,but it fills the room with bass....weird...

Playing Bela Fleck's Flight of the Cosmic Hippo at 120 db peaks on the Radio Shack meter at the mouth,excursion is very low...maybe a mm or two.(I should have worn ear plugs...feels like I'm under water right now)I thought it would be a lot higher than that.

Freq measurements are all over the place depending on mic placement,will have to take it outside to measure.has a big peak at 200 hz in my room.

DJN,

I made the internal width 14",the driver is 12.25" dia,so you could make the width 12.5",so the external width would be 14",should slip right in between the floor joists.

You could mount it vertically,with just the top 12" sticking out...would freak people out to see such a small box put out so much sound! you don't have to tell them the rest of it is basement.!hehehe...

I'm planning to build another one soon (hooked on stereo bass),will make it 14" outside dim to see how it works,would be much more convenient for mounting in floors,walls,or ceilings.Will let you know how it works out.
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Old 27th March 2007, 01:43 AM   #120
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Hi Don, does changing the dimentions so much change the sound a lot? Would you consider these more musical or more HT?
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