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Old 30th November 2012, 02:43 PM   #31
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by murphythecat8 View Post
can you elaborate a bit about the 250 hertz cross over.
Im planning on crossing my FR at 300 hz, but you seem to think its not ideal...
I can report two cases.
First, XO at 380hz, biamping was very critical and I dont want to go that high ever. (they were commercial speakers).
Second, XO at 300hz. My current speakers have this, which i raised after initial 250hz due to lack of dynamics otherwise. The XO has a very high steep (it's done in digital with serious software). Here the amp matching is much better but still far from perfect. For instance, I get a more uniform timbre and rhythm if I use similar amplifiers, it is not smooth when using for instance a class AB and a SE-class A.

For these new speakers, I want less compromises in this matter, because I know for sure that I will biamp low and MT section, and that I like amp rolling.
The voice range starts at 200hz* and finish at 4khz. (*some male fundamentals are even lower) As you read from my first post, a suitable driver which is also highly efficient (which i require to use class A amplification) is very hard to find. If you dont care as much for efficiency, but want a wideband to push XO boundaries out of the voice range, go for a Volt as midrange, they are the smoothest. Of if space/budget permits an array of 4-6 per side
I see, you are using a fullrange, well, think about adding a midwoofer as third way (300 down to 100 maybe). I decided against a FR, and I dont want to go 4-way (read my post about the ATC midrange), but maybe you can. Scan-speak, Seas, Volt... there are many good midbass units around 90db efficiency, or higher (PHL).

BUT if you dont plan to biamp your speakers, it doesnt really matter, you can do even 800hz XO and you wont notice the transition if it's tuned well. (You will notice if the loading is different though, like sealed box + OB top) Most commercial speakers are not meant to be multiamped and when they are, the predefined amplifiers have similar technology and timbre (i.e. Linn, Naim), or they are active (ATC, PMC...).
Hope this helps.
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Old 30th November 2012, 03:08 PM   #32
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B&C 6MD38-8? Zaph has this tested and reported on his site.
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Old 30th November 2012, 03:20 PM   #33
Telstar is offline Telstar  Italy
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Quote:
Originally Posted by 454Casull View Post
B&C 6MD38-8? Zaph has this tested and reported on his site.
Not bad, better than the 6" beymas I have in list (and that now gets scraped).
Not powerful enough for 250hz XO, though.

Of the two compromises (crossing higher in the low-range or crossing lower in the upper range), i definitely prefer the second option, so i'm more inclined in getting a (pair of) midwoofer than a pure 6" mid.
Finding one in smaller size than 8" is very hard, though. Physics cant be cheated

Finished checking B&C catalogue. They have a nice 8" midwoofer:
B&C 8PE21
and their graph seem to match with Zaph measurements, so this one has the capabilities to play well down to 250hz, with a little active padding. It's FR is quite similar to the Jantzen 8008.
I'd like to see a CSD, though.
Attached Files
File Type: pdf B&C 8pe21.pdf (57.7 KB, 24 views)
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Last edited by Telstar; 30th November 2012 at 03:47 PM. Reason: added 8" B&C driver
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Old 30th November 2012, 03:48 PM   #34
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attached measurements for the 8PE21 that i found on this very forum
250hz -3khz seem a good range for it.
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Old 30th November 2012, 04:46 PM   #35
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Why would you want to run an 8" up to 4 kHz?
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Old 30th November 2012, 05:00 PM   #36
Telstar is offline Telstar  Italy
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Read post #31.
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Old 1st December 2012, 09:38 AM   #37
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Quote:
Originally Posted by Telstar View Post
Read post #31.
Only answers half the question.
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Old 1st December 2012, 10:25 AM   #38
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Little update on PHL drivers.
While i could not find FR of all current models, it appears that the midbass ones have depressed LF reproduction, which is not acceptable for me.
Instead the extended midrange 6,5" such as 1120/1130 is pretty smooth (see attached test results) and most importantly has been used cut at 250hz with only 1st order, although the upper range will require more shelving.

Two 1130 in parallel I think that could be cut at 200hz whithout sacrifying SPL too much, which is ideal for me.
Moreover they are much cheaper than the Supravox 165gmf (140 vs 240).
This road seems more satisfying than the single 8" because will allow me to try a MTM configuration and reduce beaming.

I'm still looking for data of other 6,5" PHL models, in particular of the 1060/1070 (which should be more extended in the HF) and 1660/1670 (which should have stronger bass).
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File Type: jpg KT_Test_phl-E17-1120.jpg (494.7 KB, 230 views)
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Old 1st December 2012, 01:00 PM   #39
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Your constraints drive you to build speakers that inherently require you to build more speakers.

Large light diaphragms prone to beaming and break up modes, and selecting bandwidth based on what a human voice does instead of what the driver can do without beaming, or breaking up.

You mention steep slopes and "serious software" in #31, and then 1st order in #38.

Whole point of multi-way speakers is to get away from deficiencies of lightweight drivers necessitated by premiums for power amplifiers fifty years ago. And likewise DSP allows techniques to improve upon limitations of analog filters.

What do you use for speaker measurements?

Does Tempest have references to bone conduction studies? I've looked and don't see much. His approach to assessing bandwidth of hearing perception is bone headed. It is obvious from ability to discern location and movement of broadband sources in the forward direction, where timing changes of 5 microsecond in path length cause perceptual change. The inverse of 5 microseconds, 200kHz is not present, or detected in perceptual process. Hair cells on bassilar membrane fire at zero crossing of membrane from its rest position in one direction only(corelated with negative going pressure). Parellel neural networking builds phase descriminator.

Regards,

Andrew
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Old 1st December 2012, 01:35 PM   #40
Telstar is offline Telstar  Italy
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Digital xo (by means of izotope Ozone) was used in my last speakers but i cannot do it in these because of WAF limitation, the only thing I can do is a low pass and highpass between woofer and MT with an active electronic xo such as Marchand.
Said that, I have been satisfied by passive multi-way speakers, so I do not have a prejudice on this matter.

The HF must be powered by a class a push-pull, no matter what you or others think of the improvements in amplifier technology. No class AB amp that I know of sounds good in the top end. If I can limit its power, the better, as I don't want to build a 100kg brick (but I have listened to one which sounded great). And don't even suggest pwm.

I build speakers that follow MY tastes, this is a DIY audio forum, isn't it?
Otherwise there are hundreds of designs I could replicate, 99% made more or less the same. Then there are fullrange monodrivers with or without reinforcement. BDDT.

Ofc I want to use the various drivers in their best range. But I want to employ them in a design that suits my needs and tastes.
I can end with a 2khz xo like Tony Gee did in a big 4-way, or maybe higher. I do not know until i have the drivers in my hands. but I'd like the midrange speakers be able to reproduce the full voice spectrum, that's all.
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