So I built a few years ago a pair of speakers based on Dynaco's A25, using the SEAS A26RE4 as midrange woofers and 27TBFC/G as tweeters.
I didn't want to spent the extra $$$ for the T35 and couldn't see the advantage of these tweeters, if they had to be padded by an 10 Ohm resistor anyway.
And from what I understood larger tweeters were more directionnal.
The 27TBFC/G has the advantage of going easily down to 1500Hz and has very little distortion. Its efficiency is on par with the A26RE4 woofer. It is also quite cheap. Finally they have protection grids and I was just going to have a children ;-)
I will make new pictures of my speakers to see the build. At that time I presented it in the A26 thread but these pictures are not hosted anymore. I have to say I'm really proud of the wood work that I've done (with some help) !
here is a picture of the cabinets while I was building it :
Now I'm just thinking again about the filter part.
I was really happy with the result and therefore didn't want to spend hours working on the filter, now I consider that maybe there is something that can be improved there.
I started playing a bit with XSim, using datas for my speakers to see how they compare with the stock A26 kit.
I found out that one can achieve a very close match, side apart from the impedance (which stays anyway above 6 Ohms):
In light blue, the commercial kit with T35, in dark blue with the 27TBFC/G:
But actually in my original design I used a 4.7uF Mundorf Supreme Cap in series with a 9.5 Ohms resistor on the tweeter (still no filtering on the A26RE4).
What is strange is that the frequency response is very far away from linear :
Though to my ears it is very well balanced.
What do I miss?
I didn't want to spent the extra $$$ for the T35 and couldn't see the advantage of these tweeters, if they had to be padded by an 10 Ohm resistor anyway.
And from what I understood larger tweeters were more directionnal.
The 27TBFC/G has the advantage of going easily down to 1500Hz and has very little distortion. Its efficiency is on par with the A26RE4 woofer. It is also quite cheap. Finally they have protection grids and I was just going to have a children ;-)
I will make new pictures of my speakers to see the build. At that time I presented it in the A26 thread but these pictures are not hosted anymore. I have to say I'm really proud of the wood work that I've done (with some help) !
here is a picture of the cabinets while I was building it :
An externally hosted image should be here but it was not working when we last tested it.
Now I'm just thinking again about the filter part.
I was really happy with the result and therefore didn't want to spend hours working on the filter, now I consider that maybe there is something that can be improved there.
I started playing a bit with XSim, using datas for my speakers to see how they compare with the stock A26 kit.
I found out that one can achieve a very close match, side apart from the impedance (which stays anyway above 6 Ohms):
In light blue, the commercial kit with T35, in dark blue with the 27TBFC/G:
An externally hosted image should be here but it was not working when we last tested it.
But actually in my original design I used a 4.7uF Mundorf Supreme Cap in series with a 9.5 Ohms resistor on the tweeter (still no filtering on the A26RE4).
What is strange is that the frequency response is very far away from linear :
An externally hosted image should be here but it was not working when we last tested it.
Though to my ears it is very well balanced.
What do I miss?
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How do you check phase shift? As you can see from the picture I placed the tweeters off-center to reduce the delay between the sound emission by the tweeter and the woofer (you see above the right speakers).
Phase correction!
Ok so I meanwhile understood the point of phase shifting.
Just modified the filter taking into account this aspect.
It now presents a perfect phase match at 1.8 kHz thanks to the inductor!
The filter now uses a 5.6uF cap, a 2.2 Ohms resistor and a 0.39mH inductor (with 510 mOhms ESR).
The frequency response is even better than the kit with the T35 (below in light gray in comparaison with the build with 27TBFCG in black): more mid ranges, between 400 Hz and 1300 Hz - though high frequencies above 18 000 Hz are reduced.
Impedance is reduced but still above 4 Ohms:
I am about to order new components ;-)
Ok so I meanwhile understood the point of phase shifting.
Just modified the filter taking into account this aspect.
It now presents a perfect phase match at 1.8 kHz thanks to the inductor!
The filter now uses a 5.6uF cap, a 2.2 Ohms resistor and a 0.39mH inductor (with 510 mOhms ESR).
An externally hosted image should be here but it was not working when we last tested it.
The frequency response is even better than the kit with the T35 (below in light gray in comparaison with the build with 27TBFCG in black): more mid ranges, between 400 Hz and 1300 Hz - though high frequencies above 18 000 Hz are reduced.
An externally hosted image should be here but it was not working when we last tested it.
Impedance is reduced but still above 4 Ohms:
An externally hosted image should be here but it was not working when we last tested it.
I am about to order new components ;-)
I am very interested in the A26 concept, especially using the woofer fullrange. Looking into tweeter choices, I just happen to have 3 pairs of Mark Audio's Alpair 10.3M.
Markaudio Alpair-10 Gold 6" Full Range Gen 3
The 10.3M certain can handle the lows in the context of functioning as a tweeter. It appears to be on the inefficient side, but I generally prefer a warner sound anyway.
I am however not an expert of modeling crossovers. What would be the cap and inductor values if I want to pair these Alpairs with the A26RE4 (running full range)? Thanks!
Markaudio Alpair-10 Gold 6" Full Range Gen 3
The 10.3M certain can handle the lows in the context of functioning as a tweeter. It appears to be on the inefficient side, but I generally prefer a warner sound anyway.
I am however not an expert of modeling crossovers. What would be the cap and inductor values if I want to pair these Alpairs with the A26RE4 (running full range)? Thanks!
3 pr, you lucky guy.
With the A26 and the A10.3 you first have to choose an XO point. Where that is depends on box, taste, how loud you want to play etc. I would cross low (circa 250 Hz) down where a passive XO becomes much harder (and often pricier) than active as one is dealing with part sof the speaker impedance near the large resonance peaks in each driver. Waxx has done a passive XO with A10.3 (different woofer), i am just drawing that project up, it would give you an idea (IIRC he has pushed the XO up to ~350 Hz).
With 4 set of A10.3 i have a scheme for all of them in a single box, but one would need an amp that is happy fdriving a nomal 20-24Ω load. Should move close to as much air as the A26, XO is much, much simplier and driver voicing match is perfect.
dave
PS: despite what they are called the drivers are copper coloured and 5.25”
With the A26 and the A10.3 you first have to choose an XO point. Where that is depends on box, taste, how loud you want to play etc. I would cross low (circa 250 Hz) down where a passive XO becomes much harder (and often pricier) than active as one is dealing with part sof the speaker impedance near the large resonance peaks in each driver. Waxx has done a passive XO with A10.3 (different woofer), i am just drawing that project up, it would give you an idea (IIRC he has pushed the XO up to ~350 Hz).
With 4 set of A10.3 i have a scheme for all of them in a single box, but one would need an amp that is happy fdriving a nomal 20-24Ω load. Should move close to as much air as the A26, XO is much, much simplier and driver voicing match is perfect.
dave
PS: despite what they are called the drivers are copper coloured and 5.25”
Thank you. With the Seas/Alpair setup, I do want to just run the Seas full range, which would mean having the high-pass filter for the Alpair at around 1500hz? I.e., using the Alpair just as a large tweeter.
I am also intrigued by your 4xAlpair scheme -- I may just need to get another pair then. How large would the box be? I am kind of fixed on having the volume at around 3 cubic feet/85L, as I have a pair of donor boxes. It appears that the Seas will be fine running full range in a sealed 85L.
I am also intrigued by your 4xAlpair scheme -- I may just need to get another pair then. How large would the box be? I am kind of fixed on having the volume at around 3 cubic feet/85L, as I have a pair of donor boxes. It appears that the Seas will be fine running full range in a sealed 85L.
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Why? The Alpair has (much) better mid/top, a high XO is not something i would even consider given all the advantages of jkeeoing it low, but if you want to try you will need to XO something like 1-1.5kHz. A box would possibly not be required.
dave
dave
Only to pay respect to Seas' A26 concept of running its 10" woofer full range. I myself never heard of the A25, so I always wondered how such a setup would sound like. Since I have the 10.3M, I thought I might just use it as a tweeter. That's all.
But I agree that the well-designed Alpair 10.3M are superb. My only complaint was that it did not move enough air to truly have that weighty orchestral reproduction, having just built and enjoyed a pair of Audio Nirvana Super 15 Ferrites in 12 cubic-feet vented boxes (with certain modification to tame the 15's lower upper range so that they are no longer shouty). I tried my best to help the Alpairs to move air at the time, even going as far as using a a pair of Snell's SUB1800 (18" woofers solidly reaching 15hz) powered separately to supplement the low end.
But 4x10.3M in a box may just do. I am intrigued! But let me not hijack this thread further.
If you are interested in potential multi-Alpair designs, email me. 4 is a different challenge than 2 or 3.
The AN has about 800 cm2 vrs 3 x A10.3 of 260 2 but more xmas. 8 cLitres to 20 cLitres is estimated volume displacement so the A10s can move more air.
Box for the A10.3 probably as large as the AN box, because it would need to be a horn or TL to get the LF extension.
dave
The AN has about 800 cm2 vrs 3 x A10.3 of 260 2 but more xmas. 8 cLitres to 20 cLitres is estimated volume displacement so the A10s can move more air.
Box for the A10.3 probably as large as the AN box, because it would need to be a horn or TL to get the LF extension.
dave