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In Reply to: RE: "...why run a transmitter triode to get 8W...?" posted by Triode_Kingdom on May 25, 2025 at 18:44:01
For example both B&W 801 and ProAc response three can go down 20Hz but the room can't. So that 20Hz is useless. On the other hand, my JBL dual 15" can go down 30Hz but it has a lot of more output than the tiny woofers on the ProAc.
I believe your woofers are JBL 2226Gs. Their free air resonance is 40Hz. In ported, tuned boxes you would be doing well to have a -3db point of 50Hz.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Key Features:
u Usable Response to 35 Hz
u 100 dB Sensitivity, 1 W, 1 m
u 1200 Watts Power Capacity
u Two 380 mm (15 in) Low Frequency
Transducers
u Direct Radiator Ported Enclosure
"Usable Response to 35 Hz"I'm sure you realize this is a meaningless number. The term "usable" has no scientific meaning, especially when discussing the frequency response of speakers.
"100 dB Sensitivity, 1 W, 1 m
"1200 Watts Power Capacity"By virtue of the physics of voice coils, gaps and excursion, these two specifications are mutually exclusive when applied to a woofer. The high power capacity implies relatively low sensitivity of the low frequency driver, more than likely at least 10dB less than the sensitivity spec. The latter is undoubtedly confined to midrange frequencies and higher, which is one reason bi-amping of SETs is so common.
Edits: 05/26/25
Have you looked at their specs?
Edits: 05/26/25
.
Have Fun and Enjoy the Music
"Still Working the Problem"
If so, cool but you didn't say that.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Forget about EQ. The only place I used EQ is on B&W 801. They call it BAF (bass alignment filter).
are not usable to 35Hz. They are too quiet at 35Hz to add anything to the rest of the music.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 05/26/25
Can you give me an example?
!
The Mind has No Firewall~ U.S. Army War College.
.
Have Fun and Enjoy the Music
"Still Working the Problem"
It's difficult to give a single number because it depends heavily on the speaker's physical size and design.Small, highly sensitive speakers (e.g., bookshelf speakers): These might struggle to go much below 60-80Hz without a significant drop-off in output or increased distortion.
Larger, highly sensitive speakers (e.g., floorstanding speakers, horn-loaded designs): These can extend lower, perhaps down to 40-50Hz, and in some cases even lower. True horn-loaded speakers, known for their extreme efficiency, can achieve impressive bass extension, but they tend to be very large.
Edits: 05/26/25
Your JBL speakers have a free air resonance of 40Hz and are 3db down at 45Hz. 10db down at 35Hz.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
That system is -10db at 35Hz. You can call that "usable if you want but that is not normally how we talk about speakers. The -3db point is 45Hz.
By the way, you said "On the other hand, my JBL dual 15" can go down 30Hz"
Again, you can say that your speakers "go down to 30Hz" if you like but that is not normally how we talk about speakers. We normally talk about the -3db point. Not the point that is further down than 10db.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
This is the specs from ProAc. Could you please tell me how many dB at 20Hz?
Description: Two-way dynamic loudspeaker with 1" dome tweeter and two 6.5" polypropylene-cone midrange/woofers. Frequency range: 20Hz-25kHz (no limits given). Nominal impedance: 8 ohms. Sensitivity: 88dB/W/m.
JBL is an American brand. I don't think they lie.
They show the speaker is 10db down at 35Hz
You can get 35Hz from that speaker but you would need a lot of EQ and a lot of watts. The speaker is far, far from flat to 35Hz.
JBL shows the speaker is 3db down at 45Hz so it might be flat down to 60Hz, (educated guess but I would bet I'm not far off)
I can't find the TS parameters for the woofers in the ProAc so I don't know for sure but a 6.5" woofer won't play low bass flat (vs. the midrange)
The ProAc 2.5 falls fast at 70Hz.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
With a drawback, had some rather rare 4315 speakers and they confounded for a brief spate till listened and realized when driven by Good SS amps they sounded like a totally different speaker than using ANY tube amps (12 or 13) I owned. The impedance curve must have looked like the Andes mountains.
The Mind has No Firewall~ U.S. Army War College.
Can you explain how a typical room would attenuate the low frequency pressure waves from a speaker at the listening position? It's not clear to me that this is even a valid concept. That aside, my point is not whether you think it's appropriate for an amplifier to perform well in the lowest octave, but rather whether it has that capability.
You do this using multiple subs. If your main speakers are good into the 20s then you only need two to do the job.
They must be asymmetrically placed. In most rooms they must not reproduce anything above about 80Hz else they can draw attention to themselves.
Standing waves can cancel bass or reinforce it. If its being cancelled, no amount of room correction or bass traps can fix it since amplifier power is being cancelled in the standing wave.
At 80Hz the waveform is about 14 feet long. The ear needs the entire waveform to pass it so know the note is there; a few more iterations to know the frequency and nature of the note. By that time anything below 80Hz has bounced all over the room probably several times. Deep bass is thus 100% reverberant. So a mono bass signal for the subs works fine and you don't have to time-align anything.
At that point you can get smaller rooms, even ones that are square to play bass just fine.
In Texas, you have huge rooms so bass is not an issue. But here in NYC, we have medium size rooms which can accommodate about 30Hz. However we stay outside during spring/summer time and enjoy sun light.f = c / 2d
For example, if your room is 6 meters (about 19.7 feet) long, the lowest frequency axial mode related to its length would be:
f= 343 / 2*6 = 28.58Hz
Edits: 05/26/25
"But here in NYC, we have medium size rooms which can accommodate about 30Hz."
Sorry, no. The smaller the space, the better it supports the pressure waves. What you are stating is an urban myth that is entirely contradicted by the laws of physics. Having taken low frequency SPL readings in motor vehicles and compared them to the same speakers in larger rooms, I can tell you that empirical data also proves this assertion to be false.
!
The Mind has No Firewall~ U.S. Army War College.
By that logic, bass would be impossible in cars. Not to mention headphones ... :^)
It's hopeless, Paul. I studied speaker drivers and acoustics in great detail more than 40 years ago. Nowadays, too many people rely on the Internet knowledge base and simply don't know what they don't know. Newcomers will argue over nonsensical concepts till they turn purple, never bothering even to crack a book written by knowledgable experts. It's the way of the world, and one of the reasons there's so much junk on the market.
I'm in the middle of building a couple monoblocks at the moment, so I'll sign off for now. Take care and thanks again for sharing your considerable expertise through the years.
I have no interest in car audio. I have good headphones and may one day get a good tube headphone amp.
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