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Multi-Way Conventional loudspeakers with crossovers

Troels Gravesen high efficiency 3-way looks like a winner.
Troels Gravesen high efficiency 3-way looks like a winner.
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Old 27th January 2020, 05:21 PM   #11
cph2000 is offline cph2000  Denmark
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Well I’m intrigued by the driver selection, Tony over at Humble Homemade Hifi has a similar concept cooking claiming exceptional results.
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Old 27th January 2020, 05:27 PM   #12
Zuhl is offline Zuhl  England
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Quote:
I've always criticised Troels designs for their apparent lack of attention to BSC.
If you look at his measurements, all bass units have a large dip at 500 hz which is not apparent on anyone else's measurements. This leads him to use a smaller than normal inductor allied with a notch filter to flatten the mid.

What would then give a 500 hz lift in most rooms plus his infamous left to right slope, to me, would make the speakers difficult to listen to.
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Old 27th January 2020, 07:39 PM   #13
5th element is offline 5th element  United Kingdom
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Originally Posted by Jonhny View Post
I must have measured and developed close to a 100 speakers using the Clio now. BSC just isnt such a big deal.
I don't really see how a phenomenon caused by the law of physics isn't such a big deal. It's present in every stereotypical loudspeaker design in one way another and needs to be accounted for. Whether this means less or more of it needs compensating for depends on the design and intended application but to say it isn't such a big deal is very dismissive.

To me the final steps in balancing a loudspeakers tonal balance involve tuning the BSC and tweeter levels. If either are off by as little as 1dB it can make a design quite unpleasant to listen to. At least to my ears. Now I do have hyperacusis and that makes me more sensitive to speakers that are lacking. An overly forward sound, indicative of too little compensation, hurts to listen to.
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Old 27th January 2020, 08:18 PM   #14
Beatlejuiced is offline Beatlejuiced
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In regard to Mr. Gravesen not listing the values of his crossover components, I read some time ago on his site that pirates were using his designs and passing them off as their own, thus his reluctance to "give away the store".

In regard to the slight downward slope of the frequency response (from bass to treble) of many of his speakers, I believe this tendency is supported by evidence that this is what most listeners prefer on axis (I don't remember the researcher or the methodology; I think it was Floyd Toole; someone please correct me if you know otherwise).

In regard to off axis performance, he reports that the Faital 6RS140 that he uses for the midrange has "excellent dispersion". The factory measurements show a very flat response on axis from 500Hz to 8KHz. The driver diameter suggests a rolloff that begins at about 2800. The ScanSpeak D2608/913000 tweeter has an Fs of 700Hz, and the response is flat down to 2000Hz. I don't know the specific measurement conditions under which he tests his speakers, but I see no reason to doubt the off-axis performance when crossing over LR2 at 500Hz and 2400Hz.

In regard to BSC and bass extension, he has designed speakers to specifically address BSC with wide baffles (Poor Man's Strad) and at least one with a downward sloping bass response meant to be placed against the wall (8008-Corner), so he does take BSC and boundary reinforcement into consideration in his designs. Though I have not analyzed all his speakers, it appears that most of them are bass reflex and transmission line designs, and I speculate that he may adjust the tuning of the cabinets to give a bit of a boost at the low end.

In the case of the Faital 3MC, the baffle width is 375mm, which suggests baffle step of -3dB at 300Hz. We don't know the DCR of the woofer crossover coil, but if we assume it to be .5ohm, a not unreasonable figure, it increases the .qts value of the Faital 12PR320 bass driver to give an approximately 1dB lift to the FR from about 150Hz to 60Hz in this cabinet. F3 becomes about 47Hz and F6 about 41Hz. This is well within the range of tone controls on preamps and receivers. The Faital woofer can handle the low EQ boost; the factory specifications suggest it can produce 108dB at 41Hz in a bass reflex cabinet at one meter. Considering that 41.2 hz is the traditionally lowest note on a double bass and a bass guitar, this should be plenty of bass response for most kinds of music with the exception of the lowest organ tones. This is a speaker for music, not movie sound effects. In addition to all this, BSC in practice may not be a concern for most people in most listening environments; I believe most listeners will place their speakers in proximity to at least one wall. For those with very large spaces, they could supplement the bass with subwoofers, or, of course, buy a different speaker. No one speaker can be all things to all people.

It is not my intention to be an apologist or champion for Troels Gravesen, but I believe in giving credit where credit is due, and I think this speaker is remarkable for a beautifully harmonized balance of performance, simplicity, and cost. I repeat, I think it would be perfect for those that need high efficiency and also for beginners that want an excellent, easy-to-construct speaker that does not cost an arm and a leg.

Last edited by Beatlejuiced; 27th January 2020 at 08:33 PM.
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Old 27th January 2020, 08:53 PM   #15
afa is offline afa  Australia
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Reads like an ad
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Old 28th January 2020, 02:46 AM   #16
Bigun is offline Bigun  Canada
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Troels Gravesen high efficiency 3-way looks like a winner.
Quote:
Originally Posted by afa View Post
Reads like an ad
I think that’s unfair. It was a good response to the preceding criticisms, providing more balance to the discussion.

I’m quite intrigued by this design and am interested to read more of everyone’s thoughts - not least because I learn from those with much more knowkedge and experience than I have.

Troels, in my view, has earned some respect. He has explored many different approaches so he has dealt with, first hand, many examples of the tradeoffs all speaker designs require. I try to learn a little of the why’s and wherefore’s from his articles.

5th element, you are also very experienced. I’ve picked up a lot from your writings.

I like mostly to design and build amplifiers, both tube and solid state. A good speaker for testing amplifiers I build needs to be that strangest of beasts - a chameleon suited to low power tubes and high power transistors, i.e. to be sensitive and have good power handling. Not being a large and expensive or difficult-to-build project makes it a lot more accessible. This latest from Troels may be a candidate.

What tradeoffs did he make that you would do differently? and where the time, effort and cost would be justified by the resulting improvement.
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Last edited by Bigun; 28th January 2020 at 02:56 AM.
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Old 28th January 2020, 01:50 PM   #17
gwmorgan is offline gwmorgan  US Virgin Islands
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Originally Posted by afa View Post
Reads like an ad
All you guys that can do a better job should set up your own sites and offer some designs for people to build.I have built one of his designs and used it for years, no problems with bass and integration of drive units is as good as I have ever heard.
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Old 28th January 2020, 01:52 PM   #18
Beatlejuiced is offline Beatlejuiced
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It came to me that I should post a disclaimer for those with an interest in this speaker: I have never built or heard one of Mr. Gravesen's designs, so I can not testify as to the sound quality of any of his speakers. Based upon what I understand about speaker design, this looks like a good one.

I will not post any more in this thread because I sense that it may devolve into a litany of nitpicking and personal comments. To those that are interested in it, I can only say that every speaker design is compromised in some way, and I think this one is a well-judged combination of those compromises. I think it will sound great for most people with most kinds of music. Again, I am not in the market for new speakers, but I will be interested to see if anyone builds it and posts a review.
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Old 28th January 2020, 02:33 PM   #19
beardman is offline beardman  Denmark
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Beatlejuiced

i am sure this speaker you look at will sound really great,,,fine speaker unit,,i have heard several system from Troels,,,,and for now i use The Loudspeaker from him,,,best i ever had owned

measure is absolut not everything in a speaker ,,,

Best Bjarne
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Old 28th January 2020, 09:09 PM   #20
Bill poster is offline Bill poster  Thailand
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Dayton RS drivers are another good option for high sensitivity and 8 ohm rating. Ie RS225P-4 in series etc
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