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Re: 7 Pi treble edge! [message #60359 is a reply to message #59326] Thu, 09 July 2009 13:29 Go to previous messageGo to previous message
Russellc is currently offline  Russellc
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Registered: May 2009
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PaulW wrote on Mon, 01 June 2009 19:13
Having built the 7's and enjoyed the results enormously but (there's always a 'but' isn't there?) for one issue, those in room bass modes causing poor, indistinct and boomy bass at certain frequencies. I tried Wayne's multi-sub approach by borrowing a few subs (3) to go with mine and I have to say it was very good. However, I really couldn't stand the extra cable runs and number of cabinets, plus the owners wanted their sub's back. So I then went down the passive route with a box resonator, followed by foam traps in all the corners against the ceiling. Then added one behind each mid unit, sitting on top of the bass cabs. The result was very good, delivering fast, articulate, integrated and musical bass, unfortunately (yes, another one of those 'buts'!) over the last few weeks I become more dissatisfied with the treble performance. This is mostly seems to show up in the upper vocal region, alto sax and plucked strings (though not on bowed violins strangely).

So, the question is, is this a room reflection problem that has been unmasked by the eradication of the previous bass issue? The room is small for these speakers at just under 200 square foot. I'm seated about (head position) 11 feet from the front of the speakers & their corner placement gives them a crossover point about 3 feet in front of me. The surfaces in the room which do not have anything to break-up/absorb treble are the ceiling and wall between the speakers. It's always difficult to describe the quality of a sound, but words like edgy, hard, beaming and resonant all seem to apply here.

Now I did mention this in an earlier post, where I stated that as the bass was improved, the treble seemed to worsen and pointed the finger at the B&C DE250, but as Wayne considers this to be

"..... one of the smoothest compression drivers I've ever heard or measured. For that matter, it's one of the smoothest tweeters of any type I've measured. It doesn't reach beyond 18kHz, but up to that point, it is smooth as silk. A DE250 on an H290 or a π wood horn is as good as it gets, in my opinion...."

I feel I either have to look at the room or perhaps some of the amplification, which is all basic Bottlehead stuff (Seduction, Foreplay and Paramours) but this is also not know for treble problems, based on what I've read on their forum, usually the opposite. Front end? Well I mostly listen to LP's and the turntable is set-up correctly and the cartridge used is a newish Denon DL304 which is considered very 'sweet' in the treble region, so I feel I'm back to looking at the room!

Any thoughts would be most welcome.

PaulW




I will agree on the "Smoothest part" but disagree as to the right out of the box part. Right out of the box, mine sounded like a cutting torch was going through your head unless I used an L-pad to severly reduce the output.

After a few weeks of play, I noticed I was slowly turning them up, until I was basically at the same place I was when the Selenium 220 Ti was installed. The Selenium sounds dry and fuzzy in comparison. Its a great driver, you can read of mine and others exploits with it over on AK with the E'wave thread.

I'm using the B&C DE 250 on top of a JBL 4507 box tuned to either 34 hz or about 30 hz depending on mood. The 5 cu ft 4507 box is currently loaded with JBL 2235H, and have also tried a pair of 2225H as well.

The B&C DE250 sounds way more clear and revealing than the Selenium 220 ti. Not to take anything away from this inexpensive driver, its amazing for the price, but the B&C DE 250 sounds a whole lot better, no small improvement. The selenium is very enjoyable in that project, the crossovers compensation is spot on. But with the B&C, another level is achieved. Clarity is much improved, truely an impressive driver, I would suggest run in time will cure your problem.

russellc

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