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Old 15th October 2008, 08:08 PM   #1
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Default Question regarding speaker selection and sensitivity

Hello all,

I am newly registered on DiyAudio, but I have spent many an hour reading and searching. Thanks to all the experienced individuals here that make life easier.

Now to my question. I am looking to build a set of speakers for my current system. In the past I have built tube guitar amps, a tube DAC, a small solid state amp and a set of Andromeda DIY speakers. I used the Andromeda speakers with my Macintosh MC602 and they sounded great. I have since sold my MC602 and gave my brother the Andromeda speakers to use.

My current system uses a pair of custom made Tube driven monoblocks that have a 805 driver tube and a 300B with 2X 12au7's each, they are estimated at about 40-60 watts based on the tube compliment. I have an Audio Note pre-amp and analog and digital front ends. I am currently using a smallish set of B&W 603's and they sound ok. This is where I want to start.

I want to design a solid 3-way speaker system that has a 10 - 13 inch sub / woofer?? and a 7 - 8 inch mid driver and a tweeter. This is not set in stone as I am unsure of how to optimize the speaker selection. I want to ensure that I have a sensitive enough speaker for the tube mono's. I am currently researching Xover designs and feel I understand the concepts fairly well. I am willing to put as much effort as needed to get the Xover's right on. I am also planning on a speaker cabinet that is something like 50" H X 12" W X 26" L, so it will be tall, thin and deep. I am also planning on making the sides curved inwards towards the back using a jig I made.

What I have:
I have excellent cabinet making and furniture making skills as well as all the woodworking machinery needed so I am set in that respect. I also have plenty of electronics parts, scopes, meters and tools, plus some electronics DIY experience.

What I need:
Pointed in the right direction to build some knowledge on Speaker selection, sensitivity and Xover design tips. I have read plenty on the subject, just need to build on that.

What I want to end up with:
A great sounding speaker that works well with the tube mono's I have. I will take care of the aesthetics of the cabinets.

Thanks for reading a long winded post, I just wanted to make sure I framed everything correctly.

Pat
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Old 15th October 2008, 09:10 PM   #2
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You might be better off posting this in the main loudspeakers section, as this part of the forum is dedicated to full / wide range drivers.

Remember that tall & thin will not automatically perform as expected if you design as a BR.

As for the rest -depends on what you want. 'Great sounding' isn't much to go on, given that everyone has different ideas about what such a thing is, and what is divine to one may be the antichrist to someone else. You're not giving us any idea of budget either. I suggest you take a look at Zaph's & Troel Gravesen's sites for inspiration WRT 3 way designs, driver choices etc. Troel's DTQWT (actually a horn) might be of interest: http://www.troelsgravesen.dk/JA8008_DTQWT.htm

FWIW, one piece of general advice I almost always give: go for efficiency. The higher the better (providing you're not sacrificing too much elsewhere in order to achieve it, which should not be the case if you select & use quality drive units).
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Old 18th October 2008, 01:19 AM   #3
elac310 is offline elac310  France
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A big, high efficiency, 3 way system is tricky to design without measuring equipment. OK for the enclosure etc. but when it comes to the crossover adjustment...

Here is a proposal, for one channel:

BASS: up to 300Hz: 2x15"woofers Ciare PW388 or 15.64 (it's the same speaker, just two different references); they have a low resonnant frequency and will require 200Liters of net volume each=400L net per channel, with bass reflex enclosure, vent: 7" diameter, 7" length '1 vent for each woofer or two for a common enclosure); they have a low moving mass of 75g and extremely low mechanical resistance=high spl and good resolution - for a 15" at least - even at low volume)
MID: 300Hz to 3000Hz; 2x Audax HM210Z10 ; only one place in the world where they are still available since they're out of production, unfortunately: http://www.audax-speaker.de/?lang=en ; excellent mid-way speaker, low moving mass despite high tech coating to avoid resonances, very smooth but high resolution. Similar mids are available under other brands.
TREBBLE: 3000Hz to above 20,000Hz: 1 x Beyma TPL150: Air motion tweeter, high resolution, high spl, smooth and neutral, good resolution also at low spl.

Crossover: I've spent two years to fine tune the crossover based on listening tests and all types of music, using many possibilities and changing often the setting from complex to simpler, and back to complex designs.
I finally prefered the simple approach (!!) despite the size of the system and the number of speakers:
BASS (polarity reversed): 12dB slope: 5mH serial +200uF parallel
MID: 6+6dB slope: 50uF serial +1,4mH serial
TREBBLE (3 inches deeper than MIDs):6dB slope: 8,2uF serial;
I managed to get an excellent tonal balance at the listening place at 5meters (17 feet) without any resistor: full spl available !
Overall sensitivity is betwen 100 and 105dB.


Works fine with high power mosfet amp, chipamp LM3886, tube amps (including PP EL34, SE 805), but I have not tried with low power SE triode amps (my SE805 deliver 40W/ch). Could be difficult for SE300B or 845 to drive such large speakers without impedance "linearization".
Another challenge was to get 4 such woofers working in my listening room. You should expect some boomy resonances depending on room proportions and if no acoustic treatment. I coped with this by just adding a couple of sofas to break stationary bass-waves. The bass level can be adjusted my moving the listening sofa closer back to the wall (closer= louder), but 3 to 4 feet away is best.
I use sigle enclosures placed at 1foot1/2 above ground to get the most articulate bass.

Good luck!
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Old 18th October 2008, 05:46 AM   #4
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Default Re: Question regarding speaker selection and sensitivity

Quote:
Originally posted by NorCalAudio
monoblocks that have a 805 driver tube and a 300B with 2X 12au7's each, they are estimated at about 40-60 watts based on the tube compliment.
You mean an 805SE amp with a 300B driver and 12AU7 front end?

SE amps tend not to like xrossovers, but that would be a nice amp for driving a "midrange" from ~100 Hz to 10k.

dave

PS: i've moved this thread to Loudspeakers, the Full-range forum is not a place to be talking too much about XOs.

dave
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Old 18th October 2008, 05:49 AM   #5
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Quote:
Originally posted by Scottmoose

Troel's DTQWT (actually a horn) might be of interest: http://www.troelsgravesen.dk/JA8008_DTQWT.htm
It is interst that the plans specify MDF, but he (properly) builds it out of plywood

dave
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Old 18th October 2008, 04:40 PM   #6
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Quote:
Originally posted by elac310
Could be difficult for SE300B or 845 to drive such large speakers without impedance "linearization".
Thanks for the response. After looking at all the DIY speakers designs that Google found, plus all the ones referenced on this forum I have rethought the design somewhat. I am considering a 2 way design.

I am pouring over speaker specs at the moment trying to determine what I should be looking for spec wise to insure I am designing a loudspeaker that is sensitive enough and has enough range with respect towards reproducing deep bass and mellow highs. I know, it sounds like I want everything....

I listen to pretty much every style of music, but I don't need huge amounts of bass. I just don't want a thin sounding experience.

Specwise what are the most important aspects of a speaker (driver, tweeter, woofer) that one should pay attention to? I am currently looking at sensitivity, power handling in Watts, freq response and construction. I would like to develop a sense of classification according to what works best for a SET amp, or a high current solid state.

As for the crossovers. I know that I will not get it right for a while. I plan on making the crossover easy to modify and change by keeping it mounted outside the inner enclosure using a built in enclosure that I can access from the rear of the speaker where the speaker wiring will connect to the speaker cables. I am actually looking forward to this as I know hands on experience will teach me more about crossover designs than reading. Also what is the common consensus regarding the use of L-Pads to control mids and highs?

In summary right now I am trying to hammer out and decide on driver selection. From there I plan on putting a few cabinet design together based on the drivers and then using software I will try my hand at crossovers. I will also probably use software to get a few cabinet dimensions.

Thanks to everyone for reading and commenting on my rudimentary questions. Also thanks "planet10" for moving this to the proper forum.
...Looking forward to more comments and learning.

Pat
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Old 18th October 2008, 07:40 PM   #7
Helmuth is offline Helmuth  Netherlands
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Default Re: Question regarding speaker selection and sensitivity

Quote:
Originally posted by NorCalAudio
Hello all,


My current system uses a pair of custom made Tube driven monoblocks that have a 805 driver tube and a 300B with 2X 12au7's each, they are estimated at about 40-60 watts based on the tube compliment. I have an Audio Note pre-amp and analog and digital front ends. I am currently using a smallish set of B&W 603's and they sound ok. This is where I want to start.

What I need:
Pointed in the right direction to build some knowledge on Speaker selection, sensitivity and Xover design tips. I have read plenty on the subject, just need to build on that.

What I want to end up with:
A great sounding speaker that works well with the tube mono's I have. I will take care of the aesthetics of the cabinets.

Thanks for reading a long winded post, I just wanted to make sure I framed everything correctly.

Pat
Hi Pat,

I am thinking a lot for building high spl spaekers.

Look on the fostex site


fostex enclosures

A quick idea of Helmuth for 98dB 1W/mtr 33Hz - 40khz (high end)

Use two of beyma 12br70 parallel.
Click the image to open in full size.
beyma Click the image to open in full size.

And with 18db/oct from 1khz this one neopro5i
Click the image to open in full size.

This shout make high qaulity high spl possible 2 way.

3 way use this mid beyma

and this ribbon neocd2.0mb
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Old 18th October 2008, 07:50 PM   #8
Helmuth is offline Helmuth  Netherlands
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Plot 12br70 pink line 6th order ventilated bandpass 95.5dB 1W/mtr white br enclosure 93dB 1W/mtr.

Vented bandpass is great for 3 way.
Attached Images
File Type: jpg beyma 12br70.jpg (81.1 KB, 474 views)
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Old 18th October 2008, 09:37 PM   #9
Helmuth is offline Helmuth  Netherlands
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I thought of a better choice for the 12br70. The sph275c will perform better within midrange due carbon cone.

http://www.monacor.de/typo3/index.ph...5&spr=DE&typ=u

Click the image to open in full size.

Two parallel should make about 95dB 1 W/mtr with the neocd2 84liter box!!Cost about 2X130 euro + 103 euro= 363 drivers.
Attached Images
File Type: jpg sph275c.jpg (98.4 KB, 314 views)
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Old 19th October 2008, 07:50 AM   #10
Helmuth is offline Helmuth  Netherlands
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Hi

And use a passive radiator of seas or peerles and not a pipe.
Click the image to open in full size.

seas
peerless

Here a new plot a box with 2x sph275 see max SPL! -3db 43Hz, -8db 35Hz
Attached Images
File Type: jpg sph275c 2.jpg (63.1 KB, 300 views)
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